As Arctic neared 2019 winter max, Bering Sea was virtually ice-free

0

  • Though yet to be called officially by scientists, Arctic sea ice extent appeared to hit its annual maximum on March 13 when it covered 14.777 million square kilometers. The 2019 max stats are among the top ten lowest on record, and well below the 1981-2010 average maximum extent of 15.64 million square kilometers.
  • One thing that stood out this winter was the extraordinarily low amounts of ice in the Bering Sea at the start of March, surpassing record lows seen in 2018 for the same dates. Seasonal ice in the Bering Sea is already known to be volatile, but it’s getting worse under climate change.
  • A new study also found something remarkable on the opposite side of the Arctic: in recent years, according to the research, Greenland has been receiving more rain, including in winter.
  • These rain events are triggering sudden, rapid ice melt and are responsible for a tremendous amount of annual runoff. Ultimately, these rains could prove catastrophic for the Greenland ice sheet, and for sea level rise.
Soaring birds in a melting Arctic. Photo on Visualhunt

After four years in a row of record low winter sea ice extent, the Arctic received a bit of a reprieve this year. This winter’s maximum — the day when sea ice extent is greatest — was likely reached on March 13, when Arctic sea ice covered 14.777 million square kilometers (5.7 million square miles). Though the National Snow and Ice Data Center has not yet officially declared the maximum, 2019 Arctic sea ice extent still remains among the top ten lowest on record for March, and well below the 1981-2010 average maximum extent of 15.64 million square kilometers (6.03 million square miles). Cold weather over much of the Arctic this winter preserved whatever ice had managed to form.

The exception was in the Bering Sea. Spanning 2 million square kilometers (772,000 square miles) between Alaska and Russia, the Bering Sea has had a rough go of it the past two years. Last winter, sea ice extent in the region plummeted. An unusually warm Autumn followed. By November 2018, when ice should have begun to reform, the Bering Sea experienced the lowest ice extent ever documented in the satellite record for that time of year.

Then the weather shifted.

“For December and the first half of January, sea ice expanded quite a bit… the ice extent never got up to average, but it was pretty close; we were almost at 90 per cent by the middle of January,” said Rick Thoman, a retired climatologist with the National Weather Service who now serves as an Alaska climate specialist at the University of Alaska Fairbanks International Arctic Research Center. “However, in the last week of January the weather pattern changed pretty dramatically.” An anticyclone system formed over Arctic Canada, with high pressure over northwestern Canada and low pressure in the Bering Sea. These two systems drew warm air into the region from the south, halting the formation of new ice while also pushing existing ice out to the north. Bad weather only exacerbated these losses.

Arctic sea ice extent in the Bering Sea and Bering Strait on March 4, 2019, a record, as compared with 2018 on the same date (the previous record) and March 2012, the year that still holds the record for the September Arctic sea ice minimum extent. Image courtesy of Neven at the Arctic Sea Ice Blog with data/maps from University of Bremen.

“I’ve counted 15 different storms that have affected the northern Bering Sea — one every three days,” Thoman said at the start of March. These storms created strong winds and wave action that had “really eaten up a lot of the ice.” From January 27 to March 3, the Bering Sea lost 373,000 square kilometers of sea ice (144,000 square miles) — an area nearly the size of Montana. According to Thoman, this will mark only the third time in the satellite record when the winter maximum in the Bering Sea was reached in January. (Winter maximum is almost always reached during March.)

The seasonal ice in the Bering Sea is already known to be volatile, but it’s getting worse under climate change. Now the ice is thin, and sometimes mushy, which means it simply can’t withstand powerful weather systems moving through, unlike thicker ice. “It just doesn’t seem like it’s as thick or as robust as it should be,” said Thoman. “The temperatures in the Bering Sea were very warm [last year] and we’re seeing the results of that now.”

Going into the summer melt season, Mark Serreze, director of the National Snow and Ice Data Center, says no one knows exactly what will happen in the Bering Sea as it depends on the vagaries of weather patterns, “but we know it’s going to be low.”

Satellite imagery of the mostly ice-free Bering Strait on February 28, 2019. Image courtesy of NASA.

Any ice issue in the Bering Sea also spells problems for the Chukchi Sea, connected via the Bering Strait to the north. Because the Bering Sea had very little ice cover in January and February, all of the sun’s energy went toward heating the ocean water rather than melting the ice on top. This means sea surface temperatures in the Bering Sea will be warmer than usual come summer, and that water flows north into the Chukchi. “This virtually assures another late freeze-up in the Chukchi, and freezing the Chukchi is a prerequisite for forming ice in the open Bering Sea. It’s a positive feedback,” said Thoman.

The loss of sea ice in the region is also creating a precarious situation for towns along the Bering Sea coast. In Gambell, Alaska, located on St. Lawrence Island, residents report only about two-and-a-half months of sea ice this winter, while also facing constant storms. The rough weather has led to non-stop swells crashing onto shore, unhindered by the sea ice. “It’s caused a tremendous amount of erosion, threatening their air strip and other town infrastructure,” said Thoman. “The whole idea that a lack of sea ice causes increased erosion is not new, but now we’re seeing it spread to more communities where it had historically not been an issue.”

The lack of sea ice is bad news for local livelihoods too. March is normally when coastal people are busy crabbing and fishing out on the ice. Under current conditions, that can’t happen.

On the other side of the Arctic, rainy weather has inundated the Greenland Ice Sheet, proving that despite the colder weather, it’s anything but business as usual in the North. These rain events – with some parts of the ice sheet now getting rain even in winter – are triggering sudden, rapid ice melt and are responsible for a tremendous amount of annual runoff. It’s believed that the Greenland Ice Sheet is losing 270 billion tons of ice every year — the majority of which stems from direct meltwater runoff. That means rains over Greenland could have a disastrous effect in the long run.

“It’s an interesting year, but what’s going on in the Bering Sea is the story right now,” concluded Serreze.

FEEDBACK: Use this form to send a message to the author of this post. If you want to post a public comment, you can do that at the bottom of the page.

A polar bear walks an ice-free Arctic shore, with fractured sea ice in the background. Photo on VisualHunt.com

This story first appeared on Mongabay

South Africa Today – Environment



This article is licensed under a Creative Commons Attribution-NoDerivatives 4.0 International License.

You may republish this article, so long as you credit the authors and Mongabay, and do not change the text. Please include a link back to the original article.

Disclaimer: The views of authors published on South Africa Today are their own and do not necessarily represent the views of South Africa Today. By viewing, visiting, using, or interacting with SouthAfricaToday.net, you are agreeing to all the provisions of the Terms of Use Policy and the Privacy Policy.