Causes, Effects, and Impacts
Barrie Maxwell
It has always been difficult to develop a comprehensive picture of the surface climate of the Canadian Arctic. Even today, with a network of observing stations in place, data coverage over the inland and offshore areas is sparse, and variations in the degree to which existing stations are indicative of their surrounding area present an additional problem. So far, satellite information has tempered this difficulty only to a modest extent.
The large expanse of the Canadian Arctic makes it unwise to generalize about the area as a whole. At any given time, one region may be experiencing warm conditions while another is relatively cool. As well, even when widely separated regions (for example, the Mackenzie Valley and Baffin Island) do experience similar conditions, magnitudes may differ substantially.
Past Climate
Our knowledge of the Arctic's past climate becomes less certain the further back we go in history. This may seem obvious, but it is worth emphasizing because dates and locations put forward tentatively in scientific papers tend to become gospel with repetition over time.
As our best evidence of present-day surface climate is that provided by modem instruments, one can readily appreciate the difficulty involved in constructing reliable profiles of climatic conditions existing in the distant past. For such studies it has been necessary to use secondary sources such as books, diaries, and logs (those maintained by posts of the Hudson's Bay Company in the 19th century are a good example), as well as natural indicators of climatic change such as glacier movements and ice cores, tree rings, fossils (particularly pollen and larger plant fragments), soils, and archaeology.
In looking at the past climate of the Arctic, three recent time periods can be considered: geologic-130 000 years before present (BP) to 10 000 BP; Holocene-10 000 BP to 1880 AD; and historic-1880 AD to the present. At the start of the last glaciation, temperatures were not much different from those of today, although precipitation was probably greater. During the course of glaciation, conditions in the Arctic became increasingly colder and drier so that by 15 000 BP, summer temperatures on Baffin Island were perhaps 4°C less than today and annual precipitation was one-third or less of present values. During the last 5000 years of the geologic period, and continuing for the first half of the Holocene, the Arctic became increasingly warmer and wetter, reaching a peak about 5000 BP. At this peak, annual mean temperatures ranged anywhere from 3° C to 4°C greater than at present over the arctic islands to as much as 11 °C greater over the lower Mackenzie Basin.
During the last half of the Holocene, arctic climate has alternated between periods warmer and cooler than today. For example, the years between 2000 BP and 1000 BP were generally warmer than both the thousand or so preceding years and much of the time since.
Over the period of instrumental or historic record, the northern hemisphere has experienced three distinct phases: a general warming trend from the 1880s until the 1940s, a period of cooling until the mid 1960s, and a modest warming thereafter. The Canadian Arctic has reflected a similar pattern, although certain regions, such as the eastern Arctic, have exhibited rather different and more complex patterns, particularly on a seasonal basis.
Contemporary Influences
A number of factors currently influence world climate, and changes in them can significantly alter the climate conditions to which we are accustomed.
Greenhouse Effect
The earth's climate is closely linked to the chemical composition of the atmosphere. Within the atmosphere, certain gases are strongly active in influencing the radiation balance because they allow sunlight (shortwave radiation) to enter the atmosphere fairly freely, but then absorb much of the long-wave radiation given off by the earth's surface. The current concentrations of such gases maintain the climate conditions that we now experience. Among these "greenhouse" gases are carbon dioxide and water vapour, supplemented by traces of methane, nitrous oxide, chlorofluorocarbons, and others. Should the concentrations of these gases increase, the ability of the atmosphere to trap long-wave radiation will also increase, with rising global temperatures the consequence.
It appears that such a trend is occurring, with measured concentrations of carbon dioxide having increased by more than 8 per cent since 1960 and by approximately 25 per cent since the beginning of the industrial revolution. The burning of fossil fuels such as oil, gas, and coal, and extensive deforestation are significant contributors. It now seems likely that the atmospheric concentration of carbon dioxide will double within the next 100 years and that other greenhouse gases will also be found in greater abundance.
Although the carbon dioxide effect has received the most attention, other factors such as increased aerosol abundance, variation of incoming solar radiation, changes in surface characteristics, and releases of waste heat are also important because they may either amplify or mask the effects of carbon dioxide-induced climatic change.
Aerosol Abundance
Aerosol influences differ depending on the location and manner of their injection into the atmosphere; for example, volcanic eruptions can inject large amounts of sulphur dioxide and other material into the stratosphere. It is generally believed that increases in such materials would warm the stratosphere and lead to a cooling of the ground and troposphere. Tropospheric aerosols, so-named because their occurrence is restricted to the lower 10 km of the atmosphere, tend to have a regional rather than global influence. This can vary markedly because of differing optical properties that depend on composition and particle size. Distinct aerosols can be identified in connection with soot and sulphate occurrence, and with desert, maritime, and arctic locations.
Over the Arctic Basin, for example, a diffuse haze layer generally characterized by persistent winter and spring occurrence can be observed. This arctic haze probably results from the long-range transport of man-made, mid-latitude pollution originating in the central and western Eurasian regions. The most obvious potential impact of arctic haze is a surface heating effect, as the aerosol has an absorptive nature and overlies a highly reflective surface.
Solar Radiation Variation
Variations in solar irradiance are highly significant for the determination of both past and future climate because energy from the sun drives both the chemistry of the atmosphere and the climate. The total amount of solar irradiance at the top of the atmosphere was once believed to be constant, but recent satellite-based measurements have revealed that such is not the case.
The slight variations detected may be related to changes in sunspot activity and in the solar radius itself, or to the effects caused by the earth's eccentric orbit around the sun. Calculations of the magnitude of the solar effect on climate are still preliminary, but they suggest that the effect may make it more difficult to detect and interpret trends caused by anthropogenic influences such as carbon dioxide.
Other Factors
The same difficulty may result from the effect of other factors such as alteration of surface characteristics and release of waste heat. In the Arctic, the former is of particular concern, as any significant alteration of the highly reflective ice and snow surface tends to feed back on itself, reinforcing the original effect, whether that be melting of the ice cover or an increase in its geographic extent.
Future Trends
In attempting to develop a picture of the arctic climate over the next 100 years, several techniques are used. This work is based on the consensus among most scientists that an increase in carbon dioxide concentration will play a dominant role, resulting in significant warming of the earth's climate.
One approach involves the development of sophisticated computer models of global climate incorporating a doubled carbon dioxide concentration. Another method reconstructs the patterns of the earth's climate during past warm periods when conditions were comparable to those expected under carbon dioxide-induced warming. Results from both approaches have limitations, but they do provide important clues in characterizing the expected climatic change. That change is likely to take the form of a global warming in the range of 1.5°C to 4.5°C by the latter half of the next century, although there will be considerable variation on a regional basis.
In the Arctic, feedback between radiation and highly reflective ice and snow surfaces, as well as the presence of a strong, surface-based temperature inversion, cause energy to be trapped near the surface. As a result, arctic warming would not only be higher than that at lower latitudes, but also seasonally dependent. Thus, warming is likely to comprise winter increases of 8°C to 10 °C and summer increases of 1°C to 2°C.
Associated with this warming will be increased penetration of the Arctic by storm systems previously confined to the mid-latitudes. This will result in increased moisture availability and windiness on average. For example, mean annual precipitation is expected to increase by 20 to 30 per cent over current levels.
Impacts
In the Arctic, the impacts of these types of climatic changes on the physical environment, on biological processes, and on social and economic concerns are likely to be profound. It should, however, be noted that much of what we can surmise is based on educated, subjective assessment. This is simply because the atmosphere and the arctic environment are complex systems both in themselves and in terms of their interaction.
It is for this reason that our efforts must be devoted to reaching a better understanding of the relationships between climate and the physical environment, as well as the sensitivity of biological, social, and economic activity (for example, offshore development) to climate. The other benefit of such an approach is the opportunity it affords to assess the importance of climate variability (that is, climate changes from year to year) in those same areas of concern. For some of them, this may be as great a problem as the long-term issue of climatic change. In any event, it is only after such understanding has been developed that we can begin to make statements about the true impact of future climatic change in the Arctic with any degree of confidence. Bearing this in mind, the following are possible influences of climatic warming in the Canadian Arctic by the latter half of the next century.
Physical Environment
Snow and Ice
As more and more variables come into play, impacts become increasingly difficult to assess; for example, lake ice, snow cover, glaciers, and sea ice will be affected by climatic change in very different ways:
Permafrost
Climatic impacts on permafrost are complicated by local variations in orography, moisture, and surface type. With future warming, it is inevitable that large areas of permafrost will eventually disappear. Within the next century, however, the greatest impacts will probably be seen in changes in permafrost-related processes resulting from a deepening active layer. These may include: an increase in slope movement due to mud flows, skin flows and slumping; fewer and smaller ice wedges and pingos; and uncertain changes in mechanical soil properties such as creep and relaxation effects.
Biological Impacts
Vegetation
Warmer temperatures and more precipitation will tend to favour vegetation, both with respect to amount and diversity. More rapid change is likely on the mainland than among the islands of the high Arctic where species movement is restricted by waterways. Mainland locations will typically see increases in growing degree-days of 30 to 40 per cent, with the frost-free period lengthening by 20 to 40 per cent. The treeline will eventually move north 200 to 300 kilometres, and the tundra will shrink back to the archipelago. The greatest new growth will likely occur in southern Yukon and Labrador.
Wildlife
Wildlife will experience generally improved environmental conditions. With the northward shift of the boreal forest, animal and bird species unique to the tundra and taiga might be diminished and replaced by more southerly ones. As with vegetation, changes will come more slowly among the arctic islands. Increased winter snow depths may pose problems for current foraging and nesting patterns, with resultant alterations in the locations of traditional wildlife habitats. Inland and ocean fisheries will become more productive due to increased water volumes, water temperature, and food supply.
Socio-Economic Impacts
Petroleum
Offshore hydrocarbon activities, for which sea ice and extreme winter cold have been obstacles, should see enhanced viability. Decreased ice thickness and extent, and the disappearance of multi-year ice would result in a reduced need for specialized drilling and transportation technologies because of the lower risk of damage to ships, oil rigs, and other marine structures. Consequently, design and construction costs would decrease, and delays in operation would be reduced, as would the chance of loss of life. These positive aspects would be tempered by increased concerns over wind. waves, and icebergs.
Transportation
Marine transportation will benefit from an extended season of between six and eight weeks and from the reduced impact of multi-year ice, with attendant savings in types and usage of vessels, insurance, maintenance and repairs, and construction costs. On the other hand, rougher seas and increased iceberg occurrence will present more significant problems than is now the case. Land transportation will eventually benefit from shifts in the permafrost zone, but on the time-scale considered here, a deepening active layer could have negative impacts on routes and require new techniques. For air transportation, increased winter storminess should result in generally poorer flying conditions. The use of ice-covered lakes for temporary airstrips would diminish.
Mining
Activity in this sector will be enhanced, with lower costs resulting from reduced permafrost, fewer operations problems due to cold, fewer inducements for personnel, and lower shipping costs. Some marginal or sub-marginal mines would become more viable.
Construction
As with land transportation, the construction industry will eventually benefit from the general shift in the permafrost, but in the short term, active layer changes will cause problems. This will be true for pipelines, buildings, foundations, and sewage systems, as well as for roads and airstrips. Meanwhile, the costs of heating, insulating, and water supplies will decrease. For marine construction, such as ports and related facilities, reduced sea ice will lead to savings in design, building, and maintenance.
Agriculture
A viable agricultural industry could become a reality in valleys of the Mackenzie District and Yukon as growing degree-days increase by 30 to 40 per cent and seasonal lengths by about 50 days. As a result, growing conditions for Yellowknife and Whitehorse would approach those now characteristic of Edmonton.
Human Habitation
With less harsh climatic conditions and more productive land and water systems, the Arctic will become a more habitable region in many respects. An increased Inuit population will be favoured and expansion northward among the islands will be likely. The proportion of permanent to transient residents in the North will also increase.
Sovereignty
The increased accessibility of the Arctic will make the region more susceptible to foreign intrusion. This will increase pressure on Canada to demonstrate visible sovereignty over the entire area. The Northwest Passage, already of interest to several nations for scientific, military, and commercial purposes, would become even more attractive and, presumably, create a need for adequate docking facilities; port, vessel, and environmental security; navigational aids; and environmental capabilities. This would necessitate an increased Canadian presence and control, perhaps even a Canadian Forces base in the arctic islands to protect vital resources and routes.
Summary
The issue of climatic change is a difficult one; at present, much is anticipated, but little can be predicted with a high level of confidence. There is not even conclusive evidence for the beginning of a long-term warming trend as yet. Past history has shown how important climatic change and its impacts can be, but, as with most fields, we seem to remember few of the difficult lessons already learned.
We should not allow the general belief that future climatic change is likely to warm up the Arctic delude us into thinking that everything will suddenly be easier to deal with in that region. As has been indicated, there are advantages and disadvantages to be weighed, depending upon what activity is being considered.
Nor should we allow the limitations which currently exist in our methods of estimating the impacts of climatic change to in any way detract from the importance of incorporating such information in policy making, project planning, and engineering design. Activities known to have long-term future consequences must be based on consideration of climatic change and its impacts during the pertinent time periods. Engineering or project design procedures associated with, for example, production structures or transportation facilities having expected 30- to 40-year life expectancies should include climatic factors, as should long-term decisions on wildlife management.
In light of current evidence, failure to include proper climatic change impact assessment for those projects in which climate is a significant factor (and that is virtually every activity in the Arctic) constitutes a serious omission on the part of planners and engineers. The risks of underdesign, with its potential consequences for environmental damage and loss of life, as well as the cost ineffectiveness of overdesign. are too significant to ignore.
Barrie Maxwell is Superintendent, Arctic Meteorology, with the Atmospheric
Environment Service of Environment Canada.