苦海沉积物有机质反映的过去840年来青藏高原东部环境变化

Environmental Changes in Eastern Qinghai-Tibetan Plateau During the Last 840 Years Revealed by Organic Matters in Kuhai Lake Sediments

中文关键词:  有机质  苦 海  青藏高原  近千年  环境变化

英文关键词:Organic matters  Kuhai Lake  Qinghai-Tibetan plateau  The last millennium  Enviromental changes

中文摘要:

      青藏高原对全球气候变暖响应敏感,研究青藏高原近千年来环境演化过程、规律与驱动机制对预测其未来气候可能发生的变化有重要参照意义。通过位于青藏高原东部的苦海沉积物总有机质相关指标[总有机碳(TOC)、总氮(TN)、总有机碳与总氮比值(TOC/TN)和总有机碳同位素(δ¹³C_org)]的研究重建了该区域过去840年来的环境演化过程。研究结果表明,苦海沉积物中的有机质主要来自于湖泊内源水生植物。由于暖期(冷期)时黄河上游径流量较高(低),苦海水位随之升高(降低),湖泊水动力增强(减弱),浅水区沉水植物对研究岩芯中有机质的贡献率提高(降低),导致沉积物TOC、TN、TOC/TN升高,δ¹³C_org值正(负)偏。人类活动导致的青藏高原近50年气候异常变暖可能是~1950 AD之后δ¹³C_org反映的黄河上游径流量变化与重建的中国温度记录之间的关系发生转变的原因。苦海沉积物δ¹³C_org记录与万象洞石笋δ¹⁸O记录和太阳总辐射强度记录变化特征的相似性说明青藏高原东部地区气候变化的控制因素为太阳辐射驱动下的季风降雨量变化。

英文摘要:

      The Qinghai-Tibetan Plateau is particularly sensitive to global warming.It is of great importance to study environment evolution process,law and driving force of Qinghai-Tibetan Plateau during the last millennium for predicting future climate change.Total organic matter related proxies,including total organic carbon(TOC),total nitrogen(TN),the ratio of total organic carbon versus total nitrogen(TOC/TN),as well as carbon isotope of total organic matters(δ¹³C_org)of sediments from Kuhai Lake,a small saline lake located in eastern Qinghai-Tibetan Plateau,during the last 840 years were comprehensively analyzed.The results suggest that organic matters in Kuhai Lake sediments are mainly from aquatic plants within the lake and variation of δ¹³C_org is mainly controlled by lake level changes.When the climate was warmer(colder),runoff in the upper reaches of the Yellow River became higher(lower),which led to higher(lower)Kuhai Lake levels,enhanced(weakened)lake hydrodynamics,and hence higher(lower)contribution of submerged plants to TOC in the studied core and positive(negative)δ¹³C_org values for the sediments.Abnormal warming of Qinghai-Tibetan Plateau during the last 50 years cuased by human activities may account for reversed correlation between runoff in the upper reaches of the Yellow River since 1950 AD indicated by δ¹³C_org and reconstructed temperatures of China.Consistent variations among δ¹³C_org of Kuhai Lake sediments,δ¹⁸O of stalagmite from Wanxiang Cave and reconstructed total solar isolation indicate that environmental changes in eastern Qinghai-Tibetan Plateau was controlled by monsoon precipitation driven by solar isolation.