May 24 2008
May 24 2008
Bye-bye Icebergs!
One of Dann Blackwood’s stunning photos of icebergs from the beginning of our trip back in Iceberg Alley, Scotia Sea.
Beautiful skies on the way home.
Snow caped mountains of Argentina could be seen throughout most of the day today.
We are approaching the end of our wonderful cruise. We had our last dredge yesterday night, we packed the last corals today, and we will have the last full day at sea tomorrow. While it is time to say good-bye to many things, there is one thing we said good-bye to a while ago – icebergs. If you followed our track on this website you may be surprised reading this, as we were still at 60ºS until yesterday afternoon, and spend most of the last two weeks close to the Antarctic Peninsula and in the Drake Passage. However, we have not seen icebergs for more than two weeks - the time when we left the Scotia Sea.
The reason for this is that the occurrence of icebergs around Antarctica is not only governed by the fact where Antarctic ice shelves or outlet glaciers calve them off, but even more importantly, what the ocean currents do. Once an iceberg is released to the ocean it travels to wherever the prevailing current takes it to, until it finally disappears. Melting happens at the bottom and at the surface of an iceberg, and gets accelerated by break down into smaller pieces. The majority of icebergs around Antarctica never leave the proximity of the continent, as a westward flowing current around the continents make them stay close. This current is predominantly driven by wind blowing off the ice sheet (from south to north), which is directed to the west by means of the Coriolis Force. However, there are a few places where the icebergs can break out of these currents and travel further north. One of these places is the Weddell Sea, where a large oceanic gyre picks up the bergs from the ice shelf and the Antarctic Peninsula and carries them up into the South Atlantic, and more precisely into the Scotia Sea. Since the current is strong, and many icebergs are produced in the area, the track of the icebergs from Antarctic into the Scotia Sea is often referred to as “iceberg alley”.
All the wonderful photographs taken by Dann Blackwood, our photographer on board, document the beauty of icebergs, and their manifold shapes and colors. For me one highlight of the cruise will always be the sighting of the first iceberg. As some people say “you never forget your first berg”. I said bye-bye to the bergs, when we left iceberg alley, and hope that I get a chance to see them again soon. In the meantime, I will go back to the lab to follow up on my studies of Antarctic iceberg provenance. Icebergs do not only look pretty, but the debris they contain and release upon melting also tells us about where in Antarctica they were produced. Today this pattern can be matched with satellite observations, and this is where the above described patterns of iceberg distributions are coming from. For the past however, the areas of iceberg production can tell us about which parts of Antarctica were glaciated, for example in warmer climates. This is important to know, as it may help us understanding the dynamics of the Antarctic ice sheet under warmer conditions – conditions we may face in the near future.
Tina van de Flierdt signing off
Snow caped mountains of Argentina could be seen throughout most of the day today.
These hourglass dolphins (or 'sea skunks') played around the ship this morning for several minutes.
A sighting of the Lawrence M. Gould, the other US Antarctic Program ship following us through the Straits of La Maire.
Meanwhile in the lab the last of the sample packing is still ongoing.