Decoupling Kinetic and Hydrological Controls on Global Silicate Weathering via a Stratified Observational Factorial Framework

Arpan Halder 

The chemical weathering of continental silicate rocks is a primary geological mechanism for long-term atmospheric CO₂ sequestration and climate stabilization. However, a longstanding scientific debate persists regarding whether global silicate weathering is fundamentally driven by temperature (kinetic limits) or by physical erosion and hydrology (transport and flushing limits). Resolving this debate empirically on a global scale has historically been hindered by the inherent statistical covariance of Earth's climate, where temperature and precipitation strongly correlate. To reduce the confounding associated with temperature-precipitation collinearity, we apply an observational Design of Experiments (DoE) factorial framework to global river sediment observations. Utilizing curated, peer-reviewed global benchmark compilations (Deng et al., 2022; GloRiSe v1.1) harmonized with WorldClim v2.1 high-resolution bioclimatic grids, we categorized n = 5,292 modern river sediment samples into discrete climate quadrants based on dataset median thresholds (MAT = 11.23°C, MAP = 941 mm/yr). A Two-Way Analysis of Variance (ANOVA) on the Chemical Index of Alteration (CIA) and the carbonate-free CIX formally estimated conditional contrasts and effect sizes (partial eta-squared, η²_p) between temperature and precipitation classes. Our results demonstrate that temperature produces the dominant contrast in weathering intensity (η²_p = 0.0347, F = 190.17, p < 0.0001), while precipitation acts as a secondary, highly consistent driver (η²_p = 0.0257, F = 139.61, p < 0.0001). Crucially, the interaction term yields an effect size that is an order of magnitude smaller (η²_p = 0.0024) and is statistically non-significant in the CIX formulation (p = 0.0891, η²_p = 0.0005). The parallel conditional slopes confirm that thermodynamic and hydrological drivers behave in an approximately additive manner within modern continental sediment arrays, providing empirical constraints for Earth System Models.