Which French Alps glacier has a name meaning "Sea of Ice"?

The French Alps glacier whose name means “Sea of Ice” is Mer de Glace. The name is a direct translation of the French phrase for a sea of frozen water, reflecting the glacier’s broad, flowing expanse above the Chamonix Valley.

Mer de Glace lies on the northern slopes of the Mont Blanc massif in France. Strictly measured, the glacier is about 7.5 kilometers long; including its connected tributary ice, the wider glacial system extends roughly 12 kilometers. It forms from the confluence of the Glacier du Tacul and Glacier de Leschaux, with ice supplied from the Vallée Blanche and nearby high snowfields.

The name became established after British travelers William Windham and Richard Pococke explored the area in 1741. A common mix-up is confusing Mer de Glace with the Glacier du Géant or Glacier d’Argentière, which feed or lie near the same Mont Blanc ice world but are distinct glaciers. Mer de Glace has also become a visible symbol of Alpine climate change because its terminus has substantially retreated.