Reduction due to snowfall still less than increase due to melt
Global warming brings more snowfall to Antarctica, causing reduction in sea level
As the average global temperature rises, the Antarctic ice sheet is melting, causing sea level to rise. However, a study conducted by polar researchers from Utrecht University and their international colleagues has discovered that a rise in temperatures also results in an increase in snowfall, resulting in a slight reduction in sea level. The results of their research will be published in today’s issue of Nature Climate Change.
“Warmer air can hold more water vapour, so clouds can carry more snow from the ocean to the ice sheet”, explains Dr. Stefan Ligtenberg, polar researcher at Utrecht University. The study published today shows that for each degree of temperature increase, approximately five percent more snow will fall on Antarctica. “That may not sound like much, but since Antarctica is so big, it means a 0.3 mm reduction in sea level each year, which is 10 percent of the current rise in sea level.”
Warmer air can hold more water vapour, so clouds can carry more snow from the ocean to the ice sheet.
More than 20,000 years
The study used both ice core samples and climate model simulations. Ice cores hold an excellent record of the history of the climate, comparable to the rings of a tree. A thick or thin layer of ice is an indication of how much snow fell in that year. Ice cores also allow researchers to reconstruct the date and the temperature at the time the snow fell using air bubbles in the ice. “Over a period over more than 20,000 years, our observations based on the ice cores and climate models all show that a degree of temperature increase results in five percent more snowfall”, explains Ligtenberg.
However, it is unlikely that the extra snowfall on the Antarctic ice sheet will make up for the amount of melt water released into the oceans. “More and more studies show that the ocean has a major influence on the melting rate of the ice sheet, and that ocean water is also becoming warmer”, according to one of the co-authors of the article, Utrecht University’s Professor of Polar Meteorology Michiel van den Broeke. Unfortunately, scientists still do not know enough about the interaction between glaciers and the ocean to make an accurate estimate for the coming century. “It is very probable that the rate of melting will be higher, and perhaps much higher, than the extra snowfall”, posits Van den Broeke.
More and more studies show that the ocean has a major influence on the melting rate of the ice sheet, and that ocean water is also becoming warmer.
Floating ice shelves
The Antarctic ice sheet is an average of two kilometres thick, and contains enough ice to raise global sea level by 58 meters. Over the past few years, several floating ice shelves have broken off due to global warming, causing the land ice to flow more rapidly into the sea. Scientists expect that this trend will continue as the average global temperature continues to rise.
Antarctic accumulation increases with atmospheric warming, Katja Frieler, Peter U. Clark, Feng He, Christo Buizert, Ronja Reese, Stefan R. M. Ligtenberg*, Michiel R. van den Broeke*, Ricarda Winkelmann and Anders Levermann, Nature Climate Change, Monday, 16 March 2015. (* Affiliated with Utrecht University)
This research was funded in part by the NWO’s Netherlands Polar Programme and the EU project Ice2sea. Ice2sea is a cooperative effort by 24 European research institutes with the goal of improving the projections of future sea level increases as a result of melting land ice.
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