TL: Climate Change and the Arctic: An Overview
SO: Greenpeace USA, (GP)
DT: July 1997

Introduction

The Arctic is home to some of the world's most distinctive mammals,
millions of migratory and resident birds, a rich ice-edge community, and
some of the world's major fisheries. It is a biologically and culturally
unique environment, and one of the last places on Earth where natural
conditions still prevail over much of the region.

Unlike the ice-bound Antarctic, the Arctic has been home to humans for more
than 10,000 years. Today, the region is culturally, politically,
demographically and economically diverse, with settlements ranging from
small indigenous communities to modern industrial cities. Indigenous
cultures include: Aleuts, who live primarily in coastal southwest Alaska;
Inuit, who live on the coast and inland from northwestern Alaska east to
Greenland; Athabascans, who live mainly inland in eastern Alaska, the
central Yukon, and the Northwest Territories of Canada; the Saami of
northern Fennoscandinavia and Native groups in northern Russia.

The Arctic is also a region particularly vulnerable to human-induced
climate change. What happens to the Arctic in response to human-induced
climate change concerns us all. The area and its people serve as indicators
for what may occur in other regions, and to the planet as a whole.

This background paper gives an overview of the Arctic environment and its
importance to the globe as a whole. It discusses the dramatic changes in
climate and related systems that have occurred at high northern latitudes
over recent decades, and further examines the implications of future
climate change.

Global Influences of Human Activity

Human modification of the natural environment is an ancient phenomenon. It
has been estimated that around 75 percent of the habitable land on the
planet has been disturbed to some degree. 1This disturbance has been
accompanied by increasing human population levels, sustained, in turn, by
increasing industrial activity and more intensive agriculture. Some of the
impacts associated with these activities have been appreciated for
centuries. For example, pollution due to the extraction of metals has been
recorded since the time of the ancient Greeks. 2 Today, human activity is
the most important determining factor in the global release of potentially
polluting metals. In short, humans have significantly altered the planetary
biological and geological cycles, or biogeochemical cycles, of these
chemicals.

The Industrial Revolution, the start of major industrial activity, marked
the point of the rapid and serious alteration to a number of biogeochemical
cycles. These include the chlorine, sulphur, nitrogen and carbon cycles.
Some of these biogeochemical cycles are being influenced by deforestation
and agricultural practices. The wide-scale burning of fossil fuels to
provide energy has also directly influenced the natural carbon and sulphur
cycles. In turn, some of the energy produced has been used to convert
nitrogen and chlorine to other chemical forms, thus influencing the global
cycle of these elements. 3,4

Greenhouse Gases

Carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) concentrations
have risen steadily in the atmosphere since the beginning of the Industrial
Revolution. Ice core records show that from the end of the last ice age
10,000 years ago, the concentration of carbon dioxide in the atmosphere was
relatively constant until the beginning of the 18th century. Pre-industrial
concentrations have risen by around 30 percent [from around 280ppm (parts
per million volume) to 358ppm by 1994]. 3 Methane, another component of the
carbon cycle, also rose in atmospheric concentration by some 145 percent
[from around 700ppb (parts per billion volume) to 1720ppb] over the same
period while nitrous oxide has increased by around 15 percent (from around
275ppb to 312ppb). In addition, from the 1940s onward, industrially
produced chemicals such as chlorofluorocarbons (CFCs), have been
progressively released into the atmosphere.

What these gases all have in common is that they act as "greenhouse" gases.
The atmosphere is relatively transparent to most of the incoming solar
radiation which heats the surface of the earth. By contrast, energy emitted
from the Earth is absorbed by water vapour and other "greenhouse" gas
molecules and retained within the atmosphere. Water vapour is the largest
contributor to the effect, but the contributions of the other gases,
particularly that of carbon dioxide, are also important. Although gases
such as methane and nitrous oxide are present in the atmosphere at lower
concentrations than carbon dioxide, molecule for molecule these gases are
more effective at trapping heat emitted from the Earth.

Atmospheric carbon dioxide levels will increase unless emissions from the
burning of fossil fuels are brought under control. Studies suggest that in
pre-industrial times the atmosphere contained 590 billion tonnes of carbon
as carbon dioxide. Between 1765 and 1991 this rose to 755 billion tonnes. 5

Scientists from the Intergovernmental Panel on Climate Change
(Intergovernmental Panel (IPCC) estimate that current emissions are around
7.1 billion tonnes of carbon annually. Around half of this is absorbed into
the terrestrial and oceanic sinks of carbon dioxide and the balance remains
in the atmosphere. This buildup results in broadly agrees with the
currently estimated rates of carbon dioxide concentration increase of
around 0.4 percent per year. 3

The potential for industrialization and the burning of fossil fuels to
increase atmospheric concentrations has been appreciated since at least the
turn of the century following the work of Savant Arrhenius in 1895. 6 With
an outlook typical of the cultural optimism at this time, Arrhenius
suggested generally beneficial effects. This view has been considerably
modified in modern times by concerns about possible large scale negative
consequences. 7

The relative radiative effect of different greenhouse gases has
been estimated by the IPCC and called their Global Warming Potential (GWP).
As the reference molecule, carbon dioxide has a GWP of one. For a time
horizon of 100 years, methane has a GWP of 21 and nitrous oxide of 310. The
typical range of uncertainty for GWPs is +/- 35 percent. 3

Temperature Rise and Climatic Change

Mathematical models predict that as levels of greenhouse gases increase in
the atmosphere, a greater proportion of the heat radiated from the earth
will be retained in the lower atmosphere, resulting in an average warming
of the Earth's surface. Computer models can be used to predict the scale of
the temperature rise and other changes in climate. Drawing from climate
models developed by the world's major climate centres. Using these, the
Intergovernmental Panel on Climate Change has estimated that relative to
1990 the Earth's surface will warm by 1 to 3.5 degree C by 2100. 8 It is
estimated that air temperatures have increased by between 0.3 and 0.6
degree C since the late 19th century and by 0.2 to 0.3 degree CC over the
last forty years. 9In historical terms the increases in surface air
temperature projected by the IPCC are extremely large. They will be greater
in all probability than any following the emergence of the Earth from the
last ice -age 10,000 years ago.

Since climatic processes are largely driven by temperature changes and
differences, any increase in temperature of the scale estimated will be
associated with major climatic changes around the world. Although there are
still many uncertainties in estimates of global climate change, it is
likely that the magnitude of global temperature change will fall within the
range estimated by the IPCC. Prediction of precise and regionally specific
changes in climate remains unclear at this stage. Limitations exist in the
models due to our poor understanding of total global and regional processes
and consequent failure to consider all the possible influencing factors.
The potential controlling feedback mechanisms are also only poorly
understood. The natural variability of the climate system also masks many
trends and this can only be compensated for by considering data obtained
over a very long time period. 10 Nonetheless, the IPCC considers that
"climate has changed over the past century" and that "the balance of
evidence suggests a discernible human influence on global climate." 11 More
recent refinement of the mathematical models and other scientific
techniques used to detect and attribute climate change has provided further
strong evidence that the observed trend in global temperature over the last
century is unlikely to be solely of natural origin. 12, 13 Undoubtedly, as
temperatures continue to rise the impacts will become increasingly obvious
as trends become more clearly defined and more easily identified.

A consistent feature of climate models is that they project intensified
warming in the northern polar regions. Hence the Arctic could well act as
an area where the first effects of global change will be unequivocally
identified. 14, 15, 16, 17 In addition, the Arctic environment has a
significant role in establishing global circulation patterns, which in turn
influence both weather, and climate.

The Arctic

A Harsh Terrestrial Environment

The Arctic Region is broadly defined as the region to the north of the
limit of tree growth in the circumpolar boreal forests (or taiga). The
limit may also be defined in terms of temperature, as the region north of
the 10 degree C July isotherm[dagger], which tends to move the boundary to
the north by as much as 200 kilometres. The area is divided into the low
Arctic region which corresponds to the tundra and the high Arctic region
which corresponds to the polar desert. This classification is based upon
the plant communities which predominate. These major regions are in turn
subdivided; some differences exist between North .A line on a map
of the Earth's surface connecting points having the same temperature at a
given time or the same average temperature for a given period America and
Eurasia, particularly in the transition between the high and low zones. In
practice the divisions show a gradual gradation rather than a defined
border.

In general, low shrub tundra occurs just north of the tree line while
tussock tundra and sedge-moss tundras (mires) have become established
according to how well the land is drained. Poor decomposition of plant
materials in waterlogged areas leads to the formation of peat. The low
Arctic gives way to polar semi-desert and polar desert environments where
lichens and mosses predominate.14, 15, 16, 17, 18 Extensive snow and ice
cover exists in winter. There are also large areas of permanent ice and
snow cover. Large areas of land remain frozen for two or more consecutive
summers and this is known as permafrost. Only a relatively thin surface
layer of this thaws in summer. The permafrost restricts drainage so that
extensive areas become waterlogged. Some 1.5 million square kilometres
above 60oN can be classed as wetlands. Bogs and fens are the most common
form of wetland.

Tundra ponds are generally small and highly acidic but support life in the
bottom sediments. In lakes, the ecology is also driven by ice-cover and the
timing of the spring melt. Those which are not too nutrient poor support a
sparse flora of algae which serves as food for a limited population of
small animals. Where nutrients are less limiting, a sufficiently high
production in the waters and sediments can support fish. The most widely
occurring fish species in inland Arctic waters is the Arctic char. 15,16

The Arctic environment is characterised by its coldness and by extremely
short growing seasons (1 to 2.5 months) as compared to temperate regions.
There is extreme variation in light and temperature. Summer periods are
short. The sun never rises very high in the sky and this limits the amount
of incoming solar energy despite the long summer days when solar radiation
is higher than anywhere else on earth. Up to 90 percent of this incoming
energy is directed back away from the Earth by the reflective snow and ice
surfaces. In addition the Arctic loses heat into space as infrared
radiation. This heat loss is compensated for by heat exchange in the
atmosphere and in ocean currents. These currents carry relatively warm air
and water northwards while cold air and water are moved southwards.

As a result, the prevailing climate and weather patterns in coastal areas
influenced by waters from the Pacific and Atlantic are generally more
temperate than continental areas. Indeed, the various combined effects of
geology, ice and climate leads to considerable diversity of terrestrial
habitat. 16

In the Arctic, low temperatures slow biological processes, snow and ice
limit the light available to plants and liquid water only becomes available
after the snow and ice have melted. Both plants and animals show extensive
adaptations to these extreme conditions.16 Many bird species found in the
Arctic are migratory, taking advantage of abundant summer food supplies and
leaving in winter. Other organisms are adapted to survive the year round by
laying down reserves of energy in the form of fat. Terrestrial food chains
are generally short.

A Fertile Marine Environment

Marine systems in the Arctic are characterised by very complex food webs
but with only a very few key species directly connecting the various
levels. 15,16 The central basins of the Arctic Ocean itself are considered
to be one of the least productive major water bodies on the planet but
recent work has suggested that they support a significant food web. 19 Even
the pack ice has high productivity with small plants living within and on
the ice. By contrast, intense production takes place elsewhere in Arctic
waters. The biologically richest areas occur at the edge of the ice and in
the continental shelf seas. Some of these shelf areas are among the most
productive ecosystems in the world.

Perennial pack ice covers about 8 to 9 million square kilometres of the
Arctic Sea, growing to a maximum of 15 to 16 million square kilometres in
the period from November to February. Areas of open water (polynyas) in the
ice field may be temporary or persistent and recurring. 20 Persistent
openings in the ice also act as a focus for intense marine production by
allowing earlier penetration of light and facilitating mixing of nutrient
poor with nutrient rich water. 21 The polynya can also be highly important
to bird populations 22 and to wintering mammal populations. 15, 23 Even in
the central Arctic these ice areas can comprise 1 to 2 percent of the total
area. Expanding in summer, they play a significant role in heat exchange
between atmosphere and water which influence local and to a lesser extent
regional weather patterns. 21 The seasonal accumulation and melting of
sea-ice results in high productivity at the edge of the ice and in the
shelf seas and also contributes to the formation of a salt driven layering
of the water. This keeps plants close to the sunlit surface. The ice-edge
bloom of microscopic plants and bacteria supports a complex food web 24
which follows the retreating ice edge. In some areas, freshwater inflow
from north flowing rivers creates highly productive estuarine zones. In the
Barents Sea, cooling and ice formation result in a complete turnover of the
water column, and in other northern sea areas surface water is enriched
annually with nutrients from deeper waters.

The marine boundary of the Arctic is formed when the water of the Arctic
Ocean, cooled and diluted by melting ice, meets the warmer saltier water of
the southern oceans. The position of this Polar Front is relatively stable
from year to year. 15, 16 To the south of this front nutrients can be
brought to the surface by summer storms, while at the front itself,
considerable vertical mixing can take place throughout the year. Despite
the short growing season, the supply of nutrients forms the basis of a rich
fauna supporting highly profitable fisheries.

The species richness and high productivity of marine ecosystems is in stark
contrast to the tundra and mountain heath environments. It is explained by
the relatively benign, although still harsh, conditions in the sea. The
Arctic has long held an attraction for ecologists 14 seeking to understand
the highly visible adaptations to these extreme environments. Moreover,
after Antarctica, the Arctic areas have been disturbed much less than most
other areas of the planet, with large areas still regarded as pristine. 1
However, human impacts from external sources are increasing. Recent
important areas of study include: the apparent northwards migration of
pesticides and industrial pollutants; contamination of the environment with
toxic metals as a result of mining and smelting; and air pollution giving
rise to an "Arctic Haze, " a form of smog and acid precipitation. 15, 16

The Arctic and Global Ocean Circulation

The highly simplified representation of the Arctic environment above hardly
does justice to the sheer complexity and diversity of Arctic systems. The
significance of the physical and chemical processes taking place in the
Arctic extends far outside the region. This polar area has been described
as a "refrigerator in the equator to pole transport of energy. " 16
Mid-latitude low and high pressure weather systems are the results of the
heat exchanges between the warm and cold water and air masses. This results
in semi-permanent low pressure systems centred around the Aleutian Islands
and Iceland which bring moist air northwards in the winter. In the
Atlantic, the Iceland low pressure system is coupled with a high pressure
system centred near the Azores. 25 As well as being an area where nutrients
are recycled and released into the water, the Polar Front region in the
North Atlantic plays a fundamental role in the driving of ocean currents.
At the Polar Front near Greenland, Iceland and the Labrador Sea, warm,
salty water from the North Atlantic is cooled by Arctic waters and by
intense heat loss to the atmosphere. These waters become more dense and
then sink to the deeper layers of the ocean. Salt rejected as sea-ice forms
also increases the density and contributes to the process. Although a slow
process, this sinking takes place over a wide area and each winter several
million cubic kilometres of water sink and begin moving slowly south along
the bottom of the Atlantic Ocean towards Antarctica. This process is known
as thermohaline circulation because it is driven in part by temperature and
partly by salinity differences.

The dense, cooled water becomes part of what is termed the Ocean Conveyor
and the water eventually returns to the surface in the Indian and Pacific
Oceans. As warm water returns to the Atlantic, the current moves polewards
as the Gulf Stream and North Atlantic Drift. 15,16,26 In reality, the
processes taking place in the Arctic are extremely complex. 27, 28 Global
circulation of the water in the ocean currents takes place over time scales
of centuries. In addition, the formation of deep-water also takes carbon
dioxide dissolved from the atmosphere into the deep ocean. The Arctic
region, therefore, plays a fundamental role in ocean circulation patterns,
which in turn determine climate patterns over the rest of the globe.

The Arctic and Climate Change

The significance of climate change with respect to the Arctic region is
twofold. On the one hand, climatic change can be expected to change Arctic
systems. On the other, these changes themselves may well induce other
changes of global significance. Modelling studies have suggested that the
Arctic will warm by more than the global average. 8, 15, 16 Thus far,
scientists have been unable to differentiate human impacts from natural
variation. In addition, temperature increases are unlikely to be uniform
over the whole area. Models have given results which in some cases are not
easily interpreted partly because the likely impact of some factors, such
as cloud cover, are poorly simulated.

Observations show that surface air temperatures have increased by about 1.5
degree C per decade over central Siberia and continental North America, and
have fallen by a similar amount in the Baffin Bay area. Over the last
century, indications of warming have been seen around the northern
continental rims of central and western North America and Central Asia.
There is a cooling trend for eastern North America to the North Atlantic. 9
Most of the warming in the western Arctic appears to have occurred in
winter and spring, with less warming observed in the summer and autumn.

Satellite monitoring has shown that the lower atmosphere of the Arctic has
become around 0.05oC warmer per decade. This is a more pronounced change
than the global average. The associated cooling in the upper atmosphere has
been determined at -1.01 degree C per decade, with the most rapid decreases
over Russia. This change is the most pronounced over the whole planet.
Borehole studies of permafrost in Alaska have also shown a temperature rise
of between 2 to 4 degrees C over the last hundred years.16

In Alaska, a warming trend of 0.75-degree C per decade has been identified
for the last three decades over land bordering the Bering Sea. Over the
eastern Bering Sea, temperatures have risen by 0.25 degree C per decade. 29
From these trends and modelling results, suggest a further rise of 1 to 2
degree C over 20 years and 4 to 5 degree C over 100 years can be expected.
West of latitude 141, precipitation has increased by 30 percent between
1968 and 1990. 30 Elsewhere precipitation in high latitudes has increased
by 15 percent over the last forty years. 16 On the North American tundra
there is a tendency toward earlier snowmelt. The area of land with
continuous snow cover over the winter to the south of the sub-Arctic has
retreated by about ten percent during the past 20 years. 16 In the
Mackenzie River Basin Study, an area that includes parts of the Yukon and
Northwest Territories as well as northern British Columbia, Alberta and
Saskatchewan, temperatures have increased by 1.5 degree C this century. 31

Regional differences in temperature trends are predicted by climate models.
For example, models applied to the Nordic Arctic area have predicted a rate
of temperature rise of 0.3 degree C per decade for Iceland and the Faeroe
Islands, and 0.45 degree C per decade for eastern Finland and the northern
extremes of Sweden. Summer warming is predicted to range between 0.25 to
0.3 degree C whereas in some areas winter warming is likely to range
between 0.35C to 0.6 degree C per decade. Precipitation is likely to
increase by between 3 to 6 percent per degree of warming.32

Observed trends, therefore, are broadly consistent with the results of
modeling exercises. The full impacts of climate change on the Arctic,
however, are extremely difficult to assess because of the intricate
interactions between physical and biological factors. Overall, the
hydrological cycle of the Arctic links atmospheric moisture transport,
precipitation, river runoff, sea-ice and ocean circulation in a single
system 33 and this in turn helps drive global ocean circulation. Hence, in
considering potential impacts of climate change in the Arctic it is
important to also consider how these changes may themselves cause wider
impacts and indeed how they may actually reinforce the warming trend. It is
redicted that practically all snow and ice features of the Arctic will be
affected by continued warming of the Earth's atmosphere. 33, 34 The
freeze-thaw line is likely to be shifted significantly northwards, and this
will be accompanied by dramatic impacts.

Temperature Change and Impacts on Arctic Terrestrial Ecosystems

Vegetation is the terrestrial environment's life-sustaining feature. Rapid
temperature increases in the Arctic are expected to push climate and
vegetation zones northward at rates faster than many plant and animal
species will be able to adapt. 15

Such dramatic shifts in vegetation could jeopardize many animal
populations, since abundant vegetation, at the right time, is critically
important to all terrestrial wildlife. Grazing animals such as reindeer,
caribou and muskoxen closely track seasonal vegetation growth, and depend
upon the vegetation for healthy herds and well-nourished calves. This
"plant-herbivore" interaction is an important part of tundra life. Without
adequate vegetation, the animals become less productive, delay having
offspring, and, in many cases, starve.

In the Arctic National Wildlife Refuge, for example, spring has arrived
earlier and earlier along the coast. Consequently, caribou have had
difficulty migrating from wintering areas in time to take advantage of
periods of maximum springtime plant growth. The spring of 1990 was the
earliest in nearly 40 years, and by the time the animals reached the plain,
their principal food plant had gone to seed. Caribou herd populations could
decline significantly should future climate and vegetation patterns prevent
proper nourishment of calves. 35 High Arctic Peary Caribou and muskoxen may
even be faced with extinction.36

Climate change could also affect regular freeze-thaw cycles, which have
important implications for reindeer populations in relation to their
ability to find food. For example, in the 1996-97 winter an estimated
10,000 reindeer died of starvation on Russia's far northeast Chukotsk
Peninsula, after inclement weather patterns formed a thick ice crust over
pastures, making it impossible for reindeer to graze. While reindeer
populations often suffer from these freeze-thaw cycles, future variations
in weather and climate could intensify their effects. 15 Increased late
winter rain could cause polar bear dens to collapse before females and cubs
have departed. Scientist surveying polar bear habitat near Manitoba, Canada
have observed large snow banks used for denning that had collapsed under
the weight of wet snow. 37>

Sea-ice and Snow Cover

There is some evidence that between 1978 and 1987 sea-ice extent in the
Arctic decreased by around 2.1 percent together with a decrease of open
water of 3.5 percent. 38 Data collected by submarine found that the
thickness of ice covering 300,000 square kilometres of sea had fallen,
decreasing in volume by some 15 percent. 39 It is unclear whether this
actually represented an overall trend or normal variation, 40 highlighting
the need for additional data. Further work since has indicated that between
1978 to 1994 the extent of Arctic sea-ice diminished by around 4.6 percent
while the sea-ice area contracted by almost 6 percent. 41 In the Bering
Sea, sea-ice extent has been reduced by about five percent over the last
forty years with the steepest decline taking place during the 1970s.29
Using sophisticated statistical analytical techniques, it has been shown
that the mean sea-ice extent in summer over most sectors of the Arctic has
fallen substantially, when the period 1961 to 1975 is compared 1976 to
1990. 42 The study detected no trend in winter.

While these changes in themselves are not unequivocal indicators of a
trend, they again concur generally with the predictions from modeling
exercises. 43 Nonetheless, under doubling of atmospheric carbon dioxide
concentrations, a reduction in sea-ice area of between 10 to 50 percent has
been predicted by one model, together with a reduction in thickness,
particularly in summer. When ice volumes are considered, a 50 percent
decrease on average in winter could be followed by a virtual disappearance
of sea-ice in the summer.

Normal variability in snow cover coupled with likely regional differences
in the rate of temperature increase mean that any such trends are likely to
be difficult to identify. Even so, directly measured snow cover over the
North American Great Plains suggests that there has been an increase over
the last century, whereas in the Canadian prairies, snow cover has
declined.34 In Alaska, there is evidence that springtime disappearance of
snow cover occurred some two weeks earlier in the 1980s than in the 1940s
and 1950s.17 Data from lakes in central Canada show a warming of several
degrees Celsius and lengthening of the ice free season by several weeks
over a twenty year period beginning in the late 1960s. The modeled
predictions 34 suggest that winter snowlines in the Arctic could move
northwards by 5 to 10? of latitude. Snowfall will tend to begin later and
snowmelt will be start earlier. This will extend the snow free season,
although in some regions, more frequent open water may actually lead to
more snowfall downwind due to increased evaporation from the water surface.

Effects on Ecosystems

Higher temperatures and longer growing seasons could increase the growth
and production of some Arctic Ocean phytoplankton. Some species are more
sensitive to temperature than others and this is likely to lead to changes
in the composition of the phytoplankton community. Changes in the
composition of the ecosystem are also likely to result from the invasion of
Arctic waters by temperate species.

Reductions in sea-ice extent and algae could, in turn, lead to profound
reductions in overall biological productivity in the Arctic seas. The
entire ice-associated community could be threatened, including dependent
fish species, such as polar cod. Arctic and migratory whale species, such
as the narwhal and beluga whales, and gray and bowhead whales, would be
affected, since they feed along the ice edge. Birds and mammals may be
affected by climate-induced changes in ice openings, which serve as
critical "outposts" for feeding, breeding and migration. 44

Animals that depend on the ice as a platform, such as ringed seals,
walruses and polar bears, would be left vulnerable by the loss of their
habitat. 44 Walrus may suffer first, since they are dependent over much of
their range on seasonal sea-ice. Polar bears could also become extinct if
the Arctic ocean is free of summer ice for long periods, or if seasonal
sea-ice changes affect ringed seals, their main prey.

If further warming occurs, ice is likely to break up earlier and freeze
later, extending the open-water season in summer and fall. This change
would reduce the amount of time polar bears can use sea-ice for hunting.
This hunting time is especially important for female bears, who often fast
for up to eight months to den and raise their cubs. If ice break-up occurs
even two or three weeks earlier, fewer adult female bears would be able to
hunt and store enough body fat to produce and successfully wean cubs. Lower
reproduction rates among the bears would quickly reflect the females' lost
hunting time. 37

In addition to providing shelter, snow also supports life on land. The
health of many plant and animal communities largely depends on the
persistence, thickness and timing of snow cover. If Arctic snowfall
declines, animals that build winter dens out of snow may suffer. Increased
snowfall, on the other hand, is likely to alter vegetation cover and affect
animal survival and reproductive success. 45 A significant increase or
decrease in snowfall would upset the present delicate balance of the Arctic
environment.

Effects on the Transfer of Heat

The reduction of snow cover and sea-ice will affect one of the most
important feedback systems in the Arctic Environment. By reducing the
reflection of solar energy from the surface of the Earth and sea, more
energy can be absorbed by the ground surface. In turn this leads to an
increased flow of heat from the surface to the atmosphere. The resulting
temperature rise may bring about further loss of snow and ice, completing a
positive feedback loop and reinforcing the original effect. One possible
offset against this is the evaporation of water from the surface leading to
increased cloud cover, but at the present the relative importance of the
two processes is impossible to assess. 33

The sea-ice also controls the transfer of heat from the relatively warm
ocean to the cold atmosphere. Hence, ice reduction either in area or
thickness could lead to increased heat transfer and interaction with winds.
16 This would allow the air to pick up moisture and make the Arctic
cloudier. This in turn would change regional weather patterns. The role of
clouds, however, continues to be one of the major uncertainties in climate
models.

Effects Upon Ocean Currents

In one scenario, barometric pressure could be reduced in the Arctic.16 This
could give rise to more cyclonic storm systems particularly in winter.
Changes in wind patterns could influence temperature and humidity, and
hence the formation of sea-ice and the circulation of water in ocean
currents. A specific concern is the likely behaviour of the thermohaline
circulation. Increased precipitation and melting of ice could make the
upper layers of the Arctic less saline. This could change the formation of
deep water at the polar front. 46

A change in the thermohaline circulation, therefore, could shut down the
Ocean Conveyor. Alternatively, based on evidence from sediment cores, the
site where deep water forms could shift southwards. This would end the
influence of warm waters from the Gulf Stream and North Atlantic Drift
along the coast of the Western Atlantic. Paradoxically, this could lead to
areas of Europe and Scandinavia cooling by up to 5 degree C. Thereafter,
these regions would experience the global temperature rise, but starting
from a point where the warming effects of Atlantic waters were absent. This
possibility is supported by geological evidence of previous phenomena
following large inputs of low salinity water into the Arctic seas. 15, 47

In addition to the profound effects that a temperature drop would have upon
regional climate and weather in Europe and Scandinavia, changes to the
transport of atmospheric carbon dioxide from the atmosphere into the oceans
could also be expected. If atmospheric levels of carbon dioxide were
increased by this a ositive reinforcement of additional increases in global
temperatures could occur.

Terrestrial Ice

a) Glaciers and Ice Sheets

Despite showing some regional variation, studies indicate that the majority
of Arctic glaciers are in retreat.34 With continued warming this loss of
glacial mass is expected to continue. The Bering Glacier, North America's
largest glacier, is an example of a major glacier in retreat. Originating
some 25 kilometres east of the US border in Canada, the Bering Glacier
flows 191 kilometres to its terminus in south central Alaska. The areal
extent of the glacier is over 5,170 square kilometres and in some places
the glacier is over 800 metres thick. During the last 10,000 years the size
of the glacier has varied in response to climatic changes. 48>

Since the beginning of this century the glacier's frontal region has
declined 130 square kilometres in area. In addition to the overall retreat
of the glacial front the Bering Glacier has thinned dramatically over the
past century. Aerial photography shows that parts of the glacier have
thinned by as much as 180 metres in the last 50 years and in some places
the glacier has lost between 20 to 25 percent of its thickness. 48

In general, Alaskan glaciers have suffered ice thickness decreases of 10m
over the last 40 years. A retreat of 15 percent appears, on average, to
follow from each 1 degree C rise in temperature. 29 It is predicted that
the largest Gulf of Alaska glaciers should persist into the 22nd century.

The significance of melting glaciers is global. Over the period 1890 to
1990, it is estimated that the mid-range contribution of global glacial
retreat to recent sea level rise was 3.5 centimetres. 49 Total sea level
rise over this period was around 18 centimetres (within a 10 to 25
centimetres range). The 3.5 centimetre contribution of glaciers is
therefore significant. In the future, global sea level is expected to rise
by between 13 to 94 centimetres. With mid-range estimates of 16 centimetres
and 28 centimetres respectively, most of this projected rise is attributed
to thermal expansion of waters and increased melting of glaciers and ice
caps. 49

However, increased precipitation could cause some glaciers to increase in
size, or remain stable, particularly at high latitudes and altitudes, at
least in the short term. The response will also partly depend upon weather
patterns. It is known that high Arctic glaciers also melt quickly following
certain shifts in the semi-permanent weather systems which become
established in the Arctic region. 34 Meltwater could also contribute to
changes in the Ocean Conveyor system, by decreasing the salinity of Arctic
seawater.

Glaciers show a delayed response to climate change of years to decades. In
the case of a very large mass of ice such as the Greenland Ice Sheet, this
lag phase will be longer. Already, parts of the margin of the Greenland Ice
Sheet appear to have retreated significantly over the past century, despite
a short-lived "thickening" of the ice during the 1970s and early 1980s. 34
The ice sheet does not at present seem to be shrinking but it is predicted
that both melting rate round the edges and accumulation rates through
increased precipitation in the interior should increase. It is predicted
that melting will predominate 28, 37. Estimates made of the likely
contribution of the Greenland Ice Sheet to sea level rise range from
between 1 to 4 centimetres by the year 2100 but could under some scenarios
reach over 1 metre by the year 2200. 50 If the Gulf Stream slows, then it
is possible that Greenland would remain stable or even cool. Eventually it
would be subject to the same temperature rises as the rest of the Arctic,
melting being simply delayed.

b) Permafrost

Permafrost currently underlies around 25 percent of the land area of the
Northern Hemisphere 51 and much is close to melting point and hence
sensitive to small changes of temperature. It is predicted by computer
modeling that permafrost zones will move northwards by between 500 and
1,200 kilometres. A significant proportion of the permafrost in the Arctic
is close to 0 degree C and therefore particularly sensitive to increasing
temperatures.16 A 16 percentshrinkage in total permafrost area is projected
by the year 2050.34 It is possible that total shrinkage could be as high as
25 to 44 percent with the continuous permafrost cover reducing in area from
29 to 67 percent according to other models.52 The regional rate of thawing
is likely to be variable and as the thaw penetrates deeper into the
permafrost, lag times will increase. In Northern Alaska, permafrost has
warmed by between 2 to 4 degrees C over the last century and some
discontinuous permafrost in Southern Alaska is thawing. Permafrost in
Russia and China has also warmed over the last two decades. 34

Permafrost melting will undoubtedly be an important consequence of climate
change. Changes in the depth of the layer which thaws in the summer will
modify biological and geological processes, but in the tundra the overall
effect on the permafrost structure could otherwise be relatively slight.
Thawing will be associated with considerable disturbance and change in
areas like Alaska, Canada and Siberia where discontinuous ice-rich
permafrost underlies much of the land area. Where the permafrost is rich in
ice, land will be susceptible to subsidence. Further south, there would be
a shift to discontinuous permafrost with degradation of ground ice and much
more severe effects.

Such changes will allow increased erosion and damage to surface vegetation.
Exposed dark soil surfaces are more efficient at absorbing solar heat than
vegetation, so disturbed ground could reinforce the thawing of the
permafrost. The thawing of large amounts of underground ice can
substantially modify the landscape by causing ground subsidence and the
forming of pits, troughs and mounds. This type of terrain is called
thermokarst. In lowland areas thermokarst will lead to the formation of
many lakes which will continue to be enlarged by erosion over a long period
of time. Thermokarst will increase both coastal retreat and inland erosion.
The depressions formed by this subsidence may be several metres deep 29 as
has been recorded in both Alaska and Russia. Permafrost melting in the
Mackenzie River Basin has led to widespread river-bluff landslides and
increased erosion. In Alaska, extensive coastal retreat has been observed
29 following the thawing of permafrost.

As permafrost thaws, infrastructure such as pipelines, housing, air strips,
roads, and water and sewage systems will be damaged. The redesign and
replacement of many of these systems will be required.

Impacts of thawing permafrost are likely to extend beyond simple physical
disturbance. Thermokarsts could act as a focus for colonising immigrant
species replacing the specialised Arctic flora. By the year 2020,
vegetation zones under a 2 degree C temperature rise could have moved up to
500 kilometres northwards. 16 Other estimates suggest that the advance of
vegetation and climate zones northwards could be equivalent to 1 metre an
hour, over 8 kilometres per year. 15 Many Arctic plants are unlikely to be
able to adapt to such changes or to adjust their ranges to keep pace.

There are possible mechanisms of positive reinforcement of climatic warming
could come into play as a result of the thawing of permafrost. The thawing
of permafrost will allow drying of some upper soil areas and decomposition
of organic matter. This in turn will release carbon dioxide and possibly
methane into the atmosphere, increasing the concentrations of greenhouse
gases. This effect could be substantial if more than a fraction of the 450
million tonnes of carbon in soils of all tundra systems or of the 50
million tonnes in Arctic soils is released as carbon dioxide or as methane.
34

Conclusions

The global build up of greenhouse gases and associated climate change has
the potential to dramaticall alter the Arctic environment and its
ecosystems The Arctic is particularly vulnerable to climate change, and
indeed in some areas the impacts of changes in climate are already evident.
Future climate change is likely to threaten both marine and terrestrial
wildlife. From plankton to polar bears, many species could suffer or
disappear entirely. While the implications of warming on the Arctic are
complex and not yet fully understood, they extend well beyond these
immediate areas and may have dramatic global repercussions, including
increases in sea level due changes in the mass balance of Arctic glaciers
and, possibly the Greenland Ice Sheet. Local warming may, in fact,
accelerate global warming and its effects.

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