Environmental statement - Flyndre and Cawdor - Maersk Oil

Flyndre and Cawdor Environmental Statement
Section 3 Environmental Baseline
Mean annual rainfall across the North Sea varies between 340 and 500 mm, averaging 425 mm.
Across much of the North Sea north of 54 o N (including the area of the proposed development) it
ranges from 201‐400 mm (OSPAR Commission, 2000).
In the area of the development fog is associated with wind directions of between south‐east and
south‐west, and can reduce visibility to less than 1 km 3‐4% of the time (DTI 2001).
3.1.3. WAVE HEIGHT
Waves are the result of wind action on the sea surface and wave size is dependent on the distance or
fetch over which the wind blows. The wave climate of the area is important in terms of the physical
energy acting on structures including supply vessels, since this will have a large influence on the
structural requirements of the design. The wave climate of the North Sea has changed in recent
years, with a tendency towards increasing wave height.
Significant wave height varies seasonally (Table 3‐1). Within the development area, the significant
wave height of 3 m is exceeded 10% of the time and 75% of the time for heights greater than 1 m
(BODC, 1998).
Month Monthly mean significant wave height (m)
January 3 ‐ 3.5
February 2.5 ‐ 3
March 2 ‐ 2.5
April 2 ‐ 2.5
May 1 ‐ 1.5
June 1.5 ‐ 2
July 1.5 ‐ 2
August 1.5 ‐ 2
September 1.5 ‐ 2
October 2 ‐ 2.5
November 2 ‐ 2.5
December 2 ‐ 2.5
Table 3‐1 Monthly mean significant wave height (BODC, 1998).
3.1.4. TEMPERATURE
The temperature of the sea affects both the properties of the sea water and the fates of discharges
and spills to the environment. Average sea surface and seabed temperatures in the area of the
Flyndre and Cawdor fields are given in Table 3‐2.
Location Mean temperature in winter ( o C) Mean temperature in summer ( o C)
Sea surface 5.5 – 6.0 15.5 ‐ 16
Sea bottom 5.5 ‐ 6.0 6.5 ‐ 7.0
Table 3‐2 Water temperature for area of the development (BODC, 1998).
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