Orbital-scale temperature and hydroclimate variability on the central Tibetan Plateau inferred from lipid biomarkers in the ICDP Nam Co drilling record

Quantifying long-term temperature and hydroclimate variability on the Tibetan Plateau (TP) is essential for understanding the evolution of the Asian monsoon-westerly system and its response to orbital forcing. Large, deep, closed-basin lakes on the TP are highly sensitive to changes in effective moisture, seasonality, and glacial meltwater input. Continuous continental archives spanning multiple glacial-interglacial cycles, however, remain rare. Lake Nam Co (4,718 m a.s.l.), located in central Tibet, contains a thick succession of medium-bedded to finely laminated lacustrine fines interspersed with coarser grained intervals and represents a key site for resolving long-term climate dynamics on the Plateau. We present preliminary lipid biomarker-based results from a new 510-m long sedimentary drill core record recovered by the ICDP NamCore project to investigate Tibetan paleoclimate. Lipid were extracted from 143 core-catcher samples. Our initial analyses are focused on using glycerol dialkyl glycerol tetraethers (GDGTs) and long-chain alkenones (LCAs) to quantitatively reconstruct temperature, as well as assess water balance. In addition, n-alkanes were investigated to study vegetation variability and hydroclimate. Our hydroclimate reconstructions are based on the distribution of n-alkanes, which show coherent variations between the ratio of ACL_27-35 and the P_aq index, indicating consistent regional hydroclimatic changes and shifts in aquatic versus terrestrial organic matter input. Variations in lake-level-sensitive GDGT parameters (e.g., %OH-GDGTs and %Cren) indicate pronounced changes in lake level, reflecting substantial variability in the lake water balance. Air temperature reconstructions derived from multiple independent proxies (MBT′_5ME, RI-OH, and U^K′₃₇) show broadly consistent long-term trends but differ in absolute values and variability. These differences likely reflect that the proxies record air temperature signals from different seasons or ecological contexts, with RI-OH and U^K’₃₇ representing mean annual air temperature, whereas MBT′_5ME are biased toward air temperatures during specific growth seasons. Such divergences point to enhanced climatic seasonality on the central TP. U^K’₃₇-derived temperature estimates indicate a sustained warming trend in the upper part of the sedimentary sequence, although LCAs were detected only in a limited number of samples within the upper ~100 m.

These preliminary results demonstrate excellent preservation of lipid biomarkers in the Lake Nam Co sediments and confirm their strong potential for long-term, high-resolution reconstructions of paleotemperature, hydroclimate, and seasonality. The Nam Co record thus provides a unique opportunity to investigate orbital-scale climate variability, monsoon–westerly interactions, and their impacts on lake systems and ecosystems on the Tibetan Plateau.