Pattern and Dynamics of the Meridional Overturning Circulation in the Upper Ocean

摘要

The physics of the Meridional Overturning Circulation (MOC) and interhemispheric heat transport is explored with an emphasis on the upper and central ocean. Sea surface temperature and wind stress are considered in the context of their ability to influence the MOC pattern and their relative significance is quantified. Most calculations in this study use an idealized rectangular basin which makes it easier to identify the key dynamic processes and explain interaction. Volumetric and advective heat transport stream functions are used to analyze interhemispheric exchanges of mass and energy. Data concerning the effects of equatorially-asymmetric wind stress and surface heat flux forcing are used to construct expressions which explicitly define the relationships between wind stress, surface heat flux, interhemispheric volume flow, and heat transport. The relative importance of wind stress and surface heat flux to the overall values of transport is discussed in light of climatology. The meridional overturning circulation in the upper ocean is found to be the dominant factor in interhemispheric heat transport and in the maintenance of the Earth's climate despite its extremely small contribution to total meridional-vertical circulations in the entire ocean basin. This study suggests that the previous emphasis on deep overturning in the abyssal region and small-scale mixing as the dominant factors in the meridional overturning circulation should be reconsidered and the role of wind stress and surface heat fluxes more thoroughly investigated as determining factors of MOC strength and maintenance. This study explores possible mechanisms responsible for climate shift which could result in long-term changes to weather patterns and ocean conditions altering important factors in the Navy's operating environment. Thus, long-term Navy planning must include an appreciation for possible changes in the forcing mechanisms responsible for the meridional overturning circulation.