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Earth Institute News

posted 11/12/04

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Reports From the Field

The Anslope Expedition: Cruising the Antarctic

November 5, 2004, 1:50a.m. local time
Dr. Gerd Krahmann aboard the R/V Nathaniel B. Palmer...

This is the second report from the field from this year's ANSLOPE cruise, with Gerd Krahmann reporting from on board the R/V Nathaniel B. Palmer. Nearly two weeks ago it left Lyttelton, New Zealand to steam towards Antarctica.

Two crabeater seals aren't sure what to make of that big orange-yellow thing (our ship) passing by their resting place on bigger ice floe. Photo by Gerd Krahmann

52 S 13.1
167 E 56.5
0% ice cover
air temperature 6°C
sea surface temperature 7.7°C
35kn winds from the south

Three days ago we left our first working area near the Mertz Glacier Tongue. Since then we have again been steaming across the Southern Ocean. Luckily it showed its calmer side. Within the next two days we should reach the small harbor town Timaru in New Zealand for our refueling stop. It will be nice to walk on solid ground and go shopping or spend an evening in a restaurant or in a pub. Unfortunately the stop will be not longer than 24 hours. After that we will head to our original work area in the northwestern corner of the Ross Sea. Satellite images still show a nearly 100% ice cover in that region. Before we get there we will again cross the Southern Ocean for 5-6 days and then will have to break ice for about four days until we reach the area.

In the Mertz region we did 79 CTD stations measuring temperature, salinity, and oxygen content from the sea surface to the sea floor and taking water samples from various depths to analyze them for different trace gases. The concentration of these gases will give us some information on where the water orginally came from, when it was last in contact with the surface, and how much of it is melt water from Antarctic glaciers. On two station we used a new instrument, the Vertical Microstructure Profiler (VMP also dubbed 'VaMPire') to measure the location and strength of mixing within the water column.

Basil Stanton and Annie Coward (left) are facing the furies of the Southern Ocean on one of the calmer days to deploy and Expendable Bathythermograph (XBT) probe that measures water temperature down to 760m from a moving ship. Photo by Gerd Krahmann

Another group of scientists on board are monitoring the wildlife encountered during the cruise. Sarah Dolman, WDCS (Whale and Dolphin Conservation Society) and Kelly Asmus, Deakin University in Australia, are conducting visual surveys and opportunistic photo-identification from the ship's bridge throughout the voyage. The primary objective of the cetacean survey is to determine patterns between the sea-ice habitat and whale densities. This involves characterising the foraging behaviour and movements of the whales encountered (A number of species would be expected in the sea ice areas, particularly minke and killer whales) in relation to prey and the physical environment. Factors affecting whale densities appear to include such measures as sea ice concentration, complexity and extent. Therefore extensive sea ice data, as well as whale observations, is being recorded continuously where sea ice is encountered. The survey also includes passive acoustic whale observations through the deployment of sonobuoys. (listen to sonar recording of unidentified seal or whale) It will be possible to record some calls of animals that may not be seen during the visual survey work (because they are diving or beyond the visual range of the ship). The combination of visual, acoustic and sea ice data will assist in the ongoing investigation into the presence of cetaceans in this incredible region of the Antarctic and the particular value of certain habitat types as favourable feeding grounds for many cetacean species. There have been 31 whale observations, of 62 animals, so far during the voyage and over 500 hours of acoustic recordings have been made. Although almost exclusively minke whales were encountered in the ice, sightings include a probable Gray's beaked whale. Twenty sightings of crabeater seals were recorded on our way out of the ice, the majority of which were female and pup pairs, many with a male escort Seabird observations are also being made along the ship's track, with the highest Emperor and Adelie penguin densities over or near the continental slope, as expected from earlier work.