Discriminators of Antarctic Atmospheric River Environments            

Although rare, atmospheric rivers (ARs) substantially influence the interannual variability of Antarctic surface mass balance. We identify characteristics unique to AR environments by comparing (1) AR, (2) Analog (environments that feature high-low pressure couplets, similar to AR environments, but no AR), and (3) Top AR (high-precipitation AR timesteps) during 1980–2019 around Antarctica. We find significant differences between AR and Analog environments including more intense and poleward-shifted mid-tropospheric geopotential height couplets as well as larger atmospheric moisture anomalies. We find similar significant enhancement in synoptic-scale dynamic drivers of Top ARs compared to AR environments, but no significant difference in local integrated water vapor anomalies. Instead, our results highlight the importance of large-scale dynamic drivers of Top AR timesteps, including connections between high-precipitation ARs and Rossby waves excited by tropical convection. This deeper understanding of Antarctic AR environments provides context for interpreting future changes to the Antarctic surface mass balance.