Image caption Researchers were surprised to see liquid water coming up through the drill hole as temperatures were below freezing 
 
 Researchers say they have discovered a large reservoir of melt water that sits under the Greenland ice sheet all year round. 
 
 The scientists say the water is stored in the air space between particles of ice, similar to the way that fruit juice stays liquid in a slush drink. 
 
 The aquifer, which covers an area the size of Ireland, could yield important clues to sea level rise. 
 
 The research is published in the journal, Nature Geoscience. 
 
 The melting of the Greenland ice sheet has been a significant contributor to a rise in sea levels over the past 100 years. 
 
 The water is stored in the air space between the ice particles, like the juice in a snow cone Prof Rick Forster, University of Utah 
 
 According to the latest report from the Intergovernmental Panel on Climate Change, the ice sheet lost 34 billion tonnes of ice per year between 1992 and 2001 - but this increased to 215 billion tonnes between 2002 and 2011 
 
 Scientists still have many unanswered questions about the direction and speed and ultimate destination of this melted water. 
 
 Ice free liquid 
 
 This new research finds that a significant amount is stored in partially compacted snow called firn. 
 
 In the spring of 2011, researchers drilled deep into this slushy layer and to their surprise, found liquid water flowing back to the surface even though air temperatures were -15 degrees C. 
 
 As this was well before the onset of the summer melt, the team concluded the water had persisted in a liquid state through the Greenland winter. 
 
 "This discovery was a surprise," said Prof Rick Forster from the University of Utah. 
 
 "Instead of the water being stored in the air space between subsurface rock particles, the water is stored in the air space between the ice particles, like the juice in a snow cone." 
 
 The scientists have also come up with a rough estimate for the amount of water that is contained in the aquifer which itself covers an area of 70,000 sq km. 
 
 Image caption The researchers drilled in areas with large accumulations of snow on the surface 
 
 They believe that it holds roughly 140 billion tonnes of water, which is the equivalent to 0.4mm of sea level rise per year - about half of what Greenland contributes to the sea every year. 
 
 But crucially the scientists don't know the ultimate destination of the water in the reservoir. 
 
 "It depends on whether it is currently connected to a system that is draining into the ocean or if it is a bit isolated and completely acting as a storage source without a current connection," said Prof Forster. 
 
 "We don't know the answer to this right now. It's massive, it's a new system we haven't seen before - we need to understand it more completely if we are to predict sea level rise." 
 
 The scientists say the water is prevented from freezing by the large amounts of snow that fall on the surface of the ice sheet late in the summer. 
 
 This insulates the water from the air temperatures which are below freezing, allowing the water to persist as liquid all year long. 
 
 Other researchers believe this discovery may help explain disparities between projections of mass loss by climate models and observations from satellites. 
 
 "The large mass of liquid water in firn also represents a heat sink that could be playing a role in Greenland's interaction with the climate system," wrote Dr Joel Harper from the University of Montana, in a comment piece published alongside the study. 
 
 "As the intensity of surface melt in Greenland increases and expands upwards to the higher elevations that are covered by firn, liquid water storage may play an expanding role in the ice sheet's future response to climate change." 
 
 Follow Matt on Twitter @mattmcgrathbbc. ||||| A drill rig was used to extract old snow (firn) cores from within the Greenland snow aquifer. 
 
 Big surprises still hide beneath the frozen surface of snowy Greenland. Despite decades of poking and prodding by scientists, only now has the massive ice island revealed a hidden aquifer. 
 
 In southeast Greenland, more than 100 billion tons of liquid water soaks a slushy snow layer buried anywhere from 15 to 160 feet (5 to 50 meters) below the surface. This snow aquifer covers more than 27,000 square miles (70,000 square kilometers) — an area bigger than West Virginia — researchers report today (Dec. 22) in the journal Nature Geoscience. 
 
 "We thought we had an understanding of how things work in Greenland, but here is this entire storage system of water we didn't realize was there," said Richard Forster, lead study author and a glaciologist at the University of Utah. 
 
 The discovery will help scientists better understand the fate of Greenland's annual surface melt, which contributes to sea level rise. When the summer sun warms the Arctic island, a giant water world of stunning blue lakes and streams appears atop the ice. Tracking this surface runoff helps scientists account for ice lost to melting each year. Until now, researchers thought most of this water went to the ocean or refroze on the ice. Now they've found a new hiding place. 
 
 "This throws an additional complexity into the system," Forster told LiveScience. 
 
 There is enough water in the snow aquifer to raise global sea level by 0.015 inches (0.4 millimeters), according to a separate study by the same team published Nov. 30 in the journal Geophysical Research Letters (GRL). Every year, Greenland adds 0.03 inches (0.7 mm) of water to global sea level rise from melting snow and ice, Forster said. [Top 10 Surprising Results of Global Warming] 
 
 Where water flows 
 
 No one yet knows how old the water in the aquifer is, and whether it stays trapped in the snow or reaches the ocean in slow streams or catastrophic floods. However, the top of the water table rose after Greenland's huge surface melt in 2012, the researchers report in their GRL study. 
 
 Water from the Greenland snow aquifer draining from a drill core extracted 40 feet (12 meters) below the surface of the ice sheet in April, before the summer surface melt, with air temperatures of 5 degrees Fahrenheit (minus 15 degrees Celsius). Credit: Ludovic Brucker 
 
 The group will return to southeast Greenland in the coming years to answer these and other questions, Forster said. "Just seeing how old it is would answer a lot of questions," he said. 
 
 The final destination of Greenland's melt water is also key to understanding how the ice sheet ebbs and flows, because water under the ice sheet lubricates flowing glaciers. Researchers know some melt water goes to the bottom of the ice, trickling through cracks and racing through vertical pipes called moulins. Some of the water also simply refreezes on the surface when winter comes. Liquid water sitting in buried snow layers can also slowly warm and melt the ice sheet. 
 
 "The existence of this rather flavorless natural snow cone has many implications for the future of the ice sheet, some that may make the ice go away faster and others that help keep the ice a little longer," said Richard Alley, a glaciologist at Pennsylvania State University, who was not involved in the study. "We would like to understand these implications better so we can help reduce the uncertainties about future changes." 
 
 Soppy surprise 
 
 Forster and his colleagues discovered the aquifer in 2011, when a drill punched into sopping wet snow, as mushy as a summer snow cone treat or a Slurpee. (This was a year before the big surface melt of 2012.) "Water was pouring out of the core," Forster said — not what one wants to find when all the electronics are mounted outside the drill. A video of the event reveals both excitement and a few choice words among the scientists. [Watch: Discover Greenland's Hidden Aquifer] 
 
 The water was stored in hard, compacted snow called firn — the remains of the previous year's snowfall. Forster thinks the aquifer went undiscovered because so much snow falls in this corner of Greenland. 
 
 In Southeast Greenland, frequent storms crash into tall mountains, dumping more winter snow there than anywhere else on the icy island. The thick, insulating snow blanket keeps the watery firn liquid during the freezing winter, like a down coverlet, Forster said. 
 
 Many drillers have skipped over this part of Greenland because the snow layers are so thick, Forster said, and most people who are drilling cylinders of ice from the ice sheet are looking to see the layers compacted over hundreds and thousands of years. "People who extract ice cores don't want to go through high accumulation layers," he said. But Forster's team was interested in the past 10 years of snowfall, so the southeast was a good research spot, he said. 
 
 Ground-penetrating radar, towed by snowmobile, helped the researchers locate more water nearby, which the group confirmed by drilling in 2011 and 2013. When the researchers returned home, they searched airborne radar data from NASA's Operation IceBridge and discovered the true extent of the buried snow aquifer, all in areas with heavy snowfall. Most of the water is in the southeast, but a few pockets appeared in the south and southwest, Forster said. "It all corresponds to these areas of high snow accumulation," he said. 
 
 Greenland's future 
 
 Researchers estimate Greenland has lost more than 200 million tons of ice and snow each year since 2003. The ice sheet will completely disappear when the planet's average temperature rises by 2 to 7.2 degrees Fahrenheit (1 to 4 degrees Celsius) above preindustrial temperatures, as predicted by the latest report from the Intergovernmental Panel on Climate Change, released in September. 
 
 Earth's surface temperatures are already up 1.3 F (0.7 C) from preindustrial temperatures, with average temperatures rising faster in Greenland. 
 
 "This doesn't change our knowledge that too much carbon dioxide in the air will melt Greenland's ice, but it will help us make better estimates of how much and how fast," Alley said. 
 
 Email Becky Oskin or follow her @beckyoskin. Follow us @livescience, Facebook& Google+. Original article on LiveScience.
– As far as discoveries go, this one is literally huge: An aquifer holding more than 100 billion tons of water that covers an area larger than West Virginia has been discovered beneath Greenland's snow-covered ice sheet. And it caught the researchers who stumbled on it in 2011 off-guard, with lead study author Richard Forster telling LiveScience, "We thought we had an understanding of how things work in Greenland, but here is this entire storage system of water we didn't realize was there." As for the "where," the aquifer was identified in the southeast part of the country, ranging from 15 to 160 feet beneath the surface, whose snow acts as an insulator, keeping the water liquid year-round. Forster gives this great description of how the water is stored, per the BBC: "in the air space between the ice particles, like the juice in a snow cone." But the find has raised plenty of questions, like: How old is the water? Does it stay where it is, or trickle to the sea ... or rush toward the sea in a flood? In a separate study, the team determined that if released, the aquifer's water could push global sea levels up 0.015 inches. And in terms of sea level rise, LiveScience explains that scientists have long assumed that most of the water produced in the country's annual surface melt streams toward the ocean, or eventually refroze; the aquifer is essentially a "new hiding place," one that researchers can study to get a better grasp on the annual melt. Says Forster, "We need to understand it more completely if we are to predict sea level rise."