User talk:Taneja rajat

The Deep Atlantic Conveyor
The Deep Atlantic Conveyor

The Nordic Heat Pump (again)

Consider again the strawberries in Norway. It is the warm currents entering the Norwegian Sea that provide the extra heat (as much as 30 percent greater than the “background” heat) to keep Norway warm enough to grow strawberries, as well as apples, pears and plums. Some of this water flows back into the North Atlantic as a cold current along the Greenland coast, laden with icebergs and pack ice, after some peregrinations. Much of it cools and sinks, causing deep convection in the Norwegian Sea. The cold deep water made in this fashion flows over sills between Greenland, Iceland and Denmark and feeds the deep waters of the North Atlantic.

The import of warm surface water and the export of cold deep water sets up a heat pump which keeps northern Europe pleasantly free of a Greenland-type ice cap. This is known as the "Atlantic Heat Conveyor" or also the "Nordic Heat Pump." In fact, the climate of all of northwestern Europe greatly depends on this heat piracy associated with the Nordic Heat Pump, which helps move heat from the Caribbean into the northern North Atlantic, and even from the tropical regions of the South Atlantic.

The Oceanic Conveyer Belt

What if we now want to follow the deep water after it sinks and observe its course through a variety of ocean basins? The best way to study this is to map out the oxygen content of the deep-water. Where the deep water is young (that is, where it came from the surface quite recently), its oxygen content is high. Where it is old (that is, where it has not seen the surface for a long time), much of its oxygen has been spent in bacterial decay of organic matter, and in respiration. (The organic matter, of course, is produced in the sunlit surface waters and gets into the deep water by sinking, in particles.) As we should expect, from the distribution of deep-water sources, the Atlantic deep waters are young, and those of the North Pacific are old.

Although an oversimplified model, the pattern we observe is as follows: The North Atlantic is filled with young surface waters, which it largely receives because of the sinking of waters around Greenland. The North Pacific is filled with older deep waters which arrive from the south after a long voyage from Antarctica — and even there these waters were not entirely "young" when they sank, because they were not at the surface long enough to thoroughly reset their chemistry by exchange with the atmosphere.

In a gross (but memorable) oversimplification, we can say that the Atlantic gives its deep waters to the Pacific, and receives surface waters in exchange. This has important consequences for the nutrient distribution in these oceans. The Atlantic loses nutrient-rich deep water, while the Pacific gains them and sends nutrient-poor waters away via the Indian Ocean. Scripps oceanographer Joseph Reid puts it well: "They give us their best, we give them our worst." Thus, deep circulation removes nutrients from the Atlantic and piles them into the Pacific. Taneja rajat (talk) 08:33, 24 March 2009 (UTC)Rajat taneja