arctic sea ice cover september 2005 nasa. sea ice extent march 2006 maximum september 2006 minimum...
TRANSCRIPT
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ARCTIC SEA ICE COVERSeptember 2005
NASA
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SEA ICE EXTENTMarch 2006
MaximumSeptember 2006
Minimum
NEW RECORD!
2006: At or near record minimum in summer and winter
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SEA ICE EXTENT
Max. Extent: 2.5% per decadeMin. Extent: 8.9% per decade
1979-2006: Decreasing trend
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UCAR, Holland et al., 2006
The Road Ahead?
Ice-free summers in foreseeable future
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SEA ICE COVERaka ‘The Great Integrator’
Ocean heat flux
Solar radiation
THERMODYNAMICSIce grow, melt and decay
Ocean stress
Wind stress
DYNAMICSIce motion
Reflects impact of atmospheric and oceanic forcing
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Arctic Oscillation (AO)Two Dominant Regimes
• Colder winter temperatures• Strong Beaufort Gyre
• Warmer winter temperatures• Transpolar Drift Stream
sweeps ice out of Arctic Ocean
Negative AO Positive AO
ICEGAINS
ICELOSES
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Atmospheric Oscillation (AO)
Strong positive pattern dominated from 1989 – 1996Favors loss of sea ice
More neutral pattern from 2000 - 2006Opportunity for recovery
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Arctic Surface Air Temperature1900- 2006
Arctic-wide, annual averaged SAT anomalies (60 – 90°N) over land
1980-present: Warming trend
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Warming: Arctic trend consistent with global trend
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• March-May temperature anomaly composites • Relative to a 1968-1996 base period
SURFACE TEMPERATURE
Despite shift, positive (warm) anomalies remain over the entire Arctic
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Southeastern Bering Sea continental shelf mooring
OCEANTemperature
2006: Significant cooling compared to previous 6-years
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• Anomalies relative to EWG climatology (1950-1980s)
• NPEO surveys & J-CAD
Morison et al., 2006a
OCEANNorth Pole Region
2000-2005:
Relaxation to near pre-1990 climatology
2000
2005
Salinity Temperature
Temperature & Salinity
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2006 Arctic Report CardSea Ice Cover
• Arctic Oscillation
• Surface Temperature
• Ocean Temperature
Why continued decrease in extent?
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Absorbedsunlight Lower albedo
Melting
Absorbedsunlight
Melting
Lower albedoAbsorbedsunlight
Melting
Lower albedo
+
++Positive
Feedback Cycle
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Rigor and Wallace, 2004
Sep 2006
Canada
Alaska
Russia
Older, thicker ice
Sep 1987
Younger, thinner ice
SEA ICE AGE(Think thickness)
1988-1990: Precipitous decrease in thick ice
OW 0 1 2 3 4 5 6 8 10+ Years
Age:
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PERENNIAL SEA ICEOlder, thicker ice
1950 1960 1970 1980 1990 2000 20102.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
Year
Modeled QuikScat
Per
enni
al ic
e ar
ea (
106 k
m2 )
Rigor & Nghiem
Significant decrease in older ice
Strong & Persistent Positive AO
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Sea ice cover susceptible to loss
Strong & PersistentPositive AO
(Less sea ice)
+Rising GlobalTemperature
Absorbedsunlight Lower albedo
Melting
+
++
Strong Positive Feedback Cycle
+
Confluence of Events…
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State of the Arctic Sea Ice Cover
Summary• System under stress• Destabilization?
Arctic Oscillations Index
Through mid - 1990s:AO index effective predictorof trends in sea icecharacteristics
1989-1996: Strong positive AO2000s:
• AO shifted back to more neutral state• Sea ice not following suit
– Continued reduction in sea ice extent – Continued reduction in amount of older, thicker ice
Will system rebound?or
Has a ‘tipping’ point been reached?
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International Polar Year
http://www.ipy.org/
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IMPACT OF IPY2007-2008
June 2006
34 Platforms Reporting
May 2007
>150 Platforms Reporting