Antarctic ice crack could cause big rise in sea level

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A massive crack in an Antarctic ice shelf — 110 miles long and 1,500 feet wide — appears set to create a gigantic iceberg larger than Rhode Island, potentially leaving an “unstable configuration,” according to researchers.

The British Antarctic Survey released a 70-second video of the “fast-moving” crack in the Larsen C ice shelf on Tuesday and warned that an iceberg larger than 5,000 square kilometers (1,930 square miles) — bigger than Rhode Island and roughly the size of Trinidad — is likely to break off.

“Iceberg calving is a normal part of the glacier life cycle, and there is every chance that Larsen C will remain stable and this ice will regrow,” Dr. Paul Holland, a researcher with the group, said in a statement. “However, it is also possible that this iceberg calving will leave Larsen C in an unstable configuration. If that happens, further iceberg calving could cause a retreat of Larsen C. We won’t be able to tell whether Larsen C is unstable until the iceberg has calved and we are able to understand the behavior of the remaining ice.”

Ice shelves typically produce an iceberg every few decades. There’s currently not enough data to determine whether the expected calving is the result of climate change, but the British researchers claim there’s scientific evidence that climate change has caused thinning of the ice shelf.

The key question, according to the researchers, becomes whether Larsen C will begin retreating once the mammoth iceberg is calved.

The Larsen A and B ice shelves, which are located farther north in the Antarctic Peninsula, collapsed in 1995 and 2002, respectively, leading to dramatic acceleration of glaciers behind them and contributing to a rise in sea levels.

“The stability of ice shelves is important because they resist the flow of the grounded ice inland,” Holland’s statement continued. “After the collapse of Larsen B, its tributary glaciers accelerated, contributing to sea-level rise.”

Just last week, a chunk of ice the size of Manhattan broke off Pine Island Glacier and floated into Antarctic waters. Two years ago, an iceberg 10 times larger broke away from the same area, calving a chunk of ice that measured 225 square miles.

“I think this event is the calving equivalent of an ‘aftershock’ following the much bigger event,” Ian Howat, a glaciologist at Ohio State University, said in a statement released by NASA’s Earth Observatory on the event. “Apparently, there are weaknesses in the ice shelf — just inland of the rift that caused the 2015 calving — that are resulting in these smaller breaks.”

Meanwhile, the effects of a collapse of the Larsen C ice shelf could be felt far beyond Antarctica, since the glaciers that flow into it contain enough water to raise the global sea level by a centimeter. By comparison, according to Scientific American, global sea levels are rising by just 3 millimeters annually, with one study suggesting that as much as one-third of that total comes from losses throughout Antarctica and Greenland.