It’s a fact: Antarctica is melting. According to researchers from Caltech, seawater surrounding the continent is slowly melting the ice. But exactly how did the warmer water come into contact with Antarctica? Using dolphin-like robotic gliders, the researchers have uncovered the answer: storm-like underwater eddies (water flows) are to blame.
The paper, co-authored by Karen Heywood, Andrew Thompson, and others, sheds light on the exact process.
“When you have a melting slab of ice, it can either melt from above because the atmosphere is getting warmer or it can melt from below because the ocean is warm,” explains lead Thompson, the assistant professor of environmental science and engineering at Caltech.
“All of our evidence points to ocean warming as the most important factor affecting these ice shelves, so we wanted to understand the physics of how the heat gets there.”
But here lies the problem: it’s impossible to measure the temperature of water beneath a continent. The traditional approach requires dropping equipment into the sea from a ship. Satellite imaging doesn’t fare too well either, since it can only capture heat on the surface.
The gliders, on the other hand, are ideal for the job. They are small (about five feet long), energy efficient and capable of exploring the area for much longer durations of time. Thus every few hours, upon surfacing from the water, the gliders provide researchers with important data that they can download, and later analyze.
Through this manner, they’ve found that the warmest water is actually sandwiched between the surface and the depths due to differences in salinity levels. Underwater eddies (swirling of fluid) are instrumental for bringing the warm water up towards the ice sheets.
“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.”