Читать книгу Life in the Open Ocean - Joseph J. Torres - Страница 21

For our purposes, ocean currents are of two basic types: surface and deep. Surface currents (Figure 1.5) are responsible for transport of about 10% of the oceanic volume and extend to about 400 m. The Earth’s prevailing winds interact with surface waters through friction, literally driving the water before them and forming large current systems, or gyres, in each of the ocean basins. The gyres circulate clockwise in the northern hemisphere and counterclockwise in the southern. The trade winds, persistent surface easterlies between the equator and about 30° latitude, are a major driving force for the central ocean gyres and were critical to past exploration and commerce. Deep‐ocean currents (Figure 1.6) transport the remaining 90% of the oceanic volume and are the result of the Earth’s thermohaline circulation or the “Great Ocean Conveyor” (Broecker 1992).