Investigation of the spatio-temporal variability in Eurasian Late Quaternary loess–paleosol sequences using a coupled atmosphere–ocean general circulation model

Loess–paleosol sequences from across the Asian interior indicate that Late Quaternary glacial periods were primarily characterized by loess deposition, although in some regions weakly developed paleosols also developed. During interglacial periods, paleosol formation dominated in most, but not all, areas. Possible reasons for this complex spatio-temporal variability of loess–paleosol deposition are investigated through the use of a coupled atmosphere–ocean general circulation model configured for the Last Glacial Maximum (LGM) and for the early–mid-Holocene. Downstream modification of the westerly trade winds by the Fennoscandian ice sheet affected climate means across much of the Asian interior. In particular, weaker horizontal winds, enhanced atmospheric subsidence, and significantly reduced moisture transport combined to dry the continental interior to such a degree that there was a northeastward expansion of the cool, semi-arid, B-climate zone of the Koppen classification. Orographic precipitation triggered by the Fennoscandian ice sheet, however, increased precipitation and snow melt amounts in the proximity of the ice sheet margin. Glacial climate over the Chinese Loess Plateau, on the other hand, was less susceptible to downstream effects and was determined primarily by changes in the south Asian monsoon. During the more seasonal early Holocene, there were latitude-dependent changes in soil moisture, with significant wetting across low-mid-latitudes and drying in the mid-high latitudes of the Siberian Plain. Our simulated spatio-temporal variability of the hydrological cycle may, therefore, give insight into the interpretation of the complex sediment records from the Asian interior that serve as proxies for paleoclimatic reconstructions.