Advancing Glacier

I subscribe to NASA’s image of the day, and I was surprised to see this:

Satellite view of the edge of Hubbard Glacier

Hubbard Glacier

Since measurements began in 1895, Alaska’s Hubbard Glacier has been thickening and steadily advancing into Disenchantment Bay. The advance runs counter to so many thinning and retreating glaciers nearby in Alaska and around the world.

This image, acquired by the Operational Land Imager (OLI) on Landsat 8, shows Hubbard Glacier on July 22, 2014.

According to Leigh Stearns, a glaciologist at the University of Kansas, Hubbard’s advance is due to its large accumulation area; the glacier’s catchment basin extends far into the Saint Elias Mountains. Snow that falls in the basin either melts or flows down to the terminus, causing Hubbard to steadily grow. In addition, Hubbard is building up a large moraine, shoveling sediment, rock, and other debris from Earth’s surface onto the glacier’s leading edge. The moraine at the front gives the glacier stability and allows it to advance more easily because the ice does not need to be as thick to stay grounded. (If it is thin, it can start floating and will not necessarily advance.)

If whether a glacier advances or retreats is so dependent on the surrounding geography, why is glacier retreat always used as an argument for global warming? Isn’t it possible that many glaciers are currently in a state of retreat due to the current erosional state of the surrounding geography?

It’s also interesting to note that retreating glaciers qualify as evidence for global warming, while advancing glaciers don’t seem count as evidence against it.

Either the name Disenchantment Bay is coincidental, or Someone has a sense of humor.