The Evolution of Polar Climates: Forcings, Feedbacks, and Coupled Atmosphere-Ocean-Ice Dynamics

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The polar regions are among the most vulnerable to anthropogenic climate change, with observed warming over the Arctic nearly triple that over the rest of the globe. This phenomenon of rapid high--latitude climate change, polar amplification, is evident over the Arctic in nearly all climate model simulations, and has been attributed to local radiative feedbacks (associated with both sea ice loss and the stability of the polar atmosphere) and changes in energy convergence by the atmosphere and ocean. This rapid rate of climate change in the polar regions has implications for global sea level, marine ecosystems, and extrapolar atmospheric circulation patterns, with anticipated societal impacts on coastal habitability, fishery productivity, and extreme weather, among others. The polar regions release much more energy to space than what they absorb from the sun, in effect acting as cooling radiator fins for the planet. This functionality, in turn, is made possible by the large--scale transport of extrapolar energy by the atmosphere and oceans into the polar regions. In a changing climate, changes in the cooling efficiency of the polar radiator fins depend on radiative feedbacks and changes in energy transport, which also affect polar and extrapolar climatology. In the proposed research program, I will investigate the evolving relationship between top--of-atmosphere polar energy loss, polar radiative feedbacks, and changing (atmosphere and ocean) energy convergence into the polar regions over a variety of time scales. Using models, observations, and applied mathematical techniques, we focus on the following objectives: 1. To quantify the temporal evolution of polar top--of--atmosphere energy loss with greenhouse gas forcing, and co--evolving contributions from radiative feedbacks and energy transport changes. 2. To understand Bjerknes compensation of atmospheric and oceanic energy transport into the high latitudes by identifying dynamic mechanisms of coupled energy transport adjustment. 3. To assess the relationship between fluctuations in polar top-of-atmosphere energy loss with natural variability and with forced climatic change. 4. To quantify the predictive power of sea ice in determining the polar climate state, top-of--atmosphere energy loss, radiative feedbacks (other than ice--albedo), and energy transport adjustments. 5. To assess the extrapolar impacts of polar climate change through a framework of varying regional forcings, radiative feedbacks, and atmospheric and oceanic energy transport adjustments. This research program will expand upon my prior work polar climate change through a lens of interacting local feedback mechanisms alongside adjustments in large--scale atmosphere--ocean coupled dynamics. More broadly, it will establish a framework for greater understanding and prediction of polar and extrapolar climate change, with particular relevance for climate change impacts, adaptation, and mitigation in the Canadian Arctic.