Study: Warm Atlantic waters contribute to sea ice decline – “I first went to the Arctic in 1969, and I’ve never seen anything like this”Posted by Jim at Saturday, April 08, 2017
By Chris Mooney
6 April 2017
(The Washington Post) – There’s something special — and very counterintuitive — about the Arctic Ocean.
Unlike in the Atlantic or Pacific, where the water gets colder as it gets deeper, the Arctic is upside-down. The water gets warmer as it gets deeper. The reason is that warm, salty Atlantic-originating water that flows into the Arctic from the south is more dense, and so it nestles beneath a colder, fresher surface layer that is often capped by floating sea ice. This state of “stratification” makes the Arctic Ocean unique, and it means that waters don’t simply grow colder as you travel farther north — they also become inverted.
But in a paper in Science released Thursday, a team of Arctic scientists say this fundamental trait is now changing across a major part of the Arctic, in conjunction with a changing climate.
“I first went to the Arctic in about 1969, and I’ve never seen anything like this,” said Eddy Carmack, a researcher with Fisheries and Oceans Canada and one of the study’s authors. “Back then we just assumed the Arctic is as it is and it will be that way forevermore. So what we’re seeing in the last decade or so is quite remarkable.” [more]
By Nate Bauer
7 April 2017
(University of Alaska Fairbanks) – A University of Alaska Fairbanks study has determined that warmer water migrating from the Atlantic Ocean is a surprisingly powerful contributor to Arctic sea ice decline.
Research led by Igor Polyakov, a professor at UAF’s International Arctic Research Center and College of Natural Science and Mathematics, has found that Atlantic currents contribute to sea ice loss in the Arctic Ocean at a rate comparable to warming air temperatures.
“This is a very important step toward a seasonal ice-free Arctic,” said Polyakov.
The findings, outlined in the journal Science’s April 6 edition, provide a greater understanding of the complex dynamics that contribute to sea ice melt. Co-authors of the paper include UAF’s Andrey Pnyushkov, Robert Rember, Till Baumann and Vladimir Ivanov, as well as collaborators from Russia, Canada, Poland, Germany, Norway, and the United States.
The Arctic Ocean has experienced dramatic reductions in sea ice in the past decade. The Eastern Eurasian Basin has had almost no ice by the end of each summer since 2011. Circulating Atlantic waters have been considered a small factor in that decline, due to a phenomenon known as stratification.
In the Arctic, warmer and denser water from the Atlantic has normally remained beneath a colder and lighter surface layer. The greater the difference in density between the layers, the less likely they are to mix. Without mixing, the heat from the warmer water can’t come into contact with sea ice at the surface.
That has changed. Data collected by Polyakov and other researchers during the Nansen and Amundsen Basins Observational System project showed increased mixing in the Eastern Eurasian Basin, a major pathway for Atlantic water into the Arctic Ocean. That means more heat is being transferred to the Arctic sea ice on the surface.
Even before analyzing the data, the research team noticed that something was changing. They depend on solid sea ice to deploy their research buoys. During the 2015 expedition aboard the icebreaking research vessel Akademik Tryoshnikov, much of the sea ice was too rotten to support the buoys, Polyakov said. “For the first time, we had a problem finding a suitable ice floe to deploy buoys. We spent several days trying to find such a floe.”
NABOS sends comprehensive research cruises through the Arctic Ocean every two years. The NABOS project is currently planning its 2017 research cruise.
ABSTRACT: Arctic sea-ice loss is a leading indicator of climate change and can be attributed, in large part, to atmospheric forcing. Here, we show that recent ice reductions, weakening of the halocline, and shoaling of intermediate-depth Atlantic Water layer in the eastern Eurasian Basin have increased winter ventilation in the ocean interior, making this region structurally similar to that of the western Eurasian Basin. The associated enhanced release of oceanic heat has reduced winter sea-ice formation at a rate now comparable to losses from atmospheric thermodynamic forcing, thus explaining the recent reduction in sea-ice cover in the eastern Eurasian Basin. This encroaching “atlantification” of the Eurasian Basin represents an essential step toward a new Arctic climate state, with a substantially greater role for Atlantic inflows.