Current-Generating Mechanism for El Ni\~no & La Ni\~na, an Data Evidence from Integrated ESMD Method

TL;DR

This paper proposes a new horizontally dependent current-generating mechanism for El Niño and La Niña, supported by data analysis using the ESMD method, challenging traditional east-west feedback theories.

Contribution

It introduces a novel current-based mechanism for ENSO, emphasizing horizontal ocean current changes over east-west feedback, supported by integrated data analysis.

Findings

CECC and NECC changes trigger positive anomalies.

Warm water transport initiates different ENSO types.

South Equatorial Current branches influence negative anomalies.

Abstract

Different to classical theories which emphasize east--west feedback along the equator, data analyses via the extreme-point symmetric mode decomposition (ESMD) method support a new viewpoint that the El Ni\~{n}o--Southern Oscillation (ENSO) cycle is horizontally dependent, rather than vertically dependent. The consistency between the ocean current changes and sea-surface temperature anomalies results in a current-generating mechanism for El Ni\~{n}o and La Ni\~{n}a events. The corresponding new findings are as follows: (1) The appearance of the Central Equatorial Countercurrent (CECC) and the enhancement of the North Equatorial Countercurrent (NECC) are primary causes for the occurrences of positive anomalies in the central and eastern Pacific, respectively. (2) In addition to the contribution from the CECC, initiations of the eastern and central Pacific types of El Ni\~{n}o events are mainly caused by the southward transport of warm water from the high-temperature sea-area off Central America, and from the eastern low-speed gap of the NECC, respectively. (3) The northern and southern branches of the South Equatorial Current contribute to the negative anomalies in the eastern and central Pacific, respectively. Particularly, the later transfers cold water from the southeast to the central equatorial Pacific in a direct way, and this implies the crack of the ENSO-asymmetry problem.