About 400,000 years ago, much of Greenland was ice-free. Sun-drenched tundra in the highlands of the northwestern part of the island. The proof is spruce forest Insect-infested trees covered southern Greenland.At that time, the world’s sea level was much higher, between 20 and 40 feet surpass today’s level. All over the world, lands where hundreds of millions of people live today have been submerged.
Scientists have known for some time that the Greenland ice sheet nearly disappeared at some point on Earth. millions of years agobut not exactly when.
In a new study in scientific journalsI used frozen soil to set the date extracted during the cold war From beneath an almost mile-thick portion of the Greenland ice sheet.
Let’s take a quick look at the evidence beneath the Greenland ice sheet and the lessons we can learn from it.
About 416,000 years ago, the timing is significant as it remained largely ice-free for 14,000 years.Then the earth and its early humans They were experiencing one of the longest glacial periods since ice sheets first covered high latitudes 2.5 million years ago.
The length, scale and impact of that natural warming help us understand the planet we are creating for the future.
A world preserved under ice
In July 1966, American scientists and Army engineers completed a six-year effort. Drill through the Greenland ice sheet. Excavations were carried out at: camp centuryone of the military’s most unusual bases, it is by nuclear It consists of a series of tunnels dug into the Greenland ice sheet.
Training grounds in northwest Greenland were underground, 220 kilometers from the coast on 4,560 feet of ice. Once the ice bottom was reached, the team continued drilling another 12 feet into the frozen, rocky soil below.
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In 1969, geophysicist Willi Dunsgaard’s analysis of ice cores at Camp Century revealed the first details of how Earth’s climate changed. changed dramatically Over the past 125,000 years. Long, cold glacial periods of rapid expansion of ice gave way to warm interglacial periods that melted ice, raised sea levels, and flooded coastal regions around the world.
For nearly three decades, scientists paid little attention to Camp Century’s twelve feet of permafrost.a study analyzed the pebbles To understand the bedrock beneath the ice sheet.Another researcher found that, interestingly, frozen soil preserved evidence A warmer time than today. However, few people paid attention to these studies because there was no way to date the material. By the 1990s, the permafrost core had disappeared.
A few years ago, a Danish colleague discovered lost soil buried deep in a freezer in Copenhagen, and we formed an association. international team to analyze this unique frozen climate archive.
In the top sample, we found it to be perfectly preserved. fossil plant—hard evidence that the land far below Camp Century was ice-free at some point in the past—but when was that?
