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Chris Mooney @chriscmooney
, 14 tweets, 3 min read Read on Twitter
1. Much of the key climate news of late has been about sea level rise. It hasn’t been good.
2. On the one hand we have a reaffirmation of a key mechanism behind James Hansen's 2016 climate disaster study – stratification of the seas around Antarctica.
3. A new scientific report suggests that in key regions, fresh water is already inhibiting the sinking of dense ocean water in winter, leaving warm waters with more access to two of the biggest glaciers on Earth, Thwaites and Totten.…
4. The stratification mechanism works like this -- melting glaciers pour freshwater into the ocean. That freshwater interferes with the ocean’s mixing, or formation of deep water. (Water needs to be both cold and salty to sink.)
5. So surface water fails to sink, leaving the warm water layer below it with access to deep glaciers where they are most vulnerable -- at their grounding lines far below the sea surface.
6. This then becomes a feedback as those glaciers freshen the oceans more, further interfering with deep water formation, and so on and so on.
7. It’s far from clear that all aspects of Hansen’s dire scenario are coming to pass – or, critically, that they are playing out as fast as he suggested -- but scientists did just go a long way towards validating this key mechanism.
8. Meanwhile – and these two stories are highly connected – we learn that coral atoll islands far from Antarctica are in even more trouble than we thought.…
9. The islands won’t succumb to the waves right away – they are 6 or so feet above sea level – but individual major wave events will wash over them more and more, and what may go first could be their drinking water supplies.
10. Wave overwash events cause the groundwater to become more saline. If there are enough of them, undrinkable. And rising seas in turn raise the wave risk. (So do dying corals, which can no longer provide protection.)
11. How long until there is too much wave overwash and islands become ‘uninhabitable’ because you can’t find fresh water? New research goes so far as to suggest the 2030s if Antarctica is super vulnerable, but other experts, like @bobkopp, disputed that.
12. Still, the rate of Antarctic loss, even in Kopp’s own analysis, feeds right back into the rising risk of drinking water contamination in places like the Marshall Islands, Maldives, etc. And this risk does seem to start to become a serious one around mid-century.
13. So in sum – what does or doesn’t happen in Antarctica will shape lives, military decisions, and much more across multitudes of unique islands in the Pacific and Indian oceans, and beyond.
14. The really big question remains -- how soon will this all play out. Here, the picture, in the form of a mosaic of scientific studies, still isn't complete. But it has certainly given people around the world a reason to watch closely for each new piece. /end
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