Nature has a paper this week from the British Antarctic Survey. Confirming what we already know about the effects of global warming, it also differentiates between the effects of currents, their cause and the air temperature effects at the ice surface.
Now we can start worrying about when the sea level rises and how far! Hamish Pritchard prepares us, "In most places in Antarctica, we can't explain the ice-shelf thinning through melting of snow at the surface, so it has to be driven by warm ocean currents melting them from below.
We've looked all around the Antarctic coast and we see a clear pattern: in all the cases where ice shelves are being melted by the ocean, the inland glaciers are speeding up. It's this glacier acceleration that's responsible for most of the increase in ice loss from the continent and this is contributing to sea-level rise." The group of scientists from the Survey also included researchers from Utrecht and San Diego and were funded by the NERC. (Natural Environment Research Council).
4.5 million measurements were made via NASA's ICEsat of the floating ice shelves around the continent. 20 out of 54 are being melted by ocean currents. With the acceleration of inland glaciers feeding the ice flows, which themselves are thinning by up to a few meters per annum.
Billions of tons of ice then drain to the sea from the glaciers. Now we can see the importance of the ice shelves in supporting and slowing down the glaciers.
Wind patterns have changed in both strength and direction with global warming, causing warm water from ocean currents to funnel down beneath the ice. To the east, however, on the peninsula that stretches toward Chile in South America, winds themselves seem to blame for melting.
In the summer, they cause the surface of the ice-shelves to melt David Vaughan of the EU's ice2sea programme commented that, "this study shows very clearly why the Antarctic ice sheet is currently losing ice, which is a major advance. But the real significance is that it also shows the key to predicting how the ice sheet will change in the future is in understanding the oceans. Perhaps we should not only be looking to the skies above Antarctica, but also into the surrounding oceans."
Here in answer to him is an animation from NASA's Echo2 project, showing the delicate and thin blue layers of the ice flows:
Credit: NASA/Goddard CGI Lab