Patagonian ice sheet
The Patagonian Ice Sheet was a massive ice age ice sheet in the area of the southern Andes , i.e. what is now Chile and western Argentina . In the area of the former ice sheet, the northern Patagonian ice field ( Campo de Hielo Norte ) and the southern Patagonian ice field ( Campo de Hielo Sur ) with a total of around 17,000 km² can be found today . There are other small ice fields in the Cordillera Darwin mountains on Tierra del Fuego .
Emergence
While the tropical glaciers are primarily influenced by precipitation from the Atlantic and react very quickly to temperature fluctuations, the main precipitation in Patagonia comes from westerly winds from the Pacific and shapes the maritime climate on the coast; however, the east side of the Andes is relatively dry. The Andes lose altitude towards the south from 35 ° S and are mostly below 3,000 m. However, the mean temperature decreases significantly to the south, and the heavy rainfall causes the formation of large glaciers.
palaeography
The German geographer Hans Meyer discovered in 1904 the multiphase nature of the glaciation of Patagonia , which was confirmed by Rudolph Hauthal . On the basis of his own geological investigations, he assumed that the ice sheet had the greatest extent during the first phase of glaciation. The Swedish geologist Carl Caldenius (1887–1961) determined the maximum extent of glaciation between 1928–1931 and mapped an area of around one million square kilometers. He also tried to determine the chronology of these movements with the help of the method developed by Gerard De Beer based on the varves , i.e. the sand and ribbon clay layers that form each year when the inland ice retreats from the glaciers, but this turned out to be flawed.
According to more recent findings, the first glaciation occurred 7 to 4.6 million years ago, i.e. roughly at the same time as that of West Antarctica and southern Alaska. A second glaciation occurred about 3.6 million years ago. The third glaciation is the most extensive: its maximum reached the Atlantic coast 1 to 1.2 million years ago at around 69 ° W. According to other sources, the ice sheet stayed about 140 km from the coast in southern Patagonia. To the south it extended to the Beagle Channel . There were also ice islands in the mountains of the province of Buenos Aires.
About 12,000 years ago, most of the ice sheet had melted, in a north-south direction, which shows the corresponding orientation of the great fjords of the Chilean west coast. The remaining glaciers in the southern Andes have been melting heavily since around 1975, which started around 10 years later than in the tropical Andes. Very different trends can be seen locally as a result of the interaction between changes in temperature and rainfall.
present
The remains of the ice sheet are the Campo de Hielo Sur (approx. 13,000 km²) and the smaller Campo de Hielo Norte (approx. 3700 km²). The two largest outlet glaciers of the northern ice field, San Rafael and San Quintín, lost around 14-17% of their area between the end of the 19th century and 2017.
literature
- C. Caldenius: Los glaciaciones cuarternarias en la Patagonia y Tierra del Fuego. In: Geografiska Annaler. 14, Stockholm 1932, pp. 1-164.
Individual evidence
- ↑ Alfonso Fernández Rivera, Andrés Rivera Ibáñez, Cristián Rodrigo Ramírez: Variaciones recientes de glaciares entre 41 ° S y 49 ° S y su relación con los cambios climáticos. In: Revista Geográfica. No. 139, 2006, pp. 39-69.
- ↑ North Patagonian Icefield NASA Earth Observation, 2017 (English).