Global warming seems to have caused record low sea ice the past two years in the Arctic winter wonderand, known for its icy waterways and snowy scenery, NASA researchers say. The melting, they add, appears to be harming polar bears and other animals.

Scientists from the agency used satellite observations to record unusually warm wintertime temperatures in the region.

The maximum amount of sea ice in the Arctic winter has fallen by six percent over each of the last two winters, they said. This compares to just 1.5 percent per decade on average annually since the earliest satellite monitoring in 1979.

This is happening as summer sea ice continues a retreat at an average of 10 percent per decade, they added.

“This amount of Arctic sea ice reduction the past two consecutive winters has not taken place before during the 27 years satellite data has been available,” said Joey Comiso, a research scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md.

“In the past, sea ice reduction in winter was significantly lower per decade compared to summer sea ice... What’s remarkable is that we’ve witnessed sea ice reduction at six percent per year over just the last two winters, most likely a result of warming due to greenhouse gases.”


In this image, the whole of the sea surface is made of forming sea ice. (Credit: NASA)

Most scientists blame global warming on greenhouse gases, substances such as carbon dioxide emitted as a result of human activities and that collect in the atmosphere. Last June, scientists reported that the Earth seems to have experienced its hottest temperatures in 400 years in recent decades.

Comiso used a computer simulation and satellite data in the study, to be published in the journal Geophysical Research Letters this month.

If the winter ice retreat continues, the effect could be profound, especially for sea animals, he said. “The seasonal ice regions in the Arctic are among the most biologically productive regions in the world,” he added.

“For example, sea ice provides melt-water in spring that floats because of low density. This melt-water layer is considered by biologists as the ideal layer for phytoplankton growth.”

Phytoplankton is a key part of plankton, aggregates of small plant and animal organisms that float or drift in great numbers in water. “Plankton are at the bottom of the food web,” so if their concentration goes down, animals at all levels could suffer, he argued.

Scientists from NASA and the Canadian Wildlife Service also reported that the reduction in sea ice is depriving Arctic polar bears of food by shortening the spring hunting season for females. That is probably responsible for an observed weight loss in the bears, the researchers said; and the lighter the females, the less they can reproduce and feed their young.

Scientists have previously reported that the warming might also be orphaning walrus pups and forcing polar bears to cannibalism.

ABOUT THE AUTHOR

Science writer Jack Lucentini is founder and editor of the World Science science news webzine. He has worked as a staff writer at three daily newspapers, and as a freelance science writer for a range of publications including The Washington Post, Discover magazine and The Scientist magazine. He earned his bachelor's degree at Oberlin College in Oberlin, Ohio in 1993.