Quantitative reconstruction of the paleosalinity at Qinghai Lake in the past 900 years

Abstract

Based on the function relationship between the shell length ofLimnocythere inopinata and the salinity of its living water in Tibetan Plateau lakes, the paleosalinty of Qinghai Lake in the past 900 years was reconstructed through the measurement of the adult body length ofLimnocythere inopinata. Meanwhile, the paleosalinity sequence of Qinghai Lake during the same period was rebuilt by the Sr/Ca ratio of the shell ofEucypris inflata combined with the Sr/Ca ratio of living ostracod valves from the species of genusEucypris inflata and the host water. The paleosalinity results obtained by two different methods were compared and assessed in this paper. To check the result, it was also contrasted with other historical climatic sequences of this area including tree ring and ice core. It was shown that the paleosalinity sequence rebuilt by adult ostracod body length had high reliability, and the paleosalinity reconstruction method by trace elements of ostracod shells was not suitable for Qinghai Lake. From the reconstructed paleosalinty sequence of Qinghai Lake, it can be found that low salinity during 1160–1290 AD showed the humid climate condition on the Mediaeval Warm Period in this area, while the high salinity during 1410–1540 AD, 1610–1670 AD and 1770–1850 AD which was corresponding to the three cold pulses of the Little Ice Age with a dry climate condition. And the high salinity in the latest several decades was consistent with recent warm and dry trends of the climate in this area. The good consistency of the reconstructed palaeosalinity sequence and the precipitation sequence in this area rebuilt by tree ring proves the reconstruction of past lake salinity is reliable.