Ocean Dynamics are Key to Extratropical Forcing of El Nino

Chakravorty, Soumi; Perez, Renellys C.; Anderson, Bruce T.; Larson, Sarah M.; Giese, Benjamin S.; Pivotti, Valentina

doi:10.1175/JCLI-D-20-0933.1

i

Ocean Dynamics are Key to Extratropical Forcing of El Nino

2021
By Chakravorty, Soumi ; Perez, Renellys C. ; Anderson, Bruce T. ; ...

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Journal Title:

Journal of Climate
Personal Author:

Chakravorty, Soumi ; Perez, Renellys C. ; Anderson, Bruce T. ; Larson, Sarah M. ; Giese, Benjamin S. ; Pivotti, Valentina
NOAA Program & Office:

OAR (Oceanic and Atmospheric Research) ; AOML (Atlantic Oceanographic and Meteorological Laboratory) ; CIMAS (Cooperative Institute for Marine and Atmospheric Studies)
Description:

El Niño–Southern Oscillation (ENSO) has been recently linked with extratropical Pacific Ocean atmospheric variability. The two key mechanisms connecting the atmospheric variability of the extratropical Pacific with ENSO are the heat flux–driven “seasonal footprinting mechanism” (SFM) and the ocean dynamics–driven “trade wind charging” (TWC) mechanism. However, their relative contributions to ENSO are still unknown. Here we present modeling evidence that the positive phase of the SFM generates a weaker, short-lived central Pacific El Niño–like warming pattern in the autumn, whereas the TWC positive phase leads to a wintertime eastern Pacific El Niño–like warming. When both mechanisms are active, a strong, persistent El Niño develops. While both mechanisms can trigger equatorial wind anomalies that generate an El Niño, the strength and persistence of the warming depends on the subsurface heat content buildup by the TWC mechanism. These results suggest that while dynamical coupling associated with extratropical forcing is crucial to maintain an El Niño, thermodynamical coupling is an extratropical source of El Niño diversity.
Keywords:

Atmosphere–ocean Interaction Climate Models El Niño Extratropics
Source:

Journal of Climate, 34(21), 8739-8753
DOI:

https://doi.org/10.1175/JCLI-D-20-0933.1
Document Type:

Journal Article
Rights Information:

CC BY
Compliance:

Submitted
Main Document Checksum:

urn:sha256:17a03597cda4fff53d5fd47bf10930edb724301a71c5ec104ff0ab8547036622
Download URL:

https://repository.library.noaa.gov/view/noaa/32917/noaa_32917_DS1.pdf
File Type:

[PDF - 4.25 MB ]

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