Hypoxia in the Lower St. Lawrence Estuary: How physics controls spatial patterns

A laterally integrated advection‐diffusion two‐dimensional model was implemented to simulate the spatial distribution of dissolved oxygen and the development of hypoxic conditions in the deep waters of the Laurentian Channel (Estuary and Gulf of St. Lawrence, Eastern Canada). Our simulations reveal that the horizontal distribution of dissolved oxygen in the bottom waters of the Laurentian Channel is determined by a combination of physical and biogeochemical processes, whereas its vertical distribution is governed by the deep water circulation. This result strongly suggests that the physics of the system and the source water properties are mostly responsible for the generation of a mid‐water column oxygen minimum and the oxygen distribution pattern in the deep water column. Key Points Reproduce observed geographical distribution of dissolved oxygen concentration System much more sensitive to physical than biogeochemical processes Circulation within the Channel mostly responsible for hypoxia in the LSLE