Southern Patagonian Icefield

At the tip of South America between 48° 20' and 51° 30' south latitude , the Andes occurs almost completely covered by a large body of ice called Southern Patagonian Icefield (SPI) , the largest in the Southern Hemisphere after Antarctica, with an area of ??13000 km² , and a length of 350 km ( Aniya et al. 1996).


The SPI is a mass of ice with character of plateau an average altitude of 1350 m.a.s.l. , which is interrupted by numerous peaks and mountain ranges with elevations up to 3600 m.a.s.l. , which generate 48 basins main glaciers (Figure 1), from the which great tongues of ice break off , most of which in the West side manage to reach sea level on the eastern slope , reach the large Patagonian lakes.


Paso Cuatro glaciares


Of the 48 glaciers basins major of the SPI , most have presented a severe recession in recent years , with retreat rates even exceed 100 m/y between 1945-1986 for O'Higgins, Amalia, Upsala and Lucia glaciers (Aniya et al. 1997).



A few glaciers SPI presented stability in their foreheads and even three have advanced , the glacier Perito Moreno ( Rott et al. 1998), Trinidad ( during the last visit of the authors in March 2000 , it was found that was destroying forests in the bottom of the fjord Exmouth ) and especially Pío XI glacier, which had a rate of advance of 206 m/y between 1945 -1995 (Rivera et al. 1997).



In PSI there is a significant loss of surface ice , estimated at ca. 500 sq km between 1945 and 1986 ( Aniya , 1999). Along with the above , it has been estimated a significant volume loss due to changes in thickness , thinning rates variable , with a maximum of 14 m / a between 1991 and 1993 for Upsala ( Naruse et al. 1997) glacier.



Recent changes in the glaciers of SPI are a clear response to observed climate changes in the southern part of the continent , characterized by an increase in temperature ( Rosemblüth et al. 1997 ) and the decrease in rainfall observed at several stations ( Rosemblüth et al . 1995).



Notwithstanding the foregoing , the specific responses of glaciers to climate change are not linear, but depend on the topographic features of the glacial basins ( hypsometry , earrings , geometry of the valley, thickness of ice, moraine material on the surface of ice) and glaciodynamics characteristics ( speed, flow, calving, surges, etc. ).


Nunatak Viedma Glacier 1998


Due to the great biodiversity of flora and fauna, as well as the scarce human intervention at the margins of SPI, this area has been designated as area protected by the governments of Chile and Argentina.


In 1959 , the Chilean government declared a southern portion of the SPI and its environment not glacier like the Parque Nacional Torres del Paine, which have an approximate area of ??181,000 ha and has been declared by UNESCO Biosphere Reserve. In Chilean territory, the rest of SPI were declared national park in 1969 , becoming the Bernardo O'Higgins Park; the largest nature reserve in Chile with 3,525,901 ha.


In the same perspective, the entire portion of the HPS located in the Republic of Argentina, is inserted into the Parque Nacional Los Glaciares with 450,000 ha, which is considered among the 25 mountain regions with exceptional significance for science and conservation, by which it is defined as World Heritage Site according to IUCN.


Despite its binational character and status of protection, the SPI is one of the least studied areas are glaciated planet.


Changes temperatures in Southern Icefield

Time series of seasonal 850-hPa temperature at 50°S, 75°W. Best-fitting piecewise-constant functions have stages 1948–56, 1957–77, 1978–83, and 1984–99 for summer (Jan, Feb, Mar) and 1948–56, 1957–77, 1978–93, 1994–99 for winter (Jul, Aug, Sep). The rms is 0.6°C for each season. The best-fitting constant in a stage is the mean of the values in that stage. Times of discontinuities between stages are determined empirically to give the best fit overall, subject to the constraint that no stage can be less than five years long. (Rasmussen L.A et al, 2007)


Rainfall in the Southern Icefield

Annual precipitation on both sides of SPI


Fuente: Rivera, 2004



Density profile temperature in the borehole


Density profile (blue), temperature (red) in the borehole at Pío XI glacier, and melt percent (black). The melt percent represents averages over 1 m depth. Green dashed lines show densities simulated with an empirical model of firn densification in the dry firn zone (Herron and Langway, 1980), using a firn temperature of -1ºC and an annual accumulation rate of 7.1 m weq (left curve) and 3.4 m weq (right curve), respectively. (Schwikowski, M et al, 2013)


Net accumulation m weq

Glacier Reference Altitude m/y
Gorra Blanca Norte (Schwikosky et al, 2006) 2300 0.97
Perito Moreno (Aristarain & Delmas, 1993) 2680 1.2
Tyndall (Shiraiwa et al, 2002) 1756 14.4
Chico (Rivera et al, 2006) 1440 0.57
Pío XI (Schwikosky et al, 2013) 2600 5.8


Areal changes in SPI

(Source: Figure extracted from Glasser et al, 2011)


Areal changes 1945-1986: (13,500 - 13,000) 12 km²/y
Areal changes 1986-2009: (13,000 - 12,500) 22 km²/y
Retreats until hundreds of m/y
(Sources: Glasser et al, 2011; Lliboutry 1956, Aniya et al, 1997, Skvarca 2009)


Thinnings in SPI


Surface elevation change rates (dh/dt) for the Southern Patagonian Ice Field between 2000 and 2012. Glacier boundaries in black. Grey pixels indicate no data. Thinning is common around the periphery, extending to high elevations at several locations.
(Source: Willis et al, 2012)




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Casassa, G., Brecher, H., Rivera, A. & Aniya, M. (1997): A Century-long Record of Glaciar O'Higgins, Patagonia. Annals of Glaciology, 24:106-110.


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Rosenblüth, B.; Casassa,G.; Fuenzalida, H. 1995. Recent climate changes in Western Patagonia. Bulletin of Glacier Research, Vol. 13, p. 127-132.


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Shiraiwa, T.; Kohshima, S.; Uemura, R.; Yoshida, N.; Matoba, S.; Uetake, J and Godoi, M.A. 2002. High net accumulation rates at Campo de Hielo Patagonico South America, revealed by analysis of a 45.97 m long ice core. Annals of Glaciology, Vol. 35, p. 84-90.


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Willis, M.; Melkonian, A.; Pritchard, M. & Rivera A. 2012. "Ice loss from the Southern Patagonian Ice Field, South America, between 2000 and 2012." Geophysical Research Letters. Vol. 39, DOI:10.1029/2012GL053136.