Estimating Reactive Oxygen Species in the Surface Ocean from Remote Sensing Data with Possible Implications for Fe Deposited from Atmospheric Dust

Reactive oxygen species (ROS), including superoxide (O2-) and hydrogen peroxide (HOOH), are implicated in a variety of important processes in both atmospheric and marine waters including redox cycling of metals, physiological impacts on aquatic micro-organisms, and degradation of natural organic matter (NOM). Photochemical production is the dominant source for O2- and HOOH in marine surface waters, thus creating a mechanistic link with UV radiation and chemical redox reactions. To examine these links over larger spatio-temporal scales (10yr regional and global), we have used the methods of Fichot and Miller (Remote Sensing Environment, 2010) to calculate HOOH photoproduction rates using modeled solar irradiance, remotely sensed ocean color and sea surface temperature, together with laboratory derived photochemical HOOH apparent quantum yield (AQY) spectra with embedded activation energies for temperature correction. Warming of the surface ocean results in higher HOOH photoproduction rates. Making assumptions for the effect of temperature on observed HOOH dark decay constants from coastal and ocean whole water samples, photoproduction rates are used to estimate in situ HOOH and O2- concentrations. These, in turn, provide insight into spatial and temporal trends for Fe redox kinetics relevant to the lifetime and thus, impact of atmospheric Fe deposited to the surface ocean.