Spatiotemporal Variations in Surface Air ⁷Be Concentrations Over the Antarctic Regions of the Indian Sector

This study examined spatiotemporal variations in Beryllium‐7 ( 7 Be) concentrations measured in surface air in high‐latitude regions of the Indian sector of the Southern Ocean, including two Japanese coastal stations. The sites included Syowa Station (69°00′S, 39°35′E) and site S17 (69°02′S, 40°05′E) on the coastal Antarctic ice sheet. Observations were conducted over three summers (2014/15, 2016/17, and 2017/18) as part of the Japanese Antarctic Research Expedition (JARE). Surface aerosol particles containing 7 Be were collected daily or twice daily using a high‐volume air sampler. 7 Be concentrations ranged from below the detection limit of approximately 1–12 mBq/m 3 . The 7 Be concentrations are higher at higher latitudes than at midlatitudes, and the effects of removal by precipitation associated with storm track may be more pronounced at midlatitudes. Fluctuations in 7 Be concentrations were correlated with the passage of synoptic‐scale disturbances over the sea to the west of 80°E, likely due to tropopause folding. Maximum concentrations were observed at site S17, where a stepwise increase from approximately 4 mBq/m 3 (5–14 January) to approximately 8 mBq/m 3 (15–28 January) was observed, likely due to repeated synoptic‐scale disturbances. A diurnal pattern was observed in 7 Be concentrations at site S17, with nighttime (daytime) concentrations being highest (lowest) when katabatic winds were stronger (weaker). From January 2015 to January 2017, the increase rate in 7 Be concentration at site S17 was similar to the increase rate in neutron counts observed at the Neumayer III station, suggesting a reflection of the elevated 7 Be production due to increased galactic cosmic rays.