2010 Vol. 32, No. 4
Display Method:
2010, 32(4): 1-11.
Abstract:
A high resolution numerical model for the tides and tidal currents in the Gulf of Tonkin (GT, also known as Beibu Gulf) and its adjacent waters is developed on the basis of Princeton Ocean Model (POM08),and is used to numerically simulate the four principal tidal constituents, K1, O1, M2 and S2. The main tidal characteristics are presented in detail, followed by an analysis of the influences of Qiongzhou Strait (QzS) on the tidal wave system in the GT from the point of tidal energy dissipation.Diurnal tides are dominant in the GT.For either K1 or O1 constituent, there is a half rotary tidal system near the southern mouth of GT, with the amphidromic points located almost on the coast near Thuan An, Vietnam.The residual current is westward in the QzS, resulting in a water volume transport of 0.034 Sv; after flowing out of the western mouth of QzS, it first turns northward and then southward, forming a anticlockwise curve in the GT.Strong tidal currents are found in two regions: the QzS and the waters off the west coast of Hainan Island, where the tidal energy dissipation rates are the highest in the modal domain.The tidal motion in the GT is maintained by the energy flux from the South China Sea through the southern mouth of the GT.Tidal energy fluxes into the QzS from the western mouth, and nearly all the energy of diurnal tides dissipates away within the strait.The energy dissipation of the four constituents amounts to 3.33 GW in the QzS, accounting for 35% of that consumed in the GT, though the area of QzS is only 2% of that of the GT.The Qiongzhou Strait, as an important area of energy dissipation, plays a significant role in the formation of the tidal waves in the GT.Calculation shows that the bottom boundary dissipation of tidal energy accounts for 83% and 80% of the total dissipation in the GT and QzS, respectively.
A high resolution numerical model for the tides and tidal currents in the Gulf of Tonkin (GT, also known as Beibu Gulf) and its adjacent waters is developed on the basis of Princeton Ocean Model (POM08),and is used to numerically simulate the four principal tidal constituents, K1, O1, M2 and S2. The main tidal characteristics are presented in detail, followed by an analysis of the influences of Qiongzhou Strait (QzS) on the tidal wave system in the GT from the point of tidal energy dissipation.Diurnal tides are dominant in the GT.For either K1 or O1 constituent, there is a half rotary tidal system near the southern mouth of GT, with the amphidromic points located almost on the coast near Thuan An, Vietnam.The residual current is westward in the QzS, resulting in a water volume transport of 0.034 Sv; after flowing out of the western mouth of QzS, it first turns northward and then southward, forming a anticlockwise curve in the GT.Strong tidal currents are found in two regions: the QzS and the waters off the west coast of Hainan Island, where the tidal energy dissipation rates are the highest in the modal domain.The tidal motion in the GT is maintained by the energy flux from the South China Sea through the southern mouth of the GT.Tidal energy fluxes into the QzS from the western mouth, and nearly all the energy of diurnal tides dissipates away within the strait.The energy dissipation of the four constituents amounts to 3.33 GW in the QzS, accounting for 35% of that consumed in the GT, though the area of QzS is only 2% of that of the GT.The Qiongzhou Strait, as an important area of energy dissipation, plays a significant role in the formation of the tidal waves in the GT.Calculation shows that the bottom boundary dissipation of tidal energy accounts for 83% and 80% of the total dissipation in the GT and QzS, respectively.
2010, 32(4): 12-23.
Abstract:
Based on the datasets from NCEP and the South China Sea (SCS) air-sea flux measurement which was carried out from April, 2008, the air-sea fluxes were calculated with COARE3.0 algorithm, and the characteristics of the weather and how the air-sea fluxes varied with the variations of atmosphere and ocean elements before and during the onset of the SCS monsoon were discussed.The results indicated that, the onset of the SCS monsoon in the 2008 appeared firstly in the southern part of SCS at early May, and then owing to influence of a tropical cyclone the onset of monsoon in the northern part of SCS was remitted to 18th May.Influence of the onset of monsoon and tropical cyclone activity on wind speed and air-sea fluxes was remarkable.By comparison, influence of the tropical cyclone activity on air-sea fluxes was stronger.Before the tropical cyclone, the latent heat flux and sensible heat flux and momentum flux were quite low.During the tropical cyclone and the onset of SCS monsoon, the latent heat flux and momentum flux increased greatly because of the strong wind while the sensible heat flux increased in the days when it rained.The momentum flux maximized during the tropical cyclone and was twice bigger than that before the onset of SCS monsoon.The latent heat flux was sixteen times as much as the sensible heat flux during the entire observation.In different types of weather, the latent heat flux had similar diurnal distribution while the sensible heat flux varied a lot.Besides, the close correlation between the transfer coefficients and wind speed was found.
Based on the datasets from NCEP and the South China Sea (SCS) air-sea flux measurement which was carried out from April, 2008, the air-sea fluxes were calculated with COARE3.0 algorithm, and the characteristics of the weather and how the air-sea fluxes varied with the variations of atmosphere and ocean elements before and during the onset of the SCS monsoon were discussed.The results indicated that, the onset of the SCS monsoon in the 2008 appeared firstly in the southern part of SCS at early May, and then owing to influence of a tropical cyclone the onset of monsoon in the northern part of SCS was remitted to 18th May.Influence of the onset of monsoon and tropical cyclone activity on wind speed and air-sea fluxes was remarkable.By comparison, influence of the tropical cyclone activity on air-sea fluxes was stronger.Before the tropical cyclone, the latent heat flux and sensible heat flux and momentum flux were quite low.During the tropical cyclone and the onset of SCS monsoon, the latent heat flux and momentum flux increased greatly because of the strong wind while the sensible heat flux increased in the days when it rained.The momentum flux maximized during the tropical cyclone and was twice bigger than that before the onset of SCS monsoon.The latent heat flux was sixteen times as much as the sensible heat flux during the entire observation.In different types of weather, the latent heat flux had similar diurnal distribution while the sensible heat flux varied a lot.Besides, the close correlation between the transfer coefficients and wind speed was found.
2010, 32(4): 24-31.
Abstract:
Based on the monthly HadiSST SSTA(sea surface temperature anomaly) in recent 100 years (from 1903 to 2002), the spatial and temporal variation characteristics of global SSTA are analyzed by using the method of Empirical Orthogonal Function (EOF),the first main mode of global SSTA and other joint modes between different oceans are respectively obtained. It is shown that the maximum changes of SSTA appear in equatorial eastern Pacific, Gulf Stream zone in northwestern Atlantic and Kuroshio extension zone in north Pacific; ENSO in tropical Pacific is the first main mode with periods of 2~7 years; the second main mode and third main mode are joint modes between different oceans with an interdecadal period of about 70 years. The second mode is a Pacific-Atlantic double dipole mode with one out-of-phase dipole in north Pacific and north Atlantic, the other in tropical Pacific and tropical Atlantic. The third mode is a North Pacific-North Atlantic-Southern Ocean mode with out-of-phase between northern and southern hemispheres. The forth mode reflects local ocean-atmosphere interaction patterns in different zones and the time series in this mode presents interannual periods of 1~4 years and an interdecadal period of about 9 years .
Based on the monthly HadiSST SSTA(sea surface temperature anomaly) in recent 100 years (from 1903 to 2002), the spatial and temporal variation characteristics of global SSTA are analyzed by using the method of Empirical Orthogonal Function (EOF),the first main mode of global SSTA and other joint modes between different oceans are respectively obtained. It is shown that the maximum changes of SSTA appear in equatorial eastern Pacific, Gulf Stream zone in northwestern Atlantic and Kuroshio extension zone in north Pacific; ENSO in tropical Pacific is the first main mode with periods of 2~7 years; the second main mode and third main mode are joint modes between different oceans with an interdecadal period of about 70 years. The second mode is a Pacific-Atlantic double dipole mode with one out-of-phase dipole in north Pacific and north Atlantic, the other in tropical Pacific and tropical Atlantic. The third mode is a North Pacific-North Atlantic-Southern Ocean mode with out-of-phase between northern and southern hemispheres. The forth mode reflects local ocean-atmosphere interaction patterns in different zones and the time series in this mode presents interannual periods of 1~4 years and an interdecadal period of about 9 years .
2010, 32(4): 32-40.
Abstract:
By using tropical cyclone data from China Meteorological Administration (CMA) and the ERA reanalysis data for the period of 1958—2001, a possible mechanism for the role of latent heat flux variation on the activities of TCs in the western North Pacific(WNP, including South China Sea) has been proposed. There exist significant decreasing trends in both the frequency of TCs in WNP(including SCS) and the latent heat flux in the key region-central subtropical North Pacific. Diagnostics suggest that latent heat flux in the key region may through a chain of latent heat flux-westward water vapor transportation at lower troposphere-water vapor converging, ascending and then condensing over the WNP(including SCS)-releasing latent heat-changing the atmospheric environment (including relative humidity in the middle troposphere, vorticity in the upper and lower troposphere, divergence in the upper and lower troposphere)-ultimately control the activities of WNP(including SCS) TCs. Modeling study by using SAMIL model further confirms the diagnostics results above and reveals that the activities of WNP TCs are very sensitive to the ocean-atmospheric interaction in the key region, while the activities of SCS TCs are less sensitive. It can be concluded at least tentatively that during the past more than 40 years the decreasing trend in the latent heat flux in the central subtropical North Pacific is one of the main reasons that cause the decreasing trend in the frequency of TCs in WNP(including SCS).
By using tropical cyclone data from China Meteorological Administration (CMA) and the ERA reanalysis data for the period of 1958—2001, a possible mechanism for the role of latent heat flux variation on the activities of TCs in the western North Pacific(WNP, including South China Sea) has been proposed. There exist significant decreasing trends in both the frequency of TCs in WNP(including SCS) and the latent heat flux in the key region-central subtropical North Pacific. Diagnostics suggest that latent heat flux in the key region may through a chain of latent heat flux-westward water vapor transportation at lower troposphere-water vapor converging, ascending and then condensing over the WNP(including SCS)-releasing latent heat-changing the atmospheric environment (including relative humidity in the middle troposphere, vorticity in the upper and lower troposphere, divergence in the upper and lower troposphere)-ultimately control the activities of WNP(including SCS) TCs. Modeling study by using SAMIL model further confirms the diagnostics results above and reveals that the activities of WNP TCs are very sensitive to the ocean-atmospheric interaction in the key region, while the activities of SCS TCs are less sensitive. It can be concluded at least tentatively that during the past more than 40 years the decreasing trend in the latent heat flux in the central subtropical North Pacific is one of the main reasons that cause the decreasing trend in the frequency of TCs in WNP(including SCS).
2010, 32(4): 41-50.
Abstract:
The mid-Holocene (6 000 years before present) North Atlantic Oscillation (NAO) is studied from the results of four ocean-atmosphere coupled models in the Paleclimate Modeling Intercomparison Project Phase 2 (PMIP2). Using winter North Atlantic sea level pressure (SLP), this paper analyze sea level pressure changes in the North Atlantic during the mid-Holocene compared to pre-industrial (1750 AD) control runs and calculate the NAO index of present and mid-Holocene. There is considerable variation in mean SLP (DJF) between 6 ka and 0 ka across models. Features common to all models include a stronger subtropical high pressure center, a deeper Icelandic low and a tendency toward an increased latitude gradient in mean SLP, and therefore a more positive NAO regime during the mid-Holocene compared to present day. The principal structural of NAO was captured well from all of the models through Empirical orthogonal function (EOF) analyses of North Atlantic sea level pressure in winter time (DJF). There is a robust cross-model change in the variance of the NAO time series. In NAO positive phase, the time lasts 10%~30% longer during the mid-Holocene,especially 29.3% longer in MIROC3.2. Although the amplitude of NAO variability show no greater during the mid-Holocene, it can still be found a more positive NAO from all models. Proxy based reconstructions of the NAO indicate a more positive NAO regime during the Mid-Holocene compared to present day. Simulated NAO variability corresponds fairly closed to proxy-based NAO reconstructions. The Multi-Taper Method of Spectrum Analysis shows that there are three- to five- year quasi-cycles in the NAO index at present and three- year quasi-cycles during the mid-Holocene. NAO plays an important role in the Asian winter warming during the mid-Holocene. The positive SST anomalies in mid-latitude North Atlantic might lead to a more positive NAO during the Mid-Holocene.
The mid-Holocene (6 000 years before present) North Atlantic Oscillation (NAO) is studied from the results of four ocean-atmosphere coupled models in the Paleclimate Modeling Intercomparison Project Phase 2 (PMIP2). Using winter North Atlantic sea level pressure (SLP), this paper analyze sea level pressure changes in the North Atlantic during the mid-Holocene compared to pre-industrial (1750 AD) control runs and calculate the NAO index of present and mid-Holocene. There is considerable variation in mean SLP (DJF) between 6 ka and 0 ka across models. Features common to all models include a stronger subtropical high pressure center, a deeper Icelandic low and a tendency toward an increased latitude gradient in mean SLP, and therefore a more positive NAO regime during the mid-Holocene compared to present day. The principal structural of NAO was captured well from all of the models through Empirical orthogonal function (EOF) analyses of North Atlantic sea level pressure in winter time (DJF). There is a robust cross-model change in the variance of the NAO time series. In NAO positive phase, the time lasts 10%~30% longer during the mid-Holocene,especially 29.3% longer in MIROC3.2. Although the amplitude of NAO variability show no greater during the mid-Holocene, it can still be found a more positive NAO from all models. Proxy based reconstructions of the NAO indicate a more positive NAO regime during the Mid-Holocene compared to present day. Simulated NAO variability corresponds fairly closed to proxy-based NAO reconstructions. The Multi-Taper Method of Spectrum Analysis shows that there are three- to five- year quasi-cycles in the NAO index at present and three- year quasi-cycles during the mid-Holocene. NAO plays an important role in the Asian winter warming during the mid-Holocene. The positive SST anomalies in mid-latitude North Atlantic might lead to a more positive NAO during the Mid-Holocene.
2010, 32(4): 51-61.
Abstract:
A typical polar vortex circulation is established and developed during the period of 2003 September 3 to 14, on which the Xuelong exploration ship entered the Chukchi Sea of the Arctic Ocean for the Second Chinese Arctic Research Expedition. Most of the previous studies focused on the mean circulation structure and seasonal variation, this case, however, provides a necessary condition for studying its transient circulation situation and structure. In this paper, NCEP reanalysis data and the expedition observations are used for the synoptic analysis, including the development of the polar vortex, the circulation structures in the stratosphere, troposphere, and their relationship, together with the satellite remote sensing and meteorological data analysis from Xuelong exploration ship. It is found that the establishment and development of the polar vortex during the 2003 expedition period is characterized by a typical seasonal circulation transition from summertime to wintertime. It first appears in the stratosphere, and then transmits downward to the troposphere. In the stratosphere the vortex shifts westward and strengthens, while in the troposphere it moves eastward and southward.
A typical polar vortex circulation is established and developed during the period of 2003 September 3 to 14, on which the Xuelong exploration ship entered the Chukchi Sea of the Arctic Ocean for the Second Chinese Arctic Research Expedition. Most of the previous studies focused on the mean circulation structure and seasonal variation, this case, however, provides a necessary condition for studying its transient circulation situation and structure. In this paper, NCEP reanalysis data and the expedition observations are used for the synoptic analysis, including the development of the polar vortex, the circulation structures in the stratosphere, troposphere, and their relationship, together with the satellite remote sensing and meteorological data analysis from Xuelong exploration ship. It is found that the establishment and development of the polar vortex during the 2003 expedition period is characterized by a typical seasonal circulation transition from summertime to wintertime. It first appears in the stratosphere, and then transmits downward to the troposphere. In the stratosphere the vortex shifts westward and strengthens, while in the troposphere it moves eastward and southward.
2010, 32(4): 62-76.
Abstract:
Heavy metals fluxes into the sea and their sources since of the 1980s have been collected and analyzed in the sea area of the East China Sea interferenced by terrigenous matter (SAECSIT). And based on a heavy metal transference-translation model in multimedia sea environment, the environmental capacity in the SAECSIT is estimated for the first time. Since the begining of the 1980s, changing trend of the total fluxes of contamination Cu, Pb, Zn and Cd into the SAECSIT basically has showed inverse "U" pattern, conforming with "environmental Kuznets curves" on the whole. The tatal fluxes of them increased to the maximum values in the 1990s, and in present still were higher than those at the beginning of the 1980s. For the main source of Cu, Pb, Zn and Cd into the SAECSIT, the terringenous discharge, especially from rivers, is overwhelmingly dominant, being up to 88.0% on average; sewage takes second place, being 7.5% approximately; the sediment from atmosphere is the smallest, being 5.5% on average. The fluxes from the Changjiang drainage area are the highest, being up to 92.4% of the total fluxes into the SAECSIT on average, those from the Qiantang River being 3.9% approximately and those from the Minjiang River being 3.7% on average. The environmental capacities of Cu, Pb, Zn and Cd in the SAECSIT are computed to be approximately 17.00, 4.70, 113.1, 0.71 kt/a. The present gross discharge fluxes of Pb, Zn and Cd in SAECSIT do not exceed their environmental capacities, but the flux of Cu is 8% higher than its environmental capacity.
Heavy metals fluxes into the sea and their sources since of the 1980s have been collected and analyzed in the sea area of the East China Sea interferenced by terrigenous matter (SAECSIT). And based on a heavy metal transference-translation model in multimedia sea environment, the environmental capacity in the SAECSIT is estimated for the first time. Since the begining of the 1980s, changing trend of the total fluxes of contamination Cu, Pb, Zn and Cd into the SAECSIT basically has showed inverse "U" pattern, conforming with "environmental Kuznets curves" on the whole. The tatal fluxes of them increased to the maximum values in the 1990s, and in present still were higher than those at the beginning of the 1980s. For the main source of Cu, Pb, Zn and Cd into the SAECSIT, the terringenous discharge, especially from rivers, is overwhelmingly dominant, being up to 88.0% on average; sewage takes second place, being 7.5% approximately; the sediment from atmosphere is the smallest, being 5.5% on average. The fluxes from the Changjiang drainage area are the highest, being up to 92.4% of the total fluxes into the SAECSIT on average, those from the Qiantang River being 3.9% approximately and those from the Minjiang River being 3.7% on average. The environmental capacities of Cu, Pb, Zn and Cd in the SAECSIT are computed to be approximately 17.00, 4.70, 113.1, 0.71 kt/a. The present gross discharge fluxes of Pb, Zn and Cd in SAECSIT do not exceed their environmental capacities, but the flux of Cu is 8% higher than its environmental capacity.
2010, 32(4): 77-87.
Abstract:
The spatial variations in nitrate (NO-3), nitrite (NO-2) and ammonium (NH+4) concentrations in the Changjiang Estuary and the adjacent East China Sea were described on the basis of the summer cruise in 2006. NO-3 concentrations decreased along a salinity gradient. Owing to the input of the sewage from Shanghai City NO-2 and NH-4 concentrations were very high (up to 8.64, 19.81 μmol/dm3 respectively) in the Changjiang Estuaxy area and decreased seaward. Generally NO-3 and NH+4 concentrations were significantly correlated with salinity, with the coefficient (r2) of 0.815 and 0.255 respectively, suggesting that these two nutrients behaved nearly conservatively, while NO-2 did not behave conservatively (r2=0.074). Theoretical dilution line (TDL) was obtained by assuming river and ocean end-members. NO-3, NO-2 and NH+4 concentrations were above values expected for a conservative mixing relationship with salinity at the freshwater end member due to high nitrogen input from the sewage effluence, and in deep water at the oceanic stations because of the decomposition of the organic matter. In contrast, at the salinity plume with high dissolved oxygen (DO) concentrations, the surface NO-3 concentrations were below values expected for the conservative mixing by 1~19 mol/dm3, as a result of high primary production in the euphotic zone, where NO-2 and NH+4 concentrations were also negatively deviated to various extents. In waters with the highest turbidity in the Changjiang Estuary, NH+4 was removed due to the adsorption of suspended matter. Overall, NO-3, NO-2 and NH+4 concentrations at the surface at the oceanic stations deviated from the TDL to less extent, while their concentrations at the bottom were generally beyond values expected for the TDL because the organic matter from the photic zone decomposed and nutrients regenerated.
The spatial variations in nitrate (NO-3), nitrite (NO-2) and ammonium (NH+4) concentrations in the Changjiang Estuary and the adjacent East China Sea were described on the basis of the summer cruise in 2006. NO-3 concentrations decreased along a salinity gradient. Owing to the input of the sewage from Shanghai City NO-2 and NH-4 concentrations were very high (up to 8.64, 19.81 μmol/dm3 respectively) in the Changjiang Estuaxy area and decreased seaward. Generally NO-3 and NH+4 concentrations were significantly correlated with salinity, with the coefficient (r2) of 0.815 and 0.255 respectively, suggesting that these two nutrients behaved nearly conservatively, while NO-2 did not behave conservatively (r2=0.074). Theoretical dilution line (TDL) was obtained by assuming river and ocean end-members. NO-3, NO-2 and NH+4 concentrations were above values expected for a conservative mixing relationship with salinity at the freshwater end member due to high nitrogen input from the sewage effluence, and in deep water at the oceanic stations because of the decomposition of the organic matter. In contrast, at the salinity plume with high dissolved oxygen (DO) concentrations, the surface NO-3 concentrations were below values expected for the conservative mixing by 1~19 mol/dm3, as a result of high primary production in the euphotic zone, where NO-2 and NH+4 concentrations were also negatively deviated to various extents. In waters with the highest turbidity in the Changjiang Estuary, NH+4 was removed due to the adsorption of suspended matter. Overall, NO-3, NO-2 and NH+4 concentrations at the surface at the oceanic stations deviated from the TDL to less extent, while their concentrations at the bottom were generally beyond values expected for the TDL because the organic matter from the photic zone decomposed and nutrients regenerated.
2010, 32(4): 88-97.
Abstract:
Surface waters were collected from the Prydz Bay of Antarctica for measurements of 226Ra activities during the 22nd China’s antarctic research expedition (from December 2005 to January 2006).226Ra in large volume waters was extracted by Mn-fibers and measured by a 222Rn emanation method.Results show that 226Ra activity in the Prydz Bay ranges from 0.92 to 2.09 Bq/m3 with an average of 1.61 Bq/m3.High contents of 226Ra were observed at deep open-ocean stations, which induced an offshore increase of 226Ra activity.This unique distribution pattern in the Prydz Bay was ascribed to the influence of water masses with different 226Ra signals.Based on the relationship between 226Ra activity and salinity, three water masses were identified: (1) the antarctic summer surface water (AASSW) with a characteristics of high salinity and high content of 226Ra; (2) the ice-melted water (IMW) with a characteristics of low salinity and low content of 226Ra; and (3) the Prydz Bay deep water (PDW) with a characteristics of high salinity and intermediate content of 226Ra.226Ra in the Prydz Bay deep water was assumed to be maintained only by the supply from the seabed sediments.The fractions of the above three water masses were estimated by mass balance calculation of salinity and 226Ra activity.Results show that the AASSW fractions decrease from the deep open ocean to inshore, while the IMW and PDW fractions increase.The maximum fractions of the IMW and the PDW occur in the eastern and the western regions along the front of the Amery ice shelf, respectively, testifying the major flow into the shelf occurs at the eastern end and exits from the west.
Surface waters were collected from the Prydz Bay of Antarctica for measurements of 226Ra activities during the 22nd China’s antarctic research expedition (from December 2005 to January 2006).226Ra in large volume waters was extracted by Mn-fibers and measured by a 222Rn emanation method.Results show that 226Ra activity in the Prydz Bay ranges from 0.92 to 2.09 Bq/m3 with an average of 1.61 Bq/m3.High contents of 226Ra were observed at deep open-ocean stations, which induced an offshore increase of 226Ra activity.This unique distribution pattern in the Prydz Bay was ascribed to the influence of water masses with different 226Ra signals.Based on the relationship between 226Ra activity and salinity, three water masses were identified: (1) the antarctic summer surface water (AASSW) with a characteristics of high salinity and high content of 226Ra; (2) the ice-melted water (IMW) with a characteristics of low salinity and low content of 226Ra; and (3) the Prydz Bay deep water (PDW) with a characteristics of high salinity and intermediate content of 226Ra.226Ra in the Prydz Bay deep water was assumed to be maintained only by the supply from the seabed sediments.The fractions of the above three water masses were estimated by mass balance calculation of salinity and 226Ra activity.Results show that the AASSW fractions decrease from the deep open ocean to inshore, while the IMW and PDW fractions increase.The maximum fractions of the IMW and the PDW occur in the eastern and the western regions along the front of the Amery ice shelf, respectively, testifying the major flow into the shelf occurs at the eastern end and exits from the west.
2010, 32(4): 98-109.
Abstract:
The paleoproductivity and paleoredox history in the Sea of Japan since 48 ka have been reconstructed using element geochemical data, and factors controlling the change are determined. The mass accumulations of multiproxies show that the paleoprodutivity has varied greatly since 48 ka. At 48~18 ka, a relative lower sea-level and a limited water mass exchange resulted in the lower paleoproductivity. At 18~11 ka, the higher paleoproductivity was resulted from the rich-nutrients water mass (the Oyasio and the East China Sea coastal water) inflowing into the Sea of Japan with relative sea-level rise, and the maximum value was observed at 12.6~11.5 ka. In the Holocene, the Tsushima Warm Current was a main factor that controlled the distribution of paleoproductivity, and since 5 ka the paleoproductivity had remained relative stability.the proxies about the paleoredox (TOC, molybdenum, uranium and manganese , the ratio of carbon to sulfur content, authigenic uranium and molybdenum contents) indicate that at 12~9 ka, the bottom water is anoxic. Both enhanced paleoproductivity and restricted bottom-water advection triggered the bottom water anoxic and it was also related to the global climate change and the sea-level change.
The paleoproductivity and paleoredox history in the Sea of Japan since 48 ka have been reconstructed using element geochemical data, and factors controlling the change are determined. The mass accumulations of multiproxies show that the paleoprodutivity has varied greatly since 48 ka. At 48~18 ka, a relative lower sea-level and a limited water mass exchange resulted in the lower paleoproductivity. At 18~11 ka, the higher paleoproductivity was resulted from the rich-nutrients water mass (the Oyasio and the East China Sea coastal water) inflowing into the Sea of Japan with relative sea-level rise, and the maximum value was observed at 12.6~11.5 ka. In the Holocene, the Tsushima Warm Current was a main factor that controlled the distribution of paleoproductivity, and since 5 ka the paleoproductivity had remained relative stability.the proxies about the paleoredox (TOC, molybdenum, uranium and manganese , the ratio of carbon to sulfur content, authigenic uranium and molybdenum contents) indicate that at 12~9 ka, the bottom water is anoxic. Both enhanced paleoproductivity and restricted bottom-water advection triggered the bottom water anoxic and it was also related to the global climate change and the sea-level change.
2010, 32(4): 110-117.
Abstract:
The source information of sediments was preserved in detrital zircons,which could sufficiently interpret the provenance of sediments uranium-lead ages and trace elements in detrital zircons from the Minjiang and Jiulong Estuaries was analyzed by in situ laser ablation-multiple collector-inductively coupled plasma mass spectrometry (LA-MC-ICP-MS). In most zircons the ratio of thorium content to uranium is higher than 0.1,indicating that zorcons have HREE-enriched feature with the positive anomaly of cerium content and the negative anomaly of europium content in chondrite-normalized REE patterns,a feature of magmatic origin. The uranium-lead ages of zircon from the Minjiang and Jiulong Estuaries can be divided into three groups: Indosinian (ca.236 Ma),Early Yanshanian (ca.155 Ma) and Late Yanshanian (ca.110 Ma). These age ranges are consistent with the ages of granitic rocks outcropped in the middle and lower reaches of the rivers. However, the uranium-lead ages of zircon from the Minjiang Estuary show distinctly Caledonian (ca.465 Ma) and Precambrian ages (553~2765Ma),which are possibly derived from the Caledonian and Precambrian rocks from upstream. In regard of similar age ranges of detrital zircons from the Minjiang Estuary and monazite from beach sands of the western Taiwan Island(Miaoli—Hsinchu,Chiayi—Tainan),the sediments of the western Taiwan Island are very likely derived from the Minjiang River.
The source information of sediments was preserved in detrital zircons,which could sufficiently interpret the provenance of sediments uranium-lead ages and trace elements in detrital zircons from the Minjiang and Jiulong Estuaries was analyzed by in situ laser ablation-multiple collector-inductively coupled plasma mass spectrometry (LA-MC-ICP-MS). In most zircons the ratio of thorium content to uranium is higher than 0.1,indicating that zorcons have HREE-enriched feature with the positive anomaly of cerium content and the negative anomaly of europium content in chondrite-normalized REE patterns,a feature of magmatic origin. The uranium-lead ages of zircon from the Minjiang and Jiulong Estuaries can be divided into three groups: Indosinian (ca.236 Ma),Early Yanshanian (ca.155 Ma) and Late Yanshanian (ca.110 Ma). These age ranges are consistent with the ages of granitic rocks outcropped in the middle and lower reaches of the rivers. However, the uranium-lead ages of zircon from the Minjiang Estuary show distinctly Caledonian (ca.465 Ma) and Precambrian ages (553~2765Ma),which are possibly derived from the Caledonian and Precambrian rocks from upstream. In regard of similar age ranges of detrital zircons from the Minjiang Estuary and monazite from beach sands of the western Taiwan Island(Miaoli—Hsinchu,Chiayi—Tainan),the sediments of the western Taiwan Island are very likely derived from the Minjiang River.
2010, 32(4): 118-128.
Abstract:
Xisha area subsided along with the seafloor spreading of the South China Sea, carbonate platform and different types of reef began developed from Early Miocene in this area. Based on the seismic analysis, reefs in Xisha area show high-amplitude moundy continuous reflection at the top and the bottom, chaotic reflection inside the reef, carbonate platform shows high-amplitude continuous sub-parallel reflection at the top and a partly obscure bottom boundary, the internal reflection shows high-amplitude reflection interbedded with weak-amplitude reflection. Based on the stratigraphic sequence analysis in Xisha area and the seismic interpretation, the development of Xisha carbonate platforms was mainly controlled by the basement structure at the early stage and then mainly controlled by the relative sea-level fluctuation, so Xisha carbonate platforms experienced several development stages such as initial establishment stage, aggradation stage, exposure stage and flooding stage. The complicated development process makes the carbonate reservoir to have favorable reservoir properties and hydrocarbon potential.
Xisha area subsided along with the seafloor spreading of the South China Sea, carbonate platform and different types of reef began developed from Early Miocene in this area. Based on the seismic analysis, reefs in Xisha area show high-amplitude moundy continuous reflection at the top and the bottom, chaotic reflection inside the reef, carbonate platform shows high-amplitude continuous sub-parallel reflection at the top and a partly obscure bottom boundary, the internal reflection shows high-amplitude reflection interbedded with weak-amplitude reflection. Based on the stratigraphic sequence analysis in Xisha area and the seismic interpretation, the development of Xisha carbonate platforms was mainly controlled by the basement structure at the early stage and then mainly controlled by the relative sea-level fluctuation, so Xisha carbonate platforms experienced several development stages such as initial establishment stage, aggradation stage, exposure stage and flooding stage. The complicated development process makes the carbonate reservoir to have favorable reservoir properties and hydrocarbon potential.
2010, 32(4): 129-138.
Abstract:
The grain-size of suspended particulate matter in the Huanghe Estuary and its adjacent area was investigated with an in situ laser grain-size analyzer in November 2006. The grain-size parameters and distribution patterns vary strongly in the horizontal and vertical directions. The results show that (1) the mean grain-size of the suspended particulate matter ranges from 3.00Φ to 6.41Φ, with an average value of 4.66Φ; (2) the grain-size distribution patterns of the suspended sediment include three types, e. g., monomode, bimode and trimode; (3) C-M patterns suggest that transportation forms of the suspended particulate matter not only include suspended transportation, but bed load transportation. The bed load transportation mainly appeared at the bottom layer. The grain-size pattern and distribution were basically controlled by the Huanghe discharge, hydrodynamics, surface sediment type, and chemical and biological conditions.
The grain-size of suspended particulate matter in the Huanghe Estuary and its adjacent area was investigated with an in situ laser grain-size analyzer in November 2006. The grain-size parameters and distribution patterns vary strongly in the horizontal and vertical directions. The results show that (1) the mean grain-size of the suspended particulate matter ranges from 3.00Φ to 6.41Φ, with an average value of 4.66Φ; (2) the grain-size distribution patterns of the suspended sediment include three types, e. g., monomode, bimode and trimode; (3) C-M patterns suggest that transportation forms of the suspended particulate matter not only include suspended transportation, but bed load transportation. The bed load transportation mainly appeared at the bottom layer. The grain-size pattern and distribution were basically controlled by the Huanghe discharge, hydrodynamics, surface sediment type, and chemical and biological conditions.
Discussion on grain-size characteristics of seafloor sediment and transport pattern in the Bohai Sea
2010, 32(4): 139-147.
Abstract:
The grain-size distribution and transport pattern of seafloor sediment collected from the Bohai Sea were studied using grain-size data and Gao-Collins grain-size trend analysis method. The results show that coarse-grained sediment is mainly distributed on Liaodong and Bozhong shoals and occurs occasionally near the Luanhe and Huanghe mouths; fine-grained sediment mainly covers the central and southern part of Bohai Gulf and extends farther to the west of Liaodong Gulf. The fine-grained sediment is better sorted with lower skewness compared with the coarse-grained sediment; the fine-grained sediment area is considered to be a modern depositional center of the Bohai Sea and the sediment outside the center displays a net transport trend toward it. The distribution and transport pattern of sediment in the study area are proposed to be controlled by tidal currents and circulations.
The grain-size distribution and transport pattern of seafloor sediment collected from the Bohai Sea were studied using grain-size data and Gao-Collins grain-size trend analysis method. The results show that coarse-grained sediment is mainly distributed on Liaodong and Bozhong shoals and occurs occasionally near the Luanhe and Huanghe mouths; fine-grained sediment mainly covers the central and southern part of Bohai Gulf and extends farther to the west of Liaodong Gulf. The fine-grained sediment is better sorted with lower skewness compared with the coarse-grained sediment; the fine-grained sediment area is considered to be a modern depositional center of the Bohai Sea and the sediment outside the center displays a net transport trend toward it. The distribution and transport pattern of sediment in the study area are proposed to be controlled by tidal currents and circulations.
2010, 32(4): 148-154.
Abstract:
Trichodesmium abundances were studied in the tropical and subtropical Pacific Ocean and the southern Indian Ocean from May 2008 to February 2009. The study area was divided into five districts including the northwest subtropical Pacific (NWSP), the central tropical Pacific (CTP), the eastern tropical Pacific (ETP), the tropical southeast Asia sea areas(TSAS) and the southern Indian Ocean (SIO). Results show that Trichodesmium trichome abundances vary between 0 and 130 103 m-3. The average abundances of Trichodesmium in the TSAS and the NWSP are 33.3 103 m-3(5.75×103~130×103 m-3) and 25.2×103 m-3(2×103~81.3×103 m-3) respectively, which are higher than in the CTP, the ETP and the SIO, where average abundances of Trichodesmium are 1.76 103 m-3(0~10.3×103 m3), 0.87×103 m3(0~7.75 103 m-3) and 1.52×103 m-3(0~8 103 m-3) respectively. No correlation between the surface water temperature and Trichodesmium abundance were found, however, iron flux from atmosphere seemed to be a hint to Trichodesmium abundances, which need to be studied further. Total chlorophyll a(chl a)concentration had a different distribution characteristics from Trichodesmium abundances, which was lower in the NWSP and the SIO but higher in the CTP, the ETP and the TSAS. The phytoplankton community was composed mostly of picophytoplankton, chl a in the 0.2~2 μm size fraction accounted for more than 60% of the total chl a, while Trichodesmium chl a made up a very small proportion of total chl a. N2-fixation rates of Trichodesmium are estimated, N2-fixation by Trichodesmium is greeter than 30% new nitrogen sources in the NWSP but much lower in the CTP and the ETP.
Trichodesmium abundances were studied in the tropical and subtropical Pacific Ocean and the southern Indian Ocean from May 2008 to February 2009. The study area was divided into five districts including the northwest subtropical Pacific (NWSP), the central tropical Pacific (CTP), the eastern tropical Pacific (ETP), the tropical southeast Asia sea areas(TSAS) and the southern Indian Ocean (SIO). Results show that Trichodesmium trichome abundances vary between 0 and 130 103 m-3. The average abundances of Trichodesmium in the TSAS and the NWSP are 33.3 103 m-3(5.75×103~130×103 m-3) and 25.2×103 m-3(2×103~81.3×103 m-3) respectively, which are higher than in the CTP, the ETP and the SIO, where average abundances of Trichodesmium are 1.76 103 m-3(0~10.3×103 m3), 0.87×103 m3(0~7.75 103 m-3) and 1.52×103 m-3(0~8 103 m-3) respectively. No correlation between the surface water temperature and Trichodesmium abundance were found, however, iron flux from atmosphere seemed to be a hint to Trichodesmium abundances, which need to be studied further. Total chlorophyll a(chl a)concentration had a different distribution characteristics from Trichodesmium abundances, which was lower in the NWSP and the SIO but higher in the CTP, the ETP and the TSAS. The phytoplankton community was composed mostly of picophytoplankton, chl a in the 0.2~2 μm size fraction accounted for more than 60% of the total chl a, while Trichodesmium chl a made up a very small proportion of total chl a. N2-fixation rates of Trichodesmium are estimated, N2-fixation by Trichodesmium is greeter than 30% new nitrogen sources in the NWSP but much lower in the CTP and the ETP.
2010, 32(4): 155-167.
Abstract:
The abundance and distribution characteristics of picophytoplankton in the southern Huanghai Sea were investigated by flow cytometry (FCM) during August 2008. The results show that the average abundance and maximum abundance of photosynthetic picoeukaryotes are 1.9×103 and 2.4×104 cells/mL respectively, while the average abundance and maximum abundance of Synechococcus are 5.3×104 and 5.1×105 cells/mL respectively.From coastal to central broad waters, the distribution of picophytoplankton varied significantly with the changes of environmental factors.The high abundance of picophytoplankton was observed in coastal and estuarine areas, and much lower abundance was recorded in the central broad waters.The relationships between the abundance of picophytoplankton and the environmental factors were also discussed. And the Huanghai Sea Cold Water Mass and the Changjiang diluted water were identified to be the major factors influencing the distribution of picophytoplankton in the study area.
The abundance and distribution characteristics of picophytoplankton in the southern Huanghai Sea were investigated by flow cytometry (FCM) during August 2008. The results show that the average abundance and maximum abundance of photosynthetic picoeukaryotes are 1.9×103 and 2.4×104 cells/mL respectively, while the average abundance and maximum abundance of Synechococcus are 5.3×104 and 5.1×105 cells/mL respectively.From coastal to central broad waters, the distribution of picophytoplankton varied significantly with the changes of environmental factors.The high abundance of picophytoplankton was observed in coastal and estuarine areas, and much lower abundance was recorded in the central broad waters.The relationships between the abundance of picophytoplankton and the environmental factors were also discussed. And the Huanghai Sea Cold Water Mass and the Changjiang diluted water were identified to be the major factors influencing the distribution of picophytoplankton in the study area.
2010, 32(4): 168-176.
Abstract:
Samplings of chlorophyll a (Chl a) concentration are analyzed based on historical cruises data for about 10 a in the South China Sea (SCS), including the northern SCS, the Nansha Islands and other sea areas in the SCS. The profiles of Chl a concentration are classified by the values within the surface layer, to develop a parameterization shape of Chl a concentration vertical profiles according to a generalized Gaussian model (adding a linear decline with a slope starting from the surface value). The modeled Chl a concentration vertical profiles show a normal distribution with a slightly declining slope, and fit well with the in situ Chl a concentration. The max value appears in subsurface layer, as the surface Chl a concentration is low, which represents deep-sea basin waters(Case I); while the difference between the modeled Chl a value and the in situ Chl a concentration is obvious, and the max value appears near the surface layer, as the surface Chl a concentration is high, which represents coastal and estuary waters(Case II).The results make an exploratory and tentative contribution to the vertical distributions of the Chl a concentration in the SCS, and lead to an empirical model and parameterization applicable to different oceanic waters. By combining this tool with satellite ocean color data, it becomes possible to reveal spatial and temporal distribution of phytoplankton biomass in the SCS.
Samplings of chlorophyll a (Chl a) concentration are analyzed based on historical cruises data for about 10 a in the South China Sea (SCS), including the northern SCS, the Nansha Islands and other sea areas in the SCS. The profiles of Chl a concentration are classified by the values within the surface layer, to develop a parameterization shape of Chl a concentration vertical profiles according to a generalized Gaussian model (adding a linear decline with a slope starting from the surface value). The modeled Chl a concentration vertical profiles show a normal distribution with a slightly declining slope, and fit well with the in situ Chl a concentration. The max value appears in subsurface layer, as the surface Chl a concentration is low, which represents deep-sea basin waters(Case I); while the difference between the modeled Chl a value and the in situ Chl a concentration is obvious, and the max value appears near the surface layer, as the surface Chl a concentration is high, which represents coastal and estuary waters(Case II).The results make an exploratory and tentative contribution to the vertical distributions of the Chl a concentration in the SCS, and lead to an empirical model and parameterization applicable to different oceanic waters. By combining this tool with satellite ocean color data, it becomes possible to reveal spatial and temporal distribution of phytoplankton biomass in the SCS.
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