Contrasting weathering dynamics within continents during the past glacial cycles

Chemical weathering of the continental rocks exerts a dominant force on atmospheric CO₂ levels and global climate. How continental weathering works during the Quaternary cooling on glacial-interglacial scales is still poorly understood. Here we reconstructed continental weathering history over the past 800 kyr in a High-Mountain Asia catchment impacted by glaciers. The ⁸⁷Sr/⁸⁶Sr ratio of lake water, a proxy of catchment weathering, was lower during interglacials while it was higher during glacials and cold stages of interglacials. This higher level in ⁸⁷Sr/⁸⁶Sr ratio is assumed to be caused by a glacier-forced release of radiogenic strontium from reactive minerals.

Conversely, ⁸⁷Sr/⁸⁶Sr ratio of weathering solution in the Chinese Loess Plateau, a non-glaciated region, displayed lower values during glacials (loess formation) and higher values during interglacials (paleosol formation), which is modulated by temperature dominance of mineral weathering rate. Such contrasting weathering dynamics in glaciated and non-glaciated regions suggest that ⁸⁷Sr/⁸⁶Sr ratios of river water delivered into the ocean would be greatly buffered by the contrasting Sr release regimes within continents. This process may limit seawater ⁸⁷Sr/⁸⁶Sr variation within a narrow range on glacial-interglacial time scales and provide a novel indicator for tracing the onset of glacial development during the deep past.