Eyjafjallajokull, Iceland’s sixth-largest glacier, gained worldwide recognition when the volcano lurking under it erupted in 2010. Large levels of volcanic ash caused air travel disruptions in Europe, and news reporters across the world struggled with the difficult pronunciation of Eyjafjallajokull, much to the amusement of us native speakers. A less-known and less-tongue-twisting glacier is Ok, which is on a mountaintop in Western Iceland.

But Ok is no longer a glacier.

The ice field that covered the mountain in 1900 — close to six square miles — has now been replaced by a crater lake . It is certainly beautiful, surrounded by patchy snowfields, and is now the highest lake in Iceland . But that beauty quickly fades in the eyes of anyone who knows what was there before and why it is no longer there. Ok’s disappearance is yet another testimony of irreversible global climate change.

On Aug. 18, I will join a group of artists and scientists — along with the former president of Ireland and climate activist Mary Robinson — on a trip to bid farewell to Ok. This trip will include the installation of a memorial shield that reads:

“Ok is the first Icelandic glacier to lose its status as a glacier. In the next 200 years, all our glaciers are expected to follow the same path. This monument is to acknowledge that we know what is happening and what needs to be done. Only you know if we did it.”

This is a local ceremony but a global story.

Glaciers cover 11 percent of Iceland and might be seen as visual thermometers. They have grown and contracted throughout recorded history, most likely reaching their maximum size around 1890, but since then they have gradually retreated, with only short periods of reversals. The process has been particularly fast in the past 20 years. In just a few decades, Iceland may no longer be characterized by the iconic Snaefellsjokull, famously known as the entrance to Earth in Jules Verne’s “Journey to the Center of the Earth.” In short: The ice is leaving Iceland.