New findings rewrite the ice-melt narrative of the late last ice age
Recent research led by Tulane University and published in Nature Geoscience upends decades of assumptions about how Earth’s oceans responded as the last ice age waned. The study shows that retreating North American ice sheets, not Antarctica, were the dominant driver of global sea-level rise between roughly 8,000 and 9,000 years ago. The magnitude of freshwater entering the North Atlantic from these ice sheets appears to have been far larger than previously believed, triggering substantial changes in ocean circulation and coastal exposure across the globe.
How the North American contribution reshapes our understanding
For years, scientists emphasized Antarctica’s role in rising seas during this interval. The Tulane findings, however, indicate that North American ice masses alone contributed more than 30 feet (about 10 meters) to global sea level during that period. This challenges established models and suggests a much different pace and pattern of meltwater input into the Atlantic than scientists assumed. The result is a revised timeline for sea-level rise that places North American ice dynamics at the center of a critical transition in Earth’s climate history.
What this means for the climate system and ocean currents
The influx of freshwater into the North Atlantic has long been linked to impacts on major ocean currents, including the Gulf Stream, which helps moderate Europe’s climate. The Tulane study argues that this region’s early post-glacial melt was unusually potent, yet the climate system showed a surprising resilience. In other words, while freshwater pulses can weaken currents in theory, the past record indicates that the system did not collapse as readily as some models predict for the near future. This resilience has important implications for how we assess climate-risk scenarios today, where rapid melt could push the Atlantic toward different circulation states.
From marsh sediments to a global sea-level picture
The breakthrough began with buried marsh sediments near the Mississippi River, preserved and accessible for carbon dating. Former Tulane postdoc Lael Vetter’s work extended sea-level reconstructions beyond what offshore drilling could alone reveal, placing the record at more than 10,000 years ago. Building on that foundation, researcher Udita Mukherjee integrated the Mississippi Delta data with high-quality records from Europe and Southeast Asia, revealing stark regional differences in sea-level rise rates. These patterns could only be reconciled by a far more substantial North American ice melt during the late glacial-to-early post-glacial transition.
Global perspective matters for climate science and policy
“This research provides a stark reminder of the complexities of our climate system and melting ice sheets,” said Mukherjee, reflecting a broader scientific lesson: to understand past climate changes—and to forecast future ones—we must assemble a truly global dataset. The study underscores the value of integrating regional records into a coherent global framework, rather than treating oceans as a sum of isolated signals. The implications extend to contemporary climate risk assessments, where the pace and sources of ice loss influence expectations for sea-level rise and its societal impacts.
Funding and collaboration
The project was funded by the U.S. National Science Foundation and involved collaborators from the University of Ottawa, Memorial University (Canada), Maynooth University (Ireland), and the University of South Florida. It reflects a cross-border, cross-continental effort to illuminate how ice sheets—from North American shelves to distant ice masses—have shaped our world’s seas. As science advances, these findings remind policymakers and researchers to consider a broader data network when evaluating future coastal risk in a warming climate.
