RIVERA, 1999), Tyndall (CASASSA, 1992: 
RAYMOND, 2005) and O’higgins (KRIMMEL 
1988). 
Estimates indicate that Southern Patagonia 
Icefield will reduce of 38,7+4,4km”/year 
between the years 1975-2000, suggesting an 
acceleration rate of melting quite high. The 
Intergovernmental Panel on Climate Changes 
(2007) showed that the losses accumulated 
since 1960 in Patagonia are approximately 40m 
ice thickness, calculated over the glacier 
(LEMKE et al., 2007). This study aims to 
calculate the surface area of the main glaciers of 
Southern Patagonia Icefield through the 
digitalization of Landsat 7 ETM+ images 
obtained in the years 1973, 1976, 1979, 1986, 
2005 and 2009. 
2. DATA AND METHODOLOGY 
The Southern Patagonia Icefield limited by 
coordinates to 74?10'-73?30'W and 48°20’- 
51°30S is approximately 60km wide, 350km in 
length and a total area of 13.000km?. The 
glaciers studied were selected based on size, 
location and the existence of past studies to 
compare the results. The digitization and 
classification was done from a database of 24 
images of the ETM + sensor aboard the Landsat 
7 satellite, with a spatial resolution of 30m 
and georeferenced in WGS84 datum obtained in 
the years 1973, 1976, 1986, 2005 and 2009. The 
images were acquired in the virtual portals of 
United States Geological Survey (USGS) 
and National Institute for Space Research 
(INPE). 
The methodology was developed with help of 
software ENVI 4.5 ©2008 and  CartaLinx 
1.2© 1999 where Landsat images were 
calibrated to radiance and reflectance for a 
global standardization method. The calibration 
procedures employed in this study were used 
according to Chander and Markham (2003). 
  
Figure 2. Linhas de variaçäo na posiçäo da lingua das 
Geleiras Upsala, Jorge Montt e Tyndall. Geradas a partir 
de imagens Landsat 7 ETM+ para os de 1973-1976-1979- 
1986-2005-2009. 
The digitization of each glacier was made in 
orderto obtainthe limiting position of the 
tongue (Figures 2 and 3), where each image was 
classified individually to avoid overlapping the 
range of pixels. Areas composed of multiple 
regions and pixel border between snow and 
sediment were excluded to avoid overlapping 
values and false classifications. Been generated 
lines of advance indicating the ceiling for each 
glacier for the period analyzed. Researchers 
such as Warren & Sugden (1993) and Aniya et 
al. (1992, 1996) showed that the main glaciers 
of Southern Patagonia Icefield presented until 
the beginning of the decade 90 a general pattern 
of decline and reduced its volume, with 
exception of some glaciers showed a profile of 
frontal accretion and growth. 
  
Figure 3. Linhas de variaçäo na posiçäo da lingua das 
Geleiras Moreno, O'Higgins e Bruggen. Geradas a partir 
de imagens Landsat 7 ETM- para os de 1976-1979-1986- 
2005-2009. 
Jorge Montt Glacier: Located within a fjord on 
the northern edge of the Southern Patagonia 
Icefield has the drainage flow to the north 
   
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