The advances in understanding the South China Sea (SCS) western boundary current (SCSwbc) have been reviewed since the works of Dale (1956) and Wyrtki (1961) in the middle of the 20th century. The features of ...The advances in understanding the South China Sea (SCS) western boundary current (SCSwbc) have been reviewed since the works of Dale (1956) and Wyrtki (1961) in the middle of the 20th century. The features of the pattern of SCSwbc and the oceanic phenomena associated with it are focused on. The current is driven mainly by monsoon over the SCS and partially by winds over the tropical Pacific governed by the island rule. The SCSwbc exhibits strong seasonal variation in its direction and patterns. In winter, the current is strong and flows southwestward along the South China shelf and slope from the east of Dongsha Islands to the northern central Vietnamese coast, then turns to the south along the central and southern Vietnamese coast, and finally partially exits the SCS through the Karimata Strait. In summer and early fall, the SCSwbc can be divided into three segments based on their characteristics. The southern segment is stable, flowing northward from the Karimata Strait up to about 11 N, where it separates from the coast forming an eastward offshore current. The separation of the current from Vietnamese coast induces some striking features, such as upwelling and cold sea-surface temperature. The middle segment off the central Vietnamese coast may have a bimodal behavior: northward coastal current and meandering current in early summer (June–July), and cyclonic gyre in later summer and early fall (August–September). The northern segment is featured by the summer SCS Warm Current on the South China shelf and a southwestward subsurface current along the continental slope.展开更多
In order to quantitatively estimate the volume and property transports between the South China Sea and Indonesian Seas via the Karimata Strait, two trawi-resistant bottom mounts, with ADCPs embedded, were deployed in ...In order to quantitatively estimate the volume and property transports between the South China Sea and Indonesian Seas via the Karimata Strait, two trawi-resistant bottom mounts, with ADCPs embedded, were deployed in the strait to measure the velocity profile as part of the South China Sea-Indonesian Seas trans- port/exchange (SITE) program. A pair of surface and bottom acoustic modems was employed to transfer the measured velocity without recovering the mooring. The advantage and problems of the instruments in this field work are reported and discussed. The field observations confirm the existence of the South Chi- na Sea branch of Indonesian throughflow via the Karimata Strait with a stronger southward flow in boreal winter and weaker southward bottom flow in boreal summer, beneath the upper layer northward (reversal) flow. The estimate of the averaged volume, heat and freshwater transports from December 2007 to March 2008 (winter) is (-2.7±1.1)×10^6 m^3/s, (-0.30±0.11) PW, 2008 (summer) is (1.2±0.6)×10^6 m^3/s, (0.14±0.03) PW, (-0.18±0.07) × 106 m3/s and from May to September (0.12±0.04)×10^6 m^3/s and for the entire record from December 2007 to October 2008 is (-0.5±1.9)×10^6 m^3/s, (-0.05±0.22) PW, (-0.01±0.15)×10^6 m^3/s (nega- tive/positive represents southward/northward transport), respectively. The existence of southward bottom flow in boreal summer implies that the downward sea surface slope from north to south as found by Fang et al. (2010) for winter is a year-round phenomenon.展开更多
On the basis of maps of sea level anomalies data set from October 1992 to January 2004, pronounced low frequency variations with periods of about 500 d are detected in the area near 20°N from 160°W to 130...On the basis of maps of sea level anomalies data set from October 1992 to January 2004, pronounced low frequency variations with periods of about 500 d are detected in the area near 20°N from 160°W to 130°E. A linear two-layer model is employed to explain the mechanism. It is found that the first-mode long baroclinic Rossby waves at 20°N in the northwest Pacific propagate westward in the form of free waves at a speed of about 10.3 cm/s. This confirms that the observed low frequency variabilities appear as baroclinic Rossby waves. It further shows that these low frequency variabilities around 20°N in the northwest Pacific can potentially be predicted with a lead up to 900 d.展开更多
The global distributions of eight principal tidal constituents, M2, S2, K1, O1, N2, K2, P1, and Q1, are derived using TOPEX/Poseidon and JASON-1(T/P-J) satellite altimeter data for 16 a. The intercomparison of the d...The global distributions of eight principal tidal constituents, M2, S2, K1, O1, N2, K2, P1, and Q1, are derived using TOPEX/Poseidon and JASON-1(T/P-J) satellite altimeter data for 16 a. The intercomparison of the derived harmonics at 7000 subsatellite track crossover points shows that the root mean square (RMS) values of the tidal height differences of the above eight constituents range from 1.19 cm to 2.67 cm, with an average of about 2 cm. The RMS values of the tidal height differences between T/P-J solutions and the harmonics from ground measurements at 152 tidal gauge stations for the above constituents range from 0.34 cm to 1.08 cm, and the relative deviations range from 0.031 to 0.211. The root sum square of the RMS differences of these eight constituents is 2.12 cm, showing the improvement of the present model over the existing global ocean tidal models. Based on the obtained tidal model the global ocean tidal energetics is studied and the global distribution of the tidal power input density by tide-generating force of each constituent is calculated, showing that the power input source regions of semidiurnal tides are mainly concentrated in the tropical belt between 30S and 30N, while the power input source regions of diurnal tides are mainly concentrated off the tropic oceans. The global energy dissipation rates of the M2, S2, K1, O1, N2, P1, K2 and Q1 tides are 2.424, 0.401, 0.334, 0.160, 0.113, 0.035, 0.030 and 0.006 TW, respectively. The total global tidal dissipation rate of these eight constituents amounts to 3.5 TW.展开更多
A numerical method is designed to examine the response properties of real sea areas to open ocean forcing. The application of this method to modeling the China's adjacent seas shows that the Bohai Sea has a highest p...A numerical method is designed to examine the response properties of real sea areas to open ocean forcing. The application of this method to modeling the China's adjacent seas shows that the Bohai Sea has a highest peak response frequency (PRF) of 1.52 d^-1; the northern Yellow Sea has a PRF of 1.69 d^-1; the Gyeonggi Bay has a high amplitude gain plateau in the frequency band roughly from 1.7 to 2.7 d^-1; the Yellow Sea (includ- ing the Gyeonggi Bay), the East China Sea shelf and the Taiwan Strait have a common high amplitude gain band with frequencies around 1.76 to 1.78 d^-1 and are shown to be a system that responds to the open ocean forcing in favor of amplifying the waves with frequencies in this band; the Beibu Gulf, the Gulf of Thailand and the South China Sea deep basin have PRFs of 0.91, 1.01 and 0.98 d^-1 respectively. In addition, the East China Sea has a Poincare mode PRF of 3.91 d^-1. The PRFs of the Bohal Sea, the northern Yellow Sea, the Bei- bu Gulf and the South China Sea can be explained by a classical quarter (half for the Bohai Sea) wavelength resonance theory. The results show that further investigations are needed for the response dynamics of the Yellow Sea-East China Sea-Taiwan Strait system, the East China Sea Poincare mode, the Talwan Strait, and the Gulf of Thailand.展开更多
A global prognostic model based on MOM4p1,which is a primitive equation nonBoussinesq numerical model,has been integrated with 1 400 years from the state of rest based on the realistic topography to study the long-ter...A global prognostic model based on MOM4p1,which is a primitive equation nonBoussinesq numerical model,has been integrated with 1 400 years from the state of rest based on the realistic topography to study the long-term pattern of combined wind-driven and thermodynamically-driven general circulation.The model is driven by monthly climatological mean forces and includes 192×189 horizontal grids and 31 pressure-based vertical levels.The main objective is to investigate the mass and heat transports at interbasin passages and their compensations and roles in the global ocean circulation under equilibrium state of long-term spin up.The kinetic energy analysis divides the spin up process into three stages:the quasi-stable state of wind driven current,the growing phase of thermodynamical circulation and the equilibrium state of thermohaline circulation.It is essential to spin up over a thousand years in order to reach the thermohaline equilibrium state from a state of rest.The Arctic Throughflow from the Bering Strait to the Greenland Sea and the Indonesian Throughflow(ITF) are captured and examined with their compensations and existing data.Analysis reveals that the slope structures of sea surface height are the dynamical driving mechanism of the Pacific-Arctic-Atlantic throughflow and ITF.The analysis denotes,in spite of O(1.4×106m3/s) of the southward volume transport in the northern Atlantic,that there is still O(1 PW) of heat transported northward since the northward currents in the upper layer carry much higher temperature water than the southward flowing northern Atlantic deep water(NADW).Meridional volume and heat transports are focused on the contributions to NADW renewals and Atlantic meridional overturning circulation(AMOC).Quantitative descriptions of the interbasin exchanges are explained by meridional compensations and supported by previous observations and numerical modeling results.Analysis indicates that the volume and heat exchanges on the interbasin passages proposed in this article manifest their hub roles in the Great Ocean Conveyor System.展开更多
The tide-induced mixing plays an important role in the regulation of ocean circulation.Numerical simulation of continental shelf circulation is found to exhibit an unreasonable vertical thermohaline structure without ...The tide-induced mixing plays an important role in the regulation of ocean circulation.Numerical simulation of continental shelf circulation is found to exhibit an unreasonable vertical thermohaline structure without consideration of tide effects.In this study,we establish a harmonic analyzed parameterization of tide-induced(HAT) mixing,by which means to derive time-depended function of mixing coefficient based on harmonic analysis of the vertical mixing coefficient.By employing HAT mixing parameterization scheme,a series of numerical experiments are conducted for the Yellow Sea.Numerical results show that an ocean circulation model with the HAT mixing involved is capable of reproducing the reasonable thermohaline structure of the Yellow Sea Cold Water Mass,similar to structures produced by explicit tidal forcing on the open boundary.The advantage of the HAT method is its faster computation time,compared with models that directly resolve explicit tidal motion.The HAT parameterization for the tide-induced mixing has potential to improve both the accuracy and efficiency of ocean circulation and climate models.展开更多
On the basis of the latest version of a U.S. Navy generalized digital environment model (GDEM-V3.0) and World Ocean Atlas (WOA13), the hydraulic theory is revisited and applied to the Luzon Strait, providing a fre...On the basis of the latest version of a U.S. Navy generalized digital environment model (GDEM-V3.0) and World Ocean Atlas (WOA13), the hydraulic theory is revisited and applied to the Luzon Strait, providing a fresh look at the deepwater overflow there. The result reveals that: (1) the persistent density difference between two sides of the Luzon Strait sustains an all year round deepwater overflow from the western Pacific to the South China Sea (SCS); (2) the seasonal variability of the deepwater overflow is influenced not only by changes in the density difference between two sides of the Luzon Strait, but also by changes in its upstream layer thickness; (3) the deepwater overflow in the Luzon Strait shows a weak semiannual variability; (4) the seasonal mean circulation pattern in the SCS deep basin does not synchronously respond to the seasonality of the deepwater overflow in the Luzon Strait. Moreover, the deepwater overflow reaches its seasonal maximum in December (based on GDEM-V3.0) or in fall (October-December, based on the WOA13), accompanied by the lowest temperature of the year on the Pacific side of the Luzon Strait. The seasonal variability of the deepwater overflow is consistent with the existing longest (3.5 a) continuous observation along the major deepwater passage of the Luzon Strait.展开更多
In this study, we develop a variable-grid global ocean general circulation model (OGCM) with a fine grid (1/6)° covering the area from 20°S-50°N and from 99°-150°E, and use the model to in...In this study, we develop a variable-grid global ocean general circulation model (OGCM) with a fine grid (1/6)° covering the area from 20°S-50°N and from 99°-150°E, and use the model to investigate the isopycnal surface circulation in the South China Sea (SCS). The simulated results show four layer structures in vertical: the surface and subsurface circulation of the SCS are characterized by the monsoon driven circulation, with basin-scaled cyclonic gyre in winter and anti-cyclonic gyre in summer. The intermediate layer circulation is opposite to the upper layer, showing anti-cyclonic gyre in winter but cyclonic gyre in summer. The circulation in the deep layer is much weaker in spring and summer, with the maximum velocity speed below 0.6 cm/s. In fall and winter, the SCS deep layer circulation shows strong east boundary current along the west coast of Philippine with the velocity speed at 1.5 m/s, which flows southward in fall and northward in winter. The results have also revealed a fourlayer vertical structure of water exchange through the Luzon Strait. The dynamics of the intermediate and deep circulation are attributed to the monsoon driving and the Luzon Strait transport forcing.展开更多
The predictability of marine ecosystem dynamics models is one of the most vital factors to limit their practical applications, of which the stability is the fundamental condition. In order to discuss the stability and...The predictability of marine ecosystem dynamics models is one of the most vital factors to limit their practical applications, of which the stability is the fundamental condition. In order to discuss the stability and Hopf bifurcation of marine ecosystem dynamics models, an approach based on a theorem termed dimension reduction was proposed and further applied in the mass-conservative nutrient-phytoplankton-zooplankton-detritus(NPZD) model in this paper. Results showed that the nonsingular equilibrium point of NPZD model was analytically stable in use of the dimension reduction theorem and the Hopf bifurcation might occur when model parameters changed along the threshold values. The analytical results of the NPZD model were further verified by numerical simulation in this study. It can be concluded that this approach based on the dimension reduction theorem is well applicable to the theoretical analysis of a kind of stability problems and Hopf bifurcation of massconservative systems.展开更多
The loading tides are calculated by means of the Green's function method based on a high-resolution regional ocean tide model, the TOPO7.0 global ocean tide model, and the Gutenberg-Bullen A Earth model. The resul...The loading tides are calculated by means of the Green's function method based on a high-resolution regional ocean tide model, the TOPO7.0 global ocean tide model, and the Gutenberg-Bullen A Earth model. The results show that the maximal amplitude of M2 vertical displacement loading (VDL) tide in the Bohai, Yellow, and East China Seas exceeding 28mm appears 150km off the Zhejiang coast; the second maximum exceeding 20mm appears in Inchon Bay; and the third maximum exceeding 14mm is located in the northeast of the North Yellow Sea. The maximal amplitudes of S2 VDL tide at the above three locations exceed 10, 8, and 4mm, respectively. The maximal amplitudes of the K1 and O1 VDL tides, exceeding 13 and 10 mm respectively, appear near the central and north Ryukyu Islands; the amplitudes tend to decease toward the inward areas. The phases of semidiurnal VDL tides are basically opposite to those of corresponding ocean tides. The phases of diurnal VDL tides are basically opposite to those of corresponding ocean tides in the most part of the East China Sea and the eastern part of the South Yellow Sea. This anti-phase relationship generally does not hold in the rest parts of the Bohai and Yellow Seas. The distribution patterns of self-attraction and loading (SAL) tides are very similar to those of VDL tides. The SAL tides have amplitudes about 1.2-1.7 times of the corresponding VDL tides and their phases are basically opposite to the corresponding VDL tides. The maximal amplitude of M2 SAL tide also appears off the Zhejiang coast, with a magnitude exceeding 42mm.展开更多
The mean sea surface heights (sea surface topography) of the South China, East China, Yellow and Bohai Seas are derived from an ocean general circulation model and surface air pressure. The circulation model covers th...The mean sea surface heights (sea surface topography) of the South China, East China, Yellow and Bohai Seas are derived from an ocean general circulation model and surface air pressure. The circulation model covers the global oceans, with fine grid (1/6°)? covering the East Asian marginal seas and coarse grid (3°) covering the rest part of the global oceans. The result shows that the China 1985 Na-tional Altitude Datum is 24.7 cm above the mean sea surface height of the world oceans. The mean sea surface in the coastal ocean adjacent to China is higher in the south than in the north. Intercomparison of the model results with the geodetic leveling measurements at 28 coastal tidal stations shows a standard deviation of 4.8 cm and a fitting coefficient of 95.3%. After correction through linear regression, the standard deviation is reduced to 4.5 cm. This indicates that the accuracy of model results is sufficient for practical application. Based on the model results, the mean sea surface heights for the展开更多
11-year satellite altimeter sea surface height (SSH) anomaly data from January 1993 to December 2003 are used to present the dominant spatial patterns and temporal variations of the South China Sea (SCS) surface circu...11-year satellite altimeter sea surface height (SSH) anomaly data from January 1993 to December 2003 are used to present the dominant spatial patterns and temporal variations of the South China Sea (SCS) surface circulation through Empirical Orthogonal Function (EOF) analysis. The first three EOF modes show the obvious seasonal variations of SSH in the SCS. EOF mode one is generally characterized by a basin-wide circulation. Mode two describes the double-cell basin scale circulation structure. The two cells were located off west of the Luzon Island and southeast of Vietnam, respectively. EOF mode three presents the mesoscale eddy structure in the western SCS, which develops into a strong cyclonic eddy rapidly from July to September. EOF mode one and mode three are also embedded with interannual signals, indicating that the SCS surface circulation variation is influenced by El Ni o events prominently. The strong El Ni o of 1997/98 obviously changed the SCS circulation structure. This study also shows that there existed a series of mesoscale eddies in the western SCS, and their temporal variation indicates intra-seasonal and in-terannual signals.展开更多
基金The National Basic Research Program ("973" Program) of China under contract Nos 2011CB403500 and 2012CB957803the National Natural Science Foundation of China under contract Nos 41006018 and 40730842the National High Technology Research and Development Program ("863" Program) of China under contract No. 2008AA09A402
文摘The advances in understanding the South China Sea (SCS) western boundary current (SCSwbc) have been reviewed since the works of Dale (1956) and Wyrtki (1961) in the middle of the 20th century. The features of the pattern of SCSwbc and the oceanic phenomena associated with it are focused on. The current is driven mainly by monsoon over the SCS and partially by winds over the tropical Pacific governed by the island rule. The SCSwbc exhibits strong seasonal variation in its direction and patterns. In winter, the current is strong and flows southwestward along the South China shelf and slope from the east of Dongsha Islands to the northern central Vietnamese coast, then turns to the south along the central and southern Vietnamese coast, and finally partially exits the SCS through the Karimata Strait. In summer and early fall, the SCSwbc can be divided into three segments based on their characteristics. The southern segment is stable, flowing northward from the Karimata Strait up to about 11 N, where it separates from the coast forming an eastward offshore current. The separation of the current from Vietnamese coast induces some striking features, such as upwelling and cold sea-surface temperature. The middle segment off the central Vietnamese coast may have a bimodal behavior: northward coastal current and meandering current in early summer (June–July), and cyclonic gyre in later summer and early fall (August–September). The northern segment is featured by the summer SCS Warm Current on the South China shelf and a southwestward subsurface current along the continental slope.
基金The National Science Foundation of the United States under contract No.OCE-07-25935the Office of Naval Research of the United States under contract No.N00014-08-1-0618 (for US LDEO)+4 种基金the National Basic Research Program under contract No.2011CB403502the International Cooperation Program of China under contract No.2010DFB23580the International Cooperation Program of State Oceanic Administration of China under contract No.QY0213022the First Institute of Oceanography,the State Oceanic Administration of China under contract No.2010G06 (for Chinese researchers)the Lamont-Doherty Earth Obseruatory contribution No.7626
文摘In order to quantitatively estimate the volume and property transports between the South China Sea and Indonesian Seas via the Karimata Strait, two trawi-resistant bottom mounts, with ADCPs embedded, were deployed in the strait to measure the velocity profile as part of the South China Sea-Indonesian Seas trans- port/exchange (SITE) program. A pair of surface and bottom acoustic modems was employed to transfer the measured velocity without recovering the mooring. The advantage and problems of the instruments in this field work are reported and discussed. The field observations confirm the existence of the South Chi- na Sea branch of Indonesian throughflow via the Karimata Strait with a stronger southward flow in boreal winter and weaker southward bottom flow in boreal summer, beneath the upper layer northward (reversal) flow. The estimate of the averaged volume, heat and freshwater transports from December 2007 to March 2008 (winter) is (-2.7±1.1)×10^6 m^3/s, (-0.30±0.11) PW, 2008 (summer) is (1.2±0.6)×10^6 m^3/s, (0.14±0.03) PW, (-0.18±0.07) × 106 m3/s and from May to September (0.12±0.04)×10^6 m^3/s and for the entire record from December 2007 to October 2008 is (-0.5±1.9)×10^6 m^3/s, (-0.05±0.22) PW, (-0.01±0.15)×10^6 m^3/s (nega- tive/positive represents southward/northward transport), respectively. The existence of southward bottom flow in boreal summer implies that the downward sea surface slope from north to south as found by Fang et al. (2010) for winter is a year-round phenomenon.
基金This study was supported by the National Natural Science Foundation of China under contract Nos 40136010 and 40520140074.
文摘On the basis of maps of sea level anomalies data set from October 1992 to January 2004, pronounced low frequency variations with periods of about 500 d are detected in the area near 20°N from 160°W to 130°E. A linear two-layer model is employed to explain the mechanism. It is found that the first-mode long baroclinic Rossby waves at 20°N in the northwest Pacific propagate westward in the form of free waves at a speed of about 10.3 cm/s. This confirms that the observed low frequency variabilities appear as baroclinic Rossby waves. It further shows that these low frequency variabilities around 20°N in the northwest Pacific can potentially be predicted with a lead up to 900 d.
基金The National Natural Science Foundation of China under contract No. 40676009 and 40606006the Basic Research Project of Qingdao Science and Technology Program under contract No. 11-1-4-98-jch
文摘The global distributions of eight principal tidal constituents, M2, S2, K1, O1, N2, K2, P1, and Q1, are derived using TOPEX/Poseidon and JASON-1(T/P-J) satellite altimeter data for 16 a. The intercomparison of the derived harmonics at 7000 subsatellite track crossover points shows that the root mean square (RMS) values of the tidal height differences of the above eight constituents range from 1.19 cm to 2.67 cm, with an average of about 2 cm. The RMS values of the tidal height differences between T/P-J solutions and the harmonics from ground measurements at 152 tidal gauge stations for the above constituents range from 0.34 cm to 1.08 cm, and the relative deviations range from 0.031 to 0.211. The root sum square of the RMS differences of these eight constituents is 2.12 cm, showing the improvement of the present model over the existing global ocean tidal models. Based on the obtained tidal model the global ocean tidal energetics is studied and the global distribution of the tidal power input density by tide-generating force of each constituent is calculated, showing that the power input source regions of semidiurnal tides are mainly concentrated in the tropical belt between 30S and 30N, while the power input source regions of diurnal tides are mainly concentrated off the tropic oceans. The global energy dissipation rates of the M2, S2, K1, O1, N2, P1, K2 and Q1 tides are 2.424, 0.401, 0.334, 0.160, 0.113, 0.035, 0.030 and 0.006 TW, respectively. The total global tidal dissipation rate of these eight constituents amounts to 3.5 TW.
基金The National Natural Science Foundation of China under contract Nos 40676009 and 40606006the Basic Research Project of Qingdao Science and Technology Program of China under contract No.11-1-4-98-jch
文摘A numerical method is designed to examine the response properties of real sea areas to open ocean forcing. The application of this method to modeling the China's adjacent seas shows that the Bohai Sea has a highest peak response frequency (PRF) of 1.52 d^-1; the northern Yellow Sea has a PRF of 1.69 d^-1; the Gyeonggi Bay has a high amplitude gain plateau in the frequency band roughly from 1.7 to 2.7 d^-1; the Yellow Sea (includ- ing the Gyeonggi Bay), the East China Sea shelf and the Taiwan Strait have a common high amplitude gain band with frequencies around 1.76 to 1.78 d^-1 and are shown to be a system that responds to the open ocean forcing in favor of amplifying the waves with frequencies in this band; the Beibu Gulf, the Gulf of Thailand and the South China Sea deep basin have PRFs of 0.91, 1.01 and 0.98 d^-1 respectively. In addition, the East China Sea has a Poincare mode PRF of 3.91 d^-1. The PRFs of the Bohal Sea, the northern Yellow Sea, the Bei- bu Gulf and the South China Sea can be explained by a classical quarter (half for the Bohai Sea) wavelength resonance theory. The results show that further investigations are needed for the response dynamics of the Yellow Sea-East China Sea-Taiwan Strait system, the East China Sea Poincare mode, the Talwan Strait, and the Gulf of Thailand.
基金The National Basic Research Program Grant of China under contact No.2011CB403502the International Cooperation Program Grant of China under contact No.2010DFB23580+3 种基金the International Cooperation Program of State Oceanic Administration of China under contract No.QY0213022project supported by the First Institute of Oceanographythe State Oceanic Administration of China under contract No.2010G06author Guan Yuping is supported by The National Natural Science Foundation of China under contact Nos 40976011 and 91228202
文摘A global prognostic model based on MOM4p1,which is a primitive equation nonBoussinesq numerical model,has been integrated with 1 400 years from the state of rest based on the realistic topography to study the long-term pattern of combined wind-driven and thermodynamically-driven general circulation.The model is driven by monthly climatological mean forces and includes 192×189 horizontal grids and 31 pressure-based vertical levels.The main objective is to investigate the mass and heat transports at interbasin passages and their compensations and roles in the global ocean circulation under equilibrium state of long-term spin up.The kinetic energy analysis divides the spin up process into three stages:the quasi-stable state of wind driven current,the growing phase of thermodynamical circulation and the equilibrium state of thermohaline circulation.It is essential to spin up over a thousand years in order to reach the thermohaline equilibrium state from a state of rest.The Arctic Throughflow from the Bering Strait to the Greenland Sea and the Indonesian Throughflow(ITF) are captured and examined with their compensations and existing data.Analysis reveals that the slope structures of sea surface height are the dynamical driving mechanism of the Pacific-Arctic-Atlantic throughflow and ITF.The analysis denotes,in spite of O(1.4×106m3/s) of the southward volume transport in the northern Atlantic,that there is still O(1 PW) of heat transported northward since the northward currents in the upper layer carry much higher temperature water than the southward flowing northern Atlantic deep water(NADW).Meridional volume and heat transports are focused on the contributions to NADW renewals and Atlantic meridional overturning circulation(AMOC).Quantitative descriptions of the interbasin exchanges are explained by meridional compensations and supported by previous observations and numerical modeling results.Analysis indicates that the volume and heat exchanges on the interbasin passages proposed in this article manifest their hub roles in the Great Ocean Conveyor System.
基金The National Key Research and Development Program of China under contract No.2017YFC1404201the National Natural Science Foundation of China(NSFC)under contract Nos 41606040 and 41606036+1 种基金the NSFC-Shandong Joint Fund for Marine Science Research Centers under contract No.U1606405the National High Technology Research and Development Program(863 Program)of China under contract No.2013AA09A506
文摘The tide-induced mixing plays an important role in the regulation of ocean circulation.Numerical simulation of continental shelf circulation is found to exhibit an unreasonable vertical thermohaline structure without consideration of tide effects.In this study,we establish a harmonic analyzed parameterization of tide-induced(HAT) mixing,by which means to derive time-depended function of mixing coefficient based on harmonic analysis of the vertical mixing coefficient.By employing HAT mixing parameterization scheme,a series of numerical experiments are conducted for the Yellow Sea.Numerical results show that an ocean circulation model with the HAT mixing involved is capable of reproducing the reasonable thermohaline structure of the Yellow Sea Cold Water Mass,similar to structures produced by explicit tidal forcing on the open boundary.The advantage of the HAT method is its faster computation time,compared with models that directly resolve explicit tidal motion.The HAT parameterization for the tide-induced mixing has potential to improve both the accuracy and efficiency of ocean circulation and climate models.
基金The National Natural Science Foundation of China(NSFC)-Shandong Joint Fund for Marine Science Research Centers of China under contract No.U1606405the National Basic Research Program(973 Program) of China under contract No.2011CB403502+2 种基金the National High Technology Research and Development Program(863 Program) of China under contract No.2013AA09A506the National Program on Global Change and Air-Sea Interaction under contract Nos GASI-IPOVAI-01-02 and GASI-03-01-01-04the National Natural Science Foundation of China under contract No.41606040
文摘On the basis of the latest version of a U.S. Navy generalized digital environment model (GDEM-V3.0) and World Ocean Atlas (WOA13), the hydraulic theory is revisited and applied to the Luzon Strait, providing a fresh look at the deepwater overflow there. The result reveals that: (1) the persistent density difference between two sides of the Luzon Strait sustains an all year round deepwater overflow from the western Pacific to the South China Sea (SCS); (2) the seasonal variability of the deepwater overflow is influenced not only by changes in the density difference between two sides of the Luzon Strait, but also by changes in its upstream layer thickness; (3) the deepwater overflow in the Luzon Strait shows a weak semiannual variability; (4) the seasonal mean circulation pattern in the SCS deep basin does not synchronously respond to the seasonality of the deepwater overflow in the Luzon Strait. Moreover, the deepwater overflow reaches its seasonal maximum in December (based on GDEM-V3.0) or in fall (October-December, based on the WOA13), accompanied by the lowest temperature of the year on the Pacific side of the Luzon Strait. The seasonal variability of the deepwater overflow is consistent with the existing longest (3.5 a) continuous observation along the major deepwater passage of the Luzon Strait.
基金The National High Technology Research and Development Program(863 Program)of China under contract No.2013AA09A506the National Natural Science Foundation of China-Shandong Joint Fund for Marine Science Research Centers under contract No.U1406404+1 种基金the National Basic Research Program(973 Program)of China under contract No.2011CB956000the National Natural Science Foundation of China under contract No.40476016
文摘In this study, we develop a variable-grid global ocean general circulation model (OGCM) with a fine grid (1/6)° covering the area from 20°S-50°N and from 99°-150°E, and use the model to investigate the isopycnal surface circulation in the South China Sea (SCS). The simulated results show four layer structures in vertical: the surface and subsurface circulation of the SCS are characterized by the monsoon driven circulation, with basin-scaled cyclonic gyre in winter and anti-cyclonic gyre in summer. The intermediate layer circulation is opposite to the upper layer, showing anti-cyclonic gyre in winter but cyclonic gyre in summer. The circulation in the deep layer is much weaker in spring and summer, with the maximum velocity speed below 0.6 cm/s. In fall and winter, the SCS deep layer circulation shows strong east boundary current along the west coast of Philippine with the velocity speed at 1.5 m/s, which flows southward in fall and northward in winter. The results have also revealed a fourlayer vertical structure of water exchange through the Luzon Strait. The dynamics of the intermediate and deep circulation are attributed to the monsoon driving and the Luzon Strait transport forcing.
基金The National Natural Science Foundation of China under contract Nos 41206111 and 41206112
文摘The predictability of marine ecosystem dynamics models is one of the most vital factors to limit their practical applications, of which the stability is the fundamental condition. In order to discuss the stability and Hopf bifurcation of marine ecosystem dynamics models, an approach based on a theorem termed dimension reduction was proposed and further applied in the mass-conservative nutrient-phytoplankton-zooplankton-detritus(NPZD) model in this paper. Results showed that the nonsingular equilibrium point of NPZD model was analytically stable in use of the dimension reduction theorem and the Hopf bifurcation might occur when model parameters changed along the threshold values. The analytical results of the NPZD model were further verified by numerical simulation in this study. It can be concluded that this approach based on the dimension reduction theorem is well applicable to the theoretical analysis of a kind of stability problems and Hopf bifurcation of massconservative systems.
基金supported by National Natural Science Foundation of China (Grant Nos. 40676009 and 40606006)Qingdao Science and Technology Basic Research Program (Grant No. 11-1-4-98-JCH)
文摘The loading tides are calculated by means of the Green's function method based on a high-resolution regional ocean tide model, the TOPO7.0 global ocean tide model, and the Gutenberg-Bullen A Earth model. The results show that the maximal amplitude of M2 vertical displacement loading (VDL) tide in the Bohai, Yellow, and East China Seas exceeding 28mm appears 150km off the Zhejiang coast; the second maximum exceeding 20mm appears in Inchon Bay; and the third maximum exceeding 14mm is located in the northeast of the North Yellow Sea. The maximal amplitudes of S2 VDL tide at the above three locations exceed 10, 8, and 4mm, respectively. The maximal amplitudes of the K1 and O1 VDL tides, exceeding 13 and 10 mm respectively, appear near the central and north Ryukyu Islands; the amplitudes tend to decease toward the inward areas. The phases of semidiurnal VDL tides are basically opposite to those of corresponding ocean tides. The phases of diurnal VDL tides are basically opposite to those of corresponding ocean tides in the most part of the East China Sea and the eastern part of the South Yellow Sea. This anti-phase relationship generally does not hold in the rest parts of the Bohai and Yellow Seas. The distribution patterns of self-attraction and loading (SAL) tides are very similar to those of VDL tides. The SAL tides have amplitudes about 1.2-1.7 times of the corresponding VDL tides and their phases are basically opposite to the corresponding VDL tides. The maximal amplitude of M2 SAL tide also appears off the Zhejiang coast, with a magnitude exceeding 42mm.
基金This work was supported by the Major State Basic Research Program (Grant No. G1999043808) the National Natural Science Foundation of China (Grant Nos. 49876010 and 40076004) the Innovation Program of the Chinese Academy of Sciences (Grant No. KZCX2-
文摘The mean sea surface heights (sea surface topography) of the South China, East China, Yellow and Bohai Seas are derived from an ocean general circulation model and surface air pressure. The circulation model covers the global oceans, with fine grid (1/6°)? covering the East Asian marginal seas and coarse grid (3°) covering the rest part of the global oceans. The result shows that the China 1985 Na-tional Altitude Datum is 24.7 cm above the mean sea surface height of the world oceans. The mean sea surface in the coastal ocean adjacent to China is higher in the south than in the north. Intercomparison of the model results with the geodetic leveling measurements at 28 coastal tidal stations shows a standard deviation of 4.8 cm and a fitting coefficient of 95.3%. After correction through linear regression, the standard deviation is reduced to 4.5 cm. This indicates that the accuracy of model results is sufficient for practical application. Based on the model results, the mean sea surface heights for the
基金Acknowledgements The satellite altimeter data were provided by AVIS0, CNES, France. This work was supported by the Ministry of Science and Technology of China through the National Basic Research Program (Grant No. 2006CB403603), the National Natural Science Foundation of China (Grant Nos. 40376002, 40520140074 and 40136010), Science Foundation of Guangdong Province (Grant No. 05003688).
文摘11-year satellite altimeter sea surface height (SSH) anomaly data from January 1993 to December 2003 are used to present the dominant spatial patterns and temporal variations of the South China Sea (SCS) surface circulation through Empirical Orthogonal Function (EOF) analysis. The first three EOF modes show the obvious seasonal variations of SSH in the SCS. EOF mode one is generally characterized by a basin-wide circulation. Mode two describes the double-cell basin scale circulation structure. The two cells were located off west of the Luzon Island and southeast of Vietnam, respectively. EOF mode three presents the mesoscale eddy structure in the western SCS, which develops into a strong cyclonic eddy rapidly from July to September. EOF mode one and mode three are also embedded with interannual signals, indicating that the SCS surface circulation variation is influenced by El Ni o events prominently. The strong El Ni o of 1997/98 obviously changed the SCS circulation structure. This study also shows that there existed a series of mesoscale eddies in the western SCS, and their temporal variation indicates intra-seasonal and in-terannual signals.