Abstract

Solar heating of the upper ocean is a primary energy input to the ocean-atmosphere system, and the vertical heating profile is modified by the concentration of phytoplankton in the water, with consequences for sea surface temperature and upper ocean dynamics. Despite the development of increasingly complex modeling approaches for radiative transfer in the atmosphere and upper ocean, the simple parameterizations of radiant heating used in most ocean models are plagued by errors and inconsistencies. There remains a need for a parameterization that is reliable in the upper meters and contains an explicitly spectral dependence on the concentration of biogenic material, while maintaining the computational simplicity of the parameterizations currently in use. In this work, we assemble simple, observationally-validated physical modeling tools for the key controls on ocean radiant heating, and simplify them into a parameterization that fulfills this need. We then use observations from 64 spectroradiometer depth casts across 6 cruises, 13 surface hyperspectral radiometer deployments, and 2 UAV flights to probe the accuracy and uncertainty associated with the new parameterization. We conclude with a case study using the new parameterization to demonstrate the impact of chlorophyll concentration on the structure of diurnal warm layers, an investigation that was not possible to conduct accurately using previous parameterizations. The parameterization presented in this work equips researchers to better model global patterns of sea surface temperature, diurnal warming, and mixed-layer depths, without a prohibitive increase in complexity.