The California Institute of Technology (Caltech), University of East Anglia and GEOMAR Helmholtz Centre for Ocean Research have been using robotic dolphins to study exactly how warm water is arriving in Antarctica and ultimately melting the polar ice caps for the last two years.
“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, assistant professor of environmental science and engineering (Caltech), who was the lead author of the study.
“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.”
Robotic Dolphins find out where is the warm water coming from?
However, deep currents of warm water make satellite information unsuited to this work given the depth and the Southern Ocean off the coast of the Antarctic Peninsula is difficult to reach by ship in order to lower instrumentation deep enough to study these currents.
“If it was only temperature that determined density, you’d always have warm water at the top and cold water at the bottom. But in the ocean you also have to factor in salinity; the higher the salinity is in the water, the more dense that water is and the more likely it is to sink to the bottom,” said Thompson.
As a result, the team has been using robotic “dolphins” to get these needed readings. The scientists contacted iRobot, the firm responsible for creating the Caltech Seaglider which resembles a torpedo more than a dolphin in order to study the warm water that is in the middle of the water column owing to salinity.
The $240,000 Seaglider has no propeller but uses batteries to pump water in and out of a compartment in the robot to affect buoyancy. Every few hours, the Seaglider contacted the scientists via a device similar to a mobile phone to share the collected data as they comfortably waited on land (if Antarctica can ever be called comfortable).
Robotic Dolphins: Blame the ocean eddies (and study them)
Through the study which was recently published in the journal Nature Geoscience, Thompson and his team blamed ocean eddies for the melting.
They are a natural occurring phenomenon that act like an ocean blender.
“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,” said Thomson.
“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.”