The Andean Glacier and Water Atlas

Shrinking ice

Glaciers form above the snowline and temperature and precipitation play a major role in their formation and maintenance. As outlined in the previous chapter, temperatures in the Andes are increasing and precipitation patterns are changing. While most glaciers around the globe have been shrinking since the end of a cold period at the beginning of the 18th Century, referred to as the Little Ice Age (Vuille et al., 2018; Zemp et al., 2015), the recent rapid retreat of glaciers in the Andes has been linked to anthropogenic climate change (Marzeion et al., 2014). Glaciers are sensitive indicators of climate change as they respond rapidly to temperature and precipitation changes. The rapid retreat of tropical glaciers is considered to be one of the most visible indicators of global warming (Vuille et al., 2008). The amount of glacial retreat varies, but small glaciers are most vulnerable and many in the Andes have already disappeared.

The hydrological response of retreating glaciers is well documented (e.g. Baraer et al., 2012). With continuous retreat, there is a temporary increase in melt runoff, which eventually reaches a maximum, referred to as peak water. This point is followed by ever decreasing annual runoff volumes as the glacier continues to lose mass (Mark and Mckenzie, 2007; Baraer et al., 2012). Downstream, this results in falling river levels and potential drought (if not compensated by increasing precipitation). Peak water occurs earlier in basins with small glaciers and lower ice cover. Most studies suggest peak water for the Andean glaciers has already occurred or will occur during the coming couple of decades (Huss and Hock, 2018; Huss et al., 2017). Glaciers are retreating in every country of the Andes. This is especially pronounced on low altitude small glaciers in the tropical Andes (Rabatel et al., 2013).

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