Impact of long-term SST trends on atmospheric teleconnections driven by the 2023/24 El Niño

Speaker: Clara Deser
Institution: NCAR
Location: MS 7124
Date: February 5, 2025
Time: 3:00 pm to 4:00 pm


Abstract:

The 2023/24 El Niño event ranked as the 5th strongest in the past 70 years, yet the expected wintertime atmospheric teleconnection pattern over the extratropical Northern Hemisphere did not materialize.  In this study, we test the hypothesis that background SST trends interfered with the canonical El Niño teleconnection response. A series of AMIP experiments with NCAR Community Atmosphere Model version 6 (CAM6) reveal that the canonical deepening of the Aleutian Low in response to the 2023/24 El Niño was largely offset by ridging driven by SST warming trends in the tropical Indo-Atlantic; SST cooling trends in the tropical eastern Pacific played a lesser role.  In addition to background SST trends, a strong Indian Ocean SST dipole event plus internal atmospheric variability also contributed to the anomalous extratropical wintertime atmospheric circulation in 2023/24.  Our results underscore the importance of considering the modulating influence of evolving long-term SST trends, both natural and anthropogenic in origin, on teleconnections and associated climate impacts driven by ENSO.