Comparison of ten packages that compute ocean carbonate chemistry

[摘要] Marine scientists often use two measured or modeled carbonate systemvariables to compute others.These carbonate chemistrycalculations, based on well-known thermodynamic equilibria, are nowavailable in a dozen public packages.Ten of those were comparedusing common input data and the set of equilibrium constantsrecommended for best practices.Current versions of all 10 packagesagree within 0.2 μatm for pCO₂, 0.0002 unitsfor pH, and 0.1 μmol kg⁻¹ for CO₃²⁻ interms of surface zonal-mean values. That represents more than a10-fold improvement relative to outdated versions of the samepackages.Differences between packages grow with depth for somecomputed variables but remain small.Discrepancies derive largelyfrom differences in equilibrium constants.Analysis of thesensitivity of each computed variable to changes in each constantreveals the general dominance of K₁ and K₂but also the comparable sensitivity to K_B for theA_T–C_T input pair.Best-practiceformulations for K₁ and K₂ are implementedconsistently among packages.Yet with more recent formulationsdesigned to cover a wider range of salinity, packages disagree by upto 8 μatm in pCO₂, 0.006 units in pH, and1 μmol kg⁻¹ in CO₃²⁻ under typical surfaceconditions.They use different proposed sets of coefficients forthese formulations, all of which are inconsistent.Users would dowell to use up-to-date versions of packages and the constantsrecommended for best practices.

[学科分类] 地球化学与岩石