Radio Script
1998

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North Pacific Getting Less Salty
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STORY: Although the North Pacific Ocean is a very big, deep place, most life there thrives within the first few hundred feet of the surface. Deep ocean currents bring up nutrients that feed the plankton that in turn support all other life in the sea. Only these days, nutrients aren't making it to the surface. The reason: there might be too much fresh water.

Tom Royer is an oceanographer at Old Dominion University in Virginia.

ROYER: "One of the things that seems to be happening is that the upper layer salinity is decreasing. There seems to be an increase in the amount of fresh water coming into the system. It could put a lid on the North Pacific. It could keep nutrients from coming up into the upper layers."

Fresh water, being lighter than salt water, forms a layer near the ocean's surface. Normally this layer, some 300 feet thick, is thoroughly mixed by wind and ocean currents. But as more and more fresh water enters the sea, the harder it is for the ocean to mix nutrients into it. The result, says Royer, may be a dramatic change in the ocean's ability to support life.

ROYER: "One of the things we're seeing throughout the Pacific is this freshening of the upper layer and the shallowing of the mixed layer. As the mixed layer's depth decreases, it's going to be tougher to get the nutrients into the upper layers, and that could change the amount of plankton available, and change the carrying capacity of the ocean."

Tom Weingartner, an oceanographer at the University of Alaska Fairbanks, says too much fresh water could explain the recent disappearance of plankton in parts of the North Pacific.

WEINGARTNER: "The nutrients necessary for phytoplankton production were depleted from the surface layers of the ocean. That has not been observed before in the Gulf of Alaska. So that's very unusual. Other things that have been noticed are a change in the phytoplankton species composition in the Bering Sea. That is usually dominated by a community called diatoms, but the last couple of summers it has been dominated by coccolithophors, a very different phytoplankton species."

Still unexplained is exactly where all this fresh water is coming from. Tom Royer says the fresh water could be the result of changing weather patterns and global warming that is melting glaciers and the polar ice caps.

OUTRO: For Arctic Science Journeys, this is Doug Schneider, reporting from Fairbanks, Alaska.