| Popis: |
We use a Lagrangian objective feature tracking algorithm with the PAMIP experiments to determine the response of extratropical cyclones to sea-ice loss and consequent weakening of the equator-to-pole near-surface temperature gradient. The wintertime storm tracks are found to shift equatorward in the North Atlantic and over Europe, and eastward in the North Pacific. In both regions, cyclones become weaker and slower, particularly on the poleward flank of the storm tracks. On average, there are fewer individual cyclones in the extratropics each winter, they last longer, are weaker, and propagate more slowly. These changes are greatest for Arctic cyclones, but still statistically significant in the midlatitudes despite being small compared to internal variability. Inter-model spread in cyclone responses is comparable to the magnitude of the multi-model mean response. Little change in summertime equator-to-pole near-surface temperature gradient or in extratropical cyclones is found. Separately, we determine the response to extratropical cyclones to future SST change and compare to the response found in the CMIP6 simulations in order to place our conclusions within the broader context of climate change. |
