Friday, July 4, 2008
Glacial "moulins" (glacier mills) and climate change
In a recent blog post on Dot Earth, New York Times reporter Andrew C. Revkin gives a "A Tempered View of Greenland's Gushing Drainpipes", writing:
"I have a story on a new [academic] paper tracking the impact over time of those iconic drainpipes for meltwater forming each summer on the warming flanks of the vast Greenland ice sheet. Here’s the nub [of the story]:
One of the most vivid symbols of global warming used by scientists and campaigners to spur society to curb climate-warming emissions is photography of gushing rivers of meltwater plunging from the surface of Greenland's ice sheet into the depths.
Recent studies have shown these natural drainpipes, called moulins, can speed up the slow seaward march of the grinding ice by lubricating the interface with bedrock below."
Question for scientists and laypeople around the world: Why are moulins called moulins? What is the derivation of the word?
Possible answer: As readers know from the name of the famous nightclub in Paris called Le Moulin Rouge -- also a movie starring Nicole Kidman, "moulin" in French means "mill" [as in a mill to grind wheat into flour]. A windmill is called a "moulin a vent" in French, vent being the word for wind.
So "moulin" means mill, usually as an agricultural and culinary term.
However, a moulin, also called "a glacier mill" is a narrow, tubular chute, hole or crevasse through which water enters a glacier from the surface, according to Wikipedia. [They can be up to 10 meters wide and are typically found at a flat area of a glacier in a region of transverse crevasses. Moulins can go all the way to the bottom of the glacier and can be hundreds of meters deep, or may reach the depth of common crevasse formation (about 10-40m) where the stream flows englacially].
Wikipedia adds: "Moulins are a part of a glacier's internal "plumbing" system, to carry meltwater out to wherever it may go. Water from moulins often exits the glacier at base level, but occasionally the lower end of a moulin may be exposed in the face of a glacier or at the edge of a stagnant block of ice. Water from moulins may help lubricate the base of the glacier, affecting glacial motion."
So a glacial moulin is a glacial mill that mills the meltwater from a glacier, so to speak. And now you know the French derivation of the word moulin as it applies to glaciers.