Climate change may be melting the Arctic, but the sea ice coverage in the Antarctic is looking better than ever. However, new research suggests the reason behind the phenomenon is the melting of Antarctica’s ice shelves -- so basically, the climate is robbing the land-based Peter to pay the ocean-based Paul.
Over the past few years, Arctic sea ice has been shrinking, with a record low reached last year. This year’s maximum, reached in mid-March, was the sixth-lowest on record, suggesting it’s going to be another thin year. But conditions are very different at the opposite pole, where sea ice has been expanding by about 1.9 percent each decade since 1985.
"Sea ice around Antarctica is increasing despite the warming global climate," Royal Netherlands Meteorological Institute scientist, Richard Bintanja, told Reuters. "This is caused by melting of the ice sheets from below.”
In a new paper in the journal Nature Geoscience, Bintanja and his colleagues say their models show that plumes of colder, fresher water melting off of the Antarctic ice shelves is helping expand the local sea ice.
“Melt water from Antarctica’s ice shelves accumulates in a cool and fresh surface layer that shields the surface ocean from the warmer deeper waters that are melting the ice shelves,” the authors wrote.
The fresh water from the melted ice shelves naturally sits on top of the denser saltwater. The researchers’ computer models showed that the cool and fresh water sitting on the surface does lead to expanded Antarctic sea ice during autumn and winter.
“This powerful negative feedback counteracts Southern Hemispheric atmospheric warming,” the authors wrote.
Though they’re both at the ends of the earth, the Arctic and the Antarctic are very different beasts. The Arctic is an ocean nearly completely surrounded by land, so its sea ice tends to not move around as much.
Antarctica, meanwhile, is a single land mass surrounded by open ocean, so ice floats around more, often ending up in warmer waters to the north.
“As a result, almost all of the sea ice that forms during the Antarctic winter melts during the summer,” the National Snow and Ice Data Center says.
Other scientists think that the behavior of Antarctic sea ice can be attributed to other explanations. Paul Holland, of the British Antarctic Survey, said in a statement provided to the U.K.-based Science Media Center, that he’s sticking with his work showing that climate change has shifted the winds to blow ice away from the coast. While the protective effect of melt water contributes to the phenomenon, Holland thinks it’s a less significant factor.
“Changes in the wind change the ice cover by both blowing the ice around directly, and by carrying colder or warmer air masses over the ocean, leading to more or less freezing,” Holland said.
Emily Shuckburgh, another scientist from the British Antarctic Survey not affiliated with the current study, said the research paper overall illustrates the “fascinating and subtle interactions” between air, wind, ice and ocean.
“It has long been known that ‘global warming’ is a vast oversimplification of the changes that might be expected from increased greenhouse gases,” Shuckburgh said. “Unusually cold weather in the UK and increasing sea ice in parts of Antarctica are both examples of disruption to our climate that may in fact be a symptom.”
SOURCE: Bintanja et al. “Important role for ocean warming and increased ice-shelf melt in Antarctic sea-ice expansion.” Nature Geoscience published online 31 March 2013.