Projected and historical amplification of moisture fluxes towards Antarctica by synoptic eddies

Abstract Synoptic weather systems play a crucial role in transporting moisture to Antarctica. Climate models project significant changes in these systems, including a wintertime intensification and a summertime poleward shift, with implications for Antarctic ice mass balance. Our analysis of CMIP6 model output shows synoptic moisture fluxes across the Antarctic Circle increasing by 2–6% per decade under high-emission scenarios, accounting for 24% of winter and 93% of summer total moisture transport trends. This increase is mainly associated with enhanced eddy moisture anomalies rather than stronger eddy wind anomalies that are often used to gauge storm track activity. Eddy-driven moisture variability also accounts for a substantial fraction of inter-model uncertainty in future projections. Furthermore, using a large-ensemble approach, we show that differences between reanalysis and multi-model mean externally forced trends could possibly be due to natural climatic variability, while potential model biases cannot be excluded.