The results of time series sediment trap experiments in the South China Sea show that particulate organic carbon (POC) fluxes are influenced by the monsoons. The increase of productivity in the northern South China Se...The results of time series sediment trap experiments in the South China Sea show that particulate organic carbon (POC) fluxes are influenced by the monsoons. The increase of productivity in the northern South China Sea is mainly due to northeast monsoon while in the central South China Sea the influence of southwest monsoon becomes more prominent. The annual primary production and export production calculated based on POC fluxes are 53 0-63 4 and 10 32-12 93 gC·m -2·a -1, respectively. The enhancement of POC flux during monsoon period suggest that higher palaeoproductivity or organic carbon accumulation rate in glacial age in the South China Sea might be the result of strengthening of the monsoons.展开更多
Primary production, bacterial production, par-ticulate organic carbon fluxes and organic carbon burial rates were quantified during the summer period of 1999 in the Arctic Ocean via 14C uptake, 3H uptake, 234Th/238U d...Primary production, bacterial production, par-ticulate organic carbon fluxes and organic carbon burial rates were quantified during the summer period of 1999 in the Arctic Ocean via 14C uptake, 3H uptake, 234Th/238U disequilibrium and 210Pbex dating, respectively. The integrated primary production in the water column was as high as 197 mmolC/(m2·d) in the Chukchi shelf and was 3.8 mmolC/(m2·d) in the Canada Basin. These rates are higher than those reported previously. The ratios of bacterial production to primary production in the study region were higher than 0.5, indicating that microbial activity is not depressed but important in cold Arctic waters. 234Th/238U dis-equilibria were evident at the station in the Canada Basin. The presence of significant 234Th deficiency suggested that scavenging and removal processes are also important to bio-geochemical cycles of trace elements in the Arctic Ocean. Particulate organic carbon export flux was estimated to be 1.0 mmolC/(m2·d). Measurements of sediment展开更多
In order to elucidate the regional export variation of participate organiccarbon in the western Arctic Ocean, samples vertically integrated between 0 and 100 m depth orbetween 0 and 30 m/40 m depth were collected for ...In order to elucidate the regional export variation of participate organiccarbon in the western Arctic Ocean, samples vertically integrated between 0 and 100 m depth orbetween 0 and 30 m/40 m depth were collected for total ^(234)Th measurements and those from 30 m/40m or 100 m depth were collected for paniculate ^(234)Th measurements during the Second ChineseArctic Expedition in July— September 2003. The removal fluxes and residence time of ^(234)Th in theupper water column were calculated by using irreversible steady-state scavenging model. The resultsshowed that, total ^(234)Th was deficit relative to its parent ^(238)U in the western Arctic Oceanexcept in the western Chukchi shelf and the slope regions around 160°W, indicating that scavengingand removal processes play an important role in element biogeochemical cycle in the Arctic Ocean. Inthe western Chukchi shelf and the slope regions around 160°W, total ^(234)Th was excess relativeto ^(238)U, ascribing to the horizontal input of ^(234)Th adsorbed by ice-rafted sediments.Thorium-234 removal fluxes decreased from the shelf to the deep ocean, while the residence time of^(234)Th increased from shelf to offshore, demonstrating that particle scavenging and removalprocesses are more active in the shelf regions. The estimated POC export fluxes from 40 m in theshelf regions and from 100 m in the slope and deep ocean varied between 1.6 and 27.5 mmol/(m^2·d),and between 1.8 and 14.4 mmol/(m^2·d), respectively. The averaged POC export fluxes over the entirewater column decreased from the shelf to the deep ocean, indicating that the Chukchi shelf is animportant region for organic carbon sequestration. The high ThE ratios (ratio of POC export fluxderived from ^(234)Th/^(238)U disequilibria to primary production) in the western Arctic Oceansuggested that the biological pump runs actively in high-latitudes.展开更多
The coupling of upper ocean-benthic carbon dynamics in the ice-free western Arctic Ocean （the Chukchi Sea and the Canada Basin） was evaluated during the late July-early September 2003 using natural stable （13C） an...The coupling of upper ocean-benthic carbon dynamics in the ice-free western Arctic Ocean （the Chukchi Sea and the Canada Basin） was evaluated during the late July-early September 2003 using natural stable （13C） and radioactive （238U-234Th） isotope tracers. POC export flux estimated from 234Th/238U disequilibria and dissolved CO2 concentration （[CO2（aq）]） pointed out that the strengthened biological pump in the Chukchi Shelf have significantly lowered [CO2（aq）] and altered the magnitude of isotopic （12C/13C） fractionation during carbon fixation in the surface ocean. Further, δ13C signatures of surface sediments （δ13Csed） are positively correlated to those of weighted δ13Cp0C in upper ocean （δ13Csed =13.64＋1.56xδ13Cpoc, r2=0.73, p〈0.01）, suggesting that the POC isotopic signals from upper ocean have been recorded in the sediments, partly due to the rapid export of particles as evidenced by low residence times of the highly particle-reactive 234Th from the upper water column. It is suggested that there probably exists an upper ocean-benthic coupling of carbon dynamics, which likely assures the sedimentary δ13C record an indicator of paleo-CO2 in the western Arctic Ocean.展开更多
To evaluate the particle dynamics and estimate the POC (particulate organic carbon) export flux from the euphotic zone in the western Arctic Ocean,234 Th238 U disequilibrium was applied during the second Chinese Natio...To evaluate the particle dynamics and estimate the POC (particulate organic carbon) export flux from the euphotic zone in the western Arctic Ocean,234 Th238 U disequilibrium was applied during the second Chinese National Arctic Research Expedition (July 15-September 26,2003).The POC export fluxes are estimated from the measured profiles of the 234 Th/238 U activity ratios and the POC/PTh ratios.The average residence times of the particulate and dissolved 234 Th in the euphotic zone are 33 d and 121 d,and their average export fluxes are 480 dpm/m 2 d and 760 dpm/m 2 d,respectively.The scavenging and removal processes of particle reactive elements are active in the upper layer of the Chukchi Sea.The average residence time of 234 Th increases from shelf to basin,while the export fluxes of 234 Th decrease.The estimated POC export fluxes from the euphotic zone vary from 2.1 to 20.3 mmol/m 2 d,indicating that the western Arctic Ocean is an important carbon sink in summer due to efficient biological pump.展开更多
^(234)Th-^(238)U disequilibria were applied to examine the particle dynamics in the euphotic zone of the central South China Sea during the spring 2002 cruise.The particulate organic carbon (POC),^(234)Th (including b...^(234)Th-^(238)U disequilibria were applied to examine the particle dynamics in the euphotic zone of the central South China Sea during the spring 2002 cruise.The particulate organic carbon (POC),^(234)Th (including both dissolved and particulate) and ^(238)U in the water column at three stations were determined. The profiles of ^(234)Th/^(238)U activity ratio at the three stations all showed consistent ^(234)Th deficit as compared to ^(238)U in the upper 100 m water column.Based on the profiles of the dissolved and particulate ^(234)Th and a steady state box model,the dissolved ^(234)Th scavenging rates,the particulate ^(234)Th removal rates and their resident times were quantified.It was found that the POC downward export fluxes out of the upper 100 m euphotic zone ranged from 9.40 to 14.78 mmol·m^(-2)·d^(-1).The results from this study provide new information for our understanding of carbon biogeochemical cycle in the South China Sea.展开更多
文摘The results of time series sediment trap experiments in the South China Sea show that particulate organic carbon (POC) fluxes are influenced by the monsoons. The increase of productivity in the northern South China Sea is mainly due to northeast monsoon while in the central South China Sea the influence of southwest monsoon becomes more prominent. The annual primary production and export production calculated based on POC fluxes are 53 0-63 4 and 10 32-12 93 gC·m -2·a -1, respectively. The enhancement of POC flux during monsoon period suggest that higher palaeoproductivity or organic carbon accumulation rate in glacial age in the South China Sea might be the result of strengthening of the monsoons.
基金This work was supported by the Chinese First Arctic Expedition Foundation the National Natural Science Foundation of China (Grant No. 40076024).
文摘Primary production, bacterial production, par-ticulate organic carbon fluxes and organic carbon burial rates were quantified during the summer period of 1999 in the Arctic Ocean via 14C uptake, 3H uptake, 234Th/238U disequilibrium and 210Pbex dating, respectively. The integrated primary production in the water column was as high as 197 mmolC/(m2·d) in the Chukchi shelf and was 3.8 mmolC/(m2·d) in the Canada Basin. These rates are higher than those reported previously. The ratios of bacterial production to primary production in the study region were higher than 0.5, indicating that microbial activity is not depressed but important in cold Arctic waters. 234Th/238U dis-equilibria were evident at the station in the Canada Basin. The presence of significant 234Th deficiency suggested that scavenging and removal processes are also important to bio-geochemical cycles of trace elements in the Arctic Ocean. Particulate organic carbon export flux was estimated to be 1.0 mmolC/(m2·d). Measurements of sediment
基金supported by the Program for New Century Excellent Talents in University of China under contract No.NCET-04-0593 and the Chinese Second Arctic Expedition Foundation.
文摘In order to elucidate the regional export variation of participate organiccarbon in the western Arctic Ocean, samples vertically integrated between 0 and 100 m depth orbetween 0 and 30 m/40 m depth were collected for total ^(234)Th measurements and those from 30 m/40m or 100 m depth were collected for paniculate ^(234)Th measurements during the Second ChineseArctic Expedition in July— September 2003. The removal fluxes and residence time of ^(234)Th in theupper water column were calculated by using irreversible steady-state scavenging model. The resultsshowed that, total ^(234)Th was deficit relative to its parent ^(238)U in the western Arctic Oceanexcept in the western Chukchi shelf and the slope regions around 160°W, indicating that scavengingand removal processes play an important role in element biogeochemical cycle in the Arctic Ocean. Inthe western Chukchi shelf and the slope regions around 160°W, total ^(234)Th was excess relativeto ^(238)U, ascribing to the horizontal input of ^(234)Th adsorbed by ice-rafted sediments.Thorium-234 removal fluxes decreased from the shelf to the deep ocean, while the residence time of^(234)Th increased from shelf to offshore, demonstrating that particle scavenging and removalprocesses are more active in the shelf regions. The estimated POC export fluxes from 40 m in theshelf regions and from 100 m in the slope and deep ocean varied between 1.6 and 27.5 mmol/(m^2·d),and between 1.8 and 14.4 mmol/(m^2·d), respectively. The averaged POC export fluxes over the entirewater column decreased from the shelf to the deep ocean, indicating that the Chukchi shelf is animportant region for organic carbon sequestration. The high ThE ratios (ratio of POC export fluxderived from ^(234)Th/^(238)U disequilibria to primary production) in the western Arctic Oceansuggested that the biological pump runs actively in high-latitudes.
基金Chinese Polar Environment Comprehensive Investigation and Assessment Programs under contract Nos CHINARE 2014-03-04-03 and CHINARE 2014-04-03-05the National Natural Science Foundation of China under contract Nos 41125020 and 41206062+2 种基金a special scientific research project for public welfare under contract No.201105022-4the research project supported by the State Oceanic Administration under contract No.GASI-03-01-02-02the Natural Science Foundation of Fujian Province of China under contract No.2014J05049
文摘The coupling of upper ocean-benthic carbon dynamics in the ice-free western Arctic Ocean （the Chukchi Sea and the Canada Basin） was evaluated during the late July-early September 2003 using natural stable （13C） and radioactive （238U-234Th） isotope tracers. POC export flux estimated from 234Th/238U disequilibria and dissolved CO2 concentration （[CO2（aq）]） pointed out that the strengthened biological pump in the Chukchi Shelf have significantly lowered [CO2（aq）] and altered the magnitude of isotopic （12C/13C） fractionation during carbon fixation in the surface ocean. Further, δ13C signatures of surface sediments （δ13Csed） are positively correlated to those of weighted δ13Cp0C in upper ocean （δ13Csed =13.64＋1.56xδ13Cpoc, r2=0.73, p〈0.01）, suggesting that the POC isotopic signals from upper ocean have been recorded in the sediments, partly due to the rapid export of particles as evidenced by low residence times of the highly particle-reactive 234Th from the upper water column. It is suggested that there probably exists an upper ocean-benthic coupling of carbon dynamics, which likely assures the sedimentary δ13C record an indicator of paleo-CO2 in the western Arctic Ocean.
基金Supported by the National Natural Science Foundation of China (No.40531007)the China Action Plan of the International Polar Year (Nos.2009DFA22920 and 2008Po5040014-03)+1 种基金the International Science and Technology Cooperation (Nos. 2008DFA20420 and 2009DFA22920)the Polar Atmospheric Environment Remote Sensing Monitoring Technique of the National High Technology Research and DevelopmentProgram of China (863 Program) (No. N2008DFA20420)
文摘To evaluate the particle dynamics and estimate the POC (particulate organic carbon) export flux from the euphotic zone in the western Arctic Ocean,234 Th238 U disequilibrium was applied during the second Chinese National Arctic Research Expedition (July 15-September 26,2003).The POC export fluxes are estimated from the measured profiles of the 234 Th/238 U activity ratios and the POC/PTh ratios.The average residence times of the particulate and dissolved 234 Th in the euphotic zone are 33 d and 121 d,and their average export fluxes are 480 dpm/m 2 d and 760 dpm/m 2 d,respectively.The scavenging and removal processes of particle reactive elements are active in the upper layer of the Chukchi Sea.The average residence time of 234 Th increases from shelf to basin,while the export fluxes of 234 Th decrease.The estimated POC export fluxes from the euphotic zone vary from 2.1 to 20.3 mmol/m 2 d,indicating that the western Arctic Ocean is an important carbon sink in summer due to efficient biological pump.
基金Supported by the NSFC (key program No.40531007) and general Programs (No.40406014,40276001 and 10705019)the State Social Commonweal Grant (No.2004DIB5178)+1 种基金and the commonweal project sponsored by the Scientific Research Foundation of the Ministry of Science and Technology of China (No.2007050228)Chinese IPY Campaign found by MOF
文摘^(234)Th-^(238)U disequilibria were applied to examine the particle dynamics in the euphotic zone of the central South China Sea during the spring 2002 cruise.The particulate organic carbon (POC),^(234)Th (including both dissolved and particulate) and ^(238)U in the water column at three stations were determined. The profiles of ^(234)Th/^(238)U activity ratio at the three stations all showed consistent ^(234)Th deficit as compared to ^(238)U in the upper 100 m water column.Based on the profiles of the dissolved and particulate ^(234)Th and a steady state box model,the dissolved ^(234)Th scavenging rates,the particulate ^(234)Th removal rates and their resident times were quantified.It was found that the POC downward export fluxes out of the upper 100 m euphotic zone ranged from 9.40 to 14.78 mmol·m^(-2)·d^(-1).The results from this study provide new information for our understanding of carbon biogeochemical cycle in the South China Sea.
