Northern Hemisphere Wintertime Teleconnections from the 2023–24 El Niño Offset by Background SST Trends.
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| Title: | Northern Hemisphere Wintertime Teleconnections from the 2023–24 El Niño Offset by Background SST Trends. |
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| Authors: | Deser, Clara1 (AUTHOR) cdeser@ucar.edu, Yeager, Stephen1 (AUTHOR), Phillips, Adam S.1 (AUTHOR), Rosenbloom, Nan1 (AUTHOR), Zhao, Xueying1 (AUTHOR) |
| Source: | Journal of Climate. Jan2026, Vol. 39 Issue 1, p363-383. 21p. |
| Subjects: | El Niño, Teleconnections (Climatology), Ocean temperature, Climatic zones, Climate change, Rossby waves, Precipitation anomalies |
| Geographic Terms: | Indian Ocean, Northern Hemisphere |
| Abstract: | El Niño of 2023–24 ranked among the top five strongest El Niño events of the past 70 years, yet wintertime atmospheric teleconnections to the extratropical Northern Hemisphere were markedly weaker than anticipated. Here, we conduct a series of atmospheric modeling experiments using prescribed observed sea surface temperatures (SSTs) and radiative forcings to test the hypothesis that the observed pattern of background SST trends since 1980 was responsible for counteracting the expected teleconnection response. This so-called "SST pattern effect" (enhanced warming in the tropical Indian and Atlantic Oceans and relative cooling in the eastern tropical Pacific) is shown to drive a teleconnection of the opposite sign via a Rossby wave response to anomalous precipitation over the western tropical Pacific driven remotely from the Indian Ocean. The circulation response to 2023–24 El Niño in the absence of background SST changes is almost entirely cancelled by the teleconnection produced by SST trends, with consequences for precipitation impacts over North America and Europe. Analogous behavior is found for the observed circulation anomalies, although internal atmospheric variability may also contribute. The results underscore the importance of considering the modulating influence of background SST trends, both natural and anthropogenic in origin, on El Niño teleconnections and associated climate impacts in the coming decades. Significance Statement: El Niño of 2023–24 ranked among the top five strongest El Niño events of the past 70 years, yet the expected wintertime atmospheric circulation and precipitation impacts over the Northern Hemisphere did not materialize. We investigate the reasons why this was the case and find that effects from long-term trends in tropical sea surface temperatures counteracted the expected El Niño teleconnections. Our results underscore the importance of considering the modulating influence of background sea surface temperatures on El Niño's fingerprint, especially as anthropogenic climate change accelerates in the coming decades. [ABSTRACT FROM AUTHOR] |
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| Database: | Engineering Source |
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| Abstract: | El Niño of 2023–24 ranked among the top five strongest El Niño events of the past 70 years, yet wintertime atmospheric teleconnections to the extratropical Northern Hemisphere were markedly weaker than anticipated. Here, we conduct a series of atmospheric modeling experiments using prescribed observed sea surface temperatures (SSTs) and radiative forcings to test the hypothesis that the observed pattern of background SST trends since 1980 was responsible for counteracting the expected teleconnection response. This so-called "SST pattern effect" (enhanced warming in the tropical Indian and Atlantic Oceans and relative cooling in the eastern tropical Pacific) is shown to drive a teleconnection of the opposite sign via a Rossby wave response to anomalous precipitation over the western tropical Pacific driven remotely from the Indian Ocean. The circulation response to 2023–24 El Niño in the absence of background SST changes is almost entirely cancelled by the teleconnection produced by SST trends, with consequences for precipitation impacts over North America and Europe. Analogous behavior is found for the observed circulation anomalies, although internal atmospheric variability may also contribute. The results underscore the importance of considering the modulating influence of background SST trends, both natural and anthropogenic in origin, on El Niño teleconnections and associated climate impacts in the coming decades. Significance Statement: El Niño of 2023–24 ranked among the top five strongest El Niño events of the past 70 years, yet the expected wintertime atmospheric circulation and precipitation impacts over the Northern Hemisphere did not materialize. We investigate the reasons why this was the case and find that effects from long-term trends in tropical sea surface temperatures counteracted the expected El Niño teleconnections. Our results underscore the importance of considering the modulating influence of background sea surface temperatures on El Niño's fingerprint, especially as anthropogenic climate change accelerates in the coming decades. [ABSTRACT FROM AUTHOR] |
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| ISSN: | 08948755 |
| DOI: | 10.1175/JCLI-D-25-0227.1 |
