USF Research News

New Research: An Ice Cave in Transylvania Yields Window into Region’s Climate Past

April 27, 2017

International science team fills in critical gap in Central and East Europe’s climate record back 10,500 years ago

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Scărișoara Ice Cave is one of the most important scientific sites in Europe with its towering ice formations and underground glaciers (Photo courtesy of Gigi Fratila & Claudiu Szabó).

TAMPA, Fla. – Ice cores drilled from a glacier in a Romanian cave are providing new scientific evidence of how Europe’s winter weather and climate patterns fluctuated during the last 10,000 years, providing new insights for understanding today’s current climate changes. The research is published today in the journal Scientific Reports.

USF Professor Bogdan Onac and former USF PhD student Aurel Perșoiu, working with an international team of scientists in western Romania’s Scărișoara Ice Cave, harvested cores of ancient ice to reconstruct winter climate conditions during the Holocene period. The Holocene is important to climate scientists because it was a period of warming following the last glacial period. Until now, there was a lack of long-term reconstructions of winter climatic conditions and that has hampered a full understanding of past climate dynamics, Onac said.

Researchers from the Emil Racoviță Institute of Speleology in Cluj-Napoca, Romania, and USF’s School of Geosciences gathered their evidence in what is known as the world’s oldest cave glacier hidden deep in the heart of Transylvania. The project, funded by the National Science Foundation and the Romanian Ministry of Education, also involved researchers from University of Belfast, University of Bremen, and Stockholm University.

“Most of the paleoclimate records from this region are plant-based, and track only the warm part of the year — the growing season,” says Candace Major, program director in NSF’s Directorate for Geosciences, which funded the research. “That misses half the story. The spectacular ice cave at Scarisoara fills a crucial piece of the puzzle of past climate change in recording what happens during winter.”

Scărișoara Ice Cave is one of the most important scientific sites in Europe with its towering ice formations. Each year during the last 10,000 years, snow and rain has dripped into the depths of Scărișoara, where it froze into thin layers of ice and held onto chemical evidence of past winter temperature changes and the source of the area’s moisture, Perșoiu said.

Located in the Apuseni Mountains, the region receives precipitations from both the Atlantic and Mediterranean sources and is an ideal location to study shifts in the storm tracks across East and Central Europe.

Ciubotarescu
Researchers gathered their evidence in the world’s oldest cave glacier hidden deep in the heart of Transylvania (Photo courtesy of Bogdan Onac).

The newly published research produces the first reconstruction of autumn through winter temperature and changes in the source of precipitation in East and Central Europe that drove the regional climate dynamics, Perșoiu said. The radiocarbon ages obtained on minute fragments of leaves and wood preserved in the ice indicate that the ice is at least 10,500 years old, making it one of the oldest glaciers on Earth outside the polar region.

The researchers were able to chart the details of winter temperatures in East and Central Europe reaching a maximum during the mid-Holocene and decreasing thereafter towards the Little Ice Age, 150 years ago. Further, a major shift in the atmospheric dynamics occurred during the mid-Holocene period when winter storm tracks switched and produced wetter and colder conditions in northwestern Europe and the expansion of the Mediterranean-type climate towards southeastern Europe.

The work is a significant advancement of climate science because much of the reconstruction of Earth’s past record has relied on summer conditions and charted climate fluctuations through vegetation-based samples such as tree ring width, pollen, and other organisms that thrive in the warmer growing season. Winter was a season absent important data, Onac said.

The isotopic analysis of the ice preserved in the cave showed that, contrary to warm summers, winters were cold 10,000 years ago, making Eastern Europe a place with strong contrasting seasons. The increasing winter temperatures led to rapid environmental changes that allowed northward expansion of Neolithic farmers towards mainland Europe, and the rapid peopling of the continent.

“Our reconstruction provides one of the very few winter climatic reconstructions - filling in numerous gaps in our knowledge of the past climatic variability,” Onac said.

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The scientists worked in temperatures of -6 Fahrenheit during a February 2003 three-day expedition to the cave (Photo courtesy of A. Persoiu).

Working in temperatures of -15 Fahrenheitduring a three-day expedition to the cave in February 2003, the team harvested 56 cores ranging from 21 to 63 centimeters totaling 22.5 meters down into the ice. The frozen cores were transported to Stockholm University, where they were melted under controlled conditions. Organic matter retained from the cores was radiocarbon dated while the sable isotope analysis was performed at USF’s labs in Tampa.

By examining the ice cores – where layers of ice act as a timeline of isotopic changes – the scientists were able to chart how East and Central Europe grew warmer and wetter with Mediterranean cyclones during the autumn and early winter penetrating further northeast into the European continent and leading to a differentiation between the Atlantic Ocean-dominated European climate in West and Northwest Europe.

“Our data allows us to reconstruct the interplay between Atlantic and Mediterranean sources of moisture, which are modulated by phases of the North Atlantic Oscillation,” Onac said. “We can also draw conclusions on past atmospheric circulation patterns, with huge implications for future climatic changes. Our research offers a long-term context to better understand these changes.”

Researchers are continuing to work in the cave and just two weeks ago finished drilling to a depth of 25 meters and possibly extending the record back some 13,000 years or more, Perșoiu said. The new research is intended to provide information to as far back as the end of the Last Glacial period, he said.

The Church
Located in the Apuseni Mountains, this cave is considered to be the world’s most investigated ice cave with more than 100 papers and monographs published over the past 90 years (Photo courtesy of Bogdan Onac).

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