Temperature variations over the past 600 years documented by a <italic>δ</italic><sup> 13</sup>C record from terrestrial plant remains from Kanas Lake, Altai Mountains, Northwestern China

Arid central Asia (ACA) is characterized by relatively dry climates and fragile ecosystems, which restrict the survival and development of human beings. A full understanding of the climatic and environmental evolution in the region is not only significant for the thorough understanding of global climate change, but is of importance for the sustainable development of the area as well, especially in the context of ongoing global warming. The Altai Mountains are located in the central part of the ACA and numerous lakes are distributed in the Mountains. Kanas Lake, one of the largest lake in the Altai Mountains of Northwestern China, is surrounded by dense forests. The climate of the area is characterized by relatively abundant precipitation and cold temperatures and the vegetations are very sensitive to climate changes. Recent temperature reconstructions based on the width and short-term series of carbon isotopes of tree-rings from the area did not exhibit an obvious warming trend during the past century. This result is unexpected in the context of ongoing global warming, but it remains uncertain whether the regional climate did not response to global warming due to complex unknown processes, or whether the tree-ring data did not record the signal of long-term warming. A 81-cm-long sediment core (KNS15E) was recovered from a water depth of 29 m near the lakeside of Kanas Lake using a modified piston corer. Here we present the results of stable carbon isotope analysis of a sequence of C3 terrestrial plant remains from core KNS15E. A chronology is constructed from five AMS 14C dates from wood fragments (twigs) and it reveals that the whole core spans the past 570 years. From the context of the sampling site, the soil of the adjacent forest would have been well-supplied with water from rainfall and snowmelt from the mountains which would have been supplied to site as ground water. In addition, based on the previous studies of carbon isotopes of tree-rings and of α -cellulose of sedge plants, the δ 13C variations are likely to be mainly related to temperature changes. The raw δ 13C values are corrected to pre-industrial values to account for changes in the δ 13C value of atmospheric CO2 and for changes in CO2 concentration. The stable carbon isotope record provides a record of temperature changes over the last 570 years which can be clearly divided into the Little Ice Age and the Current Warm Period. The temperature increased continuously since the early 19th century and the 20th century was the warmest period in the sequence. The temperature variations revealed in our study are consistent with temperature reconstructions from ice cores, tree-rings and from Teletskoe Lake in the Russian Altai, as well as with the extratropical NH mean temperature record. In addition, a trend of decreasing temperature is indicated by the decreasing stable carbon isotope ratios of both bulk plant remains and conifer needles in the upper part of the core, which corresponds with the widely-reported phenomenon of a hiatus in global warming in central Asia and with meteorological data from the study region.