Effects of Solar Penetration on the Prediction of Upper Ocean Circulation in the Northwest Atlantic

Vertical distribution of solar radiation has an important impact on upper ocean hydrodynamics and thermal dynamics. However, conventional approaches in marine environment modeling and prediction science ignore the complexity in the ocean water optical properties, and account for vertical transmittance of solar radiation only by a sum of multiple exponentials functions, each with empirically defined depth-independent attenuation coefficients. Such a simplification has been shown to lead to significant biases in ocean thermal energy budget, upper ocean circulation, and air-sea heat flux exchange. Here we coupled a generalized optical model with a three-dimensional realistic ocean prediction system for the Northwest Atlantic ocean. The generalized optical model considers the solar radiation in both visible (wavelength < 700 mn) and infrared (wavelength > 700 nm) bands as well as the three-dimensional variations of attenuation coefficients, which are modeled as a function of satellite observed water absorption and backscattering characteristics. A suite of model sensitivity experiments using conventional solar penetration schemes and this generalized optical model were performed both in the one-dimensional and three-dimensional configurations. The resulting ocean circulation, thermal stratifications, upper ocean heat content, and air-sea heat flux exchanges from each case were compared among each other, along with in situ observations. The results highlight the important value of utilizing the generalized three-dimensional optical model to better resolve the subsurface distribution of shortwave solar radiation, which directly impacts synoptic and seasonal forecast of coastal oceanographic and meteorological conditions.