Teleconnections and relationship between the El Niño–Southern Oscillation (ENSO) and the Southern Annular Mode (SAM) in reconstructions and models over the past millennium

Dätwyler, Christoph; Grosjean, Martin; Steiger, Nathan J.; Neukom, Raphael

doi:10.5194/cp-16-743-2020

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Teleconnections and relationship between the El Niño–Southern Oscillation (ENSO) and the Southern Annular Mode (SAM) in reconstructions and models over the past millennium

Dätwyler, Christoph Institute of Geography and Oeschger Centre for Climate Change Research, University of Bern, Bern, 3012, Switzerland
Grosjean, Martin Institute of Geography and Oeschger Centre for Climate Change Research, University of Bern, Bern, 3012, Switzerland
Steiger, Nathan J. Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY, USA
Neukom, Raphael Institute of Geography and Oeschger Centre for Climate Change Research, University of Bern, Bern, 3012, Switzerland - Department of Geosciences, University of Fribourg, Fribourg, Switzerland - Department of Geography, University of Zurich, Zurich, Switzerland

22.04.2020

Published in:

Climate of the Past. - 2020, vol. 16, no. 2, p. 743–756

English The climate of the Southern Hemisphere (SH) is strongly influenced by variations in the El Niño–Southern Oscillation (ENSO) and the Southern Annular Mode (SAM). Because of the limited length of instrumental records in most parts of the SH, very little is known about the relationship between these two key modes of variability over time. Using proxy-based reconstructions and last-millennium climate model simulations, we find that ENSO and SAM indices are mostly negatively correlated over the past millennium. Pseudo-proxy experiments indicate that currently available proxy records are able to reliably capture ENSO–SAM relationships back to at least 1600CE. Palaeoclimate reconstructions show mostly negative correlations back to about 1400CE. An ensemble of last-millennium climate model simulations confirms this negative correlation, showing a stable correlation of approximately −0.3. Despite this generally negative relationship we do find intermittent periods of positive ENSO–SAM correlations in individual model simulations and in the palaeoclimate reconstructions. We do not find evidence that these relationship fluctuations are caused by exogenous forcing nor by a consistent climate pattern. However, we do find evidence that strong negative correlations are associated with strong positive (negative) anomalies in the Interdecadal Pacific Oscillation and the Amundsen Sea Low during periods when SAM and ENSO indices are of opposite (equal) sign.

Faculty

Faculté des sciences et de médecine

Department

Département de Géosciences

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