Research On Ice Core Dating Of The Central Tibetan Plateau Based On High-Resolution Continuous Measurement Technology

The study of paleoclimate reveals environmental changes in historical periods,and also has an indication of future climate change trends.Ice core dating is the prerequisite and basis for the use of ice cores to recover climate and environmental records at different time scales.Limited by the accuracy of ice core data analysis,common methods cannot effectively divide the bottom annual layers.This study uses Electrical Conductivity Measurement(ECM)and optical scanning two high-resolution methods to date the Qiangtang No.1 core No.2 ice core,and established a new continuous optical scanning system for ice core profile.Combined with visual recognition and gray value curve,the system can accurately distinguish the layer at the bottom of the core which is thinner than 2cm.At the annual level,the entire ice core is dated.This method provides a new idea for optical scanning of ice cores and a reliable choice for highresolution dating of the ice core bottom of the Tibetan Plateau.The main conclusions are as follows:(1)By measuring the ECM of core No.2 on top 53.9m,it was found that the current value was stable at a low level of about 0.1?A,showing no obvious fluctuations,and no reference layer that could be used for dating.This method is more suitable for polar glaciers of marine origin,and no seasonal changes in acidity can be seen on ice cores that are heavily affected by alkaline dust.(2)The optical scanning system for ice core profile was used to complete the dating of the Qiangtang No.1 core No.2 ice core.The ice core image and ion concentration were used for dating from 0 to 79.5m,a total of 618 ± 18 years were found,and the annual thickness reduces from 24 cm to 7cm;The gray value was used to date from 79.5m to 109.8 m,a total of 518 ± 12 layers are identified to the bottom,the thickness of the annual layer decreases from 7cm to 2cm,and the entire ice core age spans about 1366 years.This method is similar to the Qiangtang No.1 core No.1 ice core.The dating results are accuracy.The annual layer on the upper part of the ice core is thick and susceptible to interference.The gray value dating method is suitable and more suitable for bottom dating.High-resolution imaging can also identify bubbles and dust layers in the ice core,providing possibilities for density viriation and structural analysis of the ice core.(3)By analyzing the changes in the gray values of the ice core,it was found that the gray value from the top to the bottom of the ice core presents an overall upward trend,reflecting the gradual decrease of bubbles' size from top to bottom,and the gradual increase in bubble density.Compared with the meteorological data of Bangor Station from 1957 to 2011,it was found that the gray value has no obvious correlation with temperature and precipitation,but the gray value corresponds well to the precipitation peak.It is believed that the gray value has a certain corresponding relationship with precipitation,but the relationship is affected by bubbles and cannot be directly reflected.