How Asymmetries Between Arctic and Antarctic Climate Sensitivity Are Modified by the Ocean

• Published in: Geophysical Research Letters
• Main Authors: Singh, H. A., Garuba, O. A., Rasch, P. J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Geophysical Research Letters 2018
• Subjects: polar climate; Arctic; Antarctic; climate sensitivity; ocean dynamics; radiative feedbacks; Pacific; Pauling; The Antarctic; albedo; Antarc*
• Online Access: http://hdl.handle.net/1828/11982; https://doi.org/10.1029/2018GL079023

We investigate how the ocean response to CO2 forcing affects hemispheric asymmetries in polar climate sensitivity. Intermodel comparison of Phase 5 of the Coupled Model Intercomparison Project CO2 quadrupling experiments shows that even in models where hemispheric ocean heat uptake differences are small, Arctic warming still exceeds Antarctic warming. The polar climate impact of this evolving ocean response to CO2 forcing is then isolated using slab ocean experiments in a state‐of‐the‐art climate model. Overall, feedbacks over the Southern Hemisphere more effectively dissipate top‐of‐atmosphere anomalies than those over the Northern Hemisphere. Furthermore, a poleward shift in ocean heat convergence in both hemispheres amplifies destabilizing ice albedo and lapse rate feedbacks over the Arctic much more so than over the Antarctic. These results suggest that the Arctic is intrinsically more sensitive to both CO2 and oceanic forcings than the Antarctic and that ocean‐driven climate sensitivity asymmetry arises from feedback destabilization over the Arctic rather than feedback stabilization over the Antarctic. H. A. S. is grateful to the Linus Pauling Distinguished Postdoctoral Fellowship, sponsored by the U.S. DOE Office of Science's Pacific Northwest National Laboratory for facilities and funding. Support for O. A. G. and P. J. R. was provided by the Regional and Global Climate Modeling Program as a contribution to the HiLAT project. The Pacific Northwest National Laboratory is operated for the U.S. Department of Energy by Battelle Memorial Institute under contract DE‐AC05‐76RL01830. All authors acknowledge the World Climate Research Program's Working Group on Coupled Modeling, which is responsible for CMIP and thank the climate modeling groups (listed in the SI and Table 1) for producing and making available their model output. For CMIP, the U.S. DOE's Program for Climate Model Diagnosis and Intercomparison provides coordinating support and led development of software infrastructure in partnership with the ...