The ice is giving up in Norway, and archaeologists are pulling history out of the melt.

Researchers with Secrets of the Ice recovered 48 prehistoric arrows during a recent three-week expedition in Jotunheimen, a mountainous region in southern Norway about 200 miles from Oslo. One of the finds, an arrowhead made of fine slate with two parts of its shaft, is estimated to be 5,000 to 6,000 years old.

The team has spent the past 20 years excavating in the region as part of Secrets of the Ice, which it describes as the largest glacial archaeology program in the world. The project is a collaboration between the Innlandet County Council and Oslo’s Museum of Cultural History.

So far, researchers have recovered more than 5,000 artifacts from 73 archaeological sites. Those finds include reindeer-hunting equipment, the remains of packhorses, clothing and other objects from everyday life. The project has also uncovered a 3,400-year-old leather shoe and the world’s oldest intact pair of wooden skis.

When archaeologists began excavating in 2006, most of the artifacts they found were less than 2,000 years old. In a recent update, the researchers said the “picture has changed dramatically” as more glaciers and adjacent ice patches melt because of human-caused climate change.

“The melting has been extensive,” they write. “In many places, ice that has survived for thousands of years is now beginning to disappear completely. And this is where we see the connection: The oldest ice contains the oldest finds.”

This summer, the team worked on ice patches next to the Langfonne, Storfonne and Handklefonne glaciers in the Kvitingskjølen mountain area. Along with the oldest arrow, they found a 3,600-year-old complete arrow with a wooden shaft and an arrowhead made from a freshwater mussel shell. Several other arrowheads were made of bone, while one was made of iron.

Organic materials usually break down when exposed to the elements, but ice can preserve them. “Ice pauses the process of decay,” Anna Fiorentino wrote in May for Smithsonian magazine. “By keeping organic material, such as wood and textiles, at a consistent, low temperature without oxygen, it slows microbial activity that could otherwise decompose the items in months.”

That preservation has extended to clothing. Archaeologists have previously unearthed a complete tunic from 300 C.E. and a complete mitten from 1000 C.E.

Espen Finstad, the glacial archaeologist who leads the Secrets of the Ice project, said this year’s work hit differently.

“We have always acknowledged this contradiction and the reality behind our work,” Finstad tells Science Norway’s Ida Irene Bergstrøm. “But this is the first time it has truly affected us on an emotional level. This year, there was a much deeper sense of seriousness and sadness … It’s brutal. And this year, that reality struck us more forcefully than ever before.”

For now, the team is securing, documenting and preparing the latest finds. The artifacts are being housed at the Norwegian Mountain Center in Lom, where some are on display in a special refrigerated case. In December, they will be taken to the Museum of Cultural History for further processing and conservation.

Finstad said that, based on what researchers have seen over the past two decades, they suspect the ice at many of the archaeological sites will disappear completely within the next 20 years.

“There has been ice here for 6,000-7,000 years,” Finstad tells Science Norway. “Nature has been warning us and sending signals for many years. But now it’s giving up. Now it is simply going to melt.”

Read more from Smithsonian Magazine.