position map04/22/04

Mary Tobin

Reports from the Field

The Antarctic CORC/ARCHES Expedition, April 16 through May 10, 2004

First Report -- April 19, 2004

RV L.M. Gould
The RV L.M.Gould is cruising through the exceptionally calm seas of Drake Passage towards our working area south of the South Orkneys.
Ice covering the Weddell Sea last year prevented scientists from reaching submerged mooring instruments busy collecting data, so Dr. Gerd Krahmann of the Lamont-Doherty Earth Observatory is again aboard the Research Vessel Laurence M. Gould heading to the Antarctic's Weddell Sea. Krahmann is leading a group of five scientists and technicians from Lamont (Dr. Robin Robertson, Dr. Deborah LeBel, Tim Newberger, and Anthony Dachille) on an expedition to replace moored instruments deployed on the northern rim of the Weddell Sea.These three moorings have been observing the strength and properties of the outflow of Weddell Sea bottom water for the past four years. The instruments need to be recovered every one to two years to exchange batteries and download the data. Another group of Lamont Scientists is concurrently investigating the processes involved in the formation of deep water in the Antartic's Ross Sea (The Antarctic AnSlope expedition).

Because it is very cold and salty, Weddell Sea bottom water is one of the densest water masses in the world's oceans. As such, it and similar dense water masses formed in other locations around Antarctica spread throughout the deep part of the world's oceans. The goal of the project, dubbed CORC/ARCHES, is to observe changes of the properties and strength of the outflow of Weddell Sea bottom water over a period of ten years. Since the Weddell Sea is a major source of deep water, changes in the outflowing waters formed there will in turn affect the global circulation of deep water.

Dr. Gerd Krahmann, of the Lamont-Doherty Earth Observatory
aboard the R/V L.M. Gould, Weddell Sea, Antarctica...

Latitude: 58S 40.2
Longitude: 53W 46.3
Sky: overcast
Wave height: 1m (3')
Air temperature: -2C (28F)
Wind Speed: 14kn (15mph)

We have left Punta Arenas three days ago and are now in the middle of Drake Passage, known to have some of the roughest oceanic conditions in the world. During a storm, waves have been reported to reach heights of more than 20m (60'). But so far it has been extremely calm. Maybe it's because I tried for the first time sea sickness medication and Neptune (the Roman god of the seas) wants to make me believe that I could do without it. I am sure that as soon as I remove the small patch behind my ear, the seas will roughen and I will have to give my dues to Neptune.

In about two days, we will reach our working area and will see how the ice conditions are. So far we have seen only satellite images of the area, which indicate that the places we want to reach are partially ice-covered. Unfortunately the satellites we use for the detailed ice images cannot see through the clouds. The last image we have is from April 10 and since then it has been overcast.

This expedition is a repeat of one we did last year (see past CORC/ARCHES Reports From the Field, 2003) and in which we were not able to accomplish our goals as the ice prevented us from getting to the places we needed to go. This year we might run into the same trouble, as we again only got a late fall slot on the very busy ship schedule. Late fall is the time of year when the sea ice surrounding Antarctica is growing again. Everybody reading this report, please cross your fingers for us.

Unlike last years expedition, we are not stopping over at Palmer Station on the western side of the Antarctic Peninsula. We are heading directly from Punta Arenas in Chile to our work area south of the South Orkney Islands. There we will spend our three day allotment of ship time for scientific work.

During this cruise, we are sharing the ship with another group of scientists who are interested in the geology of an area east of the Antarctic Peninsula. This place was previously covered by the Larsen ice shelf that broke up a few years ago (you might have heard of it in the news). An ice shelf is an extension of a huge glacier slowly flowing into the ocean. Ice shelves typically are several 100' thick. Now that this ice shelf is gone, ships are able to reach places that before were covered and where nobody has ventured before.


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