Glaciers around the world are in retreat. Out of 250 alpine glaciers studied, the Taku Glacier in Alaska was the only glacier not retreating until, in 2019, it too began retreating. 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 average temperature at the glacier surface|
When the “glacier altitude feedback” is dominant:
- more glacial surface melting causes
- the altitude of the glacial surface to drop, causing
- higher temperatures at the glacial surface, which closes the cycle by causing
- more glacial surface melting.
This feedback cycle indirectly increases global temperatures. As the “glacier altitude feedback cycle” decreases the area of reflective glacial ice, the area will absorb more heat from the sun. So, another feedback, the “ice reflection feedback cycle“, will increase global temperatures.
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, or
- the TED talk by James Balog in July 2009.
- Amplifying feedback cycles and climate change
- The mass of Antarctic Ice is decreasing
- The mass of Greenland Ice is decreasing
Updated 28 March 2022