The overall objective of this project is to understand ocean surface wave breaking, both in terms of the spectral input-dissipation balance that controls wave evolution and in terms of the fundamental physics at the air-sea interface. This proposal builds on recent success measuring wave breaking dissipation in the field, using newly developed SWIFT buoys and conventional video techniques. The investigation is guided by those results, in which short waves appear to saturate at high winds and in which the phase-averaged approach obscures the detailed relationship between turbulent kinetic energy dissipation and wave energy dissipation. New measurements will be made in the context of larger efforts at Ocean Weather Station P (OWS-P) and the pending Calwater2 experiment. The specific objectives are to: 1. Continue ongoing wave spectral observations at OWS-P in the North Pacific Ocean. 2. Extend phase-averaged wave breaking dissipation measurements to higher wind speeds (greater than 15 m/s) using long-endurance versions of SWIFT buoys deployed throughout the winter months, and 3. Develop methods for phase-resolved wave breaking dissipation measurements, using a combination of remote sensing (stereo video) and in situ (coherent arrays of SWIFT buoys) techniques.
Wave breaking is a key process in wave evolution and air-sea interaction, yet is remains poorly understood. Wave forecast models, such as Wave Watch 3, use spectral parameterizations of breaking dissipation. These parameterizations are empirical and largely originate from laboratory studies, in which waves break as a result of superposition rather than the modulation instability process of real ocean waves. This study will measure wave breaking dissipation in the field and evaluate these parameterizations and the underlying hypothesis that wave breaking can be represented spectrally. This is directly related to the ongoing debate on the nature and magnitude of the "breaking strength" parameter b, which was successfully determined in laboratory studies but has ranged over four orders of magnitude in field studies.
This effort will continue a unique time series, begun in 2010, of continuous wave spectral measurements at OWS-P. This is the only offshore wave buoy with spectral measurements in the Northwestern Pacific Ocean. This data is available in real-time and is used for maritime safety, wave forecast assimilation/calibration, and basic research. The data complement the upcoming installation of an Ocean Observatories Initiative (OOI) global node at OWS-P, which will not measure surface waves. The project will include the training of a PhD and of an undergraduate student. Outreach will include continued posts (by invitation) to the New York Times "Scientists at Work" blog, annual participation in the Pacific Science Center's "Science EXPO", and continued participation in the Ocean Inquiry Project.
