The role of Arctic sea ice loss in projected polar vortex changes
The Northern Hemisphere stratospheric polar vortex (SPV) plays a key role for mid-latitude weather and climate. However, in what way the SPV will respond to global warming is not clear, with climate models disagreeing on the sign and magnitude of projected SPV strength change. Here we address the ro...
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ftcopernicus:oai:publications.copernicus.org:wcdd86709 2023-05-15T14:59:47+02:00 The role of Arctic sea ice loss in projected polar vortex changes Kretschmer, Marlene Zappa, Giuseppe Shepherd, Theodore G. 2020-07-27 application/pdf https://doi.org/10.5194/wcd-2020-29 https://wcd.copernicus.org/preprints/wcd-2020-29/ eng eng doi:10.5194/wcd-2020-29 https://wcd.copernicus.org/preprints/wcd-2020-29/ eISSN: 2698-4016 Text 2020 ftcopernicus https://doi.org/10.5194/wcd-2020-29 2020-08-03T16:22:02Z The Northern Hemisphere stratospheric polar vortex (SPV) plays a key role for mid-latitude weather and climate. However, in what way the SPV will respond to global warming is not clear, with climate models disagreeing on the sign and magnitude of projected SPV strength change. Here we address the role of Barents and Kara (BK) sea ice loss in this. We provide evidence for a non-linear response of the SPV to global mean temperature change, dependent on the time the BK Seas become ice-free. Using a causal network approach, we demonstrate that climate models show some partial support for the previously proposed link between low BK sea ice in autumn and a weakened winter SPV, but that this effect is plausibly very small relative to internal variability. Yet, given the expected dramatic decrease of sea ice in the future, a small causal effect can explain all of the projected ensemble-mean SPV weakening, approximately one-half of the ensemble spread at the middle of the 21st century, and one-third of the spread at the end of the century. Finally, we note that most models have unrealistic amounts of BK sea ice, meaning that their SPV response to ice loss is unrealistic. Bias-adjusting for this effect leads to pronounced differences in SPV response of individual models at both ends of the spectrum, but has no strong consequences for the overall ensemble mean and spread. Overall, our results indicate the importance of exploring all plausible implications of a changing Arctic for regional climate risk assessments. Text Arctic Global warming Sea ice Copernicus Publications: E-Journals Arctic |
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Open Polar |
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Copernicus Publications: E-Journals |
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ftcopernicus |
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English |
description |
The Northern Hemisphere stratospheric polar vortex (SPV) plays a key role for mid-latitude weather and climate. However, in what way the SPV will respond to global warming is not clear, with climate models disagreeing on the sign and magnitude of projected SPV strength change. Here we address the role of Barents and Kara (BK) sea ice loss in this. We provide evidence for a non-linear response of the SPV to global mean temperature change, dependent on the time the BK Seas become ice-free. Using a causal network approach, we demonstrate that climate models show some partial support for the previously proposed link between low BK sea ice in autumn and a weakened winter SPV, but that this effect is plausibly very small relative to internal variability. Yet, given the expected dramatic decrease of sea ice in the future, a small causal effect can explain all of the projected ensemble-mean SPV weakening, approximately one-half of the ensemble spread at the middle of the 21st century, and one-third of the spread at the end of the century. Finally, we note that most models have unrealistic amounts of BK sea ice, meaning that their SPV response to ice loss is unrealistic. Bias-adjusting for this effect leads to pronounced differences in SPV response of individual models at both ends of the spectrum, but has no strong consequences for the overall ensemble mean and spread. Overall, our results indicate the importance of exploring all plausible implications of a changing Arctic for regional climate risk assessments. |
format |
Text |
author |
Kretschmer, Marlene Zappa, Giuseppe Shepherd, Theodore G. |
spellingShingle |
Kretschmer, Marlene Zappa, Giuseppe Shepherd, Theodore G. The role of Arctic sea ice loss in projected polar vortex changes |
author_facet |
Kretschmer, Marlene Zappa, Giuseppe Shepherd, Theodore G. |
author_sort |
Kretschmer, Marlene |
title |
The role of Arctic sea ice loss in projected polar vortex changes |
title_short |
The role of Arctic sea ice loss in projected polar vortex changes |
title_full |
The role of Arctic sea ice loss in projected polar vortex changes |
title_fullStr |
The role of Arctic sea ice loss in projected polar vortex changes |
title_full_unstemmed |
The role of Arctic sea ice loss in projected polar vortex changes |
title_sort |
role of arctic sea ice loss in projected polar vortex changes |
publishDate |
2020 |
url |
https://doi.org/10.5194/wcd-2020-29 https://wcd.copernicus.org/preprints/wcd-2020-29/ |
geographic |
Arctic |
geographic_facet |
Arctic |
genre |
Arctic Global warming Sea ice |
genre_facet |
Arctic Global warming Sea ice |
op_source |
eISSN: 2698-4016 |
op_relation |
doi:10.5194/wcd-2020-29 https://wcd.copernicus.org/preprints/wcd-2020-29/ |
op_doi |
https://doi.org/10.5194/wcd-2020-29 |
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1766331911022575616 |