第八届青年地学论坛

Knowledge of multi-centennial-scale climate variation and their impact on lake aquatic ecosystems over the past 2000 years is crucial for evaluating the key driving factors affecting these ecosystems and for predicting the potential changes that may occur in response to recent global warming scenarios. Despite the significance of multi-centennial-scale climate variations on lake aquatic ecosystems, our understanding of the climate patterns, including temperature and hydrology variations, during the Common Era in the Tibetan Plateau (TP) remains inadequate. This knowledge gap hinders our ability to fully comprehend the impact of climate change on lake ecosystems. In this study, we present a quantitative temperature record, along with sedimentary data from a non-glacial, meltwater-fed lake sediment archive in the interior of the Tibetan Plateau (TP), in order to track climate changes and variations in aquatic productivity over the past two millennia. Our results show that the temperature derived from branched glycerol dialkyl glycerol tetraethers (brGDGTs) displays a cooling trend overall, with multi-centennial-scale fluctuations in temperature. These include a relatively warm period during the so-called Roman Warm Period (-200-490 AD), followed by a cold period centered around 500-1000 AD, a warm period during the Medieval Climate Anomaly (1050-1410 AD), a cooling interval during the Little Ice Age (1470-1900 AD), and a rapid warming trend since 1900 AD, which coincides with Current Warm Period. The grain-size data reflect variations in lake level that are related to the Summer Monsoon (SM) over the Bamu Co catchment. Lake level record indicates several periods when the lake shrank, centered at -125 AD, 416 AD, 779 AD, 1762 AD, and others. The Bamu Co paleoproductivity shows similarities with paleoclimate records, suggesting that millennial-scale aquatic productivity was influenced by both temperature and lake hydrology conditions. Warmer and deeper lake conditions are conducive to the flourishing of aquatic macrophytes, which primarily accumulate lake productivity. The variability of climate and its effects on aquatic productivity responses in Bamu Co also support the recent warming and humidification of the TP interior and generally better changes in the ecosystem.
 

brGDGTs; temperature reconstructions; lake level; lake productivity; central Tibetan Plateau; the Common Era