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Abstract:
Anthropogenic global warming generally has been shown to cause the rapid loss of Arctic sea ice in recent decades. However, whether this rapid loss has exerted significant impact on recent changes in tropical cyclone (TC) activity over the North Pacific remains unknown. Here, we first extract the leading mode of the rapid loss of Arctic sea ice concentration (SIC) averaged in July-October during 1950-2021, and then investigate the impact of this leading mode on long-term changes in TC genesis frequency over the western North Pacific (WNP) and the eastern North Pacific (ENP). Results show that the reduced SIC was favorable for more TC geneses over the whole ENP but led to fewer TC geneses over most of the WNP. Further analyses based on dynamical diagnosis and CMIP6 model data demonstrate that the rapid loss of Arctic SIC is responsible for local warming and weakened upper-tropospheric westerly over most of the Arctic. This triggers a teleconnection wave train over the upper troposphere from high to low latitudes, leading to the weakening of tropical easterly jet over the tropical western Pacific and the strengthening over the tropical eastern Pacific. The former dynamically contributes to decrease in mid-level upward motion and low-level vorticity, and eventually accounts for few TCs over the WNP. The opposite dynamical process is true for the ENP TCs. The finding not only has an important implication for future TC changes but also suggests a possible link between Arctic sea ice and tropical climate.
