Robotic dolphins have helped shed light on the mechanism behind Antarctica's declining glaciers, which scientists suspect to be melting from bottom up and is crucial to understanding climate change.

In a new study, which was published in the journal Nature Geoscience on Nov. 10, Andrew Thompson, assistant professor of environmental science and engineering at the California Institute of Technology, and colleagues used yellow robot ocean gliders measuring about six feet long to gauge the salinity, temperature and oxygen levels of the depths of the Weddell Sea in West Antarctica.

Compared with large ships, the gliders, which were remotely controlled, are small and energy-efficient so they can sample the waters for longer periods of time and allow researchers to identify ocean features that could not have been feasible to study using other means.

Thompson said that changes that occur in the Polar Regions tend to amplify posing problems to researchers who want to conduct observations in the area.

"One of the challenges of using ship-based oceanography is that it's difficult to stay out for long periods of time. Life gets in the way, sometimes," Thompson said.

The robots send data through satellite mobile phone technology when they surface every few hour hours, allowing the researchers to immediately access the information that the gliders have gathered. Each of the gliders places a satellite "call" home about five or six times a day.

The measurements reveal that the warm salty water that reaches the Antarctic continental shelf and which contributes to the melting of the coastal ice, is transported by eddies, swirling underwater storms produced by the currents of the ocean.

"Eddies are instabilities that are caused by ocean currents, and we often compare their effect on the ocean to putting a spoon in your coffee," Thompson said. "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."

The eddies seem to spin towards the ice sheet carrying warm water and because they occur beneath the ocean surface, the warmest layer of the ocean is the middle layer which appears to be transporting heat and thawing the ice sheets.

"We show that the eddy transport and the surface wind-driven transport make comparable contributions to the total overturning circulation," the researchers wrote. "Eddy-induced transport is concentrated in the warm, intermediate layers away from frictional boundaries.