In recent research, scientists analyzed ice cores collected from Greenland, with data spanning up to 120,000 years, to better understand these abrupt climate events and their future implications. These events, called Dansgaard-Oeschger events, are considered "tipping points" in Earth's climate. According to Christo Buizert, lead author of the study and associate professor at Oregon State University, tipping points represent thresholds that can lead to rapid and widespread climate shifts.

"It is really important to understand such tipping points in the climate, because they may result in catastrophic and irreversible change," said Buizert.

The research, recently published in the *Proceedings of the National Academy of Sciences*, investigates the Dansgaard-Oeschger cycle, a pattern triggered by the Atlantic Meridional Overturning Circulation (AMOC), which controls water circulation in the Atlantic Ocean. AMOC's instability has significant global effects, including cooling in Europe and failure of monsoons in Asia.

"The AMOC is fundamentally unstable, and when it collapses, big things happen across the globe," said Buizert. "It is cause for concern for the future because climate models suggest the AMOC will likely weaken again under global warming, potentially impacting billions of people."

Buizert and his team focused on ice cores from lesser-studied areas of Greenland to gain new insights into the impact of Dansgaard-Oeschger events. Their research reveals that interactions between the AMOC and winter sea ice were crucial to these events. Contrary to previous beliefs, winter sea ice likely extended as far south as modern-day France and New York City during these periods.

"The model shows that the Nordic Seas alone wouldn't be big enough to drive a climate change event of this size," Buizert explained.

Although the AMOC has remained stable for the last 11,700 years, current climate models predict it will weaken in the future, potentially triggering new climate shifts.

"We know the AMOC will weaken, but will it collapse? That is the big question," Buizert added. "The climate does not behave in linear patterns; it can change quickly and irreversibly."

The research was conducted in collaboration with scientists from five countries and supported by the National Science Foundation. The drilling of the Renland ice core in Greenland was led by the University of Copenhagen.