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Glacier inventory of the upper Huasco valley, Norte Chico, Chile: Glacier characteristics, glacier change and comparison with central Chile


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Results of a new glacier inventory of the upper Huasco valley, which lies within the arid Norte Chico zone of the Chilean Andes, are presented for 2004. Despite the high altitude, the glaciation in this region is limited in extent and is not classical mountain glaciation, which poses difficulties in completing standard inventory attribute tables. Small cornice-style ridgeline features constitute a large number of the non-transient ice bodies identified, and glaciers with surface areas <0.1 km2 comprise 18% of the glacierized area and 3% of the water resource stored as glacier ice within the Huasco valley. Rock glaciers are an important component of the cryosphere, comprising 12% of the total water volume stored in glacial features. Changes in glacier area over the last ∼50 years are in line with those for glaciers in central Chile despite the contrasting climate conditions. Projections of glacier area change based on glacier hypsometry and zero isotherm shifts predicted using the PRECIS regional model temperature change for IPCC scenario B2 conditions suggest that the survival of 65% of glacier area and 77% of active rock-glacier area will be threatened under forecast conditions for the end of the 21st century.
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Glacier inventory of the upper Huasco valley, Norte Chico, Chile:
glacier characteristics, glacier change and comparison with
central Chile
Jorge MARI
David LOPEZ,
Antoine RABATEL,
Francisca BOWN,
Centro de Estudios Avanzados en Zonas A
´ridas (CEAZA), Benavente 980, Casilla 599, La Serena, Chile
Centro de Estudios Cientı´ficos (CECS), Av. Arturo Prat 514, Mailbox 1469, Valdivia, Chile
Departamento de Geografı´a, Universidad de Chile, Portugal 84, Casilla 3387, Santiago, Chile
ABSTRACT. Results of a new glacier inventory of the upper Huasco valley, which lies within the arid
Norte Chico zone of the Chilean Andes, are presented for 2004. Despite the high altitude, the glaciation
in this region is limited in extent and is not classical mountain glaciation, which poses difficulties in
completing standard inventory attribute tables. Small cornice-style ridgeline features constitute a large
number of the non-transient ice bodies identified, and glaciers with surface areas <0.1 km
18% of the glacierized area and 3% of the water resource stored as glacier ice within the Huasco valley.
Rock glaciers are an important component of the cryosphere, comprising 12% of the total water volume
stored in glacial features. Changes in glacier area over the last 50 years are in line with those for
glaciers in central Chile despite the contrasting climate conditions. Projections of glacier area change
based on glacier hypsometry and zero isotherm shifts predicted using the PRECIS regional model
temperature change for IPCC scenario B2 conditions suggest that the survival of 65% of glacier area and
77% of active rock-glacier area will be threatened under forecast conditions for the end of the 21st
In the semi-arid Norte Chico region of Chile (27–338S), the
evolution of the cryosphere is of concern for local
populations because of its role in local water resources.
Although the region contains peaks in excess of 6000 m
a.s.l., low precipitation and strong ablation, a large portion
of which can be sublimation (Ginot and others, 2002), mean
that glaciers are limited in both number and extent (total ice
coverage in Norte Chico administrative regions of 73.85km
(Garı´n, 1987; Rivera and others, 2000)). Despite the limited
glacier extent, glacial meltwaters, when combined with
snowmelt, are an important component of the hydrological
resources (Favier and others, 2009) providing water that is
vital for the regional economy.
The mountain climate is characterized by persistent low
temperatures and humidity levels and generally clear skies.
Meteorological conditions measured over 7 years at the
Pascua-Lama mine exploration site (298S, 708W, 5000 m
a.s.l.) show that monthly mean temperature remains nega-
tive year-round, monthly mean relative humidity is 34–54%,
precipitation is concentrated in the winter season between
May and August, and monthly mean wind speed remains
above 4 m s
. Synoptic-scale winds are predominantly
westerly but are deflected southward along the Andean
range (Kalthoff and others, 2002). Prevailing wind direction
at the Pascua-Lama meteorological stations is from the
northwest to north-northwest.
The glaciers of northern Chile (18–328S), including Norte
Chico, were inventoried using aerial photographs from 1955
and 1961 (Garı´n, 1987). The report for this inventory
highlights that in northern Chile: (1) it is not usually possible
to separate permanent accumulations of snow from ice
because glaciers show few surface signs of flow;
(2) permanent snowpatches were likely to be a significant
hydrological resource; (3) the glacial group at Los Tronquitos
(28832’ S) is the most significant concentration of ice in
northern Chile; (4) clearly defined moraine forms were
absent; and (5) rock-glacier features present in Norte Chico
were difficult to identify as some did not show surface flow
features. Rivera and others (2000) noted that as this
inventory was not well associated with watersheds, more
detailed work was required to make better hydrological
This paper presents the findings of a new inventory of the
upper Huasco valley (Fig. 1) based on Advanced Spaceborne
Thermal Emission and Reflection Radiometer (ASTER)
images from 2004, presents an assessment of glacier type
and glacier evolution in this watershed, and compares the
results with those from a similar study in the upper
Aconcagua valley (338S), central Chile (Bown and others,
Images and image treatment
All the materials used in this study are presented in Table 1.
The inventory work was carried out using ASTER images
from 2004 (Fig. 1), but the orthorectification process used
images from 2002 and 2003 as well. A 15 m digital terrain
model (DTM) was generated from the ASTER images using
the ASTER DTM module for ENVI. The same module was
Annals of Glaciology 50(53) 2009
*Present address: Center for Climate and Cryosphere, Department of
Geography, University of Innsbruck, Innrain 52, A-6020 Innsbruck, Austria.
used to orthorectify the images using an additional vectorial
input of the 1 : 50 000 scale drainage network produced
from the cartography of the Instituto Geogra´fico Militar
(IGM). The rectified images were mosaicked and colour
balanced using ENVI software. The catchment boundaries
were determined from the 1:50 000 contours (IGM). Near
the Argentine border, there is some discrepancy between the
catchment boundaries determined this way and the ridge-
lines evident in the rectified ASTER mosaic. The DTM is
expected to have a maximum of 10% difference to reality,
and horizontal and vertical accuracy of 30 and 15m,
respectively (Toutin, 2008). Additional differences may be
introduced because: (1) the ASTER images in this zone were
not rectified with the use of further ASTER images to the east;
(2) the drainage network vector used to optimize the
rectification process covers the Chilean territory only, so
does not cover all of the easternmost ASTER images; and (3)
the catchment boundary follows the ridgeline and the
rectification procedure is less accurate in high-relief areas.
In places, the eastern catchment boundary was corrected
manually to ensure glaciers draining to Chile are included in
the inventory. Aerial photographs taken between 1996 and
1999 were used as a reference for feature identification
rather than delimitation and also as a means of determining
the non-transience of features to be included in the
Glacier delimitation
Snow and ice features identified in both the aerial
photographs from the late 1990s and the 2004 ASTER
images were considered as perennial and were included in
the inventory, although some of these bodies are of very
Fig. 1. Location of the Huasco valley showing the El Transito and El Carmen sub-catchments. ASTER images used for glacier delineation are
indicated in grey.
Table 1. Images and spatial data used in the study
Image/material Source Years Resolution/scale
ASTER ASTER 2002–04 15 m pixel
Aerial photographs GEOTEC flight 1996–99 1 : 50 000
Contour lines Instituto Geogra´fico Militar, Chile Based on air photography from 1955 Hycon flight 1 : 50 000
Huasco drainage network Direccio´n General de Aguas, Chile 1 : 50 000
Nicholson and others: Glacier inventory of the upper Huasco valley112
small surface area and it is not clear from the images
whether they would be classified as ne´ve´s, glacierets or
glaciers. The term ‘glacieret’ defines an ice body that is
formed primarily by blowing or avalanching snow, which
usually shows no surface signs of flow (Mu
¨ller and others,
1977; Rau and others, 2005). Additionally, this inventory
includes rock glaciers due to their prevalence in the basin
and consequent role in hydrological resources.
Snow and ice feature limits were mapped manually from
ASTER images taken on 14 February 2004, which is late
summer and so should present the most snow-free condi-
tions. Where transient snowpatches were identified to be
merging with permanent snow and ice features, the transient
portion was excluded from the inventoried area.
Only rock glaciers deemed to be active were included in
the inventory, as inactive rock glaciers may in fact no longer
contain ice and thus would not form part of the hydrological
resource of the catchment. Rock glaciers were determined to
be active if they showed: (1) a colour contrast between the
frontal slope and upper surface, as this was considered to be
indicative of ongoing frontal activity; and (2) evidence of
surface flow features. There are numerous fossil rock-glacier
features and valley fill deposits that may still contain some
quantity of ice, but as this is unknown such features were not
included in the inventory. Upper limits of rock glaciers were
taken to be the break of slope above the highest surface flow
The characteristics of mapped glaciers were entered into a
database to include the data requirements of both the
Chilean Direccio´n General de Aguas (DGA), which is based
on the World Glacier Inventory (WGI) database, and also
the Global Land Ice Measurements from Space (GLIMS)
database. Thus two identities were generated for each
glacier mapped, a UNESCO (WGI) name, based on country
and catchment, and a GLIMS ID, based on latitude and
longitude. Glaciers were classified using both the UNESCO/
WGI and expanded GLIMS system. The glaciers in this
region do not have classical altitude-delimited accumu-
lation and ablation areas, and instead wind patterns
determine the spatial distribution of accumulation. Addi-
tionally, the whole surface can be an accumulation or
ablation zone depending on the interannual climate vari-
ation (A. Rabatel and others, unpublished information), so
the field referring to dimensions of the zonation of the
glacier surface was filled with ‘not applicable’. Similarly, it
was not possible to identify snowlines. The WGI database
requests mean glacier width and length, but as the ice
bodies mapped in the upper Huasco valley are small, and
do not generally have a ‘tongue’ form the width of which
can be measured, or multiple tributary flowlines, these
fields were filled with maximum glacier dimensions in-
stead. Maximum length and width were measured as
straight line vectors parallel to and perpendicular to the
main contour trend of the ice body given by the IGM
1:50 000 contours. Maximum and minimum elevations
were determined from the polygon outlines and elevations
derived from the DTM. Glacier orientation was determined
automatically using the Landscape Management System
(LMS Tools) extension for ArcView 3.3; this extension
determines the predominant orientation and slope in a
polygon using a gridded DTM, in this case taken from the
IGM 1 : 50 000 contours.
Mean glacier thickness was determined in accordance to
an area–thickness relationship determined for glaciers in the
Maipo valley of central Chile (Marangunic, 1979). Analysis
of four ice bodies in the upper Huasco valley for which
ground-penetrating radar (GPR) thickness data are available
shows that the only glacier of the group is a good fit to the
relationship, but of the three glacierets, two are outliers,
with the positive outlier being a cornice glacieret (Fig. 2).
From this we assume that the relationship applies to glaciers
in this area as well, but it is less applicable to glacierets and
may be likely to underestimate the thickness of cornice
accumulations. Ice volumes were then estimated from the
mapped glacier area and approximated mean ice thickness.
Ice volume of rock glaciers was estimated following the
method of Brenning (2005), which assumes the average ice-
rich thickness of all rock glaciers to be 30 m and the
volumetric ice content of this layer to be 50%. It should be
noted that in the absence of bedrock topography and a more
extensive program of GPR surveying on glaciers in the
region, the ice volume estimates should be considered
approximations only and it is impossible to provide error
estimates on them. Water equivalents were calculated from
these ice volumes using ice densities of 0.9 kg m
for the
glaciers and 0.8 kg m
for the rock glaciers (Brenning,
Glaciation is limited in the upper Huasco valley, and many
perennial features mapped are very small and are likely to
be glacierets, ne´ve´ patches or perennial cornices. In the first
instance we consider all solid water features that were
identified as perennial, and subsequently we consider
thresholds for exclusion of smaller bodies. In the following
discussion, all snow, firn or ice bodies are referred to as
‘glaciers’ for simplicity.
Fig. 2. Relationships between glacier surface area and mean
thickness. Grey diamonds and equation indicate the relationship
given by Marangunic (1979); black squares represent three
glacierets and one glacier in the Huasco valley computed from
GPR measurements made by Golder Associates as part of the
glacier monitoring program of the future Pascua-Lama mining
project (Barrick Gold Corporation).
Nicholson and others: Glacier inventory of the upper Huasco valley 113
Of 152 glaciers identified, 111 were clean-ice glaciers, 1
was identified as having a debris-covered terminus and so
was termed a debris-covered glacier and 40 were active rock
glaciers. This population was considered as two groups:
‘glaciers’ (which includes the single glacier with a debris-
covered terminus) and ‘rock glaciers’. These two groups
constitute a total area of 23.17 km
of glacial features, of
which 16.86 km
are glaciers and 6.30 km
are rock-glacier
surfaces. Table 2 shows the distribution of glaciers within the
sub-catchments shown in Figure 3. In comparison, in his
inventory based on images from 1955 and 1961, Garı´n
(1987) identified 15 glaciers and snowpatches in the Huasco
valley, ranging from 0.01 to 5.60km
, although the latter
area refers to a large snowpatch that was covering the
location of present-day glaciers. The total ice-covered area
given by Garı´n was 20.16 km
, which is 3.30 km
more than
the inventoried glacier area presented here for 2004.
However, it should be noted that the two inventories are
not directly comparable due to different techniques, imagery
and scale of mapping used. The total estimated water
volume of the glacier and rock-glacier component of the
cryopshere in the upper Huasco valley in 2004 is
614.74 Mm
, of which 12% consists of rock glaciers.
Glacier distribution is strongly controlled by aspect, with
the result that over 80% of all the glaciers are on slopes
orientated towards the southeast, south and southwest
sectors. This preference is likely to be due in part to solar
influences and in part to preferential lee-slope snow
accumulation. There is no strong relationship between
glacier size and latitude or longitude, as the glaciers are
focused along high ridgelines. The hypsometry shows the
majority of clean-ice area between 5000 and 5200 m a.s.l.,
and the majority of rock-glacier surface area is found
between 4000 and 4400 m a.s.l. (Fig. 4). To elucidate this
elevation distribution of glacial features in terms of air
temperatures, the current zero-degree isotherm altitude
(ZIA) was computed from two weather stations (3975 and
4927 m a.s.l.) at the Pascua-Lama exploration mine site for
6 years (2001–2007). Annual ZIA is 4112 m a.s.l., and
summer (December–March) ZIA is 4718 m a.s.l. This annual
value is higher than that predicted from radiosonde
measurements from coastal stations spanning 30–388S
(Carrasco and others, 2005), which would suggest a ZIA of
about 3200 m a.s.l., but is considered a more accurate
representation for the upper catchment. Using these values,
glacier surface area can be seen to exist above the summer
ZIA, while rock glaciers are found between the annual and
summer ZIA.
A recommended smallest size of 0.1 km
for features
included in a glacier inventory is often used on the basis of
optimizing comparability between inventories using differ-
ent image types with different pixel resolution, for example
if Landsat Thematic Mapper (25m pixel) images are being
used. Applying this cut-off point to our data removes 70% of
the glaciers counted, which represent 18% of the glacier
area but only 3% of the estimated glacier volume. In the
case of rock glaciers, this size threshold results in the
rejection of 50% of those counted, representing 15% of the
rock-glacier area and volume (Table 3).
Many of the clean-ice glaciers identified were associated
with ridgelines and are likely to be permanent or semi-
permanent snow cornices. These cornice features tend to be
wider than they are long (where length is defined in the
downslope direction) and were identified numerically using
the ratio of glacier length to glacier width. Of the 112
glaciers, 40% have a length/width ratio <1, suggesting they
are ridgeline or cornice features. Eight of the 34 glaciers with
surface areas >0.1 km
were wider than they are long (24%),
while 37 of the 78 glaciers with surface areas <0.1 km
classified as ridgeline or cornice features (47%). Given that
the area to average thickness relationship we used for glaciers
appears to underestimate the volume of cornice features
(Fig. 2) and that almost half of the small features excluded by
this cut-off threshold are identified as cornice features, this
suggests that the ice and water volumes represented by
features <0.1 km
in Table 3 are a minimum estimate.
Table 2. Glacier areas in terms of WGI rank sizes, separated by sub-catchments (see Fig. 3) and by glacier type
Rank 1 (0.01–0.1 km
) Rank 2 (0.1–1 km
) Rank 3 (1–10 km
) Rank 4 (>10 km
Number Area Number Area Number Area Number Area
Glaciers (Debris-covered glaciers)
Laguna Grande 6 0.26 8 1.82 1 1.83
Valeriano 17 0.81 7 1.53
Cholloy 12 0.42 2 0.46 1 1.50
Potrerillo 25 0.94 12 (1) 4.49 (0.19) 1 1.92
Carmen 17 0.58 1 0.10
Socarron 1 0.03
All glaciers 78 3.03 30 (31) 8.40 (8.59) 3 5.24
Rock glaciers
Laguna Grande 1 0.04 4 1.25
Valeriano 5 0.29 3 0.96
Cholloy 9 0.35 9 2.42
Plata 1 0.19
Potrerillo 5 0.24 2 0.28
Carmen 1 0.26
All rock glaciers 20 0.93 20 5.38
Nicholson and others: Glacier inventory of the upper Huasco valley114
Type of glaciation in the upper Huasco valley
No classical valley glaciers are present in the upper Huasco
valley, and instead glaciation exists in the form of rock
glaciers and glaciers/glacierets of limited extent. Glacier
distribution is limited to ridgelines and shallow cirques and
shows no regional gradients in glacier size. Even on high
ridgelines, glaciers are limited to south-facing lee slopes,
suggesting that shelter from wind ablation is an important
control of glacier survival.
Methodological considerations
For the semi-arid Andes it is difficult to apply a number of the
standard glacier inventory approaches suggested by WGI and
GLIMS, as the glaciers here do not generally conform to the
classical alpine glacier upon which inventory database par-
ameters were previously based. For the upper Huasco valley
a number of WGI attributes could not be determined. Due to
the small size of ice features in the upper Huasco, maximum
length and width parameters are more applicable than mean
dimensions, and fields on snowline, accumulation and
ablation zones are not relevant to this style of glaciation.
In this region of the Andes, rock glaciers are a significant
water store (Brenning, 2005) and they may become more
hydrologically important under the influence of a warming
climate. Currently, there are no WGI-approved criteria for
mapping rock glaciers. In particular, it is necessary to
develop a standard procedure for identifying the upper limits
and the activity status of rock glaciers, which are both
important factors for determining the area of the feature that
Fig. 3. Mapped glacier features and sub-catchments of the upper
Huasco valley.
Fig. 4. Area–altitude distribution of glaciers and rock glaciers in the
upper Huasco catchment. Horizontal lines show the elevation of
measured (2001–07) annual and summer ZIAs and PRECIS-mod-
elled (2071–2100) annual and summer ZIAs for IPCC scenarios B2
and A2.
Nicholson and others: Glacier inventory of the upper Huasco valley 115
may be ice-bearing. Inclusion of rock glaciers and the
numerous small (<0.1 km
) ice bodies in the upper Huasco
is required for an accurate hydrological estimate of the
glaciological water stores.
Comparison of Norte Chico to central Chile
A recent inventory of the glaciers in the upper Aconcagua
valley (Bown and others, 2008) provides an opportunity to
compare the results of two Chilean glacier inventories in
catchments north and south of the South American arid
Most differences between these two regions can be
attributed to the climatic setting, as the Huasco basin lies
within the semi-arid conditions that prevail north of 328S,
whereas the Aconcagua basin has a more temperate
environmental setting, with higher snowfall especially
during winters affected by El Nin
˜o/El Nin
Oscillation (ENSO) events, when precipitation well above
normal is detected in the Andes of central Chile (Escobar
and Aceituno, 1998).
The outstanding difference between the two catchments
is that there are essentially no debris-covered glaciers in the
Huasco inventory, and rock glaciers constitute almost a
quarter of the total accounted number of features (Table 3),
whereas no rock glaciers were reported by Bown and others
(2008) in the upper Aconcagua valley basin, and a third of
the mapped ice area was debris-covered ice. In the Huasco
basin, spatial distribution of glaciers shows a strong
topographic control, with glaciers existing along ridgelines,
and rock-glacier distribution appearing to be random,
which is suggestive of very local topo-climatic controls and
varying debris supply. In the Aconcagua region, the spatial
pattern of ice distribution shows debris-covered glacier
areas are concentrated in the southern sub-catchments of
the upper Aconcagua valley and a significant increase of
bare ice towards sub-catchments Juncal and Blanco, where
most of the ice storage is located in deeply eroded high-
elevation cirques.
The two basins also differ significantly in terms of glacier
distribution among the size classes. The upper Huasco valley
contains many of the smallest size class of glaciers, which
account for a non-negligible part of the net ice surface of the
catchment, while in the Aconcagua region, where inventor-
ied ice is fivefold larger (Table 4), ice bodies <0.1 km
play a
marginal role.
In the central Chilean Andes, active rock glaciers
generally exist between 3500 and 4250 m a.s.l. in relation
to an annual ZIA of approximately 3600 m a.s.l. (Brenning,
2005). This relationship between ZIA and rock-glacier
distribution is similar to that found in the upper Huasco,
where the lower limit of active rock glaciers coincides
(within 100 m) with the annual ZIA and rock glaciers exist in
a range of 1000 m upwards of this level.
Glacier changes in the north-central Andes 1955–
In Norte Chico, the surface area evolution of Glaciar
Tronquitos (28832’ S, 69843’ W) has been reconstructed
using aerial photographs, showing a frontal retreat rate of
14 m a
between 1955 and 1984 up to 23 m a
1984 and 1996 (Rivera and others, 2002). Expanding on this
work, Figure 5a shows the comparison of glacier surface
area evolution between 1955 and the early 21st century for
six glaciers located between 288S and 338S. Their surface
evolution has been reconstructed using aerial photographs
and satellite images. Estrecho and Guanaco glaciers are
located in the upper Huasco. Data from Rivera and others
(2002) on Glaciar Tronquitos have been updated with the
2004 ASTER images used for this study. Data from Glaciar
Juncal Norte are presented in Bown and others (2008) and
from Juncal Sur and Olivares Gamma glaciers in Masiokas
and others (2008). A good consistency between changes in
Table 3. Summary of upper Huasco inventory showing the area and estimated volume of glaciers and rock glaciers and the same values
considering only features over and under a 0.1km
All identified features Features >0.1km
Features <0.1 km
Percent features <0.1 km
Glaciers Rock glaciers Glaciers Rock glaciers Glaciers Rock glaciers Glaciers Rock glaciers
Number 112 40 34 20 78 20 70% 50%
Total area (ha) 1686.18 630.38 1383.09 537.56 303.09 92.82 18% 15%
Estimated ice volume (Mm
) 599.00 94.56 583.84 80.63 15.15 13.92 3% 15%
Estimated water volume (Mm
) 539.10 75.65 525.46 64.51 13.64 11.14 3% 15%
Table 4. Comparison of inventory data of Huasco and Aconcagua valleys
All glaciers 0.01–0.1 km
0.1–1 km
1–10 km
>10 km
Number Area Number Area Number Area Number Area Number Area
Huasco glaciers 112 16.86 78 3.03 31 8.59 3 5.24
Huasco rock glaciers 40 6.30 20 0.93 20 5.38
Huasco all glaciers 152 23.17 98 3.96 51 13.96 3 5.24
Aconcagua glaciers 159 121 24 1 112 43 22 52 1 24
Nicholson and others: Glacier inventory of the upper Huasco valley116
these six glaciers is observed. Their evolution over this
50 year period is homogeneous, although a slight accelera-
tion could be suggested for some glaciers over the last
decade (Juncal Norte, Olivares Gamma). Although some
local conditions (e.g. topographical constraints (Bown and
others, 2008) or mining activity (Brenning, 2008)) may
modify glacier retreat trends, climate should remain the
main driving factor in glacier behavior.
Figure 5b presents a comparison between glacier loss
during the last 50 years and their initial surface, showing a
good relationship between surface lost and initial surface
area. The small glaciers of the subtropical Andes (i.e.
Estrecho, Guanaco and Tronquitos glaciers) experienced a
greater retreat (in percent of their initial surface) than did the
biggest glaciers of the central Andes of Chile (Juncal Norte,
Juncal Sur and Olivares Gamma glaciers). This size depen-
dency of response to climate also holds true within each
climatic regime, with smaller glaciers within both the Huasco
and the Aconcagua valleys showing a greater reduction in
surface area compared with the climate response of the upper
size-class glaciers within the same basins, which have been
less affected proportionally by climate change.
Glacier change in future climate scenarios
Mid-troposperic warming has been highlighted as a cause for
glacier retreat in central Chile, with changes in air tempera-
ture being more important in causing increases in glacier
equilibrium-line altitude than are changes in precipitation
(Carrasco and others, 2005). On this basis, a simple
prediction of future glacier area change can be made using
projected temperature shifts and the relationships established
between the hypsometrical distribution of glacier surface
area and the ZIA, to generate estimations of future glacier
extent in the Huasco valley. Climate projections for 2071–
2100 using Intergovernmental Panel on Climate Change
(IPCC) scenarios B2 and A2 have been computed by the
Departamento Geofisica of the Universidad de Chile using
the PRECIS regional climate model (model description can
be found at and
outputs are available at
Modelled 2 m air temperatures for 29.258S and 70.008E
were used to compute the temperature change expected
between average baseline (1961–90) and average future
(2071–2100) conditions under the two climate scenarios.
The temperature change was applied to the mean annual and
summer air temperatures measured at 3975 m a.s.l. over the
time period 2001–07. The modern-day (2001–07) lapse rate
was used in conjunction with the projected temperatures to
compute annual and summer ZIA for the B2 and A2
scenarios. Annual (summer) ZIA changes from the modern-
day (2001–07) elevation of 4112 (4718) m a.s.l. to 4497
(5125) m a.s.l. under the conditions of scenario B2, and to
4718 (5400) m a.s.l. under the conditions of scenario A2 for
the period 2071–2100. From the modern-day inventory we
can approximate the lower limit of glaciers as the summer
ZIA and the lower limit of rock glaciers as the annual ZIA
(Fig. 4). Assuming glacial features below these limits will not
be in equilibrium and thus will no longer exist under the
projected conditions, scenario B2 suggests a loss of
11.00 km
(65%) of current glacier area and 4.41 km
(70%) of current active rock-glacier area, and scenario A2
suggests a loss of 16.07 km
(95%) of current glacier area and
5.72 km
(91%) of current active rock-glacier area. However,
it should be noted that these projected changes in glacierized
area in the Huasco valley do not account for changing
precipitation. PRECIS-modelled precipitation for the 2071–
2100 period at the study site shows no significant change in
precipitation amount or trend from the baseline period, but
an increase in interannual variability, which will have an
impact on how glacier mass balances respond to future
climate change.
The glacier-derived water resources from the arid Andes
contribute to the water supply downstream and are particu-
larly important in maintaining summer base flow and water
levels in drought periods. The results of this inventory reveal
that the limited glaciation in the upper Huasco basin
represents approximately 615 10
of stored water. At
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waters and that lost to the atmosphere through sublimation
remains poorly understood, as does the runoff contribution
of rock glaciers in this region. Understanding the interaction
of these ice masses with climate and projected climate
change is likely to be important for long-term water resource
management for the region.
Fig. 5. (a) Surface evolution of sample Chilean glaciers (approximate central coordinates are given) and (b) glacier surface evolution as
percent of the initial (1955) surface area. Data are from air photographs until 2003 and ASTER images thereafter; details of source data and
mapping treatment are in the source articles.
Nicholson and others: Glacier inventory of the upper Huasco valley 117
Images used in this study were procured with funds provided
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Nicholson and others: Glacier inventory of the upper Huasco valley118
... In the second group are studies focusing on synoptic or regional scales, such as glacier inventories (e.g. Casassa (1995); Rivera et al. (2002); Nicholson et al. (2010)) and land-climate dynamics (e.g. Favier et al. (2009);Falvey and Garreaud (2007); Mernild et al. (2016b)). ...
... Lliboutry (1998) observed that due to precipitation and elevation dierences, glaciers in the Desert Andes are considerably smaller than those in the Central Andes. Similarly, Nicholson et al. (2010) highlighted that glaciers in the Desert Andes show few surface signs of ow and are often dicult to dierentiate from permanent snow patches. Figure 1.2 shows the location of the semiarid Andes in Chile and South-America and the glaciers that are later analysed in this thesis. ...
... Knowledge on the actual state of glaciers in the semiarid Andes is scarce in comparison to other glacierised regions of the world, such as the European Alps, and is based mostly on remote sensing studies (Casassa, 1995;Rivera et al., 2002;Nicholson et al., 2010;Janke et al., 2015;Malmros et al., 2016) with few modelling investigations that have explicitly taken into account glacier processes (Corripio and Purves, 2005;Pellicciotti et al., 2008;MacDonell et al., 2013a). However, these investigations have focused on point-scale processes with spatially-distributed analyses almost entirely absent . ...
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The role of glaciers as storages of water resources is of primary importance in arid and semiarid mountain regions characterised by pronounced seasonality and long melting periods without significant precipitation. A robust understanding of the physical processes controlling the energy and mass balance of glaciers in these areas is thus crucial for estimation of water resources and their seasonal variability, long term trends and future changes. It has been suggested that glaciers in dry regions are strongly affected by mass and energy losses associated to surface sublimation, but few studies provide a quantification of its influence at the glacier or catchment scales. The main objective of this thesis is to understand and quantify the role of surface sublimation in the energy and mass balance of glaciers in dry environments, by means of point-scale and distributed physically-based energy and mass balance models. Complementary to this objective, this thesis also addresses three relevant topics in semiarid catchments related to the hydrological role of debris-free glaciers and the modelling of glacier ablation. These topics are the runoff contribution of debris-free glaciers in comparison to that of the seasonal snowpack and debris-covered glaciers, the use of temperature-index models under sublimation-favourable conditions and the spatial distribution of near-surface air temperature over mountain glaciers during the ablation season. As study region, the subtropical semiarid Andes of North-Central Chile (29-34°S) is selected. This region is characterized by elevations up to almost 7000 m a.s.l., a dry environment, a large number of debris-free and debris-covered glaciers and a strong dependence of ecosystems and human activities on fresh water resources originated from snow and ice melt. In this region, it has been suggested that distributed, physically-based models at the glacier and catchment scales can bridge the gap between regional studies based on remote sensing products and specific studies focused on point-scale process understanding. The presented analyses are conducted on seven glaciers for which a unique dataset of meteorological, glaciological and hydrological variables has been collected in the period 2008-2015. The study sites are grouped in two clusters, one in North Chile (29-30°S), in which climatic conditions are particularly dry, and another one in Central Chile (32-34°S), where the climate is more Mediterranean. To achieve the proposed objectives, the collected field data is analysed and complemented with remote sensing products to force several hydrological, melt and energy balance models at different spatial scales. The main results of these analyses can be summarised as follows: i) At the integrated glacier scale, surface sublimation accounts for 6.6\% of total ablation during a 2-month summer period in a selected case study in the Juncal Norte Glacier (33°S). It is found that surface sublimation is negligible in comparison to melt at low-elevation low-albedo sites, but it dominates at high-elevation wind-exposed sites, where it represents most of the total ablation. Negative latent heat fluxes, associated with sublimation, are one of the largest sinks in the glacier energy balance and consistently reduce the energy available for melt. ii) Despite having remarkably different spatial and temporal mass balances patterns, the total annual contribution to runoff of low-elevation debris-covered glaciers is similar to that of high-elevation debris-free glaciers. iii) At low-elevation sites, the performance of an enhanced temperature-index model is good compared to that of an energy balance model and its parameters are transferable from one glacier to another and from season to season. However, its performance and parameter transferability tends to decrease with elevation as energy losses modify the diurnal cycle of surface temperature and lower the correlation of melt and index variables. iv) During warm periods, the most relevant controls of near-surface air temperature over glaciers are off-glacier lapse rates and the advection of cold air by katabatic winds and warm air by up-valley winds. A new air temperature distribution model including these processes has been developed and tested with positive results. In relation to the main research question of this thesis, it is concluded that neglecting surface sublimation in the glacier mass balance has relatively small consequences in the simulation of one ablation season, but it might have large cumulative effects in long term simulations, especially on glaciers in very dry environments, such as Tapado and Guanaco glaciers in North-Chile. Physically-based (or oriented) distributed models, as the ones presented in this study, have the potential to shed light on the dominant processes and energy and mass fluxes on glacierised catchments, and their spatial and temporal patterns. However, much work needs to be committed to i) develop model components that reproduce still poorly-known processes, such as turbulent fluxes on penitente fields or ablation processes on debris-covered glaciers, ii) generate appropriate meteorological forcing fields, and iii) obtain the corresponding on-site model validation data. The obtained results and developed methods are likely to be relevant for the scientific community of glaciologists and hydrologists, and to communities, decision-makers, water-managers and engineers interested on glaciers and water resources in arid and semiarid regions, particularly those in the central regions of Chile and Argentina.
... Images coming from different satellites (ASTER, ALOS, SPOT, Landsat, CBERS) were carefully selected considering the absence of seasonal snow and cloud cover, which greatly varies at different latitudes along the Andes ( Paul and others, 2009) (Fig. 2, Table S1). All ice masses larger than 0.01 km 2 were included in the inventory, this being a standard threshold in most glacier inventories ( Andreassen and others, 2008; Nicholson and others, 2009;others, 2009, 2011;Gardent and others, 2014;RGI Consortium, 2017). Then, based on their superficial characteristics, ice masses were classified into five main operational categories: clean ice, debris-covered ice, glacierets or perennial snowfields, rock glaciers (active and inactive), and debris-covered ice with rock glacier. ...
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Glaciers and the periglacial environment in Argentina have been protected by the Law since 2010. This legislation required the development of the first National Glacier Inventory (NGI), which was officially presented in May 2018 and based on satellite images spanning between 2004 and 2016. Here, we present the methods and results of the NGI, summarize the glaciers' morphological and spatial characteristics, and compare our results to previous regional and global inventories. The NGI reveals an impressive variety of ice masses including rock glaciers, permanent snowfields, mountain and valley glaciers with varying amounts of debris-cover and large outlet glaciers. The Argentinean Andes contain 16 078 ice masses covering an area of 5769 km 2 between 200 and 6900 m a.s.l. Comparison of the combined national inventories of Argentina and Chile (∼30 000 glaciers and 28 400 km 2) with the Randolph Glacier Inventory 6.0 for the Southern Andes (∼16 000 glaciers and 29 400 km 2), shows that there are large differences in extent and number of glaciers in some sub-regions. The NGI represents an improvement for a better understanding of Argentina's freshwater reservoirs and provides detailed information for the preservation and study of ice masses along 4000 km of the Southern Andes.
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The Desert Andes contain >4500 ice masses, but only a handful are currently being monitored. We present the mass changes of the small mountain glacier Agua Negra (1 km ² ) and of the rest of glaciers in the Jáchal river basin. Remote-sensing data show Agua Negra glacier lost 23% of its area during 1959–2019. Glaciological measurements during 2014–2021 indicate an average annual mass balance of −0.52 m w.e. a ⁻¹ , with mean winter and summer balances of 0.80 and −1.33 m w.e. a ⁻¹ , respectively. The Equilibrium Line Altitude (ELA) is estimated to be 5100 ± 100 m a.s.l., which corresponds to an Accumulation Area Ratio (AAR) of 0.28 ± 0.21. Geodetic data from SRTM X and Pléiades show a doubling of the loss rate from −0.32 ± 0.03 m w.e. a ⁻¹ in 2000–2013, to −0.66 ± 0.06 m w.e. a ⁻¹ in 2013–2019. Comparatively, the ice losses for the entire Jáchal river basin (25 500 km ² ) derived from ASTER show less negative values, −0.11 ± 16 m w.e. a ⁻¹ for 2000–2012 and −0.23 ± 14 m w.e. a ⁻¹ for 2012–2018. The regional warming trend since 1979 and a recent decline in snow accumulation are probably driving the observed glacier mass balance.
The Andes Cordillera strongly determines Chile’s biophysical conditions. Spanning the entire length of the country, this mountain range’s interaction with the atmosphere dominates regional hydroclimates, from the high-plateau fed groundwater systems in the country’s arid north, through the snow-dominated catchments in the Mediterranean central region, to the temperate rain-forests and glacial environments of Chile’s Patagonia and Tierra del Fuego. This chapter offers an overview of the cryosphere (that is, pertaining to snow and ice) conditions in the country and their influence on hydrological systems. We cover aspects of the Chilean cryosphere’s spatial distribution and temporal variability, physical characteristics and dynamics, and provide an overview of the most recent estimates of projected future conditions under climate change.
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In the semi-arid and arid regions of the Chilean Andes, meltwater from the cryosphere is a key resource for the local economy and population. In this setting, climate change and economic activities foster water scarcity and resource conflicts. The study presents a detailed glacier and rock glacier inventory for the Huasco valley (28-29 • S) in northern Chile based on a multi-temporal remote sensing approach. The results indicate a glacier-covered area of 16.35 ± 3.06 km 2 (n = 167) and, additionally, 50 rock glaciers covering an area of about 8.6 km 2 in 2016. About 81% of the ice-bodies are smaller than 0.1 km 2 , and only four glaciers are larger than 1 km 2. The change analysis reveals a more or less stable period between 1986 and 2000 and a drastic decline in the glacier-covered area by about 35% between 2000 and 2016. The detailed assessment of six subregions indicates a more pronounced glacier decrease in the vicinity of the Pascua Lama mining project.
An abundance of world-class copper deposits in the Atacama region of northern Chile has made Chile the world’s leading copper producer. However, despite extensive exploration activities, the region remains a conundrum, with mature outcropping exploration plays juxtaposed with largely unexplored, extensive areas of post-mineral cover. This scenario offers exciting mineral exploration opportunities in the highly prospective and well-endowed, but locally concealed, metallogenic belts of northern Chile. Conventional exploration of local vast gravel plains or ignimbrite cover in northern Chile are hindered by the ineffectiveness of traditional geochemical techniques in covered settings and the commonly uneconomical costs associated with the systematic use of geophysics and extensive grid drilling. Porphyry deposits of the Atacama region have served as a test case for the use and testing of the effectiveness of hydrogeochemistry and isotopic vectoring in base metal exploration, with a comprehensive set of mineral exploration case studies, including examples of porphyry, epithermal and strata-bound deposits in Chile. Despite previous pilot studies, hydrogeochemistry remains a tool underutilized tool by many explorers, presumably due to a perception that sampling is challenging and laborious, and that data interpretation is intricate and complicated. Here we present a compilation of historical and current case studies to provide an overview of the most likely solute sources and sinks in the hyper-arid Atacama Desert as well as the resulting potential hydrogeochemical signatures that can be expected and their interpretation. The objective of this study is to provide a guide for the interpretation of hydrogeochemical exploration datasets.
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The Andes Cordillera contains the most diverse cryosphere on Earth, including extensive areas covered by seasonal snow, numerous tropical and extratropical glaciers, and many mountain permafrost landforms. Here, we review some recent advances in the study of the main components of the cryosphere in the Andes, and discuss the changes observed in the seasonal snow and permanent ice masses of this region over the past decades. The open access and increasing availability of remote sensing products has produced a substantial improvement in our understanding of the current state and recent changes of the Andean cryosphere, allowing an unprecedented detail in their identification and monitoring at local and regional scales. Analyses of snow cover maps has allowed the identification of seasonal patterns and long term trends in snow accumulation for most of the Andes, with some sectors in central Chile and central-western Argentina showing a clear decline in snowfall and snow persistence since 2010. This recent shortage of mountain snow has caused an extended, severe drought that is unprecedented in the hydrological and climatological records from this region. Together with data from global glacier inventories, detailed inventories at local/regional scales are now also freely available, providing important new information for glaciological, hydrological, and climatological assessments in different sectors of the Andes. Numerous studies largely based on field measurements and/or remote sensing techniques have documented the recent glacier shrinkage throughout the Andes. This observed ice mass loss has put Andean glaciers among the highest contributors to sea level rise per unit area. Other recent studies have focused on rock glaciers, showing that in extensive semi-arid sectors of the Andes these mountain permafrost features contain large reserves of freshwater and may play a crucial role as future climate becomes warmer and drier in this region. Many relevant issues remain to be investigated, however, including an improved estimation of ice volumes at local scales, and detailed assessments of the hydrological significance of the different components of the cryosphere in Andean river basins. The impacts of future climate changes on the Andean cryosphere also need to be studied in more detail, considering the contrasting climatic scenarios projected for each region. The sustained work of various monitoring programs in the different Andean countries is promising and will provide much needed field observations to validate and improve the analyses made from remote sensors and modeling techniques. In this sense, the development of a well-coordinated network of high-elevation hydro-meteorological stations appears as a much needed priority to complement and improve the many glaciological and hydro-climatological assessments that are being conducted across the Andes.
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Glaciers in the dry Chilean Andes provide important ecological services, yet their mass balance response to past and ongoing climate change has been little studied. This study examines the recent (2002–2015), historical (1955–2005), and past (<1900) mass balance history of the high-altitude Guanaco Glacier (29.34°S, >5000 m), using a combination of glaciological, geodetic, and ice core observations. Mass balance has been predominantly negative since 2002. Analysis of mass balance and meteorological data since 2002 suggests that mass balance is currently mostly sensitive to precipitation variations, while low temperatures, aridity and high solar radiation and wind speeds cause large sublimation losses and limited melting. Mass balance reconstructed by geodetic methods shows that Guanaco Glacier has been losing mass since at least 1955, and that mass loss has increased over time until present. An ice core recovered from the deepest part of the glacier in 2008 revealed that the glacier is cold-based with a −5.5°C basal temperature and a warm reversal of the temperature profile above 60-m depth attributed to the recent atmospheric warming trend. Detailed stratigraphic and stable isotope analyses of the upper 20 m of the core revealed seasonal cycles in the δ18O and δ2H records with periods varying between 0.5 and 3 m. w.e. a–1. Deuterium excess values larger than 10‰ suggest limited post-depositional sublimation, while the presence of numerous refrozen ice layers indicate significant summer melt. Tritium concentration in the upper 20 m of the core was very low, while 210Pb was undetected, indicating that the glacier surface in 2008 was at least 100 years old. Taken together, these results suggest that Guanaco Glacier formed under drastically different climate conditions than today, with humid conditions causing high accumulation rates, reduced sublimation and increased melting. Reconstruction of mass balance based on correlations with precipitation and streamflow records show periods of sustained mass gain in the early 20th century and the 1980s, separated by periods of mass loss. The southern migration of the South Pacific Subtropical High over the course of the 20th and 21st centuries is proposed as the main mechanism explaining the progressive precipitation starvation of glaciers in this area.
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A synthesis of glaciological research carried out in Chile during the last decades is presented, including existing inventories, mass balance and glacier variations, which are related to the regional climate change. In Chile, almost 100 glaciers have been measured in terms of their historical frontal variations. They represent 5,6% of the total inventoried glaciers of the country. Only 6% of the inventoried glaciers show a net advance during the study penod, especially glaciar Pio XI with an average of 206 m a-1 between 1945-1997. A 7 % of the studied glaciers show no significant change, while 87% show a negative rate of variation, ranging from a few meters per year to a maximum of 278 m a-1 at glaciar Amalia for the period 1945-1986. Although there are some glaciers with variations related to non-climatic effects, most of the glacier variations are driven by the temperature increase which has been detected in several stations of Chile. Some of these stations show a doubling of the warming rate during the last three decades compared to the secular trend. Anomalies of rainfall and the decreasing trend in the annual precipitation shown in a few stations, have also affected significantly the glacier variations. Finally, the higher frequency of El Nino/Southern Oscillation phenomena (ENSO), has had a significant influence on the inter-annual variability of the precipitation and temperature, with a contrasting response of glaciers at a regional level. Based on observed climatic trends, it is expected that the glacier retreat will continue, the mass balance will maintain negative trends and the thinning rates will increase, affecting the availability of water resources of the country in the future.
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In November of 1999, four permanent surface stations were installed in the vicinity of the surface ozone monitoring station on the summit of the Cerro Tololo (2200 m MSL) in Chile at 30°S. These stations were used to study the atmospheric flow conditions, which are important for the interpretation of the ozone measurements at Cerro Tololo. In addition, radiosonde ascents were performed in March of 2000 near the coast and about 60 km inland. Different wind regimes were distinguished. Above 4 km MSL, large-scale westerly winds prevailed, while northerly winds were observed in a band along the coastline between 2- and 4-km-MSL height. The upper boundary of the northerly wind regime corresponded to the mean height of the Andes mountain range. This wind regime resulted from the westerly winds being blocked and forced to flow in parallel to the Andes (when Froude number is less than 1). The phenomenon was also confirmed by model simulations. Seasonally varying, thermally induced valley winds and a sea breeze developed below the northerly wind regime. In summer, the valley winds reached the Cerro Tololo. Diurnal variation of the top boundary of the valley winds also influenced the lower boundary of the northerly wind regime, which was less than 2 km MSL during the night and greater than 2 km MSL during the day. Thus, this observational and modeling study has shown that in summer the baseline ozone monitoring site at Cerro Tololo can be contaminated by polluted air that is transported from the plains by the thermally induced wind systems.
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A synthesis of glaciological studies carried out in Chile during recent decades is presented, including inventories and records of glacier variations, fluctuations of which are related to regional climate change and their contribution to eustatic sea-level rise. Based upon satellite imagery, aerial photographs and historical records, new data for 20 glaciers are presented. These new data are combined with previous records to cover the historical variations of 95 Chilean glaciers. Of these glaciers, only 6% show a net advance during the study period, 6% show no significant change, while 88% have retreated. The contribution of Chilean glaciers to eustatic sea-level rise has been estimated to be approximately 8.2% of the worldwide contribution of small glaciers on Earth during the last 51 years. Most of the glacier variations are thought to have been driven by a temperature increase, which has been documented by several stations in Chile. Anomalies in rainfall, and the decreasing trend in annual precipitation shown at a few stations, have probably also contributed to glacier recession. Based on observed climatic trends, it is expected that the glacier retreat will continue, that the mass balance will continue to show a negative trend and that thinning rates will increase. All of these changes will ultimately affect the availability of water resources in Chile that depend on glacierized basins.
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An overall retreat of glaciers has been observed in the Andes of central Chile during the last ~100 years. Precipitation is mainly of frontal origin and concentrates in winter months. Analysis of precipitation data shows a decrease until 1976, an increase thereafter north of 34°S and a decrease south of 34°S, but overall no significant trends during the last quarter of the 20th century. Analysis of radiosonde data of central Chile shows mid-tropospheric warming with an elevation increase of the 0°C isotherm of 122 ± 8 m and 200 ± 6 m in winter and summer, respectively, during the 27-year period between 1975 and 2001. The results point to a snowline elevation increase in the region during the last quarter of the 20th century and a concurrent rise of the equilibrium line altitude (ELA) and suggest that mid-troposphere warming is the main cause for glacier retreat in central Chile.
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1] The water resources of high-altitude areas of Chile's semiarid Norte Chico region (26–32°S) are studied using surface hydrological observations (from 59 rain gauges and 38 hydrological stations), remotely sensed data, and output from atmospheric prediction models. At high elevations, the observed discharge is very high in comparison with precipitation. Runoff coefficients exceed 100% in many of the highest watersheds. A glacier inventory performed with aerial photographs and ASTER images was combined with information from past studies, suggesting that glacier retreat could contribute between 5% and 10% of the discharge at 3000 m in the most glacierized catchment of the region. Snow extent was studied using MOD10A2 data. Results show that snow is present during 4 months at above 3000 m, suggesting that snow processes are crucial. The mean annual sublimation ($80 mm a À1 at 4000 m) was estimated from the regional circulation model (WRF) and data from past studies. Finally, spatial distribution of precipitation was derived from available surface data and the global forecast system (GFS) atmospheric prediction model. Results suggest that annual precipitation is three to five times higher near the peak of the Andes than in the lowlands to the west. The GFS model suggests that daily precipitation rates in the mountains are similar to those in the coastal region, but precipitation events are more frequent and tend to last longer. Underestimation of summer precipitation may also explain part of the excess in discharge. Simple calculations show that consideration of GFS precipitation distributions, sublimation, and glacier melt leads to a better hydrological balance.
In February 1999 a 36 m ice core reaching bedrock of the cerro Tapado summit glacier (5550 m, 30°08′ S, 69°55′ W) was recovered in order to investigate the suitability of this glacier as paleoenvironmental and climate archive. Site selection was based on the assumption that this area is strongly influenced by the El Niño phenomenon. Glaciochemical data indicate that a record of about 100 years is contained in the ice core and that El Niño periods are characterized by low concentrations of chemical species.
Rock glaciers in the Andes of Santiago de Chile occupy c. 10% of the total land surface between 3500 and 4250 m ASL. An estimated water equivalent of 0.3 km3 per 1000 km2 of mountain area is stored within them; this value is one order of magnitude higher than in the Swiss Alps. Climate data indicate that the lowest occurrences of active rock glaciers in the Andes of Santiago are not in equilibrium with modern climate. Relict features are found as low as at 2630 m ASL, implying a depression of the mean annual air temperature of at least c. 5.5°C. South of Santiago, active rock glacier distribution ends at 35° 15′S due to lower topography, young volcanism and increased humidity. Copyright © 2005 John Wiley & Sons, Ltd.