Contrasting megadrought episodes across the Mid-Brunhes Event in northwest China

Drought events seriously impact our society, yet the evolution of extreme drought events (megadroughts), and their mechanism(s), remain largely unknown. Here we used R_i/b ratio and BIT, two drought proxies based on the relative abundance of archaeal isoprenoid glycerol dialkyl glycerol tetraethers (isoGDGTs) vs. bacterial branched GDGTs (brGDGTs), to identify drought events on the Chinese Loess Plateau (CLP) since 700 thousand years (ka) ago. Droughts identified during the transition from glacial to interglacial climate states (glacial terminations) were much larger in amplitude after the Mid-Brunhes Event (MBE) than before the MBE, consistent with a transition from generally colder to warmer interglacial conditions reconstructed from bacterial brGDGTs due to higher atmospheric pCO₂ and weakened tropical Pacific Sea surface temperature gradients. The post-MBE shift to higher temperatures is somewhat analogous to the recent global warming trend, suggesting more extreme drought events are likely to occur in the future in NW China.