Brian Powell

It's been quite a delay since my last posting; however, that was due to a lack of change to our schedule. We have been continuing our drifting/sampling sessions and I didn't have much to report. On Tues., that all changed. We saw an iceberg field on the radar and decided to sample the upstream and downstream influences of the iceberg fresh water melt on the mixed layer. So, we steamed to the largest iceberg and pulled up as close as we could to it on several sides, performing a survey at each stop. The iceberg (at least what was above the water) was roughly 60m high (~17 stories) and probably 300m wide. It had a large "lagoon" where a portion of the middle had calved away previously. It was absolutely amazing to be about 100m from such a large iceberg. While the instruments were sampling, we would run about the decks taking pictures of the iceberg. The fresh water influence (since the water is relatively warm--about 0.08 to 0.1 degrees away from freezing--it melts the iceberg from the bottom which introduces a large amount of fresh water) was very prevalent with a sharp drop in the mixed layer depth downstream from the iceberg. Although this iceberg was very stable (due to the ratio of its width to height), it is common for icebergs down here to "flip" when the bottom has melted away enough such that the bottom buoyancy can no longer support the part of the structure that is above the water. Anyhow, we decided to do some research of opportunity and it turned out very well. We will be finishing up our science mission this upcoming Monday (Sept. 5) and begin our long trek home. We have put ourselves a long way from any place (we are about equal distance to Punta Arenas, Chile or Capetown, South Africa). We have also been given (and accepted) an invitation from the British research station at Grytviken, South Georgia Island. There are 4 people who work at this station during the winter so we will go into the harbor there and spend a day visiting and hiking on Sept. 12. That will be a nice little diversion on the way home. It is a very large breeding ground for seals and penguins. We are scheduled to return to Punta Arenas, Chile on the morning of Sept. 18 and then I'll be heading home a day or two after that.

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