Working the 70-Meter Line




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.

How the Ship Goes

Bering Sea, May 2, 2009 -- How does the icebreaker Healy go? Like a car. It’s got a throttle for a gas pedal and a wheel for…a steering wheel. It also has an engine – actually, four. And it goes through water, so instead of wheels it has propellers. Ok, my car analogy just fell apart.

Today we’re looking at how the ship moves, from the people who drive the ship up front on the bridge, 70 feet above the water line, to the propellers and rudders under the ship’s rear.

Sounds of the Ice

Bering Sea, May 1, 2009 -- The ice was different today. The ship spent the night heading north, back to the area where we were about two weeks ago. The last few times we were supposed to stop at the ice, there wasn’t a big enough piece for everyone who does work on the ice to get off the ship. Now that we’re back in the north, today a larger group of scientists was able to work on the ice.

Ned Cokelet, an oceanographer at the National Oceanic and Atmospheric Administration, measures the ice itself as a member of the hydrography team. "Today the ice was much warmer," he says. "The ice was just slightly colder than the freezing temperature of water." He searches for a word to describe the condition of the ice today and comes up with "saturated," then "waterlogged."

The Bering Sea has sea ice only in winter. Unlike in the Arctic Ocean, where some ice lasts through the summer and there are areas where multi-year ice can stop an icebreaker like Healy in its tracks, the Bering Sea’s ice melts completely every summer. So now, on May 1st, it looks like the spring may be on the way. "The end is in sight, I think," says Cokelet. "The only way it could turn around is if it gets much colder...I think that’s unlikely."