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2/18/2007

Wind shifts devastate ocean life

Earth/Science News
San Francisco, Ca. USA
Feb 17, 2007

The delicate interplay between the oceans and atmosphere is changing with catastrophic consequences. Entire marine ecosystems have been wiped out, devastating populations of sea birds and larger marine mammals. These "dead zones" occur where there are disturbances to the nutrient-rich ocean currents, which are driven by coastal winds. Extreme marine suffocations have occurred off the west coast of the US every year for the last five years. The most intense event, which left the ocean floor littered with the carcasses of crabs, happened in 2006. It was unlike anything measured along the Oregon coast in the PAST 50 YEARS. Other coastal countries including Chile, Namibia and South Africa have also been affected. Observations along the west coast of the US suggest that the upwelling in the ocean is being disrupted, changing its timing and intensity. For example, in 2005 the upwelling was delayed which meant that the plankton blooms did not occur, leading to a collapse in fish populations. This particularly hit migrating salmon, which pass along the coast in April and May every year. An even more catastrophic event occurred in 2006 when the amount of upwelling doubled, leading to a huge influx of nutrients and a supercharged plankton bloom. When these sank to the ocean floor they stripped the water column of oxygen, creating a 3,000 sq km (1,150 sq miles) dead zone, where creatures unable to swim away suffocated en masse. Crabs, worms and sea stars all perished in the anoxic water. The event was so severe that the researchers fear that marine life cannot return to the area. "In previous years, fish that have escaped the low-oxygen area appear to have returned once the oxygen was renewed. This year may be different, however, because unlike earlier years, the living habitat was also suffocated." Researchers believe the cause of these events was changes in the intensity of the coastal winds, perhaps brought about by global warming. "What we know from the climate change models is that the land will warm more than the sea." It is this difference in temperature and pressure that drives the winds. "As you intensify that gradient - that will drive the stronger winds." "Climate models predict increasing uncertainty with wild fluctuations. We should expect more surprises
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