the demise of the arctic sea ice
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
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The Demise of the Arctic Sea Ice
Jeff Ridley
David Simonin
Jason Lowe
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Climate Change
HadCM3 Climate at 4xCO22% per year increase in CO2 for 70 yearsStabilise at 4xCO2 for 1000 yearsGlobal temperature rise of 5°CTHC decreases by 35% but recovers to just 10% downPrecipitation over Arctic and river runoff up by 20%Greenland runoff from surface melt 10% of total runoff
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12
10
8
6
4
2
0
Arc
tic ic
e ar
ea (
x 10
6 k
m2)
Climate at 4xCO2
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Basic state 1xCO2 Basic state 4xCO2
High state Low state
Annual cycle
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Possible Causes
Change in atmospheric circulationbut, pressure system constant- no change in AO
Change in surface forcingbut, cloud cover increase compensates for ice
declineChange in THC and ocean heat transport
THC variable but no shift in regimeInternal redistribution of oceanic heat
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61 73 86 82 69
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
Dep
th (
m)
Latitude
TREND
0.5
1
1.5
2
2.5
3
3.5
4
x 10-3
Ocean Warming
Cross-section across pole along 45° longitude
Degrees warmingper 1000 years
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Arctic Ocean Temperature at 100m
1xCO2 4xCO2
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Correlation between 90m ocean temperature and sea-ice cover
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-2 0 2 4 6 8
Ocean Temperature (°C)
20
50
120
300
650
Dep
th (
m)
Ice
Con
cent
ratio
n
Ocean time series (Beaufort Gyre)
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Tem
pera
ture
(°C
)
Time
Ocean Temperatures in Beaufort Gyre
200m depth
90m depth
Ice fraction
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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