The South America Glacier:
There are two glaciated areas in South America a) the tropical glaciers in Peru, Bolivia, Ecuador, Colombia and Venezuela, and b) those in Patagonia and Tierra del Fuego (southern Chile and -Argentina). They are subject to very different climatic conditions.
The total area of the South American glaciers was estimated in the mid-1970s to be approximately 25,000 km². About 10% are located in the tropical region. They are there economically very important, especially for water supply.
The tropical glaciers belong mainly to the so-called warm glaciers, that is, their ice temperature is located at the pressure melting point. They react therefore in a relatively short time to temperature change and are quick indicators of climate change.
Throughout the year there are conditions in the tropical Andes that allow ablation. In other regions such as the Alps, the winter months are determined by the accumulation and the summer months by ablation. In the tropical Andes both processes – maximum ablation and maximum accumulation – can take place during the summer.
The reason for this is the fact that the rainfall usually occurs during the summer months, when the insolation is at its maximum. Scientists agree that the tropical glaciers have retreated for 40 years at a rate without precedent during the last three centuries. The main reason lies in global warming; beside that El Niño-Southern Oscillation (ENSO) in the Pacific plays for an important role for short time periods.
According to the climate projection, it can be assumedthat, due a warming of 3-4 °C, most of the tropical glaciers will be gone by 2100. In the southern Andes we can distinguish four glaciated areas: the northern Patagonian Andes, the North and the South Patagonian ice areas as well as the Cordillera Darwin in Tierra del Fuego. From these, the South Patagonian ice area is by far the largest.
While the tropical glaciers are primarily influenced by the rainfall from the Atlantic, westerly winds bring from the Pacific Ocean the main precipitation to Patagonian and determine the maritime character of the climate in the coastal zone; contrary to that, the eastern side of the Andes is relatively dry.
The Andes are, with few exceptions, below 3,000 m high south of 35 °S .. The mean temperature decreases and heavy rainfall simultaneously cause the formation of large glaciers. They show as well a strong melting in recent decades, however, about 10 years later than in the tropical Andes.
Also for the retreat of glaciers in the southern Andes global warming is seen as the main reason. An additional role can be played by the decreasing precipitation in some cases as can the nature of the surface for calving glaciers.