Modeling the oceanic mixed-layer and effects of deep convection

• Main Author: Käse, Rolf H.
• Other Authors: Plate, E. J.
• Format: Book Part
• Language: English
• Published: Kluwer 1998
• Subjects: Pacific; north atlantic current; North Atlantic
• Online Access: https://oceanrep.geomar.de/id/eprint/3217/; https://oceanrep.geomar.de/id/eprint/3217/1/K%C3%A4se.pdf; https://doi.org/10.1007/978-94-011-5058-3_7

Progress in modeling the oceanic circulation has been achieved in the last few years by increasing the speed of computers and by refining modeling techniques. The dynamics of major current systems such as the Gulfstream-North Atlantic Current and their corresponding eddy variability is reasonably well understood [58, 32]. Climate models predict global warming as a result of increasing CO2 in the atmosphere and forecast El Nino events in the equatorial Pacific [50]. Freshwater imbalances in the deep convection regions of the polar and subpolar regions of the North Atlantic result in alternating multiple equilibrium states of the global thermohaline vertical circulation - the ”conveyor belt” [53]. On the other hand, large scale modeling relies heavily on the parametrization of ”subgrid” processes. This is especially true for the oceanic boundary layer. Here the modeling suffers from inappropriate information on the fluxes at the air-sea interface. Most coupled models with simplified fluxes do not represent the surface temperature well enough and water mass characteristics drift away from the initial state. Restoring conditions at the sea surface are needed to force the model back to the observations. The fluxes analyzed from runs with restoring conditions show substantial errors. It is evident that progress in the reliability of long-term predictions of climate variations can only be made with a better representation of mixed layer dynamics.