New research involving various ice cores from Greenland, encompassing a time span of up to 120,000 years, sheds light on sudden Dansgaard-Oeschger events, their progression, and potential implications for our future.
A shifting climate can lead to a dramatic change in ocean currents, resulting in chaotic weather patterns and potentially initiating a sudden Ice Age on Earth.
This scenario may sound like a plot from a Hollywood movie—much like the 2004 sci-fi disaster film “The Day After Tomorrow”—but it actually reflects instances that occurred multiple times during the last Ice Age, which ended more than 11,000 years ago.
Recent findings from ice cores across Greenland reveal new insights regarding these swift climate events, their mechanics, and what they could indicate for the future.
The Dansgaard-Oeschger events are marked as “tipping points” in Earth’s climate, where crossing certain thresholds leads to rapid and extensive shifts, explained lead author Christo Buizert, who is an associate professor in the College of Earth, Ocean, and Atmospheric Sciences at Oregon State University.
“Understanding these tipping points is crucial, as they can lead to catastrophic and irreversible changes,” he stated.
The study has just been published in the Proceedings of the National Academy of Sciences.
Occurrences of the Dansgaard-Oeschger cycle, happening over 25 times during the last Ice Age, are attributed to the swift switching of the Atlantic Meridional Overturning Circulation (AMOC), which is responsible for the distribution of water across the Atlantic Ocean. The Gulf Stream, known for transporting warm tropical waters to the North Atlantic, is part of this circulation.
“The AMOC is inherently unstable. When it fails, significant global impacts can occur, including major cooling in Europe and the North Atlantic, alongside failures of the Indian and Asian monsoons,” Buizert noted. “This kind of instability was common during the last Ice Age, and its potential recurrence under global warming raises significant concerns for the future, as it could affect billions of people.”
Buizert, a paleoclimatologist, analyzes ice cores to reconstruct historical climate changes. Researchers gather and examine these ice cores from Greenland and Antarctica, analyzing the trapped water, dust, and tiny air bubbles for insights into Earth’s atmospheric changes over extensive time periods. These ice core records serve as fundamental resources for understanding past climate events.
Along with his colleague, Buizert examined ice cores from various locations in Greenland, including previously overlooked sites in southern and coastal eastern regions, to gain a clearer understanding of Dansgaard-Oeschger events’ effects across the continent.
Fresh data combined with new climate models suggest that interactions between the AMOC and winter sea ice are critical for triggering Dansgaard-Oeschger events. Previously, scientists believed that sea ice from the Nordic Seas north of Iceland primarily influenced these events, but their new analysis indicates that winter sea ice would have moved much further south, reaching latitudes as low as 40 degrees. This means that the ice would have reached areas as far south as modern-day France and New York City, locations also featured in “The Day After Tomorrow.”
“Our models indicate that the Nordic Seas alone would not be sufficient to initiate such a significant climate event,” Buizert emphasized. “It simply lacks the necessary impact.”
For the past 11,700 years, the AMOC has operated relatively smoothly, but current climatic conditions and models predict it may weaken again, albeit for different reasons than those observed during the last Ice Age, according to Buizert.
“While we expect the AMOC to weaken, the central question remains: will it collapse? Although this weakening seems to be gradual for now, it could reach a tipping point, triggering abrupt climate change events as seen in the past,” he explained. “Climate behavior is not linear; it can shift suddenly and irreversibly.”
This research received backing from the National Science Foundation and involved collaboration among scientists from five different countries. The University of Copenhagen in Denmark spearheaded the drilling of the Renland ice core in eastern Greenland.
