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Thursday, July 5, 2012

Peter Wadhams: When the Arctic Sea Ice Is Gone

from Sam Carana's Arctic News blog, June 27, 2012

When the sea ice is gone

How long do you think it will take for most sea ice in the Arctic to disappear? How much change in temperature you think this would result in? 

Below an educated guess from some of the members of the Arctic Methane Emergency Group

Professor Peter Wadhams
Peter Wadhams Sc.D., Professor of Ocean Physics
and head of the Polar Ocean Physics group at the
of Cambridge, U.K., researching effects
of global warming 
on sea ice, icebergs and oceans

My own view of what will happen is:
  1. Summer sea ice disappears, except perhaps for small multiyear remnant north of Greenland and Ellesmere Island, by 2015-2016.
  2. By 2020 the ice free season lasts at least a month and by 2030 has extended to 3 months.
  3. September sea surface temperatures are already elevated by 6-7 °C over continental shelves of Arctic. As shrink back continues, the newly exposed surface water over abyssal depths warms up less in a single summer (say 2-3 °C) because of deeper surface water layer (150 m) than over a shelf (50 m).
  4. The 6-7 °C warming over the shelves causes offshore permafrost to shrink back and vanish over about 10 years. During this time there is elevated methane emission from offshore and from onshore warming, and global warming rates increase by about 50%.
  5. Result is that bad effects forecast for end of century (4 °C warming worldwide, 10 °C in Arctic) actually occur by about 2060. Speed of change is catastrophic for agriculture; warfare and population crashes ensue.
  6. Late in the day, the rapidly disintegrating civilised world tries desperate technofixes for warming and resource depletion, e.g. widespread use of nuclear power (thorium cycle), geoengineering. This may work, and bring us back from the brink of destruction after heavy losses.

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