The role of interannual ENSO events in decadal timescale transitions of the Interdecadal Pacific Oscillation

Journal Article · Wed May 12 00:00:00 EDT 2021 · Climate Dynamics

DOI:https://doi.org/10.1007/s00382-021-05784-y· OSTI ID:1813444

Meehl, Gerald A. ^[1]; Teng, Haiyan ^[2]; Capotondi, Antonietta ^[3]; Hu, Aixue ^[4]

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1. National Center for Atmospheric Research, Boulder, CO (United States); National Center for Atmospheric Research
2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
3. Univ. of Colorado, Boulder, CO (United States); National Oceanic and Atmospheric Administration (NOAA), Boulder, CO (United States)
4. National Center for Atmospheric Research, Boulder, CO (United States)

The build-up of decadal timescale upper ocean heat content in the off-equatorial western tropical Pacific can provide necessary conditions for interannual El Niño/Southern Oscillation (ENSO) events to contribute to decadal timescale transitions of tropical Pacific SSTs to the opposite phase of the Interdecadal Pacific Oscillation (IPO). This can be viewed as a corollary to subseasonal westerly wind burst events contributing to El Niño interannual timescale transitions. In this work, a long pre-industrial control run with CESM1 is analyzed to show that there is a greater chance of ENSO activity to contribute to an IPO transition when off-equatorial western Pacific Ocean heat content reaches either a maximum (for El Niño to contribute to a transition to positive IPO) or minimum (for La Niña to contribute to a transition to negative IPO) as seen in observations. If above a necessary ocean heat content threshold, the convergence associated with westerly anomaly near-equatorial surface winds associated with El Niño activity can draw that heat content equatorward to sustain anomalously warm western and central Pacific SSTs. These are associated with positive precipitation and convective heating anomalies, a Gill-type response and wind stress curl anomalies that continue to feed warm water into the near-equatorial western Pacific. These conditions then sustain the decadal-timescale transition to positive IPO (with the opposite sign for transition to negative IPO). Associated central equatorial Pacific convective heating anomalies produce SLP and wind stress anomalies in the North and South Pacific that can excite westward-propagating off-equatorial oceanic Rossby waves to contribute to the western Pacific thermocline depth and consequent heat content anomalies.

• Research Organization: National Center for Atmospheric Research, Boulder, CO (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER)
• Grant/Contract Number: 89243018SSC000007
• OSTI ID: 1813444
• Journal Information: Climate Dynamics, Journal Name: Climate Dynamics Vol. 57; ISSN 0930-7575
• Publisher: Springer-Verlag
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
ENSO
El Nino
Interdecadal Pacific Oscillation
decadal variability
ocean heat content