PyCO2SYS v1.8: marine carbonate system calculations in Python

Abstract. Oceanic dissolved inorganic carbon (TC) is the largest pool of that substantially interacts with atmosphere on human timescales. TC increasing through uptake anthropogenic dioxide (CO2), and seawater pH decreasing as a consequence. Both exchange CO2 between ocean response are governed by set parameters interact chemical equilibria, collectively known marine carbonate system. To investigate these processes, at least two system's typically measured – most commonly, from TC, total alkalinity (AT), pH, fugacity (fCO2; or its partial pressure, pCO2, dry-air mole fraction, xCO2) which remaining can be calculated equilibrium state solved. Several software tools exist to carry out calculations, but no fully functional rigorously validated tool written in Python, popular scientific programming language, was previously available. Here, we present PyCO2SYS, Python package intended fill this capability gap. We describe elements PyCO2SYS have been inherited existing CO2SYS family explain subsequent adjustments improvements. For example, uses automatic differentiation solve system calculate buffer factors, ensuring effect every modelled solute reaction accurately included all results. validate internal consistency tests comparisons against other software, showing produces results either virtually identical different for reasons, differences negligible practical purposes. discuss insights guided development PyCO2SYS: fact cannot unambiguously solved certain pairs parameters. Finally, consider potential future developments outlook solving The code distributed via GitHub (https://github.com/mvdh7/PyCO2SYS, last access: 23 December 2021) under GNU General Public License v3, archived Zenodo (Humphreys et al., 2021), documented online (https://pyco2sys.readthedocs.io/en/latest/, 2021).