Ice in the Beaufort Sea is scarcer now than in early June of any other year in the satellite record, and the vast stretches of open water off Alaska has helped push the Arctic-wide sea extent to a record low for this time of the ear, according to reports from the National Snow and Ice Data Center.
The combined year-to-date melt in the Beaufort, Chukchi and Bering seas drove overall Arctic sea ice extent last month to the second-lowest for any May in the four-decade satellite record, according to most recent monthly summary from the Colorado-based NSIDC. And as of Monday, overall Arctic sea ice extent has slipped to the lowest for the date in satellite records that go back to 1979, according to NSIDC reports.
Melt in the Beaufort has been one of the dramatic turns in the Arctic spring. As of June 7, 22 percent of the Beaufort was ice-free, the most ever for that date, said Rick Thoman, climate specialist with the Alaska Center for Climate Assessment and Policy. That melt, currently about two months ahead of normal, appears headed for a continued fast pace throughout the melt season, he said. “I guess I’m expecting that the Beaufort is going to wind up being near-record low,” he said.
Exactly why the Beaufort’s ice retreat off Alaska has been so rapid and so early is unclear, Thoman said.
While air temperatures are far less important to sea-ice melt than the conditions in the water and patterns of the winds, the warm weather in northwestern Canada did speed up river breakup and did cause an earlier runoff of water from the Mackenzie River into the Beaufort, he said.
Elsewhere off Alaska, the Bering Sea had lost almost all of its seasonal ice by May 15, the second-earliest date on record, after last year’s dramatically early meltdown, according to Thoman’s calculations. He uses a melt-out threshold of 50,000 square kilometers of remaining ice — about 7 percent of normal winter maximum — as the point at which the Bering Sea is considered essentially open.
The Chukchi Sea’s melt is also nearly a month ahead of normal. The Bering and the Chukchi seas in recent years have been notable for their scarcity of ice, even in winter. The melt is now advancing faster there than in most other parts of the Arctic, said NSIDC director Mark Serreze.
“That area’s kind of leading the way. That’s where the biggest reductions have occurred,” Serreze said.
Ice loss has also been dramatic on the other side of the Arctic, along the Atlantic edges in and around the Barents said, he said. “It’s not that it’s melting. It’s not forming,” he said. There, “Atlantification” — the transformation of ocean from Arctic to Atlantic conditions — is at play there, he said.
Ice extent isn’t dwindling very quickly in one part of the Arctic, though.
“The place that is not changing much is north of the Canadian Arctic Archipelago,” he said. The tightly spaced islands are able to trap ice driven there by winds and currents, and even though the ice there is thinner than it used to be, it remains present, he said.
What happens over the rest of the melt season is now a matter of scientific speculation. The U.S. Arctic Research Commission’s Sea Ice Prediction Network is currently gathering the summer’s first detailed forecasts.
While the long-term trend is clearly downward, there are year-to-year fluctuations during the melt season that create a zig-zagged sawtooth pattern around that long-term trend. “It’s going to continue in fits and starts,” Serreze said.
Now a new study by scientists from the Max Planck Institute for Meteorology in Germany and Stockholm University in Sweden quantifies the role that weather plays in that variability around the overall downward trend. The study, published in Nature Geoscience, concludes that about 75 percent of the variability of melt rate around the long-term decline is product of weather influence from lower latitudes. The remaining 25 percent of the variability is attributable to internal Arctic forces — the rate of albedo, or solar reflection from the white snow and ice surface; clouds; water vapor; and ocean heat transfer.
That short-term variation limits prospects for year-to-year predictions of sea ice melt “and suggests that observed record lows in Arctic sea-ice area are a direct response to an unusually warm atmosphere,” the study says.
To Serreze, there is a “fixation” on the annual minimum, which is understandable in some ways. “At some point that number goes to zero. That’s when the Arctic becomes labeled ice-free” he said.
But for the ecosystem and, in some cases, the economy, the annual minimum is much less important than the loss of ice in during all seasons, he said. “It’s a year-round thing. It’s not just summer,” he said.
A separate study, published in the Journal of Geophysical Research: Atmospheres, provides a further link between Arctic sea ice and southern weather conditions. When Arctic ice melt is fast and early, particularly in the Hudson Bay and northeastern Canada region, the study finds, there are more frequent summer heat waves in the lower latitudes of the United States — extreme heat waves in the southern Plains states and oppressive heat waves in the southeastern states.
The finding is one of correlation, not necessarily that fast melt and low ice causes the heat waves thousands of miles to the south, said lead author, Dagmar Budikova of Illinois State University.
The study showed the presence of strong atmospheric warming in the spring over the Canadian Arctic and Hudson Bay regions, which contributed to early season melting, Budikova said in an email. “These local conditions would promote enhanced sea ice melting, in part I am sure through the ice-albedo-feedback mechanism,” she said. Also present in these situations is “well-developed atmospheric ridge over the area” that promotes the flow of relatively warm area from lower latitudes into the north, she said.
The study not did investigate the relative importance of local versus remote influences on melt, she said. “It is evident in our study, however, that atmospheric transport of ‘heat’ from southern latitudes coincides with earlier sea ice melt in the spring that continues into the summer months over the Hudson Bay region,” she said.