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

Abstract

The ocean current system off Southern Greenland is a key component of the Earth’s
climate system due to its role in the regulation of the global thermohaline
circulation. A combination of historic and new observational data, supported by
modelling simulations, has revealed great complexity in both the surface and deep
currents of the area. A comprehensive review of the available hydrographic data for
the South-East Greenland shelf has shown that the observed spatial variability in the
transport of the on-shelf East Greenland Coastal Current is inconsistent with the
theory that it is primarily driven by local fjord runoff. A high resolution regional
modelling study supports these observations and suggests that the East Greenland
Coastal Current is primarily the result of a bifurcation of the East Greenland Current
in the vicinity of Denmark Strait. Model simulations also suggest that the pathways
followed by the low salinity output of the region’s fjord complexes are influenced
by the strength and position of the main East Greenland Current. New data collected
in the vicinity of Cape Farewell, on the southern tip of Greenland, has also revealed
more complex behaviour in the Deep Western Boundary Current. The significant
spatial variability in Deep Western Boundary Current transport observed in the
region of Cape Farewell suggests that the confluence of Denmark Strait Overflow
Water and Iceland Scotland Overflow Water occurs over a wider geographic area
than is commonly suggested. A review of historic data indicates that these spatial
patterns vary over timescales of months and upwards. It is hypothesised that strands
of overflow water follow different depth controlled pathways dependent on their
relative water density in comparison with the surrounding water masses. This has
significance for the way deep current strength proxies in the region are interpreted in
relation to climatic variations. Time series data for a single location may well
overestimate the variability in the Deep Western Boundary Current further south due
to path switching of the flow. In the future more complete observational datasets
combined with more advanced oceanographic and coupled climate models will
provide a better understanding of the interaction between the regional current
system, the global current system and the climate system. This will enable more
reliable prediction of the impact of global warming and, in particular, the potential
influence of accelerated Greenland ice cap melting on the global ocean circulation.

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