Poleward atmospheric moisture transport (AMT) into the Arctic Ocean can change atmospheric moisture or water vapor
content and cause cloud formation and redistribution, which may change downward longwave radiation and, in turn, surface
energy budgets, air temperatures, and sea-ice production and melt. In this study, we found a consistently enhanced poleward
AMT across 60◦N since 1959 based on the NCAR–NCEP reanalysis. Regional analysis demonstrates that the poleward AMT
predominantly occurs over the North Atlantic and North Pacific regions, contributing about 57% and 32%, respectively, to the
total transport. To improve our understanding of the driving force for this enhanced poleward AMT, we explored the role that
extratropical cyclone activity may play. Climatologically, about 207 extratropical cyclones move across 60◦N into the Arctic
Ocean each year, among which about 66 (32% of the total) and 47 (23%) originate from the North Atlantic and North Pacific
Ocean, respectively. When analyzing the linear trends of the time series constructed by using a 20-year running window, we
found a positive correlation of 0.70 between poleward yearly AMT and the integrated cyclone activity index (measurement
of cyclone intensity, number, and duration). This shows the consistent multidecadal changes between these two parameters
and may suggest cyclone activity plays a driving role in the enhanced poleward AMT. Furthermore, a composite analysis
indicates that intensification and poleward extension of the Icelandic low and accompanying strengthened cyclone activity
play an important role in enhancing poleward AMT over the North Atlantic region.

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• Role of Extratropical Cyclones in the Recently Observed Increase in Poleward Moisture Transport into the Arctic Ocean