Drone Glider Finds Swirling Undersea Storms That Help Melt Ice Sheets

Using the undersea gliders above, scientists have uncovered swirling submarine storms that move hot and cold water around near Antarctic ice sheets.

Setting the six-foot-long properless vehicles loose in the Weddell Sea west of Antarctica, an international team of researchers hoped to collect data about how much these submarine eddies impact polar ice melt.

The gliders move down through the water column by pumping water in; they rise back toward the surface by pumping water out. Using this simple principle, they dive up to 3,280 feet below the ocean’s surface to collect temperature, salinity, pressure and oxygen readings at different depths. When the vehicle surfaces periodically through its two-month cruise, it transmits the data it has collected back to the mother ship.

Using this information, the scientists learned that giant invisible eddies spinning off of currents swirl the ocean’s water around, transporting warmer water at lower depths toward the ice.

“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,” said Andrew Thompson, an assistant professor of environmental science and engineering at the California Institute of Technology. “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.”

Thompson said warmer water is not always at the surface in the ocean–higher salinity levels make some water denser. This can mean that warmer water is actually below colder water. The data from the gliders let the team see how these warmer subsurface waters could be transported toward the ice shelf, leading it to melt from below and break off, or calve, big pieces.

“The penetration of the warmer mid-depth waters past the shelf break has been implicated in the pronounced loss of ice shelf mass over much of west Antarctica,” Thompson and his coauthors write in a paper published Nov. 10 in the journal Nature Geoscience. “Here we show, using hydrographic data collected from ocean gliders, that eddy-induced transport is a primary contributor to mass and property fluxes across the slope.”

Read more about their work here.

Image and schematic: Courtesy of CalTech.

Top Gif: Created from Vimeo video courtesy of GEOMAR Helmholtz Centre for Ocean Research Kiel, Germany.