As they excavated a nearly mile-long core of ice from Camp Century, the name of the secret nuclear base, U.S. scientists were puzzled by the discovery of light and dark bands in the ice. They turned to Willi Dansgaard, a Danish scientist who had devised a method to date ice that fell as snow thousands of years ago by measuring the density of isotopes in each layer of snowfall. Water molecules that fall in winter have more of the heavier oxygen-18 isotopes than those that fall in summer. Dansgaard deduced that the core retrieved from Camp Century was stratified with 100,000 years of snowfall, arranged in seasonal layers that could be read like lines on a calendar.
As fallen snow solidifies into ice, it traps microscopic bubbles of air along with traces of past climates. Ash from ancient forest fires, or pollen, can help scientists reconstruct what life on Earth was like thousands of years ago.
The world’s frozen places are an immense library of our planet’s history.
The Camp Century ice core caused a sensation. It was the first to reach bedrock; the New York Times called it “the most rewarding hole ever drilled.” But until recently, no one had examined the soil sample that came up with it. As The Washinton Post reported in March 2021, Andrew Christ, a geologist at the University of Vermont, has determined that the soil — full of the frozen remains of ancient plants — was last exposed to the air less than 1 million years ago. If Greenland had been ice-free that recently (geologically speaking), then surely it could become so again.
Christ’s discovery is a warning. The mechanisms that could cause the ice sheet’s collapse are extremely delicate. The Camp Century core not only tells us about the world as it once was, but also it foreshadows the world to come if our efforts to mitigate climate change fail.
The rapid melting of the Greenland ice sheet is an unfolding environmental disaster. As The Washinton Post reported, without drastic cuts to emissions, Greenland could lose 35,900 billion metric tons of ice by 2100. This would significantly contribute to the three feet of sea-level rise predicted to occur by the end of the century, which would disrupt ocean currents and make storms and hurricanes more destructive.
But melting ice also entails a deeper loss: our cultural memory.
The antique particles locked away in ice tell a profoundly human tale. It isn’t just pollen or volcanic tephra. Parts of our history are archived as well. There are stories of calamity: in Alpine glaciers, a gap between trace layers of lead bears witness to the cessation of lead smelting during the Black Death; the devastation of the New World by European diseases is remembered in Antarctic ice cores that record a decline in atmospheric carbon in the 100 years after 1492, as the indigenous population collapsed and agricultural land briefly reverted to forest. There are stories that weave human achievement with geological processes. Traces of tephra recall the 1815 eruption of Indonesia’s Mount Tambora, which cast a pall of bleak weather over Europe. The “year without summer” that followed inspired Mary Shelley’s “Frankenstein”; John Keats’s rhapsodic poem “To Autumn” was a sign of relief at the restoration of the seasons.
The story of the modern age is written into the ice. An increase in black carbon and fly ash (a residue from burning coal) marks the onset of the Industrial Revolution; a sudden surge in synthesized nitrogen dates the invention of the Haber-Bosch fertilizer process in 1914. Radionuclides inscribe the nuclear weapons tests in the 1950s.
The shift from chlorofluorocarbons to hydrofluorocarbons at the end of the 1980s marks a change in environmental consciousness, but the massive acceleration in anthropogenic carbon since the 1990s indicates that there is still a long way to go. Even the Covid-19 pandemic will be recorded, as global carbon emissions fell by 7 per cent in 2020.
A frozen Alexandria?
Spending time in the library of ice reminds us that our history is bound up with that of the planet. As that library comes under ever increasing risk, we should remember the fate of another great library. Legend tells that the Library of Alexandria burned to the ground, but the truth is less spectacular. As the Roman Empire fell into decline, people simply neglected to protect and preserve the fragile papyrus manuscripts that were stored in the Library of Alexandria. Gone with it were the greatest treasures of the ancient world: hundreds of years of civilizations’ stories, memories, knowledge and wisdom.
The greatest library in history was lost to neglect. Unless we act now, the library of ice will meet the same fate.
This article originally appeared in the Washington Post on 7 April 2021
Image credit: Getty/Gerald Corsi
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