The changing mass of the Antarctic Ice Sheet during ENSO-dominated periods in the GRACE era (2002–2022)

Abstract. Large-scale modes of climate variability significantly influence Antarctic Ice Sheet (AIS) mass change. Improved understanding of the relationship between these climate modes and AIS mass change can help reduce uncertainties in future ice mass estimates and its contribution to sea level rise. However, the spatiotemporal patterns of AIS mass variation driven by El Niño Southern Oscillation (ENSO)-induced atmospheric circulation remain unclear. We investigated AIS mass variability during different ENSO periods using Gravity Recovery and Climate Experiment (GRACE) observed mass changes and modelled surface mass balance (using RACMO2.4p1) over the period 2002 to 2022. To allow comparison with GRACE, we used a cumulative sum indexing method to define different ENSO-dominated `periods' over 2002–2022. This method results in time periods that are dominated by a particular phase of ENSO, that is not necessarily equivalent to specific events as derived from canonical indices. The results show strong spatial variability in how the ENSO teleconnection cumulatively manifests over the AIS. These differing spatial patterns are primarily driven by changes in the Amundsen Sea Low strength, location, and extent, which alter circulation patterns and moisture flow in West Antarctica. In East Antarctica, ice mass variability is largely influenced by the positioning of cyclonic and anticyclonic circulation anomalies, primarily driven by the Southern Annular Mode; however, ENSO signals are also present. In both East and West Antarctica, this study shows that the spatial impact of any given ENSO-dominant period can trigger distinct circulation patterns which can variably influence surface mass balance and ice mass change. However, uncertainties remain, as the mass variability observed during ENSO-dominant periods may not be solely attributed to ENSO, due to teleconnections that may not have fully developed or may have been masked by other processes.