Temperature as a passive isopycnal tracer in salty, spiceless oceans

Abstract

The decoupling between the gradients of temperature and density in cold, relatively fresh oceanic waters is discussed from a theoretical standpoint and furthermore demonstrated on the basis of observations from the Baltic Sea. Near the temperature of maximum density, the thermal expansion coefficient is effectively zero, hereby de facto making temperature a passive tracer. As a consequence, the baroclinic advection of heat anomalies is determined by freshwater gradients. Recognition of such dynamics could prove helpful for the understanding of a warmer, fresher future Arctic Ocean, as projected by the IPCC.