Analyzing the effects of sea ice melting and atmospheric heat transport on the warming around arctic based on comparable analysis and coupling modes

摘要

The Arctic warming has become a key signal with global climate change in recent decades. In this study, sea ice volume and whole layer atmospheric heat flux divergence were used to represent the local factor and external transport, respectively. The random forest algorithm was adopted to study the nonlinear effects and variations in importance between the local factors and external transport on Arctic warming between 1979 and 2018. The multivariate empirical orthogonal function decomposition method was applied to explore the coupling structure among sea ice volume, heat flux divergence, and temperature at different altitudes, locate the main passages of atmospheric heat transport to the Arctic, and explore the physical mechanisms of extreme Arctic climate events in the past two years. The analysis results suggest that sea ice has a significant impact on lower-level warming, and the atmospheric heat transport is essential in regulating temperature changes in the middle and upper troposphere. Additionally, on an interdecadal scale, the average state of Arctic warming was found to be strongly related to the Arctic Ocean Oscillation index, explaining the warming trend in the Atlantic sector. The trend is jointly controlled by the heat transport passages in the Pacific and Atlantic Oceans. The abrupt change in 2017-2018 was caused by the increased heat transport in the Pacific Ocean and weakened heat transport in the Atlantic Ocean, leading to abnormal warming and cooling near the two passages. On a seasonal scale, heat transport increase in the three passages located in 1) the Baffin Bay and the Labrador Sea, 2) the Nordic Peninsula and the Barents Sea, 3) the Bering Sea and the East Siberian Sea likely causes regional differences in Arctic summer warming. The increased heat transport in the Bering Sea and East Siberian Sea passage in winter made the Pacific sector significantly warmer. A positive feedback mechanism was created by the change in the circulation field between the temperature and Pacific heat transport.