Baroclinic Effect on Modeling Deep Flow in Brown Passage, BC, Canada

Yuehua Lin,Todd Mudge,Keath Borg,David B Fissel

doi:10.3390/jmse6040117

Yuehua Lin, Todd Mudge + Show 2 more

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https://doi.org/10.3390/jmse6040117

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Abstract

Brown Passage is a deep (up to 200 m) ocean channel connecting the western offshore waters of Hecate Strait and Dixon Entrance on the Pacific continental shelf with the eastern inland waters of Chatham Sound in Northern British Columbia, Canada. A high-resolution 3D finite difference hydrodynamic model, COastal CIRculation and SEDiment transport Model (COCIRM-SED), was developed in 2010 and 2013 to determine the tidal and wind-driven currents of this area. The barotropic model results for ocean currents were found to be in reasonably good agreement with the historical ocean current observations at near-surface and middle depth available for Brown Passage. Operated from October 2014 to April 2015, the first modern oceanographic measurement program in Brown Passage found surprisingly strong near-bottom currents (the 99th percentile current speed reaches 53 cm/s at 196 m). As a result, the COCIRM-SED model was modified and rerun, with the most important change incorporating water density/salinity fields as modeled variables. This change led to considerable improvements in the ability of the model to generate episodes of relatively strong currents in the bottom layers. The bottom intensification in ocean currents in Brown Passage is shown to be due to semi-diurnal internal tides, which were not previously included in the barotropic version of the 3D model. This finding for the near-bottom flow from the qualitative modeling study is important for applications of the potential sediment deposition and resuspension studies.

Highlights

Brown Passage is a deep ocean channel connecting the western offshore waters of Hecate Strait and Dixon Entrance on the Pacific continental shelf with the eastern inland waters of Chatham Sound in Northern British Columbia, Canada (Figure 1)
Among them the two largest and deepest passages are the eastward extension of Dixon Entrance to the north of Dundas Island; and Brown Passage in central Chatham Sound, which are the most important channels allowing the exchanges of water and wave energy with the larger water bodies to the west
Brown Passage is a deep ocean channel connecting the western offshore waters of Hecate Strait on the Pacific continental shelf with the eastern inland waters of Chatham Sound in Northern British Columbia, Canada. Recent research into this oceanic environment is motivated by studies of the possible use of this area for disposal at sea of dredged sediments arising from expansion of marine terminals in and around Prince Rupert Harbor in Chatham Sound

Summary

Introduction

Brown Passage is a deep (up to 200 m below chart datum, i.e., the reference level for depths used on a nautical chart) ocean channel connecting the western offshore waters of Hecate Strait and Dixon Entrance on the Pacific continental shelf with the eastern inland waters of Chatham Sound in Northern British Columbia, Canada (Figure 1). Among them the two largest and deepest passages are the eastward extension of Dixon Entrance to the north of Dundas Island; and Brown Passage in central Chatham Sound, which are the most important channels allowing the exchanges of water and wave energy with the larger water bodies to the west. One LANDSAT-8 scene, 28 August 2013 (Skeena River ddiisscchhargge ooff 666655mm33//ss))wwaasssseelleecctteeddaanndd eennhhaanncceedd,, aass sshhoowwnn in Figure 2 (Figure 5 in [[11]])).

Previous Modeling Studies

Model Performance

Findings

Discussion

Summary and Conclusions