Northern Hemisphere ice sheet expansion intensified Asian aridification and the winter monsoon across the mid-Pleistocene transition

Abstract The mid-Pleistocene transition (MPT) from ~ 1.25 to ~ 0.6 million years ago (Ma) marked a major shift in periodicity of Earth’s climate variability from dominantly ~ 40- to ~ 100-thousand years (kyr) without a concomitant shift in orbital forcing. Here we advance understanding of Asian climate dynamics associated with two glacial extreme loess coarsening events that are recorded across the Chinese Loess Plateau (CLP) at the onset and middle of the MPT. This is based on a combination of new and existing millennial-resolution grain size and magnetic susceptibility records for the last 1.6 million years from the CLP and general circulation model simulations, viewed within a global palaeoclimatological context. We find that the two extreme glacial events reflect exceptionally enhanced Asian aridification and winter monsoon activity. They occurred at times of notable Northern Hemisphere glacial ice sheet expansion, when the ~ 100-kyr glacial cyclicity initiated and intensified at marine isotope stages 38 and 22 (~ 1.25 and ~ 0.9 Ma), respectively. Our integration of palaeoclimate data and climate model simulations indicates that these anomalously cold, dry, and windy Asian glacials were driven by amplified, non-linear regional threshold responses to phases of Northern Hemisphere ice sheet expansion.