So one of the huge questions in Antarctic climate science has been what is primarily driving the melting of the ice-shelves. Are they thawing from above (warmer air temperatures) or from below (warm waters slowly eroding the base of the floating extensions of ice-sheets)? A paper published in Nature today, shows that most of the ice being lost from Antarctica is through melting by warm ocean currents. The international research team, led by Dr. Hamish Pritchard from the British Antarctic Survey (BAS), used a laser altimeter on NASA’s ICESat satellite to map the changes in thickness on Antarctic ice-sheets from October 2003 and November 2008, taking 4.5 million measurements! They found that 20 out of 54 ice-shelves measured are being melted from below, most of these from West Antarctica. Laser altimetry is a more precise technique to measure ice-sheet thickness through time, as opposed to satellite radar data (used in previous studies).
This substantially changes our views on ice-sheet loss because warm atmospheric temperatures are no longer a pre-requisite! In a recent press release, Pritchard has said: “We can lose an awful lot of ice to the sea without ever having summers warm enough to make the snow on top of the glaciers melt. The oceans can do all the work from below.” Their work also shows that there is a relationship between the basal melt (the melting that occurs at the base of the ice shelf) and wind-driven forcing. The changing wind patterns around Antarctica influence the strength and direction of ocean currents. In turn, this would increase warm currents flowing at the base of these shelves. This study also shows how sensitive the glaciers are to the changing climate.
On the Antarctic Peninsula, it’s a different story. The study shows that the predominant driver of ice-shelf thinning is from above – from the warm summer winds.
This study gives us a better understanding of sea-ice and climate interactions. So maybe more attention should now be given to understanding the ocean instead of just looking at the skies??