Introduction

The Water Mass Transformation (WMT) framework was initially put forward by Walin (1982) to describe the relationship between surface heat fluxes and interior ocean circulation (building on his earlier paper on salinity transformations in estuaries). A series of studies further refined the framework to include the effect of haline-driven buoyancy forcing (e.g., Tziperman 1986; Speer and Tziperman, 1992) and account for the role of interior mixing (e.g., Nurser et al., 1999; Iudicone et al., 2008). A comprehensive overview of past studies in WMT and details of how WMT is derived from diapycnal processes can be found in Groeskamp et al. 2019.

A detailed account of best practices for computing full Water Mass Budgets (WMB) in finite-volume ocean models is given by Drake et al. 2025, which was written alongside this package. This package enables comprehensive calculations of water mass transformation budges. Transformation rates are computed using companion package NOAA-GFDL/xwmt, overturning transports are computed using MOM6-community/sectionate and hdrake/regionate, and all other terms in the water mass budget are computed within this package.

Package Objectives

The goal of this package is to provide various WMB routines to derive key metrics related to water masses in the ocean and the rates at which they transform and circulate.

Disclaimer

xwmb does not employ any checks to mass or tracer conservation. It is the user’s responsibility to ensure that budgets are properly closed in the datasets. Improperly conserved fields will yield incorrect results.