Recent glacier variations of the Hielos Patagonicos, South America, and their contribution to sea-level change

Area variations of outlet glaciers of the Hielos Patagonicos (Patagonia icefields), South America, since 1944/45, are summarized, and the volume of ice loss due to recession and thinning estimated, in order to derive the contribution of the Patagonian glaciers to sea-level change. For the Hielo Patagonico Norte (HPN), variations of 22 outlet glaciers were studied for the period between 1944/45 and 1995/96. Until 1990, most glaciers retreated at increasing rates; however, since then, the retreat has slowed down. The total area loss of the HPN due to frontal recession is about 64 km(2). From the estimated ice thickness and thinning rates, a total ice loss of 152-310 km(3) was obtained for the 51 yr. In the Hielo Patagonico Sur (HPS), 48 outlet glaciers were studied for the period between 1944/45 and 1985/86. Most glaciers have been retreating, with a few remaining almost stagnant, but two glaciers, Pio XI and Perito Moreno, showed a net advance. The total area loss of the HPS due to recession was about 200 km(2). From the estimated ice thickness and thinning rates, a total ice loss was 285-670 km(3) for the period of 1945-1986. With a simple linear extrapolation to the period of 1945-1996, figures of 355-833 km(3) were obtained. The total volume reduction of the HPN and HPS is therefore roughly 825 +/- 320 km(3) for the 51-yr period. This amount roughly translates into a world-wide sea-level rise of 1.93 +/- 0.75 mm, or 0.038 mm yr(-1) since 1944/45, which accounts for 3.6% of the total sea-level change. Analyses of climatic data at several Chilean and Argentinean meteorological stations located around the icefield revealed a slight increase in air temperature and a decrease in precipitation over the last 40 to 50 yr. Other factors affecting the variation include calving status, the ratio of the accumulation area to the total area (AAR), the gradient of the glacier surface near the equilibrium line (EL), and subglacial topography.