Abstract. The flow (flux) of climate-critical gases, such as carbon dioxide
(CO2), between the ocean and the atmosphere is a fundamental component
of our climate and an important driver of the biogeochemical systems within
the oceans. Therefore, the accurate calculation of these air–sea gas fluxes
is critical if we are to monitor the oceans and assess the impact that these
gases are having on Earth's climate and ecosystems. FluxEngine is an open-source software toolbox that allows users to easily perform calculations of
air–sea gas fluxes from model, in situ, and Earth observation data. The original
development and verification of the toolbox was described in a previous
publication. The toolbox has now been considerably updated to allow for its use
as a Python library, to enable simplified installation, to ensure verification of its
installation, to enable the handling of multiple sparingly soluble gases, and to enable the
greatly expanded functionality for supporting in situ dataset analyses. This new
functionality for supporting in situ analyses includes user-defined grids, time
periods and projections, the ability to reanalyse in situ CO2 data to a
common temperature dataset, and the ability to easily calculate gas fluxes
using in situ data from drifting buoys, fixed moorings, and research cruises. Here
we describe these new capabilities and demonstrate their application
through illustrative case studies. The first case study demonstrates the
workflow for accurately calculating CO2 fluxes using in situ data from four
research cruises from the Surface Ocean CO2 ATlas (SOCAT) database. The
second case study calculates air–sea CO2 fluxes using in situ data from a
fixed monitoring station in the Baltic Sea. The third case study focuses on
nitrous oxide (N2O) and, through a user-defined gas transfer
parameterisation, identifies that biological surfactants in the North
Atlantic could suppress individual N2O sea–air gas fluxes by up to
13 %. The fourth and final case study illustrates how a dissipation-based
gas transfer parameterisation can be implemented and used. The updated
version of the toolbox (version 3) and all documentation is now freely
available.