Abstract
Abstract. Pío XI, the largest glacier of the Southern Patagonia Icefield, reached its neoglacial maximum extent in 1994 and is one of the few glaciers in that area which is not retreating. In view of the recent warming it is important to understand glacier responses to climate changes. Due to its remoteness and the harsh conditions in Patagonia, no systematic mass balance studies have been performed. In this study we derived net accumulation rates for the period 2000–2006 from a 50 m (33.2 4 m weq) ice core collected in the accumulation area of Pío XI (2600 m a.s.l., 49°16'40"S, 73°21'14"W). Borehole temperatures indicate near temperate ice, but the average melt percent is only 16 ± 14%. Records of stable isotopes are well preserved and were used for identification of annual layers. Net accumulation rates range from 3.4–7.1 water equivalent (m weq) with an average of 5.8 m weq, comparable to precipitation amounts at the Chilean coast, but not as high as expected for the Icefield. Ice core stable isotope data correlate well with upper air temperatures and may be used as temperature proxy.
Highlights
The Southern Patagonia Icefield (SPI) is the largest ice body of the Southern Hemisphere outside Antarctica with an area of 13 000 km2 and 48 major glaciers (Aniya et al, 1996), many of them calving into fjords and lakes
Jorge Montt and Pío XI glaciers, in spite of both being located at the SPI, are in the very opposite phase of the Tidewater Calving Glacier Cycle (TWG), as the former is probably ending the fastest retreat phase, while the latter is in the steady state phase after an advancing cycle that started in 1944/45 (Rivera et al, 1997a)
This deficiency is due to extremely harsh field conditions with stormy weather and high precipitation rates throughout the year, and to the fact that the low-altitude main plateaus of both the Northern Patagonia Icefield (NPI) and the SPI are strongly influenced by meltwater percolation
Summary
The Southern Patagonia Icefield (SPI) is the largest ice body of the Southern Hemisphere outside Antarctica with an area of 13 000 km and 48 major glaciers (Aniya et al, 1996), many of them calving into fjords and lakes. An accumulation history can be obtained from glacier ice cores, but only few cores with meaningful climatic information have been obtained from Patagonia This deficiency is due to extremely harsh field conditions with stormy weather and high precipitation rates throughout the year, and to the fact that the low-altitude main plateaus of both the Northern Patagonia Icefield (NPI) and the SPI are strongly influenced by meltwater percolation. All three sites are located east of the ice divide of the Icefields, where lower precipitation rates are expected, but there might be net loss by erosion due to the intense winds (Vimeux et al, 2011) In this regard, the upper reaches of Pío XI glacier appear to be an excellent candidate to obtain net accumulation information, because they are located at an altitude where little influence of melting expected, and where wind erosion should not be so critical, since it forms an extended, gently sloping plateau. Lower right: The northern plateau of Cordón Mariano Moreno including topographic information (contour lines) extracted from SRTM
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