Observations of Currents in Gaoping Submarine Canyon

1. Observations of Currents in Gaoping Submarine Canyon I-Huan Lee 李逸環 National Museum of Marine Biology and Aquarium, Pingtung, Taiwan, 944-50, R.O.C. ihlee@nmmba.gov.tw Yu-Huai Wang 王玉懷 Institute of Applied Marine Physics and Underwater Technology, National Sun Yat-sen University Kaohsiung, Taiwan, 804-24, R.O.C. yhwang@mail.nsysu.edu.tw James T. Liu 劉祖乾 Institute of Marine Geology and Chemistry, National Sun Yat-sen University Kaohsiung, Taiwan, 804-24, R.O.C. james@mail.nsysu.edu.tw Ren-Chieh Lien 連仁杰 Applied Physics Laboratory, Washinton University, Seattle, USA chuang@ntu.edu.tw March.25, 2009 International Sediment Trap Workshop March 23~27 2009, NSYSU, Taiwan

2. 2000~2008 7 major mooring or anchor observations of physical oceanography 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 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 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 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 T6KP 2007.Jan~Mar.20 btLADCP T7KP 2008.July8~Sep.11 btLADCP 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) 2~3 km Exp6&7 ~20 km

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

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5. Four field experiments in Gaoping submarine canyon were carried out from 2000 to 2006. 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 90o out-of-phase. Temperature Sea level Velocity

7. 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).

8. 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:10.1029/2005GL025183. 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. 153-160. doi:10.1016/j.ecss.2008.07.016 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

9. 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)

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

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

13. Calmaegi Fung Wong Kammuri Nuri

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

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

16. the water temperature increase smoothly and reached a peak of 15.3℃ from a background of 9.8℃bottom cold water in 4 hours. 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. 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.

17. temperature Another event occurred on 22:40 of July 20 (day 201) 2008. pressure There was a pressure increase of 5 m in 20 minutes. The pressure did not bounce back after the event. Pitch and roll 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). speed

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