By Clement de Boyer Montégut, available on SEANOE https://www.seanoe.org/data/00806/91774/
The dataset made available here is the monthly climatology (i.e. 12 months) of ocean surface Mixed Layer Depth (MLD) over the global ocean, at 1 degree x 1 degree spatial resolution. It is provided as a netcdf data file embedded in a tar file at bottom of this page. A short documentation about the product is also available as a pdf readme file. The climatology is based on about 4.5 million casts/profiles of temperature and salinity measurements made at sea between January 1970 and November 2021. Those profiles data come from the ARGO program and from the NCEI-NOAA World Ocean Database (WOD). The MLD is computed on each individual cast/profile using a threshold criterion. The depth of the mixed layer is defined as the shallowest depth where the surface potential density of the profile is superior to a reference value taken close to the surface added with the chosen threshold. Here we take a threshold value for the density of 0.03kg/m3, and a surface reference depth fixed at 10m (de Boyer Montégut et al. JGR 2004, see reference details at bottom of page). This mixed layer is by definition homogeneous in density (up to 0.03 kg/m3 variations) and can also be called an isopycnal layer.