PyCO2SYS: marine carbonate system calculations in Python

PyCO2SYS is a Python toolbox for solving the marine carbonate system and calculating related seawater properties. Its core is a Python implementation of CO2SYS for MATLAB. Documentation is available at PyCO2SYS.rtfd.io. Changes in v1.4.0 New features Added uncertainty module with functions to evaluate derivatives of PyCO2SYS outputs with respect to inputs, along with corresponding documentation. Specific input values can optionally be provided for all total concentrations and equilibrium constants that are estimated internally from salinity, temperature and pressure. General improvements Added basic sanity checking to prevent some invalid marine carbonate system parameter input values. Nutrient concentrations have always been set to zero internally for K1K2CONSTANTS options 6 and 8, and salinity too for 8, regardless of the input values. This is now reflected in the output values of these variables in the CO2dict. New outputs Substrate:inhibitor ratio (SIR) of B15, calculated with SIratio in new module bio. Inputs PAR1 and PAR2. The "Peng correction" factor. The fugacity factor for converting between CO2 partial pressure and fugacity. The activity coefficient of the H+ ion for NBS pH scale conversions. Validation Calculations compare very favourably against the forthcoming CO2SYS for MATLAB v3 - see the validation documentation for a discussion of the results