Samples drilled from deep beneath the sea have revealed just how much global sea levels changed following the last ice age.
Melting ice caps in North America, Antarctica and Europe caused sea levels to rise quickly as temperatures warmed after the last ice age. But researchers have lacked robust geological data from this period, so how much sea levels climbed was unknown.
Now, new geological data show that sea levels rose about 125 feet (38 meters) between 11,000 and 3,000 years ago, according to a study published March 19 in the journal Nature. The findings could help scientists and policymakers understand what to expect as today’s ice sheets respond to a warming climate.
In pursuit of these records, an international team of scientists turned to a relatively shallow area of the North Sea covering “Doggerland,” the land bridge that connected the U.K. to mainland Europe until about 7000 years ago. The researchers drilled samples of peat, or partially decomposed plant matter, from beneath the sea.
Doggerland was home to coastal marshlands during the ice age, but rising waters and marine sediments submerged and compressed the marshes as sea levels rose. The team analyzed the different elements and types of microalgae in the peat to work out how sea levels changed.
All told, sea levels rose about 125 feet over the course of 8,000 years following the end of the last ice age. Most of this increase took place in two phases. The first occurred around 10,300 years ago and was due purely to an increase in meltwater. The second phase hit around 8,300 years ago and was driven by both ice melt and an influx of water from lakes atop melting glaciers.
Rates of sea level rise peaked at more than 0.4 inch (10 millimeters) per year, or about 40 inches (1 meter) per century. For context, sea levels are currently rising by 0.1 to 0.2 inch (3 to 4 mm) per year and will likely increase to between 0.2 and 0.4 inch (4 to 9 mm) per year by the end of the century, according to the Intergovernmental Panel on Climate Change (IPCC).
“Of course, the consequences of sea level rise are now far greater due to the growth in population and the current presence of infrastructure, cities and economic activity in areas that will be vulnerable to the effects of climate change in the future,” study co-author Sarah Bradley, a researcher in the School of Geography and Planning at the University of Sheffield in the U.K., said in a statement.
Understanding how sea levels changed during past periods of rapid warming could help scientists improve existing models of sea level rise, the researchers wrote. Paleorecords like the ones described in the new study complement more recent data from modern instruments on how Earth responds to various changes.
“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,” Marc Hijma, a geologist at Deltares, a technical institute in the Netherlands, said in the same statement. “This provides insights for both scientists and policymakers, so that we can better prepare for the impacts of current climate change, for example by focusing on climate adaptation.”
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