Sea levels rose sharply at the end of the last ice age, as ice sheets in North America, Antarctica and Europe melted rapidly. (Image credit: PHOTOSTOCK-ISRAEL/SCIENCE PHOTO LIBRARY via Getty Images)
Samples pulled from the deep sea have shown how dramatically sea levels have changed since the last ice age.
Melting ice caps in North America, Antarctica and Europe caused sea levels to rise rapidly as temperatures began to rise after the last ice age. However, scientists lacked reliable geological data for this period, so sea levels remained unclear.
Now, new geological evidence suggests that sea levels rose by 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 modern ice sheets respond to climate change.
To find this data, an international team of scientists turned to a relatively shallow area of the North Sea that encompasses “Doggerland,” a land bridge that connected Britain to mainland Europe some 7,000 years ago. The researchers drilled for samples of peat, or partially decomposed plant material, from the sea floor.
Doggerland was home to coastal peatlands during the Ice Age, but rising waters and marine sediments have flooded and compressed these peatlands as sea levels have risen. The team analysed different elements and microalgae species in the peat to find out how sea levels have changed.
Overall, sea levels have risen about 125 feet in the 8,000 years since the end of the last ice age. Most of this rise occurred in two stages. The first stage occurred about 10,300 years ago and was caused solely by increased meltwater. The second stage occurred about 8,300 years ago and was caused by both melting ice and inflows from lakes on the melting glaciers.
The rate of sea level rise peaked at more than 0.4 inches (10 millimeters) per year, or about 40 inches (1 meter) per century. By comparison, sea levels are currently rising at 0.1 to 0.2 inches (3 to 4 mm) per year and are likely to increase to 0.2 to 0.4 inches (4 to 9 mm) per year by the end of the century, according to the Intergovernmental Panel on Climate Change (IPCC).
“It's clear that the impacts of sea level rise are now much more severe because of the increase in population and existing infrastructure, cities and economic activity in areas that will be vulnerable to the impacts of climate change in the future,” said study co-author Sarah Bradley, a research fellow at the School of Geography and Planning at the University of Sheffield in the UK.
Understanding how sea levels have changed during past periods of rapid warming could help scientists improve existing models of sea level rise, the researchers note. Paleorecords like those discussed in the new study complement more recent data from modern instruments about how the Earth responds to various changes.
“Based on detailed data from the North Sea region, we can now better understand the complex interactions between ice sheets, climate and sea level,” said Mark Hijma, a geologist at Deltares, a technical institute in the Netherlands, in the same statement. “This provides insights for both scientists and policymakers, allowing us to better prepare for the impacts of ongoing climate change, for example by focusing on climate adaptation.”
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