Will polar bears survive shrinking ice?
Source: NOAA
A new climate study predicts polar ice north of Alaska will retreat hundreds of miles further offshore by mid-century, setting in motion changes in the ocean food chain and endangering marine mammals like polar bears.
The study, to be published Sept. 8 in Geophysical Research Letters, found that sea ice extent would decline by more than 40 percent before the melt season of 2050, compared with a base period of 1979-99.
The work was completed by oceanographer James Overland from the Pacific Marine Environmental Laboratory and Muyin Wang, a meteorologist at the Joint Institute for the Study of the Atmosphere and Ocean.
The startling announcement, covered in a story by the Associated Press, comes amid the most extraordinary summer meltdown in history. Sea ice extent during the last weeks of August and first days of September covered the smallest area ever observed by satellites.
This Perfect Melt is expected to set new all-time records during the next two weeks, according to the fall melt countdown by the National Snow and Ice Data Center.
While current ice melt may be the floating floe equivalent of weather, the climate study takes a long view and tries to apply lessons learned with the increasingly sophisticated battery of supercomputing models.
A world where ice once retreated 40 to 50 miles offshore will be replaced by one with ice far beyond the horizon — far beyond the shallow productive waters so important to fish, marine mammals and birds.
“Now we’re talking about 300 to 500 miles north of Alaska,” Overland told the AP.
A story posted by NOAA online has more details:
“We wanted to assess how much confidence we can have in regional projections of sea ice from the 20 computer models used in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report,” said Overland.
“Our purpose was to first ensure that our models could replicate observations of the baseline conditions during the 1979-1999 period before considering 21st century projections. Our results present a consistent picture: there is a substantial loss of sea ice for most models by 2050.”
Source: NSIDCProjections in the IPCC report show summer sea ice loss throughout the Arctic Ocean north of Alaska, Canada and Asia. Sea ice loss is also seen during winter in the seasonal ice zones of the more southern Bering and Barent seas, and the Sea of Okhotsk. The models show no ice loss in the Baffin Bay region, west of Greenland.
“These seasonal ice zones have large variability on annual and decadal time scales,” said Wang. “Projections of sea ice are important as there will be impacts on humans and other ecosystem components.”
The authors note that loss of ice has major impacts on marine ecosystems, transportation, and feedbacks to the larger climate system. For example, the light-colored ice reflects the sun’s warming rays; the dark water absorbs that heat. Less ice to reflect the heat means more water to absorb the warmth.
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