Last June-September 2016 the
Crystal Serenity, a large cruise
ship, sailed through the ice-free Northwest Passage. Days after it passed,
researchers off King William Island found the long-lost wreck of H.M.S. Terror, of Britain’s Franklin expedition
– which had gotten trapped in the ice in 1846 while searching for the passage. The
Arctic has warmed dramatically, and its ice cover has thinned and shrunk
(graph, below). That loss speeds the warming, as sunlight is absorbed by dark ocean
instead of reflected into space by ice.
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| Click to Enlarge |
Melting sea ice doesn’t
raise sea level – it’s already in the water – but melting land ice does. Mountain
glaciers are in global retreat. The total sea level rise of 8 to 9 inches since
1900 has contributed to a sharp increase in flooding along coasts. During Superstorm
Sandy, for example, floods and winds cause $68 billion in damage on the U.S.
East Coast.
The big treat is the ice
sheets covering Greenland and Antarctica. The hold enough ice to raise seas
more than 200 feet – and they’re losing it. When Earth was just a bit warmer,
125,000 years ago, they seem to have lost a lot: Sea levels were 20 to 30 feet
higher. Such a rise today would swamp coastal cities.
How Fast Can Ice Sheets Fail?
Since 2002 Greenland has
lost an average of 287 billion metric tons of ice a year, according to NASA
satellites. Antarctica is losing less, but it’s vulnerable; much of the West
Antarctica ice sheet sits on the seabed, and the floating ice shelves that
buttress it are eroding in a warmer ocean – as the calving of a 44-square-mile
iceberg into Pine Island Bay illustrates (above). A glacial collapse that would
raise sea level several feet could take centuries. Or maybe just decades.
(Summarized from National Geography Magazine, April 2017)
Verdict: Ice
is melting fast, so fast…
Lord, Give
Us Today Our Daily Idea(s)
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