Exploring New Model of Ice Cliff Collapse

Greenland ice sheet. Hannes Grobe 20:10, 16 December 2007 (UTC), CC BY-SA 2.5, via Wikimedia Commons

By Jim Brace-Thompson

Immense ice sheets have long covered Greenland and Antarctica, tying up water and giving us enticing vacation spots like the low-lying Florida peninsula. As temperatures rise around the globe from climate change, scientists have been worried about the rise of ocean waters along all coasts from the release of water tied up in the big ice sheets. Bye-bye, Florida!

The standard model says that as climate warms, marine ices at the edges of Greenland and Antarctica retreat and form ever taller ice cliffs that become increasingly unstable and increasingly amendable to collapse, causing further retreat. And as those cliffs collapse at an increasing pace, we are on a course toward seeing imminent, sustained and catastrophically rapid flow and collapse of entire continental ice sheets behind the marine margins. This is the so-called “marine ice-cliff instability” hypothesis.

Now, in a recent issue of the journal Science, a team led by Jeremy N. Bassis (University of Michigan, Ann Arbor) has formulated a new hypothesis suggesting a collapse may not be as rapid as feared. In fact, they say, their model shows that “small resistive forces from sea-ice and calved debris can slow down or arrest retreat, reducing the potential for sustained ice sheet collapse.” Their new model incorporates more localized variables and nuances than the standard model that is more or less one-size-fits-all.

Some fellow scientists are saying this represents “an improved rheologic model.” (Rheology studies the deformation and flow of matter including “soft solids” like ice sheets that exhibit something of a plastic flow.) However, those of us living in coastal communities shouldn’t just sit back and breathe a sigh of relief. This new model still shows that even if collapse is not catastrophically rapid, a heck of a lot of sea level rise is still on our horizon if global temperatures continue to rise.


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