Equatorial Counter Current

This apparent paradox is concisely explained by Sverdrup theory, which shows that the east-west transport is governed by the north-south change in the curl of the wind stress.

[4] Klaus Wyrtki, who first reported this connection, suggested that a stronger than normal NECC could be the cause of an El Niño because of the extra volume of warm water it carried eastwards.

The NECC is a direct response to the meridional changes in the coriolis parameter and the wind stress curl near the Intertropical Convergence Zone (ITCZ).

The magnitude of the NECC weakens substantially east of 38°W due to water being absorbed by the westward equatorial current south of 3°N.

[10] Physically, this implies that the altered convection in the Pacific Ocean due to El Niño drives changes in the meridional gradient of wind stress curl over the equatorial Atlantic.

[11] At the surface, the current is located on the southern slope of the North Equatorial Trough, a region of low sea level which extends from east to west across the Pacific.

The low sea level is a result of Ekman suction caused by the increased easterly winds found just to the north of the Intertropical Convergence Zone (ITCZ).

Klaus Wyrtki was the first to report the connection, in the early 1970s, based on analysis of tide-gauge measurements at Pacific island stations on either side of the current.

On the basis of this analysis, Wyrtki hypothesized that such an unusually strong NECC in the western Pacific would lead to an anomalous accumulation of warm water of the coast of Central America and thus an El Niño.