How temperature-dependent silicate weathering acts as Earth’s geological thermostat

Abstract

Earth’s climate may be stabilized over millennia by solubilization of atmospheric carbon dioxide (CO 2 ) as minerals weather, but the temperature sensitivity of this thermostat is poorly understood. We discovered that the temperature dependence of weathering expressed as an activation energy increases from laboratory to watershed as transport, clay precipitation, disaggregation, and fracturing increasingly couple to dissolution. A simple upscaling to the global system indicates that the temperature dependence decreases to ~22 kilojoules per mole because (i) the lack of runoff limits weathering and retains base metal cations on half the land surface and (ii) other landscapes are regolith-shielded and show little weathering response to temperature. By comparing weathering from laboratory to globe, we reconcile some aspects of kinetic and thermodynamic controls on CO 2 drawdown by natural or enhanced weathering.

Initial Validation of a Soil-Based Mass-Balance Approach for Empirical Monitoring of Enhanced Rock Weathering Rates

“…Our approach also directly overcomes possibly the largest uncertainty in scaling ERW in agricultural settings: estimating the initial extent of feedstock dissolution in soils (see, e.g., refs and ). There is currently significant uncertainty about how rock grain surface areas evolve through time within a given field setting (i.e., individual farm) and the extent to which secondary mineral formation on the surface of the feedstock has the potential to alter mineral dissolution rates (e.g., refs − ). In addition, bulk mineral dissolution kinetics are in some cases poorly constrained (e.g., refs , , and ).…”

“…In addition, bulk mineral dissolution kinetics are in some cases poorly constrained (e.g., refs , , and ). Taken together, these considerations make it extremely challenging to accurately forecast feedstock dissolution across a range of deployment regimes with existing reactive transport models alone. ,,− …”

Do Southeast Asia's paleo‐Antarctic trees cool the planet?

“…On geological time scales, carbon sequestration from silicate weathering and the burial of organic carbon approximately balances the atmospheric CO 2 contribution from volcanism and the weathering of organic‐rich sediments. Complex feedbacks are involved, based on increased weathering and CO 2 consumption resulting from higher p CO 2 and temperatures (Walker et al ., 1981; Gislason et al ., 2009; Brantley et al ., 2023) and the rate of exposure of fresh bedrock (Börker et al ., 2019).…”

Direct and indirect effects of the increase in atmospheric CO2and temperature on groundwater organisms

“…This increased CO 2 import will immediately lead to increased acidity which, in turn, will dissolve minerals, and thus, fuel weathering (for a summary of CO 2 -driven weathering, see Supplementary Information SI 1). In fact, in parallel to sea water acting (still) as a CO 2 sink, rock weathering under the consumption of CO 2 is regarded as one mechanism stabilizing earth’s climate (Brantley et al, 2023; Li et al, 2016). Such geochemical processes are estimated to have absorbed the equivalent of about half of the carbon dioxide that was emitted each year in the 2012-2021 decade (Friedlingstein et al, 2022).…”