Why are the world's great deserts and calmest seas named after horses?

Nature · Published 3 October 2026 Swipe more like this →

In short: Located roughly 30 degrees north and south of the equator, the horse latitudes are high-pressure zones defined by sunny skies and stagnant winds. While their influence on global climate is profound, the origin of their peculiar name remains a subject of intense debate among historians and maritime experts.

The horse latitudes, also known as subtropical ridges, are atmospheric high-pressure belts that encircle the Earth. They form as air rising at the thermal equator moves toward the mid-latitudes, cools, and sinks. This subsidence creates the calm, dry conditions responsible for many of the world's major deserts, including the Sahara, the Arabian, the Mojave, and the Atacama. Because these regions lack consistent wind, they have historically challenged sailing vessels, which often became becalmed for days or weeks.

The most popular explanation for the name is a grim maritime legend: ships transporting horses to the Americas would stall in these high-pressure zones, forcing crews to throw the animals overboard to conserve dwindling water supplies. However, skeptics offer alternative theories. One suggests the term stems from the 'dead horse' ritual, where sailors celebrated paying off debts incurred during long voyages. Another theory posits that 'horsed' was a nautical term for a ship being carried by a strong current, while a final hypothesis suggests a mistranslation of the German word 'Rossbreiten'.

Beyond their etymology, these latitudes are vital to global weather. They shift poleward in summer and equatorward in winter, a movement strongly correlated with the Intertropical Convergence Zone. Their position and strength dictate the tracks of tropical cyclones and the intensity of monsoon regimes. During El Niño cycles, for instance, the ridge's displacement can significantly alter cyclone landfall frequencies in Asia and the Atlantic. When surface winds remain light, the sinking air can trap particulates, leading to widespread haze in urban areas beneath the ridge.

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