The equator is a curious place. Despite high solar radiation that is relatively steady year-round, oceanographers know to pack a sweater when sailing there. Compared with the 28°C surface temperatures of the adjacent tropical waters, the eastern halves of the equatorial Pacific or Atlantic Oceans have surface temperatures up to 10°C colder, particularly in boreal summer months. The currents are equally odd. Prevailing easterly winds over most of the tropical Pacific and Atlantic Oceans suggest westward flowing currents. Yet, eastward currents oftentimes outweigh those flowing toward the west. Motivation for the first quantitative theory of the large scale, wind driven ocean circulation, in fact, came from observations of the Pacific North Equatorial Counter Current (NECC), an eastward surface current that flows halfway around the Earth counter to the prevailing winds.

Weisberg, R.H. 2001. An observer’s view of the equatorial ocean currents. Oceanography 14(2):27–33, https://doi.org/10.5670/oceanog.2001.39.

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