The role of large-scale drivers in the Amundsen Sea Low variability and associated changes in water isotopes from the Roosevelt Island ice core, Antarctica

Abstract

Here we examine the water stable-isotope data from the Roosevelt Island Climate Evolution (RICE) ice core. Roosevelt Island is an independent ice rise located at the northeastern margin of the Ross Ice Shelf. In this study, we use empirical orthogonal function (EOF) analysis to investigate the relationship between RICE ice-core oxygen-18 isotopes (δ18O) and Southern Hemisphere atmospheric circulation during the extended austral winter (April–November). The RICE δ18O record is correlated with Southern Annular Mode (SAM) and Pacific–South American pattern 1 (PSA1), which both project onto the Amundsen–Bellingshausen Sea (ABS) geopotential height field. Pacific sector Southern Ocean, eastern Ross Sea, and West Antarctic’s atmospheric circulation, sea ice, and surface air temperature (SAT) anomalies, as well as RICE δ18O, are strongest when El Niño–Southern Oscillation (ENSO) and SAM are “in-phase”. That is when the SAM − /PSA1 + (El Niño) and SAM + /PSA1 − (La Niña) phasing prevails. When in-phase, the δ18O correlation with the 500-hPa geopotential height (Z500) is strong in regions (e.g., the Amundsen Sea) where their anomalies associated with SAM and PSA1 show the same sign. SAM − /PSA1 + (El Niño) and SAM + /PSA1 − (La Niña) is associated with positive and negative δ18O anomalies, respectively. RICE δ18O can aid in establishing past natural variability of the strength of the SH high-latitude Pacific sector ENSO-SAM connection and associated atmospheric circulation, sea ice, and SAT extremes.