Seasonal variations in surface processes and hydroclimate on an alpine lake, NE Tibetan Plateau

• Published in: Quaternary Science Reviews
• Main Authors: Wunnemann, Bernd, Yan, Dada, Hu, Shuai, Zhang, Yongzhan, Chen, Wei
• Format: Report
• Language: English
• Published: PERGAMON-ELSEVIER SCIENCE LTD 2023
• Subjects: Surface processes; Stable isotopes; Interannual variation; Holocene hydroclimate; Tibetan plateau; HIGH-RESOLUTION; STABLE-ISOTOPE; ASIAN MONSOON; SEA-LEVEL; HOLOCENE; PRECIPITATION; QINGHAI; CLIMATE; VARIABILITY; RECORD; Physical Geography; Geology; Geography; Physical; Geosciences; Multidisciplinary; Alpine Lake; Lower Lake; permafrost
• Online Access: http://ir.nigpas.ac.cn/handle/332004/41633; https://doi.org/10.1016/j.quascirev.2022.107876

Koucha Lake, located in Qinghai Province, north-eastern Tibetan Plateau (NETP) at an elevation of 4530 m a.s.l. Occupies an ideal position to investigate the seasonal hydroclimatic variations and related surface processes during the Holocene. We re-investigated the lake and analysed a new sediment core from the deepest part of the lake. Grain size measurements and related endmember modelling analyses (EMMA) in combination with ostracod associations together with geochemical parameters and mineral compo-sitions from core sediments were used as relevant proxies for hydro-climatic reconstruction.A compar-ison of 818O/8D from various waters on the NETP indicates a clear depleted isotopic signature of non -monsoon moisture supply in comparison to summer rainfalls, highlighting the summer evaporation for 818O enrichment, as a reference for interpreting 818O values from lake sediments for various situa-tions of hydrological balance. Based on the individual core chronology the multi-proxy data indicate a very low sedimentation rate over the entire period in accordance with the catchment topography and the absence of well-developed and constant river systems, limiting the flux of sediment supply to the lake. Thus, Koucha Lake remains almost a closed system since the Lateglacial, except for the early mid -Holocene part of the sequence. The coarser particle components and their representative endmembers for spring flood and permafrost thaw between 11.9 and 10.1 cal Ka BP and from 4.5 to ca. 1.0 cal Ka BP point to lower lake levels, influenced by long winter duration with dry summer interruptions, and lighter oxygen isotopes were preserved at low evaporations. Fine-grained sediments supplied by permafrost thaw associated with activating summer surface erosion led to lake level rise between 10.1 and 4.5 cal Ka BP and during the last 1000 years, with a maximum during 7.6-7.1 cal Ka BP. Their enriched 818O values indicate extended summer duration and concomitant evaporation enhancement, albeit a positive hy-drological balance. ...