Snowline elevation and eolian dust flux in the Japanese Islands during Isotope Stages 2 and 4

Abstract

Abstract Changes in snowline elevation and dust flux clearly contrast the paleoenvironments of the Japanese Islands during Isotope Stages 2 and 4. A lower snowline elevation and a smaller dust flux during Isotope Stage 4 suggests a climate with a cold and dry summer dominated by winter monsoonal precipitation between 70 and 55 ka. A higher snowline elevation and a larger dust flux during Isotope Stage 2 indicates a climate with a cold and very dry summer with a minimized winter monsoon precipitation especially around 18 ka. A drier climate during Stage 2 can be explained by (1) a lowering of sea surface temperature in the Japan Sea by blocking the warm Tsushima Current during a sea-level lowering; (2) the extension of sea ice over the northern part of the Japan Sea and the Sea of Okhotsk; and (3) weakening of the summer monsoon and the southern migration of the polar front. The increase in dust flux in both Stages 2 and 4 suggests an intensification of westerlies and winter monsoon during these stages. A bigger dust flux in Stage 2 than Stage 4 reflects (1) stronger westerlies and winter monsoon, and (2) the emergence of continental shelf which became an important dust source.