Loess weathering as an important contributor to the glacial atmospheric pCO2 drawdown

Loess deposits are silt sediments that can contain up to 30% carbon. As they are transported into the ocean, whether by wind or by rivers, they can increase the ocean's alkalinity. Recent studies have reported that accounting for the carbon weathering of loess under glacial conditions could increase the global alkalinity flux by more than 50% compared with previous estimates. This, in turn, could lower atmospheric CO₂ concentrations by increasing the ocean's buffering capacity. To test this hypothesis in a transient Earth System Modeling framework and quantify the role of loess weathering in orbital-scale global carbon reorganizations, we employed the cGENIE model, nudged the ocean circulation state to a previously conducted transient 3 Ma CESM1.2 simulation, and applied various loess weathering scenarios. Our results suggest that plausible estimates of loess-derived carbon fluxes can explain a considerable fraction of interglacial/glacial CO₂ variability during the last 1 Ma.