How Will Warming Air Temperatures Impact Antarctica's Ice Shelves?

The ice sheets off Antarctica prevent the glaciers from sliding into the ocean. Pen State/Flickr CC BY-NC-ND 2.0

If the entire Antarctic ice sheet were to melt, it’s estimated that it would raise the sea level by an astonishing 61 meters (200 feet). While this is unlikely to ever happen, if even just a fraction of it were to thaw the impact could be disastrous. With it looking increasingly like the world will pass the crucial 2 degrees Celsius (3.6 degrees Fahrenheit) warming limit, a new study has found that if we carry on emitting greenhouse gases as usual, there will likely be mass melting of the ice shelves. But if we cut emissions now, these consequences could be avoided.

When trying to predict how climate change is likely to affect the melting of Antarctic ice, one of the most important aspects to understand is the ice shelves that surround the continent. These are effectively the floating platforms of ice that form when the glaciers meet the ocean. And they can be vast; the Ross Ice Shelf, for example, spans roughly 510,000 square kilometers (200,000 square miles). The shelves act a little like corks in bottles of champagne, holding back the glaciers on the land and stopping them from sliding into the sea and increasing global sea levels.

A new study, published in Nature Geoscience, looks at how rising air temperatures might impact the surface melt on the massive ice sheets found in Antarctica, which can affect their stability. When the tops of the sheets melt, the water pools on the surface and starts to trickle down the cracks and holes naturally present. This causes the cracks and fissures to deepen and widen, and can eventually lead to the shelves collapsing entirely. This is effectively what happened to the Larsen B ice shelf in 2002, which partially collapsed and broke apart in a matter of just a few months.

The researchers produced two models, one in which we continue burning fossil fuels in a “business-as-usual” scenario, and another in which we stabilize emissions fairly sharpish. What they found was that up until around 2050, it’s likely that surface melt will double in both situations to almost 200 gigatons (200 billion metric tons) of surface water a year. But it’s after this point that is most interesting, as the models then start to diverge. In the one in which we stabilize emissions, surface melt doesn’t increase further, but in the business-as-usual model, melting speeds up by almost eight times.

“Our results illustrate just how rapidly melting in Antarctica can intensify in a warming climate,” explains Luke Trusel, from the Woods Hole Oceanographic Institution, and who led the study. “This has already occurred in places like the Antarctic Peninsula where we've observed warming and abrupt ice shelf collapses in the last few decades. Our model projections show that similar levels of melt may occur across coastal Antarctica near the end of this century, raising concerns about future ice shelf stability.”

But this isn’t as doomsday a study as it might at first sound, as it clearly indicates that these events are entirely dependent on our own behavior, and how much more greenhouse gas we pump into the atmosphere. If we can get on top of our emissions, as almost every climate scientists agrees we should if we are to survive, then the melting of the Antarctic ice sheet can hopefully be limited.

Image credit: Pen State/Flickr CC BY-NC-ND 2.0

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