Blocking Events in East Antarctica: Impact on Precipitation and their Association with Large-Scale Atmospheric Circulation Modes

Abstract

Abstract This study, utilizing ERA5 data from 1979 to 2021, identifies a prevalent occurrence of blocking events in East Antarctica, particularly in the region extending from Wilkes Land to Dronning Maud Land. The genesis of these blocking highs is typically facilitated by the intensification of Rossby waves within the circumpolar westerlies. By classifying the circulation patterns causing the blocking events, the blocking events in East Antarctica are divided into five categories. On the western flank of the blocking high, we observe the transportation of warm and humid air into inland Antarctica, instigating regional snowfall. High precipitation levels are observed in different regions based on the specific location of the blocking high. We also demonstrate that the contribution of atmospheric blockings to total annual precipitation and extreme precipitation events increases from coastal to inland. Over the East Antarctic plateau, the blockings are responsible for at least 15% of total accumulated snowfall and 30% of extreme precipitation events. Finally, we find a significant relationship between the interannual variability in East Antarctic blocking frequency and the phase variability of the Southern Annular Mode (SAM). A positive phase of the SAM inhibits an increase in blocking frequency, while a negative phase favors an increase. However, the two Pacific–South American patterns (PSA-1 and PSA-2), characterized by wave trains originating in the tropical Pacific that extend across the Southern Hemisphere extratropics, do not significantly influence the interannual variability in East Antarctic blocking frequency.