Nuclear magnetic resonance study of sea-water freezing mechanisms: 2. temperature dependence of relaxation time of protons in sea-ice brine

Abstract

Results of determinations of proton magnetic relaxation time (T 1) in the liquid phase of frozen sea water at temperatures between -2°C and -38°C, with variable rate and direction of temperature change, are presented. Temperature hysteresis corresponding to the crystallization range of certain sea-water salts, mainly NaCl which partially precipitates as the crystalline hydrate NaCl·2H2O at temperatures below -23°C, is detected in the temperature dependence of T1, as in the analogous dependence of brine content. It is shown that formation of crystalline hydrates in brine is preceded by complete solvation of ions at -5 to -6°C. The main causes of hysteresis in temperature dependence of T1 and the extension of loop limits compared with the analogous loop for liquid brine content are indicated. Additional potentialities of using the nuclear magnetic resonance method for investigating sea-ice properties are presented.