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ODU's Dinniman Tests Data-Gathering Gliders in Antarctic Waters

Dinniman (left) preparing a glider for its mission

Michael Dinniman, an Old Dominion University oceanographer, breathed a sigh of relief when he got word in Norfolk late in January that a research vessel near the Antarctic coast had recovered SG503. After all, Dinniman had built up something close to affection for the plucky SG503, called Ice Dragon, and its identical twin, SG502, called Minke, while he was in Antarctica for most of the month of November.

These two engineering marvels are five-foot-long, tubular gliders that resemble torpedoes. Needing only a tiny bit of battery power, they move slowly but surely - diving and resurfacing - through open waters collecting data such as temperature, salinity, levels of dissolved oxygen and chlorophyll concentrations. They were developed at the University of Washington and are now sold commercially by iRobot Inc.

Similar gliders have been employed by ODU oceanographers to collect data at various depth levels of the Atlantic Ocean off the East Coast. The gliders, which cost about $150,000 apiece, are very inexpensive to operate. The costs for researchers to do such a thorough job of data gathering from a ship would be prohibitively high.

A team of oceanographers including faculty from ODU and the Virginia Institute of Marine Science (VIMS) believed that the gliders would be particularly useful in the Antarctic's Ross Sea, where data-gathering expeditions by ships are limited because the vessels must have reinforced hulls or other protection against the ice.

The National Science Foundation agreed to fund the project - "Seasonal Evolution of Chemical and Biological Variability in the Ross Sea" - and the glider tests began last fall.

Each ODU member of the project team is an affiliate of the Center for Coastal Physical Oceanography (CCPO). Dinniman, who is a research scientist, was the ODU team member tapped to take part in the field work near the U.S. McMurdo Research Station in Anarctica. Other investigators on the grant include Eileen Hofmann and John Klinck, both professors of ocean, earth and atmospheric sciences at ODU, Walker Smith, the team leader, who is a researcher with VIMS. Klinck is also the CCPO director.

The field work in Antarctica also included team members who are from VIMS, the University of Southern Mississippi, University of East Anglia in the United Kingdom, and the University of Washington. The command center for the gliders is at the University of Washington.

Research in the past has suggested that short-term changes in currents and sunlight play a major role in determining the size and duration of the algae blooms that are at the base of the Antarctic food chain. Algae sustain krill and other tiny sea creatures, which, in turn, sustain larger fish, seabirds and marine mammals. The goal of this latest project is to compile enough data over a large enough area to enable the researchers to build computer models of the relationship between physical conditions and biological activity in the Ross Sea.

Although November is almost summertime in Antarctica, Dinniman still encountered zero-degree temperatures, and the researchers were eager to find out if the gliders could withstand cold temperatures and collisions with ice floes.

"Both gliders ended up working fantastically," Dinniman said. "One lost one of its several sensors early on and the other had some problems diving near the end, but both sent back data the entire time and - really important because of their cost - we were able to recover both of them."

Dinniman had to return to Norfolk at the end of November and was not present when Minke (named after a type of whale) and Ice Dragon were recovered in January. "Even though this project was the farthest south any of these gliders had ever been used, in the end they completed 701 (for Minke) and 923 (for Ice Dragon) dives and traveled a combined total of 1,872 miles."

During his time in Antarctica, Dinniman posted dispatches and answered schoolchildren's questions at his website, "Penguins Is Practically Chickens" (http://www.mike-rossglider.blogspot.com/). The name of the site comes from a Bugs Bunny cartoon in which Bugs meets a penguin.

There are posts about penguins that marched right up to the scientists to see what they were doing, about an encounter with a seal and her pup and about igloo building.

Dinniman also provides drama about the gliders, which are programmed to change their buoyancy in order to sink when they need to dive or float upward when they need to surface. Wings turn some of the up and down movement into forward progress - very slow, at only a mile or two an hour. The gliders can dive as deep as about 3,200 feet, collecting data as they go. Periodically, they must surface in order to transmit the data via satellite to a receiving station, calibrate their coordinates and get directions on where to go next.

But the researchers knew a glider's push to get to the surface might cause it occasionally to knock into ice, and even though they did everything they could to keep the devices away from ice, they confronted their worst fears right after the launch of Minke in mid-November.

"We were feeling really good about the launch on the flight back to the base," Dinniman said. "The glider is supposed to signal back to the satellite every time it finishes a dive. The first dive should've taken only about 90 minutes, so when we got back and checked our computers we were a little worried that we hadn't heard anything yet. Then we found out that a software option had been set so that if ice was detected, it wouldn't try to surface for about 10 dives.

"I finally got to bed about 3 a.m. a little worried, but not overly concerned. The next day we got up late and still hadn't heard anything. By the time 9 p.m. rolled around and we still hadn't heard anything, we were getting pretty worried. We got up early (the next morning) and still hadn't heard anything. We were starting to believe the glider might be lost. However, at 8 a.m. we finally got a call from the glider. Everything was OK. Apparently it did have some trouble surfacing and it had actually made 22 dives before it could surface."

This article was posted on: February 3, 2011

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