Heat and freshwater budgets of the Texas‐Louisiana shelf

Abstract

A self‐consistent climatology comprising monthly mean heat budgets and seasonal mean freshwater budgets was constructed for the Texas‐Louisiana shelf. The heat‐budget phase amplitude was dominated by net heat gain and heat storage. The freshwater‐budget phase amplitude was dominated by river discharge and freshwater storage. Flux divergences of heat and freshwater were computed as residuals. Heat flux diverged in June and July but converged the rest of the year. Freshwater flux showed a persistent divergence throughout the year. This new climatology provided a baseline against which to evaluate synoptic fields computed over the period May 1992 to November 1994 using hydrographic data supplemented by meteorological data derived from a novel mixture of measurements and model products. Analysis of the synoptic fields advanced understanding of the freshwater filling and flushing times (the times required, respectively, to accumulate and remove the freshwater content present on the shelf at any instant). Filling times were calculated by performing a reverse time integration of the net amount of fresh water added to the shelf through the effects of precipitation, river discharge and evaporation. Flushing times were calculated apparently for the first time for this region by performing a forward time integration of the amount of fresh water advected off the shelf through divergence. Filling and flushing times were balanced by adjusting the fraction of Mississippi River discharge assumed to flow westward onto the shelf. The results, which are within the estimated uncertainty, provide new insights into the freshwater balance on the Texas‐Louisiana shelf.