An Investigation into the dynamics of the ocean current system off southern Greenland

The ocean current system off Southern Greenland is a key component of the Earth’sclimate system due to its role in the regulation of the global thermohalinecirculation. A combination of historic and new observational data, supported bymodelling simulations, has revealed great complexity in both the surface and deepcurrents of the area. A comprehensive review of the available hydrographic data forthe South-East Greenland shelf has shown that the observed spatial variability in thetransport of the on-shelf East Greenland Coastal Current is inconsistent with thetheory that it is primarily driven by local fjord runoff. A high resolution regionalmodelling study supports these observations and suggests that the East GreenlandCoastal Current is primarily the result of a bifurcation of the East Greenland Currentin the vicinity of Denmark Strait. Model simulations also suggest that the pathwaysfollowed by the low salinity output of the region’s fjord complexes are influencedby the strength and position of the main East Greenland Current. New data collectedin the vicinity of Cape Farewell, on the southern tip of Greenland, has also revealedmore complex behaviour in the Deep Western Boundary Current. The significantspatial variability in Deep Western Boundary Current transport observed in theregion of Cape Farewell suggests that the confluence of Denmark Strait OverflowWater and Iceland Scotland Overflow Water occurs over a wider geographic areathan is commonly suggested. A review of historic data indicates that these spatialpatterns vary over timescales of months and upwards. It is hypothesised that strandsof overflow water follow different depth controlled pathways dependent on theirrelative water density in comparison with the surrounding water masses. This hassignificance for the way deep current strength proxies in the region are interpreted inrelation to climatic variations. Time series data for a single location may welloverestimate the variability in the Deep Western Boundary Current further south dueto path switching of the flow. In the future more complete observational datasetscombined with more advanced oceanographic and coupled climate models willprovide a better understanding of the interaction between the regional currentsystem, the global current system and the climate system. This will enable morereliable prediction of the impact of global warming and, in particular, the potentialinfluence of accelerated Greenland ice cap melting on the global ocean circulation