Oral

IAMAS

JMP10 - Ocean-Atmosphere Mechanisms of Climate Variability, Change and Predictability

Arctic Amplification as the Most Excitable Mode Intrinsic to the Coupled Climate System

The Arctic amplifed warming may be the most robust feature of climate change response to relatively uniform greenhouse gas forcing across climate models. The origin of this robustness is not well understood. We develop a pattern-aware feedback framework for interpreting the forced climate response using a series of Green's function experiments with forcing perturbations at each representative location on the globe. A comprehensive linear response function (CLRF) of the climate system can be estimated from the experimental data, delineating the effects of energy diffusion in the ocean and atmosphere and the pattern-aware feedbacks from radiatively active processes such as albedo, lapse rate, clouds, etc. The CLRF can then be decomposed into forcing-response mode pairs that capture the nonlocal effects and teleconnections in the climate and the associated feedbacks. The mode decomposition of the CLRF reveals that Arctic amplified warming is the most excitable mode of the climate system, and thus the most robust to noise and model uncertainties. The mode perspective also provides a patterned framework for interpreting Arctic amplification (AA): AA is rooted in the tendency of atmospheric transport to converge moist static energy to the Arctic, with the lapse rate feedback playing a secondary role and other feedbacks playing a tertiary role.