Once you've decided whether you want actual NaCl molarity or total salt as NaCl molarity, and once you've picked a spot on the map above, you can convert units to obtain a molarity of NaCl from a salinity in PSS. Suppose your spot has a salinity of 35 PSS. Then your calculation will look like
PSS g sea salt/kg seawater g Cl/kg seawater
mol Cl/kg seawater mol NaCl/kg seawater mol NaCl/L seawater
1 PSS unit = 1 g sea salt/ kg seawater
1.80655 g sea salt = 1 g Cl
The last step converts kg seawater to L seawater, and you'll need the density of seawater for that. It's between 1.02 g/mL and 1.07 g/mL, but if you want precision you'll have to look up the number in a physical oceanography text. (I can't give you a number because the density will depend on the salinity you use- and on the ocean temperature and pressure).
Copyright © 1997-2010 by Fred Senese
Comments & questions to fsenese@frostburg.edu
Last Revised 02/23/18.URL: http://antoine.frostburg.edu/chem/senese/101/moles/faq/print-seawater-salt-molarity.shtml