The 17 kilometer mountain time trial — the shortest stage the Tour de France has seen — did not give us many opportunities to see some impressive hydrological features. Those that we did see were the impressive glaciers atop the Mont Blanc massif in whose shadow each of the rider set off on his own today. The largest of these is called the Mer de Glace, the “sea of ice.”

The Mer de Glace runs from the northwest side of the Mont Blanc massif into the valley of the Arve river just north of the ski resort. Chamonix (see this Google Earth photo, or have more fun by visiting Mont Blanc in Google Earth yourself. The three-dimensional views they render are pretty spectacular).

As with most glaciers in the world, this one is retreating fairly quickly.

Vincent et al. (2014) estimated the parameters of a model for the mass balance of the Mer de Glace and projected their model into the future, predicting a retreat of 1200 m by 2040.

Chris Froome rode 1200 meters in about a minute this afternoon, crushing the already fantastically impressive time of Tom Dumoulin for the stage win, a preview of the Olympics one can only hope.

• Vincent, C., M. Harter, A. Gilbert, E. Berthier, and D. Six. “Future fluctuations of Mer de Glace, French Alps, assessed using a parameterized model calibrated with past thickness changes.” Annals of Glaciology 55, no. 66 (2014): 15-24.