A Simulation of Thermohaline Effects of a Great Salinity Anomaly

Model simulations of an idealistic "Great Salinity Anomaly" (GSA) demonstrate that variability in the sea ice export from the Arctic when concentrated to short pulses can have a large influence on the meridional heat transport and can lead to an altered overturning state. One single freshwater disturbance resulting from excess ice export, as in 1968, can disrupt the deep mixing process. The critical condition for a large oceanic response is defined by the intensity, duration, and timing of the ice pulse, in particular, as it exits through the Denmark Strait. A recovery from this event takes several years for advection and diffusion to remove the salinity anomaly. Concurrently, the influence of the GSA propagates to the subtropics via the boundary currents and baroclinic adjustment. As a result of this adjustment, there are large (up to 20%) changes in the strength of the overturning cell and in the meridional heat transport in the subtropics and subpolar areas. Simulations show a temperature–salinity shift toward colder and fresher subpolar deep waters after the GSA, which is also found in hydrographic data. Corresponding author address: Dr. Sirpa Häkkinen, NASA/Goddard Space Flight Center, MC 971, Greenbelt, MD 20771.