Variability in the teleconnection between the El Niño–Southern Oscillation and West Antarctic climate deduced from West Antarctic ice core isotope records

Abstract

The U.S. contribution to the International Trans‐Antarctic Scientific Expedition (ITASE) program obtained several ice cores from the West Antarctic Ice Sheet. Because of proximity to the Pacific Ocean, the West Antarctic ice cores are expected to have an El Niño–Southern Oscillation (ENSO) signature. The ITASE 2001‐5 core δ18O isotope was selected for detailed analysis here because its location, high annual accumulation, and record length make it an ideal candidate for capturing the effects of regional circulation anomalies in the isotopic composition. The 2001‐5 core is compared to two other cores, the 2001‐2 and 2001‐3 cores, which are further west and therefore capture some spatial variability of the regional circulation on various time scales. Analysis shows that several phenomena, including ENSO, leave a signature in the ice cores. Evidence suggests that ENSO signals in the ice cores are significantly modulated by low‐frequency variability. Correlation with the Southern Annular Mode (SAM), global temperature, Pacific Decadal Oscillation, and ENSO shows that temperature and ENSO generally appear to have the strongest influence on the 2001‐5 isotope signal while there is no clearly dominant single influence in the other cores. Results suggest that the teleconnection between ENSO and the 2001‐5 core is quite dependent on the state of the SAM. Specifically, when the Southern Oscillation Index (SOI) and SAM are in phase, there is an ENSO related pressure anomaly west of the Antarctic Peninsula, in the vicinity of the ice cores studied. This extends previous findings to span the entire 20th century.