1. Evaluation of the surface flows and
salinity in the Fraser River plume in a
model
Jie Liu, Susan Allen, Nancy Soontiens, Mark Halverson
University of British Columbia

2. Outline
• Background
• Data-Model Comparisons
• Model Problems
• Objective
• Model Configurations
• Analysis
• Model Runs
• Model Improvements
• Summary
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3. Background
• Fraser River plume
• Implications in
various fields
• Three-dimensional
ocean model
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4. Data-Model Comparisons
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• Ferry data from Ocean Networks Canada (ONC).
• 2 hrs per complete transect.
• 4 round trips during weekdays and fewer at weekends.

5. Data-Model Comparisons
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• Drifter data by Mark Halverson and Rich Pawlowicz, UBC.
• Released during ebb tides on October 8, 2014.
• Tracked for 29 hrs.

6. Model Problems
• Cross-strait velocities are too weak
• Along-strait flows are too strong
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7. Objective
To improve the surface flows of the Fraser River
plume in a three-dimensional baroclinic model by
modifying the geometry of the Fraser River and
investigating the effects of turbulence parameters.
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8. Model Configurations
• NEMO 3.4
• ~500 m horizontal
1-27 m vertical
• Based on Soontiens et
al., 2015: Fraser River
was modified to be
longer and deeper
• Background vertical
eddy viscosity and
diffusivity reduced to
and
, separately.
8
sm
125-
101


sm
126-
101



9. Analysis
Baseline Long River
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10. Analysis
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• Max(Background values, turbulence closure）
• Reduced background vertical eddy viscosity and diffusivity
separate the surface and intermediate water movements.
Averaged Diffusivity at VENUS Central Averaged Viscosity at VENUS Central

11. Model Runs
 Baseline: short river + high viscosity + high diffusivity
 Long river + high viscosity + high diffusivity
 Long river + low viscosity + high diffusivity
 Long river + low viscosity + low diffusivity
Period: September 25~ October 10, 2014
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12. Model Improvements
Long river: produces slightly stronger cross-strait flows
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13. Model Improvements
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14. Model Improvements
14
Difference between model and ferry observations

15. Summary
• Generally, model results and ferry-based observations for
salinity values exhibit similar ranges.
• Extended and deepened river channel improves surface
currents by generating stronger cross-strait surface flows.
• Reducing vertical eddy viscosity and diffusivity is important
to produce weaker along-strait flows.
• Lower diffusivity reduces upper layer salinity values, which
increases the accuracy of model results compared to observed
ferry salinity.
• A longer river with lower viscosity and diffusivity minimizes
the overall discrepancies for modeled surface flows.
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16. Thank you!
Any questions?