France’s largest glacier once looked so mighty sliding down the granite slopes of the Mont Blanc, Western Europe’s tallest peak, that early explorers struggled to find the words to capture it.
“You must imagine your lake put in agitation by a strong wind, all frozen at once,” wrote British adventurer William Windham, one of the first tourists to explore the glacier in 1741. “Perhaps even that would not produce the same appearance.”
That description gave the place its current name—la Mer de Glace, the Sea of Ice. At that time and until the late 1980s, thousands of years of ice covered the steep valley. Visitors walked from the nearby town of Chamonix to Montenvers, where the glacier was so close they only had to hike down a few metres to touch it.
Today, the Mer de Glace remains the biggest glacier in France, and the second-largest in the Alps. But it’s also become a symbol of the rapid pace of global warming. Mont Blanc is heating up more than twice as fast as the rest of the world. The Mer de Glace has been shrinking since the beginning of the 20th century, but the loss has accelerated over the past two decades. Since 1900, it’s shrunk by about a third of its volume. In total it’s lost around 1.5 cubic kilometers of ice. That’s equivalent to more than half a million Olympic swimming pools of ice.
“Glaciers are symbols of climate change because they’re the elements in nature that react fastest to it,” says French glaciologist Luc Moreau. “Solar radiation, temperature, and greenhouse gases are all invisible things, but measuring glaciers gives us information of all of them.”