Environment

Oceans melt Antarctica's ice from below

The Antarctic ice sheet (shown here in a three-dimensional NASA image that exaggerates the vertical scale) is losing more ice from oceanic currents eating at it from below than from the breaking off of large blocks of ice.

They may be less dramatic than the events in which icebergs break off, but everyday interactions with warm ocean currents could cause more than half of the ice melt along Antarctica’s coastline.

Ice shelves are portions of the larger ice sheet that extend over the ocean, floating on seawater. Conventional wisdom once held that calving, the break off of large chunks of ice, was the main factor driving ice-shelf dynamics, but recent research has underscored the role of melting from below, or 'basal' melting. A team of scientists led by Eric Rignot at the University of California, Irvine, has for the first time quantified this effect for the entire continent.

The results, which appear in Science, suggest that warm ocean currents are melting ice shelves predominantly at certain locations around the continent, to an extent that accounts for 55% of the annual meltwater. The findings will help scientists to tackle larger questions about how the Antarctic ice sheet might change in future and its contribution to global sea-level rise.

Rignot suggests that the ice shelves act like stoppers, stemming the slow flow of continental ice. “If they thin and disappear, then the continental ice will accelerate its movement to the sea.”