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When the Larsen C ice shelf broke, it exposed a hidden world

Science teams are racing to Antarctica to assess ice, seafloor ecosystems

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1:33pm, October 13, 2017
RRS James Clark Ross

ICY VOYAGE  In February, an expedition led by the British Antarctic Survey will journey to Antarctica on the RRS James Clark Ross (shown here during the Antarctic summer of 2010‒2011) to study a mysterious ecosystem exposed in July by the calving of the Larsen C iceberg.

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Teams of scientists are gearing up to race to the Antarctic Peninsula to find out what happens in the immediate aftermath of a massive ice calving event. In July, a Delaware-sized iceberg broke off from Antarctica’s Larsen C ice shelf (SN: 8/5/17, p. 6). Now, several research groups aim to assess the stability of the remaining ice shelf, map the region’s seafloor and study a newly exposed ecosystem that’s been hidden from the sun for up to 120,000 years.

First on the scene in November will be a team of scientists led by geophysicist Adam Booth of the University of Leeds in England and the U.K.-based Project MIDAS, which tracked the progress of the rifting from 2014 until the final break (SN: 7/25/15, p. 8). The researchers will conduct ground-penetrating radar and passive seismic surveys of the still-intact ice shelf, looking for shifts in the subsurface ice. They will also use GPS to monitor movements of the ice shelf.

The goal is to track the dynamic response of the ice to the calving event, both short-term and long-term. Computer simulations suggest that the central part of the shelf will speed up, now that a piece of its buttress has been removed, says glaciologist Adrian Luckman of Swansea University in Wales, who will analyze satellite data as part of the effort. “What we need to keep tabs on now is whether the speedup will in any way destabilize what’s left. It might take many months to play out.”

Meanwhile, another team of scientists, led by marine biologist Katrin Linse of the British Antarctic Survey, is preparing for its own voyage in February. Linse and her colleagues’ urgent mission is to study seafloor that was in the shadow of the ice before the ecosystem changes. Now that sunlight can penetrate those waters and more food will be available, new creatures will begin to colonize the seabed. 

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Larsen C iceberg

Scientists have documented this transition before: In 2002, a Rhode Island‒sized chunk of ice calved from a different ice shelf, Larsen B, along the Antarctic Peninsula (SN: 10/18/14, p. 9). Five years later, a team of researchers investigated the seafloor species in the region once shadowed by ice. They found that some pioneering critters had already moved in, taking advantage of the change in circumstances (SN: 9/7/13, p. 11).

Linse says her team aims to get there before those pioneers do. “For the first time, we can set a baseline on what lives under ice shelves,” she says. The group’s proposal was green-lighted on October 9, becoming the first team to get the go-ahead to rapidly investigate regions exposed by ice shelf retreat under a new international conservation measure.

Linse expects to find something similar to ecosystems found in the deep sea — a dark, extremely food-sparse environment that spawns odd creatures such as carnivorous sponges and bivalves. “In the deep sea they have sponges that almost look like fly-eating plants, with long radials that are extremely sticky and catch anything that comes through the water column,” she says. But it’s also possible that the team will find nothing living there at all, she says. “That would be a very interesting result. [But] I expect to find life.”

In addition to a marine biologist’s typical tools— water samplers to measure salinity and temperature, plankton nets — the team’s toolbox will hold cameras, coring systems to collect seafloor sediment, and hydroacoustic equipment to map the topography of the now-exposed seabed. “We only have satellite data giving us the seafloor depth,” which is an estimated 500 meters, Linse says. “We will be the first to get real data on the water depth.”

Citations
Further Reading

A. Yeager. Delaware-sized iceberg breaks off Antarctic ice shelf. Science News. Vol. 192, August 5, 2017, p. 6.

T. Sumner. Fast-spreading crack threatens giant Antarctic ice shelf. Science News. Vol. 188, July 25, 2015, p. 8.

T. Sumner. Warming alone triggered Antarctic ice shelf collapse. Science News. Vol. 186, October 18, 2014, p. 9.

J. Shugart. Sponges boom thanks to Antarctic ice shelf bust. Science News. Vol. 184, September 7, 2013, p. 11.

S. Perkins. All cracked up from the heat? Major hunk of an Antarctic ice shelf shatters and drifts away. Science News. Vol. 161, March 30, 2002, p. 197.

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