A sketch of the surface topography across the equatorial current system. NEC: North Equatorial Current, ECC: Equatorial Countercurrent, SEC: South Equatorial Current. The sea surface slopes up towards the north across the NEC, producing high pressure on the right of the current (which is in the northern hemisphere); it slopes down towards the north across the ECC, again producing high pressure on the right of the current (looking downstream). The SEC flows in the same direction as the NEC but is found on both sides of the equator, so the sea surface slopes up to the north, in the same way as it does across the NEC, where the SEC is flowing in the northern hemisphere; it slopes up to the south across the SEC in the southern hemisphere, producing high pressure on the left of the current.

The variation of sea level necessary to maintain the pressure distribution is of the order of 0.2 - 0.4 m and cannot be seen when looking at the ocean. It has been verified through measurements of the shape of the ocean surface from satellites.

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