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In a warming world, Alaska's icy Bering Sea bucks the trend

The Renda makes its way through Bering Sea ice, bringing winter fuel to Nome in 2012. The slight growth in Bering Sea ice between 1979 and 2012 stands in contrast to the substantial loss of summer sea ice in the Arctic Ocean, according to a new report. U.S. Coast Guard photo

Like a wayward superstorm in a warming world comes this curveball of an observation: The frigid Bering Sea at the Arctic Ocean’s door has gotten colder and icier in recent decades.

That’s according to scientists at the Alaska Climate Research Center who reviewed 33 years of sea ice records in the Bering Sea, the body of water between Russia and Alaska where the ice melts each spring and begins forming again in October.

The growth in Bering Sea ice between 1979 and 2012 was small, but it stands in stark contrast to the substantial loss of summer sea ice in the Arctic Ocean to the north, according to the report. 

“(That) is in strong contrast to the Arctic Ocean, where a substantial decrease in sea ice has been observed, accompanied by higher temperatures,” the report said.

It’s no secret that the Bering Sea, home to some of the nation’s most valuable fisheries, has been nippy in recent years. Two years ago, the sea ice famously locked out crab fishermen and necessitated a fuel delivery using international icebreakers designed to ensure Nome could keep its heat on all winter.

To get a long-term view, researchers reviewed microwave satellite imagery of the sea ice forming in autumn and moving south as winter progressed, becoming thickest in March. 

The ice cover was “pronounced” in four of the 33 years, including 1992, 1999 and 2009. Ice was thickest in 2012, covering an average of 109,000 square miles, an area slightly larger than Colorado.

Those heavy ice years helped pull up the overall average during the study period.  

Meanwhile, there wasn’t much variation in years when the sea ice coverage was less than normal. It regularly plummeted to around 55,000 square miles, an area about the size of New York state.

Increasing Bering Sea ice has made life busier at the National Weather Service’s ice desk in Anchorage, with more calls coming in from mariners hoping to wend their way through frozen mazes

The ice desk crunched data between 1986 and 2012 to determine the ice extent around St. Paul Island in the southern Bering Sea as a measuring stick of ice cover.

It was iciest around the island in 2012, with 113 days of sea ice touching the island. The second highest year came in 2010, with 100 days of ice, and in 2013, with 90 days of ice.

Becki Legatt, an ice meteorologist, could not say whether Bering Sea ice has increased in the 26-year period reviewed by the National Weather Service.

One complication, she said, is that the data looks only at St. Paul Island, about 800 miles west of Anchorage. In recent years, that satellite data has improved, offering greater detail.  

“Their study is all-encompassing of the Bering Sea,” she said, referring to the climate research center report. “The numbers I’m providing you are one pinpoint location.”

Researchers behind the climate center’s study are Gerd Wendler, L. Chen and Blake Moore, the same team that reached another surprising conclusion on climate change -- that readings at 19 of the 20 Alaska weather stations showed that the state had cooled during the first decade of the 21st century.

Their study noted that the 10-year cooling period came on the heels of a longer warming trend across Alaska. That long-term trend is in line with theories about climate change and rising global greenhouse emissions, they noted.  

To explain the increased Bering Sea ice and the cooler decade in Alaska, the researchers point to the same culprit: the Pacific Decadal Oscillation.

One effect of the oscillation is to weaken the Aleutian Low, a low-pressure center above the Aleutian Islands. The weakened low meant polar storms that raked Alaska from the north lingered longer. That left the state, and the Bering Sea, chillier.

Whether that pattern will continue is uncertain. In 2013, the center reported that temperatures statewide were slightly warmer than normal. On the other hand, St. Paul in the Bering Sea was cooler than normal in 2013.

So far, 2014 has been extremely warm. Alaska slogged through a stunning stretch of heat in January, a month the research center called “absolutely an amazing departure” from what’s normal in such a huge state, with 20 National Weather Service stations reporting above-average temperatures for the month, seven of them by 15 degrees or more. 

So far, Bering Sea ice formation is below normal, according to officials at the National Weather Service ice desk. And, so far, no ice has touched St. Paul this year.

That’s not unusual, said Legatt. On eight occasions between 1986 and 2012, the sea ice edge never reached St. Paul’s coast for an entire year. The last time that happened was 2005.

“It’s cyclic and depends on weather patterns across the Bering Sea,” she said. “A warmer air mass or southerly push delays the ice from coming down on its southward progression. That happened in January.” 

Contact Alex DeMarban at alex(at)alaskadispatch.com.