Mountain Landforms and Geomorphic Processes - Mountain Geography: Physical and Human Dimensions - page 242

Future warming will likely have diverse effects on the existence of permafrost. With
increasing temperatures, permafrost may become a “historical curiosity” in which such
landforms and processes no longer exist (Barsch 1993). Permafrost zones and processes
may shift, and increased melting of permafrost will thicken active layers (Price and
Barry 1997). Thermokarst could dominate in some regions where ground ice is being
depleted, making development of roads, pipelines, or airfields more difficult. Develop-
ment on permafrost will become difficult with future warming because most builders
try to keep permafrost intact. In a warmer climate, developers must address differen-
tial heaving, sinking of portions of the surface, destruction of bridges by spring floods,
burial of pavement by slumping or mass movements. Future development on permafrost
will have to use new technology or techniques for construction (Ritter et al. 2002).
Climate change will also affect other microclimate variables related to permafrost
aggradation or degradation (Williams and Smith 1989). A series of complex feedbacks
will determine permafrost survival. Greater rates of evaporation will cause cooling of
the ground. An increase in summer rainfall, or decreasing winter snowfall, may offset
some permafrost warming compared to the magnitude of air temperature increase
(Wu and Zhang 2008). Thermokarst from melting permafrost may act as snow traps in
winter, thus further warming the soil. With more CO 2 available, vegetation could have
higher productivity. Wetter (but not necessarily warmer) soils could enhance carbon and
nitrogen production, which would provide an additional greenhouse gas contribution
(Baumann et al. 2009). When warmer temperatures occur at higher elevations, veget-
ation will succeed or encroach upon alpine tundra where permafrost commonly occurs
(Beniston 2000). Changes in vegetation patterns will also influence local microclimatic
variables. Areas with no vegetation show the greatest annual range of temperature. As
trees encroach, the annual amplitude will be less, which, depending upon the temperat-
ure regime, could cause permafrost to aggrade or degrade. Trees will also act as snow
accumulators, which is far less important than their shading and cooling effects. Areas
with trees will be cooler than tundra in the summer, but warmer in the winter because
of snow fencing and trapping of snow (Williams and Smith 1989).
The timing, depth, and duration of snowpack will have an impact on permafrost ex-
istence. The date of spring snow-pack melt has come earlier over the past 54 years in
Australia (Green and Pickering 2009). Clow (2010) showed that MAAT at high elevations
in the Colorado Front Range has increased by about 1.0°C per decade from 1983 to
2007, and that the timing of snowmelt is two to three weeks earlier. The mountain west
of North America, especially the Cascade Mountains and northern Colorado, has exper-
ienced declines in spring snowpack, despite increases in winter precipitation (Mote et
al. 2005). An increase in winter snowpack has the potential to warm ground through
insulation, and earlier spring snowmelt exposes the ground to warmer summer temper-
atures. Each is detrimental for permafrost occurrence.
Predicting future change will be improved through the use of geospatial models,
such as ALPINE3D, which measures alpine snow processes (Lehning et al. 2006). Geo-
spatial tools combined with field measurements can help investigate permafrost devel-
opment or destruction under a variety of scenarios.
Warming of permafrost will also initiate other hazards. Groundwater seepage causes
some rockfalls; therefore, if groundwater pressure rises with increased precipitation in-
duced by a wetter climate, this could trigger rockfalls. As permafrost degrades, there