Larsen C Ice Shelf Loses Iceberg the Size of Delaware

A trillion-tonne, 5,800-square-kilometre section of ice—an expanse the size of Delaware, 200 square kilometres larger than Prince Edward Island, and twice the volume of Lake Erie—finally broke away from Antarctica’s Larsen C ice shelf Wednesday, in a long-anticipated event widely seen as a marker for accelerating climate change.

The “calving” event reduces Larsen C by 12%, bringing it to its smallest size ever recorded.

“We have been anticipating this event for months, and have been surprised how long it took for the rift to break through the final few kilometres of ice,” said Prof. Adrian Luckman of Swansea University, lead investigator with Project MIDAS. “We will continue to monitor both the impact of this calving event on the Larsen C Ice Shelf, and the fate of this huge iceberg.”

Luckman said the iceberg, “one of the largest ever recorded”, will likely break into fragments. The ice shelf itself “could either gradually regrow, or may suffer further calving events which may eventually lead to collapse—opinions in the scientific community are divided,” he added. “Our models say it will be less stable,” though Project MIDAS puts Larsen C’s collapse years or decades away.

EcoWatch explains that the new iceberg “will have no immediate impact on sea level since it was already floating before it calved. However, as these ice shelves disintegrate, the land-locked glaciers they hold back may begin sliding into the sea.”

While Larsen C was blocking relatively little land ice from entering open water, the New York Times adds, similar ice shelves in other parts of Antarctica “are holding back enormous amounts of ice, and scientists fear that their future collapse could dump enough ice into the ocean to raise the sea level by many feet. How fast this could happen is unclear.”

Climate Central points to the sheer mass of the iceberg: “After all, can you really imagine 463 million Olympic-sized pools, let alone all those pools filled with ice?” asks writer Brian Kahn. Instead, illustrations accompanying Kahn’s post compare an equivalent eight-mile sphere to the geographies of New York, Miami, Chicago, Denver, San Francisco, Mount Rainier, and the Grand Canyon.

Much of the news coverage following the Project MIDAS announcement reflected some scientists’ hesitancy to link it definitively to climate change. “We just can’t make a clear connection to this being driven by climate change at this time,” NASA glaciologist Christopher Shuman told CBC. “This is a worrisome sign for the Larsen C: you can’t lose 12 or 13% of your area from an ice shelf and not think, ‘Hmm. Well, that’s an awful lot that’s gone missing.’ On the other hand, there have been previous large bergs from this area.”

“While it might not be caused by global warming, it’s at least a natural laboratory to study how breakups will occur at other ice shelves to improve the theoretical basis for our projections of future sea level rise,” NASA polar specialist Thomas P. Wagner added on the Times.

That didn’t sit well with Climate Nexus Strategic Communications Director Hunter Cutting, whoresponded with his own self-described Twitter rant.

“In the jargon of the field, the null hypothesis of some scientists is that there is no#climatechange link in #LarsenC until one is found,” he wrote. But “given regional trends, I don’t see any legit basis for a null hypothesis of no #climatechange role in #LarsenC break-up. U.S. National Academies of Science have explicitly rejected use of the ‘no #climatechange’ null hypothesis for ALL extreme weather events.” And “given radical trends at poles driven by#climatechange, no-climate-change null hypothesis does not seem justified in #LarsenC.”