Increased Antarctic snowfall may reduce sea-level rise: study

Rising temperatures could increase the amount of snowfall over Antarctica which may help reduce the rise in global sea level, a new study has found.

When Antarctica's air temperature rises, moisture in the atmosphere increases. That should mean more snowfall on the frozen continent, researchers said.

However, as climate models predict, that trend has not become evident in Antarctica's surface mass balance.

Scientists from Columbia University in the US used historical records and climate simulations to examine that trend.

They found that the effect of rising temperatures on snowfall has so far been overshadowed by Antarctica's large natural climate variability, which comes from random, chaotic variations in the polar weather.

By mid-century, however, as temperatures continue to rise, the study shows how the effect of human-induced warming on Antarctica's net snow accumulation should emerge above the noise.

The expectation of more snowfall is something of a silver lining as temperatures rise. Global warming is already increasing sea level through melting ice and thermal expansion, researchers said.

The increase in snowfall over Antarctica could help reduce the amount of global sea level rise by 51 to 79 millimetres by the year 2100, according to the study.

"Increased snowfall over Antarctica is the sole process connected to global warming that is thought to have a significant mitigating effect on global sea level rise," said Michael Previdi from Columbia University in the US.

"While the magnitude of this effect is uncertain, it is likely that the balance of different processes determining Antarctica's net contribution to global sea level rise will be decidedly different in the future than it has been in the recent past," said Previdi.

On a continental scale, surface mass balance is the difference between the amount of snowfall that accumulates and the amount of snow lost to sublimation.

It affects global sea level because the amount of water on Earth is essentially constant, so when more water is stored as snow or ice on land, less water is available to contribute to rising seas.

For the study, researchers evaluated surface mass balance simulations from 35 coupled atmosphere-ocean climate models, which simulate the physical forces that affect Antarctica.

When the scientists looked at all 35 models, 46 per cent of the individual simulations showed a statistically significant trend in surface mass balance from 1961 to 2005, the year that most of the models' historical simulations end.

The likelihood of seeing a statistically significant trend in surface mass balance rises as the models forecast ahead in time, researchers said.

The findings were published in the journal Environmental Research Letters.