Abstract ID: 3.13326 | Accepted as Talk | Talk | TBA | TBA

On the eastern Tibetan plateau (TP), Little Ice Age (LIA) glacier advances reached far below the upper tree line. This provides unique opportunities to study the contact zone of mountain forests and glaciers, to use tree-ring data to provide dating control for glacier history, and utilize tree-ring based climate reconstrutions for the assignment of glacier responses to changes in the temperature and moisture regime. Furhermore, such a setting enables us to study the response of mountain forest ecosystems to coupled impacts of recent climate induced environmental changes. We studied several glacier forefields in a series of mountain ranges, namely Gongga Shan, Hengduan Shan, and the heavily glaciated mountain ranges north of the Yarlung Tsangpo river in the southern TP. Tree age-derived moraine dating revealed a high consistently of minimum ages of maximum LIA glacier advances between CE 1760-1785, although also older glacier morain deposits were found. Moraines of recessional stages date from the early (1820s-1830s) and late (1870s to 188s) 19th century as well as from the early 20th century (1920s). From each glacier system, we analyzed tree-ring oxygen isotope (δ¹⁸O) records, which were used to reconstruct variations in the hydroclimate and maximum latewood density (MXD) as a proxy for summer temperature. The derived summer temperature reconstruction revealed that the temperature depression of ca. 1°C during the LIA maximum (around 1600-1750 CE) provided the background for a general decline in equilibrium line altitude of regional galciers, leading to subsequent glacier advances. δ¹⁸O-baased moisture reconstructions revealed that local glacier advances can be assigned to temporal variations of increased moisture availability. Long-term drying trends of decreased summer monsoon activity as well as multi-decadal moisture variability are widely consistent over the whole study area. However, backward trajectory analyses of climatic extreme event years indicate that differences in air mass origin and therefore moisture regimes are evident in different parts of the southern and eastern TP, ponting to the influence of regional transport pathways influencing forest ecosystems and regional glacier mass balance. If the observed trend of monsoonal activity bility will further continue, we expect a significant impact on Asian high mountain forest ecosystems.