If the Greenland ice sheet melted away, global sea levels would rise an average of six metres, putting almost every coastal city in the world at risk of major flooding.
Now, a study of an ice core forgotten for more than 50 years has found this is exactly what happened during a recent warm period that occurred within the last million years.
The core was originally extracted in 1966 from Camp Century, a polar Cold War military base that masqueraded as a science station to provide cover for Project Iceworm - a top-secret US Army program to build a network of mobile nuclear missile launch sites beneath the Greenland ice sheet.
The military mission failed, but the science team did complete several important pieces of research, including drilling a 1400m-deep ice core.
Read more about Greenland:
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- Greenland ice melt putting 40 million people at greater risk than previously thought
- The real value of Greenland is in the ice, rather than the minerals
The core was kept in an army freezer before being moved to the University of Buffalo in the 1970s, then to the University of Copenhagen in the 1990s. It was eventually accidentally rediscovered by Danish researchers in 2017.
For the last year, an international team of researchers has been analysing the plant fossils and sediment found in the core to determine their composition and age. They concluded that most, if not all, of Greenland melted at least once during the past million years and that the ground was covered in a blanket of vegetation including moss, lichen, and perhaps even spruce and fir trees.
“Our study shows that Greenland is much more sensitive to natural climate warming than we used to think - and we already know that humanity's out-of-control warming of the planet hugely exceeds the natural rate,” said team member Dr Andrew Christ, of the University of Vermont.
“Ice sheets typically pulverise and destroy everything in their path. But what we discovered was delicate plant structures - perfectly preserved. They're fossils, but they look like they died yesterday. It's a time capsule of what used to live on Greenland that we wouldn't be able to find anywhere else."
Reader Q&A: Are some plants better than others at sucking up carbon dioxide?
Asked by: Roy Musselbrook, Ramsgate
Plants use carbon dioxide (CO₂) during photosynthesis to make glucose. It takes six molecules of CO₂ to make every molecule of glucose, and this basic building block is then used for energy and to make the structure of the plant itself. This biochemical reaction is the same for all plants, but the faster a plant grows, the more carbon dioxide it will use up per second. By that measure, bamboo might be the best at sucking up CO₂. However, fast-growing plants tend not to live long and when a plant dies, all the carbon in the plant is broken down by insects, fungi and microbes and released as CO₂ again.
So the plants that are considered the most adept at locking away carbon dioxide from the atmosphere are the longest-living ones, with the most mass – hardwood trees. It’s all temporary though. Eventually every plant returns all the carbon dioxide it uses back to the atmosphere.
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