National Science Foundation-funded researchers at the University of Utah have discovered a previously unknown aquifer in the Greenland ice sheet that holds liquid water all year long in the otherwise perpetually frozen winter landscape. The aquifer is extensive, covering 27,000 square miles.
The reservoir is known as the "perennial firn aquifer" because water persists within the firn--layers of snow and ice that don't melt for at least one season. Researchers believe it figures significantly in understanding the contribution of snowmelt and ice melt to rising sea levels.
The journal Nature Geoscience published the study online Sunday, Dec. 22.
"Of the current sea level rise, the Greenland Ice Sheet is the largest contributor--and it is melting at record levels,” said Rick Forster, the study's lead author and a professor of geography at the University of Utah. "So understanding the aquifer's capacity to store water from year to year is important because it fills a major gap in the overall equation of meltwater runoff and sea levels."
This research is the result of an international collaboration among researchers at the University of Utah; the Geological Survey of Denmark and Greenland; Byrd Polar Research Center at Ohio State University; the Institute for Marine and Atmospheric research Utrecht, Utrecht University in the Netherlands; the NASA Goddard Space Flight Center; the Center for Remote Sensing of Ice Sheets at the University of Kansas and the Desert Research Institute at the University of Nevada, Reno.
Forster and the Utah team were supported by both the Division of Polar Programs at the National Science Foundation and NASA.
Forster's team has been doing research in southeast Greenland since 2010 to measure snowfall accumulation and how it varies from year to year. The area they study covers 14 percent of southeast Greenland yet receives 32 percent of the entire ice sheet's snowfall, but there has been little data gathered.
In 2010, the team drilled core samples in three locations on the ice for analysis. Team members returned in 2011 to approximately the same area, but at lower elevation. Of the four core samples taken then, two came to the surface with liquid water pouring off the drill while the air temperatures were minus 4 degrees Fahrenheit. The water was found at about 33 feet below the surface at the first hole and at 82 feet in the second hole.
"This discovery was a surprise," Forster says. "Although water discharge from streams in winter had been previously reported, and snow temperature data implied small amounts of water, no one had yet reported observing water in the firn that had persisted through the winter."
The aquifer's 27,000 square miles is larger than the state of West Virginia. It is similar in form to a groundwater aquifer on land that can be used for drinking water.
"Here instead of the water being stored in the airspace between subsurface rock particles, the water is stored in the air space between the ice particles, like the juice in a snow cone," Forster said. "The surprising fact is the juice in this snow cone never freezes, even during the dark Greenland winter. Large amounts of snow fall on the surface late in the summer and quickly insulates the water from the subfreezing air temperatures above, allowing the water to persist all year long."
The Greenland ice sheet covers roughly the same area as the states of California, Nevada, Arizona, New Mexico, Colorado and Utah combined. The average thickness of the ice is 5,000 feet.
In 2012, the ice sheet lost volume of 60 cubic miles--a record for melt and runoff.
In the unlikely event that all the water retained in the ice sheet melted, it is estimated that the global sea level would rise about 21 feet, says Forster. Monitoring run-off amounts and how the water is moving is critical to accurately predicting sea-level changes.