South American Glaciers In Historic Retreat

Jay Owen Earth Systems Science

Study: South American Glaciers In Historic Retreat

By Jeff Spross on, Jan 24, 2013 at 5:04 pm

One of the more dramatic effects of global warming is shrinking glaciers around the globe. 10 to 20 percent of glacier ice in the European Alps, for example, has been lost in less than two decades, and half the volume of the mountain range’s glacier ice has melted away since 1850.

Thinning and melting rates in Alaskan glaciers more than doubled over the last decade, African glaciers have declined by 60 to 70 percent since the 1900s, and most Pacific glaciers are also receding. Summer ice coverage in the Arctic could disappear entirely within a decade, and Glacier National Park may not have any glaciers by 2030.

This isn’t just destructive to wildlife and ecosystems. Given their locations, glaciers can serve as crucial supplies of fresh water for various human populations — and as they shrink year after year, those supplies tighten.

The latest example comes from a new report by The Cryosphere, which documents the shrinkage of glaciers in the Andes mountain range of South America. The glaciers have shrunk by at least a third, and possibly as much as half, since the 1970s alone. And the worst loss has been seen in the smaller, lower altitude glaciers which supply fresh water for many of the continent’s residents, according to a round-up of the report by Reuters:

Climate change has shrunk Andean glaciers between 30 and 50% since the 1970s and could melt many of them away altogether in coming years, according to a study published on Tuesday in the journal Cryosphere.

Andean glaciers, a vital source of fresh water for tens of millions of South Americans, are retreating at their fastest rates in more than 300 years, according to the most comprehensive review of Andean ice loss so far.

The study included data on about half of all Andean glaciers in South America, and blamed the ice loss on an average temperature rise of 0.7 degree Celsius over the past 70 years. […]

The researchers also warned that future warming could totally wipe out the smaller glaciers found at lower altitudes that store and release fresh water for downstream communities.

The plot above tracks the changes in surface area for the various glaciers in the Andes since the Little Ice Age in the mid-17th to early-18th centuries. The measurements prior to 1940 were put together from studies of debris associated with the glaciers, and reconstructed from aerial photographs after that point. The drop-off in the second half of the 20th Century is precipitous.

The Zongo Glacier (the red squares) managed to avoid the dramatic shrinkage of the other glaciers because it sits at a higher altitude. The lower altitude glaciers are more vulnerable to temperature shifts, and thus have seen the worst of the melting. They’re also the glaciers that supply fresh water for both the agriculture and consumption of large populations in the arid regions of Peru and Bolivia, serving as a buffer for those communities during the dry season from May/June to August/September.

As the glaciers recede, that buffer shrinks, leaving those water supplies ever more strained. Meanwhile, the tendency of global warming to drive more extreme weather patterns could exacerbate the severity of the dry season, dealing a double blow to the people of Peru and Bolivia.