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An Antarctic expedition will search for what lived under the Larsen C ice shelf

Author: Carolyn Gramling / Source: Science News

larsen c and iceberg A68
BERG IN MOTION Iceberg A68 fully split from the Antarctic Peninsula’s Larsen C ice shelf in July 2017, but was still hugging the coast in November 2017 (left). A year later, the iceberg had rotated around and drifted northward, fully exposing the seafloor it once shadowed (right).

Maybe the fourth time’s the charm. On February 9, an international team of scientists is embarking on yet another mission to hunt for ocean life that may have once dwelled in the shadow of a giant iceberg (SN Online: 10/13/17). The scientists, led by researchers at the Alfred Wegener Institute in Bremerhaven, Germany, are headed to the Larsen C ice shelf on the Antarctic Peninsula, where a Delaware-sized iceberg broke off a year and a half ago.

Three previous expeditions have set a course for the ice shelf since the big break in July 2017 (SN: 8/5/17, p. 6). To reach the site, ships must navigate through sea ice drifting in the Weddell Sea, which lies between the Antarctic Peninsula and the main continent. There’s a narrow time window when the sea ice is at its sparsest: just after the Southern Hemisphere’s midsummer, from February into March.

But good timing isn’t a guarantee of success. Two previous missions, a British Antarctic Survey–led expedition in February 2018 and a Korea Polar Research Institute mission in March 2018, were stymied by thick sea ice blocking their way through the Weddell Sea (SN Online: 3/3/18). A third, led by scientists at the Scott Polar Research Institute in Cambridge, England, reached the shelf in late January 2019, but strong winds and dangerous ice floes ultimately forced the team to move on to focus on its primary (and still ongoing) mission — to find polar explorer Ernest Shackleton’s ship Endurance, which sank in the Weddell Sea in 1915.

This latest team will be traveling aboard the Alfred Wegener Institute’s icebreaker Polarstern, the most powerful ship yet to make the attempt. Polarstern’s reinforced hull means that the ship can withstand greater battering from sea ice, and can linger longer in the area until the waters begin to freeze — roughly at the end of March.

ICY HAZARD Sea ice has congested the gap between the A68 iceberg and the Larsen C shelf, as seen in this October 2018 image snapped by NASA’s airborne Operation IceBridge mission. Sea ice conditions have stymied previous ship-based attempts to reach the site, but the Alfred Wegener Institute’s icebreaker Polarstern is the strongest ship yet to make the attempt.

Moreover, the berg that broke off from Larsen C, now dubbed A68, also has finally moved out of the way, fully exposing the seafloor that it once shadowed. That also reduces the risks: With the iceberg still looming nearby, last year’s expeditions were in danger of being crushed by it, or rocked by large waves generated by falling ice chunks.

“I’m confident that if anyone’s going to get there, it’ll be this mission,” says Huw Griffiths, a marine biologist with the British Antarctic Survey in Cambridge, England, who will lead the marine biology portion of the expedition.

Science News talked with Griffiths about what he hopes to find lurking on the seafloor. His responses have been edited for length and clarity.

SN: What sorts of equipment will you use to study the seafloor?

Griffiths: Sonar to study…

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