Ancient ice has preserved thousands of artifacts left in Norway’s highest mountain passes by hunters and travelers over the last 6,000 years. But even as rising temperatures are revealing these artifacts for the first time, the vanishing ice is putting them at risk.

Well above the tree line in Norway’s highest mountains, ancient fields of ice are shrinking as Earth’s climate warms. As the ice has vanished, it has been giving up the treasures it has preserved in cold storage for the last 6,000 years: Neolithic arrows, scraps of clothing from the Bronze Age, and skis from Viking Age traders. And those artifacts have provided some surprising insights into how ancient Norwegians made their livings.

Oppland’s past

Organic materials like wood, textiles, and hides are relatively rare finds at archaeological sites—unless they’re protected from the microorganisms that cause decay, they don’t tend to last long. Extreme cold is one reliable way to keep artifacts relatively fresh for a few thousand years, but once thawed out, these materials tend to degrade quickly. With climate change shrinking ice cover around the world, glacial archaeologists are racing the clock to find these newly revealed artifacts, preserve them, and study them.

“If something fragile like textile melts out, dries and is windblown it might be lost to science very quickly. Or an arrow might be exposed and then covered again by the next snow, within a few weeks, and remain well-preserved. The unpredictability means the fieldwork, led by Lars Pilø of Oppland County Council, Norway, needs to be well-timed and systematic,” said study co-author archaeologist James Barrett of the McDonald Institute for Archaeological Research at the University of Cambridge.

From 2006 to 2015, a team of archaeologists surveyed patches of ice in Oppland, a county in south-central Norway that’s home to some of the country’s highest mountains. Reindeer once gathered on these icy patches in the later summer months to escape biting insects, and from the late Stone Age to the Middle Ages, hunters followed. And trade routes threaded through the mountain passes of Oppland, linking settlements in Norway to the rest of Europe.

The slow but steady movement of glaciers tends to destroy anything at their bases, so the team focused on stationary patches of ice, mostly above 1,400 meters. That ice is found amid fields of blocky frost-weathered boulders, fallen rocks, and exposed bedrock that spend nine months out of the year buried beneath snow.

“Fieldwork is hard work—hiking with all our equipment, often camping on permafrost—but very rewarding. [You're] rescuing the archaeology, bringing the melting ice to wider attention, discovering a unique environmental history and really connecting with the natural environment,” said Barrett.

At the edges of the contracting ice patches, archaeologists found more than 2,000 artifacts, which formed a material record that ran from 4,000 BCE to the beginnings of the Renaissance. Many of the artifacts are associated with reindeer hunting. Hunters would have easily misplaced arrows and “scaring sticks”—poles with wooden flags that hunters would set up in rows to channel reindeer toward waiting bowmen—and they often discarded broken bows rather than lug them all the way home. Other items could have been used either by hunters or by traders traversing the high mountain passes of Oppland: all-purpose items like tools, skis, clothes, and horse tack, along with “incidental evidence of human journeys,” or, in lay terms, “horse dung.”

History’s hot and cold

Barrett and his colleagues radiocarbon dated 153 of the artifacts and compared those dates to the timing of major environmental changes in the region—such as periods of cooling or warming—and major social and economic shifts—such as the growth of farming settlements and the spread of international trade networks leading up to the Viking Age. They found that some periods had produced lots of artifacts, which indicates that people had been pretty active in the mountains during those times. But there were few or no signs of activity during other periods. The most surprising thing, according to Barrett, was the timing.

Oppland’s mountains can be daunting terrain at the best of times, but in periods of extreme cold, glaciers could block the higher mountain passes and make travel in the upper reaches of the mountains difficult. Archaeologists would have expected people to stick to lower elevations during a time like the Late Antique Little Ice Age, a short period of deeper-than-usual cold from about 536-600 CE.

But it turned out that hunters kept regularly venturing into the mountains even when the climate turned cold, based on the amount of stuff they had apparently dropped there.

“Remarkably, though, the finds from the ice may have continued through this period, perhaps suggesting that the importance of mountain hunting (mainly for reindeer), increased to supplement failing agricultural harvests in times of low temperatures,” said Barrett. A colder turn in the Scandinavian climate would likely have meant widespread crop failures, so more people would have depended on hunting to make up for those losses.

“In times of increasing demand for mountain resources,” Barrett and his colleagues wrote, “activity probably continued in the face of adverse or variable climatic conditions.”

Hunting During the Viking Age

Many of the artifacts Barrett and his colleagues recovered date from the beginning of the Viking Age, the 700s through 900s CE. Trade networks connecting Scandinavia with Europe and the Middle East were expanding around this time. Although we usually think of ships when we think of Scandinavian expansion, plenty of trade goods traveled on overland routes, like the mountain passes of Oppland. And growing Norwegian towns, along with export markets, would have created a booming demand for hides and furs to fight off the cold, as well as antlers to make useful items like combs. Business must have been good for reindeer hunters.

“With settlement expansion, the potential and necessity to carry out high-elevation hunting and to use mountain passes can only have increased,” wrote the researchers. And all of that expansion, population growth, and trade took place during the Medieval Warm Period, when the Scandinavian climate was warmer than usual, which must have made life easier for Viking Age traders and hunters. The things they lost, discarded, or otherwise left behind in the mountains offer a look into the Viking Age far from longships, raids, and colonies—and a view into the heart of the economic activity that supported that period of expansion.

Norway’s mountains are probably still hiding a lot of history—and prehistory—in remote ice patches. When Barrett and his colleagues looked at the dates for their sample of 153 artifacts, they noticed a gap with almost no artifacts from about 3800 to 2200 BCE. In fact, archaeological finds from that period, just at the end of the Stone Age, are rare all over Norway. The researchers say that could be because many of those artifacts have already been lost to ancient melting episodes at lower altitudes, while others are still frozen in the ice at higher altitudes. That means archaeologists could be extracting some of those artifacts from retreating ice in the next few decades.

Royal Society Open Science, 2018. DOI: 10.1098/rsos.171738. (About DOIs).