The mystery of Greenland's icy history could help us survive climate change

Eighty percent of Greenland is covered by a wall of ice thousands of feet thick. If the wall melted completely, the water it contains would be enough to raise sea levels by over 20 feet.

Greenland's ice has grown and shrunk over time, driven by variations in the climate, but mapping out the history of those changes is a remarkably difficult task. The deeper that researchers dig into Greenland's past, the more tangled the icy narrative becomes.

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Global warming, climate change impacting Patagonia's massive glaciers
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SANTA CRUZ PROVINCE, ARGENTINA - NOVEMBER 29: Ice calves from the Northern wall of the Perito Moreno glacier in Los Glaciares National Park, part of the Southern Patagonian Ice Field, on November 29, 2015 in Santa Cruz Province, Argentina. Certain areas of glacial ice take on a bluish hue due to light refraction. The Southern Patagonian Ice Field is the third largest ice field in the world. The majority of the almost 50 large glaciers in Los Glaciares National Park have been retreating during the past fifty years due to warming temperatures, according to the European Space Agency (ESA). The United States Geological Survey (USGS) reports that over 68 percent of the world's freshwater supplies are locked in ice caps and glaciers. The United Nations climate change conference begins November 30 in Paris. (Photo by Mario Tama/Getty Images)
SANTA CRUZ PROVINCE, ARGENTINA - NOVEMBER 28: Runoff cascades from the edge of Heim glacier in Los Glaciares National Park, part of the Southern Patagonian Ice Field, the third largest ice field in the world, on November 28, 2015 in Santa Cruz Province, Argentina. The majority of the almost fifty large glaciers in the park have been retreating over the past fifty years due to warming temperatures, according to the European Space Agency (ESA). The United States Geological Survey reports that over 68 percent of the world's freshwater supplies are locked in icecaps and glaciers. The United Nations climate change conference begins November 30 in Paris. (Photo by Mario Tama/Getty Images)
SANTA CRUZ PROVINCE, ARGENTINA - NOVEMBER 27: The Perito Moreno glacier stands in Los Glaciares National Park, part of the Southern Patagonian Ice Field, the third largest ice field in the world, on November 27, 2015 in Santa Cruz Province, Argentina. Certain areas of glacial ice take on a blueish hue due to light refraction. The majority of the almost fifty large glaciers in the park have been retreating over the past fifty years due to warming temperatures, according to the European Space Agency (ESA). The United States Geological Survey (USGS) reports that over 68 percent of the world's freshwater supplies are locked in icecaps and glaciers. The United Nations climate change conference begins November 30 in Paris. (Photo by Mario Tama/Getty Images)
SANTA CRUZ PROVINCE, ARGENTINA - NOVEMBER 28: Runoff cascades from the edge of Heim glacier in Los Glaciares National Park, part of the Southern Patagonian Ice Field, the third largest ice field in the world, on November 28, 2015 in Santa Cruz Province, Argentina. The majority of the almost fifty large glaciers in the park have been retreating over the past fifty years due to warming temperatures, according to the European Space Agency (ESA). The United States Geological Survey reports that over 68 percent of the world's freshwater supplies are locked in icecaps and glaciers. The United Nations climate change conference begins November 30 in Paris. (Photo by Mario Tama/Getty Images)
SANTA CRUZ PROVINCE, ARGENTINA - NOVEMBER 27: The Perito Moreno glacier stands in Los Glaciares National Park, part of the Southern Patagonian Ice Field, the third largest ice field in the world, on November 27, 2015 in Santa Cruz Province, Argentina. The majority of the almost fifty large glaciers in the park have been retreating over the past fifty years due to warming temperatures, according to the European Space Agency (ESA). The United States Geological Survey (USGS) reports that over 68 percent of the world's freshwater supplies are locked in icecaps and glaciers. The United Nations climate change conference begins November 30 in Paris. (Photo by Mario Tama/Getty Images)
SANTA CRUZ PROVINCE, ARGENTINA - NOVEMBER 29: The Perito Moreno glacier stands in Los Glaciares National Park, part of the Southern Patagonian Ice Field, on November 29, 2015 in Santa Cruz Province, Argentina. Certain areas of glacial ice take on a bluish hue due to light refraction. The Southern Patagonian Ice Field is the third largest ice field in the world. The majority of the almost 50 large glaciers in Los Glaciares National Park have been retreating during the past fifty years due to warming temperatures, according to the European Space Agency (ESA). The United States Geological Survey (USGS) reports that over 68 percent of the world's freshwater supplies are locked in ice caps and glaciers. The United Nations climate change conference begins November 30 in Paris. (Photo by Mario Tama/Getty Images)
SANTA CRUZ PROVINCE, ARGENTINA - NOVEMBER 28: An iceberg broken off from a melting glacier floats in Lake Argentino, which holds runoff water from the Southern Patagonian Ice Field, the third largest ice field in the world, on November 28, 2015 in Santa Cruz Province, Argentina. The majority of the almost fifty large glaciers in the surrounding Los Glaciares National Park have been retreating over the past fifty years due to warming temperatures, according to the European Space Agency (ESA). The United States Geological Survey reports that over 68 percent of the world's freshwater supplies are locked in icecaps and glaciers. The United Nations climate change conference begins November 30 in Paris. (Photo by Mario Tama/Getty Images)
SANTA CRUZ PROVINCE, ARGENTINA - NOVEMBER 29: Melting glacial ice floats in Los Glaciares National Park, part of the Southern Patagonian Ice Field, on November 29, 2015 in Santa Cruz Province, Argentina. Certain areas of glacial ice take on a bluish hue due to light refraction. The Southern Patagonian Ice Field is the third largest ice field in the world. The majority of the almost 50 large glaciers in Los Glaciares National Park have been retreating during the past fifty years due to warming temperatures, according to the European Space Agency (ESA). The United States Geological Survey (USGS) reports that over 68 percent of the world's freshwater supplies are locked in ice caps and glaciers. The United Nations climate change conference begins November 30 in Paris. (Photo by Mario Tama/Getty Images)
SANTA CRUZ PROVINCE, ARGENTINA - NOVEMBER 28: An iceberg broken off from a melting glacier floats in Lake Argentino, which holds runoff water from the Southern Patagonian Ice Field, the third largest ice field in the world, on November 28, 2015 in Santa Cruz Province, Argentina. Certain areas of glacial ice take on a blueish hue due to light refraction. The majority of the almost fifty large glaciers in the surrounding Los Glaciares National Park have been retreating over the past fifty years due to warming temperatures, according to the European Space Agency (ESA). The United States Geological Survey reports that over 68 percent of the world's freshwater supplies are locked in icecaps and glaciers. The United Nations climate change conference begins November 30 in Paris. (Photo by Mario Tama/Getty Images)
SANTA CRUZ PROVINCE, ARGENTINA - NOVEMBER 29: Melted glacial ice floats in Los Glaciares National Park, part of the Southern Patagonian Ice Field, on November 29, 2015 in Santa Cruz Province, Argentina. Certain areas of glacial ice take on a bluish hue due to light refraction. The Southern Patagonian Ice Field is the third largest ice field in the world. The majority of the almost 50 large glaciers in Los Glaciares National Park have been retreating during the past fifty years due to warming temperatures, according to the European Space Agency (ESA). The United States Geological Survey (USGS) reports that over 68 percent of the world's freshwater supplies are locked in ice caps and glaciers. The United Nations climate change conference begins November 30 in Paris. (Photo by Mario Tama/Getty Images)
SANTA CRUZ PROVINCE, ARGENTINA - NOVEMBER 29: The Perito Moreno glacier stands in Los Glaciares National Park, part of the Southern Patagonian Ice Field, on November 29, 2015 in Santa Cruz Province, Argentina. Certain areas of glacial ice take on a bluish hue due to light refraction. The Southern Patagonian Ice Field is the third largest ice field in the world. The majority of the almost 50 large glaciers in Los Glaciares National Park have been retreating during the past fifty years due to warming temperatures, according to the European Space Agency (ESA). The United States Geological Survey (USGS) reports that over 68 percent of the world's freshwater supplies are locked in ice caps and glaciers. The United Nations climate change conference begins November 30 in Paris. (Photo by Mario Tama/Getty Images)
SANTA CRUZ PROVINCE, ARGENTINA - NOVEMBER 28: Runoff cascades from the edge of Heim glacier in Los Glaciares National Park, part of the Southern Patagonian Ice Field, the third largest ice field in the world, on November 28, 2015 in Santa Cruz Province, Argentina. The majority of the almost fifty large glaciers in the park have been retreating over the past fifty years due to warming temperatures, according to the European Space Agency (ESA). The United States Geological Survey reports that over 68 percent of the world's freshwater supplies are locked in icecaps and glaciers. The United Nations climate change conference begins November 30 in Paris. (Photo by Mario Tama/Getty Images)
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Two new studies published today in Nature illustrate the complexity that faces scientists studying changes to the Greenland ice sheet. One study led by Joerg Schaefer finds that Greenland was almost entirely ice free for extended periods of time during the last 2.6 million years. The other study, led by Paul Bierman, finds that there has been a stable ice sheet over East Greenland for the past 7.5 million years.

Taken at face value, the results would seem best suited for a scientific showdown, with contrasting findings leading to an epic Battle Royale fought with data sets and fieldwork over the next several years.

But sorry, you'd better put away the folding chairs and dueling dissertations. That's one matchup that is not gonna happen.

The reality is far more nuanced. And while the results appear to differ greatly, they actually aren't as disparate as their conclusions might lead you to believe.

East Greenland Ice Sheet

Paul Bierman

East Greenland Ice Sheet

East Greenland ice sheet in a Fjord.

Vanishing Ice

Let's start with the study that uncovered Greenland's ice sheet disappearing act.

"It's kind of an awkward situation. Scientifically, it's fascinating and cutting edge and we are happy and proud of what we have done in that respect. But the message really is somber, and I wished the story would have been different," Schaefer says.

Schaefer examined rock cores that had been drilled from under the ice sheet in 1993, looking for a set of isotopes called cosmogenic nuclides that would indicate that the rock had been released from its icy prison at some point in the past.

Cosmic rays are streams of atomic fragments (mostly protons) that bombard the Earth constantly from all directions. When rock is exposed to these cosmic rays, the protons slamming into the rocks' atomic structure can generate the isotopes beryllium-10 and aluminum-26, the cosmogenic nuclides that Schaefer was looking for.

Cosmic rays can only travel through a very small fraction of the Earth's crust. Ice sheets can act as shields, preventing the cosmic rays from interacting with the bedrock. Greenland's ice sheet is over 9,000 feet thick in places, much too thick for the cosmic rays to pass through.

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7 landmarks to visit before climate change ruins them (takepart only do not use)
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7 landmarks to visit before climate change ruins them (takepart only do not use)

Statue of Liberty National Monument, New York

Photo credit: Roberto Machado Noa // Getty​

The Statue of Liberty and Liberty Island, the 14-acre spot of land on which she stands, are dangerously exposed to the elements. In October 2012, Lady Liberty was left largely unscathed by Hurricane Sandy's storm surge, but 75 percent of the island was flooded. "It was total destruction: windows blown out, doors blown out,” said David Luchsinger, superintendent of the statue. Even if the Big Apple dodges another Sandy-size hurricane before 2100, a report published last month in the journal Environmental Research Letters concluded that 750 UNESCO World Heritage sites, including the French statue, could be swamped by climate-change-induced sea level rise unless action on flood defense is taken. "It's relatively safe to say that we will see the first impacts at these sites in the 21st century," lead author Ben Marzeion told The Guardian

Glacier National Park, Montana

Photo credit: kanonsky // Getty

When Congress established Glacier National Park in May 1910, the on-the-nose name was appropriate. At the time, the park was home to more than 150 glaciers. Today just 25 glaciers remain, and those left are fragments of their former icy selves. With temperatures rising because of climate change, scientists predict the park may be glacier-free by 2030. When that sad, seemingly inevitable day arrives, will Congress vote to change the park’s name? Even if it doesn’t, what will our children and grandchildren think of us, the generation that allowed Not-So-Glacier National Park to become a reality?

Venice, Italy

Photo credit: Salvator Barki // Getty

Once described to me by a tour guide as “the one place on the planet everyone must see to disbelieve,” Venice, Italy, a city of 118 islands connected by 409 bridges, now floods more than 100 times every year. The reason? A combination of climate change–induced sea rise and the incremental sinking of the city. Since 1727, the marshlands on which the City of Water rests have descended two feet.

But city officials haven’t taken the bleak prognosis sitting down. MOSES, a $7.3 billion water barrier system, passed its first public test in October 2013 when four of the system’s floodgates were raised and successfully deflected the incoming high tide. When the massive engineering project is completed in 2016, a total of 78 mobile barriers will safeguard the city from acqua alta (Italian for “high water”) for the next hundred years.

Joshua Tree National Park

Photo credit: Carol Polich Photo Workshops // Getty

The clock is ticking on just how long California’s Joshua Tree National Park will be home to its namesake yucca. A 2011 study published in the journal Ecological Applications used climate models to forecast that the desert tree could see its historical range dramatically reduced by 2100. “The established ones may persist for 150 years,” said Ken Cole, an ecologist with the U.S. Geological Survey and the paper’s lead author. “But within 90 percent of its current range, they will be unable to survive,” he added. The reason for the die-off is straightforward: Neither the Joshua Tree nor the yucca moth can survive without each other. “The moth’s larvae depend on the seeds of the yucca plant for food, and the yucca plant can only be pollinated by the yucca moth,” reports Nature Conservancy. And, because climate change will make it too hot for the moth to survive in the desert southwest of the twenty-second century, the pollinator will be forced to migrate north to find a cooler home.

Harriet Tubman underground railroad national monument, Maryland

Photo credit: Twitter

To preserve the Chesapeake Bay swamplands that abolitionist Harriet Tubman once shepherded slaves through en route to the North and to freedom, President Obama designated the area a national monument in March 2013. But, as a local CBS affiliate pointed out at the time, “not even a presidential proclamation” can stop Mother Nature. Though rising sea levels caused by climate change are a global issue, the problem is compounded in the Chesapeake region because its marshlands are simultaneously sinking. A recent study found that water levels in the bay, which is the largest estuary in the U.S., rose by more than a foot in the 1900s and could rise by up to four feet by 2100. “The sea is coming—I think we can win a few years, but not a substantial amount of time,” said a local historian.

Great Barrier Reef, Australia

Photo Credit: Pete Niesen // Getty

Massive enough to be seen from space, the Great Barrier Reef is home to more than 2,900 individual reefs and 900 islands and spans more than 1,600 miles along the northeast coast of Australia. Since 1985 three different threats have eradicated half the coral at this UNESCO World Heritage site: Increased levels of ocean acidification; the crown-of-thorns starfish, which kills coral with a deadly neurotoxin; and warming ocean temperatures, which cause coral bleaching. (Coral can survive a bleaching event, but it’s under more stress than usual and is therefore subject to mortality.) David Curnick, a marine expert with the Zoological Society of London, told The Guardian last year that the future of the reef “lies with the global response to reducing carbon dioxide emissions.” 

Cape Hatteras Lighthouse, North Carolina

Photo credit: Stephen Saks // Getty

Between 1870 and 1999, the shoreline of North Carolina’s Outer Banks eroded nearly 1,400 feet, forcing the National Park Service to relocate the famous Cape Hatteras Lighthouse inland in 1999. In an event dubbed the “Move of the Millennium,” engineers mounted the lighthouse on a tailor-made steel foundation to inch the then-129-year-old structure away from the sea. It took hydraulic machinery 45 seconds to push the lighthouse just five feet, and the entire 2,900-foot move lasted 23 days. Today the lighthouse sits more than a mile from the ocean, a distance that should be safe—for now. If climate change caused all the ice on Earth to melt, as recently visualized in a National Geographic interactive, the entire North Carolina coast would be underwater.

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But Schaefer found cosmogenic nuclides in the bedrock, indicating it had been exposed at some point in the relatively recent past. The specific timing of this exposure is still uncertain. In the most stable scenario, Greenland was nearly ice-free for 280,000 years, before it started freezing over again about 1.1 million years ago. But the data collected by Schaefer and colleagues could also indicate that the ice sheet melted and refroze more than once over the past few million years, which might mean the ice sheet is far less stable than previously assumed.

"It is certainly surprising," Schaefer says of his results. "Most importantly, there is not a single model that can show that Greenland's ice sheet has been gone several times over the past few million years or for one period over that time"

The fact that the current models used by glaciologists appear to be too stable and conservative could be bad news for future estimates of ice loss and sea level rise, which rely on models of what happened in the past to figure out what will happen in the future.

Steady State

"It's a big day for beryllium," Schaefer laughs, noting that Bierman et al's study also used trace amounts of the isotopes to get to their conclusions.

Instead of looking at cores of bedrock from under the ice, Bierman and colleagues looked at records of sediments carried off Greenland by icebergs–sediment cores taken during the early 1990's over 100 kilometers off the southeastern coast.

"If there's a lot of sand and gravel in these cores, that must meant that there were a lot of icebergs floating offshore. And the only way to get icebergs offshore is if you have glaciers on the land," Bierman says.

Bierman isolated beryllium-10 in the core samples and found that the concentration of the isotope dropped over time. That suggests that there was a near-constant ice cover over the land during the 7.5 million year period he and his team studied.

But there are limitations to the findings. Bierman's study looks at averages over long periods of time. Really, really long periods of time. "If the ice sheet disappeared for thousands of years, we probably wouldn't see it," Bierman notes. "We can't see short term changes, but we can see the long-term overall trend."

Related: A look at polar ice melting

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Climate change: A look at polar ice melting
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ILULISSAT, GREENLAND - JULY 22: Seagulls sit on an iceberg on July 22, 2013 in Ilulissat, Greenland. As Greenlanders adapt to the changing climate and go on with their lives, researchers from the National Science Foundation and other organizations are studying the phenomena of the melting glaciers and its long-term ramifications for the rest of the world. In recent years, sea level rise in places such as Miami Beach has led to increased street flooding and prompted leaders such as New York City Mayor Michael Bloomberg to propose a $19.5 billion plan to boost the citys capacity to withstand future extreme weather events by, among other things, devising mechanisms to withstand flooding. (Photo by Joe Raedle/Getty Images)
ILULISSAT, GREENLAND - JULY 25: Pedestrians walk along the road on July 26, 2013 in Ilulissat, Greenland. As Greenlanders adapt to the changing climate and go on with their lives, researchers from the National Science Foundation and other organizations are studying the phenomena of the melting glaciers and its long-term ramifications for the rest of the world. In recent years, sea level rise in places such as Miami Beach has led to increased street flooding and prompted leaders such as New York City Mayor Michael Bloomberg to propose a $19.5 billion plan to boost the citys capacity to withstand future extreme weather events by, among other things, devising mechanisms to withstand flooding. (Photo by Joe Raedle/Getty Images)
ILULISSAT, GREENLAND - JULY 24: Jason Briner, with the University of Buffalo, Department of Geology, flies in a helicopter to a spot to gather samples of granite to research the age of the local glacial retreat on July 24, 2013 in Ilulissat, Greenland. As Greenlanders adapt to the changing climate and go on with their lives, researchers from the National Science Foundation and other organizations are studying the phenomena of the melting glaciers and its long-term ramifications for the rest of the world. In recent years, sea level rise in places such as Miami Beach has led to increased street flooding and prompted leaders such as New York City Mayor Michael Bloomberg to propose a $19.5 billion plan to boost the citys capacity to withstand future extreme weather events by, among other things, devising mechanisms to withstand flooding. (Photo by Joe Raedle/Getty Images)
ILULISSAT, GREENLAND - JULY 17: Icebergs float in the water on July 17, 2013 in Ilulissat, Greenland. As Greenlanders adapt to the changing climate and go on with their lives, researchers from the National Science Foundation and other organizations are studying the phenomena of the melting glaciers and its long-term ramifications for the rest of the world. In recent years, sea level rise in places such as Miami Beach has led to increased street flooding and prompted leaders such as New York City Mayor Michael Bloomberg to propose a $19.5 billion plan to boost the citys capacity to withstand future extreme weather events by, among other things, devising mechanisms to withstand flooding. (Photo by Joe Raedle/Getty Images)
ILULISSAT, GREENLAND - JULY 22: A fish hangs from a fishermans hook on July 22, 2013 in Ilulissat, Greenland. As Greenlanders adapt to the changing climate and go on with their lives, researchers from the National Science Foundation and other organizations are studying the phenomena of the melting glaciers and its long-term ramifications for the rest of the world. In recent years, sea level rise in places such as Miami Beach has led to increased street flooding and prompted leaders such as New York City Mayor Michael Bloomberg to propose a $19.5 billion plan to boost the citys capacity to withstand future extreme weather events by, among other things, devising mechanisms to withstand flooding. (Photo by Joe Raedle/Getty Images)
UNSPECIFIED - AUGUST 01: Aerial view of melt season in the Antarctic Peninsula - Antarctica. (Photo by DeAgostini/Getty Images)
KANGERLUSSUAQ, GREENLAND - JULY 14: Blooming flowers are seen near the glacial ice toe on July 14, 2013 in Kangerlussuaq, Greenland. As the sea levels around the globe rise, researchers affiliated with the National Science Foundation and other organizations are studying the phenomena of the melting glaciers and its long-term ramifications. In recent years, sea level rise in places such as Miami Beach has led to increased street flooding and prompted leaders such as New York City Mayor Michael Bloomberg to propose a $19.5 billion plan to boost the citys capacity to withstand future extreme weather events by, among other things, devising mechanisms to withstand flooding. (Photo by Joe Raedle/Getty Images)
ILULISSAT, GREENLAND - JULY 15: A glacial toe is seen on July 15, 2013 near Ilulissat, Greenland. As the sea levels around the globe rise, researchers affiliated with the National Science Foundation and other organizations are studying the phenomena of the melting glaciers and its long-term ramifications. In recent years, sea level rise in places such as Miami Beach has led to increased street flooding and prompted leaders such as New York City Mayor Michael Bloomberg to propose a $19.5 billion plan to boost the citys capacity to withstand future extreme weather events by, among other things, devising mechanisms to withstand flooding. (Photo by Joe Raedle/Getty Images)
QAANAAQ, GREENLAND - AUGUST 01: (CHINA OUT, SOUTH KOREA OUT) A researcher of Japan's National Institute of Polar Research investigates the glacier coloured to red by being covered by glacier organisms on August 1, 2012 near Qaanaaq, Greenland. In Greenland there is said to be approximately ten percent of ice of the earth and the large scale melting of the glacier and ice may affect to the global climate change. (Photo by The Asahi Shimbun via Getty Images)
A child wades through the flood waters in front of the Doges' Palace, next to a flooded St. Mark's Square, in Venice on November 7, 2014. The high water, a combination of high tides and a strong Scirocco wind in the Adriatic Sea, stood at 110 centimeters early on November 7. The city has for years been wrestling with the problems posed by the threat of rising sea levels. AFP PHOTO / OLIVIER MORIN (Photo credit should read OLIVIER MORIN/AFP/Getty Images)
HOOPERS ISLAND, MD - OCTOBER 30: Donny Willey stands near graves that were once several yards from the waters edge are now exposed and releasing human remains by the eroding waters of the Chesapeake Bay at the Anchor of Hope Cemetery October 30, 2014 in Hoopers Island, Maryland. Willey volunteered his time to try and save the cemetery from erosion and cannot get a permit from the state of Maryland to erect a seawall. The cemetery is the resting place of more than 150 men, women, and children; from the War of 1812 to veterans of several other wars, from the founding family of Hoopers Island to slaves and freed slaves. With sea levels projected to rise several feet over the next century, several islands in the Chesapeake Bay region are slowly eroding away. (Photo by Mark Wilson/Getty Images)
ROBBINS, MD - OCTOBER 09: A truck drives on Robbins Road that is flooded from the high tide of the Blackwater River October 9, 2014 in Robbins, Maryland. Several islands and property's located at sea level in the lower Chesapeake Bay region are slowly eroding away as sea levels rise. Officials have projected the sea level will rise several feet over the next century leaving many of the Chesapeake bay's lower islands underwater. (Photo by Mark Wilson/Getty Images)
HOOPERS ISLAND, MD - OCTOBER 08: A Snapping Turtle sits in the middle of the road October 8, 2014 in Hoopers Island, Maryland. Several islands in the Chesapeake Bay region are slowly eroding away as sea levels are projected to rise several feet over the next century. (Photo by Mark Wilson/Getty Images)
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So how to reconcile the two conclusions? Both Schaefer and Beirman say that it isn't that hard to do. The seemingly-disparate results probably just indicate how much more study is needed to uncover the whole truth. "It's like the parable of the blind person and the elephant, we each know our little pieces of this but we don't have the whole picture figured out," Bierman says.

While Schaefer's core was taken in the center of Greenland (at the thickest part of the ice sheet), Bierman's looked at sediments that came from eastern Greenland, an area of highlands. In Schaefer's paper, he notes several possible scenarios in which the ice sheet might have collapsed by 90 to 95 percent, but also indicates that the higher altitude of eastern Greenland might have been the location where 5 to 10 percent of the ice sheet persisted.

"The most important thing is we now have two important interesting sets of data that we didn't have a week ago," Bierman says. "It's going to take some time to figure out not only the best fit between our two studies, but all the other studies. We need to come up with an explanation that doesn't just fit one or two studies, but everything we know about Greenland."

Icebergs Greenland

Paul Bierman

Icebergs Greenland

Icebergs float in a Greenland Fjord in June.

What Comes Next?

"One of the hopes is that with this study we show that bedrock underneath ice sheets is an untapped climate archive," Schaefer says.

There are tools currently in development that could drill through the ice quickly, melting it in the process for the express purpose of sampling the bedrock below. Schaefer hopes that future studies will focus on collecting these bedrock samples, which researchers can use to get a clearer picture of our climate history from other areas in Greenland and Antarctica. Bierman is planning on studying sediments from off the coast of other areas of Greenland, also hoping to get a more detailed picture of that island's climate history.

"Both of these studies are science that will be important pieces to understand how the ice sheet will behave. They themselves do not predict what's going to happen, but they're part of a bigger picture of understanding how a complex system behaves over time," Bierman says.

Understanding how the Greenland ice sheet functioned in the past could help us better understand how it could behave in the future, particularly as the climate warms. With the human limitation of a short life span and the utter lack of a time machine, conceptual and numerical models of how the ice sheet behaves are the only way that climate scientists can understand how these massive hunks of ice change over thousands and millions of years. Or, in our current situation, how they might change over the next few centuries.

"We're facing a climate that you can deny all you want, but the data shows it is getting warmer. There is zero debate in the scientific community that if it's going to get warmer, Greenland is going to melt. And sitting in Greenland are the equivalent of seven meters (23 feet) of sea level rise," Bierman says. "I don't think this is a trivial problem by any means. We need to understand how the Greenland ice sheet functions over time because it is the best way we're going to figure out what's going to happen in the future as we tweak our climate."

Schaefer agrees. "What we are doing in the moment [with climate change] is so much faster and so much stronger than the natural forces that I just don't think it is reasonable to expect us to keep the Greenland ice sheet," Schaefer says. "This not to steer panic or something, it just is what it is. We have to prepare for these higher sea level scenarios."

"It's just idiotic not to plan for this," Schaffer adds. "It will already be extremely expensive to mitigate and adapt to that [rising sea levels]. It would be a complete and unmitigated disaster if it hit us unprepared, and it would throw the United States behind countries that do plan ahead."

But if the United States is going to keep from falling behind, it needs to start preparing now. And that means gathering all the data it can about the past to get a clearer picture of what's waiting for us down the road.

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