Modeling the impact of explosive volcanism on biogeochemical cycling at the peak of the Late Paleozoic icehouse

Abstract

The peak of the Late Paleozoic Ice Age (LPIA) coincided with atmospheric carbon dioxide (pCO₂) lows, and large-magnitude fluctuations in glacial-interglacial pCO₂, but the driver(s) for pCO₂ drawdown at this time remain debated. Backed by parameters for the frequency and magnitude of Late Carboniferous volcanism derived from the rock record, we apply an intermediate complexity Earth system model to evaluate the biogeochemical impacts of ash-borne nutrients from frequent (decadal) and explosive silicic volcanism on nutrient cycling ca. 310–300 Ma. Results show that volcanic perturbations result in negligible changes in marine particulate organic carbon export concurrent with sustained increases in pCO₂ (+20 ppm), suggesting that volcanic pCO₂ emissions are not sequestered by fertilization and/or weathering of associated Fe-bearing volcanic ash. We propose that Fe loading in the Permo-Carboniferous may have been bolstered by abundant and highly reactive non-volcanic mineral dust. Future carbon cycle modeling of this interval should integrate the effects of high mineral dust loading with volcanically-induced high Fe solubilities to assess the resultant effects on biological productivity and consequent pCO₂ sequestration on scales sufficient to initiate or sustain cold climate modes during the lead-up to the peak LPIA. The Permo-Carboniferous world serves as a deep-time analog for understanding the novel mechanistic links among explosive volcanism, acidic atmospheric chemistry, nutrient availability in mineral aerosols, and organic carbon burial, with implications for Earth system responses to persistent biogeochemical forcings and Earth's future in a purposefully geoengineered world.