Breakthrough reshapes our view of last‑ice‑age sea level
A Tulane University-led study has overturned long‑standing assumptions about the forces behind the dramatic global sea‑level rise that marked the end of the last ice age. The research, published in Nature Geoscience, finds that melting ice sheets in North America contributed far more to sea‑level rise between about 8,000 and 9,000 years ago than scientists had previously believed. In this reconsideration, Antarctica’s role appears comparatively small, while the North American ice masses emerge as the dominant driver of the period’s seas swelling.
The results imply that a massive influx of freshwater into the North Atlantic—far larger than earlier estimates—helped sweep global sea levels higher by more than 30 feet (roughly 10 meters) during the early Holocene. This challenges decades of conventional wisdom that placed Antarctic melt at the center of sea‑level rise during this interval and calls for a major revision of the region’s ice‑melt history.
Why the finding matters for climate understanding
“This requires a major revision of the ice melt history during this critical time interval,” said Torbjörn Törnqvist, Vokes Geology Professor at Tulane and a co‑author of the study. He noted that the amount of freshwater entering the North Atlantic helped reshape ocean circulation patterns that influence climate across the Northern Hemisphere.
The North Atlantic is a linchpin of global climate, sustaining currents like the Gulf Stream that moderate temperatures in Northwest Europe. Modern concerns about a weakening Gulf Stream and shifting rainfall patterns often center on Greenland’s melt. The new evidence from the end of the last ice age shows a historically resilient system, at least under those past conditions, even as freshwater fluxes spiked—raising questions about how quickly today’s warming could alter ocean dynamics.
From Mississippi sediment cores to a global picture
The new narrative rests on a sequence of discoveries and cross‑continental comparisons. The breakthrough work began with former Tulane postdoctoral researcher Lael Vetter, who found deeply buried ancient marsh sediments near the Mississippi River across from New Orleans. Carbon‑14 dating pushed reliable sea‑level reconstructions back to more than 10,000 years ago, enabling researchers to chart a clearer timeline of melt and rise.
Building on that foundation, former PhD student Udita Mukherjee integrated the Mississippi Delta record with parallel data from Europe and Southeast Asia. The global comparison revealed striking disparities in sea‑level rise rates that could only be reconciled by a far larger North American ice melt than previously assumed. As Mukherjee, now a postdoctoral fellow at the University of Hong Kong, explains, a globally inclusive dataset is essential for accurate climate storytelling. “Broadening our focus beyond North America and Europe to include valuable high‑quality data from Southeast Asia was critical for this study,” she said. “By embracing a truly global perspective in climate studies, we can enhance our understanding and work together towards a sustainable future.”
Implications for today’s climate risk assessment
The study’s authors emphasize that while the end‑ice‑age dynamics are distinct from contemporary warming, the research highlights the sensitivity of global sea level to freshwater inputs in major ocean basins. It also suggests that the Gulf Stream and its associated climate effects could respond to different drivers than previously thought, underscoring the importance of refining models that project future sea‑level rise.
The research was funded by the U.S. National Science Foundation and included collaborators from the University of Ottawa, Memorial University (Canada), Maynooth University (Ireland), and the University of South Florida. As scientists continue to piece together the complex history of Earth’s climate system, this study stands as a reminder that major regional contributors can drive global changes in unexpected ways.
