This is a posting about Bering Sea Ice. This past melt season is more or less over and so when it comes to discussing the Bering Sea Ice, the point is that there is none, it is all gone. You might expect this to be the norm at the end of the ice melt season and no different than any other year. However, a new study reveals that this is not at all normal, but instead is very exceptional. To quote the well-worn phrase, we live in “interesting” times.
There is a new paper that established some good solid historical context for us.
Let’s take a look
Study: High sensitivity of Bering Sea winter sea ice to winter insolation and carbon dioxide over the last 5500 years
Published on Sep 2, 2020 within Science Advances, it describes the results of a study conducted by researchers based at the University Of Alaska, Fairbanks.
What did they do?
Sitting in the Bering Sea is a small island called St. Matthew Island. They went there and drilled peat cores. These could then be analysed. That enabled them to estimate sea ice extent in the region for the past 5,500 years.
“It’s a small island in the middle of the Bering Sea, and it’s essentially been recording what’s happening in the ocean and atmosphere around it,”
…said lead author Miriam Jones, a research geologist with the U.S. Geological Survey. Jones worked as a faculty researcher at the University of Alaska Fairbanks when the project began in 2012.
For context, here is an image from the paper that shows you where the island is located, and the location on the island where they obtained samples.
What did they discover?
The researchers determined that modern ice conditions are at remarkably low levels.
“What we’ve seen most recently is unprecedented in the last 5,500 years,” said Matthew Wooller, director of the Alaska Stable Isotope Facility and a contributor to the paper. “We haven’t seen anything like this in terms of sea ice in the Bering Sea.”
Jones said the long-term findings also affirm that reductions in Bering Sea ice are due to more than recent higher temperatures associated with global warming. Atmospheric and ocean currents, which are also affected by climate change, play a larger role in the presence of sea ice.
How exactly did They use Peat Samples to measure historic Sea Ice?
The ancient sea ice record comes in the form of changes in the relative amounts of two isotopes of the element oxygen— oxygen-16 and oxygen-18. The ratio of those two isotopes changes depending on patterns in the atmosphere and ocean, reflecting the different signatures that precipitation has around the globe. More oxygen-18 makes for an isotopically “heavier” precipitation, more oxygen-16 makes precipitation “lighter.”
By analyzing data from a model that tracks atmospheric movement using the isotopic signature of precipitation, the authors found that heavier precipitation originated from the North Pacific, while lighter precipitation originated from the Arctic.
How do you confirm that this is correct?
That connection has been confirmed though sea ice satellite data collected since 1979, and to a smaller extent, through the presence of some microorganisms in previous core samples.
A “heavy” ratio signals a seasonal pattern that causes the amount of sea ice to decrease. A “light” ratio indicates a season with more sea ice.
UAF’s Alaska Stable Isotope Facility analyzed isotope ratios throughout the peat layers, providing a time stamp for ice conditions that existed through the millennia.
This is what reveals that right now we are at an all-time low.
Captain Cook and the wall of sea ice
It does remind me of a part of Captain Cook’s journal. He sailed North and was probing for a passage through, but never found one. All he encountered was a wall of sea ice in July 1779.
Here we are now and conditions are very different, no such wall of sea ice exists anymore.
Implications of the Study
Lead author Miriam Jones said the long-term findings also affirm that reductions in Bering Sea ice are due to more than recent higher temperatures associated with global warming. Atmospheric and ocean currents, which are also affected by climate change, play a larger role in the presence of sea ice.
“There’s a lot more going on than simply warming temperatures,” Jones said. “We’re seeing a shift in circulation patterns both in the ocean and the atmosphere.”
Although the Bering Strait throughflow may be relatively small it can have a disproportionate influence on heatflux into the Arctic Ocean basin. Enhanced winds originating from the North Pacific could amplify Arctic Ocean sea ice decline via increasing winds from the south. Simultaneously, the increased frequency and duration of winter cyclones in the Arctic have led to the large reductions in freezing degree days in Arctic Ocean winters. The loss of sea ice can also increase coastal erosion and increase land temperatures that result in permafrost thaw.
(Posting has been partially sourced from materials provided by the University Of Alaska, Fairbanks)
The paper is open Access and may be found here.