Researchers analyzed a stalagmite found in a cave in Wisconsin and discovered evidence of an ice age thousands of years ago interspersed by sudden massive warming events affecting large parts of the Northern Hemisphere.
The findings were published in a peer-reviewed study on Thursday in the journal Nature Geoscience by scientists at the University of Wisconsin-Madison.
Stalagmites grow incredibly slowly. The sample researchers had taken took roughly 20,000 years to grow the length of a small finger. It was formed through a process where water, which fell from the atmosphere, soaked into the Earth. From there, the water made its way through various rocks and crevices and eventually dissolved into limestone. Layers of limestone built over time until calcite, a mineral, was formed.
Stalagmites and stalactites are often confused with one another. Stalagmites grow from the cave floor pointing up and stalactites grow from the cave ceiling pointing down.
"Most scientists believe that the color of speleothems is determined by the mineral content. Pure calcite is white and almost colorless. Iron and other minerals, as well as acids from surface vegetation, combine with calcite crystals to add shades of red, orange and black to the color of speleothems. Others believe that humic and fulvic acids in the soil may also contribute to speleothem coloration," according to the National Park Service.
Significance of the study
The study's findings are the first to identify a potential connection between the ice age warm-ups and the Greenland ice sheet.
"This is the only study in this area of the world that is recording these abrupt climate events during the last glacial period," says Cameron Batchelor, who led the analysis while completing her PhD at UW-Madison.
Scientists can use the stalagmite’s isotopes to gather further information about the environment, weather conditions and temperatures from thousands of years ago.
The researchers used a specialized imaging technique that allowed them to analyze every layer of the stalagmite. This can be broken down to show the annual changes in the aforementioned information categories
The data collected tell a climate story that might help scientists predict future climate changes and the impact of global warming.