On the effects of variability in meteorological forcing on the vertical structure of a stratified watercolumn

Abstract

A one-dimensional mixed layer model which includes both a surface and bottom mixed layer is used to examine the variability in the physical vertical structure of a stratified watercolumn due to realistic meteorological forcing. Results are discussed for a relatively large water depth, representative for stably stratified regions, and a relatively small water depth, representative for regions in the vicinity of tidal mixing fronts. Substantial differences in heat content of both columns for different years appear to be caused by different wind regimes. Comparison of model runs with hourly and averaged (daily, weekly, monthly) meteorological forcing shows that short-period wind mixing events influence not only the variability in the vertical physical structure (e.g. the surface mixed layer depth) but also its longer term mean (e.g. the average heat content of a watercolumn). In regions with a relatively small water depth storm events cause a cross-thermocline exchange of surface and bottom water which may trigger the blooming of algae. Therefore these events may have consequences for the net annual production of phytoplankton.