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.

by Bob Berwyn, via Summit County Citizens Voice

In yet another sign of how quickly global warming is eating away at glaciers in the European Alps, the Austrian Alpine Club is reporting that the summit cross high on the 3,660-meter Grossvenediger in Austria came close to toppling off its podium this summer.

The permanent snow and ice that helped hold the monument in place for decades melted away in the summer heat, with several feet of ice vanishing just in the past few months. A mountain guide arriving at the summit last week discovered that the cross was close to falling over, with potential risks to summit visitors.

A mountain rescue crew and other workers temporarily re-anchored the cross to the remaining ice with steel cables, but later decided to take it down once again. It will be remounted on solid rock.

Austrian media is reporting that, up until very recently, it would have been impossible to use the bare rocks at the summit as an anchor point. The permanent snow and ice that has covered the mountain’s peak for at least a century has just vanished within the past few weeks, according to Friedl Steiner, head of the local rescue group, who attributed the melting to climate change.

The U.S. Geological Survey has documented shrinking and vanishing ice fields in the Rocky Mountains with this extraordinary photo project.

Global warming deniers will try to tell you that glaciers have been melting since the end of the last ice age, but the rate of melting at most glaciers now far exceeds the background rate that could be expected as part of natural climate variations.

Glacier melting has accelerated in the European Alps since 1980, and 10 to 20 percent of glacier ice in the Alps has been lost in less than two decades. Half the volume of Europe’s Alpine glaciers has disappeared since 1850.

Thinning and melting rates in Alaskan glaciers have more than doubled just in the past 10 years.

African glaciers have declined by 60 to 70 percent since the 1900s, and most Pacific glaciers have also declined, with the exception of some of New Zealand’s ice fields, where increased precipitation has helped boost glacier growth.

Bob Berwyn is Editor of the Summit County Citizens Voice. This piece was originally published at the Citizens Voice and was reprinted with permission.

Petermann Glacier has calved another gigantic ice island, larger than twice the size of Manhattan, not quite as large as the calving of two years ago. A study this month found that the melting of the Greenland Ice Sheet is nearing a critical “tipping point.”

by Neven, via the Arctic Sea Ice Blog

This second big calving (spotted this time by Arcticicelost80) is another spectacular event on Greenland, after retreats of the Jakobshavn Glacier and lowest reflectivity of the Greenland ice sheet on record (see blog post), leading to unprecedented flooding in the southwest of Greenland.

From the Icy Seas blog:

This morning Petermann Glacier lost another ice island….

The break-off point has been visible for at least 8 years in MODIS imagery propagating at speeds of 1 km/year towards Nares Strait. The fracture also extended further across the floating ice sheet from the northern towards its southern side.

This event is still evolving, Trudy Wohleben of the Canadian Ice Service noticed it first (as in 2010) after reviewing MODIS imagery. Several people in several countries are monitoring and assessing the situation, but a first estimate of its size is 200 km^2 (3 Manhattans), I will revise this figure as soon as I got my hands on the raw data.

Read more here.

Two years ago Patrick Lockerby was the first to tell the world about the big calving that occurred at Petermann Glacier. The Arctic Sea Ice blog followed suit shortly afterwards. The whole event garnered a lot of attention, popularizing the island of Manhattan as an area measurement tool (metre, kilometre, Manhattan). This second big calving in as many years doesn’t come as a surprise, as attested by this article on the New York Times blog from August last year:

Read more