Diapycnal flow through the Georges Bank tidal front: A dye tracer study

Abstract

A fluorescent dye tracer, Fluorescein, injected into the bottom mixed layer at the seaward edge of the tidal front on Georges Bank has provided the first quantitative measurement of an on-bank diapycnal Lagrangian flow through the front. From the warming of the dye patch, 2.5x10 -6°C/s and 7.8x10 -6 °C/s on the south flank and northeast peak respectively, as it passed through the frontal temperature gradient we infer an on-bank flow of 1.9 cm/s on the south flank and 3.2 cm/s on the northeast peak. The heat flux required for this warming is predominantly due to vertical mixing within the tidal front. These observations further demonstrate the utility of direct Lagrangian measurements and provide quantitative estimates of the cross-frontal exchange on Georges Bank, the focus of the U.S GLOBEC Northwest Atlantic/Georges Bank Phase III program.