Since roughly 1850, the majority of all glaciers are no longer growing, but melting. Since then, the glaciers of the Alps have lost around a third of their surface – some even more. South America’s most famous glacier, the Perito Moreno, is supposed to be still growing – or at least to be a glacier at equilibrium. Many tourist agencies and travel guides still advertise that it is “one of the last growing glaciers”. According to Wikipedia, “(…) The Glacier is unusual in that it is advancing, while most glaciers worldwide are retreating.” Even some local tour guides refer to it as a stable glacier – but why?


Part of the Southern Patagonian Icefield

The Perito Moreno, named after an Argentine geographer, is located in the Argentine part of Patagonia, in the Province of Santa Cruz. In fact, the glacier is not more than an outlet glacier of the Southern Patagonian Ice Field – Campo de Hielo Patagónico Sur –, which is the world’s second largest ice field except the poles as well as the largest ice field of the Andes. While the Perito Moreno “flows” from the Andes (the Southern Patagonian Ice Field) to the Argentino Lake, it often advances at a meter a day. However, the Magellan Peninsula in Lake Argentino limits the glacier’s advance. Therefore, it is possible to get really close to the calving glacier, generally something impossible or at least very difficult to do.

The glacier advances until it reaches the Peninsula and, therefore, divides the Argentino Lake in two parts: a natural ice dam wall divides “Brazo Rico” and “Brazo Sur”. The ascending water level on one side of the blockade increases the pressure on the ice, so that it finally collapses. The collapse is a spectacular natural phenomenon, which attracts tourists and journalists from all over the world (the last collapse took place recently on March 10th 2016). The glacier advances regularly until it reaches the Peninsula, but does this mean that it is growing?


The big melt

For a long time, scientists and qualified park rangers of the Los Glaciares National Park already knew that global warming does not stop in front of the Perito Moreno glacier. Between 1970 and 2000, the Southern Patagonian Ice Field has lost around 20 billion tons of ice per year and glaciers of this field have thinned by about 1.8 meters annually. In the end, the ice of the Perito Moreno stems from the same ice field. While there is still enough ice to make it advance, the overall volume of the ice field is decreasing.



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