Understanding of the temporal variation of oceanic heat content (OHC) is of fundamental importance to the prediction of climate change and associated global meteorological phenomena. However, OHC characteristics in ...Understanding of the temporal variation of oceanic heat content (OHC) is of fundamental importance to the prediction of climate change and associated global meteorological phenomena. However, OHC characteristics in the Pacific and Indian oceans are not well understood. Based on in situ ocean temperature and salinity profiles mainly from the Argo program, we estimated the upper layer (0-750 m) OHC in the Indo-Pacific Ocean (40°S-40°N, 30°E-80°W). Spatial and temporal variability of OHC and its likely physical mechanisms are also analyzed. Climatic distributions of upper-layer OHC in the Indian and Pacific oceans have a similar saddle pattern in the subtropics, and the highest OHC value was in the northern Arabian Sea. However, OHC variabilities in the two oceans were different. OHC in the Pacific has an east-west see-saw pattern, which does not appear in the Indian Ocean. In the Indian Ocean, the largest change was around 10°S. The most interesting phenomenon is that, there was a long-term shift of OHC in the Indo-Pacific Ocean during 2001-2012. Such variation coincided with modulation of subsurface temperature/salinity. During 2001-2007, there was subsurface cooling (freshening) nearly the entire upper 400 m layer in the western Pacific and warming (salting) in the eastern Pacific. During 2008-2012, the thermocline deepened in the western Pacific but shoaled in the east. In the Indian Ocean, there was only cooling (upper 150 m only) and freshening (almost the entire upper 400 m) during 2001-2007. The thermocline deepened during 2008-2012 in the Indian Ocean. Such change appeared from the equator to off the equator and even to the subtropics (about 20°N/S) in the two oceans. This long-term change of subsurface temperature/salinity may have been caused by change of the wind field over the two oceans during 2001-2012, in turn modifying OHC.展开更多
The mesoscale eddy and internal wave both are phenomena commonly observed in oceans. It is aimed to investigate how the presence of a mesoscale eddy in the ocean affects wave form deformation of the internal solitary ...The mesoscale eddy and internal wave both are phenomena commonly observed in oceans. It is aimed to investigate how the presence of a mesoscale eddy in the ocean affects wave form deformation of the internal solitary wave propagation. An ocean eddy is produced by a quasi-geostrophic model in f-plane, and the one-dimensional nonlinear variable-coefficient extended Korteweg-de Vries (eKdV) equation is used to simulate an internal solitary wave passing through the mesoscale eddy field. The results suggest that the mode structures of the linear internal wave are modified due to the presence of the mesoscale eddy field. A cyclonic eddy and an anticyclonic eddy have different influences on the background environment of the internal solitary wave propagation. The existence of a mesoscale eddy field has almost no prominent impact on the propagation of a smallamplitude internal solitary wave only based on the first mode vertical structure, but the mesoscale eddy background field exerts a considerable influence on the solitary wave propagation if considering high-mode vertical structures. Furthermore, whether an internal solitary wave first passes through anticyclonic eddy or cyclonic eddy, the deformation of wave profiles is different. Many observations of solitary internal waves in the real oceans suggest the formation of the waves. Apart from topography effect, it is shown that the mesoscale eddy background field is also a considerable factor which influences the internal solitary wave propagation and deformation.展开更多
Acoustic Doppler current profiler (ADCP) receives echoes from sound scatterers, then their speed is calcu- lated by the Doppler effect. In the open ocean, most of these backscatterers are from the plankton. The soun...Acoustic Doppler current profiler (ADCP) receives echoes from sound scatterers, then their speed is calcu- lated by the Doppler effect. In the open ocean, most of these backscatterers are from the plankton. The sound scatterers descend down to depth at around dawn, their mean speed is 2.9 cm/s, then they ascend up to the surface layer at around dusk with a mean speed of 2.1 cm/s, in the Luzon Strait. The descending speed is faster, which suggests that this zooplankton population may accelerate its downward migration under the action of the gravity. The vertical distribution of a mean volume backscattering strength (MVB- S) in the nighttime has two peaks, which locate near the upper and lower boundary layers of halocline, respectively. However, the backscatterers only aggregate near the surface layer in the daytime. The diel ver- tical migration (DVM) of sound scatterers has several characteristic patterns, it is stronger in summer, but weaker in winter, and the maximum peak occurs in September. The DVM occurrence is synchronous with the seawater temperature increasing at around dawn and dusk, it may affect the ocean mixing and water stratification,展开更多
The characteristics of internal tides in the upper layer of the Luzon Strait are investigated on the basis of direct-observation current data recorded on April 25 and September 26, 2008 by an acoustic Doppler current ...The characteristics of internal tides in the upper layer of the Luzon Strait are investigated on the basis of direct-observation current data recorded on April 25 and September 26, 2008 by an acoustic Doppler current profiler. Spectral analysis and energy estimation show that the diurnals and semidiurnals carry most of the energy of internal tides. Values of the depth-integrated total energy E for the three frequency bands of diurnal, semidiurnal, and high frequencies are 31, 6.9, and 3.4 kJ·m, respectively. Near-inertial peaks are only present in the baroclinic component. The behavior of typical tidal frequencies (i.e., O1, K1, M2, MK3, and M4) and the near-inertial frequency is basically consistent with linear internal wave theory, which predicts E + (ω)/E (ω)=(ω f) 2 /(ω+f) 2 at depths above 66 m, while not all prominent tidal components coincide well with the relation of the linear internal wave field at other depths. Examinations of depth structures of the baroclinic tides and temporal variations show that the surface tides and internal tides are both of mixed type, having diurnal inequality and spring-neap fortnight periods. The K1 and O1 tides have comparable cross-and along-shelf components, while the M2 and S2 tides propagate toward the shelf in the northern South China Sea as wave beams. The amplitude and phase of internal tides vary with time, but M2 and S2 tides appear to have structures dominated by the first mode, while the K1 and O1 tides resemble second-mode structures. The minor to major axis ratios are close to expected values of f/ω in the thermocline.展开更多
The structure and variability of the currents in the Luzon Strait during spring of 2002 are studied, based on the current measurements at the average position of the mooring station (20°49′57"N, 120°48...The structure and variability of the currents in the Luzon Strait during spring of 2002 are studied, based on the current measurements at the average position of the mooring station (20°49′57"N, 120°48′12"E) from March 17 to April 15, 2002, satellite geostrophic currents in the Luzon Strait, and the spectral analyses, using the maximum entropy method. The subtidal currents at the mooring station show de-creased amplitudes downward with an anti-cyclonic rotation, suggesting that the currents enter and exit the South China Sea in the upper and intermediate layers, respectively. The vertical structure of the currents in the Luzon Strait suggests strongly the sandwiched structure of the LST, even though the bottom part of the profile is not resolved by the observational grid. The spectral analyses show the following periods of significant spectral peaks: (1) the tidal currents variability in the vertical direction; (2) the period about 4-6 d for the two cases of frequency f >0 and f<0 at the 200 and 500 m levels, but at the 800 m level only for the case of f >0; (3) The fluctuation in the period range is about 2-3 days for the two cases of f >0 and f<0 at the 200, 500 and 800 m levels, namely the Luzon Strait currents exhibit significant synoptical variability throughout the water column up to 800 m deep. Both direct current measurements and in situ hydrographic and satellite survey suggest no Kuroshio loop current in the Luzon Strait during the spring of 2002.展开更多
基金The National Basic Research Program(973 Program)of China under contract No.2012CB955601the Special Program for National Basic Research under contract No.2012FY112300+1 种基金the Scientific Research Fund of the Second Institute of Oceanography,State Oceanic Administration under contract Nos JG1207,JG1303 and SOED1307the National Natural Science Foundation of China under contract Nos 41206022,and 41406022
文摘Understanding of the temporal variation of oceanic heat content (OHC) is of fundamental importance to the prediction of climate change and associated global meteorological phenomena. However, OHC characteristics in the Pacific and Indian oceans are not well understood. Based on in situ ocean temperature and salinity profiles mainly from the Argo program, we estimated the upper layer (0-750 m) OHC in the Indo-Pacific Ocean (40°S-40°N, 30°E-80°W). Spatial and temporal variability of OHC and its likely physical mechanisms are also analyzed. Climatic distributions of upper-layer OHC in the Indian and Pacific oceans have a similar saddle pattern in the subtropics, and the highest OHC value was in the northern Arabian Sea. However, OHC variabilities in the two oceans were different. OHC in the Pacific has an east-west see-saw pattern, which does not appear in the Indian Ocean. In the Indian Ocean, the largest change was around 10°S. The most interesting phenomenon is that, there was a long-term shift of OHC in the Indo-Pacific Ocean during 2001-2012. Such variation coincided with modulation of subsurface temperature/salinity. During 2001-2007, there was subsurface cooling (freshening) nearly the entire upper 400 m layer in the western Pacific and warming (salting) in the eastern Pacific. During 2008-2012, the thermocline deepened in the western Pacific but shoaled in the east. In the Indian Ocean, there was only cooling (upper 150 m only) and freshening (almost the entire upper 400 m) during 2001-2007. The thermocline deepened during 2008-2012 in the Indian Ocean. Such change appeared from the equator to off the equator and even to the subtropics (about 20°N/S) in the two oceans. This long-term change of subsurface temperature/salinity may have been caused by change of the wind field over the two oceans during 2001-2012, in turn modifying OHC.
基金The National Basic Research Program of China under contract Nos 2011CB403503 and 2012CB955601the Scientific Research Fund of the Second Institute of Oceanography, the State Oceanic Administration of China under contract Nos JG1009, JT1006 and JT0905
文摘The mesoscale eddy and internal wave both are phenomena commonly observed in oceans. It is aimed to investigate how the presence of a mesoscale eddy in the ocean affects wave form deformation of the internal solitary wave propagation. An ocean eddy is produced by a quasi-geostrophic model in f-plane, and the one-dimensional nonlinear variable-coefficient extended Korteweg-de Vries (eKdV) equation is used to simulate an internal solitary wave passing through the mesoscale eddy field. The results suggest that the mode structures of the linear internal wave are modified due to the presence of the mesoscale eddy field. A cyclonic eddy and an anticyclonic eddy have different influences on the background environment of the internal solitary wave propagation. The existence of a mesoscale eddy field has almost no prominent impact on the propagation of a smallamplitude internal solitary wave only based on the first mode vertical structure, but the mesoscale eddy background field exerts a considerable influence on the solitary wave propagation if considering high-mode vertical structures. Furthermore, whether an internal solitary wave first passes through anticyclonic eddy or cyclonic eddy, the deformation of wave profiles is different. Many observations of solitary internal waves in the real oceans suggest the formation of the waves. Apart from topography effect, it is shown that the mesoscale eddy background field is also a considerable factor which influences the internal solitary wave propagation and deformation.
基金The National Basic Research Program of China under contract Nos 2007CB816003,2011CB403503 and 2012CB955601the National Natural Science Foundation of China under contract Nos 41176020 and 41176021the Scientific Research Fund of the Second Institute of Oceanography,State Oeanic Administration,under contract Nos JT1006 and JG1009
文摘Acoustic Doppler current profiler (ADCP) receives echoes from sound scatterers, then their speed is calcu- lated by the Doppler effect. In the open ocean, most of these backscatterers are from the plankton. The sound scatterers descend down to depth at around dawn, their mean speed is 2.9 cm/s, then they ascend up to the surface layer at around dusk with a mean speed of 2.1 cm/s, in the Luzon Strait. The descending speed is faster, which suggests that this zooplankton population may accelerate its downward migration under the action of the gravity. The vertical distribution of a mean volume backscattering strength (MVB- S) in the nighttime has two peaks, which locate near the upper and lower boundary layers of halocline, respectively. However, the backscatterers only aggregate near the surface layer in the daytime. The diel ver- tical migration (DVM) of sound scatterers has several characteristic patterns, it is stronger in summer, but weaker in winter, and the maximum peak occurs in September. The DVM occurrence is synchronous with the seawater temperature increasing at around dawn and dusk, it may affect the ocean mixing and water stratification,
基金supported by National Basic Research Program of China (Grant Nos. 2007CB816003, 2011CB403503)International Cooperative Project of the Ministry of Science and Technology of China (Grant No. 2006DFB21630)+1 种基金Key Project of the National Natural Science Foundation of China (Grant No. 40520140073)the Scientific Research Fund of the Second Institute of Oceanography, SOA (Grant Nos. JG1009, JG0711 and JT0702)
文摘The characteristics of internal tides in the upper layer of the Luzon Strait are investigated on the basis of direct-observation current data recorded on April 25 and September 26, 2008 by an acoustic Doppler current profiler. Spectral analysis and energy estimation show that the diurnals and semidiurnals carry most of the energy of internal tides. Values of the depth-integrated total energy E for the three frequency bands of diurnal, semidiurnal, and high frequencies are 31, 6.9, and 3.4 kJ·m, respectively. Near-inertial peaks are only present in the baroclinic component. The behavior of typical tidal frequencies (i.e., O1, K1, M2, MK3, and M4) and the near-inertial frequency is basically consistent with linear internal wave theory, which predicts E + (ω)/E (ω)=(ω f) 2 /(ω+f) 2 at depths above 66 m, while not all prominent tidal components coincide well with the relation of the linear internal wave field at other depths. Examinations of depth structures of the baroclinic tides and temporal variations show that the surface tides and internal tides are both of mixed type, having diurnal inequality and spring-neap fortnight periods. The K1 and O1 tides have comparable cross-and along-shelf components, while the M2 and S2 tides propagate toward the shelf in the northern South China Sea as wave beams. The amplitude and phase of internal tides vary with time, but M2 and S2 tides appear to have structures dominated by the first mode, while the K1 and O1 tides resemble second-mode structures. The minor to major axis ratios are close to expected values of f/ω in the thermocline.
基金Supported by National Basic Research Program of China (Grant No. 2007 CB816003)International Cooperative Project of the Ministry of Science and Tech-nology of China (Grant No. 2006DFB21630)+1 种基金National Natural Science Foundation of China (Grant No. 40520140073)Open Fund of the Key Laboratory of Ocean Circulation and Waves, Chinese Academy of Sciences (Grant No. KLOCAW0802)
文摘The structure and variability of the currents in the Luzon Strait during spring of 2002 are studied, based on the current measurements at the average position of the mooring station (20°49′57"N, 120°48′12"E) from March 17 to April 15, 2002, satellite geostrophic currents in the Luzon Strait, and the spectral analyses, using the maximum entropy method. The subtidal currents at the mooring station show de-creased amplitudes downward with an anti-cyclonic rotation, suggesting that the currents enter and exit the South China Sea in the upper and intermediate layers, respectively. The vertical structure of the currents in the Luzon Strait suggests strongly the sandwiched structure of the LST, even though the bottom part of the profile is not resolved by the observational grid. The spectral analyses show the following periods of significant spectral peaks: (1) the tidal currents variability in the vertical direction; (2) the period about 4-6 d for the two cases of frequency f >0 and f<0 at the 200 and 500 m levels, but at the 800 m level only for the case of f >0; (3) The fluctuation in the period range is about 2-3 days for the two cases of f >0 and f<0 at the 200, 500 and 800 m levels, namely the Luzon Strait currents exhibit significant synoptical variability throughout the water column up to 800 m deep. Both direct current measurements and in situ hydrographic and satellite survey suggest no Kuroshio loop current in the Luzon Strait during the spring of 2002.