Abstract
Many ocean and climate models output ocean variables (like velocity,
temperature, oxygen concentration etc.) in depth space. Property
transport in the ocean generally follows isopycnals, but isopycnals
often move up and down in depth space. A small difference in the
vertical location of isopycnals between experiments can cause a large
apparent difference in ocean properties when the experiments are
compared in depth space. As a result, it is often useful to compare
ocean variables in density space. This work compares two algorithms for
plotting ocean properties in density coordinates, one written in FORTRAN
with a python wrapper (xlayers), and one written in python
(xarrayutils). Both algorithms conserve total salt content in the
vertical, and both algorithms are easily parallelizable to enable
plotting large datasets in density coordinates. We apply these
algorithms to plot salinity in density space in some of the CMIP-6
models. In general, areas with net precipitation today experience
increasing precipitation in higher greenhouse-gas scenarios, and areas
with net evaporation today experience a further reduction in net
precipitation in higher greenhouse-gas scenarios. By plotting salinity
in density space, we visualize how changes in evaporation and
precipitation at the surface propagate along isopycnals to influence
salinity concentrations in the ocean interior.