Is the freeze coming?
the Aswan dam on the Nile river in Egypt is depriving the Mediterranean Sea of freshwater, and this has put the Northern hemisphere at the risk of another ice age, says Bob Johnson, oceanographer at the University of Minnesota, Minneapolis, usa . The Mediterranean is becoming increasingly saline and dense in the absence of inflow of freshwater. The turbid waters of the Mediterranean pushes its way north through the Strait of Gibraltar towards the Arctic, where they could disturb existing ocean currents and lead to large-scale formation of ice, he claims ( New Scientist , Vol 155, No 2092).
The only way to prevent this would be to build a giant barrage at the Strait of Gibraltar that would keep the dense water of the Mediterranean from escaping into the Arctic, suggests Johnson. A barrage such as this would be around 420 times the volume of the Great Pyramid of Egypt and would reduce the flow from the Mediterranean by about 80 per cent.
Dramatic as the claims are (Johnson admits that it is a "pretty far-out idea'), he suggests that it is "worth floating' and that he is "quite serious about it'. He claims that there is fossil evidence to suggest that a strong Mediterranean outflow has pushed more water in the Atlantic Gulf Stream west of Greenland into the Labrador Sea in the past, warming it in the process. A warmer Labrador Sea could lead to the expansion of ice sheets in the Arctic, Johnson argues.
This warmth increases evaporation, and hence, snowfall, Johnson says. This, in turn, promotes the formation of ice packs in the northern regions of Canada. As heat is reflected back by ice, the growth of ice sheets would lead to further ice formation and would significantly cool the Arctic, he asserts. This was the reason behind ice ages in the past and the phenomenon is likely to repeat itself, suggests Johnson.
Gifford Miller from the University of Colorado, usa , has produced evidence in the form of marine fossils in 1992 to indicate that the last ice age was caused by ice packs formed in the Arctic nearly 120,000 years ago. Interestingly, this was also the time when the Arctic was at its warmest. Glaciologists do not deny that such processes could trigger another ice age.
Johnson says that the Aswan dam has recreated the situation that had caused the last ice age in the Arctic region. He says that as the setting in of this ice age might coincide with the effects of global warming, the tropics and the Southern hemisphere might get warmer, just as the Northern hemisphere chills out.
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