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Chris Mooney @chriscmooney
, 17 tweets, 6 min read Read on Twitter
A little over three years ago in February 2015, on my first trip to the Arctic, I took this photo of weak sea ice along the coast of the Chukchi Sea. (1; #thread)
2. This was at a time of year when sea ice was nearing its annual maximum extent, but it was oddly broken up right along the shoreline.
3. Little did I know at the time that I was witnessing the first in a string of four successive years – 2015, 2016, 2017, and 2018 -- that would be the four lowest on record for winter sea ice at its peak.…
4. But that’s the conclusion published yesterday from the @NSIDC, which found that while 2018 was not the absolute lowest peak on record – 2017 clung to that title – overall, we have seen a clustering of very low years and 2018 just adds to the list.…
5. The peak ice extent, or winter maximum, this year came on March 17, apparently, and this is what it looked like per @NASA…
6. Meanwhile, here are 2015, 2016, 2017, and 2018 in context -- all far below average, per @NSIDC
7. Just to dispel any confusion, let me just briefly explain this concept of a winter sea ice maximum. The ice naturally grows in winter and shrinks in summer. Like so:…
8. Therefore, there’s always a winter peak (when the extent is the highest) and a summer low (when it’s lowest). The problem is, both the winter peak and the summer low keep getting lower.
9. And these are clearly related – if you start from a lower peak in the winter, then naturally, as ice melts there’s the potential to go lower in summer.
10. Similarly, if you start from a low point in summer, you have to freeze a lot more ice to have a high peak in winter.
11. In this context, what really counts is not whether 2018 set a new record low for the winter peak (which it just missed) but rather that we’re seeing very low years continually.
12. 2018 in winter was an enormous 448,000 square miles below average – meaning that Arctic ice was missing an area far larger than Texas (which is 268,000 sq miles).
13. These low years have been accompanied by repeated events in which the Arctic, in winter, has shown super warm anomalies, sometimes even getting briefly above the freezing point.…
14. And while it’s contested still, some scientists continue to argue that this Arctic bizarreness is rebounding and affecting us in the mid-latitudes, including potentially influencing U.S. East Coast winter cold extremes.…
15.Having visited three times in the past three years or so, I’ve heard the people of the Arctic people speak eloquently about the dramatic changes they’ve experienced.…
16. So while 2018’s near record low may seem like a mere statistic to us, it's a lot more than that.
17. Some scientists think the middle latitudes are already experiencing these changes through our weather -- and in the Arctic itself, there’s wide recognition of a new regime and its transformational consequences. (/end #thread)
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