A wind-induced mechanism for the cross-frontal transport over the southern flank of Georges Bank in early summer: a 2-D real-time modeling experiment

C. Chen, R. Schlitz, G. Lough, K. Smith, and J.P. Manning

The water exchange across tidal mixing front on the southern flank of Georges Bank was examined using a 2-D primitive equation model. The numerical domain featured a cross- frontal transect of the June 1999 hydrographic/ADCP survey cruise. The model was initialized with temperature and salinity fields measured at the first hydrographic survey on the 11th of June and run prognostically with tidal forcing and real-time winds plus heat flux. The model results show that the significant cross-frontal, onbank water transport could occur in the upper 20 m as the upper part of the tidal mixing front migrated onbank under real-time wind fluctuation (Figure 1). The onbank flux tended to enhance as the heat flux was added. The fact that no or less cross-frontal water transport was found in the cases with either tide forcing only or tide plus averaged wind suggested that the temporal wind variation played a critical role in the cross-frontal, onbank water transport on the southern flank in early summer, when stratification just developed. The wind-induced cross-frontal, onbank water transport occurred episodically with wind fluctuation associated with atmospheric frontal passages and also was much more significant than the tide-induced cross-frontal water flux near the bottom. This process could be one of the physical mechanisms responsible for the cross-frontal, onbank flux of the copepod observed on the southern flank in early summer.

Figure 1

Southern Flank Moored Water Property Summary.