Cool water surges could affect fish stocks

PARIS (Reuters) - Surges of cool waters from the depths of the Atlantic Ocean became stronger off Morocco in the 20th century, apparently because of global warming that could affect fish stocks, a study showed on Thursday. The report, in the journal Science, said there was evidence of similar upwellings in the Arabian Sea, off California, Peru and Chile, also apparently driven by higher temperatures and shifts in winds tied to greenhouse gases.The upwellings could be commercially important because areas where cooler waters rise near coasts provide about 20 percent of the world's fish catch even though they cover less than one percent of the world's ocean surface, they said.But the scientists, at research institutes in Germany, Australia and Romania, did not predict whether fish stocks would get bigger or smaller because of the increased upwelling."Upwelling regions...show extremely high levels of biological activity, yet the ecosystem response in these regions is dependent on a complex balance of temperature, ocean chemistry, ocean circulation, and fishing pressure," it said.The report, reconstructing a 2,500-year record of temperatures based on seabed sediments off Morocco, said surface waters were the coolest from 1965-98 because of cool waters from the depths."These results strongly imply that upwelling may continue to intensify with future increased levels of atmospheric carbon dioxide and global warming," Helen Victoria McGregor of the University of Bremen and co-authors wrote.Almost all scientists say that a build-up of carbon dioxide in the atmosphere, mainly from burning fossil fuels, is blanketing the planet and driving up temperatures.