because the
ICESaT
campaign was originally developed to
study polar ice dynamics, therefore, its coverage decreases
as one moves toward the equator. The numbers of footprints
across seasons and years varied significantly in the glaciated
areas in our study region. Some areas covered with a very
large number of footprints, but the others had only a few foot-
prints. However, researchers have successfully used a limited
number of
ICESaT
footprints in non-polar regions such as Tibet
and parts of the Himalayas to study glacial mass balance (
Beaulieu and Clavet, 2009; Gardner
et al.
, 2013; Kääb
et al.
,
2012; Neckel
et al.
, 2014). Highly accurate measurement of
elevation in
ICESaT
campaign makes it suitable for mass bal-
ance study at a regional or a sub-regional level. Our study is
the first attempt to use
GLAS
/
ICESaT
data over clean ice in the
Southern Andes. We used only the dry season footprints on
clean ice areas of the glaciers in the analysis.
Generally, in all regions and all the years, the elevation val-
ues were lower than the elevation values from the year 2000,
with some annual fluctuations especially in the
NW
region.
But the elevation trends fitted through all data points have
been always negative (Figure 4 and Figure 5). Therefore, it is
evident that there was a negative mass balance in the region.
Several other studies in the region using various remote sens-
ing satellite data also have indicated glacial retreat and mass
balance decline (Chen
et al.
, 2007; Dixon and Ambinakudige,
2015; Lopez
et al.
, 2010; Masiokas
et al.
, 2009; Mouginot and
Rignot, 2015; Rignot
et al.
, 2003; Rivera
et al.
, 2006; Sakaki-
bara and Sugiyama 2014).
The mass balance of glaciers were significantly negative
in the
CDI
and
NW
regions. The uncertainty in the estimation
of mass balance is very low in the
CDI
ad
NW
. However, in
SPI
and
DC
regions, negative trends were not very significant as
the uncertainties in our estimation of elevation differences are
higher than the elevation differences. In the
CDI
region, glacial
mass balance was −0.126 ±0.05 m w.e.a
-1
. Lopez
et al.
(2010)
studied 25 glaciers in
CDI
and found 20 glaciers retreating and
five glaciers remaining stationary between 1945 and 2005. A
recent study by Melkonian
et al.
(2013) used
ASTER
and STRM
DEM
s to record an average glacier thinning rate of −1.5 ±0.6
m w.e.a
-1
in the
CDI
region. Overall, it evident from our study
and other studies that the Cordillera Darwin Icefield is losing
mass more rapidly than other regions in the Southern Andes.
In the
NW
region, glacial mass balance was −0.122 ±0.12 m
w.e.a
-1
. Rivera
et al.
, (2006) and Rivera and Bown (2013) stud-
ied the glacial retreat in this region and observed significant
negative trends. Our study reiterated these observations even
though uncertainties in our estimations. Rivera
et al.
, (2006)
and Rivera and Bown (2013) related these negative trends to
trophospheric warming and reduced precipitation.
In Dry Central, we observed gradual but continuous mass
loss at the rate of −0.037 ±0.13 m w.e.a
-1
. Previously in this re-
gion, Rivera
et al.
(2006) also found a negative mass balance of
−1.06 ±0.45 m a
-1
in the Cipreses glacier between 1955 to 2000.
Similarly, our results in the
SPI
region reveal steady glacier
mass balance rates of −0.037 ±0.05 m w.e.a
-1
. Considering the
uncertainties, our results are comparable to the observations
made by Willis
et al.
(2012) in this region where they found
−24.4 ±1.4 Gt a
-1
loss in the mass between 2000 and 2012.
One possible reason for the negative mass balance in the
region is the increased temperature in South America over the
twentieth century, as reported by Carrasco
et al.
(2005), Favier
et al.
(2009), Rabatel
et al.
(2011), and Villalba
et al.
(2003).
Similarly, there might be other climatic factors responsible for
glacial melting and variation in the snow accumulation, like
a fluctuation in the precipitation, as suggested by Favier
et
al.
(2009), Prieto
et al.
(2001), and Rignot
et al.
(2003). More
research is required to understand the role of micro-climatic
conditions on glacial variations in the region. It is also
important to understand the effects of
ENSO
events on Central
Andean glaciers (Carrasco
et al.
, 2005; Prieto
et al.
, 2001,
Rivera
et al.
, 2006; Rivera and Bown, 2013). However, the
lack of good quality climatic data in glacier regions (Masiokas
et al.
, 2009) prevented such analysis. This study attempts to
use limited data to study the status of glacial change in a large
area, but further studies are still required.
References
Ambinakudige, S., 2010. A study of the Gangotri glacier retreat in the
Himalayas using Landsat satellite images,
International Journal
of Geoinformatics
, 6(3):7–12.
Ambinakudige, S., 2014. Glaciers,
Oxford Bibliographies in
Geography
(B. Warf, editor), Oxford University Press, New York.
Ambinakudige, S., and K. Joshi, 2015. Multi-decadal changes in glacial
parameters of the Fedchenko Glacier in Tajikistan,
International
Journal of Advanced Remote Sensing and GIS
, 4(1):911.
Ambinakudige, S., and K. Joshi, 2012. Remote sensing of cryosphere,
Remote Sensing Applications
(B. Escalante-Ramirez, editor),
InTech, pp. 369–380.
Aniya, M., H. Sato, R. Naruse, P. Skvarca, and G. Casassa, 1996. The
use of satellite and airborne imagery to inventory outlet glaciers of
the Southern Patagonia Icefield, South America,
Photogrammetric
Engineering & Remote Sensing
, 62(12):1361–1369.
Bamber, J.L.,and A. Rivera, 2007. A review of remote sensing methods
for glacier mass balance determination,
Global and Planetary
Change
, 59(1):138–148.
Beaulieu, A., and D. Clavet, 2009. Accuracy assessment of
Canadian digital elevation data using ICESat,
Photogrammetric
Engineering & Remote Sensing
, 75(1):81–86.
Bolch, T., M. Buchroithner, T. Pieczonka, and A. Kunert, 2008.
Planimetric and volumetric glacier changes in the Khumbu
Himal, Nepal since 1962 using Corona, Landsat TM and ASTER
data,
Journal of Glaciology
, 54(187):592–600.
Carrasco, J.F., G. Casassa, and J. Quintana, 2005. Changes of the 0°C
isotherm and the equilibrium line altitude in central Chile
during the last quarter of the 20
th
Century / Changements de
l’isotherme 0
°
C et de la ligne d’équilibre des neiges dans le Chili
central durant le dernier quart du 20ème siècle,
Hydrological
Sciences Journal
, 50(6):37–41.
Carabajal, C.C., and D.J. Harding, 2006. SRTM C-band and ICESat
laser altimetry elevation comparisons as a function of tree cover
and relief,
Photogrammetric Engineering & Remote Sensing
,
72(3):287–298.
Chen, J.L., C.R.Wilson, B.D.Tapley, D.D. Blankenship, and E.R. Ivins,
2007. Patagonia icefield melting observed by Gravity Recovery
and Climate Experiment (GRACE),
Geophysical Research Letters
,
34(22):1–6.
Dixon, L., and S. Ambinakudige, 2015. Remote sensing study of
glacial change in the northern Patagonian icefield,
Advances in
Remote Sensing
, 4(04):270–279.
Dyurgerov, M.B., and M.F. Meier, 1997. Mass balance of mountain
and subpolar glaciers: A new global assessment for 1961-1990,
Arctic and Alpine Research
, 29 (4):379–391.
Espizua, L.E., and P. Pitte, 2009. The Little Ice Age glacier advance in
the Central Andes (33°- 35°S), Argentina,
Palaeogeography,
Palaeoclimatology, Palaeoecology
, 281(3-4):345–350.
Favier, V., M. Falvey, A. Rabatel, E. Praderio, and D. López, 2009.
Interpreting discrepancies between discharge and precipitation
in high-altitude area of chile’s norte chico region (26°-32°S),
Water Resources Research
, 45(2):1–20.
Fountain, A., 2011. Temperate Glaciers,
Encyclopedia of Snow, Ice
and Glaciers
( V.Singh, P. Singh, and U. Haritashya, editors),
Springer, The Netherlands, pp. 1145.
Gardner, A.S.,G. Moholdt, J.G. Cogley, B.Wouters, A.A.Arendt,
J. Wahr, E. Berthier, R. Hock, W.T. Pfeffer, G. Kaser, S.R.M.
Ligtenberg, T. Bolch, M.J. Sharp, J.O. Hagen, M.R.van den Broeke,
and F. Paul, 2013. A reconciled estimate of glacier contributions
to sea level rise: 2003 to 2009,
Science
, 340(6134):852–7.
PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
October 2016
817
