The University of British Columbia

Keywords
Strait of Georgia, Estuarine Circulation, Tracers Fluxes/Sources/Sinks, Box Model

Gulf of St Lawrence, Inertial Oscillations

Presentations
The Seasonal Cycle of Nitrate Upward Entrainment and net Primary Production in the Strait of Georgia During 2002-2005.Riche & R. Pawlowicz 2006 Ocean Sciences Meeting, American Geophysical Union, Honolulu, HA, United States, Feb 24^th 2006

STRATOGEM 2002-2005: Transports and Biochemical Tracer Fluxes Derived with a Three-Box Inverse Model of the Strait of Georgia. O. Riche & R. Pawlowicz. Canadian Meteorological and Oceanographic Society Congress 2005, Richmond, BC, Canada, May 31^st 2005

Mass, heat and nutrient fluxes in the Strait of Georgia during STRATOGEM using a box inverse model. O. Riche, R. Pawlowicz and R. Lee. Eastern Pacific Ocean Conference 2004, Dunsmuir, BC, Canada, September 24^th 2004

Interannual Variability in the Strait of Georgia During the STRATOGEM Project. O. Riche, R. Pawlowicz, R. Lee and S. Harris AGU Oceans Meeting, Portland OR, USA, January 28^th 2004

Publication

None Yet.

Paper Contributions

STRATOGEM--The Strait of Georgia Ecosystem Project. R. Pawlowicz, S. Allen, J. Dower, R. Lee, S. Harris, M. Halverson, O. Riche, T. Bird. 2003 Georgia Basin/Puget Sound Resarch Conference Proceedings, February 2004.

The Circulation and Residence Time of the Strait of Georgia Using a Simple Mixing-box Approach. Rich Pawlowicz, O. Riche, M. Halverson. Atmosphere-Ocean, in press. 2007

Award
Mohammed El-Sabh's Excellence Scholarship (Oceanography) March 1^st 2001 - Université du Québec à Rimouski

PhD Research
The STRATOGEM program is a comprehensive study of the Strait of Georgia, a narrow and long body of water flanked with the mainland coast of British Columbia and the Vancouver Island. My PhD research took advantage of the monthly observations collected using the CCG hovercraft SYAY ("Friend" in Native American). These obserations were both high-resolution vertical profiles of the water column and data derived from the analysis of discrete water samples for essential physical and biogeochemical parameters. Completing this dataset with weather air/sea data of the Strait of Georgia and oceanographical data from the North of Pugent Sound (South of the Strait of Georgia), I quantified the surface net heat budget, the estuarine water transports and the nutrient budgets in the Strait of Georgia. Using a time-dependent inverse box-model approach, I computed monthly water transports. The physical analysis of the estuarine circulation and the freshwater forcing suggests that the Strait of Georgia is a "stiff" estuary, like theoretical analyses and different physical analyses found for other estuaries. Like a stiff spring that does not easily deform under mechanical stress, the Strait of Georgia estuarine circulation responds weakly to a large discharge of freshwater. Using a fractional power fit to represent the sensitivity to freshwater inflow, I found a relationship in R^1/n with 1/n≤1/3. Using a forward time-dependent box-model approach, I computed the monthly uptake rate of phosphate, nitrate and silicic acid and production rate of dissolved oxygen. Using the classic Redfield ratios C:N:P, I obtained estimates of the monthly primary productivity of the Strait of Georgia and found that the primary productivity is mainly due to net vertical entrainment of nutrient-rich deep seawater. The comparison of the silicic acid uptake rate to the phosphate uptake rate suggests that in spring silicic acid is used up faster than previous studies suggested (Si:N≈2:1): either spring diatoms are more silicified in the Strait than in previously estuaries or they compete with heterotrophic species for silicic acid, e.g. heterotrophic silicoflagellates. The comparison of the oxygen production rate with the phosphate uptake rate only allowed to speculate on the magnitude of the regenerated primary productivity and the heterotrophic respiration rate.

M.Sc. Thesis
"Étude de la Génération des Oscillations Inertielles en Fonction des Variations du Vent sur le Plateau Madelinien"

Over the Madgedalana Shallows in the Gulf of St Lawrence, driven by a sustaining wind or slowly damped after a wind blow, inertial oscillations can be important for transport of zooplanktonic larvae. They can be compared to the motion of a "slab" of water sliding over the water column. Using GPS positionning data from surface drifters and surface wind data over the Summer 1996, I tried to identify inertial events and to extract information about the conditions of minimal time, minimal intensity or angular phase required to generate them.

D.E.S.S. Thesis
"Refroidissement du Moteur d'un Véhicule Sous-Marin Autonome"
Autonomous Unmanned Vehicles (AUVs) have a large spectrum of applications. The CALAS, a torpedo-shaped AUV designed by CNIM France was used for studies of the Rhone River Plume on the Mediterranean shore (M.A.U.V.E. program). Due to its carbon fiber body, various sources of stress and friction and the AUV high speed, the AUV engine tended to heat up rapidly. The objective of this work was to find a way to reduce the rate of heating or to move the hot spot off the engine.

Maîtrise Thesis
"Effet de Modulation Fréquentielle d'un Fond Sinusoïdal dans un Canal à Houle"
A sinusoidal bottom was set up in the middle of a long wave tank while the remainder of the tank bottom was originally flat. A set of two resistive probes were running in opposite directions along the tank. They were measuring surface levels and thus incoming, reflected and transmitted waves above the sinusoidal bottom. The objective of this work was to study not only the propagation of waves through the sinusoidal feature but also the strong dispersion and the frequential modulation of the waves.