The dynamic systems causing sheets of ice in West Antarctica to melt are less mysterious, thanks to a team of glider robots. Using data collected by the bots, the team was able to deduce that swirling ocean eddies help transport warm waters to the Antarctic coast. Knowing how the warm water travels will help researchers be able to better determine how fast the ice is melting and how quickly the ocean will rise.
The six-foot gliders were important to the project, because they allowed the Caltech research team to collect data from the Southern Ocean in especially treacherous weather. It also saved the team considerable money on oil that would have been needed to power a ship to each area. Normally, the researchers go out in big ships and then lower the equipment into the ocean, or they collect data from above using satellites.
“Observationally, it’s a very hard place to get to with ships. Also, the warm water is not at the surface, making satellite observations ineffective,” lead author Andrew Thompson, assistant professor of environmental science and engineering.
The ocean gliders are small — about six feet long — and, like airborne gliders, they have no propeller. Batteries drive a pump that pushes water from inside to outside the hull. This allowed the robot to sink to the bottom of the ocean to collect data on water temperature and salinity, and float to the top so that it can contact the researchers via mobile phone. The gliders were able to get a good, long-term view of the impact of the storms swirling deep in the ocean because they could stay in the ocean for months, collecting and transmitting data.
“Ocean currents are variable, and so if you go just one time, what you measure might not be what the current looks like a day later. It’s sort of like the weather—you know it’s going to be warm in the summer and cold in the winter, but on a day-to-day basis it could be cold in the summer just because a storm came in,” Thompson says. “Eddies do the same thing in the ocean, so unless you understand how the temperature of currents is changing from day to day—information we can actually collect with the gliders—then you can’t understand what the long-term heat transport is.”
For more information on the project, see the study published in the Nov. 10th issue of Nature Geoscience.