Long-chain alkenones were detected in samples of sea surface sediments from the Chukchi Sea and the Bering Sea areas, the Arctic Pole. The analysis result indicates that C37:3 methylketone is predominate in the long-c...Long-chain alkenones were detected in samples of sea surface sediments from the Chukchi Sea and the Bering Sea areas, the Arctic Pole. The analysis result indicates that C37:3 methylketone is predominate in the long-chain alkenones from the Chukchi and Bering Sea sediments. The abundance of C37 to C39 unsaturated alkenones changes in an order of C37 > C38 > C39. Based on C37 /C38 ratio, the detected organism precursors of the long-chain alkenones are mainly coccolithophrid (Emiliania huxleyi). By the calibration relationship between U37k and U37k indices, the sea surface paleotemperature in these seas is estimated. The estimated values of U37k vary from 4.147℃ to 5.706℃ , with a mean value of 5.092℃.展开更多
The long-chain alkenones present in the shallow sediment of Hotong Qagan Nur Lake in China are reported. According to the similarity of compositions and distributions of the alkenones determined commonly in the sedime...The long-chain alkenones present in the shallow sediment of Hotong Qagan Nur Lake in China are reported. According to the similarity of compositions and distributions of the alkenones determined commonly in the sediment section to those of marine sediment, it is reasonably referred that the alkenones might also originate from Prymnesiophyceae. ln addition, the parameter U<sub>37</sub><sup>k</sup>'of alkenone is in positive correlation to δ<sup>18</sup>O values of authigenic calcium and magnesium minerals. This indicates that the parameter U<sub>37</sub><sup>k</sup>'of long-chain alkenone is also available to indicate paleoclimate of high-salinity alkaline lake.展开更多
The northern South China Sea(NSCS)is significantly influenced by the Kuroshio intrusion and the coastal currents.Our knowledge on the roles of both currents on phytoplankton spatial variations is still inadequate.Here...The northern South China Sea(NSCS)is significantly influenced by the Kuroshio intrusion and the coastal currents.Our knowledge on the roles of both currents on phytoplankton spatial variations is still inadequate.Here,we investigated the concentrations of phytoplankton biomarkers and their proportions in surface suspended particles from 47 sites of the NSCS during summer of 2017 and 2019.Brassicasterol/epi-brassicasterol,dinosterol,and C37 alkenones were used as proxies of biomass for diatoms,dinoflagellates,and haptophytes,respectively,and their sum indicating total phytoplankton biomass.A three end-member mixing model was applied to quantitatively assess the influence extent of the Kuroshio intrusion and the coastal currents.Our results showed that the Kuroshio intrusion and the coastal currents contributed equally to the overall surface water masses in the study area;however,the two currents had distinct effects on the spatial distribution of phytoplankton.For phytoplankton biomass,the eutrophic coastal currents were likely to be the main controlling factors,while the impact of the Kuroshio intrusion was weak and stimulated significant increases in phytoplankton biomass only at certain boundary sites.For phytoplankton community structures,the Kuroshio and its intrusion were the main factors,resulting in an increase in the proportions of dinoflagellates and haptophytes.The proportion of diatoms slightly increased due to the influence of the coastal currents.Our study quantifies the effects of the Kuroshio and the coastal currents on phytoplankton in the NSCS in terms of hydrological parameters,providing an important basis for the understanding of ecological functions and biogeochemical cycles in marginal sea-open ocean boundary regions.展开更多
Sea surface temperatures (SSTs) in the southwestern South China Sea have been reconstructed for the past 160 ka using the U37^k paleothermometer from the core MD01 - 2392. The temperature differences between glacial...Sea surface temperatures (SSTs) in the southwestern South China Sea have been reconstructed for the past 160 ka using the U37^k paleothermometer from the core MD01 - 2392. The temperature differences between glacial times ( MISs 6 and 2) and interglacial times ( MISs 5.5 and 1) are 2.2 ~ 2.5 ℃. Younger Dryas event during the last deglaciation was documented in both the planktonic foraminiferal δ^18 and SST records. After MIS 5.5, SSTs displayed a progressive cooling from 28.6 to 24.5 ℃ culminating at the LGM. During this gradual cooling period, warm events such as MISs 5.3, 5.1 and 3 were also clearly documented. By comparison of SST between the study core and Core 17954, a pattern of low or no meridional SST gradients during the interglacial periods and high meridional SST gradients during the glacial periods was exhibited. This pattern indicates the much stronger East Asian winter monsoon at the glacial than at the interglacial periods. Spectral analysis gives two prominent cycles:41 and 23 ka, with the former more pronounced, suggesting that SSTs in the southern SCS varied in concert with high-latitude processes through the connection of East Asian winter monsoon.展开更多
To investigate the relationship between the alkenone unsaturation index(U^(K′)_(37)) and sea surface temperature(SST) in coastal and continental shelf waters, 58 surface sediment samples were collected from the South...To investigate the relationship between the alkenone unsaturation index(U^(K′)_(37)) and sea surface temperature(SST) in coastal and continental shelf waters, 58 surface sediment samples were collected from the South China Sea(SCS), Taiwan Strait,and East China Sea(ECS). We combined the new results with the previously published 71 data points from the SCS, the shallow water areas of the Yellow Sea(YS) and northern ECS, to form a dataset with sample sites spanning across 6°N and 37°N(including annual SST calibration between 14.3℃ and 28.6℃). With this dataset, we examined the U^(K′)_(37)-SST relationship based on 129 samples from the Western North Pacific(WNP) margin as well as using 85 samples from specific WNP shallow water.The U^(K′)_(37)index from the low-mid latitudinal WNP margin demonstrated a good correlation with the surface annual mean SST(0–50 m water depth;R^(2)=0.89). The slope of linear regression(U^(K′)_(37)-SST) based on the coastal-continental shelf samples with water depth less than 200 m is similar to that of the published global open ocean regression equation. These results confirm that U^(K′)_(37)can be used as a shallow sea water SST proxy in mid-low latitudes of the WNP marginal seas. In addition, our reintegrated U^(K′)_(37)-SST results based on 172 global shallow water samples are similar(similar slopes and intercepts) to the shallow ocean results in the WNP marginal seas. However, the similarity of the regression formula to the open ocean does not imply that the formula is applicable. For example, of the 85 data in the shallow waters from the marginal sea in this study, the majority of data points lie above the regression line, showing positive residuals for U^(K′)_(37). This regression bias appears to be caused by specific marine environments, such as warm ocean currents and/or high nutrient conditions that result in positive U^(K′)_(37)residuals. Taken together,considering the specific temperature and environmental factors in the shallow waters of the low-mid-latitude WNP margin, we propose a nonlinear U^(K′)_(37)-SST regression formula: U^(K′)_(37)=-1.2488+0.1740×SST-0.0035×(SST)2, R2=0.93, N=85, specifically for the environments with SST below 24℃.展开更多
基金This study was supported by the First Chinese National Scientific Observation for the Arctic the Development Program of NKBR
文摘Long-chain alkenones were detected in samples of sea surface sediments from the Chukchi Sea and the Bering Sea areas, the Arctic Pole. The analysis result indicates that C37:3 methylketone is predominate in the long-chain alkenones from the Chukchi and Bering Sea sediments. The abundance of C37 to C39 unsaturated alkenones changes in an order of C37 > C38 > C39. Based on C37 /C38 ratio, the detected organism precursors of the long-chain alkenones are mainly coccolithophrid (Emiliania huxleyi). By the calibration relationship between U37k and U37k indices, the sea surface paleotemperature in these seas is estimated. The estimated values of U37k vary from 4.147℃ to 5.706℃ , with a mean value of 5.092℃.
文摘The long-chain alkenones present in the shallow sediment of Hotong Qagan Nur Lake in China are reported. According to the similarity of compositions and distributions of the alkenones determined commonly in the sediment section to those of marine sediment, it is reasonably referred that the alkenones might also originate from Prymnesiophyceae. ln addition, the parameter U<sub>37</sub><sup>k</sup>'of alkenone is in positive correlation to δ<sup>18</sup>O values of authigenic calcium and magnesium minerals. This indicates that the parameter U<sub>37</sub><sup>k</sup>'of long-chain alkenone is also available to indicate paleoclimate of high-salinity alkaline lake.
基金The study was supported by the National Natural Science Foundation of China(No.41876118)the Global Climate Changes and Air-Sea Interaction Program(No.GASI-02-PAC-ST-Wwin)This is MCTL(Key Laboratory of Marine Chemistry Theory and Technology)contribution#281.
文摘The northern South China Sea(NSCS)is significantly influenced by the Kuroshio intrusion and the coastal currents.Our knowledge on the roles of both currents on phytoplankton spatial variations is still inadequate.Here,we investigated the concentrations of phytoplankton biomarkers and their proportions in surface suspended particles from 47 sites of the NSCS during summer of 2017 and 2019.Brassicasterol/epi-brassicasterol,dinosterol,and C37 alkenones were used as proxies of biomass for diatoms,dinoflagellates,and haptophytes,respectively,and their sum indicating total phytoplankton biomass.A three end-member mixing model was applied to quantitatively assess the influence extent of the Kuroshio intrusion and the coastal currents.Our results showed that the Kuroshio intrusion and the coastal currents contributed equally to the overall surface water masses in the study area;however,the two currents had distinct effects on the spatial distribution of phytoplankton.For phytoplankton biomass,the eutrophic coastal currents were likely to be the main controlling factors,while the impact of the Kuroshio intrusion was weak and stimulated significant increases in phytoplankton biomass only at certain boundary sites.For phytoplankton community structures,the Kuroshio and its intrusion were the main factors,resulting in an increase in the proportions of dinoflagellates and haptophytes.The proportion of diatoms slightly increased due to the influence of the coastal currents.Our study quantifies the effects of the Kuroshio and the coastal currents on phytoplankton in the NSCS in terms of hydrological parameters,providing an important basis for the understanding of ecological functions and biogeochemical cycles in marginal sea-open ocean boundary regions.
基金This work was financially supported by the National Natural Science Foundation of China under contract No.40103006the National Key Basic Research Special Funds of China under contract No.G200078500.
文摘Sea surface temperatures (SSTs) in the southwestern South China Sea have been reconstructed for the past 160 ka using the U37^k paleothermometer from the core MD01 - 2392. The temperature differences between glacial times ( MISs 6 and 2) and interglacial times ( MISs 5.5 and 1) are 2.2 ~ 2.5 ℃. Younger Dryas event during the last deglaciation was documented in both the planktonic foraminiferal δ^18 and SST records. After MIS 5.5, SSTs displayed a progressive cooling from 28.6 to 24.5 ℃ culminating at the LGM. During this gradual cooling period, warm events such as MISs 5.3, 5.1 and 3 were also clearly documented. By comparison of SST between the study core and Core 17954, a pattern of low or no meridional SST gradients during the interglacial periods and high meridional SST gradients during the glacial periods was exhibited. This pattern indicates the much stronger East Asian winter monsoon at the glacial than at the interglacial periods. Spectral analysis gives two prominent cycles:41 and 23 ka, with the former more pronounced, suggesting that SSTs in the southern SCS varied in concert with high-latitude processes through the connection of East Asian winter monsoon.
基金supported by the Guangzhou Science and Technology Plan Project(Grant No.202102080366)the Guangdong Academy of Sciences(Grant No.2016GDASRC-0209)+1 种基金the Research Grant Council of Hong Kong(Grant No.HKU17311816)the National Natural Science Foundation of China(Grant Nos.42106062,41706039&41606070)。
文摘To investigate the relationship between the alkenone unsaturation index(U^(K′)_(37)) and sea surface temperature(SST) in coastal and continental shelf waters, 58 surface sediment samples were collected from the South China Sea(SCS), Taiwan Strait,and East China Sea(ECS). We combined the new results with the previously published 71 data points from the SCS, the shallow water areas of the Yellow Sea(YS) and northern ECS, to form a dataset with sample sites spanning across 6°N and 37°N(including annual SST calibration between 14.3℃ and 28.6℃). With this dataset, we examined the U^(K′)_(37)-SST relationship based on 129 samples from the Western North Pacific(WNP) margin as well as using 85 samples from specific WNP shallow water.The U^(K′)_(37)index from the low-mid latitudinal WNP margin demonstrated a good correlation with the surface annual mean SST(0–50 m water depth;R^(2)=0.89). The slope of linear regression(U^(K′)_(37)-SST) based on the coastal-continental shelf samples with water depth less than 200 m is similar to that of the published global open ocean regression equation. These results confirm that U^(K′)_(37)can be used as a shallow sea water SST proxy in mid-low latitudes of the WNP marginal seas. In addition, our reintegrated U^(K′)_(37)-SST results based on 172 global shallow water samples are similar(similar slopes and intercepts) to the shallow ocean results in the WNP marginal seas. However, the similarity of the regression formula to the open ocean does not imply that the formula is applicable. For example, of the 85 data in the shallow waters from the marginal sea in this study, the majority of data points lie above the regression line, showing positive residuals for U^(K′)_(37). This regression bias appears to be caused by specific marine environments, such as warm ocean currents and/or high nutrient conditions that result in positive U^(K′)_(37)residuals. Taken together,considering the specific temperature and environmental factors in the shallow waters of the low-mid-latitude WNP margin, we propose a nonlinear U^(K′)_(37)-SST regression formula: U^(K′)_(37)=-1.2488+0.1740×SST-0.0035×(SST)2, R2=0.93, N=85, specifically for the environments with SST below 24℃.
基金financially supported by the Strategic Priority Research Program of Chinese Academy of Sciences(XDB40000000)the National Natural Science Foundation of China(41672349,40802084)Hong Kong Research Grants Council(17325516)。