Late Paleozoic climate transition from a long-term carbon cycle modeling perspective

Abstract

The Late Paleozoic ice age (LPIA) is the longest-lived Phanerozoic icehouse climate and the only recorded greenhouse–icehouse–greenhouse cycle on a vegetated Earth. Sedimentary archives partially detail the glaciation events, but the reasons and timing of the LPIA's onset (∼330 Ma) and end (∼260 Ma) remain debated. In many models, the shift to icehouse conditions is linked to enhanced CO₂ uptake through silicate weathering, but the causes of this increased carbon sink are unclear. Most carbon cycle models are limited by their non-dimensional nature, and spatially resolved models rely heavily on variables such as topography and bathymetry, which are difficult to constrain over time. This study investigates the influence of weatherability reconstructions in non-dimensional versus spatially resolved models in the context of the LPIA's onset and ending. We review constraints on simulated silicate weathering fluxes and test forcings affecting its rate. Our paleogeographic forcing review uses newly developed land-maps and reconstructed climatic belts to constrain weathering based on fossil paleo-indicators. Our findings suggest that increased land availability in the high weatherability zones (HWZ) led to enhanced weathering processes, likely contributing to the glaciation onset. However, when a high solid Earth degassing factor is included, the likelihood of an extensive glaciation diminishes, indicating the need for an intensified CO₂ sink driven by higher erosion rates and associated chemical weathering tied to topographic elevation to instigate widespread glaciation. A reduction in available land for weathering in the HWZ appears to have a determining role in the LPIA's termination.