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

Abstract

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.more » 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.« less

Authors:

Meehl, Gerald A.  ^[1];

• Search DOE PAGES for author "Meehl, Gerald A."
• Search DOE PAGES for ORCID "0000-0002-8760-9534"

Teng, Haiyan ^[2]; Capotondi, Antonietta ^[3]; Hu, Aixue ^[1]

---

+ Show Author Affiliations

1. National Center for Atmospheric Research, Boulder, CO (United States)
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)

Publication Date:

Wed May 12 00:00:00 EDT 2021

Research Org.:

National Center for Atmospheric Research (NCAR), Boulder, CO (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Biological and Environmental Research (BER)

OSTI Identifier:

1813444

Grant/Contract Number:  

89243018SSC000007; IA-1947282; 1852977

Resource Type:

Accepted Manuscript

Journal Name:

Climate Dynamics

Additional Journal Information:

Journal Volume: 57; Journal ID: ISSN 0930-7575

Publisher:

Springer-Verlag

Country of Publication:

United States

Language:

English

Subject:

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