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

General knowledge on the potential fate and degradation of spilled oil relevant
for the Greenland marine environments has been reviewed by
Pritchard & Karlson (in Mosbech 2002). Ross (1992) evaluated the behaviour
of potential offshore oil spills in West Greenland with special regard to the
potential for cleanup. Simulations of oil spill trajectories in West Greenland
waters have previously been performed by Christensen et al. (1993) using
the SAW model and by SINTEF (Johansen 1999) using the OSCAR model in
preparation for the Statoil drilling in the Fylla area in 2000. More recently
DMI simulated oil spill drift and fate in the Disko West area (Nielsen et al.
2006), in eastern Baffin Bay (Nielsen et al. 2008), in South Greenland
(Ribergaard et al. 2010) and presently they are working on simulation of
subsurface spills in the deep waters off South Greenland. Updated oil spill
drift scenarios for the eastern Davis Strait have not yet been developed.
Surface spills
Oil released to open water surfaces spreads rapidly resulting in a thin slick
(often about 0.1 mm in the first day) that covers a large area. Wind-driven
surface currents move the oil at approx. 3% of the wind speed and cause
turbulence in the surface water layer, which breaks the oil slick up into
patches and causes some of the oil to disperse in the upper water column.
This dispersed oil will usually stay in the upper 10 m (Johansen et al. 2003).
Low temperatures and the presence of sea ice can hamper the process of
dispersal considerably, and the complexity of an oil spill in ice can be much
larger than a similar oil spill in open water.
The oil spill simulations have generally addressed surface spills and the subsequent
drift. However oil may also sink to the seabed, depending on the
density of the oil spilled. Even light oil may sink if it adsorbs onto sediment
particles in the water (Hjermann et al. 2007). Sediment particles are frequently
seen in coastal Greenland surface waters where meltwater from the glaciers
can disperse widely into the open sea.
Subsurface spills
Blowouts on a platform will initially cause a surface spill, but may continue
as a subsurface spill if the rising drill tubes from the wellhead collapse. The
risk of a collapse is higher in deeper water. The oil in a subsurface blowout
can float to the surface or remain for a longer time in the water column. The
oil that remains in the water column will typically initially be dispersed in
small droplets. Whether oil in a subsea blowout remains in the water column
as a dispersed plume or floats to the surface depends on oil type,
oil/gas ratio, temperature and water depth. As the potential oil type and
oil/gas ratio is unknown for the assessment area, the behaviour of the oil
cannot be predicted with any certainty. This is why DMI have modelled
subsurface spills in West Greenland which quickly float to the surface
(Nielsen et al. 2006), while SINTEF modelled subsurface spills which would
not reach the surface at all but rather form a subsea plume at a depth of 300-
500 m (Johansen 1999). High total hydrocarbon concentrations (> 100 ppb by
weight) were estimated in an area close to the outflow.
The Deepwater Horizon oil spill in the Mexican Gulf in 2010 was unusual in
size, location and duration (though similar to the Ixtoc blowout in 1979, also
in the Mexican Gulf), and revealed new and undescribed ways spilled oil
could be distributed in the environment (which probably was also the case
during the Ixtoc spill) (Jernelöv 2010). The unusual dispersion of the oil was
mainly caused by the spill site being on the seabed in waters more than 1500
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