||Measurements of sea surface salinity (SSS) were obtained from in situ oceanographic observations compiled by NOAA’s World Ocean Atlas 2009 (WOA09; Antonov et al. 2010). Monthly climatological means (measured in practical salinity units) were calculated by the original authors by averaging five “decadal” climatologies, at 1 arc-degree spatial resolution for the following time periods: 1955–1964, 1965–1974, 1975–1984, 1985–1994, 1995–2006. Further details on data compilation, quality control, and the creation of climatologies can be found in the original publication (Antonov et al. 2010). We downloaded the monthly climatologies for the sea surface in ArcGIS point shapefile format and used spline interpolation in ArcGIS 9.3.1 to spatially smooth the data from 1 arc-degree to 30 arc-second grids within the GSHHS ocean mask. The final monthly climatologies were multiplied by 100 and rounded to the nearest integer value in order to conserve file space. Five bioclimatic MARSPEC layers were calculated from the scaled climatologies: mean annual sea surface salinity (biogeo08), salinity of the least salty month (biogeo09), salinity of the saltiest month (biogeo10), annual range in sea surface salinity (biogeo11), and annual variance in sea surface salinity (biogeo12).