Upper Irtysh River flow since AD 1500 as reconstructed by tree rings, reveals the hydroclimatic signal of inner Asia

In a warming world, water scarcity is one of the main concerns for sustainable development and human well-being in inner Asia. Due to the lack of instrumental streamflow records, the natural variability of the water supply from inner Asian rivers is not well understood from a long-term perspective. Here, we have reconstructed the streamflow of Upper Irtysh River from AD 1500 to 2010, based on the tree-ring width indices of spruce (Picea obovata) and larch (Larix sibirica) from the Altay Mountains. The reconstruction explains 48.4 % of the recorded streamflow variance over the common period 1958–2008. This streamflow reconstruction is representative of regional moisture conditions over the Irtysh River basin area. Some significant spectral peaks are identified, and suggest the influence of natural forcing on the streamflow of the Upper Irtysh River, such as ENSO and solar activity. The linkages of our reconstruction with sea surface temperature in the northern Indian Ocean, eastern equatorial Pacific Ocean, and equatorial Atlantic Ocean suggest the connection of regional streamflow variations to large-scale atmospheric circulation. We also find that there is the relationship between regional drought/streamflow variations in inner Asia and the interaction of the mid-latitude Westerlies and Asian summer monsoon. Our 511-year streamflow reconstruction provides a long-term perspective on current and twentieth century wet and dry events in the Irtysh River basin, is useful to guide predictions of future variability, and aids future water resource management.