The “Horse Latitudes” are oceanic regions known for distinctive atmospheric conditions that historically posed significant challenges for sailing vessels. Understanding these latitudes involves exploring their geographical characteristics and the scientific principles governing their weather patterns.
Defining the Horse Latitudes
The Horse Latitudes are located approximately between 30 and 35 degrees north and south of the equator. These regions are characterized by consistent atmospheric high-pressure systems, leading to light, variable winds or calm periods. The weather typically features sunny skies and very little precipitation, creating warm and dry conditions. These latitudinal bands are also referred to as subtropical ridges or highs.
The northern band is called the “calms of Cancer,” while the southern band is known as the “calms of Capricorn.” This dry, high-pressure environment contrasts with the rainy, low-pressure conditions found closer to the equator. The steady conditions within these belts contribute to the formation of many of the world’s major deserts on landmasses at similar latitudes.
The Origin of the Name
The most widely accepted explanation for the name “Horse Latitudes” stems from early sailing ships. Spanish vessels, in particular, transported horses to the West Indies and the Americas. These ships often became becalmed in these windless regions for extended periods, sometimes for days or even weeks.
When stalled, ships faced rapidly dwindling supplies of fresh water and food. To conserve precious water for the human crew, the difficult decision was sometimes made to throw horses, dead or dying, overboard. This grim necessity led to the adoption of the term. While other theories exist, such as a “dead horse” ritual, the account of jettisoning livestock is prominent in maritime lore.
The Atmospheric Phenomena
The calm conditions of the Horse Latitudes are a direct result of global atmospheric circulation patterns, specifically the Hadley Cells. Warm, moist air rises near the equator, creating a low-pressure zone. As this air ascends, it cools and releases moisture, leading to precipitation in equatorial regions. This now-drier air then moves poleward in the upper atmosphere.
This cooler, denser air begins to descend back towards the Earth’s surface. This downward movement, known as subsidence, compresses and warms the air, leading to clear skies and a lack of cloud formation and wind. This continuous cycle forms the subtropical high-pressure belts, which are the Horse Latitudes.
Impact on Historical Navigation
For historical sailing ships, the Horse Latitudes presented considerable navigational hazards. Vessels could become stranded for prolonged durations, significantly extending journey times from weeks to months.
Extended voyages led to severe depletion of vital supplies, including food and, most critically, fresh drinking water. Crews and cargo, including livestock, suffered immensely from starvation and dehydration. These challenges underscored the limitations of wind-powered maritime travel. While the meteorological phenomenon persists, the advent of steam and later engine-powered vessels largely mitigated these dangers, allowing ships to traverse these areas without relying on wind.