Evaluating the Impact of Paleogeographic Reconstructions on Phanerozoic Climate Simulations and Carbon Cycle Dynamics

Over the course of the Phanerozoic, Earth’s climate has alternated between greenhouse and icehouse regimes, driven in large part by shifts in continental configurations that influence weathering processes and, consequently, the global climate. Geodynamic factors play a critical role in these shifts, and intermediate-complexity Earth System Models provide an effective means of exploring the associated parameter spaces. These models rely on topographic boundary conditions derived from paleogeographic reconstructions, where elevation and slope significantly affect silicate weathering intensities. However, different methodologies for reconstructing paleogeographies can yield markedly different results. Among these, the digital elevation maps by Scotese and Wright (2018) are widely used, despite notable discrepancies compared to alternative reconstructions.

To evaluate the impact of paleogeographic reconstructions on climate model simulations, we compared the outcomes of PlaSim-GENIE simulations for 45 time slices across the Phanerozoic, using both Paleomap and PANALESIS (Vérard, 2019) digital elevation models (DEMs). These simulations, covering pCO₂ levels from 0.25 to 16 times pre-industrial atmospheric concentrations (280 ppm), were used to generate lookup tables for the spatially resolved global carbon cycle model SCION (Mills et al., 2022). This approach allowed us to investigate a broad parameter space of potential drivers for climatic shifts throughout the Phanerozoic.

Preliminary results indicate that incorporating degassing forcing from the PANALESIS paleogeography enables even simple inorganic carbon cycle box models to more closely replicate atmospheric CO₂ variations inferred from proxy records. Furthermore, climate simulations using PANALESIS paleogeography within SCION more successfully capture the Hirnantian Glaciation, whereas simulations constrained by PaleoMap reconstructions produce pCO₂ levels that are too high to align with the observed glaciation during this period. The identified differences may be related to a more robust treatment of plate boundaries evolution in PANALESIS, which is based on plate tectonic rules.

References

Mills, B. J., Donnadieu, Y., & Goddéris, Y. (2021). Spatial continuous integration of Phanerozoic global biogeochemistry and climate. Gondwana Research, 100, 73-86.

Scotese, C. R., & Wright, N. (2018). PALEOMAP paleodigital elevation models (PaleoDEMS) for the Phanerozoic. Paleomap Proj.

Vérard C. (2019.b). PANALESIS: Towards global synthetic palæogeographies using integration and coupling of manifold models. Geological Magazine, 156 (2), 320-330; doi:10.1017/S0016756817001042.