Examining the soil and water cycles of the 1002 region,
one cannot ignore the presence of permafrost, or permanently frozen
soil,¨ which underlies 80% of Alaska and remains a central issue
in the debate about oil drilling. Permafrost has been defined as frozen
ground in which a naturally occurring temperature below 0æ C (32æ F)
has existed for two or more years (A). On the North Slope, permafrost
ranges in thickness from about 700 to as much as 2,240 feet thick, and
may be as cold as -8° to -10° C.
Permafrost can be either thaw-stable or non thaw-stable, depending on
the type and percentage water of the soil it is made of. Permafrosts
in more fine-grained soils like loess (silty) tend to thaw, sink, and
create thermokarsts more often. Permafrost thaws from heat input, such
as global warming or human activity, as well as the clearing of vegetation
which insulates the ground.
Permafrost is affected by road dust generated by traffic on unpaved
roads; snow melt due to dust deposition can lead to flooding, ponding,
and hydrological changes in oil. Continuing oil and gas exploration,
development, and production, construction of a natural gas pipeline,
the operation and maintenance of facilities, and other activities requiring
road travel would add cumulatively to the volume of road dust generated
on unpaved roads (A). Regions of ice which have been wind-dusted are
likely to undergo localized melting earlier than the neighboring non-dusted
There are three approaches to dealing with the permafrost problem in
the construction practice. The first and most obvious is to avoid it
entirely. The second is to destroy it by stripping the insulating vegetative
cover and allowing it to melt over a period of years. This has the obvious
drawback of requiring a considerable period of time to elapse before
construction can begin, and even then, it is a good idea to excavate
the thawed ground and replace it with coarse material.
The third approach, and one which is becoming more widespread, is to
preserve it. This can be accomplished by building on piles to allow
cold air to circulate beneath heated structures, by building up the
construction site with gravel fill which insulates and protects the
permafrost below, or by refrigeration to maintain low ground temperatures.
This is done by utilizing thermal piles or freeze tubes, such as those
used by the trans-Alaska pipeline. These devices are filled with a non-freezing
liquid and act like coffee percolators. They are cooled during the winter
months and draw heat from the ground to retard thawing during warm weather
In nearshore areas, ice-bonded permafrost is probably present and must
be considered in the design of an offshore pipeline. But nearshore ice-wedge
permafrost under shallow water, particularly along a rapidly receding
coastline, is even more critical for design. Oil pipelines placed in
areas of ice-bonded or ice-wedge permafrost must be heavily insulated
to limit thawing of permafrost. The best location for an offshore platform
is at water depths of 6.5-65 feet, to minimize ice gouging. Beyond the
6.5 foot water depth the top of the ice-bonded permafrost generally
is below the surface of the seabed. Inshore of the 18-foot bottom-depth
contour, ice gouging is typically less than 1.6 feet (Y). Relation of
oil drilling, permafrost and vegetation
Permafrost layer restricts the drainage of water through the soil, making
it moist in the short summer growing season. It is easily broken by
road construction or the seismic explosions used in oil exploration,
changing the water drainage patterns of the soil and thus retention
of moisture. Melting permafrost has also led to widespread damage of
buildings, costly road repairs, and increased maintenance for pipelines
and other infrastructure impacts that will continue to grow in magnitude.
Permafrost also stores large amount of ancient carbon and methane; thawing
is likely to release some of this stored carbon and methane back into
the atmosphere, amplifying the risk of further climate change. The boreal
forest will advance northward into present coastal plain tundra, and
mixed forest into present boreal forest. Forest fires and insect outbreaks,
both of which have increased sharply in recent years, will further increase.
If the permafrost thaws, the vegetation will in the long term dries
out, altering plant communities and use by wildlife.
It has been observed that in areas where the permafrost thaws, there
is a sudden rapid growth of plants, which attract more animals to feed
on. However, this is only momentary. Once the permafrost thaws, temporarily
there is much water for plants to grow well for like a month or two,
but then the water is continuously used up and drained away as there
is no layer to prevention drainage now; yet the permafrost, once destroyed,
take years to resume. Therefore, a few months after destruction, water
will finally be deficient and no plants can grow well even during summer
when water has already been used up, drained away but no permafrost
exists to trap them for the growing season. This detrimental effect
on vegetation is permanent, while the vast growth of plants is just
Impacts of Seismic Exploration:
Seismic exploration involves
a large number of vehicles driving across the tundra in a grid or network.
The snow covering the vegetation in teh 1002 area is often shallow and
therefore it doesn't provide great protection to the vegetation and
soil underneath. The impact from the seismic grid will depend on the
a. Type of vegetation. Trails
in shrub-dominated tundra have the slowest rate of recovery, whereas
trails in sedge-dominated tundra recover well.
b. Texture and ice content
of the soil.
c. The shape of the surface.
d. the depth of the snow;
snow depths of at least 25 cm are required to minimize disturbance.
e. Type of vehicle. Surprisingly
enough, camp move trails persist much longer and produce a more scarring
effedct than seismic trails, due the great pressure exerted by camp
Studies conducted by the
US Fish and Wildlife Service (USFWS) after the 1984-85 exploration showed
the following effects:
a. The depth to permafrost
was greater on disturbed sites than nearby controls.
b.Increased thaw depths.
c. Increased trail subsidence.
d.Shifts to wetter conditions.
e.Formation of distinct ruts.
f. Invasion of grasses
g. Decreases in shrub cover.
h. Longterm disruption of
the soil thermal regime.
1. Union of Concerned Scientists (2002). http://www.ucsusa.org/global_environment/archive/page.cfm?pageID=780
2. Williams, M.; Rastetter, E. Vegetation characteristics
and primary productivity along an arctic transect: implication for scaling-up.
Journal of Ecology 1999 87: 885-898.