Greenland And Antarctica ‘May Be Vulnerable To Rapid Ice Loss Through Catastrophic Disintegration’

Jul 30, 2013 by

Think Progress


By Joe Romm on July 30, 2013 at 4:51 pm


Humanity faces 70 feet of sea level rise, possibly coming much sooner than has been expected if we continue with unrestricted carbon pollution. Two recent studies underscore our perilous situation.

The first study found, “East Antarctica’s Ice Sheet Not as Stable as Thought,” as Science reported. This conclusion is consistent with other recent research that found we’re all but certain to end up with a coastline at least this flooded (20 meters or 70 feet):
70 feet SLR

Some taken solace in the notion that this amount of sea level rise might take more than a thousand years. But a second study finds, “stretches of ice on the coasts of Antarctica and Greenland are at risk of rapidly cracking apart and falling into the ocean.”

The lead author, Jeremy Bassis from the University of Michigan, explained that if this new analysis is right, “we might be closer to the higher end of sea level rise estimates for the next 100 years.” That “higher end” is about 5 or 6 feet.

Here’s a video of Bassis discussing his findings:

A key point of the study is that current ice sheet models don’t capture what is already being observed with our modest 1.5°F warming to date — 60% faster sea level rise than models had projected:

Iceberg calving, or the formation of icebergs, occurs when ice chunks break off larger shelves or glaciers and float away, eventually melting in warmer waters. Although iceberg calving accounts for roughly half of the mass lost from ice sheets, it isn’t reflected in any models of how climate change affects the ice sheets and could lead to additional sea level rise, Bassis said.

“Fifty percent of the total mass loss from the ice sheets, we just don’t understand. We essentially haven’t been able to predict that, so events such as rapid disintegration aren’t included in those estimates,” Bassis said. “Our new model helps us understand the different parameters, and that gives us hope that we can better predict how things will change in the future.”

Earlier studies had also found that rapid ice loss is possible. A 2009 study of coral fossils in the journal Nature found “catastrophic increase of more than 5 centimetres per year over a 50-year stretch is possible” — that is more than 8 feet in half a century. The lead author of that study warned, “This could happen again.”

The new study provides a mechanism by which such rapid ice loss may be possible. “Portions of Greenland and Antarctica,” the it concludes, “may be vulnerable to rapid ice loss through catastrophic disintegration.” See also Like Butter: Study Explains Surprising Acceleration Of Greenland’s Inland Ice” and Antarctica Is Melting From Below, Which “May Already Have Triggered A Period of Unstable Glacier Retreat”.

Let’s return to the study of the East Antarctic Ice Sheet (EAIS) during the Pliocine Epoch (from 5.3 million to 2.6 million years ago). Lead author Carys Cook explained:

“Scientists previously considered the East Antarctic ice sheet to be more stable than the much smaller ice sheets in West Antarctica and Greenland, even though very few studies of East Antarctic ice sheet have been carried out. Our work now shows that the East Antarctic ice sheet has been much more sensitive to climate change in the past than previously realised. This finding is important for our understanding of what may happen to the Earth if we do not tackle the effects of climate change.”

It’s important because, as Science reported, “Current warm temperatures and high greenhouse gas conditions are reminiscent of the warm Pliocene Epoch,” when mean temperatures were “2°C to 3°C warmer than today, and atmospheric carbon dioxide concentrations between 350 and 450 parts per million” (we’re currently at 400 ppm). And that matters because:

Some data have also suggested that sea levels were perhaps 22 meters higher than today—and even complete melting of the WAIS [West Antarctic ice sheet] and Greenland couldn’t account for more than about 12 meters of that, Cook says. Melting of the EAIS would have to have contributed.

Now it appears the EAIS can see significant retreat even with the level of warming we are headed toward in the second half of this century.

Just last year the lead author of paleoclimate research funded by the National Science Foundation (NSF) said, “The natural state of the Earth with present carbon dioxide levels is one with sea levels about 70 feet higher than now.” And that was only slightly less worrisome than a 2009 paper in Science that found when CO2 levels were this high 15 million years ago, it was 5° to 10°F warmer and seas were 75 to 120 feet higher.

The time to rapidly reduce carbon pollution was decades ago, but now is still vastly better than later.

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