Westerly jet shifts over the last glacial cycle revealed by provenance of Japan Sea dust

Asian deserts are major sources of dust loading to the atmosphere, second only to those of North Africa. Today, dust activation in central and eastern Asia and convective rainfall over eastern China are preconditioned by the seasonal weakening of the Siberian High-Pressure system and migration of the Westerly Jet (WJ) northwards of the Tibetan Plateau during spring. Once activated, East Asian dust is transported over long distances to the North Pacific Ocean and to Greenland. Downcore records from locations on the dust transportation pathway provide valuable information about changes in past aridity and wind systems. Recent studies suggest that the westerlies were weaker and shifted towards more poleward latitudes than today during the warm Pliocene. However, the available data are too sparse to evaluate variability on glacial-interglacial timescales and often of questionable attribution (uncertain provenance). Here we report new downcore radiogenic isotope (Nd, Sr) records of dust provenance change over the last glacial cycle (150 kyrs to present) from the Japan Sea. Our records benefit from a thorough treatment protocol to remove the imprint of contaminating marine phases (including barite) and non-dust material and show remarkably clean glacial-interglacial structure. We report a marked shift in East Asian dust sources from glacial to interglacial conditions that has important implications for our understanding of the behaviour of the Siberian High-Pressure system and the westerly jet in response to changes in atmospheric carbon dioxide concentrations and ice sheet extent on geological timescales.