Reading the Record of Lakes: What Ostracods Tell Us About Central Asian Changing Environments

Understanding past variability of the Asian monsoon system is essential for constraining its sensitivity to ongoing and future climate change. High Asia, encompassing the Tibetan Plateau and surrounding regions of China, Nepal, and Mongolia, represents a key area where the Indian Summer Monsoon, East Asian Summer Monsoon, and mid-latitude westerlies interact. This contribution synthesizes paleoclimate reconstructions from this region with a primary focus on lacustrine ostracod records, complemented by a wide range of established climate proxies reported in the literature, including pollen, diatoms, sedimentological indicators, geochemical proxies, loess sequences, and ice-core records. Central Asia is selected to provide a broader atmospheric and hydrological context, though the emphasis remains on monsoon-influenced regions to the south and east.

Ostracods are particularly valuable paleoclimate indicators due to their sensitivity to changes in temperature, salinity and generally lake-water chemistry. Variations in ostracod assemblage composition, species diversity, and stable isotope and elemental geochemistry (δ¹⁸O, δ¹³C, Mg/Ca, Sr/Ca) are used to infer past effective moisture and monsoon intensity. These records are evaluated alongside pollen-based vegetation reconstructions and sedimentary evidence for lake-level fluctuations, allowing for a robust, multiproxy assessment of regional climate evolution from the late Pleistocene through the Holocene.

The compiled records reveal strong spatial and temporal heterogeneity in monsoon behavior across High Asia. Periods of enhanced monsoon activity are generally associated with expanded lakes, lower salinity, increased ostracod diversity, and forest or grassland pollen taxa, whereas weakened monsoon phases correspond to salinity-tolerant ostracod assemblages, steppe-dominated vegetation, and increased aridity, particularly in Mongolia and northern Tibet.