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particles deposited over snow and ice are transported by wind and gravitational
falls (mass removals). If the thickness of the particles is less than about 1 inch
(Espinoza, 2018), a larger loss of snow and ice will occur due to enhanced
absorption of solar radiation since these particles are normally darker than the
glacier and snow surface. For example, in the eastern sector of the Northern
Patagonia Icefield, an increase of 68% of the surface covered by debris in
glaciers has been reported in the period 1944-2014 (Farías-Barahona, 2015). In
the central Chilean Andes, Shaw et al. (2020) concluded that the albedo of
glacier ice decreased by 7% during the 1986-2009 period.
A third feedback mechanism originates from the altitudinal gradient of the
atmospheric temperature, which results in an average altitudinal temperature
gradient of 6.5˚C/km. Due to global warming, the glaciers are experiencing a
significant thinning, so their surface level decreases, being subjected as a
consequence to higher temperatures at lower levels due to the altitudinal
temperature gradient.
Water contribution
As a result of the presence of seasonal snow and glaciers, the mountain ranges
are recognized as true "water towers" (Schoolmeester et al., 2018). In central
Chile, for example, it is well known that the highest water flow occurs towards
mid/late spring due to seasonal snowmelt. Subsequently, towards the mid/end
of summer, the largest water contribution originates from glaciers. However, it
is considerably less than the contribution from seasonal snow, reaching up to
2/3 of the runoff for extremely dry years (Ayala et al., 2020).
Glaciers are natural water reservoirs that accumulate water in solid form during
the snow accumulation period and deliver water mainly during the summer
season, when it is most needed, particularly for agricultural use, which in Chile
represents around 70% of water consumption. Due to global warming, glaciers
initially contribute to more meltwater. However, as the glacier masses decrease
below a certain critical size, they begin to contribute less water due to the
gradual decrease in the ice surface. This way, the water supply from glaciers
has had an increasing trend in recent decades, reaching a "peak water flow" and
decreasing after that. This peak water flow is reached in the short/medium term
for small glaciers. For large glaciers, for example, those in the Olivares River
basin, around the Palomo volcano in the interior of Rancagua/San Fernando in