Calcium carbonate dissolution is the dominant negative feedback in the ocean for neutralizing the acidity from rising atmospheric carbon dioxide. Mimicking this natural process, the accelerated weathering of limestone (AWL) can store carbon as bicarbonate in the ocean for tens of thousands of years. Here, we evaluate the potential of AWL on ships as a…

We present a novel determination of the dissolution kinetics of inorganic calcite in seawater. We dissolved 13C-labeled calcite in unlabeled seawater, and traced the evolving δ13C composition of the fluid over time to establish dissolution rates. This method provides sensitive determinations of dissolution rate, which we couple with tight constraints on both seawater saturation state and surface area of the dissolving minerals.…

Near-equilibrium calcite dissolution in seawater contributes significantly to the regulation of atmospheric CO2 on 1,000-y timescales. Despite many studies on far-from-equilibrium dissolution, little is known about the detailed mechanisms responsible for calcite dissolution in seawater. In this paper, we dissolve 13C-labeled calcites in natural seawater. We show that the time-evolving enrichment of 𝜹13C in solution is a direct measure of…

This study provides laboratory data of calcite dissolution rate as a function of seawater undersaturation state (1 − Ω) under variable pressure. 13C-labeled calcite was dissolved in unlabeled seawater and the evolving δ13C composition of the fluid was monitored over time to evaluate the dissolution rate. Results show that dissolution rates are enhanced by a factor of 2–4 at 700 dbar compared…

Knowledge of the mechanism of calcite dissolution in seawater is a critical component of our understanding of the changing global carbon budget. Towards this goal, we provide the first measurements of the temperature dependence of seawatercalcite dissolution kinetics. We measured the dissolution rates of 13C-labeled calcite in seawater at 5, 12, 21, and 37 °C across the full range of saturation states 0<Ω=Ca2+[CO32-]Ksp'<1. We show that the dissolution rate is non-linearly dependent…

Ocean acidification from fossil fuel burning is lowering the mean global ocean saturation state (Ω = Ca2+CO32−Ksp′), thus increasing the thermodynamic driving force for calcium carbonate minerals to dissolve. This dissolution process will eventually neutralize the input of anthropogenic CO2, but the relationship between Ω and calcite dissolution rates in seawater is still debated. Recent advances have also revealed that spectrophotometric measurements of…

We present the first examination of calcite dissolution in seawater using Atomic Force Microscopy (AFM). We quantify step retreat velocity and etch pit density to compare dissolution in seawater to low ionic strength water, and also to compare calcite dissolution under AFM conditions to those conducted in bulk solution experiments (e.g. Subhas et al., 2015, Dong et al., 2018). Bulk dissolution rates and step retreat velocities are slower at high and…

Abstract The dissolution of CaCO3 minerals in the ocean is a fundamental part of the marine alkalinity and carbon cycles. While there have been decades of work aimed at deriving the relationship between dissolution rate and mineral saturation state (a so-called rate law), no real consensus has been reached. There are disagreements between laboratory- and field-based…

Carbonic anhydrase (CA) has been shown to promote calcite dissolution (Liu, 2001, https://doi.org/10.1111/j.1755-6724.2001.tb00531.x; Subhas et al., 2017, https://doi.org/10.1073/pnas.1703604114), and understanding the catalytic mechanism will facilitate our understanding of the oceanic alkalinity cycle. We use atomic force microscopy (AFM) to directly observe calcite dissolution in CA-bearing solution. CA is found to etch the calcite surface only when in…