Does ocean coupling matter for the northern extratropical response to projected Arctic sea ice loss?

The question of whether ocean coupling matters for the extratropical Northern Hemisphere atmospheric response to projected late 21st century Arctic sea ice loss is addressed using a series of experiments with Community Climate System Model version 4 at 1° spatial resolution under different configurations of the ocean model component: no interactive ocean, thermodynamic slab ocean, and full‐depth (dynamic plus thermodynamic) ocean. Ocean‐atmosphere coupling magnifies the response to Arctic sea ice loss but does not change its overall structure; however, a slab ocean is inadequate for inferring the role of oceanic feedbacks. The westerly winds along the poleward flank of the eddy‐driven jet weaken in response to Arctic sea ice loss, accompanied by a smaller‐magnitude strengthening on the equatorward side, with largest amplitudes in winter. Dynamical and thermodynamic oceanic feedbacks amplify this response by approximately 50%. Air temperature, precipitation, and sea level pressure responses also show sensitivity to the degree of ocean coupling. Key Points Air‐sea coupling amplifies the extratropical response to Arctic sea ice loss A slab ocean model is inadequate for inferring the effects of air‐sea coupling The atmospheric response is largest in winter despite that the sea ice loss is greatest in autumn