LARISSA - LARsen Ice Shelf System, Antarctica, a NSF-funded project.

LARISSA - LARsen Ice Shelf System, Antarctica, a NSF-funded project.
We are conducting an integrated, multi-disciplinary field program to address the rapid and fundamental changes occurring in the Antarctic Peninsula region as a consequence of the abrupt collapse of the Larsen B Ice Shelf in the fall of 2002. A profound transformation in ecosystem structure and function is occurring in coastal waters of the western Weddell Sea. This transformation appears to be yielding a redistribution of energy flow between chemoautotrophic and photosynthetic production, and to be causing the rapid demise of the extraordinary seep ecosystem discovered beneath the ice shelf, providing an ideal opportunity to test fundamental paradigms in ecosystem evolution.

Monday, March 1, 2010

Hill Island

30 Jan – 2 Feb We are now a halted in the sea ice a few miles west of
 Snow Hill Island, unable to break our way any close than 60 miles to the 
entrance of the Larsen B region, around the tip of Robertson Island
 (map below). Quite appropriately, we can see Cape Longing in the 
distance, reflecting our desire to get further south into our primary study
area. Our satellite images of sea ice indicate that the leads are closing
in the Larsen B area, reducing the changes of getting there. We are within 
helicopter range of several or our terrestrial sites for GPS stations that 
will evaluate the rebound, or rise, of land masses as a result of the
 breakup of the Larsen B shelf; a vast weight of ice has been lifted from
the the coast in this region, and the Antarctic peninsula is likely to be
rising at a few millimeters a year as a consequence. Thus, the terrestrial
 components of our program may not be set back too heavily from lack of ship 
access to the Larsen B region.

Map of East Antarctic Peninsula including Larsen B Area, and
 showing Lockyer Island Station location near Snow Hill Island.

The oceanographers on board the vessel have discussed how to modify our
 sampling program to best advance our goals of studying the effects of
ice-shelf loss on Antarctic marine ecosystems, while working in waters in 
which sea-ice conditions will allow the ship to work. A number of smaller 
ice shelves have collapsed on this eastern side of the Antarctic Peninsula 
in the last few decades, including one covering the southern Gustav Channel
 (see map). We now plan to sample the Gustav Channel as a post-ice shelf
 system (with ice shelf loss in about 1992), and then to sample the mid- and
 outer-continental shelf stations east of James Ross Island, to provide a
 comparison with the open sea-ice zone. We will also sample an inner shelf
 site just west of Snow Hill Island, very close to our current location. 
These latter three sites will provide a necessary context to evaluate
 colonization patterns in the Gustav Channel, and in the Larsen B area, when
 we finally are able to get south of Robertson Island (most likely not until
 2012, during our next LARISSA cruise). Thus, even though we are currently 
barred from the Larsen B area by sea ice, we will be able to conduct
 ecosystem studies on this cruise that advance or understanding of the
effects of rapid climate warming and loss of ice shelves on Antarctic
 marine ecosystems. Now that we have a workable plan, we are eager to 
press forward with our sampling!

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