The Davis Strait - DCE - Nationalt Center for Miljø og Energi

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3 Physical environment
Michael Dünweber (AU)
The assessment area forms part of the Davis Strait and is situated within
what is normally referred to as the sub-Arctic region in the marine environment,
defined as the marine areas where the upper water layers are of mixed
polar and non-polar origin (Dunbar 1954). The Davis Strait is a semienclosed
oceanic basin that separates western Greenland and Baffin Island,
the largest island in the Canadian Arctic Archipelago. In the north it is connected
to the Arctic Ocean through Baffin Bay and the Nares Strait. In the
south it is connected to the Labrador Sea. In terms of hydrography, the area
is characterised by sub-Arctic waters from the North Atlantic (average July
temperature higher than 5° C) in the southern part and the high-Arctic waters
of Baffin Bay (average July temperature below 5° C) in the northern part.
The shelf comprises the rather shallow waters (depths less than 100m) in the
northeastern corner to more than 2000m (down to 2,500 metres) in the
southwestern corner. This shelf includes several large shoals or banks e.g.,
Fyllas Banke, Sukkertop Banke and Store Hellefiskebanke, typically ranging
between 20 and 100m in depth. The shelf is traversed by deep troughs,
which separate the fishing banks. At its narrowest point, a ridge up to approximately
600m deep extends between Greenland (at Holsteinborg, Sisimiut)
and Baffin Island (at Cape dyer).
On a large scale, the metrological and oceanographic conditions of Davis
Strait are quite well known. Recent descriptions are found in (Buch et al.
2005, Myers et al. 2009), however the majority are focused on the Baffin Bay
area with short descriptions of the Davis Strait (Tang et al. 2004, Dunlap &
Tang 2006). More detailed descriptions on hydrography are found for offshore
areas prepared by the Danish Meteorological Institute and Bureau of
Minerals and Petroleum (DMI and BMP, respectively) (Nazareth &
Steensboe 1998, Buch 2000, Karlsen et al. 2001, Buch 2002, Hansen et al. 2004,
Ribergaard 2010). An early impact assessment report by NERI for the Fyllas
Banke is found in Mosbech et al. (1996b) and an oil sensitivity atlas for the
coastal zones of West Greenland by Mosbech et al. (2004a) and (2004b).
3.1 Weather and Climate
The weather in this region is determined by the North American continent
and the North Atlantic Ocean, namely the North Atlantic Oscillation (NAO).
NAO exerts a dominant influence on the winter-time temperatures of surface
air and sea temperatures in the Arctic. When the NAO is positive, enhanced
westerlies flow across the Atlantic and intensify the North Atlantic
Current, which is deflected to the east of Greenland. This results in low intensities
of the cold, south-flowing East Greenland Current and the warm,
north-flowing Irminger current (derived from the North Atlantic Current),
producing cold conditions in the Arctic region. When the NAO is negative,
the conditions are almost the opposite, with low inflow of North Atlantic
Waters coupled with an intensified East Greenland Current and Irminger
Current giving warm Arctic temperatures (Buch 2002, Ribergaard 2010).
However, the Greenland Inland ice and the steep coasts of Greenland also
have a fundamental impact on the weather local to the area. Many Atlantic