Diagnosing vertical mixing in a two-layer exchange flow

Most classification schemes and analyses of estuarine and exchange flows us e only salinity as a tracer. Temperatures are generally ignored. However, a proper understanding of the effects of surface heating can explain observe d seaward changes in the slope of temperature-salinity correlations. A theo ry is proposed relating changes in temperature and salinity with transport and mixing parameters in a two-layer exchange flow. Results show that along -channel changes in the slope of T-S correlations are virtually independent of vertical mixing but are directly related to horizontal layer transport. Changes in the layer salinities can be related to various ratios of horizo ntal and vertical transports. Combining these two features of the theory pe rmits a diagnostic determination of Lagrangian transport and mixing from st andard hydrographic observations of layer temperature and salinity and an e stimate of the surface heat input. The theory is applied to observations ma de through the spring/neap tidal cycle of mixing in Hare Strait, British Co lumbia.