Actively Breaking and Maturing Oceanic Whitecap Observations

Whitecap coverage plays a key role when parameterizing air--sea interaction of gases, aerosols, heat and momentum, determination of ocean albedo changes, and estimating dissipation from the ocean wave-field. Understanding whitecap coverage, its variability, and rate of production, will provide valuable information for upper ocean processes. Over the past 40 years, various meteorological and sea state proxies have been used to explain the highly variable nature of whitecap coverage with limited success. Although wind speed is one of the main forcing paramaters, variability in whitecapping has been observed to span orders of magnitude for similar wind conditions.

In this study, high resolution ocean surface images are examined using digital processing to achieve high confidence spatial quantifications of actively breaking and maturing whitecaps (Scanlon and Ward, 2013). Two data sets (North West Atlantic and Pacific Oceans) were sampled and processed to achieve a maximal range of observed environmental and meteorological conditions. A total of 97,156 images were selected, processed, and segregated into 311 10-minute periods. Best fit functions were applied to the average actively breaking and maturing whitecap coverage estimates along with complimentary estimates of wind, sea temperature, thermal atmospheric stability, and satellite derived chlorophyll concentration.

Our results indicate that, after wind, chlorophyll concentration is the most influential parameter for maturing coverage, and thermal atmospheric stability is the most infuential parameter for actively breaking coverage.