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Knowledge of calcite dissolution kinetics 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 calcite dissolution kinetics in seawater. We measured the dissolution rates of 13 C-labeled calcite in seawater at 5, 12, 21, and 37°C across the full range of saturation states (0 < Ω = < 1). We show that the dissolution rate is non-linearly dependent on Ω and that the degree of non-linearity both increases with temperature, and changes abruptly at "critical" saturation states (Ωcrit). The traditional exponential rate law most often utilized in the oceanographic community, R=k(1-Ω) n , requires different fits to k and n depending upon the degree of undersaturation. Though we

The marine calcium carbonate (CaCO 3 ) cycle is integral to the global carbon cycle. The production of biogenic CaCO 3 tends to raise atmospheric CO 2 due to consumption of surface ocean alkalinity, while the ballasting of organic matter and export into the deep ocean provided by this material tends to lower CO