Polar Climate Change and the Arctic Oscillation in CCSM3 IPCC

Scenario Simulations

June22 2006

Haiyan Teng

NCAR/CGD

H. Teng, W. M. Washington, G. A. Meehl, L.E. Buja and G. W. Strand, 2006: Twenty-first century Arctic climate change in the CCSM3 IPCC scenario simulations, Climate Dynamics

Sea Ice Extent Sea Ice Concentration

http://nsidc.org/data/seaice_index/

Overland and Wang, 2005: The Arctic climate paradox: Therecent decrease of the Arctic Oscillation

Moritz et al. (Science 2002) review “Dynamics of recentclimate change in the Arctic”

TAS EOF1

TAS EOF2

SLP EOF1

1870-2099

PDF of the AO index (SLP EOF1)

Red: 21st centuryBlack:20th centuryA2

A1B

B1

Conclusions

• The AO is the dominant mode in the wintertime atmosphere and sea ice variability in the 1870-1999 historical runs.

• The AO shifts to the positive phase in response to anthropogenic forcing in the 21st century but the simulated AO trends are smaller than the observed.

• The AO plays a secondary role (<10% of the total variance) in the 21st century while 50%-70% of the total variances are explained by the warming trend.

Surface Temperature EOF1

Surface temperature EOF2

Sea level pressure EOF1

Questions

• How does the AO respond to the anthropogenic forcing?

• Thinning of current Arctic sea ice: triggered by the early 1990s’ positive AO?

• Climate variability under a warming trend