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SOURCE: Earther

DATE: October 30, 2018

SNIP: The Pine Island Glacier has been breaking off monstrous icebergs over the past five years, presenting a worrying sign that the West Antarctic is destabilizing. The latest occurred this weekend. Satellite imagery shows an iceberg roughly 115 square miles—five times the size of Manhattan—breaking off the front of the glacier.

“What is mostly remarkable about this event is that the frequency of calving seems to increase,” Lhermitte said about the big boy ‘berg that broke off Pine Island Glacier. In the 2000s, so-called iceberg calving events of this magnitude used to occur roughly every five years. But since 2013, there have been four calving events including one last year.

Icebergs break off the front of glaciers on the regular because glaciers are giant rivers of ice. As the upstream ice flows toward the sea, it puts tremendous stress on the ice below, causing icebergs to snap off.

But what’s been happening at Pine Island Glacier in recent years could be a sign the flow is increasing. Satellite imagery put together by Lhermitte shows that the calving front has slowly receded for decades before beginning a sharp recession in recent years, including 3 miles of shrinkage since 2015 alone.

All that activity has contributed to making Pine Island Glacier the most rapidly receding glacier on Earth. In addition to the calving area retreating, the ice has gotten thinner by about a meter annually over the past 15 years while shedding a staggering 45 billion tons annually. Much of that is driven by warm water eating away at it from underneath.

If the disintegration continues, there’s concerns it could lead to something call marine ice cliff instability, where the walls of ice at the calving front get progressively taller due to the downward slope of the bedrock beneath it. This is expected to make the remaining ice more wobbly, like an ever-growing Jenga tower, and it could lead to an even more rapid breakup of glaciers that causes sea level rise to spike.