BerPolarforsch1996197
Ber. Polarforsch. 197 (1996)
ISSN 0176 5027
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ARK XI12
TROMS0
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BREMERHAVEN
22.09.1 995
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29.1 0.1 995
Chief Scientist: Gunther Krause
Contents:
1. Introduction
1.1
Scientific background
Strategie considerations and narrative of the cruise
1.2
1.3
Weather conditions
2.
2.1
2.2
Meteorology
Turbulente measurements
Remote sensing of sea ice
3.
3.1
3.2
Physical Oceanography
Stratification and circulation in the Greenland Sea
Transport of mass, heat and freshwater
4.
4.1
4.2
Chemistry
Investigation of nutrients
Naturally produced volatile halogenated compounds
5.
Zooplankton
6.
6.1
6.2
6.3
6.4
Multidisciplinary sea ice investigations
Formation of sea ice
Effect of freezing rate on organism incorporation
Microcosm Sea ice formation experiment
Autumn/winter conditions within Arctic sea ice floes
7.
Bathymetric mapping in the Fram Strait
8. Joint Research Program at Kiel University
8.1
Pelagic production regimes
8.2
Bentho-pelagic coupling
8.3
List of benthos stations
9.
Station list
10.
Participants
11.
Ship's Crew
12.
Participating Institutions
13.
Moorings serviced during cruise ARK XI/2
Page:
CRUISEREPORT ARK XI12
Tromsa - Bremerhaven
22.9. - 29.10. 1995
' A u t u m n in the Greenland Sea"
Chief Scientist: Gunther Krause
1.1
Scientific Background
With the theme "Autumn in the Greenland Sea" the expedition had set out to
improve our knowledge of meteorological, physical, chemical and biological processes during the season of rapidly decreasing solar radiation and onset of the cooling phase. Previous field observations during this generally uncomfortable time
of the year are fragmentary, and it was intended to close some of the gaps in the
annual cycles of processes in the physical and biological arctic environment.
In the polar atmosphere, autumn provides the first strong outbreaks of cold air
from Greenland onto a structured sea surface consisting of stretches of Open water
and new ice. There is little Information on the near-ground turbulence of the atmospheric boundary layer which determines the exchange of momentum, heat
and water vapour under such conditions.
The principal goal of Physical Oceanography was to study the water mass stratification just before and possibly during the onset of convection. The measurements of
temperature and salinity were supplemented by nutrient sampling for multiparameter water mass analyses. These investigations continue observations on a long
section from 13OW to 1 7 O E with a station spacing of 10 nm at 75ON, occupied 1989
for the first time during the international Greenland Sea project.
Besides nutrient analyses the investigations of Marine Chemistry concentrated on
lipids, the energy reserves of copepods for surviving the Polar Night. In a second
project naturally produced volatile halogenated organic trace compounds (e.g.
chloroform, trichloroethylene and related substances) were studied.
The largest project focused on the role that autumn plays in the vertical flux of particles which originate in the ice-associated and pelagic production and their fate in
the sediment.
In addition to the above projects, which were specifically designed to profit from
autumn conditions, a bathymetric survey of a region in Fram Strait was planned,
and numerous current meter moorings were to be recovered and partly to be deployed. That task has fallen to this expedition because only the occasional research
ship makes it this far to the north and is able to complete the work due to the iceCover.
1.2
Strategie considerations and narrative of the cruise
The onbreak of winter from the Northwest and the rapidly decreasing duration of
daylight determined route and schedule of this autumn expedition in the first
place. Daylight is followed by the Polar Night at 80° on the 22nd of October. Even
at 75ON the times between sunrise and sunset decrease from 12 to 6 hours during
the time of the expedition.
Daylight was a necessary preposition for many of the planned investigations. This
included all work on the ice, the flight operations with the HELIPOD which carries
delicate turbulence Sensors through the air 15 m below a helicopter, the flights
with laser altimeter and line-scanner, and the recovery of moorings. In the ice
some of the shipbased work which is normally done round the clock relies on daylight as well, e.g. the towing of bottom gear like Agassiz trawl and the epibenthos
sledge. Naturally, there has been much pressure On the precious hours of daylight.
Fortunately, the large working group of Kiel University had planned for extensive
station work up to 20 hours at few locations. These stations were called the "SFB
stations", and they formed the backbone of the daily work during much of the first
phase of the expedition. During the daylight time the flight operations and work
on the ice could be done in parallel, and it has been possible to interrupt some of
these stations to recover moorings.
Compromising on the demand to head North as fast as possible, to ensure daylight
for respective work, and to minimize steaming, the following work sequence was
adopted (Fig.1.I):
Complete half of the bathymetric survey
Try to recover moorings at 79ON while occupying SFB stations
perpendicular to the slope of the Greenland Shelf from East to West
In the ice, perform ice investigations parallel to ship operations, fly
HELIPOD, laser altimeter, line-scanner and employ bow mast for
turbulence measurements
Work on stations in the Northeast Water Polynya (NEW) and supply fuel
to Eskimonaes summer camp
Perform SFB station work along the 2000 m isobath
Complete second half of bathymetric survey
Revisit mooring sites at 79ON to provide a second chance to recover
moorings in the pack ice
Steam to 75ON and recover 7 moorings in the area
Intensive turbulence measuring campaign, complete ice investigations,
SFB station and trawling with Agassiz net
Work the long CTD transect at 75ON including several plankton net
stations, deploy 1 and recover 2 moorings on depths of 3200 m
PFS "Polarstern"
Reise ARKXIl2
Tromse - Bremerhaven
22.09.-29.10.95
Fig. 1.1: Cruise track of the expedition
'Polarstern" left Tromsà in the morning of the 22nd of September. Due to a strong
and favourable SW wind the bathymetric survey began only 1.5 days later at 79ON.
On September 26, we found the first mooring at 790N under such thick a n d compressed pack ice that one could not even think of recovering the instruments, even
though free water was tantalizingly close to the east. The Same Situation was found
12 days later, when the area was revisited. Out of five instrument moorings at
7g0N, three were brought on deck. Otherwise the recovery of all the other moored
instrument strings on the list has been a great success so late in the season.
Due to an almost 100% coverage by very thick and very large old ice floes in the
area of the NEW Polynya the summer camp at Eskimonaes could not be supplied.
Only little station work in the vicinity of the planned positions was possible.
1.3
Weather Conditions
At the southeast side of a large low the wind increased to Bft 8, in gusts 9, when we
were leaving the Norwegian fjords. The characteristic height of the waves reached
about 3 m. Close to the center of the low the wind speed decreased on the following
day to Bft 5, while the first Snow showers appeared and the temperature dropped
to O0C.
During the night between 24th and 25th of September the ship arrived at its working area West of Spitsbergen. On the northeast flank of a low that was located West
of Spitsbergen the wind shifted to easterly direction with force Bft 5. Over the night
the wind velocity rose up to Bft 7 shortly.
On September 26, the wind shifted via north to northwest, while a new low coming
from Spitsbergen moved slowly westward. As a result of cold air advection from
the northeast Greenland area the temperature dropped below O° for the first time
during this journey. The thermometer showed -8OC at noontime. Temporary Snow
flurries occurred. The lows were controlled by high rising cold air turbulence.
Starting in the northern Greenland Sea the center of this turbulent region moved
slowly southward towards the waters of Jan Mayen. Thereby the Fram Strait was
influenced by an upper-level-airflow. This and the bottom low were moving
southwestward and weakening.
On September 27, the wind shifted shortly to southwest and decreased to a force of
Bft 3, when we were in the operation area at 78ON, 5OW. The stratiform clouds
broke u p simultaneously. On 28th of September a new low moved westward via
Bear Island while its pressure dropped below 980 hPa. Heavy warm air advection at
the front of this low caused a quick change in weather with snowfall and temperatures increasing close to O°CThe wind shifted to north and increased to Bft 6. Since
the controlling power of the upper level vortex over the Northern Polar Sea
was still not diminished this low moved slowly southward while weakening to
1000 hPa in its center.
Towards the end of the month a temporary pressure increase caused the formation
of a high over 1015 hPa that was slowly spreading in the direction of the Fram
Strait. The wind velocities within the working area decreased to Bft 2 -3. However,
simultaneously sinking air strengthened a near bottom Inversion, which in turn
caused deep Stratus clouds with fogbanks. The helicopter work was hindered by
this weather situation.
On the 2nd of October, a weak convergence was forming within the older polar air,
which was partly damp while it was reaching high. The convergence was swinging
around the filling low southwest of Spitsbergen. Thereby the operation area of
"Polarstern" was influenced by snowfall and low visibilities. The wind shifted to
northeast and had a strength of Bft 3. During the night between 2nd and 3rd October the sky was clearing up. As a consequence a thin cold air layer was forming at
light winds because of a negative balance of radiation. In the morning the fog point
was reached. The shallow fog persisted over the day while temperatures were
around -9OC. The ship was covered with strong hoarfrost.
On October 4, the high over Greenland continued to increase and the area where
"Polarstern" was working was influenced by sinking processes. This resulted in a
very stable stratification with Stratus clouds resting almost on it and 'white out'
conditions occurred.
By the 6th of October the center of high bottom pressure moved from the northeast
of Greenland to Spitsbergen. Therefore the wind shifted quickly to northeast.
Simultaneously a weak lee low developed north West of the mountains of
Spitsbergen because of a southeasterly airflow. In the vicinity of the center of this
low wind velocities of Bft 3 to 5 occurred only. There were partly also Snow showers and temperatures of about O°CHowever, the southeasterly swell increased.
On the 8th of October the ship reached the ice edge again at about 79' N while visual flight conditions were prevailing. The southeasterly winds of Bft 3 to 4 were
continuing, and the sun was shining for the first time since days.
When the operation area at 75ON and l l O Wwas reached the weather conditions
were worsening at the edge of a northatlantic low pressure complex. This resulted
in winds with Bft 6 to 7, and in the evening of the 9th October of Bft 8. The visibility decreased simultaneously accompanied by partly rain showers developing into
Snow. Meanwhile one low split from the complex and moved to the Northern
Norwegian Sea. At the Same time a high over Greenland developed. Increasingly
cold air reached "Polarstern" from the nearby ice edge together with backening
winds coming from the northwest. Within a few hours the temperature dropped
by 8 K to -6OC. The gustiness of the wind increased over relatively warm water
(+2OC). The ship's weather station reported winds of northwest Bft 8 with gusts up
to Bft 10 on the 10th of October. However, the characteristic wave height did not
reach beyond 3 m, since the fetch from the nearby ice edge to the ship was relatively small. On the following day the wind decreased very slowly only because
another weaker low moved quickly from Iceland to the North Cape. No air traffic
was possible in light Snow flurries with low visibilities.
On the following two days the area of operation was influenced by an eastward
spreading Greenland high. Light winds from northwest to southwest were
blowing, there were little clouds, and at temperatures of - 1 3 T there were good visibilities in dry air. The area at the ice edge at about 75OW 9OW was influenced
by favourable weather, because the high over Greenland was increasing over
1025 hPa.
On the 14th October the wind came from northwest with Bft 4, the sky was without
clouds and the visibility was very good. Towards the middle of the month the area
of investigation was influenced shortly by a storm low that was moving slowly to
the northeast. The wind which was shifting right to the northeast reached only Bft
6 on the 16th of October, since the low was slowly decreasing. There were heavy
Snow showers in a labile layered cold air mass at the backside of the low at -2OC to
-4OC air temperature. Because of the relatively small fetch characteristic wave
heights of 1 to 2 m were reached. On the following day the wind blew consistently
from one direction, but the speed decreased to 4 to 5 Bft.
On October 18 the wind shifted to the right to southeasterly direction because of a
low development in the Fram Strait. The wind blew with Bft 7 with Snow showers.
A new storm low which developed on the 17th of October in lee of Greenland near
Cape Farvel moved under decreasing via Iceland towards the Northern
Norwegian Sea. It reached a low pressure of 980 hPa at the 19th of October.
"Polarstern" stayed at first at the outer edge on the north side of this cyclone.
On the 20th of October the wind was backing to the northwest and increased within
a few hours to Bft 8. This was due to our location at the backside of this storm low.
The temperature dropped from -4OC to -8OC simultaneously because of cold air advection. This led to a turbulente development over the 5OC warm sea water. The
wave height increased rapidly. During the night of 21st/22nd of October a marked
cold air front passed "Polarstern". It caused a sudden shift in the wind direction
from West to eastnortheast and an increase in the wind velocity from Bft 3 to Bft 9.
There was no work possible at the station due to Snow flurries and crossing seas up
to 5 m in height. But the the weather calmed down quickly.
On the way home several cyclones influenced the track of the ship. They developed into storm lows partly below 970 hPa in the vicinity of Iceland. Strong
southerly winds prevailed south of 70°N
Bordwetterwarte FS Polarstern ARK XI12
Tromsoe - Bremerhaven 22.9, - 29 10.95
Bordwetterwarte FS Polarstern ARK XI12
Tromsoe - Bremerhaven 22.9. - 29 10.95
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Windstiirke in Beaufort
Fig. 1.2: Frequency distributions of wind direction and wind speed
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-Lufttempetatut
Tauputii~tstempetati~
Fig. 1.3: Air temperature, dew point temperature and wind velocity
2.1
Turbulence measurements
(C. Wamser, W. Cohrs, C. Wode, M. Hofmann, M. Schürmann
Current efforts in numerical climate predictions require that the knowledge of global near-surface turbulent energy fluxes be improved by about one order of magnitude. Since the earth's polar regions have great influence on the oceanic deep-sea
water circulation, the atmosphere-ocean heat and momentum exchange is also of
special interest. Due to the inaccessibility of these regions, most of the relevant parameters, needed for model calculations, are poorly investigated.
In order to help filling this gap, two quite different but complementary meteorological turbulence measuring systems were operated together for the first time: the
helicopter-borne sensor system HELIPOD, and the newly constructed shipborne
turbulence measuring system TMS. Both systems aim at high-resolution in-situ
measurements of near-surface turbulent fluxes of mass, momentum, sensible and
latent heat. The turbulence measurements were supplemented by a helicopterborne colour line-scan camera, which provided digital Images of the ice Cover in
order to record the different ice situations during the flux measurements.
The TMS consists of a 17 m mast, installed on the ship's bow crane. This mast
usually is fixed horizontally during the cruise, but for operation it can be moved
forward and turned into a vertical position by a hydraulic and a tackle system. At
five heights between 3 and 20 m above the sea surface, five USAT sonic sensors
(METEK) are mounted to measure the turbulent fluctuations of wind and temperature. Five Pt-100 temperature sensors determine the mean temperature profile.
Additionally, a Lyman-alpha hygrometer is installed at a height of 3 m to measure
the turbulent humidity signals. An acceleration sensor determines disturbing frequencies of mast oscillations or even of slow ship movements.
HELIPOD is an autonomous meteorological turbulence measurement system,
about 5 m long and 240 kg in weight, which is constructed for operation on a 15 m
rope below almost any helicopter. The system is the first worldwide, and the only
one which combines the aerodynamical and logistical advantages of a helicopter as
towing aircraft with high-tech meteorological, navigational and technical sensor
equipment. HELIPOD possesses an internal power supply, an active rudder stabilization, a DGPS-based and an inertial navigation system, and an extensive sensor
equipment including real-time data processing and recording. It carries the following meteorological sensors: A 5-hole probe for static pressure and wind measurements, 2 temperature sensors with different response times, an independent
humidity measuring channel containing a humicap (i.e. a capacitive humidity
sensor), a dewpoint mirror and a Lyman-alpha sensor, and a radiation thermometer for surface temperature measurements.
The navigation system equally comprises sensors with different response times
and long-term stabilities: a static and a radar altimeter, an inertial navigation sy-
stem and two different GPS Systems providing the determination of both position
and altitude.
As HELIPOD contains some quasi-redundant sensors each with different time behaviour, even long-term data can be obtained within a wide frequency range
through complementary filtering of corresponding signals. For additional improvement, the digitizing error of the fast sensors is reduced by storing 10-value averages calculated on-line from a 1000-Hz oversampling.
Meteorological and navigational raw data, technical system Parameters and on-line
calculated secondary quantities are recorded in up to 160 channels. Sampling frequencies reach from 1 Hz (GPS navigation) u p to 100 Hz (turbulent fluctuations of
meteorological quantities). Data preprocessing is done simultaneously by different
transputers, while the final data storing is real-time controlled by the VC6 main
computer. For data storing, magneto-optical discs are used with a recording capacity
of 300 MB each side, corresponding to about 3 hours or 450 km flight path length. A
special software package allows an on-line display of arbitrary data channels on a
laptop computer inside the helicopter and an in-flight calibration of different sensors.
The objectives for the HELIPOD operations during ARK XI/2 were:
system tests and calibration flights,
measurements of the near-ice edge atmospheric boundary layer
structure,
airborne near-surface measurements within a stably stratified boundary
layer over different types of surfaces and comparison of the results with
those, gathered simultaneously by the shipborne TMS,
investigations of the dependence of some statistical meteorological
properties from different types of flight patterns,
comparisons of HELIPOD vertical profiles with data from GPS-wind finding
radiosondes.
In total, during the ARK XI/2 cruise 10 different HELIPOD measurements were
performed. The locations of the flights are marked in Figure 2.1.
The main objectives of the TMS measurements were the analysis of the turbulent
fluxes in the marginal ice Zone and a general in-situ system test. During the whole
cruise, the TMS was operated at 8 stations each of 2 to 3 hours duration. At these
stations the ship was either at a fixed position in the ice or moved very slowly
against the wind. During the measurements, very different structures of ice Cover
could be investigated with regard to their influences On the heat, moisture and
momentum exchange between the ocean and the atmosphere. All the elements of
the TMS including mast, hydraulic and tackle Parts, sensors and the data acquisition system were tested under various meteorological situations.
Figure 2.1:
Locations of HELIPOD flight areas during ARK XI/2. The inserted
symbols denote in particular:
test measurements and calibration flights,
cross:
measurements of the near-ice edge boundary layer structure,
triangle:
HELIPOD, TMS and radiosonde comparisons,
diamond:
test of statistical flight pattern properties.
Square:
It turned out that different modes of operation of the ship's propulsion System
(main engine, bow and Stern thrusters) cause different vibrations of the ship,
which also are conducted to the mast and the Sensors via the bow crane. High resolution acceleration measurements provided the spectral distribution of all the various vibrations which possibly may influence the turbulence signals. By means of
spectral analysis of the acceleration measurements, two dominant frequencies were
detected. These vibrations were mainly caused by the rotation of the main shafts
and the thrusters, and they are at 3 and 14 Hz, respectively. The amplitudes of the
corresponding acceleration have turned out to be typically about 0.05 g.
The evaluation of the collected HELIPOD and TMS data comprise plausibility
checks, elimination of outliers and trends, correction for potential data losses and
resulting spectral gaps, cutting of longer time series into sections, spectral analysis
of the resulting time series, and finally the calculation of some statistical properties
which provide information about the investigated turbulent exchange processes.
For this purpose also the weather analyses of the "Polarstern" weather-station are
used, as well as some further radiosounding data, satellite images and ice charts.
First steps of data evaluation of both HELIPOD and TMS data were started directly
after the measurements on board "Polarstern". Since a total amount of about 2500
MBytes of binary HELIPOD raw data and about 700 MBytes of TMS data were
-25
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Distonce [km]
Figure 2.2:
Isotherms of the potential temperature in a vertical plane perpendicular to the marginal
ice Zone. The abscissa origin indicates the transition betwcen the ice edge and Open water.
Positive distances denote Open water, negative ones denote ice cover.
(HELIPOD flieht 8,75.0Â N / 12.8' W, 12'0ctober 1995,10:50- 12:30 UTC)
collected during this cruise, the final evaluation of these data will take some time.
However, some preliminary results are already presented in the following.
In Figure 2.2 isotherms of the potential temperature in a vertical plane perpendicular to the marginal ice zone over the ice edge are presented. The basic data were
measured by the HELIPOD On October 12, 1995 at about noontime (Figure 2.1, triangle at 75'N). The ice edge was in NNE-SSW direction, and during the measurement the surface wind came from 340°i.e. blowing nearly in off-ice direction.
The wind speed at 10 m height was only about 5 knots, resulting in a very widely
spread marginal ice zone. Stable stratification developed above the ice and unstable
stratification above the Open water. Figure 2.2 shows that under weak wind
conditions significant horizontal temperature differences develop over the transition Zone between sea ice and Open water.
An example of the TMS measurements is presented in Figure 2.3 a,b. During the
station on 4 October 1995 "Polarstern" sailed with an approximate speed of about
0.5 knots through a newly frozen lead towards a huge, snow-covered, thick old ice
flow. The mean thickness of the new ice was about 5 Cm, the water temperature
was -1.2' C. The wind came from starboard ahead and so the fetch over the thin
new ice reduced from 1700 m at the beginning to about 300 m at the end of the
measurements. Figure 3a shows the development of the sensible heat flux hs at
three levels. From most of the data, a decrease of hs with height and with the
approach to the ice edge is obvious. The deviation from the expected development
of hs at the two lower levels at 1000 m is obviously caused by a right-hand turning
of the wind during that period, which leads to a decrease of the fetch. The
corresponding temperatures, measured at five heights, are presented in Figure 3b.
The continuous decrease is consistent with the decrease of the sensible heat fluxes
during "Polarstern's" approach to the huge flow.
Figure 2.4 shows a comparison of the standard deviation sigw of the vertical wind
component and the friction velocity ustar in the height range from 3 to 50 m,
measured simultaneously with the TMS (black bars) and the HELIPOD (white bars).
The corresponding measurements were performed above a newly frozen homogeneous lead of a width of about 10 km in the wind direction. The ice thickness was
about 20 cm (Figure 2.1, diamond at 75ON). The ship's position was fixed, and the
HELIPOD flight Pattern consisted of 5 horizontal legs, each about six miles long,
orientated parallel to the wind and situated very close to the ship. The heights of
the legs were about 8, 15, 25, 33 and 52 m. The wind velocity during the measurement in the covered height range was about 6 to 10 knots. The measured statistical
wind and turbulent quantities between these two Systems agree surprisingly well.
distance t o huge ice floe (m)
Figure 2.3a,b:
Sensible heat flux (3a) and temperature data (3b) vs. distance to a huge homogeneous
ice flow. The data show the effect of a lead, covered with thin new ice, on the lower
boundary layer.
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height (m)
30
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50
Figure 2.4a,b: Comparison of the standard deviation sigw of the vertical wind component W (4a) and
the friction velocity ustar (4b) in the height range 3 to 50 m, measured simultaneously
with the TMS (black bars) and the HELIPOD (white bars). (HELIPOD flight 10,
75.0' N / 13.5' W, 13 October 1995,14:10 - 16:20UTC)
During the measuring period corresponding to Figure 2.4, some GPS radiosondes
were launched, each measuring vertical profiles of wind, temperature and relative
humidity. Figure 2.5 gives an example of a temperature profile from the surface up
to 700 m. Data from the radiosounding and from the HELIPOD's parallel ascent
agree even better than the HELIPOD's upward and its immediately following
downward soundings.
700
600
E
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500
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(U
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ternperature ('C)
Figure 2.5:
2.2
Example of a temperature profile from the surface u p to 700 m, measured simultaneously by HELIPOD and a GPS radiosonde. (HELIPOD flight 10,75.0ÂN / 13.5O W, 13
October 1995, approx. 16:lO UTC)
Remote Sensing of Sea Ice
(T. Martin, L. Kaleschke)
The horizontal extent of the sea ice in the Arctic Ocean and the bordering seas
changes seasonally from up to 12-13 106km2during winter time to approximately
half that during the summer. The sea ice exported out of the Arctic Ocean via the
East Greenland Current represents a prominent Part of the fresh-water budget of
the Greenland Sea and the North Atlantic. The stability of the circulation depends
strongly On the surface fresh-water and salt fluxes. The surface fresh-water budget
of the North Atlantic, and therefore the sea ice export out of the Arctic Basin, plays
a critical role in the climate System.
To obtain an estimate of the sea ice mass flux, the sea ice distribution and the sea
ice drift must be known as well as the ice thickness.
The aim of the Programme was the observation of sea ice Parameters which are relevant for the sea ice mass flux in the East Greenland Current. This includes the
reception of satellite images and measurement of the sea ice surface structure. The
combined processing along with data Sets of sea ice thickness, sea ice concentration,
sea ice extension and sea ice drift velocity should give an improved knowledge of
the sea ice mass fluxes in this area.
AVHRR satellite images:
During the expedition, images of the Advanced Very High Resolution Radiometer
(AVHRR) flown on the satellites of the National Oceanic and Atmospheric
Administration (NOAA) have been received on board "Polarstern". The AVHRR
is sensitive in the visible and thermal infra-red spectral range. The horizontal resolution in the nadir view is 1.1 km. All images are processed using routines for calibration and rectification on to a stereographic grid. These images were used to derive the sea ice distribution, and for planning the flight activities of the laser-altimeter (see below) as well as for ship navigation.
Sequences of cloud-free images allow the determination of the sea ice motion.
Special image processing algorithms track common features in pairs of images. The
investigations of the last years show a minimum of the sea ice drift velocity in
summertime of 15cm/s. During autumn, the drift velocity increases and reaches a
maximum during winter with approximately 30 cm/s.
Figure 2.6 - 2.9 give an overview of the sea ice conditions and their development
during the expedition. Figures 2.6 and 2.8 show the difference between channel 1
(0.58 pm - 0.68 pm) and channel 2 (0.725 pm - 1.1 [im ) which are both located in
the visible spectral range. The signals in both channels are strongly influenced by
the extensive coverage of semi-transparent clouds. Differencing these channels reduces this effect and results in information about the sea ice. Due to the reduction
of sunlight during the field phase, only channel 4 (10.3 [im - 11.3 pm) and channel
5 (11.5 pm - 12.5 pm), which are located in the spectral range of the thermal infrared, gave reliable results at the end of the experiment (see Figure 2.7 and Figure
2.9).
Figure 2.6 documents the sea ice conditions at the beginning of the work in the ice.
The image shows a clearly pronounced ice edge due to the easterly wind direction
of the first days. The ice coverage was an assemblage of larger multiyear ice floes
age shown as light areas in the image. Smaller ice floes with different ages combined with areas of a larger portion of new and young ice are Seen as darker regions.
During the following four weeks, the ice concentration increased and larger ice
floes dominated this region. The ice edge also moves to the east (see Figure 2.7). A
similar situation could be found in the southern area of interest at 75ON. At the beginning of our work in this region, the ice conditions were dominated by multiyear ice floes with smaller sizes. The satellite image shows no further structure
because of the restricted resolution of the Sensor (see Figure 2.8). Strong advection
from the northern Part of the East Greenland Current and decreasing temperatures
very quickly formed a more extensive ice coverage. Our work was mainly located
in the area of the ice edge, which was primarily covered by pancake ice of different
sizes ( Figure 2.9).
Figure 2.7:
NOAA-12 AVHRR satellite image of October 24,1995 08:12 GMT channel5
and the ship's track from September 24 to October 8
Figure 2.8:
NOAA-14 AVHRR satellite image of October Ist, 1995 12:14 GMT channel 1 - channel2
and the ship's track from October 9 to October 19
The laser-altimeter:
Laser profiling is a remote sensing technique in which the terrain surface elevation
along a straight line path is monitored. In sea ice remote sensing, laser profiler data
are used to investigate the roughness of the ice surface, in particular, height and
spatial distributions of pressure and shear ridges. Profiler data can also be utilized
to estimate the thickness of ridged ice. Given the roughness statistics, it is also possible to determine the contribution of form drag on ridges to the momentum
transfer from the atmosphere to the pack ice.
The laser profiler used during this experiment was an Ibeo PS 100 EL mounted on a
helicopter. The laser diode generates pulses with a wavelength of 905 nm. The ice
surface elevation profiles were collected at a sampling rate of 2000 Hz and a vertical
resolution of 2 Cm. A flight speed of 80 kn yields a horizontal resolution of 2 cm.
During the expedition, we have had 12 flight missions with a total profile length of
1150 km. The table below gives the date and the location of every mission. The
laser altimeter measures the distance between the helicopter and the ice surface
(Figure 2.10 top). Thus the raw laser profiles express the variation in flight altitude
and surface undulation. A criterion for the classification of the signal from the
ground is the echo amplitude. Open water and very thin new ice are not detectable
with this Instrument. Light Nilas or snow-covered new ice results in lower echo
amplitudes than thicker ice. A special filtering method separated the different
signal components (See Figure 2.10 bottom). The Zero is set to the mean flat surface
of the floe. The deflection of the signal is now equivalent to the height of the ridges
on the floe. At 400 m a layer of thin ice is detected. This point represents the border
line between two larger multiyear ice floes. We hope that this kind of data will
allow us to obtain more knowledge of the freeboard of ice floes in the East Greenland Current.
Table of the flight missions:
Flight
Date
Start Position
Comment
No.
1
2
3
4
5
6
7
8
9
10
11
12
26.09.95
27.09.95
28.09.95
29.09.95
02.10.95
04.10.95
05.10.95
08.10.95
12.10.95
12.10.95
13.10.95
14.10.95
78 59.90 N 03 42.87 W
78 56.00 N 05 06.00 W
78 59.00 N 03 59.00 W
79 02.37 N 07 17.36 W
80 32.56 N 05 42.69 W
80 03.04 N 04 18.42W
79 33.22 N 03 54.73 W
79 02.00 N 02 02.60 W
05 00.00 N 13 00.00 W
75 00.00 N 13 00.00 W
74 59.86 N 14 01.04 W
75 00.00 N 12 50.00 W
small ice floes in the area of the ice edge
Video flight in the Same area
Video flight in the Same area
Line-scan flight in the Same area
All flight missions took place over ice conditions which are typical for the early autumn. The 8 missions at 79ON describe a homogeneous situation of wide-spread
areas of multiyear ice floes of different sizes. The ice floes were covered with refrozen melt ponds and a thin Snow layer. Between these floes, different types of nekv
ice were still forming. Due to the dynamics in this region, the most dominant
phases of ice development were pancake ice of different sizes and slush ice. Most of
the pressure ridges covering multiyear ice floes were old and hummocky. Due to
the increasing ice velocity during autumn, some ridging could be observed at the
floe edges.
The sea ice thickness:
During the last years, AWI has deployed several oceanographic moorings at 75ON
in the ice covered Part of the Hast Greenland Current. Most moorings were
equipped with an Upward Looking Sonar mounted in a depth of 50 m. The ULS's
operate like inverted echo sounders and measure the ice draught during one
whole year. Five of these Instruments were recovered during these field experiments. For further Information See section 3.2.
Figure 2.10:
Time series of the laser-altimeter flight mission of 27.09.95. The time series Cover a
period of T=50s, which is equivalent of a measuring distance of D = 2300 m. Fach data
point represents a mean of 100 measurements. Top: Original distance measurements
between the helicopter and the sea ice surface. Bottom: The retrieved surface structure
of the ice floe.
3.1
Stratification and circulation in the Greenland Sea
(G. Budeus, B. Cisewski, R. Plugge, S. Ronski, S. Ufermann, H. Wehde)
Aims
The physical oceanography Programme continued the work performed during the
Greenland Sea Project and provided pre-information for ESOP-2, starting in 1996.
Thus it has been an important link between the two projects, avoiding an observational gap between them. The measurements aimed at the understanding of the
convective urocesses in the central Greenland Sea and their deuendence o n the
climatological Status of the Nordic Seas/Arctic Ocean System.
Since the beginning of the Greenland Sea Project in 1988, winter convection has
only penetrated to mid-depths of the Greenland Sea. No bottom water renewal
could be observed up to now. It is now generally believed that such a renewal does
not occur continuously but rather bears the character of a distinct event taking
place every 10 to 20 years. Therefore long term efforts are demanded in order to
answer the questions whether convective activity in the Greenland Sea has ceased
in the last decade or whether it undergoes a normal cycle of necessary preconditions. It is not possible yet to state which preconditions are necessitated to initiate
deep convection and bottom water renewal.
Consequently, considerable efforts are undertaken by AWI to repeat a standard
transect across the Greenland Sea once per year and to complement these investigations by mooring-based measurements.
Methods
A prototype self-profiling deep sea instrument for mooring purposes to be employed within the frame of ESOP-2 has been tested during the cruise. Seven test
casts have been performed and will be evaluated later.
The methods of the ship-borne oceanographic work are modern standard and are
listed below.
CTD, Water sample rosette
The CTD-system used is a Seabird 911+, equipped with dual temperature and conductivity sensors, and a number of additional optical sensors including chlorophyll
and yellow substance fluorescence. The dual sensors allow for an immediate Cross
check of calibration consistency and Sensor drift. The water sample rosette was a
Seabird Carousel that underwent its first expedition. Its peformance was faultless
during an uninterrupted use of about four months. Bottles were 12 1 Niskin with
coated steel springs. They proved not to contaminate samples taken for tracer
measurements (by K. Abrahamson and A. Ekdahl, Chalmers University Gateborg).
Pot. Temperature
0
100
/
OC
200
300
400
Distance
Fig. 3.1:
500
/
600
km
Preliminary data of potential temperature across the Greenland Sea at 7 5 O N.
Final calibration may lead to minor changes.
700
800
Some salinity checks were performed at sea. We prefer however to do the major
part of the in-situ conductivity calibration under laboratory conditions later.
Reversing thermometers were used to control the stability of the CTD temperature
Sensors. Spacing of the hydrographical stations was generally 10 nautical miles, but
was enhanced at certain locations according to prior experience with the hydrographic structure of the Greenland Sea.
Our naming convention for the hydrographic stations is as follows: There is a four
character prefix ('arll'), followed by a three digit station number ('xxx', coinciding
with the ship's station numbers, except after station 096) and a Cast number ('Y')
starting with 0 for the first Cast of a station. So 'arll0991' would denominate the second Cast on station 099. First casts are usually to the bottom, later casts usually to
smaller depths.
ADCP
A ship mounted ADCP (RDI, 150 KHz) has been operated in ice-free areas and on
stations in the ice. In most regions a vertical range of slightly less than 400 m has
been achieved. The data will be used for transport estimates of the major currents
in the Greenland Sea. The north-south transect West of Bjnrn~yaallows to determine the Atlantic Water outflow towards the Barents Shelf.
First resul ts
First results must be Seen as qualitative Information only, since the post-cruise calibration of the CTD data could not be applied yet. Therefore no estimates of e.g.
watermass volumes or geostrophic speeds are given here. Based on the high primary quality of the data, some immediate conclusions can nevertheless be presented.
Since the standard transect on 75ON has been performed with a high spatial resolution it allows for a sound estimate of the convective Status of the Greenland Sea
and of the modifications in the absence of deep water renewal. In the upper layer,
no indication of last winter's convection could be observed. This stays in contrast
to preceding years, where remnants of convective events could be traced to depths
of e.g. about 2000 m in 1989 and 800 m in 1993. From the latter date On, Atlantic
Water seems to spread from the boundaries into the Center of the Greenland gyre
in a layer close to the suface and to hinder convective activity. The body of fresher
and colder water between station 44 and 69 in a depth range from 500 to 1000 m
(Fig. 3.1) can be identified as not to stem from last winter's convection. The formation of these waters dates back to at least the winter 1993/94 if not to the preceding
one.
Below this layer a temperature maximum is found that might be related to parts of
the Arctic outflow which shows a prominent signal over the East Greenland slope.
The deeper waters in the Greenland Sea keep changing their properties towards
higher temperatures and salinities, i.e. towards the properties of the Arctic Deep
Water. Potential temperatures below -1.20° are not observed anywhere in the
deep water any more, and the -1.15OC isotherm is found roughly 200 m deeper than
in 1994. Waters with salinities below 34.90 are found only as very small remnants
that endure close to the bottom in the center of the Greenland gyre.
3.2
Transport of mass, heat and freshwater
(C.H. Darnall, R.A. Woodgate)
The East Greenland Current determines the flow of polar water masses from the
Arctic Ocean via the Greenland Sea into the Iceland Sea. This flow gives rise to significant transports of mass, heat and fresh water. The fresh water transport is especially important in Setting the conditions for water mass formation, as it affects
the stability of the water column. Ultimately, it is the export of the newly formed
water masses into neighbouring parts of the North Atlantic which determines the
role of the Greenland Sea in the global circulation.
To assess these transports of mass, heat and fresh water, current meter moorings
have been maintained for several years in the Fram Strait at 79ON and along a
transect across the East Greenland Current at 75ON. A long-term measurement
Programme is required as the transports are subject to sizeable fluctuations. The
seasonal fluctuations are certainly significant, but it is expected that the interannual variations are also important.
These mooring arrays have been recovered and partly redeployed during this
cruise. Of the 9 planned recoveries, 8 moorings (FWA-2 '94, MI-94, AWI410, 411,
412, 413, 414 and GSM-05), have been successfully retrieved, with all Instruments
being recovered without damage. However, one mooring (FWA-1 '94) was under
too much ice for recovery despite several visits to the site, and has been left for recovery by another ship next year. The only two redeployments planned (FWA-1'95,
FWA-2'95, both at 79ON) have also been successfully completed.
The moorings recovered are part of an international programme with participation of Germany (AWI, Kiel IfM and Hamburg IfM), USA (APL/UoW) and
Norway (Norsk Polar Institute). In total, some 7.5 tonnes of equipment have been
recovered, including 23 current meters, 7 SeaCats, 7 ULS (Upward Looking Sonars)
and over 10 km of line.
4.1
Investigation of Nutrients
(C. Albers, B. Hollmann, M. StŸrcken-Rodewald
The concentrations of the dissolved inorganic nutrients, nitrate, nitrite, phosphate
and silicate, were determined during this cruise in high spatial resolution. The distributions of nutrients are closely connected with the biological and physical inves-
tigations. The different water masses with their different nutrient concentrations
influence the development of phytoplankton blooms. During this study the variability of nutrients in the surface water was determined to find out whether there
was a limitation of phytoplankton growth by nitrate or silicate during this late
season of the year.
The change in nutrient concentrations was followed during the Fram Strait transect and the transect across the Greenland shelf, slope and Greenland Sea. In comparison with similar transects the years ago, the seasonal and interannual variability was determined. In view of the water mass determination, especially silicate is
an excellent tracer of the outflow of upper halocline Arctic surface water along the
Greenland slope. This water mass is especially rich in silicate compared to Atlantic
and Arctic waters. On 80° and 75' two transects with a high spatial resolution of
hydrographic and chemical stations were performed across the Greenland slope
and the Greenland Sea to determine the structure of this outflow as well as the nutrient concentrations and distributions in the entire Greenland Sea. Additionally
nutrients were determined on a transect from Bear Island to North N&rway. In cooperation with the ice group and the geologists nutrients were analysed in large
numbers of samples from ice cores and various ice types as well as Pore waters.
Water samples taken with CTD casts were analysed immediately on board for
nitrate, nitrite, phosphate and silicate with a Technicon Autoanalyzer system according to standard methods. Nutrients were determined at nearly all stations from
usually 24 depths distributed between surface and bottom. The sampling schedule
follows standard oceanographic depths, and in addition samples were obtained
from casts for biological investigations.
First interpretations of the results give no clear indication on high silicate values
along the East Greenland slope neither at 80° nor at 75ON. Unfortunately a transect at 77ON was not possible due to heavy ice conditions. In the surface layer nutrients were reduced compared to winter concentrations but never totally exhausted.
In the surface water of the East Greenland shelf and across the slope silicate and
phosphate values were 2 to 3 times higher than in the central Greenland Sea. These
enhanced concentrations are typical for the Polar Water in this region.
4.2
Naturally Produced Volatile Halogenated Organic Compounds
(K. Abrahamson)
Obiective:
The main objective of our investigations is to understand the fate, distribution and
formation of naturally produced volatile halogenated compounds. These compounds are ubiquitous trace constituents of the oceans and the atmosphere. Their
role in the global circulation of halogens and in atmospheric chemical reactions
has been discussed extensively within the last few years in connection with their
ability to affect the atmospheric ozone budget.
Bromine is the halogen found most often in marine-derived compounds, even
though its concentration is much lower than that for chlorine. The presence of organo-chlorine compounds in the marine environment is usually attributed to
human activities, through their use as pesticides, anti-freezing agents etc. However, our recent investigations have shown that both macroalgae and microalgae
produce chlorinated compounds, too.
Our investigations during ARK XI/2 can be divided in three Parts:
-
Formation of halocarbons by pelagic micro-organisms
Estimation of the flux of naturally produced compounds from the sea
surface to the atmosphere
Distribution of halocarbons in the water column
Sam~line:
In accordance to the objectives, sea surface water samples were collected through
the sea surface inlet of the ship along the cruise track. Also, water from the entire
water column was collected from the rosette sampler. In addition water was sampled from the multicorer. Table 4.1 summarizes the work performed during the
first Part of the cruise. Along the two transects, 75ON, and 75ON to 71°N38 out of 58
and 14 out of 24 stations were sampled respectively. Due to the relatively long analysis time, 26 minutes, effort was made to sample every other station, and at least
12 different depths. To avoid contamination of the preconcentration unit with
micro-organisms, all samples were filtered through a GFC filter prior to analysis.
In order to be able to calculate fluxes of the compounds between the air-sea interface, air samples were also analysed.
The formation of naturally produced halocarbons by different-sized micro-organisms, were studied. Surface water was filtered through a filtration unit equipped
with 5 different-sized filters, 1000, 150, 12, 2 and 0.4 Pm. Each fraction contained
250 ml. After the filtration of approximately 25 1 of water, during a period of
4 hours, the water from the different compartments was put in 60 ml glass bottles.
Care was taken to avoid any headspace volume, in order to minimize losses of the
compounds to air. The glass bottles were then put in a refrigerator, with a mean
temperature of 0.5OC, and a light intensity of approximately 70 mol photons m-2 s-I.
The formation of halocarbons was then measured after 6 to 60 hours. Prior to
injection, the water was filtered through a GFC filter, and the chlorophyll content
was measured according to standard procedures.
It was also possible to measure the formation rates of halocarbons by two macro-algae, Laminaria digifafaand Dilsea sp., collected at Bear Island.
All samples were preconcentrated with a purge-and-trap technique prior to the final determination with capillary gas chromatography.
Table 4.1
Summary of samples collected at stations during the first Part
of the cruise.
Prel iminary results
One of the main goals is to get information regarding the surface water concentrations of naturally produced halocarbons, in order to be able to estimate the ocean
source strength. We have earlier pointed out that not only do the formation of
these compounds vary between different parts of the world, but also with seasons,
and even, within a day. Therefore, care should be taken when global estimates are
to be made.
In an autumn situation, one is likely to believe that the algae responsible for the
formation of these compounds should not be as active as during summertime.
Surprisingly, we found that the mean surface concentrations of the biogenic compound bromoform was approximately around 8 ng/l, which should be compared
with an investigation made in the high Arctic in 1991, where the mean concentration was around 4 ng/1. The levels of bromoform found during this cruise are also
higher than mean concentrations measured in the coastal sea of the Skagerrak.
The high values are supported by the results from the filtration experiments. As
can be Seen in Figure 4.1, all the different-sized fractions produced bromoform in
significant amounts. It can also be seen that the ability to produce the two chlorinated ethenes trichloroethylene and perchloroethylene increases with decreasing size
of the micro-organisms.
The distribution of halocarbons in the water column is exemplified in Figure 4.2.
Carbontetrachloride (CC14) is a compound of mainly anthropogenic origin. Consequently, the concentration is highest at the surface, and decreases towards the sea
floor. The complicated distribution of a compound with both an anthropogenic
and a biogenic source is exemplified with the depth profile of perchloroethylene.
ng/
UQ
chio h
Trf
Figure 4.1
Per
CHBr3
The production rates of three halocarbons by different sized
micro-organisms (stn 25).
Tri: trichloroethylene
Per: perchloroethylene
CHBr3: bromoform
500
-
1000
-
1500
-
2000
--
2500
-
3000 -
Figure 4.2:
Depth profiles of two halocarbons (stn 41)
Perchloroethylene
Carbontetrachloride
4
(C. Albers, H. Auel, B. Niehoff, B. Strohscher)
Bongo-net hauls (mesh size: 200 and 310 um) and Multi-net hauls (mesh size:
150 pm) were performed at 20 and 6 stations respectively. The investigations concentrated On the vertical distribution, reproduction, overwintering strategies, lipid
Storage and composition of dominant copepod species in different parts of the
Greenland Sea.
The Northeast Water Polynya on the East Greenland Shelf has been the subject of
the International Arctic Polynya Project (IAPP) studies since 1993. During ARK
XI/2 Multi-net hauls were taken to study the Stage composition and vertical distribution of the overwintering population of herbivorous copepods under autumn
conditions. Net samples were fixed in 4% Formalin and transported to AWI for final evaluation. Together with the Summer data of the previous cruises, this will
allow us to estimate the development and growth during the productive season
and to reconstruct life cycles of dominant species. The results will also improve
our understanding of the overwintering strategies of different species. About 640
samples of different Calanus species and stages were frozen for later analysis of carbon and nitrogen content and dry mass. The results will increase knowledge of the
standing stock of biomass and the secondary production.
In the Greenland Sea Gyre, Multi-net and Bongo-net hauls were taken to study
Calanus hyperboreus, which is a key species in the food web of the Greenland Sea
due to its size and abundance. In contrast to other calanoids, gonadogenesis and egg
production is based On lipid reserves accumulated during the previous Summer.
Observations during ARK XI/2 showed that nearly 50% of the females were mature and produced eggs in October. To study the spawning physiology and molting
behaviour in detail, females and copepodid stages IV and V were collected for laboratory experiments. Of special interest is the role of the lipid metabolism in the egg
formation.
Lipids are of major importance for the survival of zooplankton organisms in polar
regions. Extensive lipid storage acts as an energy reserve for overwintering and, in
some cases, reproduction. Herbivorous species especially depend On lipid reserves
to survive long starvation periods, when the darkness of the polar winter or ice
Cover prevent primary production. In addition, lipids are important components
of biomembranes.
In order to study the seasonal lipid storage of zooplankton organisms, individuals
were collected and sorted On board according to species, ontogenetic Stage and Sex.
In total, 360 samples were frozen (-80°C)Their lipid content and composition will
be analysed in the Institute for Polar Ecology, Kiel. Research concentrated on the
polynya region and two transects (79 and 75ON) in order to elucidate the effects of
sea ice coverage On lipid storage. Comparisons between different oceanographic
domains, e.g. polar East Greenland Current, arctic Greenland Sea Gyre and borealatlantic West Spitsbergen Current, are also possible.
Data obtained under autumn conditions will complete the investigations of seasonal energy storage of zooplankton in high latitude ecosystems from late winter,
spring and summer. Using these data it is possible to calculate the energy demands
of overwintering and the role of lipids for the energy flux within the ecosystem.
These results contribute to the ecosystem studies of the Joint Reseach Programme
313 (SFB 313) at Kiel University. In addition, the potential of specific lipid components as trophic biomarkers will be studied in CO-operationwith the AWI.
Wax esters serve as long-term energy reserves, whereas triacylglycerols act as shortterm fuels. In order to determine the molecular species of these lipid classes, zooplankton samples, especially Calanus spp.. have been stored in dichlormethane/methanol (2/1) at -30°Cuntil gas chromatographic analysis can be performed
in Bremerhaven. In comparison to other marine taxa, polar copepods contain
highly unsaturated phospholipids, which are very important in maintaining the
fluidity of biomembranes even under low ambient temperatures. Investigations
should elucidate the composition of these molecular species.
Hitherto, research has focused On larger species that dominate the biomass, e. g.
Calanus spp.. The aim during the expedition ARK XI/2 was to determine the fatty
arid and fatty alcohol composition of abundant smaller species, e. g. Oithona spp.
and Oncaea spp.. Altogether 21 Bongo net hauls were conducted and more than
6300 animals of the species Calanus hyperboreus, Calanus glacialis, Calanus finmarchicus, Oithona spp. and Oncaea spp. were collected for investigations in
Bremerhaven.
6.
MULTI-DISCIPLINARY SEA ICE INVESTIGATIONS
The Greenland Sea area is the major outflow region of pack ice from the central
Arctic Basin. Our studies aimed to outline the physical, chemical and biological
properties in Arctic drifting ice floes in the autumn/winter transition time which
is characterized by decreasing air temperature and light intensities.
Our studies focused on three major questions: a) What kind of organisms are incorporated into newiy forming sea ice, b) What are the characteristics of the sea ice
biota in late autumn, and C) What organisms are found in the ice-water interface at
this period of the year.
6.1
Formation of sea ice
(R. Gradinger, E.J. IkävalkoT. Mock, Q. Zhang)
Studies on the sea ice formation in Antarctica have revealed, that protistan organispts are incorporated already into the initial stages of newly forming sea ice.
During the sea ice formation, a succession of several characteristic stages has been
described as the "pancake ice cycle", and suspended particulate matter including
microorganisms accumulate in newly forming ice primarily due to physical concentration mechanisms. It has been shown that algal populations are "scavenged"
by frazil ice crystals rising through the water column. Furthermore, incorporation
of plankton organisms may be supported by wave fields that pump water through
the new ice layer, thus enmeshing cells between ice crystals.
During our cruise we studied the physical (temperature, salinity), chemical (nitrate,
nitrite, phosphate, silicate) and bioiogical characteristics (Chlorophyll a/ cell abundances, species composition) of different types of new ice (grease ice, pancake ice,
nilas ice). Preliminary information On the variability of protists inhabiting the different stages of sea ice formation was gained by light microscopy of live material.
The most versatile communities were found in pancake ice, with numerous phototrophic and heterotrophic flagellates, whereas grease ice was mainly dominated
by pennate and centric diatoms. The variability of protist communities in the surface water was generally lower than in the other samples studied. Thus, the phototrophy seems to prevail in the early stages of the sea ice formation, whereas heterotrophy increases in importance in the later phases.
Two experiments were made in order to understand a) the effect of freezing rate on
organism inclusion and b) the early succession Patterns after an ice sheet has formed.
6.2
Effect of freezing rate on organism incorporation
(E.J. IkävalkoR. Gradingcr)
An experiment on the new ice formation was made in order to study the effect of
slow and fast ice formation processes on the incorporation of protists into the sea
ice. Slow ice formation was achieved by placing an experiment tank with 40 liters
of freshly collected surface sea water onto the working deck (air temperature
-11,4 'C). The ship's cold room of -30 ' C was optimal for establishing fast ice formation. Measured environmental variables in the beginning of the experiment
were water salinity and the temperature of both the water and the air. The ice
formation was allowed to continue in both tanks for ca. 4 hours, after which,
together with the variables mentioned above, the surface and bottom ice
temperature and the brine salinity was measured. In the beginning and the end of
the experiment water samples were collected. These, together with brine samples
serve in the species identification and enumeration of the protists. The obtained
material was studied live and documented by photography and video recordings
shortly after the sampling. Further examination On the preserved material will be
done both light, epifluorescence and transmission electron microscopically.
6.3
Microcosm Sea ice formation experiment
(Q. Zhang, R. Gradinger)
In this experiment we wanted to follow the evolution of a nilas ice layer on a larger water body (900 1) over a period of at least two weeks, monitor the related changes of the abiotic and biotic parameters both in the sea water and inside the ice cover under natural light and temperature conditions.
A plastic tank (100 X 70 X 150 cm) was fixed on the working deck of RV "Polarstern"
and filled with 900 1 of 64 pm filtered sea water at the location of 79'2'N, 2'59'W on
8 October 1995. Ice formation started with the air temperature below -5OC, and an
ice sheet grew rapidly from initial 1.5-1.8 cm (after 12 hours) to 11 cm after three
days. The maximum ice thickness of 16 cm was reached after 16 days, when the last
sampling was done and the experiment was finished.
In the experiment tank, the surface was covered with a solid ice sheet. A layer of ice
crystals, each of about 1 mm thickness and different shapes, had formed in the interface between the solid ice and the water body below. Thus, three different types
of samples could be obtained: 1) ice Cover, 2) ice crystal layer, and 3) water body.
Temperature, salinity, nutrient (NO3, NO2, PO4, Si) and chlorophyll 2 concentrations were measured in all sample types every second day. Subsamples were fixed
0
4
b)
0
0
12
16
Salinitv
4
C)
Days
8
Days
12
16
12
16
Chlorophyll-?
,
;
'
0
4
Days
Figures 6 a/b/c: Results of a tank experiment
with borax-buffered formalin (1.0 % final concentration) for further analysis of the
abundance of algae and bacteria by light and epifluorescence microscopy.
The air temperature varied in the Course of the experiment between +l° to below
-9.5OC. While the temperature of the solid ice sheet followed the air temperature
changes but in lower magnitude, the temperature of the water body and the ice crystal layer were nearly stable at about -2 to -3OC (Fig. 6.1a). As an effect of the ice
growth the salinity of the water body increased with time, while the salinity of the
ice sheet decreased due to desalination processes (Fig 6.1b). The chlorophyll a concentrations in the water column and the ice crystal layer were relatively constant,
whereas in the ice cover a decrease was observed (Fig. 6 . 1 ~ ) .
6.4
Autumnlwinter conditions within Arctic sea ice floes
(R. Gradinger, E.J. IkävalkoT . Mock, Q. Zhang)
The Arctic sea ice is inhabited by a diverse community of bacteria, protists and metazoa. Our main scientific concern was to determine the physical and chemical
properties of the ice cover which correspond to the observed distribution of the
biota within the ice column.
At 8 stations ice cores were drilled from Arctic ice floes with a 10 cm ice auger. The
vertical distribution of temperature, salinity, nutrients and biological properties
(Chlorophyll a/ species abundances and composition) was investigated with a vertical resolution of 1 to 20 Cm. A particular emphasis was on a detailed study of the
protistan community. In order to survey the versatility of the protists inhabiting
the sea ice biota samples were collected from both the ice floes and the beneath
lying water column. Thus, the material consists of brine, together with 50 and
10 um net samples. Immediately after the sampling the material was concentrated
by a centrifuge, and protists were examined live with an interference microscope.
Documentation was done photographically and by video-recording using an inverted microscope. Based on light and electron microscopical preparations made
On board further identification of e.g. scale- and lorica-bearing protists will be done
at the University of Helsinki, Finland. A total of three serial dilution experiments
were conducted using brine water. These experiments will give estimates for the
in-situ growth and grazing rates of sea ice bacteria and protists.
Two experiments (dark survival and salinity tolerante) were conducted to test the
reaction of ice algae onto decreasing light and temperatures which are both typical
for the autumn/winter transition.
Experiment 1: Dark survival of Arctic aleae
(Q. Zhang, R. Gradinger)
Polar marine ecosystems are characterized by strong seasonal and interannual variations of environmental factors like the extent of the ice cover and solar irradiance. With the onset of polar winter, the available light intensities are reduced
to nearly total darkness for periods of up to 6 months. It has been suggested that
algae overwinter as resting Spores with reduced metabolic rates. Although winter
survival of the ice algal community is necessary for the seeding of the annual
spring development, dark survival in polar marine algae has received little attention. Thus, an experiment was designed to investigate the survival strategies of
Arctic algae in the darkness over a period of 5 months.
Grease ice was collected at a position of 79'2'N, 2O59'W in the Greenland Sea, melted and filtered through a 64 pm gaze to exclude larger zooplankton. 40 bottles
(50 ml each) were filled with the water and stored in the dark at a temperature of
+2OC. Measurements on abiotic and biotic Parameters will be carried out every
seven days in the first month, every 14 days in following four dark months, and
every five days after the total five dark months. In the end of the experiment the
algae will be exposed to increasing light intensities at a temperature of +4OC. The
microscopical analysis will focus On the identification of different adaptation
strategies.
Salinitv tolerance of Arctic alc-ae
(Q. Zhang, R. Gradinger)
Particularly during the periods of brine drainage and ice melting microorganisms
inhabiting the brine channels of the Arctic sea ice are exposed to strong seasonal
variations in the brine salinity. Ice algae are known to have adaptations to low
water temperatures and increasing salinity which take place during wintertime in
the ice. Earlier studies have demonstrated that Arctic sea ice diatoms are relatively
euryhaline and can maintain growth rates of 0.6 to 0.8 divisions per day over a salinity range of 10 psu to 50 psu. In the Antarctic, the bottom community of ice algae have shown a positive correlation between the growth rate and water salinity,
the latter ranging from 11.5 to 34 psu. Culture experiments have revealed that ice
algal growth continued even in temperatures of -5.5OC and a brine salinity of
95 psu.
Our experiment was designed to study the response of the growth of Arctic sea ice
algae to salinities ranging from 1 to 100 psu. For that purpose ice cores were taken
from an Arctic ice floe at the location of 79'59'N, 4'14'W in the Greenland Sea.
The bottom 1 cm of two ice cores were let thawn in an excess of 0.2 pm filtered sea
water. Salinities of 1, 10, 20,32, 40,50, 60, 70, 80, 100 psu were achieved by the addition of either high salinity brine (124 psu) or low salinity meltwater from the
Same ice floe (1 psu salinity). Larger metazoans were excluded by the filtration of
the samples through 64 pm gaze. The algae were incubated at a light/dark cycle of
8:16 hours and a temperature of +l°C
The experiment was continued for 19 days. Subsamples (25 ml) were collected
1, 3, 6, 9 and 14 days after the Start and in the end of the experiment. These were fixed with borax-buffered formalin (1% final concentration) and will be used for
light and epifluorescence microscopical analysis of species abundantes and biomass.
Autumn Under The Roof - The Under-ice Community
(I. Werner)
The world under an Arctic ice floe is a habitat with special and variable conditions.
The underside of the ice is not an even and homogenous surface, but rather characterized by a variety of cracks and crevices, undulations or rafted pieces of other
floes. Even entire floes can underlay each other, thus building a complex under-ice
landscape. This is the environment for a specialised under-ice community.
During ARK XI/2, a total of 5 ice stations on multi-year ice floes were used to investigate the characteristics of the Arctic under-ice community. Temperature and salinity profiles were recorded over the upper 5 metres of the water column under
the ice and the underside of the ice was sampled for measurements of chlorophyll g and the C / N ratio. In order to gather information on the morphology and
structure of the habitat as well as on abundance and distribution of under-ice
amphipods, a videocamera was deployed under the ice. A pumping System delivered quantitative samples of the sub-ice fauna, caught from the waterlayer directly under the ice. Furthermore, under-ice amphipods recovered from Bongo net
catches (200 and 310 [im) done by the zooplankton working group were deepfrozen for lipid analyses. On board "Polarstern", experiments with under-ice amphipods were carried out to gain insights into the feeding ecology and fecal pellet
production of this group.
In contrast to the summer situation, where melting processes occur, neither temperature nor salinity gradients were measured under the ice floes during this autumn expedition. Water temperature ranged from -1.3OC to -1.6OC with salinities of
30.6 to 32.8 psu.
The morphology of the underside of the floes was characterized by a quite smooth
structure and only shallow undulations. Dense aggregations of decaying algae were
frequently observed in depressions here, as well as patches of algae inside the ice
itself. Chlorophyll g concentrations in the lowermost 1 cm of the ice ranged from
0.7 to 195.8 pg/l between stations.
Based on net samples and video observations, Apherusa glacialis was the most
abundant species of the under-ice amphipods, followed by Gammarus wilkifzkii,
while Onisimus spp. was quite scarce. First results of the feeding experiments indicate that A. glacialis is probably the only herbivorous under-ice amphipod, whereas the other species are rather omnivorous. G. wilkifzkii showed even a pronounced preference for feeding On crustaceans.
There was virtually no makrozooplankton (> 200 km) in the waterlayer below the
ice. During the Summer, sometimes dense swarms of pelagic copepods (Calanus
glacialis) or pelagic amphipods (Themisfo libellula) can be found here, probably
feeding on ice algae sloughing off from the floe. However, a very diverse and
abundant community of smaller zooplankton (>50 [im) seems to dominate this
habitat during both seasons, e.g. naupliar Stages, cyclopoid copepods (Oifhona spp.)
and above all, several groups of harpacticoid copepods (Tisbe sp., Halectinosorna
sp., Microsetella sp.), which are partly described to live also inside the ice.
Further analyses and experimental work on all members of the under-ice community, which is thought to function as a mediator for the production and transport
of organic matter between the ice and the water column will hopefully throw some
light onto the cryopelagic coupling processes. In particular, the fecal pellet production and sedimentation of particles from the ice are important points for the multidisciplinary approach of the SFB 313.
7.
BATHYMETRICMAPPING INTHE F'RAM STRAIT
(U. Lenk, J. Monk, V. Sackmann)
Introduction
The area of the Fram Strait between Spitsbergen and Greenland plays a key role for
the water exchange between the North Atlantic and the Arctic Ocean and is therefore subject of investigations of various disciplines. Besides the collecting of samples and the observation of physical Parameters, it is necessary to have reliable
depth Information as a description of the sea bottom topography, i.e. bathymetric
data available for planning and conducting of detailed studies of the region.
One project of the Bathymetric Group of AWI is concerned with the preparation of
bathymetric charts scale 1:100000 of the Fram Strait as a basis for further investigations by other sciences. The surveys conducted during ARK XI/2 were intended to
fill existing gaps in the bathymetric data and to provide the opportunity to check
and adjust the results of previous surveys with less accurate navigation using the
newly gathered data as a reference.
The HYDROSWEEP measurements were started at position 74.B0N, 12.0° on the
23th of September 1995 at 0830 Universal Time Coordinated (UTC). The system was
running continuously during the whole cruise with some minor exceptions caused by system failures or the requests of other disciplines to stop the transmission
of acoustical signals into the water column, as the HYDROSWEEP signal caused
difficulties in finding the moorings deployed in the Greenland Sea for the subsequent recovery. Another reason for interrupting the logging of data was given
when the ship was steaming through heavy ice, and no reasonable signal could be
recorded.
As a result of ARK XI/2 about 1205 nautical miles of run lines were sailed resulting
in an area of about 10 500 km2 being surveyed.
Data Storage was conducted on a daily basis. The raw bathymetric data is stored on
magnetic tape by HYDROSWEEP; additionally, an interface to the VAX-cluster is
installed where the profiles are recorded. The latter files are used as the basis for
further processing. Navigational data is also stored separately on disk, and all data
is time-tagged with regard to UTC in order to relate the different types of data to
each other during the subsequent post-processing.
Survev Instrumentation
During several expeditions in 1984, 1985, 1987, 1990 and 1991 hydrographic surveys
were conducted with RV "Polarstern". Until 1989, the SEABEAM system was used
to gather bathymetric data, and positioning was mainly based on the TRANSIT satellite system operated by the US Government Department of Defence.
The TRANSIT satellite system forms a "birdcage" of circular, polar orbits about
1075 km above the Earth. Thus, fixes can only be recorded every few hours depending on the number of available satellites and the latitude of the ship's position.
The time gaps between the fixes had to be filled by dead reckoning Systems.
Problems involved with these systems include their decreasing accuracy with time,
and offsets are likely to occur in the positioning data when the next TRANSIT satellite fix occurs. These offsets can be in the range of several nautical miles.
As a result of the offsets and the overall accuracy of TRANSIT, the accuracy of positioning is likely to be in the range of 500 m and worse in poor conditions, even
after substantial interactive post-processing. This accuracy is unacceptable for the
planned charts at a scale of 1:100 000, as a displacement of 500 m in position would
result in 0.5 cm on the chart.
Nowadays, the NAVSTAR GPS system is used for positioning, and the ATLAS
HYDROSWEEP system has replaced the SEABEAM system in 1989. HYDROSWEEP
operates at a frequency of 15.5 kHz and measures athwardship oriented profiles
consisting out of 59 preformed beams (PFB) from 10 m down to 10 000 m depth.
The opening angle of the swath across the ship's axis varies between 90' and 120°
and the aperture along the main axis is about 2'. Thus, the footprint of PFB beam
Covers an area of approx. 2' by 2' squared. The system is automatically calibrated for
speed of sound in a patented procedure called cross-fan calibration where the mean
sound velocity is determined in a Least Squares process by comparison of a swath
measured along the ship's main axis to the standard survey cross-profile as observed by the centre beam. In addition to this calibration, a keel sonde is installed for
the determination of speed of sound at the surface.
The use of NAVSTAR GPS for navigation and positioning has led to dramatic
changes in the seafloor topography from previous surveys in regions with bad navigational aids. Today real-time differential positioning with GPS (D-GPS) provides absolute positions referenced to the World Geodetic System 1984 (WGS84),
with an accuracy of up to k5 ... 6 m, depending on the mode in which the system is
operated and the reference station which is used. However, in remote areas such as
the Greenland Sea, where n o differential reference station is yet available to
achieve these high accuracies, positions are only accurate to ±I0 m. During the
commissioning phase of GPS, there was no full coverage by the system, and the si-
tuation was similar to the time when navigation was based on TRANSIT, i.e. the
gaps had to be bridged by dead reckoning Systems, and offsets resulted from new fixes.
As the overall accuracy of positioning is now far better than at the beginning of hydrographic surveys on board "Polarstern", it is possible to check existing low accuracy data using the new high accuracy data as a reference.
Survev operation
In order to achieve the best coverage of the survey area, a box survey was planned
prior to the expedition (see Fig. 1.1)with regards to the time schedule and altered
according to the conditions prevailing On the cruise.
During the actual survey operation, the system has additionally to be observed to
ensure the best results possible and to prevent a break-down of the system. One
major error source in bathymetry is the use of a wrong value for the mean speed of
sound. As the quality of the determined depth is directly dependent on quality of
the latter value, it is of vital importance to check the applied sound speed value in
regions with a hillocky underwater topography.
Problems were observed when the sea bottom is flat without much topographic
variation. In case that a wrong value for the speed of sound is used, the measured
profiles will be bent symmetrically to the centre beam. If the speed of sound used by
the system is too high, both ends of the profile will be bent upwards, and if the value is too small, they will be bent downwards. This will result in an apparently
symmetric shape of the sea bottom indicated by contour lines which are parallel to
the ship's track.
To check the data obtained, the measured cross-profiles are displayed on-line, and a
bottom map is scrolling over a screen. In addition, on-line charts are plotted in order to observe the quality of the data by comparing of adjacent swath-profiles and
to check the coverage achieved by neighboured swathes.
Svstem Test
In addition to the normal survey operations, a system test was performed as it
seems that there are still some systematic errors causing distortions in the measured profiles. These distortions occur symmetrically to the centre beam of HYDROSWEEP near the pre-formed beams No. 14 and 46 and result in an hill-like effect.
They are sometimes referred to as "the dikes of the profiles". The manufacturer of
HYDROSWEEP, STN ATLAS ELECTRONIC, Bremen, Germany, asked to record
deep sea data from a flat sea bed in order to investigate these distortions which also
occur On other research vessels with HYDROSWEEP. This data will be processed
after the cruise at ATLAS for further improvements of the system.
8.1
Pelagic production regimes of Open water, marginal ice Zone
and under the ice
(0.Haupt, G. Donner, M.Krumbholz)
Planktological research within the SFB 313 at Kiel University focused on processes
that control the formation and modification of particles in the upper layers of the
Northern North Atlantic, their settling through the water column and their fate
before they finally reach the deep sea floor. The investigations conducted during
ARK XI/2 focused On the relation between pelagic processes and vertical particle
fluxes in the marginal ice Zone of the Greenland Sea. Special attention is given to
the pelagic and ice-associated production regimes which are expected to differ with
respect to quantity and composition of matter exported from the euphotic zone.
Stations had been sampled at 2000 m, 1200 m, 800 m and 200 m depth on a transect
normal to the continental slope within the marginal ice zone. Also a slope parallel
transect at 2000 m depth from 80°30' to 79ON with ice cover from about 10/10 to
1/10 were sampled. Water from different depth was taken with a rosette water
sampler and filtered to measure phytoplankton biomass, suspended particulated
matter (Seston), elements (C, N, P, Si) and algal pigments (HPLC analysis). Water
samples for microscopic investigations of species composition were fixed with
borax-buffered formalin. At two mooring positions at 75ON with water depths of
400 m and 3000 m which were already investigated during the summer cruise ARK
X-1 for long term explorations of the seasonality and the interannual variability of
bentho-pelagic coupling. Additionally, water samples were collected along a transect at 75ON extending from 13O40'W to 17OE with a total of 19 stations to measure
the already mentioned planktological Parameters within the upper 500 m of the
water column.
First results of chlorophyll measurements show a system state which is typical for
low light conditions in fall. In the northern Part of the Eastern Greenland Sea we
found values mostly below 0.1 microgram per liter and chlorophyll a/phaeopigment ratios of about 1 within the upper 100 m.
The area at 75ON shows chlorophyll values below 1 microgram per liter and a more
divers chlorophyll a/phaeopigment ratio with mean values greater 1. Figure 8.1
shows the chlorophyll 3 and phaeopigment distribution of the 75' transect. Highest
chlorophyll 3 values were found in the upper cold Arctic water mass in the marginal ice zone. Depending On the ice cover the low light level of the surface layer
results in a sharp decrease of chlorophyll concentration with increasing depth.
Chlorophyll 2 as well as phaeopigment concentrations shows homogeneous tendency in deeper water layers of the warmer atlantic water masses. Relatively high
pigment concentrations in a depth of about 60 to 100 m may be caused by fecal
pellets and aggregates rather then by living phytoplankton cells.
latitude
Fig. 8.1: Vertical distribution of chlorophyll
a (a) and phaeopigments (b) at 75ON
Measurements of vertical particle fluxes from the various regimes in the marginal
ice Zone
Within the last years the field work of the SFB 313 has focused on the seasonally
ice-covered region of the Greenland Sea. Measurements of vertical flux in this
region are conducted to collect particles exported by different pelagic production
regimes in relation to seasonal retreat of the ice. During this cruise, moorings
which were deployed in cooperation with AWI in 1994 during the expedition
ARK X/l were recovered successfully with a total of 4 sediment traps (AWI 4134/OG 7 at 3000 m and AWI 410-2/OG 8 at 400 m depth). A mooring deployed in
Mai 1995 at 75ON, 3O55'W with RV Johan Hjort (OG 9) was also successfull recovered. A first look at the collected material in the sampling glasses shows a clear
annual cycle of vertical particle flux with high rates during spring and summer.
A long term mooring (OG 10, collecting time 1 year) at a position of 75¡03.4'N
04'35.7'W was deployed with 3 sediment traps in 500, 1000 and 2000 m depth as
well as 3 current meters each about 20 m below the traps. This area is within the
seasonal ice-covered Part of the Greenland Sea. Because of the influence and the
variability of the ice Cover on the production of biogenic matter we predict a direct
relation between the location of the marginal ice Zone and the sedimentation of
organic particles. The mooring will be recovered in August 1996.
Experimental studies with dominant organisms
To analyse changes in pigment signature and composition of other biogenic compounds and for comparison with sediment trap samples, experiments for fecal pellet production were made on board with the dominant zooplankton species
(copepods, amphipods and euphausiids) to analyse changes in pigment signature
and composition of other biogenic compounds and for comparison with sediment
trap samples.
Dominant copepods (Calanus hyperboreus and Calanus glacialis) were sampled
with a Bongo Net and cultivated for different experiments which will be conducted
at Kiel University
8.2
Bentho-pelagic coupling
(Angelika Brandt, Jör Stefan Berg, Michael Gedamke, Angela Lunau,
Eberhard Sauter, Annette Scheltz, Klaus Schnack, Susanne Wanner)
Background
Quality and quantity of organic carbon reaching the seafloor have a direct effect on
the benthic community. Organic particles are enriched in the BNL (bottom nepheloid layer) and in the upper sediment layer, where they are the main food source
for benthic organisms. Composition and quality of these particles are influenced by
the vertical sedimentation, by lateral advection, by biological and chemical modification of the particles in the water column and at the seafloor, by the bottom topography, as well as the seasonal deposition of particles due to spring blooms and the
production of ice algae at the floes margins.
Objectives
Our work will focus On the interactions between the BNL and the upper sediment
layer. In this respect it is crucial to investigate composition, abundance, diversity,
and community patterns of benthic organisms, which take up organic particles, incorporate them into the sediment by biodeposition and bioturbation processes and
also play an irnportant role in the recirculation of organic material by resuspension. Therefore we will also try to scrutinize the interaction of the amount, the
composition and the flux of particles in the BNL and the patterns and activity observed in the benthic communities.
Moreover our program encompasses work on the following aspects:
0
*
*
*
evaluation of the degree of bentho-pelagic coupling along the Northeast
Greenland continental margin
investigations of the composition, abundance and diversity of macrobenthic
communities, especially peracarid crustaceans and polychaetes (which are
most important in terms of numbers) and seafloor/BNL-properties
assessment of micro- and mesoscale dispersion patterns of benthic
populations
investigation of metabolic activities and bioturbation potential of the total
sediment communities by measurements of biochemical parameters at
certain sites, as well as the macro- and megabenthic (i.e. sponges)
communities
the analyses of BNL characteristics in terms of the amount and composition
of particles in relation to near bed current velocities and direction
impact of biodeposition and bioentrainment on the particle composition in
the sediment in in situ experiments
In order to reach these goals, a normal transect at 79ON, at 2000 m, 1200 m, 800 m,
and 200 m depth had been sampled, and additionally a slope parallel transect in
about 2000 m depth consisting of 4 stations and extending from 80°30' to 79ON,
off the Greenland continental slope. We hope that this slope parallel transect will
cover different conditions of particle supply to the benthos due to variable surface
production in areas of permanent ice cover, ice edge situations and Open water.
The normal transect will provide information on the depth distribution and dispersion patterns of benthic communities and characteristics of the BNL. Additionally we will investigate bentho-pelagic coupling processes at 2 revisited SFBmooring stations at 75O, NE Greenland.
A Set of various benthos equipment has been used to serve our purposes. For
faunistic studies and comparison the giant box corer, the Agassiz trawl and an
epibenthic sledge with a newly constructed supranet at about 1 m above the bottom
(additionally to the epinet), will be employed. The vertical distribution of chemical
and biogeochemical parameters will be assessed by deploying a multiple corer and a
newly designed 02-profiler called "Floorian". For the characterization of the BNL a
modified bottom water sampler will retrieve water samples and thus provide in
formation on current velocity and direction within the last meter of the BNL, i.e.
just above the sediment water interface.
First results
AGT (Agassiz trawl)
During last year's cruise of "Polarstern" into the arctic waters some evidence of
high sponge densities was found. Sponges are filter-feeding organisms that feed on
phytoplankton, detritus and bacteria. Some of the sedimentary organic matter will
eventually reach the BNL, where it might be available to sponges. However, size
classes of the consumed particles as well as the composition of the food and the
influence of the flow velocity to the particle retention rate are only known for very
few species (see e.g. Witte, U., 1995). Therefore we have only little information
about the possible contribution of sponges to sediment formation. These question
will be approached in a laboratory study with living sponges (Geodia mesotriaena)
that were caught in the Greenland Sea.
On five stations we employed the Agassiz-Trawl, three of these were taken on the
transect from 2000 m to 200 m depth onto the Greenland shelf. The three trawls on
the transect running perpendicular to the shelf were taken at 1200 m, 700 m and
200 m depth. All three trawls were successful, but no or only few sponges came up
with it. At the 1200 m station, most of the catch consisted of fine mud, but we also
found some shrimps and bottom living fishes (e.g. ray). The trawl contained
Ophiuroidea and Priapulida, we tried to keep them alive in aquaria. Actinians,
brittle stars, decapods and some fish were sampled at the 700 m station. The diversity and biomass was highest in the 200 m trawl, where we found 3 species of sponges, several amphipod species, 1 Sclerocrangon ferox, many Heliometra, 5 Holothuroidea and a few polychaetes. All of the Heliometra died after 20 days of being
kept in the aquaria, although they have been observed feeding. The water volume
might have been too small, and flow velocities too weak for these animals.
Two further trawls were taken 75ON at 800 m and 400 m depth. The first one at
800 m was very successful as the catch consisted almost completly of sponges
(Geodia mesotriaena) and a few octocorals. Except for five sponges, all of them are
still alive in aquaria for later experiments in the laboratory. About 900 m2 of
seafloor were sampled, therefore I could calculate a sponge density in this area of
about 0.3 individuals per m2- The last trawl taken consisted of two Gorgonocephali
in very good condition, few fishes, and some sponges.
BWS (bottom-water sampler)
In order to receive information about the hydrodynamic sorting of the organic
matter near the seafloor, we took samples from 7 cm, 12 Cm, 20 cm and 40 cm
height above the seafloor with the bottom-water sampler. The water was filtered to
analyse its content of chlorophyll, POC (particulate organic carbon), PON
(particulate organic nitrogen), and total supended matter. 200 ml of each sample
were fixed with formalin to Count bacteria and phytoplankton (e.g. diatomes). On
each deployment of the BWS, a video camera was installed in 40 cm height above
the seafloor as well as a current and a turbidity profiler. The hydrodynamic sorting
of the organic matter is crucial for the benthic animals, because it determines the
quantity and quality of food they receive. The whole sedimentation regime is influenced by the hydrodynamic processes near the seafloor.
At seven out of nine stations we took water samples and employed the video camera with the BWS. At the 1200 m station of the slope-normal transect, the BWS
could not be employed because of the strong ice drift. At the last station at 75ON
(water depth: 400 m) the control unit broke down so that we could not get samples
at that station either. The 200 m station remarkably showed very good video images of different species of mysids and 1-2 amphipod species. The parallel EBS-hau1
at that station enabled us to determine the most frequent mysid as Boreomysis arc-
t ica .
The chlorophyll contents of the water samples were already analysed on board. As
expected for this time of the year, the chlorophyll a and phaeopigment values of
the water were very low in all samples taken.
EBS (epibenthic sledge)
Within the macrobenthic communities, peracarid crustaceans play as important a
role as polychaetes, as they occur in large numbers and are usually quite diverse. In
order to catch a high number of individuals, an epibenthic sledge was employed,
which was first modified after a construction of Rothlishberg & Pearcy (Rothlishberg & Pearcy, 1977). This sledge originally consisted of a single box. Its opening
measures 33 X 100 cm and is at about 25 cm above the bottom. As many peracarids
are vagile (e.g. Amphipoda, Isopoda, Cumacea migrate in the water column during
the nichts), or exhibit a suprabenthic mode of living (Mysidacea), an additional
supranet with the Same size was constructed and fixed above the epinet (Brandt &
Barthel) 1995). It extends from 1 m to 1.33 m above the ground and helps to
separate supra- and epifauna more clearly.
In total the epibenthic sledge had been employed at 10 stations, 8 of these have
been sampled successfully. At 80°30' about 2000 m depth, the sledge did not work
properly and came up damaged. The second failure occurred at about 75ON around
2800 m depth.
Up to now it has only been possible to analyse the content of the supranets of the
samples. As well as varying numbers of decapods, euphausiaceans, chaetognaths,
ostracods and calanoid copepods, peracarids have been sampled at all successful
EBS-stations. Within the Amphipoda, most species belong to the families Ampeliscidae, Amphilochidae, Calliopidae, Eusiridae, Isaeidae, Lysianassidae, Pardaliscidae, and Stegocephalidae. All Cumacea found in the supranet were specimens
of the genus Diastylis (Diastylidae). Eurycope was the most frequent isopod genus
in the supranet, however, a single, well preserved specimen of the deep-sea isopod
Munnopsis typica (Sars) was found at station 37-018. Other common isopod families were the Ilyarachnidae, Nannoniscidae, and Munnidae; the Mysidacea were all
members of the family Mysidae, the most frequent genera were Boreornysis, Eryt-throps, and Pseudomma. Only a single species of Tanaidacea, Sphyrapus a n o r m lus (Sars), was found in the supranet.
The following table shows the differences in the supranets at the different stations.
The values are total numbers collected and are not yet standardized for a 1000 m
haul.
Peracarida in the supranet of the EBS
Station
1 Amphipoda 1 Cumacca 1 Isopoda
37-008
I37
1 Mysidacca 1 Tanaidacea 1 S u m
I0
I 39
"The higher number of Peracarida at station 37-027 is an artifact, as the supranet contained some sediment in the cod end and must have been trawled partly upside down.
GKG (giant box corer)
To investigate the relationship between surface production and benthic community structure, the macrobenthos was sampled quantitatively with a box corer (50 X
50 cm surface). The box corer was employed at 9 stations, in total 25 cores were
sampled. From each core 3 fractions were sampled:
-
1) the surface water above the sediment,
2) and a 25 X 25 cm subsample of the first cm of sediment, and
3) the next 5 cm of sediment.
These samples were sieved, fixed and partly sorted on board of "Polarstern". Some
living polychaetes (eg. Onuphis conchylega) were kept in aquaria for further observations at home. Additionally, smaller amounts of sediment were taken for determination of various sediment Parameters.
A very preliminary investigation of the infaunal distribution shows an impoverished community. This might be due to low food supply. Total abundance is estimated to 500 - 5000 animals/m2. The main dominant infaunal taxa are polychaetes,
followed in abundance by other groups including crustaceans, sipunculids, mussles
and holothurians. Within the polychaete fauna, important families are Spionidae,
Oweniidae, Maldanidae, Ampharetidae, Terebellidae, Lumbrineridae, Nephtyidae
and Polynoidae.
There are strong indications that the observed macrofaunal community structure
with low abundance and very low biomass reflects a low and variable food particle
flux.
One sediment core of 19 cm inner diameter and length of approximately 30 cm was
taken at each station and stored for further examination at 2OC. The cores were vertically dissected, the infaunal "Lebensspuren" were documented by photography
and eventually found animals were fixed separately. Additionally at each station,
samples for chlorophyll-equivalent analyses were taken.
MUC (multiple corer)
The MUC is able to take 8 sediment cores (10 cm diameter) simultaneously with in
haul. It was deployed 15 times at 9 Stations. Where the gear was used more than
once, the sediment was either too hard or too sandy to get proper sediment cores or
additional sediment cores were needed for incubation or other experiments. The
sediment cores were kept at a temperature of O0C to 1° after recovery until further
analysis. The described sampling and incubations (see below) were perforrned at all
stations except those, where insufficient sediment cores were recovered.
sampling: The upper 10 cm of the sediment cores were cut into horizontal slices
of 0,5 to 1 Cm. Depending on the parameter the samples were taken for, the sediment disks were subsampled. Subsamples were taken for measurements of
the following Parameters: ATP-concentration (biological activity), chlorophyllequivalent (sediment-food supply and bioturbation), C/N-ratio (geochemistry),
DNA-content (sediment activity), ^OPb (bioturbation), porewater nutrients
(iitrate, phosphate and silicate) and porosity (both for geochemistry).
shipboard measurements and incubations: The sediment oxygen demand was
measured on three sediment cores. Oxygen profiles were obtained from another
core for comparison with in-situ measurements (see FLOORIAN). Whenever
possible, one core was incubated with addition of Br-Ions in the overlaying water to study sediment porewater exchange rates (bioirrigation/geochemistry).
Luminophores (stained sediment particles) were used in three size-fractions
(<63 Pm, 63-125 Pm and 500-1000 um diameter) in order to study short-time
(5 to 8 days) bioturbation capacities of the smaller infauna. The average half life
of chlorophyll and its products of decay in the sediment column were also examined.
Additionally, the sediment surface was investigated for biological activity, for example burrow openings or tracks, which were documented photographically.
Floorian ( 0 7 profiler)
The diffusiGi boundary layer (DBL) is easily disturbed and compaction of sediment
might occur during the coring process, for example of a MUC. Also, quality of samples changes during recovery from the seafloor to the surface. These were the reasons for the development of in situ measuring methods.
On this cruise we were able for the first time to deploy the newly developed oxygen
in-situ profiler FLOORIAN in deeper water. In contrast to free falling lander systems, FLOORIAN is capable of measuring under ice covered water, because it is
deployed via the winch. The device also records a resistivity profile of the sediment. Additionally two cores for laboratory experiments and porewater analyses
are taken at each deployment.
FLOORIAN was deployed at eight locations. Four in-situ measurements were performed in the Fram Strait, and four at 75ON (where two deployments failed).
The in-situ data (Figure 8.2) will be used to calculate the fluxes of oxygen and
organic carbon, respectively. Together with oxygen profiles taken from cores
(measured On board), we will obtain information about the oxygen-penetration
depth. These were 3-12 cm at shallower localities (e.g 37-014, 800 m; 37-016, 190 m)
and some decimeters at deeper stations (e.g. 37-025, 2800 m).
Sometimes oxygen profiles show subsiduary maxima, which might be caused by
oxygen irrigated due to burrows of infaunal animals (e.g. polychaetes).
The fingerprint-like resistivity profiles (figure 8.2) characterize the respective sediment and also determine sediment porosity.
Literature
Brandt, A. & D. Barthel (1995): An improved supra- and epibenthic sledge for
catching Peracarida (Crustacea, Malacostraca). Ophelia 43 (1).
Rothlisberg, P. C. & W. G. Pearcy (1977): An epibenthic sampler to study the
ontogeny of vertical migration of Pandalus jordani (Decapoda, Caridea). - Fish.
Bull. U. S. 74: 994-997.
Witte, U. (1995): Reproduktion, Energiestoffwechsel und Biodeposition
dominanter Porifera aus der Tiefsee des Europäische Nordmeeres, Berichte aus
dem Sonderforschungsbereich 313, Nr. 53: 1-83.
0
M
f^
M
C;
0
.M
U
03
U
U")
4A
03
01
U3
E.
01bo
>-,
0
8.3
List of benthos stations
GKGl
GKG2
GKG3
GKG4
MUC
EBS
AGT
BWS
GKGl
GKG2
GKG3
FLOORI
MUC
EBS
soft rnud with forams
failure
soft mud, some tubes
soft mud, tubes, forams
fine rnud no stones light brown
fine rnud with
many amphipods, shrimps
fine rnud with much
fish and many shrimps
40 cm sample is missing
fine mud, forams, cumaceans,
spnges
fine mud, forams, amphipods
fine mud, 1decapod,
1 amphipod 2 spnges, many
forams
fine mud, first deployment at
all
light brown rnud rare
macrofauna
fine sediment, many
peracarids
FLOORI
soft rnud
GKG 1
GKG2
GKG3
MUC
FLOORI
BWS
EBS
fine mud, some tubes, forams
some tubes, forams
fine mud, holes from bivalves
fine rnud
successful
successfu1
peracarids, decapods, etc.
AGT
many actinians, brittle stars,
some fish, decapods
BWS
GKG1
GKG2
GKG3
GKG4
MUC
EBS
successful
failure
soft sediment
some polychaete tubes
failure - stone damaged box
sandy sed., short cores
many crinoids, octopus,
shrimps, many peracarids,
fish
many Heliomefra,
polychaetes
AGT
EBS
many pantopods, crustaceans,
polychaetes
EBS
crustaceans, ophiuroids, ray,
polychaetes
BWS
GKG1
successful
very coarse sediment, surface
slightly damaged
small samples, very coarse sed.
very coarse, much sand, stones
stony sed., short cores
no cores but in-situ profiles
failure, sledge was upside
down; coarse sed. with forarns
GKG2
GKG3
MUC
FLOORI
EBS
GKG1
GKG2
GKG3
MUC
MUC
BWS
EBS
hard, corase sed., - megafauna
high sand content
high sand content
failure
second trial instead FLOORI
successful
many forams, sponge spicules
peracarids, polychaetes
BWS
GKG1
GKG2
GKG3
MUC
MUC
successful
big tubes, sponge, forarns
many cumacea, 1 hydrozoa
cumacea, forams, fine rnud
fine mud, rare rnacrofauna
GKG1
GKG2
GKG3
MUC
MUC
EBS
fine mud, many forams
failure
fine mud, rnany forams
failure, no sediment
fine, sandy mud, many forams
failure, sledge damaged
BWS
FLOORI
successful
in-situ profiles
GKG1
GKG2
GKG3
GKG4
GKG5
MUC
MUC
MUC
MUC
hard sediment, many stones
-"-polychaetes, bivalves
failure, empty box
failure, empty box
hard sediment, forams
hard sediment, many stones
failure, no sediment
failure, no sediment
hard sediment
37-027 12.10.95
75'00.45'N
75'00.50'N
74O58.34.N
74'58.49'N
12'38.57'W,
12'39.32 W,
12'56,45'W,
12'57.31 W,
745 m 745 m
424 m 401 m
AGT
many sponges (Geodia)
EBS
sporiges, crustaceans
37-030 14.10.95
74O59.52'N 12'46.15W, 568 m
FLOORI
many rnatted sponge needles
37-032 14.10.95
75O00.10'N 12'54.59W, 390 m
75O00.18'N 1Z054.57W, 390m 75'00.22-N 12'55.48W, 371 m
BWS
AGT
failure, control unit broke down
many big stones,gorgonocephali
37-053 17.10.95
75O00.ll'N 04'07.83'W, 3587 m
FLOORI
failure
37-062 19.10.95
75O00.06'N 00°21.65'E3727m
FLOORI
failure (blocked by big stone?)
9.
Date
STATION
LIST
Station Time
Latitude
75'43'N
75'43'N
78O58'N
78'57'N 78O59'N
78O54'N
78'59'N
78'58'N
79'00'N
78'59'N
78'59'N
78'51 'N
79'00'N
78'58'N
78O59'N
7g056'N
78'56'N
78'56'N
78'59'N
7g058'N
79'00'N
79'00'N
79O00'N
78O52'N
78O59'N
78'58'N
79O06'N
79'03'N
80°11'
80°10'
80°23'
80°23'
80°30'
80°23'
80°03'
79O58'N
79O37'N
79O33'N
79O02'N
79'02'N
74'53'N
74'53'N
74'57'N
74O57'N
74O56'N
74'55'N
74O58'N
75'00'N
1
Longitude Equipment employed
'.
$
10°12' 1
i3
03'2O'W 1 Mooring FWA-1/95 deployed
03'22'W 5
04O00'W i CTD, PLA, MN, SD
i
04OO5'W
05'09'W 1 CTD, PLN, BO, MN, HN, GKG, EBW, A G T , ~
05'1 1 'W MUC
04'41 'W 1 Mooring FWA-2 /94 recovered
1
04'41 'W
04O41'W 1 Moorine FWA-2/95 deployed
l
~
1
-
1
1
1
V
A
P
04'45'W
04'47'W
P
J
1
 CTD, BO, M N
1
1
P
P
P
0 9 0 4 9 ' w L
09O21'W S EBS,CTD, BO, M N
P
P
P
13Oll'W
12'59'W
12'42'W
-
1
.
.
Mooring AWI/411-2 recovered, AWI/410-2
, recovered, HELIPOD
026
cont.
028
029
EBS, CTD
CTD
CTD
030
031
TMS, Jojo, BO, HELIPOD
032
BWS, AGT
033
CTD
034
Mooring AWI/412-4 recovered
035
FLO, CTD
036
CTD
037
CTD
038
CTD
P
039
040
041
-042
043
CTD
CTD
CTD
P
-
CTD
V
P
=
044
045
W
.
-
046
P
.
047
CTD
CTD
CTD
C
T
---U.
048
P
049
050
CTD
051
Mooring OG-10 deployed
052
Jojo, CTD
D
~
1 7 . 5 4 175OOO'N 1 11°56'
19.16 75'00'N
12'36'E
20.29 75O00'N
12'34'E
22.10.
086 06.14 75'00'N
13'15'E
07.24 75'00'N
13'15'E
2.10.
087 108.49 175OOO'N 13O52'E
l
j 13.30 175OOl'N j 13O49'E
22.10.
088
14.50 75'00'N
14031rE
15.39 75'00'N
14'31 'E
21.10.
1
L4.10.
1
085
CTD
CTD
CTD, MN, B 0
1
CTD
23.13 73'20'N
16'59'E
103 100.29 173OlO'N 117OOO'E
CTD
j_____fO0.48 ~ 7 3 Â ° 1 0 ' ~ 1 7 0 0 1 r
1
1
-
17'00'E
CTD
17'00'E
8 CTD
17'00'E
17O01'E
17O0 1 'E
17O00'E
17'00'E
17'01'E
17O00'E
17OOO'E
..
17O00'E
1
CTD
-
1
1 CTD
1
CTD
CTD
i
Abrahamsson, Katarina
Albers. Carola
Auel, Holger
Berg, JörStefan
BöhmJoachim
Brandt, Angelika
Budkus, Gereon
Cisewski, Boris
Cohrs, Wolfgang
Darnall, Clark
Donner, Gabriele
Ekdahl, Anja
Erdmann, Hilger
Gedamke, Michael
Gradinger, Rolf
Haupt, Olaf
Hofmann, Michael
Hollmann, Beate
IkävalkoEira Johanna
Jensen, Stefan
Kaleschke, Lars
KöhlerHerbert
Krause, Gunther
Krumbhoiz, Marita
Lahrmann, Uwe
Lunau, Angela
Martin, Thomas
Mock, Thomas
Monk, JŸrge
Niehoff, Barbara
Plugge, Rainer
Riewesell, Christian
Ronski, Stephanie
Sackmann, Volker
Sauter, Eberhard
Scheltz, Annette
Schnack, Klaus
Schreiber, Detlev
Schürmann
Mathias
Strohscher, Birgit
Stürcken-Rodewald
Marthi
Takizawa, Takatoshi
Ufermann, Susanne
Wamser, Christian
Wanner, Susanne
Wehde, Henning
Werner, Iris
Wode, Christian
Woodgate, Rebecca
Zhang, Qing
AMK
AWI
Ir0
SFB 313
HSW
IPO
AWI
AWI
AWI
APL
SFB 313
AMK
DWD
SFB 313
IPO
SFB 313
IMK
AWI
UNI HELSINKI
SFB 313
AWI
DWD
AWI
SFB 313
HSW
GEOMAR
AWI
SFB
AWI
AWI
AWI
HSW
AWI
AWI
SFB 313
SFB 313
SFB 313
HSW
Aerodata
AWI
AWI
JAMSTEC
AWI
AWI
GEOMAR
AWI
IPO - SFB 313
Ih4K
AWI
PO
11
SHIP'SCREW
Captain
C. Allers
1. Officer
2. Officer
2. Officer
2. Officer
H. Pförtne
Doctor
Dr. Thoepser
Chief Engineer
Ist Engineer
2nd Engineer
2nd Engineer
D. Knoop
G. Erreth
H. Schneider
0.Ziemann
Electrician
Electron Engineer
Electron Engineer
Electron Engineer
Electron Engineer
G. Schuster
U. Lembke
H. Muhle
J. Roschinsky
Radio Officer
Radio Officer
A. Hecht
W. Kriemann
M. Rodewald
U. Grundmann
T. Hebekus
A. Greitemann-Hack1
E. Arias Iglesias
M. Ipsen
U. Husung
E. Heurich
G. Dufner
Carpenter
Store keeper
A. Brunotte
K. Mülle
Boatswain
Seaman
Seaman
Seaman
Seaman
Seaman
Seaman
Seaman
Seaman
R. Zulauf
B. Iglesias Bermudez
J. Soage Curra
S. Pousada Martinez
L. Gil Iglesias
E. Arias Iglesias
K. Bindernagel
M. Winkler
H. Voges
Cook
Cook Mate
Cook Mate
H. Schuster
1. Steward
Stewardess/Nurse
Steward/ess
Steward/ess
Steward/ess
2. Steward
2. Steward
Laundry Man
H. Vollmeyer
S. Hoffmann
NN
E. Golose
C. L. Wu
J. M. Tu
K. F. Mui
K. Yu
H. Hünek
G. Rickert
AWI
Alfred-Wegener-Institut fü
Polar- und Meeresforschung
Columbusstraß
27568 Bremerhaven
Aerodata
Aerodata
FlugmeßtechniGmbH
Rebenring 33
38106 Braunschweig
DWD
Deutscher Wetterdienst Hamburg
Seewetteramt
Bernhard-Nocht-Straß 76
20359 Hamburg
GEOMAR
GEOMAR
Forschungszentrum fümarine
Geowissenschaften
Universitä Kiel
Wischhofstraß 1-3
24148 Kiel
Helicopter-Service
Wasserthal GmbH
Kätnerwe 43
22393 Hamburg
IfMHH
Institut füMeereskunde
Universitat Hamburg
Troplowitzstraß7
22529 Hamburg
IMK
Institut füMeteorologie
und Klimatologie
Universitat Hannover
HerrenhäuseStraß2
30419 Hannover
Institut füPolarökologi
Universitä Kiel
Wischhofstraf3e 1-3, Gebäud12
24184 Kiel
SFB 313
Universitä Kiel
Sonderforschungsbereich 313
Olshausenstraß40
24118 Kiel
UNI
University of Helsinki
Hydrobiol. Laboratory
P.O. Box 4
FIN-00014 Helsinki
J AMSTEC
Japan Marine Science and Technology Center
JAMSTEC
Headquarters
2-15 Natsushima-Cho
YOKOSUKA 237 JAPAN
Norwegian Polar Institute
Dept. of Analyt. and Marine Chemistry
Postboks 5072, Majorstua
N-0301 Os10
APL
Polar Science Center
Applied Physics Laboratory
University of Washington HN-10
Seattle, WA 98195
AMK
Chalmers University of Technology
and University of Götebor
Analytical and Marine Chemistry
S-412 96 Götebor
Second Institute of Oceanography
State Oceanic Administration
P.O.Box 1207
Hangzhou, Zhejiang, 310012
13.
Moorings serviced during "Polarstern" cruise ARK XI12
Latitude
Idegrees
Longitude
Idegrees
AWI 410-2
74 57.7N
12 5 8 . W
AWI 411-2
74 59.8N
12 31.9W
AWI 412-4
74 57.5N
11 36.9W
Name
Depth /m
(corrluncorr)
Instruments
RECOVERED
Fahrbach, AW1
10 37.1W
AWI 414-4
74 52.6N
7 45.6W
2 Current Meters
1 Sediment Trap
1 ULS
3 Current Meters
1 ULS
4 Current Meters
1 ULS
4 Current Meters
3 Sediment Traps
1Transmissometer
1 ULS
4 Current Meters
1uLs
Meincke, IfM HH
MI-94
79 0.2N
6 1.6W
GSM-05
75 2.3N
2 54.9W
78 59.3N
4 40.W
3 Current Meters
2 Seacats
1ULS
74 52.9N
3 56.9W
2 Sediment Traps
78 57.1N
3 22.3W
2 Current Meters
1Seacat
1ULS
4 40.6W
2 Current Meters
1Seacat
1ULS
435.m
3 Current Meters
3 Sediment Traps
2 Current Meters
1ULS
1 Current Meter
5 Seacats
1 Thermistor Chain
1ADCP
Aagaard, APL
FWA-2 '94
SFB, Kiel
OG-9
DEPLOYED
Aagaard, APL
FWA-1 '95
SFB, Kiel
OG-10
75 3.4N
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