The data set contains subsurface salt concentration profiles and pore water density measurements from salt deserts showing salt polygons at the surface. The data set characterizes the subsurface of the salt deserts and is used together with other data sets (which characterize the surface) to explain the driving mechanism of salt polygon growth in salt deserts.For each site, the sand in a cross-sectional area of about 2 m x 1 m below a salt polygon was sampled with a horizontal and vertical resolution of 15 cm and 10 cm respectively. Samples were then analyzed for their salt content to resolve salinity gradients present below the salt polygon patterns at the surface. Additionally, pore water at the sites was sampled from the surface and at a depth of ~1 m to measure the surface and background salinity. The pore water was then analyzed using a vibrating-tube densimeter with a measurement accuracy of 5 x 10^(-4) g/cm^3.Samples used to compile salt concentration profiles were taken at 3 different sites, samples of pore water were taken at 8 different sites. All samples were collected during a field campaign at Owens Lake, Central California in January 2018.Related to this data are also- grain size distributions of sand samples taken at the field sites at different depths (see data at https://doi.pangaea.de/10.1594/PANGAEA.910996),- pictures and videos characterizing the sites (see data at https://doi.pangaea.de/10.1594/PANGAEA.911054),- temperature and humidity time-series measured during one week in late 2016 (see data at https://doi.pangaea.de/10.1594/PANGAEA.922231 ),- as well as surface scans measured by TLS (see data at https://doi.pangaea.de/10.1594/PANGAEA.911233)- and a chemical characterization of the salt species present in the crust (see data at https://doi.pangaea.de/10.1594/PANGAEA.911239).

Changes in version 2.0:- In the file owens_lake_T32-1-L1_P3_salt_concentration_profile, zero-values were removed since they corresponded to missing samples. Doubtful values were removed since they corresponded to wrong results from the laboratory analysis.- In the file owens_lake_T27-S_salt_concentration_profile, negative values were removed, since they corresponded to missing values from the laboratory analysis.- In the file owens_lake_pore_water_density, entries from the column measurement_error were removed for cases with <= 2 measurements. Sites T10-3, T16 and T16_validation were renamed to T10-3_P1, T16_P1 and T16_P1_validation respectively, to be consistent with related data sets. Entries from the columns "z" and "x" were swapped for sites T25-3_P2 and T16_P1 since these were in the wrong order initially. Depth entries for site T16_P1 were added and the entries in the colum "Distance from left ridge" were converted to units of meters.