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

The dry and windy Asian glacials during the mid-Pleistocene transition were probably due to the Northern Hemisphere ice sheet expansion, suggest records of grain size and magnetic susceptibility from the Chinese Loess Plateau and model simulations. The mid-Pleistocene transition 1.25 to 0.6 million years ago marked a major shift in global climate periodicity from 41,000 to around 100,000 years without a concomitant orbital forcing shift. Here, we investigate Asian climate dynamics associated with two extreme glacial loess coarsening events at the onset and middle of the mid-Pleistocene transition by combining new and existing grain size and magnetic susceptibility records from the Chinese Loess Plateau spanning the last 1.6 million years with general circulation model simulations. We find that the two extreme glacial events reflect exceptionally enhanced Asian aridification and winter monsoon activity. They coincided with notable Northern Hemisphere glacial ice sheet expansion at 1.25 and 0.9 million years ago when the 100,000-year periodicity initiated and intensified, respectively. Our results indicate that these anomalously dry and windy Asian glacials were probably driven by an amplified terrestrial climate response to the coincident Northern Hemisphere ice sheet expansion.