observations of currents in gaoping submarine canyon i-huan lee 李逸環 national museum of marine...
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![Page 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](https://reader035.vdocuments.mx/reader035/viewer/2022062714/56649d4d5503460f94a2c96e/html5/thumbnails/1.jpg)
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
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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
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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
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Exp2
Exp4
Exp2
Exp4 Exp5
Exp5
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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
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•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).
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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
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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)
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670m
590m
2004
strong internal tides propagation along the canyon toward the head at the pycnalcline around 100~150 m below surface
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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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CalmaegiFung WongKammuri Nuri
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Echo intensity (ADCP) indicated water-mass flushing out of canyon on day 198, in additional to tidal oscillations.
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Two large events: July 18 (day 199) & July 21 (day 202) of 2008.
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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.
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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
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The Hunt for RED OCTOBER is MISSION IMPOSSIBLE
in Gaoping submarine Canyon
Very strong Tidal currents in Gaoping submarine canyon