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

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Along the Greenlandic west coast the current patterns tend to follow the bathymetry
along the coast (Ribergaard et al. 2004). Southeast of the assessment
area (south of the Fyllas Banke area) the current patterns are influenced
by the steep continental slope, and the complex topography of several
shallow banks that deflect the coastal currents and generate instabilities in
the current flow.
The East Greenland Current component loses its momentum on the way
northward, and at the latitude of Fylla Banke (64º N) there is no longer a
strong and solid current. A great proportion of the mass is deflected westward
towards Canada where it joins the Labrador Current. Further north the
deflection towards west continues resulting in a further weakening of the
current (Buch 2000).
The Polar water inflow is strongest during spring and early summer (May-
July). The inflow of relatively warm Atlantic water masses of the West
Greenland current is strongest during autumn and winter, explaining why
the waters between 62º N and 67º N are usually ice free during winter time.
Mixing and heat diffusion of the two layers (The Polar and Irminger Currents)
are important factors in determining temperature conditions in the assessment
area. Years where the East Greenland Current and Irminger Current
are strong will often be cold years (Nazareth & Steensboe 1998, Buch
2000, 2002, Hansen et al. 2004).
A fifty-year long time series (1950-2000) of temperature and salinity measurements
from West Greenland oceanographic observation points at Fyllas
Banke has revealed strong inter-annual variability in the oceanographic
conditions off West Greenland. These climatic variabilities can be related to
shift in the NAO index from negative to positive values during the period
1970-2000, resulting in colder climate (Buch et al. 2005). However, over the
past two decades there has been a tendency towards increased water temperatures
and reduced ice cover during the Arctic winters (Rothrock et al.
1999, Parkinson 2000, Hansen et al. 2006, Comiso et al. 2008). High melt rates
from the inner Godthåbsfjord glacier suggest increased input of freshwater
to the West Greenland basin, presumably affecting the marine ecosystem
and the fjord and marine water exchanges (Rysgaard et al. 2008 and
references therein). The warmer climate in the Arctic during the last decade
may partly be a result of the change in the NAO index from positive to negative.
However, there is a profound increase of 0.4º C per decade (1966-2003)
in Arctic surface air temperature, which deviates from that of natural expected
variations (McBean et al. 2005).
3.2.2 Hydrodynamic discontinuities
Hydrodynamic discontinuities are areas where different water masses meet
with sharp boundaries and steep gradients between them. They can be
upwelling events where cold nutrient water is forced upwards to the upper
layers, fronts between different water masses and ice edges (inclusive the
marginal ice zone). Upwelling often occurs along the steep sides of the shelf
banks driven by the tidal current and therefore usually alternates with
downwelling. Model simulations north of the assessment area predict that
that most frequent upwelling occurs west of the banks, both north and south
of the Disko Bay entrance and at the slopes of Store Hellefiskebanke
(Mosbech et al. 2007 and references therein).