Submarine groundwater discharge as a source of nutrients to the North Pacific and Arctic coastal ocean

Abstract

Primary productivity in both the Arctic Ocean and the Gulf of Alaska (GOA) is nitrogen limited in the summer when light limitation is relieved, and stratification in the GOA inhibits nutrient fluxes from deep water sources. Concentrations of nutrients and trace metals in these regions are higher closer to shore, and thus rivers have been attributed as the primary coastal source of nutrients and trace metals. Here we evaluate the role of Submarine Groundwater Discharge (SGD), a previously unquantified source of nutrients and trace metals to the coastal Arctic Ocean and GOA. SGD is an especially enriched in nitrate relative to other nutrients, contributing 1.2 ± 0.4 mol NO3 day− 1 m− 1 of shoreline of the Arctic Ocean. In the GOA, both SGD-associated nitrate flux (4.3 ± 2.1 NO3 day− 1 m− 1 of shoreline) and silicate flux (13 ± 6 SiO4 day− 1 m− 1 of shoreline), are substantial when compared to other external nutrient sources. Conservative extrapolations indicate overall SGD supplies more nitrate (1.5–17.5 times) to the GOA than rivers.