Seasonal variability of tides in the deep northern South China Sea
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摘要
Tides are the major energy source for ocean mixing, regulating the variation of oceanic circulation and sediment transport in the deep sea. Here twenty months of high-resolution current profiles, which were observed via a mooring system at a water depth of 2100 m in the northern South China Sea(SCS), are used to investigate seasonal variability in deep-sea tides.Spectral analysis shows that tides in this region are dominated by diurnal tide, and both diurnal and semidiurnal tide are vertical mode-1 dominant. Baroclinic diurnal tidal current exhibits pronounced seasonal variability, showing its kinetic energy was the strongest in summer, and the maximum depth-averaged value was up to 86.7 cm~2 s~(-2), which was about 1.5 times of that in winter and twice that in spring and autumn. In contrast, baroclinic semidiurnal tide displays no evident seasonal variability. Such seasonal variability in baroclinic tide was mainly modulated by the barotropic forcing from the Luzon Strait. On the other hand,two anticyclonic eddies and one cyclonic eddy, which originated off southwestern Taiwan in winter, crossed the mooring system.The cyclonic eddy had weak impact on current velocity in the deep sea, but the two deep-reaching anticyclonic eddies enhanced the current velocity through the full-water column by inducing strong subinertial flows. Consequently, the kinetic energy of tides was strengthened and the incoherent variance of baroclinic diurnal tide increased in winter, which contributed ～85% of the variability in diurnal tide. Meanwhile, the velocity of baroclinic diurnal tide was reduced in winter, which was attributed to the weakened stratification induced by the passage of anticyclonic eddies in the deep sea. The seasonal variability of tides in the deep northern SCS can provide a dynamic mechanism for interpreting sediment transport processes in the deep sea on different time scales.
Tides are the major energy source for ocean mixing, regulating the variation of oceanic circulation and sediment transport in the deep sea. Here twenty months of high-resolution current profiles, which were observed via a mooring system at a water depth of 2100 m in the northern South China Sea(SCS), are used to investigate seasonal variability in deep-sea tides.Spectral analysis shows that tides in this region are dominated by diurnal tide, and both diurnal and semidiurnal tide are vertical mode-1 dominant. Baroclinic diurnal tidal current exhibits pronounced seasonal variability, showing its kinetic energy was the strongest in summer, and the maximum depth-averaged value was up to 86.7 cm~2 s~(-2), which was about 1.5 times of that in winter and twice that in spring and autumn. In contrast, baroclinic semidiurnal tide displays no evident seasonal variability. Such seasonal variability in baroclinic tide was mainly modulated by the barotropic forcing from the Luzon Strait. On the other hand,two anticyclonic eddies and one cyclonic eddy, which originated off southwestern Taiwan in winter, crossed the mooring system.The cyclonic eddy had weak impact on current velocity in the deep sea, but the two deep-reaching anticyclonic eddies enhanced the current velocity through the full-water column by inducing strong subinertial flows. Consequently, the kinetic energy of tides was strengthened and the incoherent variance of baroclinic diurnal tide increased in winter, which contributed ～85% of the variability in diurnal tide. Meanwhile, the velocity of baroclinic diurnal tide was reduced in winter, which was attributed to the weakened stratification induced by the passage of anticyclonic eddies in the deep sea. The seasonal variability of tides in the deep northern SCS can provide a dynamic mechanism for interpreting sediment transport processes in the deep sea on different time scales.
Tides are the major energy source for ocean mixing, regulating the variation of oceanic circulation and sediment transport in the deep sea. Here twenty months of high-resolution current profiles, which were observed via a mooring system at a water depth of 2100 m in the northern South China Sea(SCS), are used to investigate seasonal variability in deep-sea tides.Spectral analysis shows that tides in this region are dominated by diurnal tide, and both diurnal and semidiurnal tide are vertical mode-1 dominant. Baroclinic diurnal tidal current exhibits pronounced seasonal variability, showing its kinetic energy was the strongest in summer, and the maximum depth-averaged value was up to 86.7 cm~2 s~(-2), which was about 1.5 times of that in winter and twice that in spring and autumn. In contrast, baroclinic semidiurnal tide displays no evident seasonal variability. Such seasonal variability in baroclinic tide was mainly modulated by the barotropic forcing from the Luzon Strait. On the other hand,two anticyclonic eddies and one cyclonic eddy, which originated off southwestern Taiwan in winter, crossed the mooring system.The cyclonic eddy had weak impact on current velocity in the deep sea, but the two deep-reaching anticyclonic eddies enhanced the current velocity through the full-water column by inducing strong subinertial flows. Consequently, the kinetic energy of tides was strengthened and the incoherent variance of baroclinic diurnal tide increased in winter, which contributed ～85% of the variability in diurnal tide. Meanwhile, the velocity of baroclinic diurnal tide was reduced in winter, which was attributed to the weakened stratification induced by the passage of anticyclonic eddies in the deep sea. The seasonal variability of tides in the deep northern SCS can provide a dynamic mechanism for interpreting sediment transport processes in the deep sea on different time scales.
引文
Alford M H,MacKinnon J A,Nash J D,Simmons H,Pickering A,Klymak J M,Pinkel R,Sun O,Rainville L,Musgrave R,Beitzel T,Fu K H,Lu C W.2011.Energy flux and dissipation in Luzon Strait:Two tales of two ridges.J Phys Oceanogr,41:2211-2222
Alford M H,Peacock T,MacKinnon J A,Nash J D,Buijsman M C,Centurioni L R,Centuroni L R,Chao S Y,Chang M H,Farmer D M,Fringer O B,Fu K H,Gallacher P C,Graber H C,Helfrich K R,Jachec S M,Jackson C R,Klymak J M,Ko D S,Jan S,Johnston T M S,Legg S,Lee I H,Lien R C,Mercier M J,Moum J N,Musgrave R,Park J H,Pickering A I,Pinkel R,Rainville L,Ramp S R,Rudnick D L,Sarkar S,Scotti A,Simmons H L,St Laurent L C,Venayagamoorthy S K,Wang Y H,Wang J,Yang Y J,Paluszkiewicz T,Tang T Y D.2015.The formation and fate of internal waves in the South China Sea.Nature,521:65-69
Beardsley R C,Duda T F,Lynch J F,Irish J D,Ramp S R,Chiu C S,Tang T Y,Yang Y J,Fang G.2004.Barotropic tide in the northeast South China Sea.IEEE J Ocean Eng,29:1075-1086
Cao A,Guo Z,Lv X,Song J,Zhang J.2017.Coherent and incoherent features,seasonal behaviors and spatial variations of internal tides in the northern South China Sea.J Mar Syst,172:75-83
Chavanne C,Flament P,Luther D,Gurgel K W.2010.The surface expression of semidiurnal internal tides near a strong source at Hawaii.Part II:Interactions with mesoscale currents.J Phys Oceanogr,40:1180-1200
Ducet N,Le Traon P Y,Reverdin G.2000.Global high-resolution mapping of ocean circulation from TOPEX/Poseidon and ERS-1 and-2.JGeophys Res,105:19477-19498
Egbert G D,Bennett A F,Foreman M G G.1994.TOPEX/POSEIDONtides estimated using a global inverse model.J Geophys Res,99:24821
Egbert G D,Erofeeva S Y.2002.Efficient inverse modeling of barotropic ocean tides.J Atmos Ocean Technol,19:183-204
Egbert G D,Ray R D.2000.Significant dissipation of tidal energy in the deep ocean inferred from satellite altimeter data.Nature,405:775-778
Fang G,Kwok Y K,Yu K,Zhu Y.1999.Numerical simulation of principal tidal constituents in the South China Sea,Gulf of Tonkin and Gulf of Thailand.Cont Shelf Res,19:845-869
Ferrari R,Wunsch C.2009.Ocean circulation kinetic energy:Reservoirs,sources,and sinks.Annu Rev Fluid Mech,41:253-282
Friedrichs C T,Wright L D.1995.Resonant internal waves and their role in transport and accumulation of fine sediment in Eckernf?rde Bay,Baltic Sea.Cont Shelf Res,15:1697-1721
Grinsted A,Moore J C,Jevrejeva S.2004.Application of the cross wavelet transform and wavelet coherence to geophysical time series.Nonlin Processes Geophys,11:561-566
Guo P,Fang W,Liu C,Qiu F.2012.Seasonal characteristics of internal tides on the continental shelf in the northern South China Sea.J Geophys Res,117:C04023
Gustafsson K E.2001.Computations of the energy flux to mixing processes via baroclinic wave drag on barotropic tides.Deep-Sea Res Part I-Oceanogr Res Pap,48:2283-2295
Hu J Y,Kawamura H,Hong H S,Kobashi F.2001.Tidal features in the China Seas and their adjacent sea areas as derived from TOPEX/PO-SEIDON altimeter data.Chin J Ocean Limnol,19:293-305
Jan S,Chern C S,Wang J,Chao S Y.2007.Generation of diurnal K1internal tide in the Luzon Strait and its influence on surface tide in the South China Sea.J Geophys Res,112:C06019
Laurent L S,Garrett C.2002.The role of internal tides in mixing the deep ocean.J Phys Oceanogr,32:2882-2899
Lee I H,Wang Y H,Yang Y,Wang D P.2012.Temporal variability of internal tides in the northeast South China Sea.J Geophys Res,117:C02013
Liang X.2014.Semidiurnal tidal currents in the deep ocean near the East Pacific Rise between 9°and 10°N.J Geophys Res-Oceans,119:4264-4277
Liang X,Zhang Xiaoqian,Tian Jiwei.2005.Observation of internal tides and near-inertial motions in the upper 450 m layer of the northern South China Sea.Chin Sci Bull,50:2890-2895
Liu J,He Y,Wang D,Liu T,Cai S.2015.Observed enhanced internal tides in winter near the Luzon Strait.J Geophys Res-Oceans,120:7237-7252
Munk W,Wunsch C.1998.Abyssal recipes II:Energetics of tidal and wind mixing.Deep-Sea Res Part I-Oceanogr Res Pap,45:1977-2010
Nan F,Xue H,Yu F.2015.Kuroshio intrusion into the South China Sea:Areview.Prog Oceanogr,137:314-333
Nash J D,Kunze E,Toole J M,Schmitt R W.2004.Internal tide reflection and turbulent mixing on the continental slope.J Phys Oceanogr,34:1117-1134
Park J H,Watts D R.2006.Internal tides in the southwestern Japan/East Sea.J Phys Oceanogr,36:22-34
Pawlowicz R,Beardsley B,Lentz S.2002.Classical tidal harmonic analysis including error estimates in MATLAB using T_TIDE.Comput Geosci,28:929-937
Peine F,Turnewitsch R,Mohn C,Reichelt T,Springer B,Kaufmann M.2009.The importance of tides for sediment dynamics in the deep seaEvidence from the particulate-matter tracer234Th in deep-sea environments with different tidal forcing.Deep-Sea Res Part I-Oceanogr Res Pap,56:1182-1202
Rainville L,Pinkel R.2006.Propagation of low-mode internal waves through the ocean.J Phys Oceanogr,36:1220-1236
Ribbe J,Holloway P E.2001.A model of suspended sediment transport by internal tides.Cont Shelf Res,21:395-422
Shang X,Liu Q,Xie X,Chen G,Chen R.2015.Characteristics and seasonal variability of internal tides in the southern South China Sea.Deep-Sea Res Part I-Oceanogr Res Pap,98:43-52
Torrence C,Compo G P.1998.A practical guide to wavelet analysis.Bull Amer Meteorol Soc,79:61-78
Turnewitsch R,Reyss J L,Nycander J,Waniek J J,Lampitt R S.2008.Internal tides and sediment dynamics in the deep sea-Evidence from radioactive234Th/238U disequilibria.Deep-Sea Res Part I-Oceanogr Res Pap,55:1727-1747
Wang G,Su J,Chu P C.2003.Mesoscale eddies in the South China Sea observed with altimeter data.Geophys Res Lett,30:2121
Welch P D.1967.The use of fast fourier transform for the estimation of power spectra:A method based on time averaging over short,modified periodograms.IEEE Transactions Audio Electroacoustics,15:70-73
Xu Z,Yin B,Hou Y,Liu A K.2014.Seasonal variability and north-south asymmetry of internal tides in the deep basin west of the Luzon Strait.JMar Syst,134:101-112
Xu Z,Yin B,Hou Y,Xu Y.2013.Variability of internal tides and nearinertial waves on the continental slope of the northwestern South China Sea.J Geophys Res-Oceans,118:197-211
Zhang Y,Liu Z,Zhao Y,Li J,Liang X.2015.Effect of surface mesoscale eddies on deep-sea currents and mixing in the northeastern South China Sea.Deep-Sea Res Part II-Top Stud Oceanogr,122:6-14
Zhang Y,Liu Z,Zhao Y,Wang W,Li J,Xu J.2014.Mesoscale eddies transport deep-sea sediments.Sci Rep,4:5937
Zhao Z,Alford M H.2006.Source and propagation of internal solitary waves in the northeastern South China Sea.J Geophys Res,111:C11012
Zheng Q,Susanto R D,Ho C R,Song Y T,Xu Q.2007.Statistical and dynamical analyses of generation mechanisms of solitary internal waves in the northern South China Sea.J Geophys Res,112:C03021
Zilberman N V,Merrifield M A,Carter G S,Luther D S,Levine M D,Boyd T J.2011.Incoherent Nature of M2Internal Tides at the Hawaiian Ridge.J Phys Oceanogr,41:2021-2036
Zu T,Gan J,Erofeeva S Y.2008.Numerical study of the tide and tidal dynamics in the South China Sea.Deep-Sea Res Part I-Oceanogr Res Pap,55:137-154
Alford M H,Peacock T,MacKinnon J A,Nash J D,Buijsman M C,Centurioni L R,Centuroni L R,Chao S Y,Chang M H,Farmer D M,Fringer O B,Fu K H,Gallacher P C,Graber H C,Helfrich K R,Jachec S M,Jackson C R,Klymak J M,Ko D S,Jan S,Johnston T M S,Legg S,Lee I H,Lien R C,Mercier M J,Moum J N,Musgrave R,Park J H,Pickering A I,Pinkel R,Rainville L,Ramp S R,Rudnick D L,Sarkar S,Scotti A,Simmons H L,St Laurent L C,Venayagamoorthy S K,Wang Y H,Wang J,Yang Y J,Paluszkiewicz T,Tang T Y D.2015.The formation and fate of internal waves in the South China Sea.Nature,521:65-69
Beardsley R C,Duda T F,Lynch J F,Irish J D,Ramp S R,Chiu C S,Tang T Y,Yang Y J,Fang G.2004.Barotropic tide in the northeast South China Sea.IEEE J Ocean Eng,29:1075-1086
Cao A,Guo Z,Lv X,Song J,Zhang J.2017.Coherent and incoherent features,seasonal behaviors and spatial variations of internal tides in the northern South China Sea.J Mar Syst,172:75-83
Chavanne C,Flament P,Luther D,Gurgel K W.2010.The surface expression of semidiurnal internal tides near a strong source at Hawaii.Part II:Interactions with mesoscale currents.J Phys Oceanogr,40:1180-1200
Ducet N,Le Traon P Y,Reverdin G.2000.Global high-resolution mapping of ocean circulation from TOPEX/Poseidon and ERS-1 and-2.JGeophys Res,105:19477-19498
Egbert G D,Bennett A F,Foreman M G G.1994.TOPEX/POSEIDONtides estimated using a global inverse model.J Geophys Res,99:24821
Egbert G D,Erofeeva S Y.2002.Efficient inverse modeling of barotropic ocean tides.J Atmos Ocean Technol,19:183-204
Egbert G D,Ray R D.2000.Significant dissipation of tidal energy in the deep ocean inferred from satellite altimeter data.Nature,405:775-778
Fang G,Kwok Y K,Yu K,Zhu Y.1999.Numerical simulation of principal tidal constituents in the South China Sea,Gulf of Tonkin and Gulf of Thailand.Cont Shelf Res,19:845-869
Ferrari R,Wunsch C.2009.Ocean circulation kinetic energy:Reservoirs,sources,and sinks.Annu Rev Fluid Mech,41:253-282
Friedrichs C T,Wright L D.1995.Resonant internal waves and their role in transport and accumulation of fine sediment in Eckernf?rde Bay,Baltic Sea.Cont Shelf Res,15:1697-1721
Grinsted A,Moore J C,Jevrejeva S.2004.Application of the cross wavelet transform and wavelet coherence to geophysical time series.Nonlin Processes Geophys,11:561-566
Guo P,Fang W,Liu C,Qiu F.2012.Seasonal characteristics of internal tides on the continental shelf in the northern South China Sea.J Geophys Res,117:C04023
Gustafsson K E.2001.Computations of the energy flux to mixing processes via baroclinic wave drag on barotropic tides.Deep-Sea Res Part I-Oceanogr Res Pap,48:2283-2295
Hu J Y,Kawamura H,Hong H S,Kobashi F.2001.Tidal features in the China Seas and their adjacent sea areas as derived from TOPEX/PO-SEIDON altimeter data.Chin J Ocean Limnol,19:293-305
Jan S,Chern C S,Wang J,Chao S Y.2007.Generation of diurnal K1internal tide in the Luzon Strait and its influence on surface tide in the South China Sea.J Geophys Res,112:C06019
Laurent L S,Garrett C.2002.The role of internal tides in mixing the deep ocean.J Phys Oceanogr,32:2882-2899
Lee I H,Wang Y H,Yang Y,Wang D P.2012.Temporal variability of internal tides in the northeast South China Sea.J Geophys Res,117:C02013
Liang X.2014.Semidiurnal tidal currents in the deep ocean near the East Pacific Rise between 9°and 10°N.J Geophys Res-Oceans,119:4264-4277
Liang X,Zhang Xiaoqian,Tian Jiwei.2005.Observation of internal tides and near-inertial motions in the upper 450 m layer of the northern South China Sea.Chin Sci Bull,50:2890-2895
Liu J,He Y,Wang D,Liu T,Cai S.2015.Observed enhanced internal tides in winter near the Luzon Strait.J Geophys Res-Oceans,120:7237-7252
Munk W,Wunsch C.1998.Abyssal recipes II:Energetics of tidal and wind mixing.Deep-Sea Res Part I-Oceanogr Res Pap,45:1977-2010
Nan F,Xue H,Yu F.2015.Kuroshio intrusion into the South China Sea:Areview.Prog Oceanogr,137:314-333
Nash J D,Kunze E,Toole J M,Schmitt R W.2004.Internal tide reflection and turbulent mixing on the continental slope.J Phys Oceanogr,34:1117-1134
Park J H,Watts D R.2006.Internal tides in the southwestern Japan/East Sea.J Phys Oceanogr,36:22-34
Pawlowicz R,Beardsley B,Lentz S.2002.Classical tidal harmonic analysis including error estimates in MATLAB using T_TIDE.Comput Geosci,28:929-937
Peine F,Turnewitsch R,Mohn C,Reichelt T,Springer B,Kaufmann M.2009.The importance of tides for sediment dynamics in the deep seaEvidence from the particulate-matter tracer234Th in deep-sea environments with different tidal forcing.Deep-Sea Res Part I-Oceanogr Res Pap,56:1182-1202
Rainville L,Pinkel R.2006.Propagation of low-mode internal waves through the ocean.J Phys Oceanogr,36:1220-1236
Ribbe J,Holloway P E.2001.A model of suspended sediment transport by internal tides.Cont Shelf Res,21:395-422
Shang X,Liu Q,Xie X,Chen G,Chen R.2015.Characteristics and seasonal variability of internal tides in the southern South China Sea.Deep-Sea Res Part I-Oceanogr Res Pap,98:43-52
Torrence C,Compo G P.1998.A practical guide to wavelet analysis.Bull Amer Meteorol Soc,79:61-78
Turnewitsch R,Reyss J L,Nycander J,Waniek J J,Lampitt R S.2008.Internal tides and sediment dynamics in the deep sea-Evidence from radioactive234Th/238U disequilibria.Deep-Sea Res Part I-Oceanogr Res Pap,55:1727-1747
Wang G,Su J,Chu P C.2003.Mesoscale eddies in the South China Sea observed with altimeter data.Geophys Res Lett,30:2121
Welch P D.1967.The use of fast fourier transform for the estimation of power spectra:A method based on time averaging over short,modified periodograms.IEEE Transactions Audio Electroacoustics,15:70-73
Xu Z,Yin B,Hou Y,Liu A K.2014.Seasonal variability and north-south asymmetry of internal tides in the deep basin west of the Luzon Strait.JMar Syst,134:101-112
Xu Z,Yin B,Hou Y,Xu Y.2013.Variability of internal tides and nearinertial waves on the continental slope of the northwestern South China Sea.J Geophys Res-Oceans,118:197-211
Zhang Y,Liu Z,Zhao Y,Li J,Liang X.2015.Effect of surface mesoscale eddies on deep-sea currents and mixing in the northeastern South China Sea.Deep-Sea Res Part II-Top Stud Oceanogr,122:6-14
Zhang Y,Liu Z,Zhao Y,Wang W,Li J,Xu J.2014.Mesoscale eddies transport deep-sea sediments.Sci Rep,4:5937
Zhao Z,Alford M H.2006.Source and propagation of internal solitary waves in the northeastern South China Sea.J Geophys Res,111:C11012
Zheng Q,Susanto R D,Ho C R,Song Y T,Xu Q.2007.Statistical and dynamical analyses of generation mechanisms of solitary internal waves in the northern South China Sea.J Geophys Res,112:C03021
Zilberman N V,Merrifield M A,Carter G S,Luther D S,Levine M D,Boyd T J.2011.Incoherent Nature of M2Internal Tides at the Hawaiian Ridge.J Phys Oceanogr,41:2021-2036
Zu T,Gan J,Erofeeva S Y.2008.Numerical study of the tide and tidal dynamics in the South China Sea.Deep-Sea Res Part I-Oceanogr Res Pap,55:137-154