LARISSA takes unique approach for research on ice shelf ecosystem
Posted September 18, 2009
Eugene Domack and his colleagues aboard the ARSV Laurence M. Gould were about six hours north of where the Larsen B Ice Shelf once floated on the northwest Weddell Sea when they made perhaps the biggest discovery of the 2005 science cruise.
A few minutes of videotape taken underwater revealed extraordinary signs of life on the floor of the continental shelf — bacteria so thick it was visible to the naked eye in what biologists call bacterial mats, along with bivalves such as clams. The scientists had unexpectedly discovered a cold seep biological community, subsisting not on light as most ecosystems but on methane vented through the seafloor.
Thick sea ice stymied a return voyage in 2006 to sample the unique ecosystem, which would have existed under the lightless shadow of the Larsen B Ice Shelf until it abruptly collapsed in 2002.
The discovery turned even more shocking — and, for curious scientists, even more interesting — when Domack’s team determined, based on benthic sediment cores, the ice shelf had been in place for at least 10,000 years.
Adding to the mystery: In 2007, a German team that did manage to reach the spot where the seep community was found reported that it was dead — and for what appeared far longer than it seemed possible based on its discovery only two years ago.
Questions emerged, as they always do: What happened to the newly discovered ecosystem? Is it truly dead or still alive? Did it evolve because of or in spite of the ice shelf? What did the collapse of the ice shelf do to the local ecosystem? How will it evolve now that that portion of the ice shelf is gone? Did global warming cause the ice shelf to break up abruptly? Or was the collapse part of a millennia-old cycle?
Some of the answers may come from LARISSA. The LARsen Ice Shelf System, Antarctica , project is an interdisciplinary program to study as many facets of the system as possible, from the remaining ice shelf itself to marine sediments piling up on the continental shelf below and from the critters that call the Larsen Embayment home to ocean circulation patterns.
LARISSA is funded by NSF’s Antarctic Integrated System Science (AISS) program .
“To be an AISS project, the ‘I’ must be met — a project must be integrated,” explained AISS program manager Lisa Clough. “It’s a bit difficult to describe, but I think a useful question to ask is what happens to the project if one of the pieces is removed — if you can’t answer the overarching questions unless all components are present — that’s an integrated project.
“LARISSA clearly meets the integration challenge,” she added. “All the scientific pieces are interesting in their own right, but putting all the pieces together will make the whole much greater than the sum of its parts, and provide critical insight into climate change questions.”
Chief scientist Domack said getting answers to many of those questions will have implications beyond the Antarctic Peninsula and the Weddell Sea.
“It’s a way for scientists to look at a small system and all the bits and pieces that contribute to its fundamental change and refine our models and estimates of how the larger parts of the Antarctic cryosphere will respond to the future,” explained Domack, a geosciences professor at Hamilton College in New York.
The LARISSA team will deploy on a two-month research cruise aboard the RVIB Nathaniel B. Palmer beginning in January 2010.
The ice shelf goeth
The Larsen B Ice Shelf was one of three ice shelves that made up the total Larsen Ice Shelf, which mainly consists now of Larsen C. Still, the remaining ice shelf is the third largest ice shelf in West Antarctic after the Ross and Ronne-Filchner ice shelves at about 48,000 square kilometers.
The Larsen A, the smallest of the three, disintegrated in January 1995 after decades of retreat. The collapse of 3,250 square kilometers of the Larsen B during a few short weeks in early 2002 represented the largest such event in more than 30 years of ice-shelf observations, according to the Boulder-based National Snow and Ice Data Center (NSIDC) .
LARISSA will offer NSIDC lead scientist Ted Scambos an opportunity to get up close and personal with a region he has observed and studied for 14 years, mainly using satellites.
“I’m really looking forward to it,” said Scambos, a principal investigator on the project and the lead on the cryosphere and ocean investigations. “It’s an area that’s on the cutting edge of climate change. Things that are happening there on the peninsula are a precursor to what’s going to happen over larger parts of Antarctica over the coming decades.”
Scientists estimate the peninsula has warmed by more than 2.5 degrees Celsius since the 1950s and more than double that average during the winter season. The verdict is mixed on whether the rest of the continent is heating up, with many on the scientific jury of the opinion that parts of West Antarctica are changing rapidly, particularly an area around Pine Island Bay on the Amundsen Sea where glaciers are retreating.
A paper in the journal Nature in January 2009 reported that overall Antarctica is warming in step with the rest of the planet, with the smaller western half heating up more than the high-altitude eastern side is cooling. “If that’s the case, other ice shelves will feel the brunt of rising summer temperatures,” Domack said.1 2 3 Next