Weather Regimes Preclude the Observation of a Southern Annular Mode Signal in Two Coastal East Antarctic Ice Cores

Abstract The Southern Annular Mode (SAM) represents the dominant pattern of climate variability in the extratropical Southern Hemisphere. However, its signature in coastal East Antarctic ice core records is unclear. A daily synoptic typing data set for the southern Indian Ocean constructed using self‐organizing maps on 500 hPa daily geopotential height anomalies was used to investigate the relationship between the SAM and ice core records from Law Dome and Mount Brown South. Results indicate that synoptic weather regimes can either enhance or suppress the signature of the SAM on surface weather and ice core records. Weather regimes that are more likely during negative SAM and are associated with positive temperature anomalies over East Antarctica support the observed relationship between the SAM and the Law Dome δ 18 O record since 1979. In contrast, weather regimes that describe meridional moisture flux toward Antarctica explain more snowfall accumulation variability at the ice core sites compared to the SAM, which contributes to suppressing the SAM signal in snowfall accumulation records. Results highlight the importance of considering the synoptic‐scale dynamics on the relationship and stationarity of the SAM influence on surface weather and interpretation of ice core records. Given the limited robust relationships between the SAM and the ice core records investigated, caution should be taken before using these records to reconstruct past SAM variability. Instead, the coastal East Antarctic ice core records provide insight into the occurrence of meridional weather regimes, which are often associated with extreme temperature and precipitation conditions.