Dripstones from Romanian cave offer insight into Europe’s climate change

A study conducted by an international research team led by Dr. Sophie Walken of the University of Heidelberg on precipitation patterns in eastern central Europe since the end of the last ice age reveals dynamic processes in atmospheric circulation, such as the North Atlantic jet stream. Ta. Affects regional variations in precipitation.

The study is published in the journal Communications Earth & Environmental.

Researchers analyzed drip stones taken from the Crošani Cave in Romania. The cave serves as a natural climate archive, allowing conclusions to be drawn about rainfall fluctuations over a period of about 20,000 years. Dr Walken said new discoveries about the dynamics of Europe’s climate could contribute to improvements to current climate models and the ability to more accurately predict the likelihood of extreme weather events.

Of particular importance to regional weather and precipitation patterns in mid-latitude regions of Europe is the North Atlantic jet stream. An atmospheric current that crosses the North Atlantic Ocean from southwest to northeast and carries precipitation to Europe.

It is well known that climate change has affected the strength and trajectory of the jet stream in the past. However, as Dr Walken explains, there is limited understanding of how climate-induced jet stream variations have affected local and regional precipitation patterns in Europe.

Natural climate archives, such as the dropstones of Romania’s Crošani Cave, provide information about climate changes in past eras. Lime deposits, also known as limestone caves, are formed by precipitation that seeps into the interior of a cave over thousands of years.

Geochemical investigations allow conclusions to be drawn about the age of the deposits, and therefore about past environmental conditions and precipitation. The study focused on three stalagmites that contain information about hydroclimatic conditions in eastern central Europe over the past 20,000 years.

The results show how warming and melting of the Northern Hemisphere’s ice sheets, which continued until about 5,000 years ago, changed the trajectory of the North Atlantic jet stream. As a result, precipitation during the Late Last Ice Age, about 20,000 years ago, and the early to mid-Holocene, the current interglacial period that followed the last Ice Age about 7,000 years ago, was 20 to 30 percent higher than today.

They found that regardless of long-term temperature changes in the North Atlantic region, precipitation fluctuations in the region fluctuated over relatively short periods of centuries, or even just a few decades.

“Our research shows that dynamic processes, such as changes in atmospheric flow, particularly wind patterns and jet streams, influence precipitation and weather patterns in central Europe,” Dr Walken said. emphasizes.

This helps fill a research gap, as previous reconstructions mainly refer to thermodynamic processes, i.e., atmospheric warming, which directly links rising temperatures to increased precipitation. she explains. These reconstructions are often based on climate models that still have uncertainties in simulating local and regional precipitation patterns.

“Climate change is already causing more frequent and intense precipitation events. Based on current projections, the number of extreme weather events and heavy rainfall events in some parts of Europe will continue to increase,” Dr Walken said. says.

A deeper understanding of the underlying dynamical processes is key to more accurately predicting future precipitation patterns and the potential for extreme weather events. Against this background, the current results obtained from Krošany Cave could help improve the accuracy of climate models and predictions, the geoscientist added. Together with a research group at the Institute of Geosciences and Environmental Physics at Heidelberg University, she is reconstructing past climates over thousands of years.

The study was carried out in collaboration with scientists from the University of Mainz and the University of Innsbruck (Austria). Other institutions from Germany and Romania also participated.