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

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 (delta O-18) and Southern Hemisphere atmospheric circulation during the extended austral winter (April-November). The RICE delta O-18 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 delta O-18, are strongest when El Nino-Southern Oscillation (ENSO) and SAM are in-phase. That is when the SAM - /PSA1 + (El Nino) and SAM + /PSA1 - (La Nina) phasing prevails. When in-phase, the delta O-18 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 Nino) and SAM + /PSA1 - (La Nina) is associated with positive and negative delta O-18 anomalies, respectively. RICE delta O-18 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.

Automated summary

In this study, the water stable-isotope data from the RICE ice core are used to investigate the relationship between Southern Hemisphere atmospheric circulation and the RICE ice-core oxygen-18 isotopes. The results show a correlation between the RICE delta O-18 record and the Southern Annular Mode (SAM) and Pacific-South American pattern 1 (PSA1), which both project onto the Amundsen-Bellingshausen Sea geopotential height field. The strongest anomalies in atmospheric circulation, sea ice, and surface air temperature (SAT) in the Pacific sector Southern Ocean, eastern Ross Sea, and West Antarctic, as well as the RICE delta O-18, occur when El Nino-Southern Oscillation (ENSO) and SAM are in-phase.