Proposed Abstract Title

Satellite based study of wind and river forcing of the Fraser River plume

Type of Presentation

Oral

Session Title

Remote sensing technology to monitor the short and long term dynamic of the Salish Sea

Location

2016SSEC

Description

The Fraser River is the largest source of inorganic particles to the Strait of Georgia (SoG). Most of the particles escape the Fraser estuary and mudflats, and enter the SoG in a buoyant plume. The fate of these particles now depends on our understanding of how the plume responds to forcing by wind, river flow, and tides. The distribution of inorganic particles affects important processes such as light attenuation in the water column and adsorption of contaminants.

Previous studies of particle dispersal in the SoG were based on light transmission profiles or sediment traps, and they lacked sufficient resolution in time and space to adequately address how the large and fickle Fraser River plume responds to forcing. Satellite imagery can overcome some of these sampling limitations. In this talk we present early results from an analysis of 13 years of satellite imagery of the SoG. Maps of suspended particulate material were derived from the application of a single-band algorithm utilizing MODIS HiRes band 1 (620 - 670 nm), which has a nominal resolution of 250 m.

After validating the images with in situ optical and hydrographic data, we conditionally average the images to determine how the plume varies in response to river flow and wind conditions. Under calm winds, the plume occupies a larger surface area as river flow increases. Surprisingly, it undertakes a southward "set" under calm winds, contrary to the influence of rotation. Under northwesterly winds, the plume is advected southward, even reaching as far south as the San Juan Islands under strong winds. Under southeasterly winds the plume is advected to the northwest. However, it is important to point out that these are just average tendencies, and they are only somewhat representative of the myriad of shapes and sizes displayed by the plume.

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Satellite based study of wind and river forcing of the Fraser River plume

2016SSEC

The Fraser River is the largest source of inorganic particles to the Strait of Georgia (SoG). Most of the particles escape the Fraser estuary and mudflats, and enter the SoG in a buoyant plume. The fate of these particles now depends on our understanding of how the plume responds to forcing by wind, river flow, and tides. The distribution of inorganic particles affects important processes such as light attenuation in the water column and adsorption of contaminants.

Previous studies of particle dispersal in the SoG were based on light transmission profiles or sediment traps, and they lacked sufficient resolution in time and space to adequately address how the large and fickle Fraser River plume responds to forcing. Satellite imagery can overcome some of these sampling limitations. In this talk we present early results from an analysis of 13 years of satellite imagery of the SoG. Maps of suspended particulate material were derived from the application of a single-band algorithm utilizing MODIS HiRes band 1 (620 - 670 nm), which has a nominal resolution of 250 m.

After validating the images with in situ optical and hydrographic data, we conditionally average the images to determine how the plume varies in response to river flow and wind conditions. Under calm winds, the plume occupies a larger surface area as river flow increases. Surprisingly, it undertakes a southward "set" under calm winds, contrary to the influence of rotation. Under northwesterly winds, the plume is advected southward, even reaching as far south as the San Juan Islands under strong winds. Under southeasterly winds the plume is advected to the northwest. However, it is important to point out that these are just average tendencies, and they are only somewhat representative of the myriad of shapes and sizes displayed by the plume.