Influence of Monsoon Climate on Chemical Weathering of Granitic Regoliths

Abstract

AbstractChemical weathering of silicates is a key process regulating global climate and biogeochemical cycles. However, little consensus has emerged on whether and how climate controls the chemical weathering of regolith. We present data on climate, geochemistry, and denudation rates of six low‐gradient granitic regoliths in the summer monsoon region. We used the time‐integrated Na loss rate (QNa) and chemical depletion fraction (CDF) to indicate plagioclase weathering and total weathering, respectively. Most profiles are primarily influenced by supply‐limited weathering (i.e., tectonic control on weathering), while the weak insignificant correlations between CDF or QNa and erosion rates or slopes suggest that tectonics and topography did not have the major control on weathering. In contrast, annual mean temperature (MAT) and annual mean water availability (MAP‐MAPET) strongly regulate weathering (QNa and CDF) exponentially, likely because of the approximately synergistic effects of temperature and water availability in the monsoon climate. The total sufficient monthly mean temperature (MMT) and monthly mean water availability (MMP‐MMPET) are utilized to further evaluate the relative influence of climate on CDF and QNa. The results suggest that total MMT and MMP‐MMPET both strongly influence CDF exponentially and linearly, respectively. However, total MMT and MMP‐MMPET show significant exponential correlations with QNa. The different effects of water availability imply that total weathering responding to variations in water availability is probably less sensitive than plagioclase weathering. The influence of climate on weathering on a large scale through MAT and MAP needs to be interpreted with caution due to the seasonal discrepancy of temperature and water availability.