LARISSA - LARsen Ice Shelf System,
"Collaborative Research in IPY: Abrupt Environmental Change in the Larsen Ice Shelf System, a Multidisciplinary Approach - Marine Ecosystems"
Craig R. Smith, Maria Vernet, Cindy Van Dover, Michael McCormick, Principal Investigators
We are conducting a multi-disciplinary field program to address the rapid and fundamental changes occurring in the Antarctic Peninsula region as a consequence of the sequential collapse of large sections of the Larsen B Ice Shelf from 1995 to 2008. 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 under the former ice shelf 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. We are testing the following hypotheses to elucidate the transformations occurring in marine ecosystems as a consequence of the Larsen B collapse:
1) Cold Seeps: The biogeographic isolation and sub-ice shelf setting of the Larsen B seep has led to novel habitat characteristics, chemoautotrophically dependent taxa and functional adaptations.
2) Background (Non-Seep) Benthos: Benthic communities beneath the former Larsen B ice shelf are fundamentally different from assemblages at similar depths in the Weddell sea-ice zone, and resemble oligotrophic deep-sea communities. Larsen B assemblages are undergoing rapid change related to time since exposure to overlying primary primary production.
3) Phytoplankton Communities: The previously dark, oligotrophic waters of the Larsen B embayment now support a thriving phototrophic community, with production rates and phytoplankton composition similar to other productive areas of the Weddell Sea.
4) Whale-Bone Communities: The distribution of whale-bone eating worms in the genus Osedax reflects to time since ice-shelf breakout in (and whale access to) surface waters.
To test these hypotheses, and to document rapid changes occurring in the Larsen B ecosystem, we are using a remotely operated vehicle, shipboard samplers, towed camera systems and moored sediment traps to:
a) Sample and characterize microbial, macrofaunal and megafaunal components of the seep community,
b) Evaluate patterns of surface productivity, export flux, and mega-, macro- and meiofaunal communty composition in areas previously covered by the ice shelf and compare them to the open sea-ice zone,
c) Place ecosystem changes within the geological, glaciological and climatological context that led to ice-shelf retreat,
d) Predict the likely consequences on marine ecosystems of ice-shelf collapse in other regions of Antarctica vulnerable to climate change.
These activities are being conducted during a cruise in Jan-Mar 2010 to the Larsen B region, with sediment-trap and whale-bone lander recoveries occurring 24 months later. Our efforts will significantly advance understanding of linkages among the earth’s systems in polar regions and are proposed in the true spirit of IPY. The project is tightly linked to companion projects addressing Marine & Quaternary Geosciences and Cryosphere & Oceans, topics, and to international collaborators from Argentina, Belgium, Canada, Germany, Spain and the United Kingdom.
SAMPLING THE SEA FLOOR SEDIMENTS
To sample the sea floor sediments and benthic fauna in the Antarctic Peninsula we employ several remote sampling techniques, including imaging of the seafloor with a towed camera plataform, coring and trawling.
We will be posting news directly from the ship N.B. Palmer. Follow us in another exciting experience down in the Antarctic ecosystem.
All pictures should be credited to our Scientific crew
Last updated, December 28 of 2009 by Fabio De Leo: email@example.com
THE LARSEN ICE-SHELF COLLAPSE IN 2002
Five true color images of the collapse of the Larsen B ice shelf of January, February, and March 2002, as recorded by NASA's MODIS satellite sensor. The first image (from top to bottom in the panel bellow) is from 31 January 2002, and shows the shelf in late austral summer with dark bluish melt ponds dotting its surface. The last image is from 7 March, with thousands of sliver icebergs and a large light blue area of very finely divided bergy bits where the shelf formerly lay. Brownish streaks within the floating chunks mark areas where rocks and morainal debris are exposed from the former underside and interior of the shelf. The last phases of the retreat totalled approximately 2600 square km.
Photo credits: NASA (http://www.nasaimaghes.org)