What explains the eastward flow of the equatorial counter-current?

The correct answer is Convergence of the two equatorial currents.

Key Points

• The equatorial countercurrents are driven by a distinct surface wind pattern in the tropics.
• Strong westward trade winds result in westward surface flow in most of the tropical Atlantic and Pacific Oceans.
• However, several hundred mi. (km.) north of the equator, the winds are much weaker, in comparison
• The stronger winds to the south pile up water where the winds are weak.
• As a result, the surface of the ocean can be up to 6 in. (15 cm.) higher and the thermocline as much as 328 ft. (100 m.) deeper than it is directly to the north.
• The excess water flows eastward under the influence of the Earth’s rotation, giving rise to the equatorial countercurrents.
•  In the Indian Ocean, the equatorial countercurrent is located several hundred mi. (km.) south of the equator.
• In all three oceans, the equatorial countercurrent is concentrated in the upper 656 ft. (200 m.), above the thermocline.
• The intensity of the equatorial countercurrent varies from season to season and from month to month.
• The strongest seasonal changes occur in the Atlantic Ocean.
• Eastward flow reaches a maximum in the summer and fall, with speeds of up to 12 in. (30 cm.) per second, and disappears in the spring.
• Seasonal changes are weaker in the Pacific Ocean. Here, the equatorial countercurrent exists year-round, and is strongest in the fall and winter, with speeds slightly

Important Points

• Thermocline: Region of strongest decrease in temperature with increasing depth.