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Today's Weather
Mostly sunny
Lat: 28° 38' N
Long: 88° 10' W
Air temp: 67.1°F (19.5°C)
Water temp: 74.5F (23.4C)
Barometric pressure: 1016 mbar
Seas: 2-3 feet
Wind: S, 23 mph

what's to eat?

When Wind and Waves Rise, So Does Alvin

December 11, 2010 (posted December 12, 2010)
by Ken Kostel

There’s a saying: If you don’t want to lose anything, don’t put it in the ocean. That’s because the ocean can be a very unforgiving place, especially when the wind kicks up and the waves start to build.

When we retrieved Sentry this morning after its overnight surveying mission, the Gulf was calm and inviting. When we launched Alvin a few hours later, a light breeze was just beginning to ruffle the surface. By lunchtime, the wind was blowing 20 miles per hour and gusting higher. The safe limit for launching and retrieving Alvin is around 25 mph.

It’s never an easy decision to cut short an Alvin dive. Time on the seafloor is expensive and hard to come by. But the ship’s captain also has to think about the safety of the crew who are sent out to retrieve Alvin and who have to stand on a pitching deck near 35,000 pounds of submarine hanging on a line. So with the forecast showing bad weather through Sunday, he re-called the sub and by 3 p.m., it was back on deck.

Thanks to careful planning made possible by detailed photographs from Sentry, Chris German and Andrea Quattrini and pilot Sean Kelley were able to accomplish many of their objectives, including setting up one long-term monitoring site on the seafloor. Chief scientist Chuck Fisher would have liked it if they had been able to set up two or three more monitoring sites and explore an area east of where they did most of their work today.

“That’s always the way it is,” said Chuck. “You always wish you could have done more.”

There are 20 or 30 locations on the seafloor around the Gulf that allow scientists to keep careful watch over many different types of ecological communities, but none are in the area around the Deepwater Horizon well and at the same depth as the well. To set one up requires that the site be documented photographically with painstaking detail to have a starting point, or baseline, from which scientists can see and measure any change. An underwater vehicle will return to the site at regular intervals for years to look for any changes.

The site that Chris and Andrea ended up picking was one that appeared on images Sentry took two nights ago. Out of nearly 2,500 photographs, four showed a hard outcrop made of carbonates, a mineral that some seafloor bacteria produce. It appeared to be easily accessible from many sides with Alvin. It also contained at least three different coral species and several individuals of each species (see today’s slideshow).

Sure enough, when they arrived in Alvin they found a perfect site for a long-term monitoring station, took high-resolution images, and left a marker for future visits. What really made the find spectacular, though, was the ease with which they found it and navigated to specific corals and vantage points, using the images from Sentry.

“It took us an hour and a half to get down there and about 15 minutes to drive to the site,” said Chris. “Within about an hour, we had documented the entire site and were moving on.”

That’s not bad, especially since the location was completely unknown just 48 hours ago.

With each dive, the number and diversity of samples in Alvin’s basket has increased. Today, even with their time cut short, Chris and Andrea brought back a selection of corals, tubeworms, sediment cores, and water samples, again thanks to the preview that Sentry gave them. The only thing they missed from their dive plan was a mussel bed. That location was too far to get to with their shortened schedule.

As soon as Alvin is secure in its hangar, the biologists get the first shot at the basket to take their rapidly degrading specimens back to the labs. It’s sometimes a mix of polite choreography and mass chaos as they cross paths with the other scientists who are waiting to retrieve their samples—water, sediment, and rocks—and with the Alvin engineers who are demobilizing the sub from one mission and preparing it for the next.

It looks like the forecasts were right. The waves have been building all afternoon and evening. The Sentry group thought about putting the vehicle in the water for a few hours, but launching it would have been risky. They also considered sending it out tonight and picking it up Sunday evening, but there is no guarantee that things will be any better then.

As it is, we will probably not be diving at all tomorrow.That doesn’t mean we can all take the day off. There is still a lot of work to be done. In one way, the loss of a dive lets everyone catch up a little—though it will be difficult on a pitching, rolling ship. Looking through a microscope can be a harrowing experience when the microscope is moving.

We will probably wait tomorrow in a place from which we can send out Sentry quickly, should the weather clear. Monday is our last chance to dive with Alvin. It would be the sub’s last dive before it goes in for a yearlong upgrade. We also hope to retrieve a second sediment trap before heading home on Tuesday.


Read the new Hot Topic

sediment trap

Light Snacks and Food Chemistry: Photosynthesis and Chemosynthesis

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