The demise of Arctic sea ice during stabilisation at high greenhouse gas concentrations |
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| Authors: | Jeff Ridley Jason Lowe David Simonin |
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| Institution: | (1) Met Office, Exeter, UK;(2) Vexcel, Berkshire, UK |
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| Abstract: | A climate model experiment was conducted using the HadCM3 climate model and a scenario in which the atmospheric CO2 concentration was increased over 70 years from pre-industrial concentrations to 4 times this level and then stabilised for
more than a 1,000 years. During the period of stabilisation the global atmospheric surface temperatures continued to rise
as the deep oceans adjusted towards a new equilibrium. However, even after 1,000 years this new equilibrium had not been reached.
During the first 600 years, Arctic and Antarctic winter sea ice thickness and area covered declined with a significant impact
on the global radiation budget. After this period the area of the Arctic covered by sea ice entered a 150 years period during
which time it underwent a series of oscillations. Following the oscillation the centre of the Arctic basin became ice free
throughout the year. A sensitivity experiment demonstrates that although the sea ice extent can be greatly reduced through
the artificial heating of the mixed layer, prior to the onset of the oscillatory phase the ice recovers over 15 years. Understanding
the causes of this oscillatory phase may elucidate the mechanisms of variability in the Arctic in the present climate and
in future policy relevant scenarios. We have investigated the atmospheric and oceanic forcing on the ice during the oscillatory
phase, and find that the behaviour is linked to a redistribution of Arctic Ocean heat stores. |
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