Surface generation of poleward-propagating spiciness anomalies
in the North Atlantic Ocean
LOCEAN, Université Pierre et Marie Curie, Paris, France
ABSTRACT: As suggested by Latif et al. (2000), anomalous salty waters generated in the tropics and subtropics in the North Atlantic Ocean due to global warming could propagate towards high latitudes and densify the surface waters in the deep convection regions, leading to a stabilized thermohaline circulation (THC), instead of slowed down THC as commonly suggested.
In this talk, we focus on the surface generation and propagation of spiciness anomalies (defined as isopycnal salinity anomalies) from the salinity maximum water (SMW) region in the North Atlantic Ocean toward the Gulf Stream region. After a brief review of the propagation of these anomalies, their surface generation is investigated based on a model study. In the SMW region, a sea surface salinity (repectively temperature) anomaly result in migrations of outcropping isopycnal surface of up to 400 km and spiciness anomalies develop from the temperature and salinity properties on the isopycnals when they subduct. The strongest spiciness anomalies are generated in the western SMW region with an amplitude close to 0.3 psu and a horizontal extension on the order of 500 km. The formation mechanism is analyzed and quantified with an analytical model.
This model forecasts the amplitude and sign of the subducted spiciness anomalies based on the observable surface parameters and the mixing processes that occur in the thermocline. It gives a more realistic description of the generation and subduction of spiciness anomalies than the model developed by Nonaka and Sasaki (2007), according to a validation with an OGCM simulation forced over the period 1948-2002.