Researchers from NASA and the British Antarctic Survey have published a new study that shows changes to Antarctic sea ice drift caused by changing winds are the cause of increases in Antarctic sea ice cover over the past two decades. The results help explain why Antarctic sea ice cover has increased while Arctic sea ice has seen heavy losses.

The study, published this week in the journal Nature Geosciences, used maps created by NASA’s Jet Propulsion Laboratory (JPL) from more than five million daily ice-motion measurements captured by U.S. Defense meteorological satellites over a period of 19 years. According to researchers, the maps show long-term changes to sea ice drift around Antarctica for the first time.

“Until now, these changes in ice drift were only speculated upon, using computer models of Antarctic winds,” said Paul Holland, lead author of the study and ocean modeller at the Natural Environment Research Council’s British Antarctic Survey. “This study of direct satellite observations shows the complexity of climate change. The total Antarctic sea ice cover is increasing slowly, but individual regions are actually experiencing much larger gains and losses that are almost offsetting each other overall.

“We now know that these regional changes are caused by changes in the winds, which, in turn, affect the ice cover through changes in both ice drift and air temperature. The changes in ice drift also suggest large changes in the ocean surrounding Antarctica, which is very sensitive to the cold and salty water produced by sea ice growth.”

The research shows that the increase in sea ice cover in the Antarctic is the result of larger regional increases and decreases caused by wind-driven changes. The Arctic Ocean is surrounded by land, meaning that changing winds cannot cause its sea ice to expand.

“The Antarctic sea ice cover interacts with the global climate system very differently than that of the Arctic, and these results highlight the sensitivity of the Antarctic ice coverage to changes in the strength of the winds around the continent,” said Ron Kwok, a senior research scientist at JPL.

(Image courtesy the British Antarctic Survey)