North Equatorial Current

Another subsequent result of the Ekman transport is the upwelling, which occurs in between the NEC and the SEC, where a massive water divergence at the sea surface takes place.

The NEC, the SEC and the ECC play an important role in the climate system causing various of climate patterns, such as El Niño–Southern Oscillation (ENSO), the Atlantic Meridional Mode (AMM), the Atlantic Multidecadal Oscillation (AMO) and the seasonal monsoon in the Indian ocean.

When the current reaches the west end, the Philippines, it splits into two western boundary flows.

[3] This North Equatorial Current Bifurcation (NECB) plays an important role in the south Asian climate system.

As currently, climate change is more and more evident, thus, leading to a more amplified migration of the NECB.

As a result, this amplification of the migration may lead to redistribution of the water mass and heat transport along the western boundary, and thus warm pool and monsoon climate.

Instead of interannual variability, the NEC shows a strong seasonality, in which NECC is stronger from July to December, weaker from January to June.

This strong northward surface transport is well known as the upper component of the Atlantic Meridional Overturning Circulation (AMOC).

On a seasonal time scale, variability of the heat transport is responsible for the tropical sea temperature anomaly.

The temperature anomaly at the sea surface is a possible cause that leads to Atlantic hurricane season.

The NEC is more southward than the other two oceans, which drives the Equatorial Counter Current to the southern hemisphere.

During January and February, thanks to the prevailing northeast wind, the NEC travels all the way to the east coast of Somalia and joins the Somali Current flowing towards the southwest to feed the SECC.

While during July and August, the location of the NEC moves southward and the Somali Current reverses.

During the transition of these two phases, specifically around May and November, the NEC becomes very weak, almost invisible in Figure 3.

Instead of the NEC, a strong eastward current is found near the equator, known as the Wyrtki jets.

North Equatorial Current (in black labeled N. Equatorial)
a) and b) show the mean zonal surface velocity in Pacific during El Niño (1997) and La Niña years (1998). Positive values (red) represent eastward flow, negative values (blue) for westward flow. All the data plotted in this article is obtained from the GODAS dataset. [ 2 ]
a) shows the mean zonal surface currents within the Atlantic in the first half-year (Jan-Jun) of 1997. b) shows the second half (Jul-Dec). These two figures show a strong seasonality, with NECC stronger during July to December. Positive values (red) represent eastward flow, negative values (blue) for westward flow.
This figure shows the mean zonal surface current of different periods in the Indian Ocean. a), b) and c) are currents during January and February, during July and August, and in May, respectively. Positive values (red) represent eastward flow, negative values (blue) for westward flow.