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Week 2

(click on map to enlarge)

2/20
17:14 GMT
64 25.9 S
61 15.0 W
1.4 C
7 knot winds
overcast
calm seas with few floating icebergs nearby

On the map, the red line roughly marks our course over the past few days. We entered the bay formerly occupied by the Larsen B from the north, rounding Robertson Island and sailing roughly NW towards the Oscar II coastline. Turning SW, we followed the coastline as we passed Exasperation Inlet and Cape Disappointment (labeled CD) on the chart. Just South of Cape Disappointment, we began our run along the last remaining portion of the Larsen B, which still exists in SCAR Inlet.

A rough estimate of the ice shelf front height comes in around 70 feet from the waterline. It varies along the front, but is very impressive even from the quarter mile distance we maintained from the front. Rounding the Jason Peninsula, we continued south to almost 66 30', the Antarctic Circle, until our way was blocked by a large tabular iceberg that has broken away from the Larsen C iceshelf. This iceberg can be seen on the NOAA -16 "visible" satellite image of 19 Feb 2005 19 UT. We placed a sediment trap mooring at this point and returned north to continue our survey of the Larsen B area.

Late yesterday evening, we collected our first Kasten core of the trip, collecting just over a meter of marine sediment. Analysis of the sediment is ongoing at this time, but all on board are very excited about our initial success. After this station, we continued through the night mapping the seafloor topography and arrived on location for our next station early this afternoon off Exasperation Inlet. Currently, multiple operations are underway at this station.

Late afternoon sunlight illuminates the Bruce Plateau with the current edge of the Larsen B iceshelf in the forground. The high snows of the Bruce Plateau are thought to be the source area for the valley glaciers that feed the Larsen B iceshelf.

2/20
22:06 GMT
65 18.116 S
61 08.867 W
-.9 C
17 knot winds
cloudy with low clouds on the mountains
smooth seas with increasing local iceberg concentrations

After a successful station, we are now gridding an area to define the extents of a few features we are seeing as we profile the bottom topography.

At most stations, we deploy a number of instruments to characterize the water and sediment at the station.  First we deploy a CTD, which measures Conductivity as a proxy for salinity, Temperature and Depth. This instrument is attached to a frame holding an array of 30 liter Nisken bottles. The instrument is lowered to the bottom, and, as it is lowered, signals from the sensors display on a computer screen changes in conductivity, temperature and the depth. Once on the bottom the instrument is slowly raised and paused at various areas of interest in the water column. A signal sent from the ship closes specified Nisken bottles allowing samples to be collected at various stages in the water column. Once the CTD is back on board, researchers collect samples from the various bottles for analysis.

Kasten core
on deck

Next over the side are a grab sampler and a photographic camera system. The grab sampler collects a small sample of the seafloor and allows us to decide if a coring attempt is justified. Each of these instruments is sent down individually.  In the water depths we are working, around 700 meters, the round trip time for each deployment is just under an hour.

The Kasten core is our main tool to sample the ocean floor. It is a 3 meter square aluminum tube with a reinforced cutter nose on one end and over 800 lbs of lead weights on the other. Lowered on a steel cable it impacts the seafloor at about 10 meter per minute. Depending on the character of the sediment it may penetrate a short distance, or its entire length. Tension on the winch cable as we pull it out of the seafloor gives an early indication of how deeply it penetrated the sediment. In the area we are working, sediments appear to be rather thin and overlie a highly compacted glacial till which collects in the cutter nose.

Dr. Eugene Domack explains the significance of sediments collected in the first Kasten core of the cruise to (from left to right): Aron Buffen (orange coat), Gemma Kirkwood, Emily Constantine (former Colgate student and now Marine Tech on the Gould), Stephanie Dulgar, Rachel Perez and Heather Tompkins.

Northwestern edge of
Larsen B ice shelf

2/21/05
22:32 GMT
65 05 S
61 18 W
0.3 C
5 knot winds
clear blue sky
open smooth water

We are stationed near the northwestern edge of the Larsen B area near the Hektoria glacier. It has been a spectacular day with amazing scenery.

Our sea floor mapping software is working well, and we are beginning to fill in the details of the sea floor topography.

This is an exciting station, as bottom profiling shows a set of deep layered sediments draped over a hard substrate. This is the first example we have seen of significant sediment accumulation. We are currently running our array of instruments: CTD, grab sampler, Benthos still camera, Kasten core, and possibly others depending on the results of the Kasten core.

Looks like a long evening ahead processing cores and deploying equipment. Should be a spectacular sunset for the day shift and sunrise for the night shift.

-commentary provided by Dave Tewksbury, geology technician at Hamilton College

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