Climate Modelling Group
School of Earth and Ocean Sciences

1. PROJECT TITLE: "Analysis of the Variability of the Arctic Oscillation under Enhanced Greenhouse Warming"

Project # (for CCAF use)

S99-13-12

2. PRINCIPAL INVESTIGATOR(S):

Daithi A. Stone and Andrew J. Weaver

3. COLLABORATOR(S):

 

4. REPORT AGAINST PROJECT GOALS AND DELIVERABLES (for period ending September 30, 2000):

Substantial progress has been made towards the completion of the goals of this project. Preliminary results were presented at the 34th Annual Congress of the Canadian Meteorological and Oceanographic Society, University of Victoria (29 May - 2 June 2000). More recent results have also been described in a manuscript, Stone et al. (2000), recently submitted to the Journal of Climate and currently under peer-revision.

One of the objectives of this project is to examine changes in the variability of atmospheric modes simulated by the Geophysical Fluid Dynamics Laboratory (GFDL) coupled model under enhanced greenhouse warming. The modes of sea level pressure (SLP), such as the Arctic Oscillation, remain dominant in warmer climates, with little change in their physical structure. The modes of surface air temperature (SAT) are often related to variations in the sea ice edge, and so do not remain important since the ice retreats as the climate warms; however, those unrelated to sea ice also remain important in the warmer climates.

Another objective of this project was to evaluate the projection of the simulated climate change onto these modes. Two possible interpretations of forced climate change view it as projecting, either linearly or nonlinearly, onto the modes. The first possibility interprets the climate change as manifesting itself as a simple linear shift in the mean state of the modes. The second interprets the change as a shift of the residence frequency of the climate system in quasi-stationary regimes associated with these modes; thus while the climate system presently may reside in one of these regimes more frequently than another, in a warmer climate the opposite may occur. The analysis performed in this project of the climate change and modes simulated in integrations of the GFDL coupled model does not support the second interpretation. Instead, under global warming about half of the change in Northern Hemisphere SLP is characterised by a simple linear trend in the Arctic Oscillation, while in the Southern Hemisphere most of the change is characterised by a linear trend in the Antarctic Oscillation, supporting the first interpretation. On the other hand, changes in SAT do not conform to either interpretation.

D. Stone, a Ph.D. student supported through these funds for this project, is currently preparing to present these results at the Fall Meeting of the American Geophysical Union, San Francisco (14-19 December 2000). Results from the peer revision of the manuscript mentioned above should be available shortly, and suggested additional analysis will be performed at that time.

References:

Stone, D. A., A. W. Weaver, and R. J. Stouffer. 2000. Projection of climate change onto atmospheric modes. J. Climate, submitted.

5. ANY COMMENTS OR CONCERNS ON STATE OF PROGRESS:

None. This project is progressing on schedule and will be completed by 31 March 2001.

6. CCAF FUNDS RECEIVED, APRIL 1

TO SEPT. 30, 2000: $13,000

7. CCAF FUNDS SPENT, APRIL 1

TO SEPT. 30, 2000: $13,000

8. DO YOU FORESEE FINISHING UNDER BUDGET (CCAF FUNDS)? No

IF SO, BY APPROXIMATELY HOW MUCH? $0

9. SOURCES AND AMOUNTS OF non-CCAF FUNDS RECEIVED, APRIL 1

TO SEPTEMBER 30, 2000 (CASH AND IN-KIND):

The infrastructure and personnel support for the Climate Modelling Lab, for projects related to this CCAF initiative comes from NSERC ($180,000 in the past year). IARC funds (50K US) were used to free up Weaver's time through salary relief and have provided additional operating support. Collaboration continues with R. Stouffer at GFDL.

10. PREPARED BY: Andrew Weaver

11. DATE: Sept 20. 2000


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