When Greenland was green: Ancient soil from beneath a mile of ice offers warnings for the future Premium

400k yrs ago, Greenland was mostly ice-free as evidence suggests a forest of spruce trees covered the south.

About 400,000 years ago, large parts of Greenland were ice-free. Scrubby tundra basked in the Sun’s rays on the island’s northwest highlands. Evidence suggests that a forest of spruce trees, buzzing with insects, covered the southern part of Greenland. Global sea level was much higher then, between 20 and 40 feet above today’s levels. Around the world, land that today is home to hundreds of millions of people was under water.

Scientists have known for a while that the Greenland ice sheet had mostly disappeared at some point in the past million years, but not precisely when.

In a new study in the journal Science, we determined the date, using frozen soil extracted during the Cold War from beneath a nearly mile-thick section of the Greenland ice sheet.

The timing – about 416,000 years ago, with largely ice-free conditions lasting for as much as 14,000 years – is important. At that time, Earth and its early humans were going through one of the longest interglacial periods since ice sheets first covered the high latitudes 2.5 million years ago.

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The length, magnitude and effects of that natural warming can help us understand the Earth that modern humans are now creating for the future.

In July 1966, American scientists and U.S. Army engineers completed a six-year effort to drill through the Greenland ice sheet. The drilling took place at Camp Century, one of the military’s most unusual bases – it was nuclear-powered and made up of a series of tunnels dug into the Greenland ice sheet.