Today, almost 98% of Greenland is covered in ice – but new research suggests that the continent was virtually ice-free less than a million years ago.
Over the years, opinions have changed about whether Greenland has been continuously covered by ice since the beginning of the Pleistocene about 2.7 million years ago. But a new fossil discovery described in a study published August 5 in the Journal PNAS“provides the first direct evidence that the centre – and not just the edges – of the Greenland ice sheet has melted away in the recent geological past,” it says in a opinion from the University of Vermont.,
“Our new data provide the strongest confirmation yet that the ice in the center of the island has disappeared and been replaced by a tundra ecosystem,” lead study author Paul Bierman, a geologist at the University of Vermont, told Live Science.
To make this discovery, the research team re-examined a sample of an ice core taken in 1993. They found a wealth of fossils, including willows, mushrooms and insect body parts. The most spectacular find, however, was a pristinely preserved Arctic poppy seed.
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The team was surprised by the findings. “The original plan was to use the sample to measure isotopes (to date using the carbon method). We didn’t know we would find fossils,” Bierman said.
An important piece of evidence was a specimen of rock moss ((Selaginella rupestris)which now only survives on sandy and rocky soils. “They need the things that all plants need to grow, and they can’t get those on an ice sheet,” Halley Mastro, a doctoral student at the University of Vermont and co-author of the study, told Live Science. “They just wouldn’t grow.”
A Study 2016 of the core suggested that the current Greenland ice sheet was a maximum of 1.1 million years old. They also estimated that the loss of ice at one location – called GISP2 – would mean that 90 percent of Greenland would have been ice-free at that time.
Another core sample recovered from the northwest coast of Greenland in 1966 analyzed by Bierman and an international team in 2019They found several fossils – including seeds, twigs and insect body parts – that indicate that this part of Greenland has been ice-free for the past 500,000 years.
The latest study shows that central Greenland was also ice-free at some point in the last 1 million years. The landscape, which is now covered by a 3.2-kilometer-thick layer of ice, was home to a complete tundra ecosystem with flowers and possibly even small trees, the statement said.
The core, re-examined by Bierman and Mastro in 1993, was stored for over 30 years at the National Science Foundation’s Ice Core Facility in Colorado and virtually ignored.
“The ice portion of the core has been extensively studied,” Bierman said. “The people who took the ice cores didn’t think much about what was underneath. After a series of analyses of the sediment, it was put in a bag on a shelf. We wouldn’t have known we needed to check this if we didn’t already have a project looking at sediment under the ice.”
The realization that Greenland was once ice-free has implications for the present.
An ice-free Greenland was possible at lower levels of carbon dioxide in the atmosphere than today. So there is a possibility that Greenland could become ice-free again, which would lead to a drastic rise in sea levels.
“It will take decades, if not centuries, for the ice to completely disappear, but most of the sea level rise is occurring in Greenland – more than anywhere else,” Bierman said.
However, there may be hope. “Nature has carried away this ice sheet in the past and it has come back,” he said.
