(2009) also noted glacier growths in certain portions of
SPI
during the first half of the past millennium. Sakakibara and
Sugiyama (2014), in their analysis of 26 calving glaciers from
1984 to 2011, noticed small advancements in two termini of
the Pío XI glacier. Espizua and Pitte (2009) noticed some peri-
ods of minor advances in the Central Andes. They concluded
that the positive mass balance during the period was the out-
come of the warm El Niño-Southern Oscillation (
ENSO
) events.
Glaciers of Chile act as a valuable source of fresh water as
their summer runoff contributes to several river basins. It is
an important water resource to the populated and eco-regions
of the Chile (Rivera
et al.
, 2006). But due to the inacces-
sible terrain and lack of data, the mass balance of the South
American Cryosphere has not been documented extensively.
As a result, the region has suffered from the absence of a
systematic, long-term, and validated mass balance program
(Bamber and Rivera, 2007; Dyurgerov and Meier, 1997). In
this paper, we use data that were generated using active and
passive remote sensing techniques to analyze the state of gla-
ciers in the Southern Andean Cryosphere from 2004 through
2008. We use
GLAS
and
SRTM
elevation data to study trends in
glacier wastage in the region. We examine regional elevation-
difference trends in clean ice and analyze glacial thinning in
the Southern Andes.
Study Area
Most of the glaciers in the South America are located in
Argentina and Chile. These glaciers are found typically in
an area from 17° 30
′
S latitude to the southern tip of South
America at 55°S latitude (Figure 2). The Pacific Ocean in the
West and the Andes Cordillera to the East influence the atmo-
spheric conditions in the region. Varieties of glacier forms,
such as mountain glaciers, valley glaciers, cirque glaciers, out-
let glaciers, Piedmont glaciers, ice caps, and ice fields, spread
across more than 4,000 km along the Andean mountains in
Chile and Argentina (Lliboutry, 1998).
The climatic parameter differs along the longitude and
latitude as the study region extends from northern Chile to
Southern Argentina (Garreaud
et al.
, 2009). Annual rainfall
increases from 100 mm to 2,000 mm along the latitude within
the central region (Montecinos and Aceituno, 2003). The stud-
ies on climate variability in the region reported a decrease in
the precipitation and a diminutive increase in temperature
(Favier
et al.
, 2009; Rabatel
et al.
, 2011). The complex land-
scapes of the Andes create numerous microclimatic zones in
the study region (Rosenblüth
et al.
, 1997).The varying climatic
conditions and topography along the Andes influence the de-
velopment of glacial masses. Therefore, we divided the study
area into four regions based on climate and topography. These
divisions help overcome statistical bias and avoid overlying
dissimilar radar signal footprints (Kääb
et al.
, 2012). These
four climatic regions are Dry Central (31°S–35°S), North Wet
(35.1°S–46°S), South Patagonian Icefields (48.15°S–51.4°S),
and Cordillera Darwin Icefield (54.20°S–55°S) (Figure 2)
(Lo-
pez
et al.
, 2010; Williams and Ferrigno, 1998).
In typical meteorological circumstances, stationary high
pressure stretches out crosswise over South America at about
35°S and along these lines keeps any intrusion of moisture-
laden air masses into the landmass (Lliboutry, 1998). In the
regions, most precipitation occurs in the winter, between
May and August. The summer months are from December
to February (Paruelo
et al.
, 1998). In this study, we grouped
ICESaT
footprints of December through February as dry season
footprints. We restricted trend analysis to only the dry season
ICESaT
footprints for an unbiased comparison with
SRTM DEM
,
which is dated February 2000.
In the North Wet region, precipitation anomalies are prom-
inent during the El Niño and La Niña periods in the Central
Andes. The
ENSO
effect varies across geographic locations. In
the El Niño years, above-average precipitation occurs between
30°S and 35°S latitudes from June to August, and between
35° and 38°S from October to November. In contrast, the op-
posite pattern is observed during La Niña years (Montecinos
and Aceituno, 2003). On the western side of the Patagonian
Icefields, near the Pacific Ocean, marine impact and westerly
frontal frameworks affect the atmosphere. A heavy north-
south atmospheric pressure gradient induces strong and moist
westerly winds over Patagonia south of 45° 5′ S (Lliboutry,
1998). The southern
SPI
receives the most extreme precipita-
tion along the coast, at around 51° S (Lopez
et al.
, 2010).
The
CDI
region (Figure 2) is by far the least inspected part
of the Southern Andean cryosphere. The lessening of pre-
cipitation to the east is observed in the
CDI
. Throughout the
winter, strong winds begin from the west and, at the same
time, cold air comes from the polar region (Holmlund
et al.,
1995; Lopez
et al.
, 2010).
These diverse climatic patterns influence glacial extent,
mass and velocity in the Andes. Any deviation in normal
climatic patterns will bring significant change in the Andean
Cryosphere.
Data
We used all footprints of the elevation product of GLA14
release 533, Geoscience Laser Altimeter System (
GLAS
) aboard
the Ice, Cloud and land Elevation Satellite (
ICESaT
) campaign
from 2004 to 2008 that overlay glaciers in the Andean cryo-
sphere. The
GLAS
transmits short pulses (40 pulses per sec-
ond) of infrared light (1064 nm) and visible green light (532
nm). Laser footprints are about 70 m in diameter and spaced
Figure 2. Illustration of the study area in South America.
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October 2016
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