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.