observations of currents in gaoping submarine canyon i-huan lee 李逸環 national museum of marine...
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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.
Yu-Huai Wang 王玉懷Institute of Applied Marine Physics and Underwater Technology, National Sun Yat-sen University
Kaohsiung, Taiwan, 804-24, [email protected]
James T. Liu 劉祖乾Institute of Marine Geology and Chemistry, National Sun Yat-sen University
Kaohsiung, Taiwan, 804-24, [email protected]
Ren-Chieh Lien 連仁杰Applied Physics Laboratory, Washinton University, Seattle, USA
March.25, 2009
International Sediment Trap Workshop March 23~27 2009, NSYSU, Taiwan
2000~20087 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.212 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. 27sbADCP (8 m ~ 320 m)CTD (0 m ~ 350m) , water depth of 410 mu, 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 mu, 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 mu, 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
T6KP2007.Jan~Mar.20btLADCP
T7KP2008.July8~Sep.11btLADCP
G r a v i t y
p
T: True tilting
H: Corrected heading
r
x1
x5
x1
x2 x2
x4
x3
Pitch
Roll
Heading
True heading
90-p
90-r
Gravityz
p
T: True tilting
H: Corrected heading
r
x1
x5
x1
x2 x2
x4
x3
Pitch
Roll
Heading
True heading
90-p
90-r
Gravityz
Exp3 (2004) The schematic presentation for solving true heading and tilting angles of NADCM
rpp
rp
p
rH
rprpr
T
x
x
x
x
x
x
x
x
x
x
x
x
costantancos
cossintan
cos
costantan
sinsinsinsinsin
sinsin
sinsin
1
1
11
1
21
4
51
1
1
11
1
21
1
31
θT : the true tilting angleθH : the corrected heading angle
(90˚-θp) and (90˚-θr) are pitch and roll readings from the NADCM.
LandSea
Metronome
Exp2
Exp4
Exp2
Exp4 Exp5
Exp5
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 d
escribed approximately as a first-mode standing wave with velocity and density interface about 90o 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: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
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.
CalmaegiFung WongKammuri Nuri
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) 2008.
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