Mixed Layer Modelling Of Tideless Seas (great Lakes, Temperature).

Uncertainties surrounding the nature of the mixing mechanisms governing upper ocean thermal structure still exist today. Progress in resolving these equations has been largely confined to the open ocean and whether these efforts are applicable to inland seas is yet uncertain. Hence, approximately 200,000 observations of water temperature were assembled from Lakes Erie and Michigan and were used in conjunction with four one-dimensional mixed layer models to evaluate model applicability to tideless seas and to aid in interpretation of lake physics. The four models were: Denman (1973) (KLD), Garwood (1977) (RWG), McCormick and Scavia (1981) (K) and Thompson (1976) (RT). The mixed layer depth, h, is the depth over which surface generated turbulence is of sufficient intensity to penetrate buoyant surface waters and uniformly mix the entire layer. The entrainment rate, dh/dt, is scaled in these models according to either U(,*), the friction velocity, or (DELTA)V, the velocity jump across the mixed layer base, or a combination of both, i.e. RWG. The results showed that any one of the models can be calibrated so as to give reasonable and similar estimates of surface water temperatures (from hourly to monthly time scales) as measured in terms of Root Mean Squared Error (RMSE). In Lake Erie, 1(DEGREES)C RMSEs were typical for upper lake thermal structure while the Michigan RMSEs were somewhat larger. The models showed their greatest differences on shorter time scales. Namely, the K model failed to resolve deepening of h during a late spring storm on Lake Erie while the other models tracked the deepening fairly well. Therefore, when diurnal physical processes are of interest the best model is then the one that is most faithful in reproducing not only observed temperatures, but also the correct mixed layer depths and the proper amount of entrainment energy. In this study two of the models, RT and RWG, which use the (DELTA)V entrainment scaling, not only tracked temperatures and h closely but they too, in general, showed the best agreement in matching the energy levels associated with entrainment as estimated from spectral analyses of model output and data.PhDEarth SciencesPhysical oceanographyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/128025/2/8712172.pd