Sack Lunch Seminar (SLS)

Salinity-Dominated Thermohaline Circulation: Multiple Equilibria and Their Possible Relevance for the Paleo Arctic Ocean




This talk addresses some dynamical aspects of the Arctic Ocean stratification, which are partly motivated by indications of a large shelf ice system during the Marine Isotope Stage 6 (180-130 ky BP). Geological data are briefly presented that indicate a past Arctic Ocean shelf ice that reached several hundreds of meter below the sea surface. In the present-day Arctic Ocean, the presence of a warm layer of Atlantic water a few hundred meters below the surface appears to hinder the formation of shelf ice. Can a weak freshwater input result in a deep cold halocline that pushes the Atlantic layer downward? This question and some related aspects of salinity-dominated thermohaline circulation is examined using a conceptual two-layer model and numerical simulations. In particular, the dynamics in the limit of weak and deep reaching stratification is considered. The possible significance for the Arctic Ocean of multiple equilibrium solutions that arise in the conceptual model is discussed.