Regional characteristics of the recent moisture transport into the Arctic and Antarctic

Atmospheric moisture transport is a primary input of water into the polar regions. In the recent decades, several drastic changes in atmosphere, ocean and land have been observed in the Arctic and Antarctic: sea ice decline, Arctic warming amplification, changes in large-scale circulation pattern, westerly jet, lake and river ice phenology, and so on. Although the recent changes may further affect the polar hydrological cycles, the moisture transport over the regions is not well understood. Our previous study indicated that the column integrated amount of water vapor (precipitable water) was clearly increasing over the Arctic and gradually decreasing over the Antarctic during the past four decades, while there were no significant long-term changes in the zonal mean poleward moisture transport into both polar regions (Oshima and Yamazaki 2017 Czech Polar Reports). In this study, we further examined regional characteristics of the recent moisture transport over the Arctic and Antarctic by using differences of moisture flux and sea-level pressure in reanalysis data during 2011-2017 from those during 1981-2010.

The changes detected as the differences in the recent moisture transport are as follows. In the Arctic, the recent poleward moisture flux was enhanced over the Barents and Kara Seas in September and was also enhanced over the Arctic Ocean from the Atlantic side to the Pacific side. These anomalies induced moisture flux convergence over the Greenland Sea and divergence over the Barents Sea. In January, the moisture flux was enhanced over the east side of the Greenland inducing weak convergence over the center of the Arctic Ocean. The above-mentioned anomalies may be related to the decrease in sea ice and WACE (Warm Arctic/Cold Eurasia) pattern (i.e., Hori and Oshima 2018 SOLA). In the Antarctic, there were enhanced poleward moisture transport anomalies over the west side of the Antarctic Peninsula in March and May, which were associated with the deepening of the Amundsen Sea low.