While climate change has impact on Antarctic sea ice, the vice versa is also true with scientist showing that changes in sea ice cover at the southern pole also plays a major role in regional as well as global climate variability.
Published in journal Nature, the study points out that almost all climate change models have seen Antarctic ice sheets as just mere objects that do not play a major role in climate variability. This, scientists say, is a major issue because it isn’t just a lump of ice sitting there at the poles, but instead it is dynamic and has a cascading effect on the climate system in the region as well as across the globe.
Lead author Pepijn Bakker with the MARUM Center for Marine Environmental Studies at the University of Bremen in Germany, Andreas Schmittner, a climate scientist in Oregon State’s College of Earth, Ocean, and Atmospheric Sciences and co-author on the study and team point out that the Antarctic ice sheet has been everything else other than being static and has undergone changes over the course of last 8,000 years.
Sediment cores from the sea floor around Antarctica contain sand grains delivered there by icebergs calving off the ice sheet. The researchers analyzed sediments from the last 8,000 years, which showed evidence that many more icebergs calved off the ice sheet in some centuries than in others. Using sophisticated computer modeling, the researchers traced the variability in iceberg calving to small changes in ocean temperatures.
Researchers point out that there is natural variability and the dynamism involved with Antarctic ice sheet just like other natural phenomenon including the Pacific Decadal Oscillation, or El Niño/La Niña, but the timescale is in centuries and hence we are not able to perceive these changes. While the changes are small, they bring about significant changes to temperatures. With increase in ocean temperatures, we see more and more melting of ice and this melting causes more and more icebergs to calve off the ice sheet.
Melting of ice and increasing number of icebergs cause more and more fresh water to be added to the Southern Ocean during high temperature regimes. This effectively means that cold water is making way into warmer oceans and thereby reducing the salinity as well as reducing the surface temperatures, at the same time, stratifying the layers of water.
With water getting colder, there is greater possibility of freezing and hence despite warmer overall temperatures, more and more ice is formed. The discovery may help explain why sea ice has expanded in the Southern Ocean despite global warming, the researchers say.
The same phenomenon doesn’t occur in the Northern Hemisphere with the Greenland Ice Sheet because it is more landlocked and not subject to the same current shifts that affect the Antarctic Ice Sheet.
Scientists estimate that if the entire Antarctic Ice Sheet were to melt, global sea levels would rise some 200 feet.