北极海冰的范围正在缩小

NEW YORK — The extent of Arctic sea ice this week shrunk to a new low in the era of satellite record-keeping that began in 1979. The increased expanse of water near the top of the world could have implications for global shipping, wildlife and even international diplomacy.

Polar bears hunt seals from sea ice, but could drown if forced to swim long distances in open water. Satellite photos released by America’s space agency, NASA, illustrate the daunting threat to such bears. An image shows the amount of Arctic Sea ice in 1979. Another shows the record minimum set this year on September 16. The shrinkage is equivalent to an area greater than Texas, an impossible distance for even the mightiest polar bear to swim.

Scientists say fossil fuels are increasing carbon emissions in the atmosphere. This not only warms the oceans, but threatens biodiversity in cold and warm waters alike.

“As we increase the carbon dioxide in the atmosphere, a high proportion, about 40 percent of that, goes back into the ocean, and so it’s increasing the acid content of the ocean and that’s threatening coral reefs,” said Ben Orlove, a Columbia University climate research scientist.

Orlove notes that the demise of coral reefs subsequently threatens fisheries around them.

Scientists at a recent symposium at Columbia University’s Earth Institute said less ice is likely to draw some shipping away from the Panama Canal. This is because a northern route, though still hazardous, reduces the distance between Europe and Asia by about 6,500 kilometers.

Anne Siders of Columbia’s Center for Climate Change Law said countries bordering the Arctic are not the only ones with interests there.

“There certainly will be interest in the Arctic from nations that don’t touch physically on the Arctic; that’s very clear for natural resources, for fishing, for a variety of reasons,” said Siders.

Energy supplies are among those reasons. Siders says China and Japan are seeking influence - so far unsuccessfully - in the Arctic Council, an international forum of eight countries that border the Arctic.

Scientists say more open water in the Arctic means more evaporation and extreme weather elsewhere. The Earth Institute’s Peter Schlosser adds that warmer water around Greenland could melt some of the island’s glaciers to the detriment of low-lying areas everywhere.

“They are impacting sea levels, for example. If you look at the tropical Pacific and island nations there, they experience sea level rise and their existence is actually threatened by that,” said Schlosser.

The Arctic is far from most of the world’s population. Scientists, however, caution that distance is no guarantee people will be spared the effects of warming in the planet’s northernmost regions.