CMIP6 projected response of the East Asian winter climate to the sea ice-free Arctic

This research evaluated the performance of 19 Coupled Model Intercomparison Project phase 6 (CMIP6) models in simulating the Arctic sea ice from the perspective of annual cycle, spatial pattern and temporal variation. Based on the evaluation, five models with better comprehensive performance capacity were optimized as the ensemble to project the response of the East Asian winter climate to the sea ice-free Arctic occurring under the SSP2-4.5 and SSP5-8.5 scenarios, respectively. The ensemble projections indicate that the sea ice-free Arctic is followed by a weakening of the East Asian winter monsoon, which is characterized with the shallower East Asian trough and weaker East Asian jet stream. Concurrently, the winter surface net radiation flux is projected to increase in the East Asian-western North Pacific region. These changes favour large-scale warming in the East Asian-western North Pacific region. Moreover, the warming is more pronounced under the sea ice-free Arctic of SSP2-4.5 than under that of SSP5-8.5. The winter precipitation tends to increase along the East Asian coast from South China to the Sea of Okhotsk. Such an increase is closely associated with the enhancement of low-level moisture. Due to larger enhancement of moisture, there appears greater increase of precipitation in the monsoon region from South China to Japan under the sea ice-free Arctic of SSP5-8.5 compare to that under SSP2-4.5. Substantial changes are also projected for the temperature and precipitation extremes, such as a general increase in warm days and warm nights and an overall intensification of extreme precipitation in the East Asian-western North Pacific region.