Remote Sensing of Environment 102 (2006) 24 – 32
www.elsevier.com/locate/rse
Changes in glacier extent in the eastern Pamir, Central Asia, determined from
historical data and ASTER imagery
T.E. Khromova a , G.B. Osipova a , D.G. Tsvetkov a , M.B. Dyurgerov b , R.G. Barry c,⁎
a
b
Institute of Geography, Russian Academy of Sciences, Moscow 109017, Russia
Institute for Arctic and Alpine Research, University of Colorado, Boulder, CO, 80309-0450, United States
c
National Snow and Ice Data Center, University of Colorado, Boulder, CO, 80309-0449, United States
Received 15 March 2005; received in revised form 17 January 2006; accepted 18 January 2006
Abstract
Historical surveys and recent satellite imagery are used to map and assess glacier recession in the eastern Pamir over the last three decades. For
this study we used topographic maps of 1 : 100 000 scales published in 1943 and 1970; air photos from 1978 and 1990; space images: from
Russian satellites in 1972, 1978, 1980, and 1990 and ASTER data for 2001. Climatic records from the “Fedtchenko” glacier station (4156 m a.s.l.,
38.83°N, 72.22°E) and “Murgab” meteorological station (3576 m a.s.l., 38.17°N, 73.97°E) are used for analysis of the climate conditions in the
region.
Changes in the area of 5 glaciers and terminus positions of 44 glaciers in the eastern Pamir reveal an accelerating trend since the end of
the 1970s through 2001, as a continuation of glacier wastage and retreat since, at least, the end of the Little Ice Age. The glacier area
decreased 7.8% during 1978–1990, and 11.6% in 1990–2001. This corresponds with documented changes in other mountain and subpolar
regions in the Northern Hemisphere and specifically in Central Asia. Glacier changes in the eastern Pamir are a response to increasing
summer temperatures. We find decreases in glacier area and retreat of glacier fronts, increased debris-covered area and the appearance of
new lakes.
© 2006 Elsevier Inc. All rights reserved.
Keywords: Glacier extent; Pamir, Central Asia; ASTER imagery
1. Introduction
Recent evidence suggests an acceleration of glacier mass loss
in several key mountain regions (Dyurgerov, 2005). On the
territory of the former Soviet Union (fSU), for example, glaciers
are retreating in all mountain regions. A more comprehensive
evaluation of glacier changes is imperative to assess ice melt
contributions to global sea level rise and the future of water
resources from glacierized basins. The World Glacier Inventory
now documents about 44% of the world's estimated 160,000
glaciers, but an immense task remains in order to complete and
update the inventory entries. The recent availability of highresolution Landsat-7 ETM+ and ASTER images, together with
new digital inventories of glaciers in the fSU and China, in
⁎ Corresponding author.
E-mail address: [email protected] (R.G. Barry).
0034-4257/$ - see front matter © 2006 Elsevier Inc. All rights reserved.
doi:10.1016/j.rse.2006.01.019
combination with GIS techniques, affords one avenue to a
practical solution of these challenges.
The task of creating a new modern glacier inventory based
on space data (ASTER and Landsat images) covering all glacier
regions of the world, is being addressed through the Global
Land Ice Measurement from Space (GLIMS) project supported
by NASA and the US Geological Survey (http://www.glims.
org/). The project is using these and other imagery and field
survey data to map many of the world's glacierized areas and to
assess changes in ice extent (Kieffer et al., 2000; Bishop et al.,
2004).
Initial results have been obtained from analysis of images for
some regions of the fSU, including the Caucasus, Kamchatka,
Tien-Shan (Khromova et al., 2003; Kuzmichenok et al., 2004)
and Russian Arctic (Glazovsky, 2003). The changes involve: a
decrease in average size and volume of glaciers, glacier
terminus retreat, the appearance of new glaciers after separation,
T.E. Khromova et al. / Remote Sensing of Environment 102 (2006) 24–32
25
Fig. 1. Location map of the Pamirs and the study region and outline of ASTER scene, 28 September 2001.
the disappearance of former small glaciers, and moraine
development on the glacier surface etc.
Here we present the first results of an examination of
changes in glacier size in another key region of Central Asia.
Historical data (topographic maps, space images from the fSU
satellites and old airphotographs) are available for comparison
with an ASTER image in order to estimate changes in some
glaciers in the Saukdara Range and the Zulumart Range in the
eastern Pamir (see Fig. 1).
2. Geographical setting
The Pamir forms part of the extensive high mountain system
of Central Asia, comprising the Pamir–Karakoram–Hindu–
Kush ranges with a glacier area of about 40 × 103 km2. The
entire system is characterized by similar topography: high
peaks, steep slopes and deep narrow valleys. The Saukdara and
Zulumart Ranges are located in the high-mountain plateau of
the eastern part of the Pamir (∼38°N, 72°E). The Saukdara
Range rises to about 6000 m a.s.l., with the highest peak
6065 m. The Zulumart Range reaches 5500 m a.s.l. with the
highest peak 5925 m. The regional climate is dominated in
winter by air masses originating in the Atlantic–Mediterranean
region while in summer the South Asian monsoon has a weak
influence.
The climate is typical for Central Asia high-mountain
regions, dry and cold. Annual precipitation at the plateau
level of the Pamir is about 100 mm with a maximum in May–
June (Getker, 1985). The annual air temperature is about − 3 °C;
− 18 °C in winter and 5–8 °C in summer (June–August) based
on data from the nearest meteorological station “Kara-Kul”
(3930 m a.s.l) (Hydrometeorological Service, USSR, 1969).
Other meteorological stations with a longer period of measure-
ments are situated to the west (“Fedtchenko” — 4169 m a.s.l.,
38.83°N, 72.22°E), and to the east (“Murgab” — 3580 m a.s.l.,
38.17°N, 73.97°) of the study area (Fig. 1).
3. Data sources
The first glacier inventory for Pamir was published in 1955
by R. Zabirov. A glacier inventory for the Pamir was published
in the 1960s–1970s as a part of the USSR glacier inventory.
There were about 6700 glaciers in the Pamir. This inventory was
converted into digital format in the 1980s (http://nsidc.org/data/
glacier_inventory/). Also in the 1980s Shchetinnikov made a
new glacier inventory for this region and published results of its
analysis (Shchetinnikov, 1998).
For this study we used topographic maps of 1 : 100 000 scale
published in 1943 and 1970; space images: from Russian
satellites in 1972, 1978 (Fig. 2), 1980, and 1990 (Resurs-F, KFA
1000 camera with 5 m resolution) and from Terra for 2001 (with
15 m resolution ASTER) (Fig. 3). All images are for the end of
the ablation period and have acceptable snow and cloud
conditions (Table 1).
Two climatic records from the “Fedtchenko” glacier station
(4169 m a.s.l.) and “Murgab” meteorological station (3580 m a.
s.l., 38.17°N, 73.97°) have been used for analysis of the climate
conditions in the region (Fig. 1). Mass balance results for Pamir
glaciers are from Dyurgerov (2005).
4. Methods
Deriving glacier outlines from space images is illustrated by
Kieffer et al. (2000), Paul et al. (2004), Kuzmichenok et al.
(2004), and others. The GLIMS project is using remote sensing
data, primarily from the Advanced Space borne Thermal
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T.E. Khromova et al. / Remote Sensing of Environment 102 (2006) 24–32
Fig. 2. KFA-1000 image, 26 September 1978 and an outline of the test area.
Emission and Reflection radiometer (ASTER) carried onboard
the National Aeronautics and Space Administration (NASA)
Terra spacecraft (Raup et al., 2000). GLIMS will maintain a
geospatial database of glacier information derived from the
ASTER sensor. One of the problems is how to combine this
with the large amount of historical data, particularly space
images from the fSU satellites. These images exist only in paper
form and as a rule do not have information which could be used
for automatic transformation and geo-registration. For the data
analysis, a flow chart of processing steps was developed. The
steps include scanning historical maps and images, coregistration, interpretation and digitizing of the glacier outlines.
The ERDAS software package was used for orthorectification and data co-registration.
To generate a DEM from ASTER data we used level L1A
data and the respective parameters provided in the image header
information. Orientation of the 3N and according 3B band from
ground control points, transformation to epipolar geometry,
parallax-matching, and parallax to DEM conversion was
performed. Visual inspection shows that the horizontal accuracy
is 60 m RMSE. Maximum errors within the subset of up to 80 m
occurred at sharp ridges or deep stream channels. Orthorectification of the ASTER image is performed with the ASTER
DEM. The ASTER image has been orthorectified using the
T.E. Khromova et al. / Remote Sensing of Environment 102 (2006) 24–32
27
Fig. 3. ASTER image and an outline of the test area with glacier area change measurements.
ERDAS Orthobase digital photogrammetric package with a
RMSE of 10.8 m for 21 ground control points (GCPs).
The ASTER image was registered to a Gauss–Krüger
projection that was also used for a scanned copy of the
topographic maps. Scanned copies of the KFS images for the
test area have been co-registered to the orthorectified ASTER
image. Thirty-five control points were collected interactively
from display windows to obtain satisfactory RMSE values
(1.35 pixels or 19 m). To determine the locations of GCPs we
selected distinguishable terrain features for both images.
The glacier outlines for each data item were digitized
manually, from the whole 2001 ASTER image (Fig. 3) and for
the test area from KFA-1000 images (Fig. 2). To do the
digitization we used GLIMSView software (see: http://www.
GLIMS.org). In cases of difficulty in distinguishing between
glacier surfaces and thin superimposed ice cover on adjacent
slopes, and to delineate glaciers in problem areas resulting from
snow cover on glaciers, debris-covered termini and shadows,
Table 1
Data sources
Images
Satellite
Sensor
Time
Area
Resolution Measurements
TERRA
Resurs-F
Resurs-F
Resurs-F
Resurs-F
ASTER
KFA 1000
KFA 1000
KFA 1000
KFA 1000
2001-09-28
1990-09-12
1980-09-07
1978-09-26
1972-09-03
60 × 60 km
81 × 81 km
81 × 81 km
63 × 63 km
60 × 60 km
15 m
5m
5m
5m
5m
Area, length
Area, length
Length
Area, length
Length
Topographic maps
Scale
Year
1 : 100 000
1 : 100 000
1970
1943
Fig. 4. Results of interactive visual transformation using visual control points in
ERDAS. The colored lines show the extent of ice for the dates indicated in the
legend.
28
T.E. Khromova et al. / Remote Sensing of Environment 102 (2006) 24–32
Table 2
Glacier area changes for test area (Zulumart range in eastern Pamir)
N
1
2
3
4
5
Total
World Glacier
Inventory ID
Name
SU5X14308307
SU5X14308310
SU5X14308312
SU5X14308313
SU5X14308314
Zulumart
Area km2
Area change %
Area change % per year
1978
1990
2001
78–90
90–01
78–01
78–90
90–01
78–01
25.56
3.37
0.78
1.78
9.83
41.32
23.45
3.1
0.74
1.59
9.23
38.11
21.11
2.47
0.71
1.44
7.97
33.7
− 8.3
− 8.1
− 5.1
− 10.7
− 6.1
− 7.8
−10
−20.3
−4.1
−9.4
−13.7
− 11.6
− 17.5
− 26.7
−9
− 19.1
− 18.9
− 18.4
− 0.7
− 0.7
− 0.4
− 0.9
− 0.5
− 0.7
− 0.9
− 1.8
− 0.4
− 0.8
− 1.3
− 1.1
− 0.7
− 1.2
− 0.4
− 0.8
− 0.8
− 0.8
thermal bands, stereo control, snow free airphotos and the
morphological patterns of the surface were used. Vector files
were exported to the ARC/GIS package.
Polygonal Arc/Info coverages were identified by the World
Glacier Inventory ID for each glacier. We then calculated the
total ice areas for 1978, 1990 and 2001. Topographic maps have
Table 3
Glacier length changes in the eastern Pamir
N
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
World Glacier
Inventory ID
Glacier morphological
type
Glacier
length, km
SU5X14308307
SU5X14308310
SU5X14308314
SU5X14308315
SU5X14308503
SU5X14308514
SU5X14308519
SU5X14308541
SU5X14308543
SU5X14308544
SU5X14308549
SU5X14308551
SU5X14308558
SU5X14308560
SU5X14308567
SU5X14308572
SU5X14308573
SU5X14308578
SU5X14308582
SU5X14308586
SU5X14308588
SU5X14308591
SU5X14308592
SU5X14308593
SU5X14308596
SU5X14308599
SU5X14308600
SU5X14308601
SU5X14308605
SU5X14308612
SU5X14308617
SU5X14308619
SU5X14308622
SU5X14308623
SU5X14317134
SU5X14317136
SU5X14317139
SU5X14317240
SU5X14317241
SU5X14317242
SU5X14317243
SU5X14317245
SU5X14317248
SU5X14317262
Complex valley
Valley
Complex valley
Hanging valley
Complex valley
Complex valley
Hanging valley
Corrie-valley
Valley
Complex valley
Slope
Valley
Valley
Valley
Valley
Hanging valley
Hanging valley
Valley
Valley
Valley
Complex valley
Corrie-valley
Complex valley
Complex valley
Complex valley
Valley
Valley
Valley
Corrie-valley
Hanging valley
Valley
Complex valley
Hanging valley
Complex valley
Valley
Valley
Valley
Valley
Valley
Hanging valley
Valley
Valley
Valley
Valley
11.6
5.2
7.2
2.6
4.3
5.0
1.0
1.7
2.3
2.5
1.5
3.2
2.2
3.6
7.0
1.4
0.6
1.5
3.8
1.1
11.3
2.0
7.6
5.8
6.8
5.0
5.4
5.8
2.8
0.9
1.1
11.4
0.5
4.5
2.8
3.7
4.0
3.8
4.7
3.5
9.3
5.9
2.6
3.3
Glacier length change, m a− 1
1972–1980
1980–1990
1990–2001
− 9.0
− 4.5
− 3.0
− 3.5
− 1.5
− 7.1
0
0
− 1.0
− 2.0
− 2.0
− 2.0
− 4.5
− 3.0
− 8.0
0
0
0
− 3.0
− 4.5
− 18
− 2.3
− 14.0
− 6.0
− 15.0
− 13
− 14.5
− 22.0
− 8.0
0
− 13
− 8.5
−1
− 17
− 1.5
− 4.1
0
− 3.9
0
− 1.5
− 12.5
− 15.0
− 17.5
− 6.0
− 6.8
− 4.0
− 6.0
− 11.0
− 2.7
− 3.0
− 5.0
− 3.5
− 4.0
− 6.5
− 8.0
− 3.0
− 19.5
− 3.0
− 2.0
− 1.5
− 5.0
− 8.0
− 22
− 4.0
− 22.0
− 10.5
− 15.0
− 20
− 24.5
+6.5
− 8.0
− 5.5
−5
− 23.2
−4
− 12
− 2.5
− 3.6
− 1.5
− 5.0
− 19.0
− 5.4
− 23.2
− 8.0
− 3.9
− 8.5
− 19
− 14
− 11
−3
− 6.6
0
−4
− 3.7
− 3.4
− 2.5
− 4.4
0
− 6.6
−6
−9
−7
0
0
−6
− 6.1
− 12
−5
− 14.7
− 23.5
− 16
− 17
− 12
− 10
−8
0
− 6.6
− 13.8
0
− 7.4
0
0
0
− 4.5
0
− 8.6
− 24.5
− 8.6
− 5.4
−9
T.E. Khromova et al. / Remote Sensing of Environment 102 (2006) 24–32
5. Results
Analysis shows that during the last 30 years, glaciers of the
area studied have continued their recession (Fig. 4 and Tables 2
and 3). All the glaciers we studied lost area. The biggest glacier
in the group studied, Zulumart glacier, decreased 17.5% in area
during 1978–2001, 8.3% during 1978–1990 and 10% in 1990–
2001. Glacier area for the region analyzed decreased 7.8% over
the interval 1978–1990 and 11.6% over 1990–2001. A new
lake also appeared in 2001 near the Zulumart glacier terminus.
Fields of thin ice and snow patches, together with glacier
termini, react first to a change in climatic conditions. We
identified such bodies from their locations, field knowledge of
the region, and stereocontrol. Thus, the disappearance of thin
ice and snow patches represents an essential part of the
shrinkage of a glacier system. These results correspond well
with other studies that have been done for different regions of
Asia (Vilesov et al., 2001; Khromova et al., 2003; Kuzmichenok et al., 2004).
The position of glacier fronts for 1943 and 1970 have been
also determined from topomaps. The accuracy of glacier
outlines derived from topomaps is not as good as with
ASTER and KFA-1000 images. However, we could see that
Zulumart glacier had advanced between 1943 and 1970 (Fig. 4).
One of the possible reasons is surging processes. The regime
and distribution of surging glaciers in this region have been
discussed in a special study by Osipova et al. (1998).
The changes in length of 44 glaciers were also determined
for 1972 to 2001 (Table 3).
The glaciers in the eastern Pamir are suitable for such
measurements because most of them have debris-free termini.
Analysis shows that during the last ten years, glaciers of the
eastern Pamir have continued their recession, in common with
most of the world's glaciers (Dyurgerov, 2005; Paul et al.,
2004). But, the rate of this recession slowed in comparison with
the previous decade. For 1972–1980 the mean recession rate
1972-1980
1980-1990
1990-2003
5
0
front position change, meters
been used for GCP selection and co-registration of the data set.
The location of glacier termini has also been determined for
1943 and 1970 using topographic maps. The results are shown
in Fig. 4 and Table 2 for 1978–2001. We have used an ASTER
image and historical data for one compact basin, which includes
glaciers of different morphological types to test this approach.
We also used the independent results of another method, applied
by Osipova and Tsvetkov (2000). This method is based on
measurements of glacier terminus displacements in a stereocomparator using space images for different times. It exploits
the pseudo-stereoscopic effect that is obtained when a
stereogram of two images of the same object, taken from the
same point at different times, is viewed. This pseudostereoscopic effect makes it possible to visualize displacement
of the glacier terminus, observing it in the form of a stereo
model of displacement. Studies of glacier terminus displacement in the eastern Pamir have been made for 1972–2001 using
5-m resolution space images from Russian satellites (1972,
1980, and 1990) and 15-m resolution ASTER data for 2001
(Table 3).
29
Compound Valley,
11 glaciers
Valley,
21 glaciers
7.1
3.9
Other small
12 glaciers
-5
-10
-15
-20
-25
-30
-35
1.7
Average glacier length, km
Fig. 5. Rates of change of glacier length (m a− 1) for three categories of glacier
type for 1972–1980, 1980–1990 and 1990–2003.
was 4.4 m a− 1, for 1980–1991 it increased almost twice to
8.3 m a− 1, while during 1991–2003 it was 6 m a− 1 or 28% less
than in the previous period.
Changes in terminus location estimated for the three periods
are summarized in Fig. 5. Data for 44 glaciers were grouped for
three different glacier types: ‘Compound Valley’, ‘Valley’, and
‘Other small’ ice bodies (including niche or crater cirque, hanging and others), according to IAHS/UNEP/UNESCO (1998).
Average front position changes were calculated and plotted
(Fig. 5). The graph shows that all glaciers have experienced
substantial retreat with different rates by period; also retreat is
greatest for the larger ‘Compound Valley’ glaciers.
6. Discussion of climatic factors
In this study we discuss glacier changes due to regional
climate using observations at two meteorological stations
“Fedtchenko” glacier station (4169 m a.s.l.) and “Murgab”
meteorological station (3576 m a.s.l.). Thus, uncertainty in our
conclusions on climate-related changes in glacier regime may
be substantial. Sharp contrasts in climate between the western
and eastern parts of the Pamir are documented (Kotlyakov et al.,
1993). The two meteorological station records demonstrate this
well. An important difference, relevant to glacier response to the
climate, is the annual cycle of precipitation. At “Fedtchenko”
about 87% of the annual precipitation falls during winter
(October–May), while at “Murgab” winter accounts for only
27% (1970–1990 average values). Thus, air temperatures and
precipitation are coupled differently at these two stations that
are relatively close to one another (about 145 km apart). Fig. 6
shows the temporal changes of the two major variables
responsible for glacier regime and mass balance – surface air
temperature and precipitation – and suggests their likely
contribution to changes in mass balance over the period
1970–1990.
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T.E. Khromova et al. / Remote Sensing of Environment 102 (2006) 24–32
winter precipitation
winter precipitation
summer temperature
summer temperature
2000
6
2
5
1
a)
1600
4
1400
3
summer temp.
1200
2
1000
standardized departures
b)
summer temperature
winter precipitation, mm
1800
0
-1
-2
-3
winter precip
1
800
-4
"Lednik Fedchenko"
"Lednik Fedchenko"
600
1965
1970 1975
1980 1985
summer precipitation
1990
0
1995
-5
1965
1975 1980
1985
14
1
c)
60
12.5
40
12
11.5
20
11
0
10.5
standardized departures
13
average temperature, June-August
precipitation, June-August
d)
13.5
80
0
-1
-2
-3
"Murgab"
-20
1965
1970 1975
1980 1985
1990
1990 1995
summer precipitation
summer temperature
summer temperature
100
1970
"Murgab"
10
1995
year
-4
1965
1970
1975 1980
year
1985
1990 1995
Fig. 6. Changes of surface air temperature (°C) and precipitation (mm) at “Murgab” and “Fedtchenko” meteorological stations; (a) and (c) show actual values for the
Fedtchenko and Murgab, respectively; (b) and (d) show the corresponding standardized values (see text).
Situated near the boundary of winter- versus summerdominated precipitation regimes, the glaciers in the Zulumart,
Saukdara and Belyankeek ranges may respond over time to both
regional climatic conditions and their changes in a complex
way. A full evaluation of the climatic controls may require
special in situ studies of mass balance, or the installation of
Automatic Weather Stations to determine the spatio-temporal
meteorological variability.
The data for “Fedtchenko” show an increase in winter
precipitation (Fig. 6a) and little change in summer precipitation
(OK) Standardized values (∑(Xi − 〈X〉) / s, where Xi = an
individual value, 〈X〉 = mean, and s = standard deviation) of
both variables (Fig. 6b) show that the effect of increasing
summer air temperature (a climatic index of glacier-mass loss)
exceeds that of increases in winter precipitation (a climatic
index of glacier-mass gain) over the entire period, except for a
few years at the beginning and at the end. The change in trends
started in the mid 1970s. Thus glaciers in this more humid part
of the Pamir should be losing mass as increases in winter
precipitation do not compensate for ablation rate increases. The
sensitivity of equilibrium line altitude to a change in the two
variables in the Pamir–Alai mountains is a rise of 120–140 m
for a 1 C summer temperature rise or a 20% decrease in annual
precipitation (Glazyrin et al., 2002). In both regions, with
contrasting summer and winter precipitation dominance, the
trend in glacier length changes is similar. This suggests that the
amount of precipitation and its distribution in time may not be
the major climatic driver. The one common driver, most likely,
was an increase in summer air temperature. The increase in air
temperature in Central Asia corresponds with globally observed
warming over the last few decades (Mann & Jones, 2003).
The “Murgab” data show an increase in both summer
precipitation and summer air temperature and the two variables
are closely coupled as seen in Fig. 6c. Standardized values of
both variables (Fig. 6d) show that summer air temperature has
also dominated over accumulation, as is the case for
“Fedtchenko”. Thus, glaciers in both these regions of the
Pamir should be losing mass because the rise in summer air
T.E. Khromova et al. / Remote Sensing of Environment 102 (2006) 24–32
temperature (climatic index of glacier-mass loss) outweighs the
increased accumulation from winter precipitation (climatic
index of glacier-mass gain) over the entire period, except a
few years at the beginning and at the end.
Mass balance observations carried out over more than
30 years on different glaciers in the Pamir (mostly on the
Abramov Glacier in the relatively humid Pamiro–Alai) show a
strong trend towards mass loss, which has been accelerating
since the 1970s (Fig. 7 and see Dyurgerov, 2005). The available
time series of mass balance data and meteorological data,
accessible in Dyurgerov (2005; also V. Konovalov, personal
communication), correspond well with the results of repeated
surveys of glacier extent acquired by space images. Changes in
climate and negative mass balance may have not immediate
impact on glacier front locations, but the cumulative mass loss
over several decades may have resulted in the glacier recession
observed in these regions. Substantial reduction of surface area
and retreat of glacier fronts has been observed since the 1970s.
This reduction and retreat may represent overlapping responses
to two superimposed climatic events: pre-1970s, generally
warm and dry; and the summer temperature rise and negative
mass balance of the last decade or so. It is hard to distinguish
these two, as the mass balance, which integrates change in air
temperature and precipitation, has been negative for about
30 years, and a steady-state condition was not observed. Given
the established greater sensitivity of Pamir glaciers to summer
temperature rather than to winter precipitation (Glazyrin et al.,
2002), we consider it likely that these reductions in length and
area were due to the observed increases in summer air
temperature. The precipitation in winter (in the humid part of
the region) and in summer (in the driest part) has also shown
increases, but these would not be able to compensate for the
mass loss due to ablation.
sum(bi-<b>)/stdev
meters
4
8
2
-2
4
-4
2
-6
sum(bi-<b>)/stdev
Cumulative mass balance, m
6
0
-8
0
-10
-12
-2
1960 1965 1970 1975 1980 1985 1990 1995 2000
year
Fig. 7. Mass balance trend in the Pamir region plotted as cumulative mass
balance (m w.e.) and as standardized values.
31
7. Concluding remarks
Glaciers are among the most distinctive natural objects for
studying changes from space related to climate. Analysis of
repeated space images has been applied to 44 glaciers in the
Saukdara and the Zulumart Ranges of High-Mountain Central
Asia. These ranges are situated in transitional climatic
conditions between the humid and arid parts of the western
and the eastern Pamir.
Substantial reduction of surface area and retreat of glacier
fronts have been observed since the 1970s. Given the
documented sensitivity of Pamir glaciers to summer temperature (Glazyrin et al., 2002), we consider it likely that these
reductions in length and area were due to increases in summer
air temperature. The precipitation in winter (in the humid part of
the region) and in summer (in the driest part) has also shown
increases, but these would not be able to compensate for the
mass loss due to ablation. The decrease in surface area has been
substantial: 10% over the interval 1978–1990 and 9% over
1990–2001. Glacier termini have also retreated with a variable
annual rate from 11.6 m a− 1 for larger Compound valley
glaciers, to 7.3 m a− 1 for Valley glaciers and 3.3 m a− 1 for
smaller, cirque and hanging glaciers. Area decrease and front
retreat broadly correspond with those observed in other
mountain regions of the world. Hence, glaciers in the Pamir's
climate-transition zone are responding to global warming.
Climatic analysis of changes in ice extent and other environmental phenomena in this region, and elsewhere in Eurasia, is
hampered by the closure of long-term permanent meteorological stations and loss of glacier stations since the breakup of the
fSU. The absence of such data will limit our understanding of
any environmental changes measured from space, the correct
interpretation of the processes involved, and future projections.
This study has been carried out in the framework of the
GLIMS project. Recent satellite data provide a unique
opportunity to look at the world's glaciers. But, in order to
assess glacier changes and understand the role of climate in
these processes, we need to take account of historical
glaciological and climatic data and we also need in situ studies.
The type of study reported here illustrates the application of
historical data and repeated high-resolution space images to
monitor ongoing changes in glacier extent in one of the critical
glacier regions of the world. The results of this study –
continuing glacier recession–correspond well with other studies
performed in different areas of Asia and elsewhere. Accurate
determination of these glacier changes may be useful in
assessing potential regional hydrological responses and water
supply in Asian rivers. Our results show the value of using
historical space images from fSU satellites together with new
data obtained from ASTER under the GLIMS project. We plan
to extend our evaluation of this large, remote, poorly studied
region of Central Asia.
Acknowledgements
Supported through NASA Grant NNG04GM09G for
the GLIMS Core Functions (R.L. Armstrong, Principal
32
T.E. Khromova et al. / Remote Sensing of Environment 102 (2006) 24–32
Investigator). We thank V. M. Konovalov for providing the
climate data.
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