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to the south of Chile (18°–40°S), an average decrease of 38% of the areal snow
cover in the dry summer season was verified in 1986-2018 (Cordero et al.,
2019).
Glacier retreat
The
glaciers,
in
their
condition
of
"perennial
snows",
as
well
as
the
seasonal
snow,
are
retreating all over the world
due to global warming, with
few
exceptions.
Chile
has
approximately 80% of the
Andean glaciers, including
the
large
Patagonia
and
Tierra del Fuego icefields,
almost
all
of
which
are
losing
mass
at
an
accelerated rate due to frontal and margin retreat and also thinning (Figure 1).
Glacier mass balance is defined as the mass gain during the snow accumulation
period (usually winter) minus the mass loss during the ablation period (usually
summer). If the glacier loses more mass than it gains, then its balance will be
negative. At a global level, during the period 2000-2010, in practically all
mountain ranges of the world, glaciers lost a global average of 0.54 meters of
water equivalent per year, that is about 0.64 meters of ice thickness per year,
which represents an increase of 64% with respect to the global average mass
balance of the glaciers during the second half of the 20th century, in accordance
with the global increase of near-surface air temperature (Zemp et al., 2015). An
emblematic glacier is Echaurren Norte, located east of Santiago, immediately
north of the El Yeso dam and Laguna Negra. This pilot glacier, monitored by
the General Water Directorate, has the longest mass balance record in the Andes
and is the only “reference” glacier in the southern hemisphere (Farías-Barahona
et al., 2019). Since 1975, Echaurren Norte has lost 32.1 meters of ice thickness
(Figure 2), with a loss of 20.8 meters (that is 65%) concentrated in the last 12
years since the mega-drought began. The combination of the mega-drought with
atmospheric warming has also contributed to the fragmentation of this glacier