Teleconnections and relationship between ENSO and SAM in reconstructions and models over the past millennium
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). Due to the temporally very limited instrumental records in most parts of the SH, very little is known about the relationship between these...
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ftcopernicus:oai:publications.copernicus.org:cpd79784 2023-05-15T13:15:04+02:00 Teleconnections and relationship between ENSO and SAM in reconstructions and models over the past millennium Dätwyler, Christoph Grosjean, Martin Steiger, Nathan J. Neukom, Raphael 2019-09-09 application/pdf https://doi.org/10.5194/cp-2019-110 https://www.clim-past-discuss.net/cp-2019-110/ eng eng doi:10.5194/cp-2019-110 https://www.clim-past-discuss.net/cp-2019-110/ eISSN: 1814-9332 Text 2019 ftcopernicus https://doi.org/10.5194/cp-2019-110 2019-12-24T09:48:34Z 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). Due to the temporally very limited instrumental records in most parts of the SH, very little is known about the relationship between these two key modes of variability and its stability over time. Here, we use proxy-based reconstructions and climate model simulations to quantify changes in tropical-extratropical SH teleconnections as represented by the correlation between the ENSO and SAM indices. Reconstructions indicate mostly negative correlations back to around 1400 CE confirming the pattern seen in the instrumental record over the last few decades. An ensemble of last millennium simulations of the model CESM1 confirms this pattern with very stable ensemble mean correlations around −0.3. Individual forced simulations, the pre-industrial control run and the proxy-based reconstructions indicate intermittent periods of positive correlations and particularly strong negative correlations. The fluctuations of the ENSO-SAM correlations are not significantly related to solar nor volcanic forcing in both proxy and model data, indicating that they are driven by internal variability in the climate system. Pseudoproxy experiments indicate that the currently available proxy records are able to reproduce the tropical-extratropical teleconnection patterns back to around 1600 CE. We analyse the spatial temperature and sea level pressure patterns during periods of positive and particularly strong negative teleconnections in the CESM model. Results indicate no consistent pattern during periods where the ENSO-SAM teleconnection changes its sign. However, periods of very strong negative SH teleconnections are associated with negative temperature anomalies across large fractions of the extra-tropical Pacific and a strengthening of the Aleutian Low. Text aleutian low Copernicus Publications: E-Journals Pacific |
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English |
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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). Due to the temporally very limited instrumental records in most parts of the SH, very little is known about the relationship between these two key modes of variability and its stability over time. Here, we use proxy-based reconstructions and climate model simulations to quantify changes in tropical-extratropical SH teleconnections as represented by the correlation between the ENSO and SAM indices. Reconstructions indicate mostly negative correlations back to around 1400 CE confirming the pattern seen in the instrumental record over the last few decades. An ensemble of last millennium simulations of the model CESM1 confirms this pattern with very stable ensemble mean correlations around −0.3. Individual forced simulations, the pre-industrial control run and the proxy-based reconstructions indicate intermittent periods of positive correlations and particularly strong negative correlations. The fluctuations of the ENSO-SAM correlations are not significantly related to solar nor volcanic forcing in both proxy and model data, indicating that they are driven by internal variability in the climate system. Pseudoproxy experiments indicate that the currently available proxy records are able to reproduce the tropical-extratropical teleconnection patterns back to around 1600 CE. We analyse the spatial temperature and sea level pressure patterns during periods of positive and particularly strong negative teleconnections in the CESM model. Results indicate no consistent pattern during periods where the ENSO-SAM teleconnection changes its sign. However, periods of very strong negative SH teleconnections are associated with negative temperature anomalies across large fractions of the extra-tropical Pacific and a strengthening of the Aleutian Low. |
format |
Text |
author |
Dätwyler, Christoph Grosjean, Martin Steiger, Nathan J. Neukom, Raphael |
spellingShingle |
Dätwyler, Christoph Grosjean, Martin Steiger, Nathan J. Neukom, Raphael Teleconnections and relationship between ENSO and SAM in reconstructions and models over the past millennium |
author_facet |
Dätwyler, Christoph Grosjean, Martin Steiger, Nathan J. Neukom, Raphael |
author_sort |
Dätwyler, Christoph |
title |
Teleconnections and relationship between ENSO and SAM in reconstructions and models over the past millennium |
title_short |
Teleconnections and relationship between ENSO and SAM in reconstructions and models over the past millennium |
title_full |
Teleconnections and relationship between ENSO and SAM in reconstructions and models over the past millennium |
title_fullStr |
Teleconnections and relationship between ENSO and SAM in reconstructions and models over the past millennium |
title_full_unstemmed |
Teleconnections and relationship between ENSO and SAM in reconstructions and models over the past millennium |
title_sort |
teleconnections and relationship between enso and sam in reconstructions and models over the past millennium |
publishDate |
2019 |
url |
https://doi.org/10.5194/cp-2019-110 https://www.clim-past-discuss.net/cp-2019-110/ |
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Pacific |
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Pacific |
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aleutian low |
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aleutian low |
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eISSN: 1814-9332 |
op_relation |
doi:10.5194/cp-2019-110 https://www.clim-past-discuss.net/cp-2019-110/ |
op_doi |
https://doi.org/10.5194/cp-2019-110 |
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