This is Section 6.3 of the Arctic Climate Impact Assessment.
Lead Author: Arne Instanes; Contributing Authors: Oleg Anisimov, Lawson Brigham, Douglas Goering, Lev N. Khrustalev, Branko Ladanyi, Jan Otto Larsen; Consulting Authors: Orson Smith, Amy Stevermer, Betsy Weatherhead, Gunter Weller
Infrastructure is defined as facilities with permanent foundations or the essential elements of a community. It includes schools; hospitals; various types of buildings and structures; and facilities such as roads, railways, airports, pipelines, harbors, power stations, and power, water, and sewage lines. Infrastructure forms the basis for regional and national economic growth. In the Arctic, the largest population concentrations are located in North America and Russia, as is much of the existing infrastructure.
Most arctic facilities are connected with population concentrations, extraction of natural resources, or military activity. In the case of industrial or military developments, facilities typically include industrial buildings and warehouses, crew and worker quarters, embankments (roadway, airport, work pad), pipelines (both chilled and warm), and excavations of different types. Many industrial buildings must be designed to accommodate heavy equipment, increasing demands on the foundation system. In the case of human settlements, infrastructure includes public transportation systems, utility generation and distribution facilities, and buildings associated with residential or business activities. In addition to the complexity presented by the wide range in requirements of the different types of infrastructure, the problems associated with climate change are compounded by the range of environmental conditions over which human activities occur, extending from the sporadic permafrost/seasonal frost zone to the high Arctic with its cold, continuous permafrost layer.
Northern pipelines are likely to be affected by frost heave and thaw settlement. Slope stability is also likely to be an issue in discontinuous permafrost.
The settlement of shallow pile foundations in permafrost could possibly be accelerated by temperature increases over the design life of a structure (~20 years). However, over the same period, there is very likely to be less of an effect on the deeper piles used for heavier structures.
Large tailings disposal facilities might be affected (negatively or positively) by climate change, due to the long-term effects on tailings layers.There is some chance that layers that freeze during winter deposition in northern seasonal-frost or permafrost areas would thaw out many years later, releasing excess water and contaminants into groundwater.There is some chance that increasing temperature would significantly change the rate of thawing of such layers.
The availability of off-road transportation routes (e.g., ice roads, snow roads) is likely to decrease owing to a reduction in the duration of the freezing season. The effect of a shorter freezing season on ice and snow roads has already been observed in Alaska and Canada (section 16.3.6).
Climate change is likely to reduce ice-cover thickness on bodies of water and the resulting ice loading on structures such as bridge piers. However, until these effects are observed, it is unlikely that engineers will incorporate them into the design of such structures.
The thickness of arctic sea-ice cover is also likely to change in response to climate change, and it is possible that this will affect the design of offshore structures for ice loadings, and the design of ice roads used to access structures over landfast ice in winter.
Precipitation changes are very likely to alter runoff patterns, and possibly the ice–water balance in the active layer. It is very difficult to assess the potential effects of these changes on structures such as bridges, pipeline river crossings, dikes, or erosion protection structures.
The stability of open-pit mine walls will possibly be affected where steep slopes in permafrost overburden have been exposed for long periods of time. The engineering concerns relate to increased thaw depth over time, with consequent increased pore pressures in the soil and rock, and resulting loss of strength and pit-wall stability.
The cleanup and abandonment of military and industrial facilities throughout the Arctic sometimes involves storage of potentially hazardous materials in permafrost or below the permafrost table.There is some chance that permafrost degradation associated with climate change will threaten these storage facilities. AMAP provides a detailed review of arctic pollution issues.
For all types of arctic infrastructure, the key climaterelated concern is changes in the thermal state of the supporting soil layers. As described in section 22.214.171.124, changes in soil temperature can induce large variations in soil strength and bearing capacity and may also cause thaw settlement or frost heave. Many facilities and structures were designed for current climatic conditions, and it is possible that appreciable warming will introduce differential settlement beneath them.The susceptibility of permafrost to environmental hazards associated with thermokarst, ground settlement, and several other destructive cryogenic processes can be crudely evaluated using the geocryological hazard index, which is the combination of the projected percentage change in active-layer thickness and the ground ice content:
Fig. 16.19. Projected geocryological hazard potential in 2050, based on output from the HadCM3 model. Eqn. 16.2
where ?zal is the percentage increase in active-layer thickness, and Vice is the volumetric proportion of nearsurface soil occupied by ground ice.The index provides a qualitative representation of relative risk, with lower values representing lower risk and vice versa. Future geocryological hazards were projected using several scenarios of climate change (including those from the ACIA-designated models) as input to a permafrost model that included information about existing permafrost and ground ice distributions from the IPA. Figure 16.19 presents the geocryological hazard potential with respect to engineered structures projected for 2050, calculated using the HadCM3 scenario.The map shows areas projected to have low, moderate, and high susceptibility to thaw-induced settlement, as well as areas where permafrost is projected to remain stable.
A zone of high and moderate risk potential is projected to extend discontinuously around the Arctic Ocean, indicating high potential for coastal erosion. North American population centers (e.g., Barrow, Inuvik) and river terminals on the arctic coast of Russia (e.g., Salekhard, Igarka, Dudinka, and Tiksi) fall within this zone.Transportation and pipeline corridors traverse areas of high projected hazard potential in northwestern North America. The area containing the Nadym- Pur-Taz natural gas production complex and associated infrastructure in northwest Siberia also falls in the projected high-risk category. Large portions of central Siberia, particularly the Sakha Republic (Yakutia) and the Russian Far East, have moderate or high projected hazard potential. These areas include several large population centers (Yakutsk, Noril’sk, and Vorkuta), an extensive network of roads and trails, and the Trans- Siberian and Baikal–Amur mainline railroads.The Bilibino nuclear power station and its grid occupy an area of projected high hazard potential in the Russian Far East. Areas of lower projected hazard potential are associated with mountainous terrain and cratons (geologically stable interior portions of continents) where bedrock is at or near the surface.
Three main design approaches are employed when using permafrost soils as foundations for structures and infrastructure:
- to maintain the existing ground thermal regime (referred to as Principle I in Russia, and the passive method in North America);
- to accept changes in the ground thermal regime caused by construction and operation, or to modify foundation materials prior to construction (referred to as Principle II in Russia, and the active method in North America); and
- to use conventional foundation methods if the soils are thaw stable.
With the first two methods, it is necessary to estimate the maximum active-layer thickness and the maximum permafrost temperature as a function of depth that the structure will be subjected to in its lifetime. The air thawing index can be used to calculate active-layer thickness and maximum permafrost temperatures as a function of depth and time of year (see section 126.96.36.199). Other approaches can also be used to calculate active-layer thickness (e.g., using a full surface energy balance).
A significant consequence of permafrost degradation is likely to be a change in the maintenance conditions of many structures, especially for those that were designed without consideration of potential climate change. Projections of the change in bearing capacity and durability of foundations as temperatures change illustrate the potential for damage as a result of climate change. The results of such calculations for Yakutsk are presented in Table 16.9.
For structures utilizing Principle I (permafrost conservation), the table illustrates that foundation failures will possibly begin when the mean annual air temperature increases by a small amount (a few tenths of a degree), and extend to all foundations when the increase exceeds 1.5 ºC. This indicates that there is little margin for safety in the bearing capacity related to changes in air temperature. For structures utilizing Principle II (permafrost thawing), design is based on allowable deformations. As with structures utilizing Principle I, no factor of safety is included in the design. However, foundation failures will occur a relatively long time after the temperature changes. This means that the change in temperature affects only the durability of the foundations.Table 16.9 shows that a small increase in air temperature substantially affects the stability of the building, and the safety of the foundation decreases sharply with rising temperatures.
Temperature increases can result in a significant decrease in the lifetime and potential failure of the structure. Permafrost engineers, therefore, face the problem of preserving infrastructure under projected future climate conditions.
The compensation method (putting new buildings into operation as existing ones are damaged and abandoned) appears to be one of the possible ways to address this problem. However, Khrustalev states that this method will be inadequate, since the required rate of new construction rises exponentially from 5% per decade in 1980–1990 to 108% per decade in 2030– 2040 (assuming a linear increase in mean annual temperature of 0.075 ºC/yr) .
Various methods have been suggested to address temperature-related foundation problems.Techniques to reduce warming and thawing, such as heat pumps, convection embankments, thermosyphons, winterventilated ducts, and passive cooling systems, are already common practice in North America, Scandinavia, and Russia.
Ultraviolet radiation and construction materials (16.3.1)
Ultraviolet (UV) radiation adversely affects many materials used in construction and other outdoor applications. Exposure to UV radiation can alter the mechanical properties of synthetic polymers used in paint and plastics, and natural polymers present in wood. Increased exposure to UV radiation due to stratospheric ozone depletion is therefore likely to decrease the useful life of these materials.
Table 16.9. Projected decrease in the bearing capacity and durability of foundations in Yakutsk for different increases in air temperature.
|Increase in mean annual air temperature (ºC)|
|Bearing capacity of structures built using Principle I (%)||100||93||85||73||50|
|Foundation durability of structures built using Principle II (%)||100||68||46||42||23|
The impact of UV radiation on infrastructure in the Arctic is influenced by two compounding factors: the high surface reflectivity of snow or ice and long hours of sunlight. Both factors have strong seasonal components, generally resulting in increased UV radiation levels in the late spring.While the level of UV radiation incident on a horizontal surface (e.g., a flat roof) may be considerably lower in the Arctic than at mid-latitudes, the level Increase in mean annual air temperature (ºC) of UV radiation incident on a vertical surface (e.g., a south-facing wall) may be higher than that on a horizontal surface at some times of the year, when reflection from snow augments the direct UV radiation incident on the surface. Materials degradation is often related to the total accumulated UV radiation exposure.
Long days during the arctic summer can result in large daily doses of UV radiation, even when noon levels remain moderate. If UV radiation levels increase as a result of ozone depletion or changes in cloud cover, the impacts on materials are likely to include earlier degradation and significant discoloration.
For natural polymers found in wood, exposure to UV radiation can lead to a decrease in the useful lifetime of the product. Even small doses of UV radiation may darken wood surfaces. Other effects of increased exposure to UV radiation on wood are less certain.The damage to finished wood products is limited primarily by protective surface coatings, but increased UV radiation levels will possibly lead to increased costs for more frequent painting or other maintenance.
The construction industry is increasingly turning to synthetic polymers for use in building materials. In the United States and Western Europe, the building sector uses 20 to 30% of the annual production of plastics. Plastics and other synthetic polymer products are used for a number of applications, including irrigation, water distribution and storage, and in fishing nets and agricultural films.
During the manufacture of virtually all polymer products, impurities can be introduced that make the end product susceptible to photodegradation by UV radiation. Although stabilizers may be added to retard photodegradation effects, their inclusion can substantially increase the cost of the final product. Unfortunately, much of the research on UV-induced degradation has been conducted on pure polymer resins, leading to problems in extrapolating the findings to processed products of the same polymer.
The effects of UV radiation on materials are closely tied to other environmental factors, including ambient temperatures. Polar regions have experienced the greatest ozone depletion and therefore the greatest potential increases in UV-B radiation levels. However, the cooler temperatures in these locations can help prevent rapid degradation of materials. Materials have different sensitivities that can depend on wavelength and dose. Some materials contain stabilizers designed to mitigate degradation, but the efficacy of those stabilizers under spectrally altered (e.g., higher than normal UV) conditions is not always known. UV-induced polymer deterioration has been widely observed. Polyvinyl chloride tends to undergo discoloration or yellowing, and to lose impact strength.
This loss of impact strength can eventually lead to cracking and other irreversible damage. Another polymer, polycarbonate, undergoes a rearrangement reaction when exposed to UV-B or UV-C radiation. When irradiated at longer wavelengths, including visible wavelengths, polycarbonates undergo oxidative reactions that result in yellowing. Polystyrene, used as expanded foam in both building and packaging applications, also undergoes light-induced color changes. In polyethylene and polypropylene, which are used extensively in agricultural mulch films, greenhouse films, plastic pipes, and outdoor furniture, the loss of tensile properties and strength is a particular concern. The cost of more frequent replacement of woods and polymers is likely to be higher in the Arctic than at lower latitudes because of the increased cost of shipping and placement. Environmental stresses in the Arctic, including high winds and repeated freezing and thawing, will possibly exacerbate minor materials problems that develop as a result of UV radiation damage.
Several foundation systems are currently in use for industrial, commercial, and residential structures situated in the Arctic and subarctic.When building sites are underlain by permafrost, the foundation system must ensure that any warmth emanating from the structure does not induce thawing of the permafrost layer. For many structures, this is accomplished by elevating the building above the ground surface on a pile or adjustable foundation system. The resulting air space ensures that heat from the structure will not induce permafrost warming. Thousands of structures ranging from single-family residences to large living quarters and apartment blocks are currently supported on pile foundations, including many residential structures in the permafrost zones of Alaska, Canada, and Scandinavia, and many apartment buildings in Siberia.
In most of these areas, existing structures are performing well, and there has been little evidence that climate change is inducing failures. However, as noted in section 16.3.8 many Siberian buildings are experiencing significant rates of structural failure that may be connected to increasing temperatures.
The bearing capacity of piles embedded in permafrost depends on the type of frozen soil (clay, silt, or sand), its temperature, and the length of pile embedment in the permafrost layer. A safe pile design is usually based on the calculated maximum temperatures of the frozen soil along the embedded pile length, determined from data on the mean annual temperature of the site and the seasonal temperature variation. Pile foundations are particularly sensitive to permafrost temperatures because of the large increase in creep rates as temperatures approach 0 ºC (see section 188.8.131.52). For this reason, extra cooling measures, such as the use of thermopiles (thermosyphon-cooled pilings), are some times taken in the warmer discontinuous permafrost zone in order to lower temperatures and ensure a stable permafrost–piling bond.
An increase in ground temperature along an existing pile is very likely to reduce its bearing capacity or increase the rate of its settlement for two reasons: an increase in the active-layer thickness will reduce the effective embedment length of the pile; and increased temperature will reduce the strength of the frozen soil. As a result, if soil warming occurs, an existing structure founded on piles will experience an increasing settlement rate that is likely to lead to uneven settlement and damage to the structure.
The design of all future structures founded on piles embedded in permafrost soils should take into account projected future temperature increases. Depending on the estimated useful lifetime of the structure, the pile design should preferably be based on projected temperature conditions at the end of its lifetime. For any particular pile type, unless bearing on rock, this will result in longer pile length and increased cost. Very light buildings in permafrost areas are often established directly on the ground surface and supported by a system of adjustable mechanical jacks providing a sufficient crawl space below the heated and insulated floor of the building and the ground surface. Although such buildings will not produce thaw settlement of underlying permafrost, they are likely to be subject to the effects of regional thaw settlement due to rising temperatures and the resulting increase in active-layer thickness. Although settlement in these types of buildings can be adjusted by the jacking system, the differential settlement of water supply and sewage evacuation pipes attached to the building must also be addressed. Depending on local meteorological conditions, the foundation soils of buildings constructed on elevated foundation systems (either pile or adjustable supports) are likely to be less prone to temperature increases as climate change occurs. This is due to the combined influence of shielding the surface from solar radiative input (due to shading by the structure) and elimination of snow cover at the surface beneath the building, both of which have a significant cooling effect on groundsurface temperatures.
For industrial and equipment buildings that must support large floor loads, pile foundations are sometimes too costly.These buildings often have a slab-on-grade foundation with insulation installed beneath the floor to help protect the underlying permafrost. In addition to the insulation, some sort of cooling system under the slab is required to remove heat from beneath the structure. Both active and passive refrigeration systems have been employed for this purpose, but passive systems are generally preferred due to their lower operational and maintenance costs. Passive systems are based on either thermosyphon or air-duct cooling systems, and utilize low ambient temperatures during winter to refreeze a buffer layer of non-frost-susceptible material beneath the building.The buffer layer typically consists of a pad of granular material that is placed before building construction and sized to contain the seasonal thaw that develops beneath the building during summer months when the passive cooling system is inactive.
Increasing air temperature is very likely to have a detrimental effect on the operation of these foundation systems for two reasons. Higher air temperatures are likely to lengthen the thaw season and place increased requirements on the thickness of the buffer layer and/or the insulation system, and reduced air freezing indices (section 184.108.40.206) are very likely to decrease the capacity of the passive cooling system to refreeze the buffer layer material during winter.
As a result, existing buildings built on slabs are likely to experience an increasing failure rate as air temperatures rise and produce either significantly longer thaw seasons or a reduced freezing index. Future designs for such buildings will need to take into account temperature increases projected for the lifetime of the structure. This is very likely to increase costs due to the need for additional buffer layer material and higher cooling capacities.
Road and railway embankments and work pads (16.3.3)
Transportation routes are likely to be particularly susceptible to destructive frost action under conditions of changing climate. Garagulya et al. developed a map showing areas with various probabilities of natural hazards. This map indicated that the regions of highest susceptibility to frost heave and thaw settlement are located along the Arctic Circle.
The design of road and railway embankments in the Arctic is complicated by the presence of underlying permafrost, due to the possibility of thaw settlement and significant permanent embankment deformation if thermal disturbance occurs. The situation is exacerbated by complex thermal interactions between the embankment and the surrounding environment. Embankment construction often produces a significant alteration of the surface microclimate that results in an increase in mean annual surface temperature of several degrees as compared to natural conditions. Precise temperature increases are a complex function of embankment surface conditions, maintenance operations (e.g., snow clearing patterns), and the pre-existing natural vegetation, and are sometimes difficult to project.
In the continuous permafrost zone, where the permafrost layer and surface conditions are generally colder, surface warming due to embankment construction can usually be accommodated using well-established design practices. In this case, the embankment thickness is adjusted to ensure that seasonal thawing is contained within the embankment itself, thus avoiding thawing of the underlying permafrost. The required embankment thickness is sensitive to climatic conditions, tending to increase significantly with warmer conditions.
In the discontinuous permafrost zone, permafrost and ground-surface temperatures are warmer, often within a few degrees of the melting point. In this zone, it is more difficult to accommodate surface warming due to embankment construction since the resulting mean surface temperatures are often above the melting point. In this case, long-term thaw of the permafrost layer can be expected and cost-effective design strategies are currently unavailable. In a limited number of cases, techniques such as thermosyphon, air duct, or convection cooling systems have been used to mitigate these problems, however, the expense associated with these systems severely limits their utility. In practice, even under current climatic conditions, many road and railway embankments located in regions of warm discontinuous permafrost experience high failure rates and resulting high maintenance costs. Typical problems include differential thaw settlement and shoulder failure due to thawing permafrost, resulting in an uneven, cracked embankment surface (Fig. 16.20). The timescales associated with permafrost thaw beneath embankments are of the order of the embankment lifetime (20 to 30 years), thus necessitating a continuous maintenance program.
Increasing temperatures are very likely to affect embankment performance in both the continuous and discontinuous permafrost zones and should be considered in the design of future projects. In the discontinuous permafrost zone, the problems associated with permafrost thaw described above are very likely to increase as increasing air temperature adds to the warming influence of embankment construction. This is very likely to result in increased failure rates and higher maintenance costs. As climate change reduces permafrost extent in the southern discontinuous permafrost zone, some reduction in these embankment problems is possible, although the timescales for projected warming and thaw are much longer than typical project lifetimes.
In the continuous permafrost zone, increasing temperatures are likely to have negative impacts on embankment performance for two reasons:
increased surface temperatures will necessitate greater embankment thicknesses in order to contain the seasonal thaw depth. This is very likely to have a large impact on project costs due to the difficulty and expense associated with obtaining appropriate granular material for embankment construction; and
as air and surface temperatures increase, a design regime shift will possibly occur in association with the northward movement of the boundary between the discontinuous and continuous permafrost zones. It is possible that increasing embankment thickness alone will no longer be sufficient to protect underlying permafrost and greater failure rates will occur, similar to those seen in the discontinuous permafrost zone.
As a result, it is likely that existing road, rail, or airport embankments will experience increasing failure rates both in the continuous and discontinuous permafrost zones. Future embankment designs should incorporate the effects of projected temperature increases over the lifetime of the project, which is likely to increase construction costs.
Many of the earth’s remaining oil and gas reserves are located in regions of the Arctic far from population centers. These areas include the North Slope of Alaska, the Canadian Arctic, northwestern Russia, and Siberia. The limited exploitation of these resources to date has relied primarily on pipeline systems to transport products to market. Future expansion of these pipeline networks is likely given the increasing demand for fossil fuels worldwide. Examples include the large gas pipeline projects currently under consideration to connect natural gas reserves in the Alaskan and western Canadian Arctic to southern Canada and the continental United States. Many of the current and anticipated pipeline routes cross extensive areas of continuous and discontinuous permafrost and require special design considerations.
Oil and gas pipelines differ in their interactions with the surrounding environment because of variations in operating temperature.Transmission of oil through pipelines usually takes place at high temperatures because of high oil-well production temperatures and reduced pumping losses. Conversely, natural gas transmission through pipelines often takes place at temperatures below freezing in order to increase gas density and throughput. High- or low-temperature pipelines present different challenges to designers and will react in different ways to increased air temperatures.
Gas and oil pipelines are normally constructed below the ground surface, as this reduces construction costs and provides other benefits. In the case of warm-oil pipelines, this becomes problematic in areas where permafrost is encountered. The desire to keep the oil warm to limit viscosity and pumping costs is in direct conflict with the requirement to maintain the frozen state of the surrounding soil. If the pipeline is buried, no practical amount of insulation will prevent the warm oil from thawing surrounding permafrost, thus resulting in loss of strength, thaw settlement, and probable line failure. As a result, designers have relied on one of two methods to avoid permafrost degradation:
- an elevated oil pipeline that is supported above the ground surface on some sort of pile foundation, thus limiting the possibility of permafrost thaw; or
- a more conventional buried pipeline design, with the oil chilled to near-permafrost temperatures (typically below 0 ºC for a large part of the year).
A major shortcoming of both methods, particularly with regard to potential climate change, is their reliance on the permafrost layer for structural support. In the first case, the piles are embedded in the permafrost, as for a building foundation, and the adfreeze bond between the pile and the permafrost supports the load. In the second case, the integrity of the pipe trench and support of the pipeline are dependent on the structural integrity of the underlying permafrost. Both methods result in increased cost; the first due to the large expense of constructing an elevated line, and the second due to the high pumping costs associated with moving chilled oil and related problems with potential wax formation in the line.
The best-known example of an existing elevated arctic oil pipeline is the Trans Alaska Pipeline System (TAPS), which stretches 1280 km from Prudhoe Bay to the ice-free port of Valdez in southern Alaska. This pipeline is elevated for just over half of its length in order to avoid potential permafrost problems. The northern sections, where permafrost temperatures are cold (lower than approximately -5 ºC), utilize non-refrigerated pile supports and a work-pad embankment designed to protect underlying permafrost. In the more southerly sections, where warmer discontinuous permafrost is encountered, the piles utilize a passive refrigeration system consisting of pairs of thermosyphons installed in each piling. More than 120 000 thermosyphons are used. The thermosyphons are designed to ensure that any excess heat transported downward from the pipeline or entering the ground surface due to construction disturbance will not cause thawing of the permafrost where the piles are embedded.
Owing to the extensive use of pile supports, elevated oil pipelines are sensitive to increasing air and soil temperatures, as are building-support pilings. Increased soil temperatures are very likely to reduce the bearing capacity of these systems because of the reduction in the strength of the adfreeze bond between the frozen soil and the pile. In addition, increased air temperatures are very likely to result in a greater active-layer depth, which will reduce the effective embedment length of the pile in the frozen zone. Some of these effects can be countered by the use of refrigerated piles, as in the case of TAPS; however, increased air temperatures are also very likely to reduce the ability of these systems to provide adequate cooling. It is also possible that the pipeline right-of-way and work-pad embankment will begin to experience increased problems with thaw settlement due to the combination of surface disturbance and increasing air temperature. These factors should be considered during the design stage of future projects.
The Norman Wells Pipeline, which runs 896 km through the western Canadian Arctic from Norman Wells, Northwest Territories, to Zama City, Alberta, is an example of a chilled pipeline that is buried in permafrost terrain.The oil is chilled by a refrigeration system before it enters the line at Norman Wells, and operates at near-ambient permafrost temperatures. Even though the oil is chilled to minimize permafrost disturbance, the designers anticipated a significant amount of thaw settlement and/or frost heave along the route. To resist the anticipated loading due to thaw strain or frost heave, a relatively highstrength system consisting of a small-diameter thickwall pipe was used.Two major design/performance issues were identified as the most significant for this project: adequate thermal conditions must be maintained such that design loads due to thaw settlement or frost heave are not exceeded; and permafrost thaw within the pipeline trench and right-of-way must be limited in order to avoid slope instability (and potential landslides) in areas of sloped terrain.
Variations in line operating conditions have resulted in significant movement of the pipe due to thaw settlement and frost heave. In some places, thaw settlement near the pipeline trench has exceeded the design projections of 1 m, and increases in thaw depth have reduced the factor of safety for slope stability.
Many of the difficult operational issues identified above for buried ambient-temperature pipelines result from the thermal interaction between the pipe and the surrounding ground.These difficulties are likely to be exacerbated if air temperatures also change over time. Increased air temperatures are likely to aggravate problems with thaw settlement along the right-of-way and decrease slope stability.To some extent, it may be possible to reduce the severity of these problems by decreasing the operational temperatures of the pipeline, however this is not desirable because of the high pumping cost and wax formation issues mentioned previously. New projects should take projected temperature increases into account during the design stage and may have to increase measures designed to prevent slope instability and settlement associated with permafrost thaw.
Unlike oil pipelines, gas pipelines benefit from lowtemperature operation and are often operated at temperatures significantly below the freezing point.When these pipelines are buried in continuous permafrost, they aid the maintenance of the permafrost layer and design is straightforward. On the other hand, where chilled buried pipelines must traverse zones of discontinuous permafrost, problems can be expected. In this case, the chilled pipeline will cause freezing of the thawed soil present along the route, some of which may be susceptible to frost.The resulting frost-heave loads on the pipe can be large and must be accounted for carefully. Previous studies have suggested that line operation temperatures should be kept only moderately below freezing in these areas in order to minimize frost-heave problems while, at the same time, avoiding thaw settlement in the permafrost portions of the route. Increased air temperatures will possibly expand the problematic portion of these pipeline routes as the boundary between continuous and discontinuous permafrost moves northward. However, the ability to control pipeline operating temperatures may help to adapt to changing climatic conditions.
Water-retaining structures (16.3.5)
Water-retaining embankments in permafrost are discussed in detail by Andersland and Ladanyi, and are generally one of two types: unfrozen embankments or frozen embankments.With unfrozen embankments it is assumed that the permafrost foundation will thaw during the lifetime of the structure. This type is limited to sites with thaw-stable foundation materials or bedrock, or cases where the water is retained for a short period of time.With frozen embankments it is assumed that the permafrost foundation will remain frozen during the lifetime of the structure. This type is suitable for continuous permafrost areas and other areas where the foundation materials are thaw-unstable.
The embankment design for a particular site must combine the principles of soil mechanics for unfrozen soils and the mechanical behavior of permafrost.The design should always include thermal and stability considerations, and for permanent structures, potential climate change should be taken into account. Sayles and Holubec et al. have summarized the factors that are relevant to embankment design.
Problems associated with water-retaining dams include seepage, frost heave (in areas of seasonal frost), settlement, slope stability, slope protection, and construction methods. Increased air temperatures are not likely to affect unfrozen embankments because the permafrost foundation is thaw stable. Frozen embankments usually require supplementary artificial freezing to ensure that the foundation and embankment remain frozen. Increased air temperatures are likely to increase the construction and operational costs of frozen embankments due to the increased energy demand required to keep the embankment frozen.
Off-road transportation routes (16.3.6)
In recent years, temporary winter transportation routes have played an increasingly important role for community supply and industrial development in the permafrost zones of North America. These transportation corridors consist of ice roads that traverse frozen lakes, rivers, and tundra. In some cases, ice roads are constructed for one-time industrial mobilizations, such as oil and gas exploration activities. In other cases, permanent ice-road corridors have been established and are reopened each winter season.Winter ice roads offer important advantages that include low cost and minimal impact to the environment. Oil and gas exploration can be conducted from these road structures with very minimal ecological effects, and costs associated with construction and eventual removal of more permanent gravel roads or work pads can be avoided.
Winter ice-road construction is affected by a number of climatic factors, including air temperature, accumulated air freezing index, and snowfall. These roads depend on the structural integrity of the underlying frozen base material and, thus, a significant period of freezing temperature must occur each autumn before ice-road construction can begin. For water crossings, the critical factor influencing the start of the winterroad season is the rate and amount of ice formation. Ice thickness must reach critical minimum values before vehicles and freight can be supported safely. For tundra areas (particularly where temporary transportation routes are needed), a critical issue is protection of the existing vegetative cover. In this case, the active layer must be frozen to a depth that is sufficient to support anticipated loads and avoid damage to vegetation. Once a sufficient frozen layer has been established, the surface is covered with snow and water is applied and allowed to freeze in place. The result is a durable driving surface that can support significant loads without harming the underlying vegetation.
In North America, winter-road use and construction is regulated to avoid environmental damage to the tundra.Various inspection techniques are used to ensure adequate freezing before the winter-road season is opened. One technique employs a penetrometer that is pushed into the frozen active layer to measure the strength and thickness of the frozen zone. Based on these measurements, regulatory agencies make decisions regarding opening and closing dates for winter-road travel.
Climatic conditions play a strong role in determining the opening and closing dates for winter-road travel, although inspection techniques and load requirements, among other factors, are also important. Increased air temperature and reductions in the annual air freezing index are very likely to have a negative impact on the duration of the winter-road season. This will possibly become particularly problematic for oil and gas exploration because of the time needed at the beginning and end of the ice-road season for mobilization and demobilization.
Hinzman et al. (in press) present historic data for the opening and closing dates for tundra travel on the North Slope of Alaska that show a substantial reduction in the duration of the winter-road season (from over 200 days in the early 1970s to just over 100 days in 2002). The rate of reduction has been fairly consistent over the intervening years and is due primarily to delayed opening dates (from early November in the 1970s to late January in the 2000s), although closing dates have also been occurring earlier in the spring. Reductions in the duration of the winter-road season have also occurred in the Canadian Arctic, however the reductions are much smaller than those observed in Alaska, and in some cases the season length has increased.
Fig. 16.21 shows historic data for opening and closing dates of winter roads on the North Slope of Alaska and in Canada’s Northwest Territories.The data for the North Slope are for temporary winter roads used primarily for oil and gas exploration, whereas the data for the Northwest Territories are for the winter roads between Inuvik and Tuktoyaktuk (187 km) and between the Yellowknife Highway and Wha Ti (103 km).The figure illustrates the reduction in season length for the North Slope of Alaska, and a trend of later opening dates for the Wha Ti road. Data for the Inuvik- Tuktoyaktuk road, however, indicate an increased season length.
The observed trend in Alaska shows that climate change is likely to lead to decreased availability of offroad transportation routes (ice roads, snow roads, etc.) due to reduced duration of the freezing season.
Offshore transportation routes (16.3.7)
The global economy of the 21st century will need the natural resources of the Arctic and subarctic. Air transport remains unprofitable for mineral payloads and attention to arctic shipping is growing as a result. Road, rail, and pipeline routes are complicated in the far north by tectonically active glacier-contorted landscapes, low-lying frozen ground, and fragile ecosystems. Shorter routes from resource to tidewater minimize terrestrial complications only if a port can be built at the coast. New ice-breaking ship designs are continually improving the efficiency of arctic shipping. Growing evidence of climate change indicates that icefree navigation seasons will probably be extended and thinner sea ice will probably reduce constraints on winter ship transits (section 16.2.5). Additional northern port capacity is critical to the success of arctic shipping strategies associated with northern resource development and potential climate change. Difficulties related to freezing temperatures, snow accumulation, and extended darkness compound the challenges of geotechnical, structural, architectural, mechanical, electrical, transportation, and coastal engineering in designing and operating sea and river ports.
The International Northern Sea Route Programme was a six-year (June 1993 – March 1999) international research program designed to create an extensive knowledge base about the ice-infested shipping lanes along the coast of the Russian Arctic, from Novaya Zemlya in the west to the Bering Strait in the east. This route was previously named the Northeast Passage, but is now more often known by its Russian name – the Northern Sea Route.
Projected reductions in sea-ice extent are likely to improve access along the Northern Sea Route and the Northwest Passage. Projected longer periods of open water are likely to foster greater access to all coastal seas around the Arctic Basin.While voyages across the Arctic Ocean (over the pole) will possibly become feasible this century, longer navigation seasons along the arctic coasts are more likely. Development of the offshore continental shelves and greater use of coastal shipping routes will possibly have significant social, political, and economic consequences for all residents of arctic coastal areas.
Output from the five ACIA-designated climate models was used to project the length of the navigation season along the Northern Sea Route based on the amount of sea ice present. Figure 16.22 shows the five-model mean for three conditions: 25, 50, and 75% open water across the Northern Sea Route. If ships sailing along the Northern Sea Route are designed for and capable of navigating in waters with 25% open water (75% sea-ice cover), the projected length of the navigation season is considerably longer than that for ships that are minimally ice-capable and can only navigate in 75% open water (25% sea-ice cover).
There are few days when, even at mid-century, the Northern Sea Route is covered by 75% open water (25% sea-ice cover).When days on which navigation is possible are defined by a higher ice-cover percentage, the length of the navigation season increases. In 2050, Fig. 16.22 shows a projected navigation season length of 125 days under conditions of 25% open water (75% sea-ice cover); conditions very favorable for the transit of ice-strengthened cargo ships. However, the ACIA designated model projections provide no information on sea-ice thickness, a critical factor for ice navigation. Section 220.127.116.11 provides additional projections of future sea-ice conditions.
With increased marine access to arctic coastal seas, national and regional governments are likely to be called upon for increased services such as icebreaking assistance, improved sea-ice charts and forecasting, enhanced emergency response capabilities for sea-ice conditions, and greatly improved oil–ice cleanup capabilities. The sea ice, although thinning and decreasing in extent, will possibly become more mobile and dynamic in many coastal regions where fast ice was previously the norm. Competing marine users in newly open or partially icecovered areas in the Arctic are likely to require increased enforcement presence and regulatory oversight.
A continued decrease in arctic sea-ice extent this century is very likely to increase seasonal and year-round access for arctic marine transportation and offshore development. New and revised national and international regulations, focusing on marine safety and marine environmental protection, are likely to be required as a result of these trends. Another probable outcome of changing marine access will be an increase in potential conflicts between competing users of arctic waterways and coastal seas.
Based on the scenarios presented in this section and in section 18.104.22.168, a longer navigation season along the arctic coast is very likely and trans-arctic (polar) shipping is possible within the next 100 years.
Damage to infrastructure (16.3.8)
Instanes A. pointed out that for structures on permafrost it is often difficult to differentiate between the effect of temperature increases and other factors that may affect a structure on permafrost. For example: the site conditions are different from the assumed design site conditions; the design of the structure did not take into account appropriate load conditions, active-layer thickness, and permafrost temperature; the contractor did not carry out construction according to the design; the maintenance program was not carried out according to plan; and/or the structure is not being used according to design assumptions. In addition, it is very difficult to find cost-effective engineering solutions for foundations or structures on warm (T >-1 ºC), discontinuous permafrost.
Kronik summarized reports on damage to infrastructure in Russian permafrost areas from the 1980s to 2000. The reported deformations of foundations and structures were caused not only by climate change, but also by other factors such as those listed above, particularly the low quality and inadequate maintenance of structures. Unfortunately, it is difficult to distinguish between these factors. The analysis of deformation causes performed by Kronik for industrial and civil complexes showed that 22, 33, and 45% of the deformations were due to mistakes by designers, contractors, and maintenance services, respectively. Out of 376 buildings surveyed, 183 (48.4%) did not meet building code requirements in 1992, including 21 buildings (8.5%) that were unfit for use. The percentage of dangerous buildings in large villages and cities in 1992 ranged from 22% in the village of Tiksi to 80% in the city of Vorkuta, including 55% in Magadan, 60% in Chita, 35% in Dudinka, 10% in Noril’sk, 50% in Pevek, 50% in Amderma, and 35% in Dikson.
The condition of land transportation routes in Russia is not much better. In the early 1990s, 10 to 16% of the subgrade in the permafrost areas of the Baikal–Amur railroad line was deformed because of permafrost thawing; this increased to 46% in 1998. The majority of runways in Norilsk,Yakutsk, Magadan, and other cities may be closed for shorter or longer periods due to lack of maintenance. The main gas and oil transmission lines in the permafrost region have also suffered damage related to permafrost thawing: 16 breaks were recorded on the Messoyakha–Noril’sk pipeline in 2000.
Energy consumption for heating (16.3.9)
A reduction in the demand for heating energy is a potential positive effect of climate change in the Arctic and subarctic. The air-temperature threshold that defines the beginning of the cold period, when additional heating of living facilities, businesses, and industrial buildings is necessary, varies within and between countries. In North America and Western Europe, most civil buildings, private houses, apartment complexes, and even most buildings in large cities have local heating systems. In the United States the temperature threshold for heating is defined as 65 ºF (17.8 ºC), but because the local systems are very flexible and can be manipulated individually, evaluation of energy consumption is complex.
In Eastern Europe and Russia, most urban buildings have centralized heating systems. Under standard con- ditions, such systems operate when the mean daily air temperature falls below 8 ºC (47 ºF). Because of the large thermal inertia of these centralized heating systems, comfortable indoor temperatures (e.g., 18 ºC) are usually maintained throughout the winter.
Figure 16.23 shows the annual demand for heating energy (in 1000 ºC-days) when building heating is required (mean daily air temperature below 8 ºC) calculated for current climatic conditions. Annual heating degree-day totals characterize the demand for heating over the entire cold period. Daily heating degree-days are calculated by subtracting the mean daily temperature from the 8 ºC threshold (e.g., a day with a mean daily temperature of 5 ºC would result in three heating degree-days); days with a mean temperature at or above 8 ºC result in zero heating degree-days.
Anisimov used the GFDL, ECHAM-1 (Max- Planck Institute for Meteorology), and HadCM transient climate scenarios for 2050 to calculate the reduction in the duration of the heating period and changes in the number of heating degree-days relative to 1999. Projected reductions in the number of heating degree-days (Fig. 16.24) can be used as a metric for the reduction in heating energy consumption. Figure 16.25 shows the percentage reduction in the duration of the heating period between 1999 and 2050; this decrease is projected to vary from a few weeks to more than a month, depending on the regional effects of climate change.
The energy savings from decreased demand for heating in northern regions are likely to be offset by increases in the temperature and duration of the warm period, leading to greater use of air conditioning.
Natural resources (16.3.10)
The Arctic has large oil and natural gas reserves. Most are located in Russia: oil in the Pechora Basin, natural gas in the Lower Ob Basin, and other potential oil and gas fields along the Siberian coast. Canadian oil and gas fields are concentrated in two main basins in the Mackenzie Delta–Beaufort Sea region and in the high Arctic. Prudhoe Bay (Alaska) is the largest oil field in North America, and other fields have been discovered or are likely to be present along the Beaufort Sea coast. Oil and gas fields also exist in other arctic waters, for example, the Barents Sea and off the west coast of Greenland. The Arctic is an important supplier of oil and gas to the global market, and it is possible that climate change will have both positive and negative financial impacts on the exploration, production, and transportation activities of this industry.
Climate change impacts on oil and gas development have so far been minor, but are likely to result in both financial costs and benefits in the future. For example, offshore oil exploration and production is likely to benefit from less extensive and thinner sea ice because of cost reductions in the construction of platforms that must withstand ice forces. Conversely, ice roads, now used widely for access to offshore activities and facilities, are likely to be useable for shorter periods and less safe than at present. The thawing of permafrost, on which buildings, pipelines, airfields, and coastal installations supporting oil development are located, is very likely to adversely affect these structures and the cost of maintaining them.
The Arctic holds large stores of minerals, ranging from gemstones to fertilizers. Russia extracts the largest quantities, including nickel, copper, platinum, apatite, tin, diamonds, and gold, mostly on the Kola Peninsula but also in Siberia. Canadian mines in the Yukon and Northwest Territories supply lead, zinc, copper, and gold. Gold mining continues in Alaska, along with extraction of lead and zinc deposits from the Red Dog Mine, which contains two-thirds of US zinc resources. Coal mining also occurs in several areas of the Arctic. Mining activities in the Arctic are an important contributor of raw materials to the global economy and are likely to benefit from improved transportation conditions to bring products to market, due to a longer ice-free shipping season.
The coal and mineral extraction industries in the Arctic are important contributors to national economies, and the actual extraction process is not likely to be much affected by climate change. However, climate change will possibly affect the transportation of coal and minerals. Mines that export their products using marine transport are likely to experience savings due to reduced sea-ice extent and a longer shipping season. Conversely, mining facilities with roads on permafrost are likely to experience higher maintenance costs as the permafrost thaws.
Any expansion of oil and gas activities and mining is likely to require expansion of air, marine, and land transportation systems. The benefits of a longer shipping season in the Arctic, with the possibility of easy transit through the Northern Sea Route and Northwest Passage for at least part of the year, are likely to be significant. Other benefits are likely to include deeper drafts in harbors and channels as sea level rises, a reduced need for ice strengthening of ship hulls and offshore oil and gas platforms, and a reduced need for icebreaker support. Conversely, coping with greater wave heights, and possible flooding and erosion threats to coastal facilities, is likely to result in increased costs.
Chapter 16: Infrastructure: Buildings, Support Systems, and Industrial Facilities
16.2. Physical environment and processes related to infrastructure
16.2.1. Observed changes in air temperature
16.2.3. Natural hazards
16.2.4. Coastal environment
16.2.5. Arctic Ocean
16.3. Infrastructure in the Arctic
16.4. Engineering design for a changing climate
16.5. Gaps in knowledge and research needs
^Anisimov, O.A. and M.A. Belolutskaia, 2002. Effects of changing climate and degradation of permafrost on infrastructure in northern Russia. Meteorology and Hydrology, 9:15–22. (In Russian);
-- Nelson, F.E., O.A. Anisimov and N.I. Shiklomanov, 2002. Climate change and hazard zonation in the circum-Arctic permafrost regions. Natural Hazards, 26(3):203–225.
- ^North Slope data after Hinzman et al., in press; Canadian data from the Government of the Northwest Territories, Department of Transportation, www.hwy.dot.gov.nt.ca/highways/, 2003)
- ^Anisimov, O.A., 1999. Impacts of anthropogenic climate change on heating and air conditioning of buildings. Meteorology and Hydrology, 6:10–17. (In Russian)
- ^Freitag, D.R. and T. McFadden, 1997. Introduction to Cold Regions Engineering. ASCE Press, 738pp.
^see also Bush, E., D.A. Etkin, D. Hayley, E. Hivon, B. Ladanyi, B. Lavender, G. Paoli, D. Riseborough, J. Smith, and M. Smith, 1998. Climate Change Impacts on Permafrost Engineering Design. Environment Canada, Environmental Adaptation Research Group, Downsview, Ontario.;
-- Nixon, 1994)
- ^ Nixon, J.F., 1994. Climate Change as an Engineering Design Consideration. Report prepared by Nixon Geotech Ltd. for the Canadian Climate Centre, Environment Canada, Downsview, Ontario, 11 pp.
^Szymanski, M.B., A. Zivkovic, A.Tchekovski and B. Swarbrick, 2003. Designing for closure of an open pit in the Canadian Arctic. In: M. Phillips, S.M. Springman and L.U. Arenson (eds.). Permafrost: Proceedings of the Eighth International Conference on Permafrost, pp. 1123–1128. A.A. Balkema.;
-- Bush et al., 1998, Op. cit.
- ^ AMAP, 1998. AMAP Assessment Report: Arctic Pollution Issues. Arctic Monitoring and Assessment Programme, Oslo, xii+859pp.
^Anisimov and Belolutskaia, 2002, Op. cit.;
--Nelson F. et al., 2002, Op. cit.
- ^Andersland, O.B. and B. Ladanyi, 1994. An Introduction to Frozen Ground Engineering. Chapman & Hall, 352pp.
^Khrustalev, L.N., 2000. Allowance for climate change in designing foundations on permafrost grounds. In: International Workshop on Permafrost Engineering, Longyearbyen, Norway, 18–21 June, 2000, pp. 25–36.Tapir Publishers.
-- Khrustalev, L.N., 2001. Problems of permafrost engineering as related to global climate warming. In: R. Paepe and V.P. Melnikov (eds.). NATO Advanced workshop on Permafrost Response on Economic Development, Environmental Security and Natural Resources, Novosibirsk, Russia, 12–16 November 1998, pp. 407–423. Kluwer Academic Publishers.
- ^ Ibid.
^Andersland and Ladanyi, 1994, Op. cit.;
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-- Goering, D.J. and P. Kumar, 1996.Winter-time convection in open-graded embankments. Cold Regions Science and Engineering, 24:57–74.;
-- Instanes, B., 2000. Permafrost engineering on Svalbard. In: Proceedings of the International workshop on Permafrost Engineering, Longyearbyen, Svalbard, 18–21 June, 2000, pp. 3–23. Tapir Publishers.;
-- Khrustalev, L.N. and V.V. Nikiforov, 1990. Permafrost Stabilization in the Construction Basements. Nauka, Novosibirsk, 353pp.;
-- Smith, S.L., M.M. Burgess and J.A. Heginbottom, 2001. Permafrost in Canada, a challenge to northern development. In: G.R. Brooks (ed.). A Synthesis of Geological Hazards in Canada. Geological Survey of Canada Bulletin 548, pp. 241–264.
- ^Andrady, A.L., S.H Hamid, X. Hu and A.Torikai, 1998. Effects of increased solar ultraviolet radiation on materials. Journal of Photochemistry and Photobiology B, 46:96–103.
- ^Khrustalev, 2000, Op. cit.
- ^Mader, F.W., 1992. Plastics waste management in Europe. Macromolecular Symposia, 57:15–31.
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- ^Factor, A.,W.V. Ligon, R.J. May and F.H. Greenburg, 1987. Recent advances in polycarbonate photodegradation. In: A.V. Patsis (ed.). Advances in Stabilization and Controlled Degradation of Polymers II, pp. 45–58.Technomic, Lancaster, Pennsylvania.
^Hamid, S.H. and W. Pritchard, 1991. Mathematical modeling of weather-induced degradation of polymer properties. Journal of Applied Polymer Science, 43:651–678.;
-- Hamid, S.H., M.B. Amin and A.G. Maadhah, 1995.Weathering degradation of polyethylene. In: S.H. Hamid, M.B. Amin and A.G. Maadhah (eds.). Handbook of Polymer Degradation. Marcel Dekker.
- ^Garagulya, L.S., G.I. Gordeeva and L.N. Khrustalev, 1997. Zoning of the permafrost area by the impact of human-induced geocryological processes on environmental conditions. Kriosfera Zeml, 1(1):30–38.
^Andersland and Ladanyi, 1994, Op. cit.;
-- Goering, D.J., 2003. Passively cooled railway embankments for use in permafrost areas. Journal of Cold Regions Engineering, 17(3):119–133.;
-- Goering and Kumar, 1996, Op. cit.;
-- Instanes, B., 2000, Op. cit.;
-- Phukan, A., 1985. Frozen Ground Engineering. Prentice-Hall Inc. 336pp.
- ^Sorensen, S., J. Smith and J. Zarling, 2003.Thermal performance of TAPS heat pipes with non-condensable gas blockage. In: M. Phillips, S.M. Springman and L.U. Arenson (eds.). Permafrost: Proceedings of the Eighth International Conference on Permafrost, pp. 1097–1102. Balkema.
- ^Nixon et al., 1984, Op. cit.
- ^ Burgess, M.M. and S.L. Smith, 2003. 17 years of thaw penetration and surface settlement observations in permafrost terrain along the Norman Wells pipeline, Northwest Territories, Canada. In: M. Phillips, S.M. Springman and L.U. Arenson (eds.). Permafrost: Proceedings of the Eighth International Conference on Permafrost, pp. 1073–1078. A.A. Balkema.
- ^Oswell, J.M., A.J. Hanna and R.M. Doblanko, 1998. Update on the performance of slopes on the Norman Wells Pipeline Project. In: Proceedings of the Seventh International Conference on Permafrost,Yellowknife, North West Territories.
- ^Jahns, H.O. and C.E. Heuer, 1983. Frost heave mitigation and permafrost protection for a buried chilled-gas pipeline. In: Proceedings of the Fourth International Conference on Permafrost, Fairbanks, Alaska, July 1983, pp. 531–536. National Academy Press.
- ^ Andersland and Ladanyi, 1994, Op. cit.
^Sayles, F. H. 1984. Design and performance of water-retaining embankments in permafrost. In: North American Contribution, Second International Conference on Permafrost, Fairbanks, Alaska, July 17–22 1983. Final Proceedings, pp. 31–42. National Academy Press.
-- Sayles, F.H. 1987. Embankment dams on permafrost: design and performance summary. US Army Cold Regions Research Engineering Laboratory, Special Report 87–11.
- ^ Holubec, I., X. Hu, J.Wonnacott, R. Olive and D. Delarosbil, 2003. Design, construction and performance of dams in continuous permafrost. In: M. Phillips, S.M. Springman and L.U. Arenson (eds.). Permafrost: Proceedings of the Eighth International Conference on Permafrost, pp. 425–430. A.A. Balkema.
- ^ Andersland and Ladanyi, 1994, Op. cit.
- ^Instanes, A., 2003. Climate change and possible impact on Arctic infrastructure. In: M. Phillips, S.M. Springman and L.U. Arenson (eds.). Permafrost: Proceedings of the Eighth International Conference on Permafrost, pp. 461–466. A.A. Balkema.
- ^ Kronik,Ya.A., 2001. Accident rate and safety of natural–anthropogenic systems in the permafrost zone. In: Proceedings of the Second Conference of Russian Geocryologists, vol. 4, pp. 138–146.
- ^ Ibid.
- ^see also Panova,Y.V., 2003. Permafrost processes inducing disastrous effects in engineering constructions, Medvezhje gas-field, Western Siberia. In: M. Phillips, S.M. Springman and L.U. Arenson (eds.). Permafrost: Proceedings of the Eighth International Conference on Permafrost, pp. 121–122. A.A. Balkema
- ^Kronik, 2001, Op. cit.
- ^ Anisimov, 1999, Op. cit.
^Parker,W.B., 2001. Effect of permafrost changes on economic development, environmental security and natural resource potential in Alaska. In: R.Paepe and V.P. Melnikov (eds.). NATO Advanced workshop on permafrost response on economic development, environmental security and natural resources, Novosibirsk, Russia, 12–16 November 1998. pp. 293–296. Kluwer Academic Publishers.;
-- Weller, G. and M. Lange, 1999. Impacts of climate change in Arctic regions. Report from a workshop on the Impacts of Global Change, Tromsø, Norway, 25–26 April, 1999. International Arctic Science Committee, Oslo, 59pp.
-- Weller, G., P. Anderson and B.Wang, 1999. Preparing for a Changing Climate.The Potential Consequences of Climate Variability and Change. A Report of the Alaska Regional Assessment Group for the U.S. Global Change Research Program. Center for Global Change and Arctic System Research, Fairbanks, Alaska.