Tag Archives: glider

Gliding Into the Danger Zone

January 15, 2015 by Hugh Powell; Photos by Chris Linder | 19 Comments

In yesterday’s post, the glider team took a calculated risk and brought glider RU05 into the shallow waters near shore. We made a big deal about how dangerous this was—how the waters near shore are full of obstacles like rocks, islands, icebergs, and squirrelly currents. But we also said that everything went fine and the glider team was already planning more. If it sounded like maybe shallow water wasn’t so dangerous to gliders after all, then today’s post is for you.

Late yesterday evening, glider RU05 dove to the bottom of the sea as usual, but it never came up. When Dr. Josh Kohut woke up this morning, he had a text from the glider pilots in New Jersey: RU05 has not checked in for more than 8 hours. Something was keeping it underwater.

We spent the rest of the day figuring out what had gone wrong. Click through the slideshow to see what happened to the glider and how the team fixed it:

Brash to the HorizonR U OK, RU05?Safeguarding the Rest of the FleetGlider on a StretcherAdvice From AfarPut All the Pieces Back Together AgainReloaded and Ready for a New Mission

 

glider salvation mystery by Dave AragonThis evening, glider pilot Dave Aragon looked at the glider’s data files and made this schematic showing what he thinks happened. The glider was doing its normal job, repeatedly diving to the bottom and rising to the surface, and measuring the water along the way. The zigzag black line shows the glider’s actual path. Aragon thinks the glider did fine but may have flown into a patch of kelp (a type of very large seaweed). The thick kelp stems got tangled in the glider and didn’t let it go until 12 hours later, when it dropped its emergency weight.

This is one of the hard parts of working with gliders. They may be sophisticated machines, but they can’t see in front of them, they have limited battery life and limited maneuverability, and once they go below the surface they can’t contact the glider pilots for help. If it gets caught underwater, there’s a very real chance the scientists will never see it again. Today, we were lucky.

“Off New Jersey the shallows don’t really present a danger to the gliders,” Dr. Kohut said. “Here with all the kelp and the rock it’s much more hazardous. But I’m still happy we sent the glider in close to shore because we got all that very nice data to go along with Kim [Bernard]’s transect.” From now on they will be a little more careful around shallow water, though. “Before this, we knew we needed to avoid islands,” he said. “Now we’ve expanded our definition of an island to include water up to 20 meters deep.”

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A Glider Joins Forces With the Krill Team

January 13, 2015 by Hugh Powell; Photos by Chris Linder | 13 Comments

The gliders have been out on their own for more than a week. In that time they’ve traveled far out to sea, but today the team decided to turn one of them around and bring it almost all the way back home. Being close to shore is actually more dangerous for a glider than being in deep water, but they thought it would be worth the risk to meet up with the krill team’s echosounder and combine the two instruments’ strengths.

Click through the slideshow to learn about the glider’s travels—then check below for a quick look at what the two instruments found together:

The Traveler Returns Converging on a PlanHazard in the Boating ZoneA Glider in Your Rearview MirrorDoubling UpTransponder BluesWhip in the Wind

glider transect data with krill results
This graph helps show how two instruments combine to create a better picture of what’s going on under the water’s surface. To read it, imagine that the glider is flying from left to right on the graph. As it moves slowly along this 1.5-mile track, it dives from the top of the graph to the bottom and measures chlorophyll levels. That gives an estimate of the amount of phytoplankton in the water, and phytoplankton are the main food of krill.

Now imagine the krill team driving their zodiac along the same route. The boat moves along the top of the graph (the surface of the water), and the echosounder detects patches of krill below it. Interestingly, the glider found a fairly high concentration of chlorophyll high in the water on the left side of the graph. The krill team found a patch of krill in deeper water beneath it, but not anywhere else.

“That’s pretty neat to find,” Dr. Kohut said, “that the only place on the whole transect there was krill was underneath the patch of chlorophyll.” The krill may have been resting during the day before swimming up to eat phytoplankton later in the day, Dr. Oliver said, or they may have been feeding on organic material as it drifted downward from the phytoplankton patch.

What’s really interesting about this find is that it couldn’t have happened without putting the two instruments—glider and echosounder—together. If the glider had been on its own, it would have noticed the phytoplankton, but we couldn’t have known whether krill were around to feed on it. On the other hand, if we’d had only the findings from the echosounder we’d have known there were krill around but we wouldn’t know why.

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