Circulation and stratification of the early Turonian Western Interior Seaway: Sensitivity to a variety of forcings

Five forcing fields potentially controlled the circulation of the early Turonian Western Interior Seaway: the wind field, latitudinal temperature gradient, precipitation minus evaporation, runoff, and mixing of Boreal and Tethyan waters. A suite of numerical experiments designed to evaluate the influence of each forcing type was conducted using CIRC, a three-dimensional, turbulent flow, coastal-ocean model, subject to various atmospheric forcings hindcast for the Turonian by GENESIS, an atmospheric general circulation model coupled to surface models of soil, snow, sea-ice, and a slab ocean. Results show that the extreme aspect ratio of the seaway creates a simple circulation pattern regardless of forcing type. A large vertically mixed, cyclonic gyre occupies the middle two-thirds of the seaway, the strength of which is largest when forced by runoff. Despite initial conditions of salinity and/or temperature that are vertically stratified and stable, turbulent mixing within the seaway destroys that stratification within a few model days. Thus, the contrasting water masses, mean annual temperatures, winds, and hydrology hindcast from GENESIS are insufficient to maintain a stable water column, and by inference, bottom-water anoxia.