UMD AOSC Seminar
Inter- and Intra-Basin Freshwater Disparities and Global Ocean Thermohaline Circulation
Dr. Dan Seidov
NOAA Ocean Climate Laboratory
The current paradigm of the global ocean thermohaline circulation (THC) is that the THC is almost exclusively controlled by freshwater fluxes across the sea surface in the Nordic Seas and northern North Atlantic (NNA). A generalized version of this paradigm suggests that the balance between formation of North Atlantic Deep Water and Antarctic Deep Water is responsible for the so-called "global ocean conveyor belt" - a system of ocean currents connecting different ocean basins and most notably - the northern North Atlantic and northern North Pacific Oceans - the most distant regions of the World Ocean. On the other hand, it is presumed that on the global scale the sea surface salinity (SSS) contrast between the Atlantic and Pacific oceans is also the key for the overall character of THC operation. Despite the agreement that both driving forces-the inter- and intra-basin salinity distributions-are important, it remained largely unknown how fragile are these SSS contrasts and how large the freshwater cycling in the ocean-atmosphere system should be in order to maintain the global conveyor. Another critical question is whether the THC indeed decisively depends on the freshwater balance in NNA. Our recent modeling efforts challenge the view of THC as a system operated exclusively from NNA. It has been shown that a slight disparity in freshwater redistribution between the Atlantic and Pacific oceans can be sufficient for building up and maintaining a global conveyor-type ocean thermohaline circulation. Relatively small changes in this disparity can easily change the operation of the entire global conveyor.
April 2, 2009, Thursday