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.

Understanding the SAM influence on the South Pacific ENSO teleconnection

“…Over the last decade, the combined impact of SAM and ENSO events on the South Pacific atmospheric circulation has garnered increasingly more attention (Kwok and Comiso 2002;Fogt and Bromwich 2006;L'Heureux and Thompson 2006;Gregory and Noone 2008;Stammerjohn et al 2008). In particular, Fogt and Bromwich (2006) found that the decadal variability of the ENSO teleconnection to the South Pacific is related to the coupling with the SAM.…”

New Reconstruction of Antarctic Near-Surface Temperatures: Multidecadal Trends and Reliability of Global Reanalyses*,+

“…The contrast with respect to East Antarctica can be traced, again, to a greater imprint of ENSO in West Antarctica (e.g., Bromwich et al 2000Bromwich et al , 2004Guo et al 2004;Gregory and Noone 2008;Schneider and Steig 2008;Okumura et al 2012). On the annual scale, the area of significant negative correlations is roughly limited to the Ross Sea sector of West Antarctica.…”

An introduction to stable water isotopes in climate models: benefits of forward proxy modelling for paleoclimatology

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