Reformation time for the thermal skin layer of the ocean

Abstract

The reformation time of the temperature gradient within the thermal skin layer of the sea surface (top few hundred microns to a few millimeters) after a disruptive event such as wave breaking was calculated. A theoretical model of the heat transfer mechanisms in the skin layer was developed which takes into account molecular conduction, emission of infra‐red (IR) radiation within the water, the evaporation of water, sensible heat flux and net IR emission at the water–atmosphere interface. The time for the skin to develop fully after the cessation of a disruptive event such as wave breaking, was found to be dependant upon the skin thickness. Using equations developed by Fedorov and Ginsberg for the skin thickness, the skin reformation time was calculated for different net heat fluxes, wind speeds and water temperatures. It was found that the reformation time could be as large as 40 s for small values of net heat flux, low wind speed and low water temperature, and on the order of 1 s for higher wind speeds and higher water temperature. In order to determine if the skin would reform fully, it was necessary to determine if the mean time between disruptive events was greater or less than reformation time. It was concluded that the wide range of the coefficient of proportionality λ′ in the equation ΔT = (λ′H tυ)/(kU*) reported in the literature may be partly attributable to measurements being taken when the skin layer was not fully developed.