An intelligent, ocean-going glider has spent six months on a record-breaking deployment to sample the icy waters off western Greenland. The samples will contribute to the longest continuous measurement of Arctic currents that help to drive ocean circulation and regulate global seawater temperatures.
The 49-kilogram (110-pound) seaglider, developed and deployed by researchers at the University of Washington, measured fresh water leaving the Arctic Ocean through the Canadian Arctic Archipelago and Davis Strait and entering the Labrador Sea.
Scientists are concerned that Arctic climate change and increased fresh-water runoff are affecting the formation of very dense water in the Labrador Sea. That dense, cold water is a critical component driving the circulation of the world's oceans, according to Craig Lee, a principal oceanographer with the University of Washington's Applied Physics Laboratory (APL).
Lee and senior oceanographer Jason Gobat lead the group developing the under-the-ice seaglider with support from the National Science Foundation (NSF).
The seaglider is one of more than 35 projects that are part of NSF's Arctic Observing Network (AON), which is meant to track and understand Arctic environmental change using an integrated suite of tools ranging from ocean buoys to satellites. Under-ice gliders might one day be among a suite of devices under the ice-covered high Arctic.
AON was one of NSF's primary research thrusts for the International Polar Year (IPY), which ended in late March. IPY was a 24-month deployment by scientists from 60 countries around the world to better understand the physical characteristics of the Polar Regions, their role as regulators of global climate and the nature of the changes occurring their as global temperatures rise. In the Arctic, scientists and Native communities also worked together not only to understand the changes themselves, but also the effects of change on subsistence lifestyles.
NSF was the lead U.S. agency for IPY.
The seaglider project was an international cooperative that included Richard Moritz, Kate Stafford and Beth Curry of APL; Brian Petrie, of the Bedford Institute of Oceanography in Canada; and Kunuk Lennert and other scientists with the Greenland Institute of Natural Resources.
Seagliders developed by the university's School of Oceanography and APL are small, reusable underwater vehicles meant to operate on their own, gliding without propellers from the surface to as deep as 1,000 meters (3,300 feet), while collecting information about temperature, salinity and level of dissolved oxygen. When seagliders are at the ocean surface they can be commanded remotely from nearly anywhere in the world via the Internet and can transmit their data via satellite telephone.
The recent glider deployment allowed the university to surpass its two-year-old world record for operating a glider under the ice, this time by successfully operating a glider as it made round trips hundreds of miles in length under the ice of the Davis Strait.
The University of Washington group is the first and only one in the world sending gliders under the ice. With NSF support, the university has developed a glider with enough artificial intelligence to be able to:
- Consider how long it has been under the ice and how urgent it is to try to reach an opening in the ice to transmit its data,
- Use an internal ice atlas to weigh the odds of having open water above and then check as it rises to determine if the water temperature actually indicates whether ice is overhead. If conditions aren't right and there isn't an urgent need to download data, it just dives back down rather than chance damaging itself on the ragged underside of the ice,
- Sense an impending mechanical, electrical or communications failure and make a run for it--that is, try to get out from under the ice and into open water where it could relay its position and possibly be recovered.
Unlike faster-moving propeller-driven autonomous underwater vehicles (AUVs), which may need to be retrieved by ships only days after being deployed, the seagliders can operate on their own for months at a time.
The ability to do so under ice, developed by Lee's group, is important in a place such as Davis Strait where scientists want to measure how much fresh water flows through the strait and at what times of year so they have a baseline for comparison in coming years.