Faltering Ice – The Crack in Larsen C

There is currently a great deal of collective breath-holding surrounding the fate of a portion of the Larsen C ice shelf. Reports since December have been narrating the changes in a widening crack along its face, as the rift has increased in length by 20 miles. Only a 12 mile stretch of intact ice keeps the shelf tenuously anchored. As USA Today notes, you can literally bet on when it will give way.

The Larsen ice shelf is a region of chaos along the Antarctic Peninsula which curves towards the toe of Chile. The region is named after whaling captain and explorer Carl Anton Larsen, who experienced an Antarctic winter stranding with his men, not unlike that of Ernest Shackleton. Much of the shelf has already been lost previously due to catastrophic collapse events. 1995 saw the crumbling of Larsen A. Seven years later, Larsen B disintegrated over the course of 2-3 months. Its epic demise was cataloged by watching satellites.

The sheering off of these massive stretches of ice are not without effect. Ice shelves are comparable to sea ice, and their liberation does not directly contribute to changes in sea level. However, they often fortify nearby glaciers, and once absent, glacial movement can speed up significantly. Glacial ice, in contrast, can contribute to changing sea levels. It is thought that global warming trends have contributed to many ice sheet de-stabilization events around Greenland and Antarctica. Because ice is a cooling influence on climate due to its reflective nature (called albedo), ice loss is part of a positive feedback loop. Warming trends reduce both ice cover and albedo which leads to further warming.

This NASA photo released December 1, 2016 shows what scientists on NASA's IceBridge mission photographed in a view of a massive
View of the Larsen C ice shelf fissure in Nov 2015 as documented by the NASA Icebridge Mission.

On perhaps a lighter note however, the calving of ice also has also led to unexpected discoveries. After the break up of Larsen B, scientists discovered an intricate chemotrophic ecosystem a half mile below the ocean’s surface.  Chemotrophic organisms create their own energy through chemical pathways rather than relying on photosynthesis. The system below Larsen B was populated by cold seep clams and mats of microbes, examples of tenacious organisms that have adapted to get by with little access to sunlight or the growth of the phytoplankton food source it supports. This along with findings like vast microbial communities found within subglacial lakes in Antarctica adds to our collective evidence that life finds ways to subsist in the most extreme of environments.

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