Linking stable water isotopes in a firn core from the Weddell Sea sector to regional atmospheric patterns

Abstract Stable water isotopes data extracted from polar ice/firn cores provides valuable climate information. This study presents isotopic time series from a shallow firn core (∼9 m deep) in the Möller Ice Stream basin, Weddell Sea sector, Antarctica. We investigated the relationships between water isotopic ratios ( δ s; i.e., δ 18 O and δ D), d-excess data, hemispheric and regional meteorological data, large-scale atmospheric modes, specifically the Southern Annular Mode (SAM) and Pacific South America pattern (PSA), as well as the position and depth of the Amundsen Sea Low (ASL). The interannual variability of δ s from 1999–2014 is largely explained by changes in SAM and PSA phases and the ASL response. Positive δ s anomalies are associated with (1) warming in the Antarctic Peninsula, southern tip of South America, and high latitudes of the western Southern Atlantic Ocean; (2) northerly flow of heat and moisture from the Antarctic Peninsula and the Weddell Sea sector; (3) establishment of positive geopotential anomalies over the southeast of South America and New Zealand, and negative geopotential anomalies over the ASL region; and, to a lesser extent, (4) the decrease in sea ice in the Weddell Sea sector. Although the δ s reflect large-scale atmospheric forcing, it is important to note that core-based studies may have biases and limited regional representation. This underscores the need for further ice core research to refine these connections at the basin scale and improve regional climate reconstructions.