Galleries / The Robo-Sub That Helps Predict Where the Ocean's Headed

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Alana Range; published March 3, 2008

Predicting the Future

Safe Travels

Galloping Glacier

How's the Weather Up There?

In Touch with the Mothership

Done with the Drink

<p>Global sea levels have risen by four to 10 inches over the past 100 years. What will they do over the next 100 years, or even the next 20? This kind of question is critical for planning future coastal development, and it's something David Holland, an oceanographer at New York University, takes very seriously. </p><p>Last year, Holland teamed up with the National Research Council of Canada to deploy a five-foot-long autonomous submarine beneath an iceberg off the coast of Greenland. Called the Slocum underwater glider, the sub's mission was to bring back critical data on how much sea ice is melting due to the rise in ocean temperatures and, ultimately, to help researchers build a digital model to predict sea level rise.</p>

<p>In preparation for shipment to the Greenland expedition site, the glider system--including control computers and additional instruments--is packed snuggly in a bump-proof box. Orange thermal suits that will be worn by the scientists are used as padding around the sub. Before the glider leaves the lab, it's trimmed (balanced horizontally and vertically level) and balanced (made neutrally buoyant) in a freshwater tank. The glider is extremely sensitive to changes in the density of water, and it has to be adjusted to the specific ocean-testing site on the day of the experiment.</p>

<p>Holland's team worked out of Ilulissat, a small town on the mouth of an ice fjord. The third-largest settlement in Greenland, Ilulissat sees 24 hours of daylight during the summer months, a luxury for the scientists who put in longer-than-usual hours. The Ilulissat fjord is home to the Jakobshavn glacier, the most active glacier in the Northern Hemisphere. In 2003, scientists found that the glacier had doubled in speed since 1997.</p><p>"We hypothesized that the Jakobshavn glacier was melting from the bottom, because slight warming of the atmosphere couldn't have caused such an increase" in melting, says Holland. Holland's glider tests in the Ilulissat fjord confirmed that significant melting of icebergs was due to warmer water below.</p>

<p>Before heading out on the ocean to test the glider, Holland's team installed a permanent weather station atop the glacier. It transmits a steady stream of measurements--solar radiation, temperature, wind direction, humidity, snow depth, rainfall, and long wave radiation (energy leaving the earth as infrared radiation)--directly to Holland's computer. The $20,000 weather station is an essential element in getting to the root of glacial melt, helping researchers determine whether it's warming air, warming water, a combination of both, or something else entirely that's melting polar ice.</p><p> </p><p>In January, Holland flew to West Antarctica, where he and a small team erected a similar station in preparation for the next series of glacial melt experiments to begin later this year.</p>

<p>Glider tests were conducted from The Clane, a locally owned, 39-foot-long research boat. It's built entirely from wood but equipped with a sheet-metal cap on its bottom to push ice aside. A control station was installed on the boat, comprising a laptop and radio modem that communicates with a radio beacon on the tail of the ocean glider.</p>

<p>After the mission is complete, an inflatable motorboat retrieves the glider and returns it to the research boat. Holland's Greenland mission has determined that warm water under icebergs and most likely under glaciers is at the root of rising global sea levels (as opposed to warm air). He will next take his methods to Antarctica, whose ice sheets are 10 times the size of Greenland's.</p><p>Read the <a href="http://discovermagazine.com/2008/apr/25-the-robo-sub-that-helps-predict-where-the-ocean.s-headed">article</a> from the April 2008 issue.</p>

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