Annular Variability and Change

John C. Fyfe

Canadian Centre for ClimateModelling and Analysis

Acknowledging

• Boer and Flato

• Monahan, Ambaum, Stephenson, North, Lorenz and Teng

• Saenko, Zickfeld, Eby, Spence, Montenegro, Weaver, England and Stone

Arctic Oscillation

Arctic Oscillation

Antarctic Oscillation

• Model has realistic annular modes, with positive trends under forced change

• Model does not suggest stratospheric involvement

Conclusions

Main Directions Since 1999

• Improving our basic understanding of the annular modes

• Assessing the impact of annular trends on the Southern Ocean

Analog Device for Climate Change

Climate Variability in the Past

Climate Variability in the Future

X

The Southern OceanAnt

arct

ica

Antarctic Oscillation

ZonalWindStress

ACC

Böning et al., Nature Geoscience, 2008

Winds Strengthen

Isopycnals Steepen

Eddies Strengthen

Isopycnals Flatten

But eddies arenot resolved in GCMs

ACC Transport with Resolution

55ºS

Ant

arct

ica

CO2

uptake

DIC removal

CO2

outgassing

DIC

sup

ply

westerlies

Human CO2

emissions

Air-to-Sea Flux of CO2

Out

gas

Upt

ake

Le Quére et al., Science, 2008

Adapted from Gille, Science, 2002

Conclusions

• Models predict intensifying ACC

• Models predict more carbon uptake

• Warming is attributed to human activity

Annular Variability and Change

John C. Fyfe

Canadian Centre for ClimateModelling and Analysis