In a warming world, let it snow!
Snowfall in Antarctica will increase owing to global warming, but this could make the ice melt faster, scientists in Germany have found.
It might seem strange that rising temperatures in the coldest place on Earth could cause it to snow more, but that is what Dr Katja Frieler and her team at the Potsdam Institute for Climate Impact Research have shown in a recent study.
Writing in the journal Nature Climate Change, the group showed how, for every degree of warming in an area, snowfall could be expected to increase by about 5%.
The water that forms the snow in Antarctica starts its journey by evaporating from the ocean surrounding the continent. "As the air warms up, it is able to hold more moisture, which can then be carried into the centre of Antarctica", explains Frieler.
Even in summer, the temperature in the centre of Antarctica is often colder than -20 °C, so the water in the air will eventually fall as snow. With temperatures always below freezing, this snow cannot melt and so it piles up, layer upon layer on the huge sheets of ice that already cover the continent.
The team reached their conclusion by comparing several different sources of information. This included looking at ice cores and using simulations to understand the link between temperature and snowfall during earlier periods of warming in Antarctica.
Understanding historical patterns was important for the team to be able to confidently predict what might happen in the future. Computer models are good at making predictions, but also need to be checked against real measurements to show that they are reliable.
The scientists believe that the amount of water being moved from the sea to Antarctica in this way is large enough to reduce the rate at which the sea level is rising. But the link isn't quite as obvious as it first seems.
"Without disturbances, there is a balance between the amount of snowfall and the amount of ice," says Frieler. As the snow builds up, its weight increases the pressure within the ice, causing it to flow toward the sea more rapidly, contributing to sea-level rise.
Do these findings mean that we don't need to worry about sea levels rising because of the Antarctic warming up? Frieler doesn't think so. She points out that her research has only considered effects that could cause a drop in sea levels, which are likely to be greatly outweighed by the melting of the huge ice sheets of the East and West of Antarctica.
"In the end, if you add all the components, the Antarctic's contribution to sea level rise is expected to be positive."