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Chris Mooney @chriscmooney
, 18 tweets, 4 min read Read on Twitter
1. In which I endeavor to convince you that a process you may not have heard of called “Atlantification” is a pretty big deal washingtonpost.com/news/energy-en…
2. Basically, the Arctic Ocean is weird. Well, so is the Southern Ocean, and in the same way, but let’s focus on the Arctic.
3. The thing is, it’s inverted. Colder water on the top, warmer water below it.
4. This is not what you and I usually expect when we think about the ocean, and it is not how things work in, say, the Atlantic or Pacific, where the sun heats the top layer far more than the deeper ocean, which is therefore colder.
5. But the Arctic is different because of ice. The ocean’s upper layer freezes and when ice melts, it freshens the water. (There is also glacial melt in this region that contributes freshening.)
6. This cold, fresh water layer at the surface and in the upper ocean is actually cooler than a warmer layer below it. And the cold water mostly stays on top because its freshness (lack of salt) means it is less dense and doesn’t sink.
7. But below that is warmer, salty Atlantic-sourced water, which circulates around the Arctic but doesn’t necessarily mix upward. There’s also a border region where the Atlantic waters and the Arctic waters meet, and it’s kind of in-between.
8. Anyway, this is all important because according to new research, climate change is pushing that boundary northward. nature.com/articles/s4155…
9. And in particular, it is on the verge of converting the entire northern part of the Barents Sea (north of Scandinavia, east of Svalbard) into a body with fundamentally Atlantic characteristics, rather than fundamentally Arctic ones.
10. The driver is the lack of ice, which reduces the freshness of the ocean surface – which helps the warm water mix upwards.
11. This sector of the ocean is already among the fastest warming parts of the Arctic – which is really saying something – and much of this is because of this upward-mixing of warmer, Atlantic originating water.
12.The northern Barents Sea has also been a major hotspot for sea ice loss and indeed, sports a sharp downward deviation from normal sea ice concentrations at this very moment. nsidc.org/arcticseaicene…
13. So the northern Barents Sea is being rapidly Atlantified – and this will mean, eventually, a totally different ecosystem.
14. On top of that, quite possibly, it will mean profound effects on weather, especially in Eurasia. At least if you buy the hypothesis that fast Arctic warming can in turn alter the jet stream/polar vortex and make winters very...strange.
15.(All I will say there is that while this remains debated, at least to an extent, scientists keep publishing results supporting the idea in various forms.)
16. In any case, in terms of the consequential nature of this change, I think the following quote from the study authors says it best.
17. “...the entire region could soon have a warm and well-mixed water column structure and be part of the Atlantic domain, a historically rare moment where we would witness a large body of water being completely transformed from Arctic to Atlantic type.”
18. So in terms of the world’s oceans and how we think about their physical boundaries – well, I guess you could say that in a sense, climate change is redrawing the map. /end
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