How much did sea levels rise after the last ice age? Alarming new clues revealed

The Earth is exposed to restless forces that are never still or settled. Over thousands of years, it has shifted, cracked, and reformed itself in ways both violent and gradual.

Ice has come and gone, swallowing landscapes and then revealing them again. And through it all, the sea has kept its own record – rising, falling, shaping coastlines, and erasing entire worlds.

Today, as melting ice sheets push ocean levels higher, scientists are looking back to a time when the planet last emerged from an ice age and experienced changes in sea level.

A recent study published in the journal Nature provides a rare and detailed look at how sea levels rose during the early Holocene epoch, about 11,700 years ago.

​Led by researchers from Deltares, Utrecht University, and the Royal Netherlands Institute for Sea Research (NIOZ), the study reveals the staggering speed at which ice sheets once melted, and offers unsettling parallels to our modern climate crisis.​

Land was swallowed by sea-level rise

There was a time when the North Sea was not a sea at all. It was a vast, habitable land, home to rivers, forests, and early human settlements.

That land, Doggerland, now rests beneath the ocean, a drowned world preserved in layers of sediment. Scientists have long known that rising waters consumed it, but exactly how fast and how much the sea rose remained uncertain – until now.

By analyzing layers of ancient peat and borehole samples from the seabed, researchers reconstructed sea-level changes with remarkable precision. Their findings show that sea levels did not rise steadily. Instead, there were sudden surges – two in particular – that transformed the landscape in dramatic ways.

A planet in flux

The end of the last ice age triggered a global transformation. As temperatures increased, glaciers that had once towered over North America and Europe began to shrink. Some of this meltwater trickled into the oceans slowly, but at times, vast quantities were released all at once.

This study identified two major pulses of rapid sea-level rise, one around 10,300 years ago and another at 8,300 years ago. During these peak periods, waters rose at rates exceeding one meter per century, which is comparable to the worst-case projections for the future.

One of the reasons for the rapid rise was a catastrophic drainage event from Lake Agassiz–Ojibway, an immense glacial lake in North America. When its ice dams collapsed, an enormous surge of freshwater spilled into the ocean, contributing to one of the most rapid rises in recorded history.

These events reshaped coastlines, submerged settlements, and forced human populations to adapt or move.

Mapping ancient sea-level rise

Reconstructing ancient sea levels is no small feat. The research team compiled 88 sea-level data points from the North Sea and removed the effects of glacial isostatic adjustment – the slow rebounding of land after the weight of ice sheets disappears.

The result, a much clearer picture was obtained of how much water was added to the oceans and how quickly this happened.

Earlier estimates of sea-level rise between 11,000 and 3,000 years ago have ranged from 32 to 55 meters (105 and 180 feet). The current study refined these previous estimates, narrowing down the total rise to approximately 38 meters. This updated figure provides crucial insight into how Earth’s climate system responds to rapid warming.

Another key finding involved the role of thermosteric effects – the expansion of seawater as it warms. While not the dominant factor, this process still contributed to the overall rise, adding yet another layer to the complex relationship between temperature and sea level.

The speed of change

In just a few thousand years, Doggerland went from a thriving environment to an underwater relic. The forests disappeared. The rivers merged with the sea. Entire communities were destroyed or displaced.

The lesson from this is that the Earth doesn’t wait. It doesn’t pause for human civilization to catch up. When the conditions are right, changes happen fast.

The peak rates of early Holocene sea-level rise reached nearly 9 mm (0.35 inches) per year – a number that is concerning to anyone following modern climate projections. The ice sheets of Greenland and Antarctica are already melting rapidly.

The oceans are rising. And the conditions that led to rapid change in the past are aligning once again.

A warning from the past

Marc Hijma, a geologist at Deltares and the lead author of the study, spoke to the broader significance of these findings.

“With this groundbreaking research, we have taken an important step towards a better understanding of sea level rise after the last ice age,” said Hijma.

“By drawing on detailed data for the North Sea region, we can now better unravel the complex interaction between ice sheets, climate, and sea level. This provides insights for both scientists and policymakers, so that we can prepare better for the impacts of current climate change, for example by focusing on climate adaptation.”

The implications are massive. The Intergovernmental Panel on Climate Change (IPCC) warns that, if current trends persist, sea levels could rise by several meters by 2300. Some projections suggest an increase of more than a meter per century – on par with what the ancient world experienced after the last ice age.

The big difference now is that today’s coastlines are home to cities, industries, and billions of people. The stakes are infinitely higher.

Learning from the water’s edge

Modern satellites can track sea-level rise with incredible accuracy. Yet, even with all our technology, there is no substitute for the deep records stored in the Earth itself.

The seabed holds a memory that no human archive can match – a history of climate, ice, and water that stretches back through time.

The data from Doggerland is more than just numbers and graphs. It’s a message from a world that no longer exists. It tells us what happens when ice melts too fast, when seas rise unchecked, and when the planet reshapes itself with little regard for what stands in the way.

This research is not just about the past – it’s a glimpse into our future. What happened once can happen again. The only difference is whether we choose to listen.

The study was published in the journal Nature.

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