Working the 70-Meter Line

05/13/2009

Story by Helen Fields and photos by Chris Linder

Bering Sea, May 8, 2009 -- The ship is working its way back towards Dutch Harbor along the "70-meter line"—a line along the sea where the water is 70 meters (230 feet) deep. Most of the science sampling is over now, but the hydrography team is going full blast. They study the water itself: how warm (or cold) it is, how salty it is, and where the nutrients are.

When you look at the ocean, it all looks like water. But water in the ocean is not all the same, and it can actually have structure. For algae to bloom, the water has to be stratified; that means there’s a layer of water near the surface that is different from the layer below, and holds the algae more or less in place. Algae has to be near the surface because they require sun to live; if they sink down into darkness, they’re in trouble. Water can be stratified either by temperature or salinity. The algae don’t care, as long as they’re getting sun.

Detailed physical measurements of the water show scientists what kind of environment the organisms in the Bering Sea are living in. Is it warm? Cold? Mixed? Warm in some places, cold in other places? Too darn salty for comfort? The physical oceanographers on the hydro team are finding out.