Characterizing Mean and Extreme Diurnal Variability of Ocean CO<sub>2</sub> System Variables Across Marine Environments
Olivier Torres, Lester Kwiatkowski, Adrienne J. Sutton, Narimane Dorey, James C. Orr
Abstract
Abstract Diurnal variability of ocean CO 2 system variables is poorly constrained. Here, this variability and its drivers are assessed using 3‐h observations collected over 8–140 months at 37 stations located in diverse marine environments. Extreme diurnal variability, that is, when the daily amplitude exceeds the 99 th percentile of diurnal variability, is comparable in magnitude to the seasonal amplitude and can surpass projected changes in mean states of p CO 2 and [H + ] over the twenty‐first century. At coastal sites and near coral reefs, extremes in diurnal amplitudes reach 187 ± 85 and 149 ± 106 μatm for p CO 2 , 0.21 ± 0.08 and 0.11 ± 0.07 for pH, and 1.2 ± 0.5 and 0.8 ± 0.4 for Ω arag , respectively. Extreme diurnal variability is weaker in the open ocean, but still reaches 47 ± 18 μatm for p CO 2 , 0.04 ± 0.01 for pH, and 0.25 ± 0.11 for Ω arag . Diurnal variability of the ocean CO 2 system is considerable and likely to respond to increasing CO 2 . Therefore, it should be represented in Earth system models.