According to a recent study published in Geophysical Research Letters, satellites have revealed that Antarctica’s ice is melting at a rate of 159 gigatonnes per year. It has long been known that these melting ice sheets are major factors in the global sea level rise, yet it wasn’t until a few months ago that anyone could deduce the source of the problem.
Researchers from California Institute of Technology dispatched a fleet of three robotic, battery-powered ocean gliders to measure new data of the Antarctic ice. These gliders, dubbed ‘dolphins’ due to their similar size and appearance, measured several qualities of water underneath the ice shelves. The purpose of this robotic expedition was to determine the cause of the massive Antarctic ice shelf melting.
To measure the temperature of an object on Earth, scientists traditionally look to satellites. As leader of the study Andrew Thompson noted,
“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. 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”.
As the Antarctic is difficult to maneuver through, the research group also couldn’t collect data from ships. They resorted to the revolutionary robotic dolphins, which, over the span of two months, measured the temperature, salinity (the amount of dissolved salt in water, which controls the water’s density), and ocean currents.
Nature recently published the gliders’ measurements along with some scientific analysis. The researchers determined that eddy currents are the root cause of warm water reaching Antarctica. Thompson defined eddy currents as
“instabilities that are caused by ocean currents, and we often compare their effect on the ocean to putting a spoon in your coffee. If you pour milk in your coffee and then you stir it with a spoon, the spoon enhances your ability to mix the milk into the coffee and that is what these eddies do. They are very good at mixing heat and other properties”.
This research is a step in the right direction in obtaining a full explanation of the global sea rise. In the future, Thompson plans on comparing meteorological data with his glider findings to better understand the interactions between the atmosphere and oceans.