1. ENS Alicia A. Washkevich, USN
An Overview of the Internal Tidal Bore at the Head of the Submarine Canyon in Monterey Bay
OC 3570 Cruise JUL 2003
Project by:
ENS Alicia A. Washkevich, USN

2. Introduction: OC3570 NPS student cruise 2 Legs: 21-24 JUL & 24-28 JUL
Legs traveled from Monterey south to San Luis Obispo and back

3. Internal Tidal Bore Unsteady flow caused by tidal forcing
Common to Monterey Bay
Submarine Canyon
Narrowing
Rising sea floor / slope
Long distance
Characterized by:
Lower temperature and salinity extending down in water column
Increased wave height
Greater current velocity at the bottom of the water column traveling toward shallow bathymetry

5. Bathymetry of Monterey Bay
Time Series 2
Time Series 1

6. Instruments / Data Used
25 Hour CTD Time Series Data
Shipboard ADCP data
Mean Sea Level data from NOAA/NOS CO-OPS

7. CTD’s Time Series 1 Time Series 2
27 CTD casts
26 JUL – 27 JUL
Average maximum depth 162m
Time Series 2
27 JUL – 28 JUL
Temperature and salinity measurements used and plotted with depth / pressure

8. Salinity from CTD Time Series 1
T-S Plot
Pressure/100
Yearday

9. Temp from CTD Time Series 1
Pressure/100
Yearday

10. Salinity from CTD Time Series 2
Pressure/100
Yearday

11. Temp from CTD Time Series 2
Pressure/100
Yearday

12. CTD Data Shows:
Lower temperature extending down at Yearday and for Series 1
Lower salinity extending down at approximately same time
Lower temperature extending down at Yearday and for Series 2

13. ADCP (Acoustic Doppler Current Profiler
Onboard Pt Sur
Transmits 150 kHz
Measures velocity of water from reflection off suspended particles

14. East/West Velocity cm/s PBOR1
Some Bottom Intensification
Yearday -1

15. North/South Velocity cm/s PBOR1
Depth/100
Yearday -1

16. East/West Velocity cm/s PBOR2
Depth
Yearday -1

17. North/South Velocity cm/s PBOR2
“sloshing”
Depth
“spilling”
Yearday -1

18. PBOR2 U vs. V (Overlay)
“E/W”
“N/S”

19. PBOR2 Discussion: Not perfectly aligned E/W (slightly oblique)
Exception to general trend (One would assume a NE/SW but overlay shows a NW/SE movement)
Canyon wall deeper on Southern side, may spill over more to South
Sloshing to North and South above canyon wall (freedom of movement)
North may be possible reflection

20. ADCP Data shows: PBOR1 clearly defined
Most notable E/W – deep water funneled “in and out” of canyon
PBOR2
Slightly offset
Less strength
Different but possible

21. Propagating or Standing Wave?
U and V components taken at depths of 71, 87, and 103 meters
6 Minute Mean Seal Level Data for Monterey
Station #
’ N
’ W

22. (PBOR1)

23. (PBOR2)

24. (PBOR1)

25. Propagating Internal Wave

26. Sea Level Shows: Bit of a lag Strong velocity at peaks
Generally followed shape

27. CONCLUSIONS:
Internal bore was present in the form of a propagating internal wave
The bore displayed customary characteristics
Lower salinity and temperature extending down into water column
Bottom intensification (velocity)
Mirrored mean sea level heights with strong velocity at peaks

28. Questions?
Special Thanks to: LT Kristen Watts RAN, Chris Miller, Tarry Rago, Prof. Collins