Geoscience Reference
In-Depth Information
The monitoring system design depends on the conditions of its functioning.
These conditions are connected basically with the hydrophysical properties of the
environment. The synoptical situation in
uences the speed of the degradation
processes and of the oil product transport through the food chains. All aquatories
can be placed by the hydrophysical parameters into two classes: freezing and
nonfreezing. It is evident that from the view point of modeling, the second class is a
special case of the
fl
first class when the snow and ice cover thickness equals zero.
Therefore, the
is gas extraction
zone situated in the Barents Sea with high variability of the synoptic situation is
accompanied during the year by periods of sharp change in the hydrophysical state
of the sea environment. In this zone, the air masses brought from the Atlantic Ocean
and the Central Arctic aquatories collide and mix up. The monsoon character of the
Barents Sea climate is shown by the presence of winds in the low atmospheric
layers which blow from the ocean to the land in summer and in the opposite
direction during the whole winter. The winter season (October
first class is considered in detail. The Shtockman
'
March) is charac-
terized by strong cyclonic activity (the largest number of days with storms and
maximal repetition of strong winds). The ice cover achieves its maximal size in
April. During the June
-
August the period of cyclonic activity is minimal.
The properties mentioned above allow us to make the obvious conclusion that
the technical realization of the system to measure the oil pollutants of Shtockman
-
'
s
gas extraction zone demands the realization of devices protected from great
physical loads and considerable temperature variations. At the same time, powerful
turbulence of the lower atmosphere layer near the water surface in the winter
reduces the quantity of measurements points in space which are required to give the
necessary information. If the wind speed is more than 5 m s
−
1
and the atmosphere
turbulence is high then the atmosphere can be considered as well mixed with a
suf
50 km. In this case, the measurements
can be realized at two or three sites of the aquatory. On the contrary, in the summer
(June
cient precision on the territory of 50
×
August), when the intensity of the atmosphere turbulence is decreased, the
measurements need to be realized in the area of in
-
uence of each oil well. The
assessment of dispersion of the pollutant and the calculation of its spatial distri-
bution are realized by means of corresponding models of atmosphere dynamics.
The most important stage of the analysis and design of the measuring system to
determine the oil pollution level consists in the description of the sea environment
dynamics. It is known that an oil spill spreading on the sea surface is subordinated
to the superposition of two processes. The
fl
first is the spill drift due to sea current,
wind and surface waves. The second is the spill spreading over a calm surface.
For the Barents Sea the second process can be not be taken into account under
the synthesis of the gas extraction zone measurement network. This process should
be taken into account only in the hydrophysical model to re
fl
ect the total range of
the hydrophysical processes.
An analysis of many models describing the oil spreading over the sea surface
gives the following results. The velocity of oil spill motion equals 60 % of the
current speed and 2
4 % of the wind speed. When ice cover exists the wind
-
component is absent.
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