Nontrivial features in the hydrodynamics of seawater and other stratified solutions

Stratified two-component media (for example, sea water) can have general hydrothermodynamic properties widely different from the properties of 'usual' fluids, whose density depends on temperature only. For example, temperature perturbations in such media can increase despite a hydrostatically stable density stratification. In this review, a number of recently discovered physical mechanisms and phenomena are discussed, including the mechanisms of convective instability, the hydrodynamic 'memory' of two-component media, the formation of temperature and admixture concentration jumps, the anomalous response of binary mixtures to mechanical and thermal forcing, and the effective 'negative heat capacity'. (reviews of topical problems)