Coastal near-inertial wave bursts detected by OSCR

Abstract

Surface current observations from High Frequency (HF) radar have revealed that not only are the low-frequency and tidal currents well resolved by the measurement, higher frequency motions are also contained within the records such as near-inertial oscillations. These motions are associated with oscillations in the internal wave continuum and usually dominate the internal wave energy. A complicating feature in the coastal regime is oceanic frontal structure that influences inertial motions through the relative vorticity fields. These background vorticities may be considerably larger than in the deep ocean case due to the larger density contrast between the fresher, cooler coastal water and the more saline, warmer water masses associated with the subtropical gyre circulation. Synoptic observations of the horizontal flow structure from HF radar provides the spatial context to assess the role of coastal fronts on the near-inertial motions. Observations from an Ocean Surface Current Radar (OSCR) during the Office of Naval Research (ONR)/Naval Research Laboratory (NRL) High Resolution Remote Sensing Experiment, the ONR-sponsored Duck-94 experiment, and U.S. Coast Guard (USCG)-sponsored Ocean Pollution Research Center (OPRC) experiments and NOAA Southeast Caribbean Recruitment Studies (SEFCAR) in the Florida Keys have revealed the presence of internal waves in surface current expressions. The data from the Florida Keys are used to demonstrate that the near-inertial motions were detected in surface current records acquired from an OSCR.