[A-CC45] 雪氷学

[ACC45-P02] Analysis of long-term wind variations and strong wind occurrences at the NDF station on the Antarctic ice sheet summit

小竹 駿輝¹、*杉浦 幸之助²、堀 雅裕²、平沢 尚彦³ (1.富山大学大学院理工学研究科、2.富山大学学術研究部都市デザイン学系、3.国立極地研究所)

キーワード：

南極、表面質量収支、風向、風速、氷床頂部、吹雪

In recent years, rising global temperatures in the Arctic and Antarctic have heightened concerns about the impacts of mass changes in the cryosphere on sea level and ecosystems. Understanding the surface mass balance of the Antarctic ice sheet requires not only knowledge of snowfall but also an understanding of wind-driven snow redistribution and sublimation processes. Detailed wind characteristics, particularly over the interior ice sheet, remains an area requiring further investigation. This study focused on wind characteristics, which strongly influence snow redistribution. Using Automatic Weather Station (AWS) data from the NDF site (77º47'S, 39º03'E) on the Antarctic ice sheet summit and ERA5 reanalysis data, we examined the long-term variability characteristics of wind and the factors behind strong wind events. Analysis of differences in prevailing wind directions compared to Dome Fuji Station revealed that north winds were slightly dominant at the NDF site throughout the year. This is attributed to the site's southern location relative to Dome Fuji Station and its lower elevation, which expose it to stronger katabatic winds descending from the higher elevation of Dome Fuji Station, in addition to broader wind patterns. Next, a correlation analysis of wind speeds at the NDF site and surrounding areas was conducted for the 30-year period from 1993 to 2022. The results showed that winds at the NDF site exhibited a high correlation with the ridge portion of the elevation distribution. Furthermore, years with a large positive stratospheric polar vortex index showed a U-shaped negative correlation east of the NDF station, suggesting the influence of cold air confinement by the polar vortex. In contrast, during years with a weak polar vortex, a gentle positive correlation spread across the entire polar region, suggesting the influence of air mass inflow from lower latitudes associated with large-scale changes in pressure patterns. Furthermore, analysis of the strong wind event in June 2022 revealed that a blocking high-pressure system formed east of the NDF location and then remained stationary. This created a strong pressure gradient extending from the middle troposphere to the lower troposphere between the high and a low-pressure system to the north. This pressure pattern likely caused a rapid rise in surface pressure and an increase in temperature due to warm air advection from the low latitudes accompanied by strong northerly winds. This study revealed that wind characteristics at NDF are dominated by air masses originating from inland areas or from the northern coastal regions, depending on the strength of the stratospheric polar vortex, with these patterns becoming apparent depending on the season. These phenomena, as indicated by reanalysis data, were also confirmed by AWS measurements. We plan to proceed with analyses to understand the actual processes of snow redistribution and sublimation within this wind system.