Destabilizing the Earth’s thermostat: Riverine alkalinity responses to climate change

Alkalinity generation from rock weathering is thought to modulate the Earth’s climate at geological time scales. Here, we use global alkalinity data paired with consistent measurements of erosion rates to develop an empirically-based model for riverine alkalinity concentration, demonstrating the impact of both erosion (i.e. erosion rate) and climate (i.e. temperature) on alkalinity generation, globally. We show that alkalinity generation from carbonate rocks is very responsive to temperature and that the weathering flux to the ocean will be significantly altered by climate warming as early as the end of this century, constituting a sudden feedback of ocean CO₂ sequestration to climate. While we anticipate that climate warming under a low emissions scenario will induce a reduction in terrestrial alkalinity flux for mid-latitudes (-1.3 t(bicarbonate) a^-1 km^-2) until the end of the century, resulting in a temporary reduction in CO₂ sequestration, we expect an increase (+1.6 t(bicarbonate) a^-1 km^-2) under a high emissions scenario, causing an additional short-term CO₂ sink at decadal timescales.