The Earth’s climate system is a complex interplay between the ocean, atmosphere, and cryosphere, a relationship that underwent profound transformation during the last deglaciation—the transition from the last Ice Age into the current interglacial period. This interval, spanning approximately 10,000 to 7,000 years ago, holds critical clues for understanding future climate dynamics, especially in the context of accelerating contemporary climate change. Among the multifaceted components of this system, sea-level change serves as a crucial integrator, linking ice melt, ocean circulation, and atmospheric conditions. However, progress in fully elucidating the ice sheet–sea-level budget from the Last Glacial Maximum (LGM) has been impeded by the limited temporal granularity and spatial coverage of relative sea-level records.
In groundbreaking research published in Nature Geoscience, Mukherjee and colleagues present an innovative relative sea-level record from the Mississippi Delta, compiled using radiocarbon-dated basal peat deposits. This dataset extends back roughly 10,000 years and provides a robust temporal constraint for sea-level changes during the critical closing phase of the last deglaciation, specifically from 9,000 to 7,000 years ago. When combined with the most rigorous and geographically diverse relative sea-level data available worldwide, this comprehensive record challenges established paradigms regarding the sources and magnitude of ice melt during this pivotal era.
Leveraging advanced geophysical modeling techniques, the research team demonstrated that the integrated data strongly favor a scenario involving approximately 14 meters of sea-level equivalent ice melt originating from North America during this interval. This figure substantially exceeds previous estimates by 4 to 10 meters and suggests a dominant North American contribution to global sea-level rise at the end of the deglaciation. Intriguingly, their modeling reveals that the Antarctic ice sheet’s contribution was markedly smaller, accounting for less than a third of the total ice melt volume hypothesized by earlier models.
This substantial revision of the deglacial ice history compels a reassessment of several interconnected climatic events. Notably, the rapid meltwater input from North American ice sheets likely precipitated the collapse of the saddle region between the two major ice domes over Hudson Bay—a structural configuration that had persisted for millennia. The ensuing destabilization triggered abrupt and regionally significant cooling events around 8,200 years ago, a phenomenon long recognized in paleoclimate proxies but hitherto poorly understood in terms of its ice sheet antecedents.
The study’s findings also bear significant implications for understanding the Atlantic Meridional Overturning Circulation (AMOC), a cornerstone of global ocean circulation and climate regulation. The influx of freshwater derived from melting North American ice sheets would have imposed a powerful perturbation on AMOC, influencing its sensitivity and potentially contributing to the abrupt climatic oscillations documented during the early Holocene. This freshwater forcing mechanism underscores the inherent vulnerability of large-scale oceanic conveyor belts to rapid cryospheric changes, a concern with direct analogues in our rapidly warming present.
Methodologically, the authors employed radiocarbon dating of basal peat as a novel proxy to constrain relative sea-level positions. This approach benefits from both high temporal resolution and precise depositional context, enabling more accurate reconstruction of post-glacial sea-level rise than traditional records based on coral reefs or sediment cores. By mapping these basal peats across the Mississippi Delta, the team was able to establish a refined chronology of sea-level changes that captures the nuances of ice sheet dynamics and regional glacio-isostatic adjustments.
The incorporation of these new empirical data into numerical geophysical models was pivotal. The models accounted for gravitational, elastic, and viscoelastic responses of the Earth’s crust to changing ice loads, including spatially variable lithospheric thickness and mantle viscosity. This modeling sophistication allowed the disentanglement of the complex interplay between local tectonics, regional uplift, and global sea-level trends, leading to more reliable estimates of ice volume loss.
Moreover, the study’s integrated approach illuminated spatial patterns of relative sea-level change that are consistent with the dominant influence of North American ice melt. Sites across the Atlantic coastline, from the Gulf of Mexico to Newfoundland and Western Europe, exhibit coherent signals that support the elevated meltwater volumes inferred by the models. Such spatial coherence enhances confidence in the reconstructed ice histories and refines our understanding of how meltwater routing and redistribution impacted ocean circulation and climatic feedbacks.
These results also rekindle debates regarding the Antarctic ice sheet’s stability during the late deglaciation. While some geological records hint at episodes of rapid Antarctic ice loss, the new modeling suggests a comparatively minor contribution relative to the North American sources during the critical 9,000–7,000-year interval. This finding refocuses attention on North America as the primary driver of sea-level rise and associated climatic phenomena during this phase.
The implications of these discoveries extend far beyond academic curiosity. Improved reconstructions of past ice sheet behavior inform projections of contemporary ice dynamics and potential sea-level rise under anthropogenic warming. Understanding the magnitude and pace at which huge ice masses can disintegrate is crucial for anticipating the trajectories of modern ice sheets, including Greenland and Antarctica, and their global impact. This study exemplifies how paleoclimate research can guide policy and adaptation strategies by refining physical models of ice sheet sensitivity.
Importantly, the refined chronology of North American ice melt provides context for abrupt climate events recorded in ice cores, marine sediments, and terrestrial proxies worldwide. Recognizing the timing and scale of meltwater pulses enhances our ability to link physical ice sheet processes with atmospheric composition changes, oceanic circulation shifts, and biospheric responses. This integrative perspective is essential for reconstructing Earth’s climate system operation during periods of rapid change.
The sophisticated interplay highlighted by this research also underscores the critical role of regional geological settings in modulating global signals. The Mississippi Delta, with its rich sedimentary archives and dynamic depositional framework, emerges as a vital natural laboratory for sea-level studies. By combining field-based proxies with cutting-edge modeling, this study sets a new standard for coupling empirical data with theory in paleoclimate science.
Furthermore, the research calls for reexamination of conventional ice sheet reconstructions used in climate models, advocacy likely to stimulate further interdisciplinary collaboration. Incorporating more accurate ice volume histories into simulations will improve fidelity in predicting the interactions among cryospheric, marine, and atmospheric systems under future forcing scenarios. This will be particularly important for refining regional climate projections and understanding feedback mechanisms involving ice sheets and ocean circulation.
In sum, the present work by Mukherjee and colleagues represents a landmark advancement in decoding the Earth’s last deglaciation puzzle. By illuminating North America’s outsized role in sea-level rise and ice sheet dynamics, the research recalibrates our understanding of past climate system behavior and enhances predictive capabilities. As the planet faces unprecedented challenges from human-induced climate shifts, such deep-time insights are invaluable for crafting resilient futures grounded in the lessons of Earth’s climatic past.
Subject of Research: Sea-level rise and ice sheet dynamics during the last deglaciation, with a focus on North American ice sheets.
Article Title: Sea-level rise at the end of the last deglaciation dominated by North American ice sheets.
Article References:
Mukherjee, U., Vetter, L., Milne, G.A. et al. Sea-level rise at the end of the last deglaciation dominated by North American ice sheets. Nat. Geosci. (2025). https://doi.org/10.1038/s41561-025-01806-0
Image Credits: AI Generated
