Glaciers around the world are in retreat. The Taku Glacier in Alaska has been studied since 1946, and only now, in 2019, has it started retreating. Out of 250 alpine glaciers studied, this had been the only one not in retreat. Now there are none. At 1,500 metres thick, it’s one of the world’s thickest mountain glaciers, now retreating by up to 390 billion tons of snow and ice a year.
This is a big deal. Mighty glacier finally succumbs to climate change. (The Age: 8 Nov 2019)
Glacial altitude feedback loops
As you descend from the top of a mountain, the air-temperature normally increases. Now, some alpine glaciers are 1,500 metres thick and some Greenland glaciers are 3,000 metres thick. So, as these glacial surfaces drop, there are significant potential increases in air-temperatures at the glacier surface.
This temperature difference is the basis for a feedback dynamic that can amplify glacial retreat or growth. While this glacial altitude feedback loop is dominant:
- a decrease in the altitude of the glacier’s surface increases the average temperature at the surface of the glacier,
- this increases the melting of snow and ice on the surface,
- this decreases the altitude of the glacier’s surface and closes the feedback loop.
This feedback loop is reversible, as if the glacier’s altitude increases, the average temperatures decrease.
The Extreme Ice Survey
The Extreme Ice Survey collects visual evidence of the impact of global warming on our planet, like time-lapse photos of the contraction of the glaciers. Outside of the Antarctic, 95% of the world’s glaciers are retreating.
See the film “Chasing Ice”, produced in cooperation with National Geographic. It won an Emmy award as an outstanding nature program.
Also a TED talk by James Balog in July 2009
Updated 10 Nov 2019