Underground weather: what caves can reveal about climate change, past and future

Underground weather: what caves can reveal about climate change, past and future

During the so-called Little Ice Age, medieval Europe experienced extremely cold winters and unusually mild summers. Extreme weather disasters are becoming more common, bringing with them the ravages of disease and famine. Because we did not fully understand climate science at the time, many blamed evil or witchcraft for the long cold spell.

“Witches” were persecuted throughout Europe, but of course this did nothing to bring the planet out of the Little Ice Age. Historical records show that Europe during the Little Ice Age struggled through an endless series of natural disasters. For example, during the 16th and 17th centuries, the Free Imperial City of Nuremberg—the most powerful and culturally important city-state in the Holy Roman Empire—regularly experienced severe floods, one of the harshest aspects of life in a thriving society because of it. To the German Renaissance.

“Witches” were persecuted throughout Europe, but of course this did nothing to bring the planet out of the Little Ice Age.

Thanks to new research published in the journal Earth and Planetary Science Letters, ordinary people living in the 21st century can understand the secrets of the Little Ice Age in ways that were impossible for the era's victims, such as accused witches and the flooded citizens of Nuremberg. In fact, geologists from the University of Heidelberg and the Karlsruhe Institute of Technology have discovered a treasure trove of climate information about their region in Germany and the world as a whole, dating back centuries and centuries.

Interestingly, they found all this in a completely unexpected place: stalagmites, or spiers, growing from the bottom of caves.

It all comes down to the fact that stalagmites are mineral deposits that form from groundwater in underground caverns such as caves. For the majority of climate research, scientists have only been able to measure short-term climate fluctuations over hundreds of years using tree-ring records. Even then, these tree-ring records had to be analyzed alongside independent measurements from other studies, as well as cross-referenced with historical records.

However, stalagmites provide new insights into climate fluctuations because German researchers were able to examine the isotopic composition of oxygen in stalagmites in southern Germany that formed from hard water. Unusually warm years produce very wet winters while unusually cold years produce very wet summers. By analyzing the history of rainfall recorded in each microscopic layer of the stalagmite, scientists were able to identify short-term climate fluctuations from centuries ago.

Active dripstone formation in a side area of ​​“Kleine Teufelshöhle”. (Photo courtesy of KIT, taken as part of the HEiKA Check Extrema project)

Hence these new ideas about the Little Ice Age. According to a statement from co-author Dr. Tobias Kluge from the Karlsruhe Institute of Technology, “The data point to cold, dry winters that delayed the annual melting of ice and snow, leading to significant short-term floods with catastrophic consequences.” All of this occurred against the larger backdrop of the Little Ice Age, which was caused by a complex set of factors including decreased sunspot activity, increased volcanic activity, changes in the Earth's orbital geometry and disruption of the Atlantic Overturning Circulation (AMOC). . However, this research not only sheds light on Earth's history, it also helps scientists better understand the planet's future.

“In the public consciousness, unusual floods, heatwaves or droughts are among the most tangible indicators of climate change,” the scientists wrote in their paper, adding that it is difficult to predict the scale of these extreme events at either a regional or regional scale. Local standards. “Developing reliable small-scale climate models requires tests against past climate records, but they are often incomplete, or cover only partial aspects across a range of environmental parameters,” such as the seasonal bias found when analyzing tree-ring records.

However, when tree-ring data is combined with data from caves, it creates a comprehensive record of Earth's water history with data that can be extrapolated in ways that are “uniquely suited to resolving short-term extreme climate events at the regional scale.” Authors' report.

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“In the public consciousness, unusual floods, heat waves or droughts are among the most tangible indicators of climate change.”

This is not the only recent research linking the science of climate change and cave science. A 2019 study in The Anthropocene Review described how climate change poses a threat to rare ecosystems found in closed cave systems, many of which are valued as research sites for biologists because, in theory, they are largely disconnected from Earth. Influences of the outside world. It's not great news for cave-dwelling life forms, as their worlds appear not to be immune to the effects of climate change. The subterranean climate, like the climate at the surface, can be affected in many ways by global warming caused by human activity. However, in contrast to surface species, subterranean life forms may struggle to cope.

“Because they evolved in a stable environment, underground species are expected to show low tolerance to climate perturbations, and can theoretically cope with such changes only by changing their distribution range or by adapting to new environmental conditions,” the authors wrote. “However, they must have more obstacles to overcome than pelagic species in such transitions, and thus could be more vulnerable to local extinction.”

There is at least one example of cave life suffering due to climate change: Troglohevantes, or a genus of very small spiders known as leaf weavers. Scientists writing for the journal Ecographia explained how they studied thermal conditions in caves in the Western Alps and compared this data to the prevalence of… Rcom. oglohyphantes. They found that the distribution of spiders is linked to temperature changes from the Pleistocene era, as well as modern climate changes.

After analyzing this data, along with information on constant temperatures inside caves, and using specialized ecological modeling, the researchers concluded that subterranean spider species have a bleak outlook. In fact, it “indicated a future decline in habitat suitability for subterranean spiders and the potential extinction of more restricted endemic species. When compared to other species that live in confined habitats such as islands and mountains, we expect cave species to be just as vulnerable.” “If not more vulnerable to climate change.”

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