Glaciers in retreat:
Glaciers around the world are in retreat. Of the 250 alpine glaciers studied, the Taku Glacier in Alaska was the only one not retreating until, in 2019, it began to do so as well. 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)
The glacier altitude feedback cycle
This feedback occurs because the average temperature at the top of a mountain is lower than at sea level, and this is relevant because we have some thick ice sheets, for example:
- up to 4,900 meters deep in Antarctica,
- up to 3,000 metres in Greenland, &
- up to 1,500 meters for mountain glaciers.
 |  |  |
| More glacial surface melting | A drop in the altitude of the glacier surface | |
 |  | A rise in the average temperature at the glacier surface |
Diagram: The feedback cycle amplifying glacial surface melting
In this amplifying feedback cycle:
- more glacial surface melting tends to cause
- a drop in the altitude of the glacial surface, which tends to cause
- higher temperatures at these lower glacial surfaces, which tends to cause
- more glacial surface melting, and then the cycle repeats.
This feedback cycle indirectly increases global temperatures as it (1) decreases the area of reflective glacial ice, and so (2) increases the absorption of the sun’s energy and (3) warms the planet.
The Extreme Ice Survey
The Extreme Ice Survey collects visual evidence of the impact of global warming on our planet, such as time-lapse photos of glacier contraction. Excluding Antarctica, 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, or
- the TED talk by James Balog in July 2009.
Related pages
- Amplifying feedback cycles and climate change
- The mass of Antarctic Ice is decreasing
- The mass of Greenland Ice is decreasing
Loaded May 2015: Updated 28 March 2022