Using Kgen to Generate Cross-Verified Apparent Equilibrium Constants (K∗’s) for Palaeoseawater Carbonate Chemistry

Abstract

Quantification of palaeo pH and palaeo CO₂ from marine proxies requires the use of apparent equilibrium constants (K^∗’s). The K^∗’s required to calculate seawater carbonate chemistry are described by empirically determined calibrations, and for palaeoseawater these calibrations must be adjusted to account for changes in seawater composition. There are a number of possible calibrations that can be used to calculate K^∗’s, and each software package for calculating carbonate chemistry separately implements these K^∗ calibrations, which are manually verified against previous implementations. Palaeo applications typically only implement a single calibration for each K^∗, but have additional complexity from the need to adjust each calibration for changing seawater composition through time. The fragmented approach to K^∗ calculation can result in unintended and difficult to resolve discrepancies between outputs calculated by different pieces of software. We present “Kgen,” a synchronised collection of three pieces of software to consistently calculate palaeoseawater K^∗’s in Python, R, and Matlab. Kgen provides a simple, and nearly identical interface in each language. Through use of a Continuous Integration/Continuous Delivery (CI/CD) pipeline, Kgen guarantees consistent outputs between languages by automatically cross-checking results from all three implementations. Unifying the approach to K^∗ calculation in this way provides an extensible platform for verifiable K^∗ generation for palaeoseawater, which can be integrated into existing carbon speciation calculators to improve the consistency of results.