Holocene cold events on the Tibetan Plateau

A lake sediment core from the eastern Tibetan Plateau was investigated by multi-proxy geochemical, sedimentological and magnetic analyses and its age determined using ¹⁴C AMS dating in an approach to use short-lived climate periods for a spatial assessment of the Holocene climate history on the Tibetan Plateau. Six cold events were identified from the Lake Ximencuo record which occurred between 10.3-10.0, 7.9-7.4, 5.9-5.5, 4.2-2.8, 1.7-1.3 and 0.6-0.1cal ka BP. A comparison with previously published Holocene records from lake and peat sections, ice cores and glacial remains of the Tibetan Plateau revealed that the cold event starting around 4.2cal ka BP had the most significant and widespread impact on almost all of the examined sites. This cold event lasted about a millennium in the western and central part of the Tibetan Plateau and possibly several hundred years longer at some sites in its eastern realm. The cold event inferred between 7.9 and 7.4cal ka BP from Lake Ximencuo was recorded at a number of sites on the eastern Tibetan Plateau too and probably corresponds to a cold event identified around 8.2cal ka BP at the sites on the western and central Tibetan Plateau. The coincidence with the 8.2ka event of the North Atlantic region implies that the latter exerted a significant environmental impact on the Tibetan Plateau too. The cold spell between 10.3 and 10.0cal ka BP was recorded at some marginal sites of the Tibetan Plateau but had apparently a less significant environmental impact. The more irregular pattern of cold events between about 7cal ka BP and the onset of the cold event after 4.2cal ka BP might be related to the catchment-specific response of the lake sediment and peat accumulation to the termination of the Holocene 'climatic optimum' on the Tibetan Plateau. The final two cold events between 1.7 and 1.3cal ka BP and in the last several hundred years representing the Little Ice Age are more widely seen on the Tibetan Plateau although they did not reach the significance of the cold event at 4.2cal ka BP. However, the three cold periods since 4.2cal ka BP are apparently coeval with the decline and establishment of Chinese Dynasties implying a remarkable impact on the social systems in eastern China. The consistent inference of cold events around 8.2cal ka BP or a few hundred years later and starting at 4.2cal ka BP is evidence for a temporary trans-regional climatic response on the Tibetan Plateau in the Holocene regardless of the catchment-specific response of complex natural systems.