Observations of Currents in Gaoping Submarine Canyon I-Huan Lee 李逸環 National Museum of Marine Biology and Aquarium, Pingtung, Taiwan, , R.O.C. Yu-Huai Wang 王玉懷 Institute of Applied Marine Physics and Underwater Technology, National Sun Yat-sen University Kaohsiung, Taiwan, , R.O.C. James T. Liu 劉祖乾 Institute of Marine Geology and Chemistry, National Sun Yat-sen University Kaohsiung, Taiwan, , R.O.C. Ren-Chieh Lien 連仁杰 Applied Physics Laboratory, Washinton University, Seattle, USA March.25, 2009 International Sediment Trap Workshop March 23~ , NSYSU, Taiwan

2000~ major mooring or anchor observations of physical oceanography 2~3 km ~20 km Time series of two current meters on a taut-line mooring 2000,Jun.28 ~Jul.21 2 RCM8s (200 m & 270m, water depth of 300m) u, v, T, p per hour 29-hour anchor station for hourly CTD and shipboard ADCP observations 2004,Feb.26 ~ Feb. 27 sbADCP (8 m ~ 320 m) CTD (0 m ~ 350m), water depth of 410 m u, v( 2 min / 8 m) T, S, p (1 hour / 1 m) Time series of two ADCPs on a taut-line mooring 2004,Dec. 13 ~ Dec. 14, sbADCP (8 m ~ 280m) btADCP (100 m ~ 320m) sbADCP (0 m ~ 250m) CTD (0 m ~ 420 m), water depth of 440 m u, v of sbADCP (30 sec / 8 m) u, v of btADCP (5 min / 2 m) T,S, p (1 hour / 1m) Time series of bottom-mounted ADCP measurements 2006,Aug. 27 ~ Aug. 28 btADCP (87 m ~ 247 m) CTD (0m ~ 250 m), water depth of 270 m u, v (1 min / 8m) T,S, p (1 hour / 1 m) Time series of one current meter on a taut-line mooring 2004 May 25 - June 26, described in Lee and Liu (2006) 2 NADCMs (50 m & 270m, water depth of 300m) u, v, T, p per hour Exp6&7 T6KP 2007.Jan~Mar.20 btLADCP T7KP 2008.July8~Sep.11 btLADCP

Exp3 (2004) The schematic presentation for solving true heading and tilting angles of NADCM θ T : the true tilting angle θ H : the corrected heading angle (90˚-θp) and (90˚-θr) are pitch and roll readings from the NADCM. Land Sea Metronome

Exp2 Exp4 Exp2 Exp4 Exp5

Four field experiments in Gaoping submarine canyon were carried out from 2000 to Despite the differences in location and time, the results indicate a consistent picture of the semidiurnal internal tides that can be described approximately as a first-mode standing wave with velocity and density interface about 90 o out-of-phase. Sea level Temperature Velocity

Both barotropic and baroclinic tides are strong and have nearly equal speed of ~0.5 m/s. The baroclinic tide shows a clear first mode structure. The depth integrated baroclinic tidal energy flux is 14 kW/m at the canyon mouth, and is 3–7 times of that measured in Monterey Canyon (Kunze et al., 2002; Carter and Gregg, 2002).

Lee, I-H. and J. T. Liu (2006): Rectification of the heading and tilting of sediment trap arrays due to strong tidal currents in a submarine canyon. Geophysical Res. Letters, 33, L08609, doi: /2005GL Y. H. Wang, Lee, I-H.*, J. T. Liu (2008): Observation of Internal Tidal Currents in the Kaoping Canyon off Southwestern Taiwan. Estuarine, Coastal and Shelf Science, 80, pp doi: /j.ecss Lee, I-H., Y. H. Wang, J. T. Liu, W. S. Chuang and J. Xu (2009): Internal Tidal Currents in the Gaoping (Kaoping) Submarine Canyon. Journal of Marine Systems, 76, 397–404. FATES Special issue Lee, I-H., R. C. Lien, J. T. Liu and W. S. Chuang (2009): Turbulent mixing and Internal Tides in Gaoping (Kaoping) Submarine Canyon, Taiwan. Journal of Marine Systems, 76, 383–396. FATES Special issue

Monterey Submarine Canyon Barotropic velocities < 1 cm/s (Petruncio et al.,1998). Surface currents of ±15 cm/s are dominated by semidiurnal internal oscillations (Paduan and Rosenfeld,1996)

670m 590m 2004 strong internal tides propagation along the canyon toward the head at the pycnalcline around 100~150 m below surface

Low-pass flow indicated: typhoons induced large wind driven currents down to 200m below surface. Bottom (hyperpicnal) flow enhanced at days 200.

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Echo intensity (ADCP) indicated water-mass flushing out of canyon on day 198, in additional to tidal oscillations.

Two large events: July 18 (day 199) & July 21 (day 202) of 2008.

an 8 m increase on 7:10. The large increase occurred in 30 minutes of time period and bounced back with 6 m decrease in an hour. resumed to normal level in about 6 hours. the mooring line tilted for an angle of 10°. There must be a large drag to force the 30 m mooring line to curve and tilt that net float is 300 Kg. the water temperature increase smoothly and reached a peak of 15.3 ℃ from a background of 9.8 ℃ bottom cold water in 4 hours. A strong current in speed of a knot flowing southwest (210°) out of the canyon. The current reached 82 cm/s. indicated cascading of sediment-laden warm (hyperpycnal) waters into the deeper part of the canyon.

There was a pressure increase of 5 m in 20 minutes. The pressure did not bounce back after the event. Another event occurred on 22:40 of July 20 (day 201) There was an out canyon flow of a knot which causing the movement of mooring. the whole mooring slide down slop for a horizontal distance of 150 m (the bottom slope in the region is about 1:30). temperature pressure Pitch and roll speed

The Hunt for RED OCTOBER is MISSION IMPOSSIBLE in Gaoping submarine Canyon Very strong Tidal currents in Gaoping submarine canyon