Even at 2,200 meters below the surface there is a tidal flow, and this is Di Iorio’s first target. “This flow is small,” she said, “and probably moves only 5 to 10 centimeters a second (coastal tides can move as much as 100 centimeters per second), but it’s there and interacting with hydrothermal plumes.”

Just like smoke from a factory smokestack shifts in wind currents, these plumes appear to sway back and forth (by as much as 5 to 10 meters) with the tidal flow, which creates slight periodic temperature changes in the vent area as water mixes into the flow. Di Iorio uses sound to illustrate these changes.

“Depending on water turbulence and temperature, a sound pulse will take a certain length of time to travel from the transmitter to the receiver. The sound waves will scatter forward, and these changes will be picked up by the receiver,” she said. By measuring amplitude and arrival-time fluctuations, acoustical scintillation enables scientists to create a “picture” of flow, turbulence and temperature character-istics of the water. “Sound can also be used to image a hydrothermal plume the same way that it can be used to image the sea floor or objects on the floor – by studying a reflected, scattered signal.”

By imaging a plume, scientists can determine the point at which the plumes have mixed with so much ocean water that they quit rising.

She noted that the scattering of sound can also allow scientists to measure variables such as plankton layers, fish abundance, size and the boundaries of layers of water at different levels of the ocean. Di Iorio has used acoustics to investigate the number of fish in Savannah’s Grays Reef National Marine Sanctuary and a variety of environments with active tides and currents. “Sound can tell you all sorts of things about the ocean environment,” she said.

This work is funded by a National Science Foundation CAREER grant.

For more information, contact Daniela Di Iorio at daniela@uga.edu.