Water And Oceanography

How the Oceans Currents Affect Weather



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Little thought was given concerning the relationship between global weather patterns and ocean currents until the 1960's. With the increasing use of computer modelling to construct scenarios spanning many thousands of years by extrapolation of limited raw data, a picture began to emerge in the 1980's when evidence suggesting a fragile balance existed where disruptions to the North Atlantic current caused significant historical shifts in global climate. With scientists of the 21st century increasingly concerned about the global warming, studies of the ocean currents are intensifying to determine the full impact on this delicate balance of heat exchange should a significant change occur.

With an average depth of 3 700m, water at the lower levels of the ocean are near freezing temperatures while the upper few meters store heat energy. Water is also an efficient thermal conductor with only a narrow region or band separating warm water from cold. The engine fuelling ocean and atmospheric circulations is the sun whereby radiated heat warms the air and water surface at a different rate. Heat energy absorbed on the surface of the ocean causes warm air to rise while cooler air moves in to replace it, in other words wind. Ocean surface currents are in turn driven by this wind that is augmented by the influence of the earth's rotation with respect to relative position of the continents

Salinity at the two poles is denser than water in the tropics and this difference is caused by surface evaporation in warm areas, and freezing temperatures where ice holds very little of the salt. The effect of this imbalance is the deep ocean circulation that spans thousands of years. It is believed that a small change to the balance of this deep-water circulation occur, the earth will experience a significant shift in climate. Empirical evidence of major climate change suggests there is an established pattern of climate shift from ice age to temperate.

The movement of warm and cold water between the two poles is mirrored in a similar heat exchange in the atmosphere. The difference in the two rates of heat transfer is disproportionate in that rate of heat transfer in air is many times faster than the same process in water. It is for this reason that scientists are of the opinion where a small change to the ocean currents will trigger a significantly larger atmospheric response global heating or cooling.

We now know the earth has experienced many hundreds of ice ages in its estimated 6.7 billion years in existence. Whether or not current predictions of a more rapidly shifting climate change is imminent, there is little doubt in what role ocean currents have in this cycle, and in weather patterns on a global scale.

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