Ocean life depends on single circulation pattern in Southern ...( A study has shown that marine life arou...)

The results suggest that ocean life may be more sensitive to climate change than previously believed because most global warming predictions indicate that major ocean circulation patterns will change. While oceanographers have identified many ocean circulation patterns, the study found that three-quarters of all biological activity in the oceans relies on this single pattern.

"When we shut off this one pathway in our models, biological productivity in the oceans drops to one-quarter of what it is today," said Jorge Sarmiento, a Princeton oceanographer who led the study published in the Jan. 1, 2004, issue of Nature. Marine organisms account for half all biological productivity on Earth.

The discovery helps oceanographers settle a longstanding question about what keeps the world's oceans fertile. Most biological activity in the ocean is concentrated near the surface where an abundance of microorganisms perform photosynthesis and support marine food chains. These organisms and their byproducts slowly sink from the surface, decomposing along the way and carrying nutrients to the deep ocean. Until now, it has not been clear how the surface becomes replenished with the nutrients that seemed lost to the deep ocean.

Previous research has shown that ocean water does not mix well across layers of equal density, which are mostly oriented horizontally in the ocean. Once the organic matter sinks to the abyss, it takes a long time for nutrients to cross the layers and return to the surface. Without a mechanism to bring deep water back to the surface, the oceans would lose about one-fiftieth of their nutrients to this sinking process each year, Sarmiento said.

Sarmiento and colleagues identified what amounts to an enormous co
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Contact: Patty Allen
pallen@princeton.edu
609-258-6108
Princeton University
31-Dec-2003