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)
A glacial melting feedback loop
As you descend from the top of a mountain, the air temperature will normally increase. Now, some alpine glaciers are 1,500 metres thick, and some Greenland glaciers are 3,000 metres thick. So, as these glaciers melt and the glacial surfaces drop, there are increases in the average air temperatures at the glacier surface.
|Melting of the glacier||———->||A drop in the altitude of the glacier surface|
|*||<———-||A rise in average 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.
- 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.
Updated 10 Nov 2019