Based on a 25-year record of the Western Antarctic Ice Sheet, a team of scientists led by the British Antarctic Survey (BAS) have shown that changes in snowfall over Antarctica can have significant short-term effects on global sea level rises.
The Earth's climate is extremely complex and Antarctica is one of the great engines that regulate how it changes over the millennia. Not the least of the reasons for this is the giant ice cap that stands miles deep on the frozen continent. This vast reservoir of water has a major effect on sea levels around the world, so it's important to understand the dynamics of how the ice builds up and calves as icebergs into the sea.
According to modern computer models, the most important factors for how Antarctic ice affects sea levels are ocean currents and temperatures, which determine the long-term sea level rises, but there are short-term factors as well. In this case, snowfall.
By looking at snowfall rates at the Amundsen Sea Embayment in Western Antarctica, the BAS team determined that, though dwarfed by the much larger long-term effects, changes in snowfall could have significant short-term impacts on the mass balance of the region and therefore on sea levels.
Essentially, it's a question of how much snow falls in a given period. As ice falls into the sea, it adds more water, so the sea level rises. If the snowfall is light, then there is a net loss to Antarctica's ice and the sea level rise is greater. However, if the snowfall is heavy, then the ice pack builds up faster than the bergs calve, so there's a net surplus of ice and the sea level rise slows.
In the case of the Amundsen Sea Embayment, it has lost about 3,331 gigatonnes of ice since 1996 (enough to bury London to a depth of 2 km (1.24 miles)), contributing about 9.2 mm to global sea level rises. What is remarkable is that this change is not consistent. Based on models of the data collected between 1996 and 2021, the years 2009 to 2013 showed a snow drought during which the region contributed 25% more to sea level rises than in an average year. By contrast, between 2019 and 2020, heavy snowfalls resulted in the region increasing sea levels by half of normal.
"Changes in ocean temperature and circulation appear to be driving the long-term, large-scale changes in West Antarctica (sic) ice sheet mass" said Dr. Ben Davison, a researcher in Earth observation at the University of Leeds and lead author of the study. " We absolutely need to research those more because they are likely to control the overall sea level contribution from West Antarctica.
"However, we were really surprised to see just how much periods of extremely low or high snowfall could affect the ice sheet over two to five-year periods – so much so that we think they could play an important, albeit secondary role, in controlling rates of West Antarctic ice loss."
The research was published in Nature Communications.
Source: British Antarctic Survey
