The Inverted Echo Sounder

The Inverted Echo Sounder (IES) is an ocean bottom moored instrument which very accurately measures the time required for an acoustic pulse to travel from the bottom to the ocean surface and back. The round-trip acoustic travel time varies in response to changes in the mean temperature structure in the water column above the instrument, which in turn may be used as a sensitive indicator of the shifting paths of ocean currents in many locations. The instrument is housed in a 17" diameter glass sphere and carries all the necessary control, transmit and receive electronics, a digital cassette recorder and an acoustic release receiver. It can operate in water depths to 6700 m for periods of up to one year and requires no additional mooring equipment other than an anchor. Records from four IES\´s deployed under the Gulf Stream northeast of Cape Hatteras are shown along with steps in the processing of the data.