2001 Antarctic Expedition
The Foraging Biology of Weddell Seals
Notes
from the Field
(from Terrie M. Williams, Ph.D.)
Building a research camp on the sea ice
in Antarctica. This structure will be used as our field laboratory. (Photo
by R.W. Davis)
WEEK 2 – SETTING UP CAMP
On
the Ice
Our
first task once arriving in the Antarctic is to establish a field camp.
To conduct our research we need to be near Weddell seals as they
dive and hunt for fish. At the same time a camp must provide shelter and
warmth for the scientists that will be studying the seals for the next two
months. We decide to
place the camp on the frozen sea that surrounds Ross Island.
In this location the camp is on a solid surface while the seals can
dive in water that is 100 meters to 500 meters deep below us.
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This satellite image
shows the major American research stations in Antarctica.
We are based near McMurdo Station which is on Ross Island
(see inset). Our camp
will be on the sea ice of McMurdo Sound adjoining the Ross Sea
located next to Ross Island. Note
how close we are to the South Pole. (NSF photo) |
We spend the first four days in Antarctica surveying the area for evidence of seals and cracks in the ice. We want our camp to be near an open crack that will allow the seals to haul out on top of the ice. However, if the ice has too many cracks or is too thin it won’t be strong enough to support the weight of our camp. To find just the right field site we drive over large expanses of the frozen McMurdo Sound in a track vehicle called a Spryte. Periodically we stop and drill into the ice to measure how thick it is.
Traveling in the Spryte and checking the thickness of the ice. The man in the photo on the
right is holding an ice auger used for drilling.
The auger is over nine feet long – which gives
you an idea of how thick the ice is! (Photos by R.W. Davis)
Our first challenge. As
we conduct our surveys we discover that many of the ice cracks and the Weddell
seals are not in the same places that we have found them in previous
years. In fact, many of
the seals seem to be missing. Members
of our research team talk to several ice biologists in McMurdo Station and
are told that a large iceberg (about the size of Rhode Island) has ground
next to Ross Island. The
iceberg is named B-15 and has blocked the movement of the winter ice away
from Ross Island. As a
result, the ice edge this year is approximately 80 miles from McMurdo
Station (shown in blue). In
normal years the ice edge is only 30 miles from the Station (shown in
red).
This satellite map shows the iceberg B-15 smashed next to Ross Island. The light gray area surrounding Ross Island is solid sea ice that has been blocked in by the iceberg. Darker gray regions in the upper right hand corner of the picture are areas of open ocean where seals, whales and penguins can swim freely. (NSF photo)
With so much ice between Ross Island and the open ocean, it is difficult for Weddell seals to swim to their usual haul out sites near McMurdo Station. We estimate that the seals can only swim 2 miles before they would have to surface to breathe.
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Weddell
seals usually follow cracks and holes in the sea ice as they swim
around Ross Island. Whenever
they need to breathe they pop their heads up through the holes and
take a breath of air. This
year, B-15 the iceberg has smashed the sea ice tightly together and
prevented the seals’ breathing holes and cracks from forming.
(Photo left: T.M. Williams, Photo above: R.W. Davis)
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The research team must now rethink where we will place our camp. Should our camp be built in a location that usually has lots of seals in the hopes that a big crack will open up later and seals will eventually arrive during the next few months? Or should we go to a new location where we have found that a few seals have already hauled out?
The team decides to try the new location with seals already there.
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Camp construction begins by drilling a large 4-foot diameter
hole through the ice. A
giant ice auger is driven to our camp site and used to drill through
7 feet of ice. The hole
is just big enough for a Weddell seal to squeeze through and will be
used by the seals in our experiments over the next few months.
(Photo by T.M. Williams) |
Our
camp is constructed around the ice hole that has been drilled for the
seals. It
will be a
combination field laboratory, sleeping dormitory, and kitchen.
There are four buildings in our campsite: 1) the laboratory-kitchen-men's
dormitory, 2) the women's hut, 3) a magnetometer hut for calibrating
instrumentation, and last but not least 4) the outhouse.
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T-Rex the mobile crane lifts an electric generator into place while Dave Ayre, the electrician, helps with the camp wiring for the computers. A team of carpenters work in the cold to build our laboratory on ice.
The sea ice camp for our Antarctic research project is named "Weddell World".
X
marks the spot where our camp is located at the foot of the Erebus Ice
Tongue, a large glacier that is in our back yard.
Weddell seals haul out on
the ice just around the corner.
It is easy to see that we are on a frozen ocean
when you realize
that the large brown rocks in this picture are Tent Island,
Inaccessible
Island, and Big Razorback Island. (Photo by R.W. Davis)
At last we are ready to begin working with the Weddell seals and start our experiments.
Next week - The Weddell Seal
You
can write to members of our Research Team at williams@biology.ucsc.edu