The variability of the sediment plume and ocean circulation features of the Nass River Estuary, British Columbia

The Nass River discharges into Nass Bay and Iceberg Bay, which are adjoining tidal inlets located within the northern inland waters of British Columbia, Canada. After the Skeena River, the Nass River is the second longest river within northern British Columbia, which discharges directly into Canadian waters of the Pacific Ocean. It is also supports one of the most productive salmon fisheries in northern British Columbia. The Nass River discharges into the eastern end of Nass Bay. Nass Bay, in turn feeds into Portland Canal and the fresh surface waters then flows westward to the Pacific Ocean via Dixon Entrance. The tides in Northern British Columbia are very large with a tidal height range of just over 7 m. Nass Bay is a shallow inlet of less than 10 km in length with typical water depths of than 10 m or less. The existing knowledge of oceanographic processes in Nass and Iceberg Bays was rudimentary until three years ago, when the first modern oceanographic measurements were obtained. In this study, the seasonal and tidal variability of the lateral extent of the Nass River surface plume is mapped from analyses of Landsat satellite data spanning the period from 2008 to 2015. A high resolution coupled three dimensional (3D) hydrodynamic model was developed and implemented, within the widely used and accepted Delft3D modeling framework, which was forced and validated using recent 2013-2016 in-situ oceanographic measurements. The combined satellite and numerical modeling methods are used to study the physical oceanographic and sediment transport regime of Nass and Iceberg Bays and the adjoining waters of Portland Inlet and Observatory Inlet. The ocean circulation of Nass and Iceberg Bays was found to be dominated by tidal currents, and by the highly seasonal and variable Nass River freshwater discharges. Complex lateral spatial patterns in the tidal currents occur due to the opening of the southwestern side of Nass Bay onto the deeper adjoining waters of Iceberg Bay. Surface winds are limited to a secondary role in the circulation variability. The sediment dynamics of the Nass Bay system features a very prominent surface sediment plume present from the time of freshet in mid-spring through to large rainfall runoff events in the fall. The time-varying turbidity distribution and transport paths of the Nass River sediment discharges in the study area were characterized using the model results combined with an analysis of several high-resolution multi-year Landsat satellite data sets

Analysis and interpretation of SAR data for the English Channel

The launch of the ERS-1 SAR in 1991 has provided oceanographers with an opportunity to obtain repeatable direct measurements of small scale topography (roughness) of the sea surface. This thesis investigates the application of SAR for monitoring coastal oceanography in the English Channel. That a radar type instrument can detect small scale features, such as tidal fronts and nearshore shoals and banks, was demonstrated by a preliminary qualitative examination of Seasat SAR images. Further investigations of a small coastal front using an airborne altimeter, combined with results from an existing monitoring programme, verified that frontal features can be associated with variations in surface roughness. The quantitative analysis of ERS-1 SAR measures of backscatter in terms of the correspondence of the data to the modulation of short waves is the main subject of this work. The multi-temporal capabilities of ERS-1 SAR have enabled a rigorous analysis of these data, enabling both the performance of the calibration routine and the backscatter relationships with dynamic features to be examined for varied wind and tide conditions. A power loss caused by saturation of the analogue to digital converter (ADC) was found to result in underestimates of backscatter values by up to 3 dB, not previously accounted for. The significance and effectiveness of using the fullest possible correction was demonstrated by comparing SAR-derived estimates of backscatter across range with predictions from an empirical wind retrieval model (CM0D4), which describes the dependence of backscatter on incidence angle. It was found that in the coastal zone the backscatter signal is dominated by transitional wind effects, which often confuse or obscure any dynamic sea surface signatures. Estimates of the wind speed contribution to surface roughness were successfully achieved using the CM0D4 to accuracies within the error bands of the model (±2 ms&quot; ). Comparisons of SAR-derived wind speeds between images demonstrated the importance of correcting for the effects of the SAR viewing geometry. It was empirically shown that a normalised SAR-derived apparent wind speed residual gave a proportional representation of surface roughness that could not be achieved using a direct measure of backscatter. It is shown that the non-linearities introduced into the data by these effects should be removed if comparisons of the backscatter signature of surface roughness variations are to be made between images, with physical variables, such as currents, or with model predictions.</p