Role of thermocline feedback in the increasing occurrence of Central Pacific ENSO.

Zhu, Xiaoting , Chen, Shengli, Greatbatch, Richard John , Claus, Martin and Xing, Jiuxing (2021) Role of thermocline feedback in the increasing occurrence of Central Pacific ENSO. Regional Studies in Marine Science, 41 . Art.Nr. 101584. DOI 10.1016/j.rsma.2020.101584.

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Supplementary data:

Abstract

Highlights:
• The pivot point for sea level shifted to the west of the Nino4 region in the 2000s.
• This enabled the thermocline feedback to increase strongly in the Central Pacific.
• The resulting increase in CP events maintains the pivot point to the west, a positive feedback mechanism.

Monthly mean sea level variations computed using a linear, reduced-gravity, multi-mode model are combined with satellite measurements to explore why Central Pacific (CP) ENSO events occur more frequently since 2000s. The pivot point for sea level (and hence thermocline) variations has shifted westward in response to an increase in zonal wind stress variance in the western equatorial Pacific. As a result, the Nino4 region is increasingly to the east of the pivot point enabling the thermocline feedback to operate there, strengthening the Bjerknes feedback mechanism in the Nino4 region and leading to an increase in the occurrence of CP events. The increased variance of wind stress in the western Pacific is, in turn, caused by the resulting increase in the frequency of CP events. These arguments imply a positive feedback in which CP events are self-maintaining and suggest that they may be part of the natural variability of the climate system and could occur without the need for changes in external forcing.

Document Type: Article
Funder compliance: info:eu-repo/grantAgreement/EC/FP7/603521
Keywords: Thermocline feedback; ENSO; Tropical Pacific; Bjerknes feedback; Shallow water model
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-OD Ocean Dynamics
OceanRep > SFB 754
Main POF Topic: PT2: Ocean and Cryosphere
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1016/j.rsma.2020.101584
ISSN: 2352-4855
Projects: SFB754, ATMOS-MODINI, SACUS, PREFACE
Date Deposited: 05 Jan 2021 10:44
Last Modified: 13 Jan 2021 13:15
URI: http://oceanrep.geomar.de/id/eprint/51382

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