Numerical study of the diapycnal flow through a tidal front with passive tracers

Abstract

[1] A two-dimensional numerical model is used to study the diapycnal flow through a tidal front with passive tracers. In a basic numerical experiment a passive tracer is released into the bottom water at the offshore edge of a tidal front, and it subsequently moves on-bank with a velocity that decreases with time. This qualitatively agrees with a recent field experiment using a dye tracer on Georges Bank. Additional experiments are performed to investigate the sensitivity of the tracer dispersion to the tidal phase and the location of tracer release within the front. As the release point is moved on-bank across the front, the tracer velocity decreases until it weakly reverses on the on-bank edge of the front. This trend can be understood by considering the structure of the Lagrangian velocity field in the tidal front, the degree of vertical mixing of the tracer, and the concentrationweighted mean patch velocity. The tidal phase at the time of tracer release does not significantly affect the tracer dispersion.

A model‐dye comparison experiment in the tidal mixing front zone on the southern flank of Georges Bank

“…[6] Most previous model studies have been ''processoriented'' due in part to the lack of direct tracer measurements [Loder and Wright, 1985;Chen, 1992;Naimie et al, 1994;Chen et al, 1995Chen et al, , 2003aNaimie, 1996, Franks and Chen, 1996Loder et al, 1997;Chen and Beardsley, 1998;Pringle and Franks, 2001;Dale et al, 2003]. Recently, two studies have been published that compare model simulations with the dye experiment of Houghton [2002] conducted on the southern flank of GB during 22-26 May 1999. Dong et al [2004 applied an idealized 2-D finite difference model to study diapycnal flow of a passive tracer released near the bottom just off-bank of the tidal mixing front on the southern flank of GB.…”

“…Recently, two studies have been published that compare model simulations with the dye experiment of Houghton [2002] conducted on the southern flank of GB during 22–26 May 1999. Dong et al [2004] applied an idealized 2‐D finite difference model to study diapycnal flow of a passive tracer released near the bottom just off‐bank of the tidal mixing front on the southern flank of GB. While this simple model showed a qualitatively consistent on‐bank diapycnal Lagrangian current (similar to that reported in an earlier 2‐D Lagrangian experiment by Chen and Beardsley [1998]) and illustrated the sensitivity of the cross‐frontal motion to the location and timing of the initial tracer injection, the 2‐D model was unable to reproduce the observed trajectory of the dye patch, which is clearly influenced by an energetic 3‐D mesoscale field of frontal structure and circulation.…”

Influences of Deep‐Water Seamounts on the Hydrodynamic Environment in the Northwestern Pacific Ocean

“…Besides air-sea fluxes (momentum, heat, freshwater), tides are another external forcing. Interaction of tidal flow with varying bottom topography can generate residual or rectified currents (e.g., Dong, Houghton, et al, 2004;Guo et al, 2020;Lavelle & Mohn, 2010;Stashchuk et al, 2017;Vlasenko et al, 2018). Sensitivity experiments with and without tides are conducted during 2012 to investigate the effects of tides on the hydrodynamic environment in the present study area.…”