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Robotic network to explore Antarctic ice shelves

Posted December 19, 2017

One of the biggest unknowns for the future of Earth’s climate is Antarctica, where the West Antarctic Ice Sheet holds so much ice that if it collapsed could bring several feet of rising seas.

A new partnership between the University of Washington’s College of the Environment, the UW Applied Physics Laboratory and Paul G. Allen Philanthropies will use a robotic network to observe the conditions beneath a floating Antarctic ice shelf.

This sketch shows how self-driving Seagliders and floats will track conditions below an Antarctic ice shelf. Inside these caves, warmer saltwater flows in on the bottom, carrying heat which may eat away at the ice, and fresher glacial meltwater flows out above. Image credit: University of Washington.

Ice shelves act as buttresses that restrain the flow of inland ice into the sea, which under a warmer climate could trigger many feet of global sea level rise, on a timeline that is largely unknown. Observations in the water-filled caves under ice shelves could help explain how warmer seawater interacts with the glacier’s underbelly.

The team members performed a final test Nov. 6 in Puget Sound before the instruments are deployed in the Southern Ocean from a Korean research ship, the R/V Araon, that departs from New Zealand in mid-December.

“A project as experimental as this one would be impossible without the support of Paul G. Allen Philanthropies,” said Craig Lee, a UW professor of oceanography and oceanographer at the UW Applied Physics Laboratory. “This is a high-risk, proof-of-concept test of using robotic technology in a very risky marine environment.”

The ice shelf is the floating portion of a glacier that extends seaward from inland ice, which rests on bedrock. Most of Antarctica does not yet show significant surface melt, but scientists think melt is happening at the glacier’s underbelly, where relatively warm ocean water meets its underside. What is learned with this new data will help scientists better understand the stability of these ice shelves and help make predictions about sea level rise.

“This is one of a series of philanthropic investments by Paul Allen to improve our understanding of how the Earth is changing and how it’s being impacted by climate change,” said Spencer Reeder, director of climate and energy for Paul G. Allen Philanthropies.

UW oceanographers invented the Seaglider in the mid-1990s, with support from the National Science Foundation, and still build research models of the torpedo-shaped ocean drone. UW researchers adapted the Seaglider for operating under ice, and have been using it to sample below Arctic sea ice since 2008. In 2014, Lee used a Seaglider and other technology in the Arctic Ocean to track the breakup of summer sea ice.

This new project will deploy a similar robotic network in the Southern Hemisphere. The environment is more challenging because the instruments must venture into the ocean cavities formed by ice shelves, which are very complex, but largely unknown, environments.

“We have almost no information about the area where the glacier is floating on top of the ocean,” said glaciologist Knut Christianson, a UW assistant professor of Earth and space sciences. “The ice is 300 to 500 meters (1/5 to 1/3 of a mile) thick. There’s no light penetrating, it’s impossible to communicate with any instruments, and this environment is extremely hard on equipment — picture big crevasses, rushing water and jagged ice.”

This effort included figuring out how to develop gliders that can get in and out from the ice sheet’s edge without being crushed by moving ice, swept away by fast-flowing water or trapped in the complex of ridges and crevasses on the ice shelf’s underside.

This year’s test also will use complementary technology designed by James Girton, an oceanographer at the UW Applied Physics Laboratory, which drifts with the currents while moving up and down gathering data.

The team has devised new navigation algorithms for the Seaglider and tested them in simulations to make sure the instrument can navigate and return safely. The plan is for the gliders to initially travel in and out of a cave several times a day in summer, surfacing between each trip to beam data back to shore.

Once the ocean surface freezes for the Southern Hemisphere winter, the robots will continue to take measurements on their own, and will beam data back only when they emerge months later in the spring.

“We’ve never been able to get really deep into an ice cave, where the floating ice shelf meets the seafloor,” Christianson said. “If we can do that, we’ll be able to collect tons of new data. We often don’t even know what the topography of the seafloor is like beneath the shelf, which affects water flow, temperature and other factors that control the melting rate.”

Source: University of Washington

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