"NO", a conservative water-mass tracer

A composite property, 9NO ₃ + O ₂, is proposed as a conservative water-mass tracer. The coefficient 9 is chosen so that the increase in "NO" resulting from nitrate introduction during respiration just balances the consumption of dissolved oxygen gas. Because of the pronounced difference in the preformed nitrate content of deep water produced at the northern and southern ends of the Atlantic Ocean "NO" provides an independent means of disentangling the degree of mixing of various water types in the deep sea. Evidence based on data obtained during the Atlantic Geosecs program is presented to demonstrate the sensitivity and reliability of this conservative tracer.