Most of the ice being lost from Antarctica is going as a result of warm water eating the fringes of the continent, scientists say.
The researchers used a satellite laser to measure the thinning occurring on ice shelves – the floating tongues of ice that jut out from the land.
The team’s analysis found the shelves’ shrinkage could not be attributed simply to warmer air temperatures.
Rather, it is warm water getting under the floating ice to melt it from below.
This is leading to a weakening of the shelves, permitting more and more ice to drain from the continent’s interior through tributary glaciers.
Previous studies have already indicated that warmer waters are being driven towards the continent by stronger westerly winds in the Southern Ocean.
The researchers say the new understanding has major implications for their ability to reliably project future sea-level rises as a result of Antarctic ice loss.
“What we realise now is that we’re looking at a very sensitive system,” Dr Hamish Pritchard, from the British Antarctic Survey (BAS), told BBC News.
“Previously, you would have thought that we needed a lot of warming in the atmosphere to get a substantial loss of ice from Antarctica – because it’s such a cold place. But what we show is that that’s not necessary; you don’t need radical change.