| Third
Report -- May 1, 2004
 |
A
scene reminiscent of Christmas. Scientists are
opening the side panel of the Kasten core and
discover, for the first time, the geological
treasures the instrument has brought to the surface.
Image credit: Gerd Krahmann |
Dr.
Gerd Krahmann, of the Lamont-Doherty Earth Observatory
aboard the R/V L.M. Gould, Weddell Sea, Antarctica...
Afternoon, May 1, 2004
Latitude: 63S 6.5'
Longitude: 55W 8.6'
Sky: overcast
Wave height: 0.0m (in sea ice)
Air temperature: -5C (23F)
Wind Speed: 11kn (12mph)
A week ago, the other group on board
(geologists under chief scientist Eugene Domack) took
over the scientific responsibility. Their primary objective
was to reach the area of the former Larsen ice shelf
on the eastern side of the Antarctic Peninsula. This
ice shelf (basically a massive glacier flowing into
the ocean and covering a large area of the sea) broke
up a few years ago and now, for the first time, allows
ships to reach a region formerly covered by ice.
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| This
jar contains the species collected from a Smith/MacIntyre
grab. It includes a brittle star and several
worms. All these species live at a water depth
of more than 700m (2100') without light and at
temperatures near the freezing point. |
As for our group, the late scheduling
of our cruise (April-May here is late fall with rapid
freezing of the open ocean) meant that Domack needed
a lot of luck to encounter favorable ice conditions.
Satellite images supplied by personnel at Palmer Station
(western side of the Antarctic Peninsula, see our reports
from last year) indicated that the direct route to the
former ice shelf region was already blocked by ice. We
thus tried two passages between islands. We quickly had
to give up on the first passage as winds had pushed ice
floes on top of each other, building ridges up to 10'
thick. Our ship can handle, at most, 5' thick ridges
and 1' continuous ice.
The second passage we tried,
the Prince Gustav Channel, was covered by a mixture
of newly formed ice and smaller ridges. We were able
to proceed to a location close to the Larsen ice
shelf—only to find that the mouth of the passage
was blocked by large icebergs and very heavy ridges.
After some scientific work in the deep part of the
channel, we had to abandon our attempts to reach
the Larsen ice shelf. Retracing our route through
the Prince Gustav Channel, we headed southward towards
another region of scientific interest.
During the night strong winds
created new ridges in the ice and the ship was actually
not able to move for several hours. The captain used
a moment of weaker winds to break free and we headed
north towards more open waters. Had the winds not
calmed down a little, we would have run the danger
of being stuck in the ice for the whole southern
winter. Conditions on the following day worsened
by the hour and peaked at wind speeds of 94kn (103mph).
The air temperatures had dropped to less than -20C
(-5F) and water from the increasing waves froze instantaneously
on deck. This freezing of seawater on the superstructure
of a ship is extremely dangerous as it can cause
the ship to be so top heavy that it can capsize within
a moment. The decks were closed for us scientists
and only crewmembers were allowed outside to break
away our several inch thick ice crust. Luckily the
bad weather lasted for only a day and we proceeded
to another region northeast of the Antarctic Peninsula.
We arrived there yesterday
and have now begun geological work. After a first
survey of the water depths, Domack's group had identified
a number of deep locations in which sediments could
accumulate. Today we did the first so-called Kasten
core. The coring system consists of a square-diameter
hollow steel tube that is lowered to the seafloor.
Heavy weights on its top push this 3m (10') long
tube deep into the mud. After it is sunk into the
mud the tube is hauled back on board and taken into
the labs. A side panel on the tube can be removed
and allows the geologists to analyze the various
layers of sediment. The chief scientist estimates
the age of the deepest layers of the core at a few
thousand years.
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