Evidence of a greener Greenland reveals shocking reality of sea level rise
Greenland, a white expanse of ice spanning an area three times the size of Texas, was not always so barren and frigid. According to a recent study published in the journal Science, a large portion of Greenland was an ice-free tundra landscape – perhaps covered by trees and populated by woolly mammoths – as recently as 416,000 years ago.
This revelation challenges the previous assumption that much of the Greenland ice sheet remained frozen for most of the last two and a half million years.
The discovery, made by an international team of researchers from the University of Vermont (UVM), Utah State University, and fourteen other institutions, highlights the sensitivity of the Greenland ice sheet to moderate warming periods.
Harsh reality
The scientists found that, between 424,000 and 374,000 years ago, Greenland’s ice sheet melted substantially, leading to at least five feet of global sea level rise.
Intriguingly, the atmospheric levels of carbon dioxide, a significant driver of climate change, were lower then than they are today – 280 parts per million (ppm) versus today’s 420 ppm.
This finding indicates that the ice sheet on Greenland may be more sensitive to human-induced climate change than previously understood, rendering it susceptible to irreversible, rapid melting in the upcoming centuries.
Long-lost ice core
The evidence for these startling revelations was unearthed from an unlikely source, a long-lost ice core collected by a secret U.S. Army mission during the Cold War.
Under the guise of the Arctic science station, Camp Century, the Army drilled through 4,560 feet of ice, extracting a twelve-foot-long tube of soil and rock from beneath the icy surface.
This icy sediment, initially lost in a freezer for decades, was accidentally rediscovered in 2017. Surprisingly, it held not just sediment but also leaves and moss, testaments to an ice-free landscape that might have been a boreal forest.
New understanding of Greenland’s history
Using advanced luminescence technology and rare isotope analysis on the sediment from the ice core, the researchers have painted a dramatically different picture of Greenland’s history.
Until recently, scientists believed Greenland to be a fortress of ice, relatively untouched by melting for millions of years. However, these new techniques allowed the team to create a detailed timeline of Greenland’s thawing, revealing that large portions of the ice sheet melted much more recently than one million years ago.
“It’s really the first bulletproof evidence that much of the Greenland ice sheet vanished when it got warm,” says University of Vermont scientist Paul Bierman, who co-led the new study. The implications of this research are significant, particularly considering the present-day effects of climate change.
Twenty-three feet of potential sea-level rise
Approximately twenty-three feet of potential sea-level rise is stored in Greenland’s ice, placing every coastal region in the world at risk.
The study revealed that the sediment from the Camp Century ice core was exposed to sunlight – indicating an ice-free landscap – before being buried under the ice once more. This discovery was made using a “luminescence signal” within the sediment, which zeros out when exposed to sunlight.
Over time, in the darkness, minerals within the sediment accumulate electrons, forming a kind of geological clock. By examining the amount of these accumulated electrons, the scientists could determine when these sediments were last exposed to the sun. The team at Utah State University conducted these examinations in a specialized dark room, using advanced tools and repeated tests.
Additional insights
In the University of Vermont lab, scientists studied quartz from the Camp Century core. Ratios of beryllium and other isotopes gave the scientists a window onto how long rocks at the surface were exposed versus buried under layers of ice.
This data helped the scientists show that the Camp Century sediment was exposed to the sky less than 14,000 years before it was deposited under the ice, narrowing down the time window when that portion of Greenland must have been ice-free.
Understanding Greenland’s past is not just about rewriting history books. It provides crucial insight into how its giant ice sheet will respond to future warming and how quickly it could melt. This discovery offers robust and precise evidence that Greenland is more sensitive to climate change than previously thought.
“Greenland’s past, preserved in twelve feet of frozen soil, suggests a warm, wet, and largely ice-free future for planet Earth, unless we can dramatically lower the concentration of carbon dioxide in the atmosphere,” says Bierman.
The Camp Century core and its rich data have transformed scientists’ understanding of Greenland’s icy history. “We had always assumed that the Greenland ice sheet formed about two and a half million years ago – and has just been there this whole time and that it’s very stable,” says study co-author Tammy Rittenour. “But this paper shows that it did.”
Implications of the study
While 416,000 years ago, there were no cities hugging coastlines, today, millions of people live in low-lying coastal areas. This makes the potential for a significant sea level rise due to the melting of Greenland’s ice sheet a major concern.
“If we melt just portions of the Greenland ice sheet, the sea level rises dramatically. Most global population centers are near sea level,” explains Rittenour.
The Camp Century study sends a clear warning to the world. It shows that the Greenland ice sheet has a history of melting during periods of moderate warming.
With today’s rapidly increasing atmospheric carbon dioxide levels, the chances of significant and irreversible melting are alarmingly high. The outcome of such an event would be catastrophic, given that Greenland’s ice holds enough water to raise global sea levels by over twenty feet – a disaster for many coastal cities and nations.
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