Characteristics of Recent Glacier Variations in Patagonia, Southern Andes

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Glaciological researches were carried out in November and December 1993, at Upsala, Moreno and Tyndall glaciers in the Southern Patagonia Icefield, southern Andes in South America. Outline of the studies accomplished is as follows :1. Measurements of glacier surface heights were made by a triangulation method in the ablation areas of the above three glaciers. By comparing the data obtained in November-December 1990, it was found that Upsala Glacier has thinned from 30 to 45 m and Tyndall Glacier has thinned from 10 to 15 m during the last three years. Whereas Moreno Glacier has been almost in a steady state.2. Distributions and short-term variations of ice flow velocities were measured at Moreno and Upsala glaciers. Velocities fluctuated from 0.4 to 1.2 cm/hour at a point near the margin of Moreno Glacier. Strain rates of glacier surface were also obtained at Moreno and Tyndall glaciers by a strain grid method.3. An aerial survey around the Northern Patagonia Icefield was accomplished in the end of December 1993. Using the oblique aerial photographs taken, variations of frontal positions of about 20 outlet glaciers are analyzed. Most glaciers have retreated considerably.4. Meteorological parameters and ablation rates of ice were observed on the bare-ice of Moreno and Tyndall glaciers during the periods of 15 days in November and 15 days in December 1993, respectively. Characteristics of meteorological conditions and heat balance are discussed.5. Geomorphological research was carried out in the Ameghino Valley, around the terminus of Upsala Glacier and in the eastern area of Tyndall Glacier. Much information of the recent glacier variations was obtained.