Antarctic Atmospheric River Response to Modes of Variability in Future Climates

Atmospheric rivers (ARs) impacting the Antarctic continent typically transport both heat and moisture sourced from lower latitudes. They are both dynamically and thermodynamically driven, and are fundamentally connected to Southern Hemisphere storm tracks and teleconnection patterns. Although only a few ARs actually reach past the coastal regimes and onto the ice sheets each year, they hold an outsized impact to the local hydroclimate by producing either local melt events, or significant snow accumulations, depending on their thermal characteristics.

Here, we present analysis based on large ensembles simulations of historical and future climate scenarios from two different Earth System models (Community Earth System Model, Version 2, CESM2, and Energy Exascale Earth System Model, version 2, E3SMv2) to diagnose future AR pathways driven by various teleconnection patterns. Teleconnection patterns can be used to diagnose AR timing, placement, and impacts to ice shelves and ice sheets, therefore, shifts to these patterns matter for the regional climatology. We focus on modes of variability that have been shown to hold importance for Southern Hemisphere variability in both models and observations, and include the SAM (Southern Annular Mode), PSA (Pacific South American Modes), and IOD (Indian Ocean Dipole). We validate the model with reanalysis, and then test the thermodynamic response of ARs to climate change by applying different moisture thresholds when identifying the ARs. Preliminary results show that the Pacific South American mode is the dominant teleconnection pattern influencing ARs over the West Antarctic ice sheet, and that under climate change, although both models consistently simulate a decrease in AR activity over the Southern hemisphere storm track, changes to Antarctic AR hotspots differ and have greater uncertainty.