How Can You Tell When a Glacier Is Dead?

The end of a famous Icelandic glacier is just the beginning.

The former site of Okjökull, now known as simply Ok.
The former site of Okjökull, now known as simply Ok.
Rice University

The unraveling story of climate change is one of loss: shrinking coastlines, fading habitats, disappearing biodiversity. Many of these changes happen subtly and slowly, so the enormous scale of loss is difficult to process in real time. But the final result can be stark. Consider the case of Okjökull, a former glacier in western Iceland. For centuries, it was there. Now it isn’t.

Thanks to a crew of dedicated glaciologists, Iceland has especially extensive records of its glaciers, amounting to more than 80 years of annual measurements. Those records are disheartening. Over the past 20 years, in particular, warmer summers have shrunk and thinned the country’s glaciers. Oddur Sigurðsson, one of the country’s leading glaciologists, declared Okjökull dead in 2014, though it likely expired before then. Jökull is the Icelandic word for glacier or ice cap, and so Okjökull had the jökull part of its name stripped. It’s now known as just Ok.

Rice University anthropologists Cymene Howe and Dominic Boyer both study Icelandic culture and were surprised that the story of Okjökull didn’t catch on beyond Iceland when it happened. “There was just one small news piece in English-language news, and no international coverage,” says Howe. “I was disturbed and intrigued by this story of this little glacier that had been destroyed with little fanfare.” So in 2018, the researchers produced a documentary about the mountain called Not Ok.

In their ethnographic research and in the interviews they conducted for the film, Howe and Boyer noticed that death was a recurring trope. “Toward the end of the process, we realized that Ok deserves some kind of memorial to its passing,” says Howe. “We did some research and saw that there were no monuments to former glaciers anywhere else in the world, and it seemed like an important symbolic and political statement to make about the radically transforming environment around the world.”

So Howe and Boyer put together a proposal to memorialize Okjökull with a plaque. The process took about year and “culminated in a phone call where we had to ask the owner of a part of the mountain whether it would be OK to place this plaque on his property, essentially,” says Howe. In August, the anthropologists, Sigurðsson, and interested members of the public will hike to a point on Ok and affix the plaque to one of its rocks. The inscription was written in Icelandic by author and poet Andri Snær Magnason, and includes a translation into English:

A letter to the future

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 will know if we did it.

August 2019

415 ppm CO2

Ok is the first, but almost certainly not the last—in Iceland, or elsewhere. Iceland has more than 400 glaciers, and, as the plaque says, experts predict they could all disappear by 2200. According to a 2017 paper, the European Alps have lost 54 percent of ice area since 1850, Bolivian glaciers have lost nearly half of their mass in the past 50 years, and glaciers in the Himalayas and Canada are also quickly losing ice. All glaciers in Glacier National Park in Montana have shrunk in area since 1966, and side-by-side shots of their recession are striking. But when does a glacier go from receding to dead?

According to Sigurðsson, he declared Okjökull dead because it had become too thin to qualify as a glacier. “A glacier must be thick enough to move by its own weight,” he says. If a glacier becomes too thin, “the glacier will stop moving and will be declared a dead glacier.” Though Ok is touted as the first Icelandic glacier to lose its designation as a glacier, “there are many cases on the verge of being a glacier or not being a glacier.”

Sigurðsson made the call by photographs he’d taken since 2003, and by sight. “It was far too thin to be able to move,” he said. If checking by sight, there are telltale signs of a moving glacier: crevices, which form as moving ice cracks and fractures, and turbid (or opaque) water beneath the surface of the ice, which is a sign that the glacier is picking up sediment from the rock below.

There are also other methods glaciologists might use to determine the movement (or lack thereof) of a glacier, says Tom Neumann, a cryospheric scientist at NASA’s Goddard Space Flight Center. While the first glaciologists measured movement with old-school methods, like placing a rock on the ice and checking back on it months later, scientists now have fancier methods. Over the past two decades, researchers have used GPS to track the movement of poles drilled into the ice, and now, glaciologists might also use satellite data, which allows them to see the movement of specific features over time, like distinct bands of darker ice. Software can also be automated to track specific shapes or patterns in photographs to get a big-picture view of how a glacier flows over the course of weeks, days, or years.

Neumann says he’s never declared a glacier dead and doesn’t know of anyone in the field who specializes in presiding over glacial death, but he offered up the same definition of a glacier that Sigurðsson did: It forms by snow falling from the sky being compressed over time to form ice, and it must move. He agrees that the ice on Ok looks far too thin to be moving and says that the geometry of the mountain could play a role in its early demise. Ok has a relatively gradual rise, so gravity does very little to help any ice on its surface flow downhill. “On a steeply sloping glacier, the ice has got to get pretty thin before it’ll stop flowing,” he says. That means that small glaciers in relatively flat locations could be more likely to “die” than similarly sized ones on steep slopes: Glaciers on flatter surfaces have less help from gravity to move them downhill.

And those smaller glaciers are certainly dying as well, according to Sigurðsson. Though Okjökull is the first well-known glacier to lose its status, Sigurðsson says that from his observations since the year 2000, he’s tracked 56 glaciers that have ceased to be. Okjökull is more noteworthy, though, because of its ubiquity in Icelandic culture. “The name Ok appears in the sagas written in the 13th and 14th centuries, so we’ve known this mountain by name for eight centuries,” he says. “Most kids [in Iceland] knew that glacier by name, and it was very obviously visible from inhabited areas; it was a marker in the landscape.”

Though the reality of melting glaciers is grim, Howe and Boyer hope that the plaque dedication will serve as an invitation to take action to downscale our environmental impact. (FYI: Even if we completely stop carbon emissions now, scientists estimate the planet will continue to warm for decades—enough time to melt many more glaciers.) “A memorial isn’t for the dead. It’s for the living—it’s to come together after a loss,” says Boyer. “We know this is the first monument to a glacier that melted because of human-induced changes to the environment, but we hope it’s not the last. We hope it’s an inspiration to others around the world to create meaningful historical records and markers.”

Future Tense is a partnership of Slate, New America, and Arizona State University that examines emerging technologies, public policy, and society.