Transylvania Cave Offers a View Into Europe's Past Climate

An underground sheet of ice in the mountains of Transylvania has given scientists a glimpse of climate changes in prehistoric Europe that helped humans settle that part of the continent.

Romania’s Scarisoara Ice Cave holds the world’s oldest cave glacier, built up by water dripping into the cavern over thousands of years. The region’s weather is shaped by the currents of both the Atlantic Ocean and the Mediterranean Sea, and the chemistry of the ice can reveal when each of those systems played the dominant role. And a shift toward the warmer Mediterranean weather may have given late Stone Age people a toehold in what had been an inhospitable land.

Researchers took a core sample of the ice from the cave, giving scientists their first records of winter temperatures in the region. Previous reconstructions were drawn from markers of plant growth like tree rings, which reflected summer conditions, said Aurel Persoiu, a paleoclimatologist at Romania’s Emil Racovita Institute of Speleology.

“It very nicely fills a gap in our knowledge,” Persoiu said.

The findings, published this week in the journal Scientific Reports, indicate the cave ice dates back more than 10,000 years. Lower amounts of stable hydrogen and oxygen isotopes in the ice indicate colder weather, Persoiu said.

The ice core revealed that summer temperatures got cooler and winter temperatures warmed up between about 8,000 and 5,000 years ago, and that reduction in extremes helped make Transylvania more palatable to Neolithic farmers.

“There were cold winters, hot summers and wet. That means the rivers were very active and there was a lot of flooding,” Persoiu said. So people migrating up the Balkan Peninsula shifted toward Western Europe. But when the climate shifted toward a more Mediterranean influence, warmer, drier winters allowed for stable agriculture, bringing people to the area, he said.

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While the Scarisoara ice core has given scientists a window into the Holocene past, its applications for the future have been limited by a very modern problem: climate change. The top layer of the glacier has been melting away, erasing whatever data it might have held since the late 19th century, Persoiu said.

“The age of the ice at the uppermost level is something like 1860 or 1880,” he said. “We lost the last 150 years of ice, so we cannot compare it to present-day conditions … All over the planet, caves of ice are disappearing quite fast.”

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