The Arctic Sea Ice cap, which shields 2 percent of the Earth’s surface from summer sunlight up there, has shrunk 70% in its September volume in the last dozen years alone, reports Ramez Naam at Climate Progress via Scientific American. The first so-called “ice-free summer” will refer to no ice in September, but as more ice melts, the remainder melts ever faster, since ice loss increases the heat absorbed from sunlight by the surrounding darker waters. At current melting rates, this thermal shield would be totally gone by 2026, especially from late May through July, when the sun shines all the time, with the ice shield reflecting away 5-6 times the sunlight that bombards the Arctic in September. But because the rate is accelerating, this shield will disappear sooner. This ice loss will have a far bigger effect on the region and planet than just September ice loss. Indeed, climate scientist Peter Wadhams, leader of the Global Oceans Physics Program at Cambridge University, has calculated that the total increase in absorbed heat will roughly double the warming of the planet, as a whole.
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Source:
http://thinkprogress.org/climate/2012/09/24/894511/arctic-sea-ice-what-why-and-what-next/
