Dynamics controlling seasonal variability of the dissolved oxygen in the Bohai Sea: A numerical study

A coupled physical-biogeochemical model is used with numerical experiments to investigate the dynamics controlling the spatiotemporal variability of dissolved oxygen (DO) distribution in the Bohai Sea. The model reproduces distinct seasonal variability of DO concentration in the Bohai Sea as characterized by low in summer with large vertical gradient and high in winter with enhanced ventilation. The evolution of bottom DO-depleted zones at northern and southern depressions is primarily controlled by water stratification and topography but also modulated by lateral transport. High bottom turbulence kinetic energy and weak stratification above the Central Bank of the Bohai Sea induce relatively high DO concentration. A comparison between the model and no-resuspension experiment suggests a slight (<5 %) impact of resuspension on DO concentration variation in the Bohai Sea. The input of terrestrial materials from the Yellow River may provide additional nutrients and phytoplankton, sustaining a relatively weak but stable oxygen production along the transport pathway.