Permafrost in Canada and climate change

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Permafrost in Canada and climate change
Source NRC
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Source Hinzman et al. (2005)
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Time to form deep permafrost
Time (yr) Permafrost depth
1 4.44 m
350 79.9 m
3,500 219.3 m
35,000 461.4 m
100,000 567.8 m
225,000 626.5 m
775,000 687.7 m
Source Wikipedia
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Snow permafrost warming
Source Stieglitz et al. (2003)
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Source Hinzman et al. (2005)
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Permafrost and climate change

• During the past few thousand years, Earth's
  climate has been subject of fairly small changes
  and world temperatures have fluctuated only
  within a couple of degrees.
• However, higher levels of carbon dioxide and
  other greenhouse gases in the atmosphere may
  progressively increase global temperature by as
  much as 2 to 4oC over the next century.

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• In addition to temperature changes, the patterns
  of precipitation would undoubtedly change -
  annual totals would likely increase over the
  arctic mainland, although current regional
  projections are again quite variable between
  models.
• Increase of 10 to 50 in summer and as much as
  60 in winter may be anticipated for parts of the
  Canadian Arctic.
• Such large and rapid climatic changes would have
  serious and far-reaching environmental and
  socio-economic effects in permafrost regions and
  for the arctic environment as a whole.

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• Some might look on the transition to a warmer
  Arctic with happy anticipation in the long term,
  it would undoubtedly result in greatly reduced
  costs of living and operating there.
• New resources could become available, and mining
  and agriculture, for example, might expand
  however the terrestrial environment of the north,
  in which permafrost plays a major role, would be
  profoundly disrupted during the transition.

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• Permafrost degradation may lead to another,
  potentially disastrous, positive feedback on
  climate.
• Degrading permafrost may allow the release of
  greenhouse gases such as CO2 and CH4 that are
  currently trapped in frozen ground (especially in
  peat bogs).

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• Let us imagine some change in climatic conditions
  which causes the mean annual surface temperature
  to fall below 0oC, so that the depth of winter
  freezing will exceed the depth of summer thaw.
• A layer of permafrost would grow downward from
  the base of the seasonal frost, thickening
  progressively with each succeeding winter.

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• Was it not for the effect of heat escaping from
  Earth's interior (the geothermal heat flux), the
  permafrost would grow to depths in response to
  surface temperatures only slightly below 0oC.
• However, this outward heat flow results in a
  temperature increase of about 30 K km-1, the
  figure varying with regional geological
  conditions.

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• Thus the base of permafrost approaches an
  equilibrium depth where the temperature increase
  caused by this geothermal gradient just offsets
  the amount by which the surface temperature is
  below freezing.
• Whereas the base of permafrost is determined by
  the mean surface temperature and geothermal heat
  flow, the upper layers of permafrost are
  influenced more by seasonal and interannual
  fluctuations of temperature and snowpack.

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• The major variation in surface temperature has a
  period of one year, corresponding to the annual
  cycle of solar radiation (there is also a diurnal
  variation corresponding to the daily cycle of
  radiation).
• Temperature variations experienced with the
  passage of the seasons at the surface extend in a
  progressively dampened manner to a depth of some
  10-20 m.

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• Within the layer of annual variation, maximum and
  minimum figures form an envelope about the mean,
  and the top of permafrost is that depth where the
  maximum annual temperature is 0oC.
• Superimposed on normal periodic variations are
  other fluctuations with durations from seconds to
  years causes may included sporadic cloudiness,
  variations in weather and changes in climate.

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• Let us now imagine some change in climatic
  conditions which causes mean annual surface
  temperature to rise.
• The result would be deepening of the active
  layer, as both the mean annual temperature and
  the envelope of maximum (summer) temperatures
  shift to higher values.
• If climatic warming were sustained, the
  permafrost table would recede further year by
  year and the base of the permafrost would begin
  to rise as surface warming propagated to greater
  depths.

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• If the progressive warming were great enough,
  then permafrost could eventually disappear
  altogether.
• Since permafrost is a thermal condition, it is
  potentially sensitive to changes in climate.
• However changes in the thermal regime of the
  ground that lead to degradation (or formation) of
  permafrost can result from environmental changes
  other than fluctuations in climate.

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• For example, removal, damage, or compaction of
  surface vegetation, peat, and soil alters the
  balance of surface energy transfers, generally
  raising mean summer surface temperature and
  thawing the upper layer of permafrost.
• In winter, increases in snow cover accumulation,
  as can result from barriers, structures, and
  depressions or changes in wind patterns, can lead
  to significant warming of the ground.
• Decreases in snow cover, in contrast, lead to
  cooling of the ground, other things being equal.

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• While the effects of surface environmental
  changes are usually restricted in areal extent,
  climatic change can affect extensive areas of
  permafrost.
• Even modest climatic warming could have drastic
  effects for terrain conditions and northern
  engineering, since thousands of square kilometers
  of warm permafrost would be directly affected.
• While many centuries would be required for
  complete degradation of the affected permafrost,
  thawing from the surface would begin immediately,
  with many potentially serious results.

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• There is some evidence that permafrost has been
  retreating during the past decades Syslov (1961)
  reports that the permafrost extent at Mezen
  (Russia) has retreated northward at an average
  rate of 400 m per year since 1837, whereas
  similar findings have been reported for the
  Mackenzie Valley of Canada.
• Although permafrost is temperature dependent, the
  relation with climate is not straightforward,
  since the surface temperature regime does not
  depend solely on geographic location.

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• Local surface conditions such as the type of
  vegetation, depth of snow cover, soil type, and
  moisture content, profoundly affect the surface
  energy regime, being interposed between the
  atmosphere and the ground.
• Thus myriad local variations of vegetation,
  topography, and soil conditions can cause
  differences in mean ground temperatures of
  several degrees over quite small areas. Wherever
  average temperature is within a few degrees of
  0oC, such variation mean that permafrost occurs
  in patches, or discontinuously.

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• These circumstances, together with the scattered
  nature of direct observations, make precise
  mapping of permafrost difficult.
• While cold is usually seen as the singular
  feature of high latitudes, problems resulting
  from thaw are generally of greater practical
  concern.

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• Where permafrost contains ground ice,
  considerable thaw settlement can occur and such
  action has been responsible for significant
  damage to buildings, roads, runways, etc. and
  increased action would undoubtedly cause
  additional and severe maintenance and repair
  problems.
• Special concern might be directed to existing
  water-retaining structures, such as reservoirs,
  and hydrodams, especially in areas of
  thaw-sensitive permafrost.

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• Erosion of lake, river, and reservoir shorelines
  may increase because of permafrost thawing and a
  longer open-water season.
• Greater sediment transport in rivers could
  shorten the operating life of hydro-electric
  projects, for example.
• The expected rise in sea level accompanying
  global warming could accelerate coastal retreat
  in permafrost regions and combined with thaw
  settlement as permafrost melts, could produce
  inundation of low-lying areas.

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Potential Changes in the Components of the
Surface Water Budget, Kuparuk River Basin
Source Déry et al. (2005), JHM.
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Source Anisimov (2006)
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Slaymaker and Kelly (2007)
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Source Lawrence and Slater (2005)
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Source Lawrence and Slater (2005)
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Source Vavrus (2007)
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