Report of the

U.S. GLOBEC Georges Bank

Science Meeting

18 - 20 November 2003, Rhode Island

 


Cover Page

Acknowledgements

Introduction

Narrative

Presentation Abstracts

Poster Presentations

Appendix I: Agenda

Appendix II: List of Participants

Appendix III: List of Planned Publications


Sub-Tidal Circulation at the Tidal Mixing Front: Analysis of the Moored Instrument Array.

Lerczak, J.1, R. Schlitz2, S. Lentz1, and R. Beardsley1

1Physical Oceanography Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543
2National Marine Fisheries Service, Woods Hole, MA 02543

We study the temporally-varying structure of the sub-tidal currents and stratification on the southern flank of Georges Bank in the vicinity of the tidal mixing front (TMF) using hydrographic surveys, meteorological data, and a moored instrument array deployed on the southern flank of Georges Bank for 160 days during the spring and summer of 1999. The array spanned the 60-m isobath (the typical summer location of the TMF) and covered a cross-bank distance of about 16 km. Seven moorings were deployed, each with a bottom-mounted acoustic Doppler current profiler and bottom pressure, temperature, and conductivity sensors. Three of the moorings were also equipped with 14 temperature sensors spanning the water column. This allows for an investigation of the temporal and spatial evolution of the TMF at unprecedented detail. In this talk, we describe the challenges of identifying the TMF in the array measurements. It is likely that the TMF's position shifts considerably in relation to the location of the mooring array during the period of the deployment. We use the cross-bank gradient of stratification to identify when the TMF is centered on the array location. When the inner-bank moorings are weakly stratified and the off-bank moorings are strongly stratified in the summer, a sharp, sub-tidal, along-bank jet is apparent (25 m below the surface, width ~ 8 km, maximum currents ~ 30 cm/s). The cross-bank currents are two-layer on either side of the jet, and three-layers at the location of the jet. Maximum cross-bank currents are about 5 cm/s.

A powerpoint version and an html version of this presentation are available on-line.