An Ocean Basin Scale Model of plankton dynamics in the North Atlantic: 1. Solutions For the climatological oceanographic conditions in May

Mathematical equations describing marine plankton dynamics are solved for the climatological oceanographic conditions during the month of May in the North Atlantic. Geographical distributions of phytoplankton, zooplankton and limiting nutrient (nitrate) concentration in the surface mixed layer of the ocean are predicted from historical mixed layer depth and the total nutrient made locally available to the plankton ecosystem by convective mixing. The effects of major ocean currents are parameterized in the model through the geographic distribution of nitrate and its vertical gradient. Major upwelling and downwelling circulations control the proximity of high nutrient concentrations to the surface. Model solution of the phytoplankton field with 1° longitude and latitude grid resolution is compared to a recently produced composite of Coastal Zone Color Scanner images of surface chlorophyll in the North Atlantic during May 1979 [W.E. Esaias et al., 1986]. Large‐scale chlorophyll patterns seen in the CZCS composite can be explained as transition zones in the supply of plant nutrients to the surface layer by vertical mixing or localities of light limitation of phytoplankton growth by a deep mixed layer.