Keeping oceans young and productive: - Upwelling and Downwelling Oceans cover two thirds of our planet thus they can be regarded as one of the major factors in shaping this blue marble in space. But oceans just don’t result in varying gradient of humidity that gives rise to different vegetations and ultimately widely different biomes when coupled with other factors such as differential exposure to solar radiation, and inherent soil type. Oceans are living systems that themselves support numerous life forms whether plant or animal; whether microscopic phytoplankton or the gigantic mammals like whales. There are gradients in oceans too whether it is in terms of productivity, density, salinity or in terms of nutrient composition. While coral reefs have one of the highest productivity open oceans have one of the lowest of all biomes. Now since nutrient composition and productivity varies there must be mechanisms similar to nutrient recycling on land that enables continued growth and productivity. The rates of vertical recycling of water is extremely slow in oceans, water from bottom of ocean may take thousands of years to reach the surface of ocean again. There are some specific areas where water rises known as sites of upwelling and some sites where water descends mostly in areas of convergence of warm and cold currents in the Polar Regions. What is upwelling exactly?
It is an oceanographic phenomenon with large biological implications. Precisely it is the wind driven movement of dense, cooler and nutrient rich water from below the photic zone, replacing the warmer, usually nutrient-deficient surface water. The reason why this layer of water is nutrient rich is that the density gradient of oceans falls rises and then falls again with an increase in depth (we must remember that the highest density of water is at 4 degree centigrade not below that) hence the organic matter such as waste products of marine organisms and their dead remains are trapped in this layer....
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