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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 compositions from core sediments were used as relevant proxies for hydro-climatic reconstruction.A comparison of δ18O/δD 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 δ18O enrichment, as a reference for interpreting δ18O values from lake sediments for various situations 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 δ18O values indicate extended summer duration and concomitant evaporation enhancement, albeit a positive hydrological balance. We suggest that the interannual latitudinal shifts of the intertropical convergence zone (ITCZ) and westerly Jet and attendant varying monsoon rain belt locations are responsible tracers for the variation of the hydrological budget of the lake and the variable spatio-temporal precipitation patterns in humid and (semi) arid regions in China. • Surface processes varied interannually and between cold and warm seasons during the Holocene. • Co-existence of long cold winter and dry summer extremes at high altitudes. • Synchronous/asynchronous patterns of heat and precipitation distribution between high/low altitudes in China. • These patterns correspond to the interannual latitudinal shifts of the ITCZ and the westerly jet. [ABSTRACT FROM AUTHOR]

Ostracoda from non-marine waters have a significant potential role in monitoring ecological conditions and reconstructing paleoenvironments. During the last decades, the increase in research on ostracods on the Tibetan Plateau (TP) has been achieved, although there are still taxonomical and ecological problems in their application in Quaternary studies. The aim of this review is to summarize the occurrences of ostracods in surface samples from four selected lakes (Qinghai Lake, Lake Donggi Cona, Lake Kuhai and Hala Lake) along the modern monsoon marginal zone on the northeast Tibetan Plateau and to compare the ostracod associations in sediment cores from different sites with available proxy data after re-evaluation of chronologies in order to reconstruct hydroclimatic conditions and monsoon influence during the late Quaternary. Comprehensive reanalysis of ostracod data from selected lakes (including 3 closed and 1 open lake basins) on the northeastern TP shows that their occurrence and disappearance responded sensitively to salinity and related water depth changes during the late Quaternary. This could lead to a re-interpretation of other proxy data related to hydro-climatic interpretation. Ostracod-based reconstructions of lake level changes along the modern summer monsoon marginal zone of the northeastern TP during the late Quaternary indicate an overestimation of the contribution from monsoonal rainfall to strong lake level changes, while the glacier/snow meltwater supply was underestimated in previous studies. This inference sheds more light on moisture source and the interplay between westerlies and Asian Summer Monsoon on the northern TP. • Summarize of Recent ostracod associations and their environmental implications. • Comparison of ostracod associations in sediment records from different lakes. • Revised reconstruction of hydroclimate on the northeastern Tibetan Plateau (Qinghai Lake). • Influence of glacier meltwater on the water balance of lakes. [ABSTRACT FROM AUTHOR]