During the Last Glacial Period some 11,500 years ago, Greenland went through massive changes called interstadial events. Then, it quickly oscillated between lower and higher temperatures, which melted and then refroze (and then melted again) massive ice sheets in the region. Geological records appear to show that around the same time that this was happening in Greenland, Earth’s lower latitudes were experiencing similarly swift and dramatic climate changes, but it’s been hard for scientists to determine exactly when all of these abrupt shifts occurred. New research offers some clues as to what happened.
The new study, published in Science on Thursday, is based on scientists’ examination of stalagmite records from all over the world. The research was possible because stalagmites form in layers, and each layer preserves records of what environmental conditions were like when it formed.
The authors’ observations suggest that these changes in Greenland were connected to abrupt climate changes in faraway places—including even as far away as the tropics.
Records of Greenland’s ice cores show that the region experienced 25 major rapid temperature fluctuations during the Last Glacial Period. Those shifts, known as Dansgaard-Oeschger events, have been associated with sharp increases in air temperature over Greenland of up to a stunning 60 degrees Fahrenheit (16 degrees Celsius) in just a few decades, which rapidly melted ice. Though the warming periods were very quick, the hot conditions they created persisted for hundreds of years before giving way to a more gradual cooling period.
Based on that knowledge, the researchers examined 63 ancient climate records in stalagmites from caves around the world, across Europe, Asia, and South America. They found that changes seen there lined up with the changes in Greenland. Europe saw swift temperature increases and alterations in rainfall that lined up with when Dansgaard-Oeschger events were happening, as did Asia and South America’s monsoon regions.
The researchers hope to bring these methods to studying even more stalagmite samples in order to determine whether or not Greenland’s Dansgaard-Oeschger events impacted regions even farther south. They also hope their findings will help scientists making future climate predictions, because they illuminate how interconnected our planet’s climate systems are.
Rapid climate change is a scary prospect in our present climate where humans have pumped carbon dioxide into the atmosphere at a rate unseen in millions of years. Another paper published on Thursday chronicled the record Greenland ice loss last summer. Other rapid shifts in the past year include huge fires in the Arctic and Australia, Arctic sea ice extent falling off a cliff in recent months, the sudden collapse of Canada’s last ice shelf, and the fact that we’re racing toward one of the hottest years on record. Sudden swings in the climate are an area of active research, including if (or when) we could cross tipping points. Looking at the past is one way to gauge that and where the pressure points may be.