Speleothem records of Asian paleomonsoon variability and mechanisms
Author(s): WANG YongJin, LIU DianBing, College of Geography Science, Nanjing Normal University
Pages: 938-951
Year: 2016 Issue: 9
Journal: Chinese Science Bulletin
Keyword: stalagmite records; Asian monsoon climates; precessional cycle; high-and low-latitude climate teleconnection; late Quaternary;
Abstract: In the last 20 years, speleothems have been increasingly applied in paleoclimate studies, and become one of the most important geologic records like oceanic sediments, loess deposits, and ice cores. Critically, the stalagmite archives from Asian monsoon(AM) area provide an insight into the mechanisms behind low-latitude precessional hydroclimate and abrupt AM changes in line with millennial-scale Greenland temperature variability. These climate records from the Asian continent interiors, well-duplicated over broad regions, extend back to 600 ka BP, and have been widely accepted as a North Hemisphere template for synchronizing global climate records. Here we review these independently- and precisely-dated stalagmite records from those climatically- and environmentally-sensitive locations and discuss various climate factors that control AM variability from annual to orbital time scales. As the speleothems are often annually laminated that extend back into a long growth history, it is possible to understand mechanisms of millennial- to annual-scale climate changes under different Earth’s climatic boundaries. By nature, these calcite records are instrumental in resolving the climate background for natural variability of current climate, abrupt climate changes in the distant time, and even a prediction for future climate. As an important sub-system of global climate, the AM climate characterizes distinct seasonal cycle of wind directions, temperature, and precipitation. It can link tropical ocean processes and even the Southern Ocean via southerly air masses, and high northern latitudes through northerly air parcels. Hence, the AM record is ideal for evaluating the forcing-response correlation between hemispheric climates. On the basis of reviewing various stalagmite proxies(i.e., ?18 O, ?13 C, trace element, annual layer, fluid inclusions, etc.) for parameters of AM climate, we discuss a potential to understand sources and trajectories of AM circulations by use of the speleothem oxygen isotope over broad regions. However, the interpretation of stable oxygen isotopes, especially a rainfall amount effect, frequently used in Chinese speleothem records remains a topic of intense debate. Considering the sources and sinks of atmospheric hydrological circulations, this review addresses the progress of stalagmite-based Asian paleomonsoon studies and the implication of Chinese speleothem ?18 O signal. As a proxy to track atmospheric moisture isotopic compositions, millennial to centennial changes of the speleothem ?18 O is supported by the atmospheric ?18 O record trapped in ice-cores. Thus, it is likely that at orbital to millennial scales, the stalagmite isotopic sequences from the Asian monsoon area can represent the alternation of aridity/ moisture associated with Asian monsoon changes. Constrained by high-precision U/Th dates, the speleothem records, covering the Mid-Brunhes Event, provide a chronological benchmark to link low-latitude hydrological circulations and high-latitude ice-sheet processes, and hence can synchronize oceanic, atmospheric, and ice-sheet changes. Once applied a unified time scale, those speleothem records can further evaluate the relationship between changes in continental ice sheets, low-latitude monsoon climates, greenhouse gasses, and biogeochemical processes. In previous literatures, the timing and frequency of these calcite ?18 O records have been widely consolidated by other archives within and outside the AM area. This implicates that the climate signals contained in Chinese speleothems can sensitively capture North Hemisphere climate changes via reorganization of atmospheric circulations. Hence, it is possible that stalagmite isotopic sequences can be used to reconstruct a stratotype for terrestrial isotopic climates, and help resolve the mechanism of current global warming.
Pages: 938-951
Year: 2016 Issue: 9
Journal: Chinese Science Bulletin
Keyword: stalagmite records; Asian monsoon climates; precessional cycle; high-and low-latitude climate teleconnection; late Quaternary;
Abstract: In the last 20 years, speleothems have been increasingly applied in paleoclimate studies, and become one of the most important geologic records like oceanic sediments, loess deposits, and ice cores. Critically, the stalagmite archives from Asian monsoon(AM) area provide an insight into the mechanisms behind low-latitude precessional hydroclimate and abrupt AM changes in line with millennial-scale Greenland temperature variability. These climate records from the Asian continent interiors, well-duplicated over broad regions, extend back to 600 ka BP, and have been widely accepted as a North Hemisphere template for synchronizing global climate records. Here we review these independently- and precisely-dated stalagmite records from those climatically- and environmentally-sensitive locations and discuss various climate factors that control AM variability from annual to orbital time scales. As the speleothems are often annually laminated that extend back into a long growth history, it is possible to understand mechanisms of millennial- to annual-scale climate changes under different Earth’s climatic boundaries. By nature, these calcite records are instrumental in resolving the climate background for natural variability of current climate, abrupt climate changes in the distant time, and even a prediction for future climate. As an important sub-system of global climate, the AM climate characterizes distinct seasonal cycle of wind directions, temperature, and precipitation. It can link tropical ocean processes and even the Southern Ocean via southerly air masses, and high northern latitudes through northerly air parcels. Hence, the AM record is ideal for evaluating the forcing-response correlation between hemispheric climates. On the basis of reviewing various stalagmite proxies(i.e., ?18 O, ?13 C, trace element, annual layer, fluid inclusions, etc.) for parameters of AM climate, we discuss a potential to understand sources and trajectories of AM circulations by use of the speleothem oxygen isotope over broad regions. However, the interpretation of stable oxygen isotopes, especially a rainfall amount effect, frequently used in Chinese speleothem records remains a topic of intense debate. Considering the sources and sinks of atmospheric hydrological circulations, this review addresses the progress of stalagmite-based Asian paleomonsoon studies and the implication of Chinese speleothem ?18 O signal. As a proxy to track atmospheric moisture isotopic compositions, millennial to centennial changes of the speleothem ?18 O is supported by the atmospheric ?18 O record trapped in ice-cores. Thus, it is likely that at orbital to millennial scales, the stalagmite isotopic sequences from the Asian monsoon area can represent the alternation of aridity/ moisture associated with Asian monsoon changes. Constrained by high-precision U/Th dates, the speleothem records, covering the Mid-Brunhes Event, provide a chronological benchmark to link low-latitude hydrological circulations and high-latitude ice-sheet processes, and hence can synchronize oceanic, atmospheric, and ice-sheet changes. Once applied a unified time scale, those speleothem records can further evaluate the relationship between changes in continental ice sheets, low-latitude monsoon climates, greenhouse gasses, and biogeochemical processes. In previous literatures, the timing and frequency of these calcite ?18 O records have been widely consolidated by other archives within and outside the AM area. This implicates that the climate signals contained in Chinese speleothems can sensitively capture North Hemisphere climate changes via reorganization of atmospheric circulations. Hence, it is possible that stalagmite isotopic sequences can be used to reconstruct a stratotype for terrestrial isotopic climates, and help resolve the mechanism of current global warming.
Related Articles