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  • Bigg, G.R. and M.R. Wadley, 2007: The simulation of “Great Salinity Anomalies” in coupled climate models. J. Geophys. Res., 112, doi:10.1029/2005JD007025.

“Great Salinity Anomalies” (GSAs) have been observed to propagate in the upper ocean around the sub-polar gyre of the North Atlantic with a decadal time-scale of both propagation and return. Successful simulation of such features in the ocean is an important prerequisite for confidence in predictions of the ocean’s response to future freshwater anomalies from ice melt or sub-polar river discharge. The coupled climate model experiments prepared for the Fourth Assessment Report of the Intergovernmental Panel on Climate Change offer a unique cross-section of model formulations, resolutions and scenarios with which to explore climate models’ ability to produce GSAs. The performance of nine different models, with a range of horizontal and vertical atmospheric and oceanic resolutions, in producing GSAs was examined using a base period of 100 years. One scenario was a pre-industrial control simulation, while the other was forced by an increasing atmospheric carbon dioxide of an enhanced greenhouse world (scenario sresa1b). It was found that the strongest control on the existence of model GSAs was the oceanic horizontal resolution. This needed to be of the order of 1.5o or less for GSAs to occur within the model. In those models which possessed GSAs these were overwhelmingly generated within the Labrador Sea, with similar periodicities to those observed. Anomalies reaching the Greenland Sea through the Nordic Sea gyre circulations generally slowed and died before propagating back into the Atlantic. Freshwater flow through the Canadian Archipelago appears to be an important factor in producing the most realistic simulation. Within the greenhouse world GSAs were significantly less likely to occur, were weaker and more likely to originate from east of Greenland.


Last Updated: 2007-07-26

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