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

10 Impacts of the potential routine activities
Flemming Merkel, David Boertmann, Anders Mosbech (AU), Fernando Ugarte
(GINR), Doris Schiedek & Susse Wegeberg (AU)
10.1 Exploration activities
In general all activities relating to exploration are temporary and will be
terminated after a few years if no commercial discoveries are made. Another
important aspect in relation to exploration is that activities can only take
place during months when the sea is more or less free of ice.
Environmental impacts of exploration activities relate to:
• Noise from seismic surveys and drilling
• Cuttings and drilling mud
• Disposal of various substances
• Emissions to air
• Placement of structures.
In relation to exploration, only the most significant impacts (from noise, cuttings
and drilling mud) will be considered. The other issues will be dealt
with in the production and development sections, as they are much more
significant during these phases of the life cycle of a petroleum field.
10.1.1 Assessment of noise
Noise from seismic surveys
The main environmental impacts from the seismic sound generators can potentially
include:
• physical damage: injury to tissue and auditory damage from the sound
waves
• disturbance/scaring (behavioural impacts, including masking of underwater
communication by marine mammals).
A recent review of the effects of seismic sound propagation on different biota
concluded ‘that seismic sounds in the marine environment are neither
completely without consequences nor are they certain to result in severe and
irreversible harm to the environment’ (DFO 2004). But there are some potential
detrimental consequences. Short-term behavioural changes (such as
avoiding areas with seismic activity) are known and in some cases well documented,
but longer-term changes are debated and studies are lacking.
In Arctic waters there are certain special conditions that should be considered.
It cannot be assumed that there is a simple relationship between sound
pressure levels and distance to source due to ray bending caused, for example,
by a strongly stratified water column. It is therefore difficult to base impact
assessments on simple transmission loss models (spherical or cylindrical
spreading) and to apply assessment results from southern latitudes to the
Arctic (Urick 1983). For example, sound pressure may be very strong in convergence
zones far (> 50 km) from the sound source, and this is particularly
evident in stratified Arctic waters. This has recently been documented by
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