Long-chain alkenones (LCAs) can potentially be used as indicators to understand past variations in lacustrine environments.Previous research has suggested that the relationship between the temperature and the unsatura...Long-chain alkenones (LCAs) can potentially be used as indicators to understand past variations in lacustrine environments.Previous research has suggested that the relationship between the temperature and the unsaturation index of LCAs should be calibrated individually,because of the possible variations in the alkenone-producing algal species in the lacustrine environment.In this work,we have calibrated U37K' of water filter samples against the in-situ water temperature in Lake Qinghai,Tibetan Plateau.There are significant relationships between U37K' and the water temperature,a non-linear relationship was derived.Because the U37K' values did not respond sensitively at lower temperatures,we suggested that a quadratic regression (U37K' =0.0011×T2-0.0201×T+0.1959,n=15,r2=0.74) was appropriate than linear regression to represent the relationship between the in-situ temperatures and U37K'.Meanwhile,the U37K correlation relationship was not more significant than U37K' index in our study.Because of the C37:4 effects by salinity change,we suggest U37K is not as robust as the U37K' index as a temperature proxy,at least for the salt lake in the Tibetan Plateau.The calibration of the U37K' index in this work has provided a new understanding of historic climatic changes in the Tibetan Plateau.展开更多
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
Sea surface temperature(SST)in the Yellow Sea Warm Current(YSWC)pathway is sensitive to the East Asian Winter Monsoon(EAWM)and YSWC.However,the role of the YSWC in the evolution of regional SST remains unclear.Here,we...Sea surface temperature(SST)in the Yellow Sea Warm Current(YSWC)pathway is sensitive to the East Asian Winter Monsoon(EAWM)and YSWC.However,the role of the YSWC in the evolution of regional SST remains unclear.Here,we present new U 37 k′based SST and grain size sequences spanning the last 6092 years in the sediment core Z1,which was retrieved from the central Yellow Sea muddy area.Overall,U 37 k′-SST gradually increased since 6.1 ka BP,with a series of centennial-scale fl uctuations.Its variation was mainly caused by EAWM when YSWC was weak between 6.1 and~3.9 ka BP,as shown by the end-member content of grain size.However,after YSWC was fully developed,i.e.,since~3.9 ka BP,it exerted critical eff ects on SST evolution in its pathway.The 1010-and 538-year cycles of the SST sequence indicated a basic control of solar activity on the oceanic conditions in the Yellow Sea.It is suggested that the variation of total solar irradiance was amplifi ed by thermohaline circulation and then transmitted to the Yellow Sea through the EAWM.Meanwhile,the tropical Pacifi c signal of El Niño was transmitted to the YSWC through the Kuroshio Current.The dual properties of warm water transported by YSWC to compensate the EAWM and driving by Kuroshio Current closely linked the variation of SST in the YSWC pathway to the Northern Hemisphere high latitude climate and the tropical Pacifi c.These fi ndings highlight the signifi cance of YSWC on regional SST evolution and its teleconnection to high and low latitude forcing,which grains a better understanding of the long-term evolution of SST in the middle latitude Yellow Sea.展开更多
基金supported by the National Natural Science Foundation of China(41002059)the West Light Foundation of the Chinese Academy of Sciences
文摘Long-chain alkenones (LCAs) can potentially be used as indicators to understand past variations in lacustrine environments.Previous research has suggested that the relationship between the temperature and the unsaturation index of LCAs should be calibrated individually,because of the possible variations in the alkenone-producing algal species in the lacustrine environment.In this work,we have calibrated U37K' of water filter samples against the in-situ water temperature in Lake Qinghai,Tibetan Plateau.There are significant relationships between U37K' and the water temperature,a non-linear relationship was derived.Because the U37K' values did not respond sensitively at lower temperatures,we suggested that a quadratic regression (U37K' =0.0011×T2-0.0201×T+0.1959,n=15,r2=0.74) was appropriate than linear regression to represent the relationship between the in-situ temperatures and U37K'.Meanwhile,the U37K correlation relationship was not more significant than U37K' index in our study.Because of the C37:4 effects by salinity change,we suggest U37K is not as robust as the U37K' index as a temperature proxy,at least for the salt lake in the Tibetan Plateau.The calibration of the U37K' index in this work has provided a new understanding of historic climatic changes in the Tibetan Plateau.
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℃.
基金Supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB42000000)the National Natural Science Foundation of China(Nos.41830539,42076051)the Open Fund Project of the Key Laboratory of Marine Sedimentology and Environmental Geology,Ministry of Natural Resources(No.MASEG201901),and the Taishan Scholar Project。
文摘Sea surface temperature(SST)in the Yellow Sea Warm Current(YSWC)pathway is sensitive to the East Asian Winter Monsoon(EAWM)and YSWC.However,the role of the YSWC in the evolution of regional SST remains unclear.Here,we present new U 37 k′based SST and grain size sequences spanning the last 6092 years in the sediment core Z1,which was retrieved from the central Yellow Sea muddy area.Overall,U 37 k′-SST gradually increased since 6.1 ka BP,with a series of centennial-scale fl uctuations.Its variation was mainly caused by EAWM when YSWC was weak between 6.1 and~3.9 ka BP,as shown by the end-member content of grain size.However,after YSWC was fully developed,i.e.,since~3.9 ka BP,it exerted critical eff ects on SST evolution in its pathway.The 1010-and 538-year cycles of the SST sequence indicated a basic control of solar activity on the oceanic conditions in the Yellow Sea.It is suggested that the variation of total solar irradiance was amplifi ed by thermohaline circulation and then transmitted to the Yellow Sea through the EAWM.Meanwhile,the tropical Pacifi c signal of El Niño was transmitted to the YSWC through the Kuroshio Current.The dual properties of warm water transported by YSWC to compensate the EAWM and driving by Kuroshio Current closely linked the variation of SST in the YSWC pathway to the Northern Hemisphere high latitude climate and the tropical Pacifi c.These fi ndings highlight the signifi cance of YSWC on regional SST evolution and its teleconnection to high and low latitude forcing,which grains a better understanding of the long-term evolution of SST in the middle latitude Yellow Sea.
