Tropical Connections to Extra-Tropical Climatic Change

The relationship between trends in tropical sea surface temperature (SST) and spring-time climatic change in the extratropical Southern Hemisphere (SH) is examined using the NCAR Community Atmosphere Model (CAM). A suite of 32-year simulations were run wherein prescribed SST conditions exhibit trends in individual ocean basins (Pacific, Indian, Atlantic, All), allowing the contribution of each region to be analysed in isolation. When forced with observed global SSTs, the model is able to realistically simulate the negative geopotential height trend over the South Pacific (Amundsen/Ross Sea regions), consistent with various reanalysis products. A similar spatial pattern of change is only reproduced in the Atlantic-forced simulations, with on-going work assessing the dynamics behind this teleconnection. Regardless of the mechanism, however, preliminary results indicate that trends observed in the tropical Atlantic may be important in understanding the observed climatic changes in the SH extratropics.