Ocean-Displacement Measurements from Motion-Contaminated Towed Temperature Arrays

Abstract

In attempting to understand the small-scale physical processes that occur within a particular area of the ocean, oceanographers typically examine the local internal wave activity there. The local internal wave activity, in particular internal wave displacement, is usually inferred from scalar quantities, such as temperature or conductivity, that are measured using sensors which are either towed or lowered from research vessels. A problem exists with data collected in this manner in that the data are usually contaminated by the surface-wave induced motions of the research vessel which are transmitted down the tow cable. A technique has been developed which not only estimates the internal wave displacement field in the ocean but also is very effective in reducing the resulting motion contamination in these estimates. This technique also reduces the finestructure contamination which is present in the data when sensors are moved through a layered medium. Two sections of motion-contaminated data from a towed thermistor array were processed using this technique. Under conditions with large sensor motion (47 cm rms), 90% of the effects of sensor motion were removed from the data, while under less severe conditions (7 cm rms), all observable effects of sensor motion were removed.