Influence of ENSO and SAM on the occurrence of absolute extremes and behavior of Ta, SST, and SIC anomalies in the western Antarctic Peninsula

Abstract

This study aims to improve the understanding of the interaction between El Niño-Southern Oscillation (ENSO) events and the phases of the Southern Annular Mode (SAM), as well as their influence on the western Antarctic Peninsula (WAP). Monthly series of air temperature (Ta), sea surface temperature (SST), and sea ice coverage (SIC) from 1981 to 2020 were analyzed at six representative points within the study area. Ta, SIC, and SST data were obtained from the ERA5 database. The Southern Oscillation Index (SOI) and Antarctic Oscillation Index (AAOI) were sourced from NOAA’s Climate Prediction Center. The spectral density of the anomaly series for each variable was calculated, and the characteristic cycles of SAM and ENSO were extracted. The most influential components driving the oscillations of the studied series were identified. A cross-correlation analysis was conducted between the anomaly components of Ta, SIC, and SST and those of SOI and AAOI. The results indicate that Ta series exhibit moderate positive correlations with SAM, particularly between the 5.2-year quasi-period of AAOI and the 4.4-year quasi period of Ta in the Drake Passage and Bransfield Strait. The SST series in Bransfield correlate with AAOI5.2, while the quasi-periods of 4.6 and 5.2 years in the Drake Passage correlate with SOI3.5. The SIC series show positive correlations with the 3.5-year quasi-period of SOI for lag times greater than one year, except in the Bransfield Strait. Extreme absolute Ta and SST events in the WAP region are strongly influenced by SAM and ENSO. It is concluded that the coupling of ENSO and SAM phases amplifies their effects on meteo-marine variables.