Researchers led by Brown University have developed a new model that sheds light on a massive sea level rise event at the end of the last ice age. This new understanding of Meltwater Pulse 1a reveals interconnected melting patterns across the globe, which may hold key insights for predicting future sea level changes.
Around 14,500 years ago, at the tail end of the last ice age, planet Earth experienced a sudden and dramatic sea level rise of up to 65 feet in just 500 years. Known as Meltwater Pulse 1a (MWP-1a), this cataclysmic event has puzzled scientists for decades. Researchers have debated which ice sheets were responsible for the immense influx of meltwater. Now, thanks to a new study led by Brown University, we have a clearer picture.
Supported by a grant from the National Science Foundation, the researchers have used an advanced physical model of sea-level dynamics to reconstruct MWP-1a. This innovative work, published in Nature Geoscience, reveals that the event was initiated by modest melting over North America, which triggered a global cascade of ice loss, affecting continents from Europe to Antarctica.
“We see a distinct interhemispheric pattern of melting associated with this catastrophic sea level rise in the past,” Allie Coonin, a doctoral candidate in Brown’s Department of Earth, Environmental and Planetary Sciences, who led the research, said in a news release. “That tells us that there’s some sort of mechanism that is responsible for linking these ice sheets across hemispheres, and that’s important for how we understand the stability of the Greenland and West Antarctic ice sheets today.”
Unlocking the Ice Age’s Secrets
To reconstruct this ancient event, scientists combined sea level records from ancient shorelines and ocean sediments, identifying timing and magnitude through fossil corals and other biological markers. They then applied a technique known as “sea level fingerprinting” to identify which ice sheets contributed to the rise.
This method considers the uneven distribution of global sea level changes — caused by the varying gravitational pulls of melting ice sheets and the Earth’s crustal rebound.
In their latest study, the team incorporated both elastic and viscous deformation of the Earth’s crust — an enhancement over previous models. This approach revealed that the viscous response, previously thought to be relevant only over millennia, can indeed play a significant role within mere decades or centuries.
“People have shown that this viscous deformation can be important on timescales of decades or centuries,” added co-author Harriet Lau, an assistant professor in Brown’s Department of Earth, Environmental and Planetary Sciences. “Allie was able to incorporate that into her modeling of solid Earth deformation in the context of sea level physics.”
A More Nuanced Scenario
The updated model diverges significantly from earlier reconstructions, offering a more nuanced and globally linked scenario.
Modest melting of the Laurentide ice sheet over North America initiated the event, contributing about 10 feet to sea level rise. This was followed by more significant melting of ice sheets over Eurasia and West Antarctica, adding approximately 23 and 15 feet respectively.
This interconnected narrative challenges prior theories that attributed MWP-1a to a single source and demonstrates the significant role of using advanced physics in modeling ice sheet dynamics.
“We show that using the appropriate physics makes a big difference in sea level predictions,” Coonin added.
Implications for the Future
Although more research is needed to fully understand the mechanisms linking disparate ice sheets, these findings suggest that contemporary ice loss, such as the rapid melting of Greenland’s ice sheet, may influence ice dynamics far afield, including the much larger Antarctic ice sheet.
The implications of this study are far-reaching, helping scientists to better predict future sea level rises and develop more effective responses to the ongoing challenges of climate change.
The study, co-authored by Sophie Coulson of the University of New Hampshire, offers essential insights into how interconnected global ice melt can drive significant changes in sea levels, directly influencing our understanding of both past and future climate scenarios.
Source: Brown University