Above the treeline and accessible only by a tough hike or helicopter ride, the Lendbreen ice patch in Norway ’ s Jotunheim Mountains, about 200 miles northwest of Oslo, is a prohibitively remote place. But a thousand years ago, long before good roads were built in the valleys, this rugged mountain pass was an artery of Viking Age traffic.

During 2011 ’ s particularly warm summer, archaeologists surveying Lendbreen for the first time found centuries-old horse dung littered all over the ground and ancient artifacts melting out of the ice. Among those early finds was a 1700-year-old tunic, the oldest piece of clothing ever discovered in Norway and one that is puzzlingly complete, perhaps tossed off by a traveler in the delirious late stages of hypothermia.

Now, after several more explorations of the site, researchers have discovered more than 1,000 artifacts including scraps of wool clothing and leather shoes, fragments of sleds, horseshoes and walking sticks. A new analysis of artifacts from the ice patch, published today in the journal Antiquity , offers new information about how this mountain pass was used over time—and some ominous clues about why it was eventually abandoned.

Lendbreen has provided the most archaeological finds of any ice patch in Scandinavia and possibly the world. While most other ice-patch sites in northern Europe were hunting sites, Lendbreen was a place for travelers. Farmers, herders and merchants came through here to cross the 6,300-foot-tall Lomseggen mountain ridge to reach local high-altitude summer pastures and perhaps trading posts and other destinations much further away.

This new research led by Lars Holger Pilø, co-director of the Glacier Archaeology Program in Norway ’ s Innlandet County, looked at the radiocarbon dates of 60 items collected at Lendbreen. Their results showed that the pass was used from the Roman Iron Age—a time around 300 A.D. when the Romans had increasing influence in northern Europe, although their empire did not extend to modern-day Norway—through the Middle Ages.

“ The pass was at its busiest during the Viking Age around 1000 A.D., a time of high mobility and growing trade across Scandinavia and Europe,” says study co-author James Barrett, an archaeologist at the University of Cambridge. “ This remarkable peak in use shows just how connected even a very remote location was to wider economic and demographic happenings.”

As climate change accelerates ice melt in the high mountains, archaeologists are suddenly discovering a wealth of artifacts that had been frozen for centuries. Icy conditions can preserve rare, delicate materials like textiles and wood, but these objects may decay and disappear forever if they aren ’ t collected in time. These sites can be difficult to interpret, however, because meltwater and strong winds may carry objects from their original context. At Lendbreen, for instance, a Bronze Age ski was found in four pieces discovered as much as 800 feet apart, while other objects that might have been dropped on the trail hundreds of years apart can get washed together. Archaeologists also have found hundreds of bones from animals like packhorses as well as a line of cairns marking the trail.

“ The Lendbreen route is much better marked than the other known passes over the ridge and even has the ruins of a shelter in the pass,” Pil ø says. “ Since there are few finds from the other passes so far, it is hard to tell whether Lendbreen was the most trafficked of the passes, but it appears to have had a special significance. Perhaps some of the travelers were not locals but longer-distance travelers and needed better guidance.”

The long-haul travelers may have picked up mountain products like wool, reindeer pelts and antlers, or cheese and butter from summer farms to bring to far-off locations, maybe even outside Norway. For example, the archaeologists have found a birch bark container packed with raw wool. But the researchers think the pass also served as an important route for local travel from permanent farms in valleys to summer farms at higher altitudes, where livestock could graze for part of the year. (In summer, the farmers needed the meadows on their main farms to produce hay for winter fodder.)

For an archaeological site like Lendbreen to form, a mountain pass must cross stretches of ice and snow where items dropped by travelers would survive for centuries or millennia, Barrett says. Similar mountain passes in the Alps and the Himalayas wouldn’t have been used in cold seasons when preservation would be at its peak. But people probably crossed the Lendbreen route in late winter through early summer, when snow on the ground made it easier to travel over the otherwise-rough terrain. Pil ø adds that the preservation of organic materials makes Lendbreen “ a completely new ballgame compared to normal mountain passes without ice where only a few metal objects remain from the traffic.”

“ This study is one of the first ice-patch archaeology studies to explore the role of mountain passes in travel over long time scales,” says William Taylor, an assistant professor and curator of archaeology at the University of Colorado Museum of Natural History. Taylor, who was not involved in this research but has explored ice patches in other parts of the world such as Mongolia, says that these results show how the Roman and Viking economies transformed mountain zones. “ It is fascinating to see direct evidence for the emergence and re-emergence of mountain travel routes—not as an abstract concept, but as a tangible archaeological phenomenon demonstrated by horse dung, horse bones and the objects dropped by travelers engaged in important pastoral work.”

The age of the Lendbreen artifacts indicates that the use of the pass declined after the Viking Age. This decline could be linked to a cooling period known as the Little Ice Age as well as the Black Death, the 14th-century plague that killed between half and two-thirds of the Norwegian population.

“ There were also other subsequent pandemics in the late medieval period making the situation even worse,” Pilø says. “ This obviously had a great influence on local settlement and economy, and thus mountain traffic, which dwindled, both long-distance and to the local summer farms.” By the time local summer farms were reestablished a few centuries later, the Lendbreen pass seems to have been forgotten as people traveled different routes.

The current COVID-19 pandemic, which has stymied travel , may doom the prospects of further exploring both Lendbreen and another promising mountain pass this summer. “ One more reason to hope that the glaciers do not retreat much this year,” Pilø says.

Regardless, the search for artifacts at Lendbreen may be nearing its end. The archaeologists have scoured an area equal to 35 football fields in what is likely the largest glacial archaeology survey ever conducted. But last summer was an especially severe year for ice melt. The discoveries, though not analyzed in the Antiquity study and have yet to be carbon-dated, were “ astounding,” Pilo says.

The field team found the remains of a dog with a collar and leash, a wooden tinderbox and a preserved horse snowshoe, which supports the idea that this pass was mainly used when it was covered in snow. Many of the artifacts were spotted lying on the ice, which normally implies that the melt has reached previously untouched layers. When the team came back weeks later, another few feet of ice had melted, but no new finds had appeared.

“ All that was left on the ice was the dung from the packhorses,” Pilø says. “ This makes us believe that the ice from the time of the pass has now melted out.”