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The seas between the Arctic and Atlantic oceans are a battleground between two opposing bodies of water. And it appears that the Arctic is starting to lose the war. This is happening faster than models projected, and scientists don’t quite know what the long-term impacts will be.

The rapid “Atlantification” of the Arctic Ocean is chronicled in a new Nature Climate Change study published on Monday. The study focuses on the Barents Sea, which sits just above Scandinavia and is what the researchers refer to as an “Arctic warming hotspot” and “the doorstep to the Arctic Ocean.”

That step is being overrun by warmer waters from the Atlantic. To understand how, you have to picture the structure of the sea as a layer cake. The sea ice is the frosting on top. Below that sits a layer of cold Arctic water and further below that is a layer of salty, dense (but warmer) Atlantic water. For years, the sea ice has held the whole cake together by acting as a cap over the other layers to prevent mixing in the winter. When it melts in the summer, it has performed the same function as a layer of cool, fresher water.

But sea ice has been dwindling in the Barents Sea (as well as across the Arctic) due to rising ocean and air temperatures. A previous analysis by the same scientists showed mixing and warming across the water column were taking place in the region in the 2000s, but the new paper updates that through 2016 and shows an acceleration in the trend.

“The entire water column is warming, and the Arctic Water-mass with subzero temperatures is diminishing rapidly and is now almost entirely gone,” the researchers wrote.

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The Barents tends to have a lot of sea ice come down from the high Arctic, but the new analysis shows that source of ice is declining. The decline is behind the dip in freshwater and increase in mixing.

The northern Barents Sea has so far been insulated from the shift underway and prior to this study, models have projected that any Atlanticification would occur by century’s end. The new findings throw a whole bunch of cold (or I guess warm) water on that, suggesting that Atlantification “is likely to happen much faster.”

What that means for the region and the Arctic as a whole is an open question. We’re already witnessing weird happenings in the Arctic every year at this point, from bizarre winter sea ice disappearances to heat waves at the North Pole to massive storms. Scientists are racing to understand these changes. What saltier, warmer seas mean for the ocean creatures that inhabit the region, the fisheries that have relied on them, and the future of ice are just a few more questions that need urgent attention.