Researchers testing ice thickness in the Arctic in August. Much of the ice in the region appears to be thinner than normal. Credit Esther Horvath
After a season that saw temperatures soar at the North Pole, the Arctic has less sea ice at winter’s end than ever before in nearly four decades of satellite measurements.
The extent of ice cover — a record low for the third straight year — is another indicator of the effects of global warming on the Arctic, a region that is among the hardest hit by climate change, scientists said.
“This is just another exclamation point on the overall loss of Arctic sea ice coverage that we’ve been seeing,” said Mark Serreze, the director of the National Snow and Ice Data Center, a government-backed research agency in Boulder, Colo. “We’re heading for summers with no sea ice coverage at all.”
Dr. Serreze said that such a situation, which would leave nothing but open ocean in summer until fall freeze-up begins, could occur by 2030, although many scientists say it may not happen for a decade or two after that.
The melting of sea ice does not raise sea levels, but loss of ice coverage can disrupt ecosystems. For example, it can affect the timing of blooms of phytoplankton, the microscopic organisms at the bottom of the ocean food chain.
Less ice coverage also means that there is more dark ocean to absorb more of the sun’s energy, which leads to more warming and melting in a feedback loop called Arctic amplification.
The data center said on Wednesday that sea ice in the Arctic had reached maximum extent, of about 5.5 million square miles, on March 7. That is an area nearly twice the size of Australia, but about 470,000 square miles less than the average maximum from 1981 to 2010.