People in the Mountains - Mountain Geography: Physical and Human Dimensions - page 504

produce warming and drying effects through compression of the moving air. “Valley
winds,” blowing upslope during the day, and “mountain winds,” blowing downslope dur-
ing the evening and night, are common in mountain areas. Wind acts as the transport
agent for particulates, including snow, gases, allergens, and contaminants, creating a
variety of hazardous conditions. In redistributing and altering snow, wind can contrib-
ute to the build-up of serious snow avalanche hazards. Very high-velocity foehn, kata-
batic, and storm-generated winds can generate very high-impact pressures that damage
and destroy structures, transmission lines, forests, and crops, and interrupt essential
services in mountain areas.
Mountain people have long experience in coping with and adapting to these con-
ditions. Settlements, buildings, and other structures are built in wind-sheltered sites
and are strengthened to withstand high-impact pressures. Mountain farmers may seek
wind-protected niches for their crops and livestock. Along roads, snow fences and plant-
ings are used to reduce wind-driven snow hazards. On the other hand, wind-driven snow
is captured by snow fences and plantings to augment snow on ski slopes and water sup-
ply and, increasingly, the windiness of mountain areas and their immediate surround-
ings is being used for electricity generation.
Snow and Ice
Snowcover, glacier ice, and, to a lesser degree, ground ice are present in many high
mountain areas and are embedded in the lives of people in and out of the mountains,
serving as water supply sources, scenic enhancements, and recreation resources for
tourism and recreation, as well as creating hazards in the form of snow avalanches, ice-
falls, rapid glacier advances (surges), and glacier lake outburst floods. As discussed in
Chapter 4, some of the most obvious indicators of present global warming and other
climatic variations have been reductions in mountain snow and ice cover over the past
150 years. The changes have been most pronounced in the shrinkage of glaciers, to the
point where some small glaciers in tropical and temperate mountains, for example, on
Mount Kenya in Africa and in Glacier National Park in the United States, representing
equatorial and midlatitude locations, have disappeared (Watson et al. 2008). Continu-
ation of this trend raises the specter of reduced water supply for people dependent on
snow and ice sources. Depletion of the summit snow and ice cap of Kilimanjaro has be-
come an icon for global climate change (Molg et al. 2010), while the shrinkage or dis-
appearance of glaciers on nearby Mount Kenya threatens water supply to subsistence
and commercial agriculture and horticulture on its lower slopes (Kaser et al. 2005). The
equatorial Andes retain a greater but shrinking glacier ice cover, which has been im-
portant as a local and regional water source for generations. In the tropical Andes, the
melting of snowcaps and glaciers is considered by the indigenous people to be a myth-
ological and cultural loss. There, glacier shrinkage compromises future water supply
for agriculture, industry, settlements, and power generation, as well as temporarily in-
creasing the frequency of damaging snow, ice, and rock avalanches and glacier lake out-
burst floods (GLOFs) (Carey 2010). With some exceptions, the cover of mountain snow
and ice increases in amount and extent and decreases in altitude from the equator to
the poles. The very large glacier systems of the northwest Himalaya and Karakoram in
subtropical latitudes, at very high altitudes, and driven by copious snowfall are among