The tug-of-war on the storm tracks between sea-ice loss and ocean warming is mainly an Atlantic phenomenon

The effects of Arctic sea-ice loss or global ocean surface warming on the Northern Hemisphere storm tracks and jet streams in boreal winter are examined using simulations from the Polar Amplification Model Intercomparison Project. The Atlantic atmospheric circulation response to sea-ice loss broadly opposes that in response to ocean warming. Whilst the storm tracks and the eddy-driven jet shift equatorward in response to sea-ice loss, they shift poleward in response to ocean surface warming. Atlantic storms are generally weaker and propagate more slowly in response to sea-ice loss, whilst they are stronger and faster-moving in response to ocean warming. Conversely, in the Pacific, the responses are generally dissimilar in pattern and sign or they act to shift the circulation in the same direction. Potential causes for these differences between the Atlantic and Pacific sectors are the differing mean states and geography, which lead to differing responses of the meridional temperature gradients. Both sea-ice loss and ocean warming act to weaken the lower tropospheric temperature gradient in the Pacific, whereas they have opposite effects on the meridional temperature gradient in the Atlantic. This weakened temperature gradient in response to ocean warming in the Pacific is due to greater warming along the west coast of North America than over the ocean farther south. Finally, the more equatorward climatological position of the Pacific jet relative to the Atlantic jet means that the zonal-mean zonal wind response to sea-ice loss acts within the region of maximum climatological winds in the Pacific, but on the flanks of it in the Atlantic.