Snowfall in Antarctica has increased by 10 per cent since 1800, an analysis of ice cores from Antarctica has revealed.
An increase in snowfall has long been predicted as a result of global warming. “A warming atmosphere is wetter, producing more precipitation,” says team leader Liz Thomas of the British Antarctic Survey, who presented the findings today at a meeting of the European Geosciences Union in Vienna, Austria.
In fact, it used to be thought that increased snowfall in the Antarctica would more than counter any ice loss due to warming. Early IPCC reports forecast that the ice sheets of Antarctica would grow over the 21 century. But gravity-measuring satellites have shown that the continent’s ice sheets have been losing mass since at least 2002.
These vast ice sheets are made of the snow that has fallen in Antarctica over the past million years or so. As the snow builds up, it is gradually compressed and turned into ice.
To find out how snowfall has changed recently, Thomas and her colleagues analysed 79 ice cores from across the Antarctic, most of which went back at least 200 years. For the whole of Antarctica, they found that 10 per cent more snow falls now than 200 years ago, an average difference per decade of 272 gigatonnes of water, says Thomas. Her team has already published some of the results, with more to follow soon.
The greatest increase in snowfall has been over the Antarctic Peninsula, where the mass of snow per decade has risen by 123 gigatonnes in 200 years. “Sea ice around the peninsula is reducing, so you have more ocean water to increase moisture,” Thomas says. Changes in ocean currents are also lead to upwelling of warm water, which also increases evaporation – and thus snow.
The increase in snow means that global sea level has risen very slightly less – just a fifth of a millimetre – than it would have otherwise. “If it had fallen elsewhere not as snow but as rain, it would have contributed to sea level rise,” says Thomas.
Unfortunately, the increase in snowfall – and thus in ice accumulation – is being more than outweighed by the increase in ice loss, which is mainly due to the speeding up of the glaciers that flow from the ice sheets into the sea. A 2016 study shocked researchers by forecasting that ice loss from the Antarctic alone could add a metre to global sea level by 2100.