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Dec. 31, 2013: Passengers from the Russian ship MV Akademik Shokalskiy link arms and stamp out a helicopter landing site on the ice near the trapped ship 1,500 nautical miles south of Hobart, Australia.

Andrew Peacock, Australasian Antarctic Expedition/Footloose Fotography via AP

Ice changes at Antarctica remain a mystery

  • Article by: HENRY FOUNTAIN
  • New York Times
  • January 11, 2014 - 4:18 PM

 

When a ship carrying scientists and adventure tourists became stuck in ice in the Antarctic late last month, climate change skeptics had a field day. On Twitter and other social media sites, they pointed out that a group whose journey was meant to highlight the effects of global warming was trapped by a substance that was supposed to be melting.

“Global warming idiots out of danger,” one noted when the ship’s 52 passengers were finally taken to safety after more than a week on the ice.

The episode had little connection to climate change — shifting winds had caused loose pack ice to jam against the ship — and this was far from the first time that a ship had been trapped. But sea ice cover in the Antarctic is changing, and scientists see the influence of climate change, although they say natural climate variability may be at work, too.

“The truth is, we don’t fully understand what’s going on,” said Ted Maksym, a researcher at the Woods Hole Oceanographic Institution.

Unlike the Arctic, where declines in recent decades in the ice that floats on sea surfaces have been linked to warming, sea ice in the Antarctic has increased, scientists say. Averaged over the entire Antarctic coast, the increase is slight — about 1 percent a decade. At the same time, larger increases and decreases are being seen on certain parts of the continent.

“We’re constantly struggling against that statement, that Antarctic ice is increasing,” said Sharon E. Stammerjohn, a scientist at the Institute of Arctic and Alpine Research at the University of Colorado. “It misses key changes that are happening.”

Most of the sea ice changes are occurring in an area covering about a third of the Antarctic coast, from the Ross Sea to the Bellingshausen Sea and the Antarctic Peninsula, said Paul Holland, a researcher with the British Antarctic Survey. Areas around the Ross Sea, for example, have seen large increases in ice, while in the Bellingshausen and along the peninsula, ice cover has declined sharply. (The area where the research ship became stuck, west of the Ross Sea, has had a slight increase in ice cover in the past 35 years.)

Researchers agree that the changes in those seas are related to north-south winds. That brings warmer air from the north into the Bellingshausen Sea and peninsula, pushing ice against the coast and melting some of it, and colder air from the south into the Ross Sea, which spreads the ice away from the coast and creates more of it.

Scientists say that increases in greenhouse gas concentration in the atmosphere, as well as depletion of atmospheric ozone, have changed temperature gradients from the tropics to the poles, which affects atmospheric circulation.

Whatever the explanation, much of the Bellingshausen is now ice free for long periods each summer. That allows the relatively warmer waters of the Southern Ocean to flow more freely to the more permanent ice that extends from the land in glaciers and sheets.

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