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The Demise of the Arctic Sea Ice

The Demise of the Arctic Sea Ice. Jeff Ridley David Simonin Jason Lowe. Climate Change. HadCM3 Climate at 4xCO2 2% per year increase in CO2 for 70 years Stabilise at 4xCO2 for 1000 years Global temperature rise of 5 ° C THC decreases by 35% but recovers to just 10% down

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The Demise of the Arctic Sea Ice

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  1. The Demise of the Arctic Sea Ice Jeff Ridley David Simonin Jason Lowe

  2. Climate Change • HadCM3 Climate at 4xCO2 • 2% per year increase in CO2 for 70 years • Stabilise at 4xCO2 for 1000 years • Global temperature rise of 5°C • THC decreases by 35% but recovers to just 10% down • Precipitation over Arctic and river runoff up by 20% • Greenland runoff from surface melt 10% of total runoff

  3. 12 10 8 6 4 2 0 Arctic ice area (x 106 km2) Climate at 4xCO2

  4. Basic state 4xCO2 Basic state 1xCO2 High state Low state Annual cycle

  5. Possible Causes • Change in atmospheric circulation • but, pressure system constant- no change in AO • Change in surface forcing • but, cloud cover increase compensates for ice decline • Change in THC and ocean heat transport • THC variable but no shift in regime • Internal redistribution of oceanic heat

  6. Ocean Warming Cross-section across pole along 45° longitude Degrees warming per 1000 years

  7. Arctic Ocean Temperature at 100m 1xCO2 4xCO2

  8. Correlation between 90m ocean temperature and sea-ice cover

  9. Ocean time series (Beaufort Gyre) Ice Concentration 20 50 120 Depth (m) 300 650 -2 0 2 4 6 8 Ocean Temperature (°C)

  10. Ocean Temperatures in Beaufort Gyre 200m depth Temperature (°C) Ice fraction 90m depth Time

  11. Summary • Climate forcing reduces ice area primarily by surface melt • Halocline layer is very stable and does not warm • Large variations in heat transport in Beaufort Gyre break down Halocline insulation • Once broken the ocean heat flux removes remaining ice

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