An international team of researchers has uncovered a giant reservoir of water beneath the ice sheet in Southeast Greenland.
This map shows locations of the perennial aquifer on the Greenland ice sheet detected by radar and cores in 2011. NASA’s airborne radar flight lines are grey and locations of detected aquifer are magenta dots. Image credit: Forster RR et al.
Scientists found the reservoir while drilling in southeast Greenland in 2011 to study snow accumulation.
They then used data from NASA’s Operation IceBridge airborne campaign to confine the limits of the water reservoir, which spreads about 70,000 square km.
The findings appear in two papers published online in the journal Nature Geoscience and the journal Geophysical Research Letters.
The scientists believe that the thick snow cover insulates the aquifer from cold winter surface temperatures, allowing it to remain liquid throughout the year. The aquifer is fed by melt water that percolates from the surface during the summer.
In April 2013, co-author Dr Lora Koenig from NASA’s Goddard Space Flight Center in Greenbelt with colleagues studied the physical characteristics of the water reservoir.
They extracted two cores of aged snow that were saturated with water. They used a water-resistant thermoelectric drill to study the density of the ice and lowered strings packed with temperature sensors down the holes, and found that the temperature of the aquifer hovers around 32 degrees Fahrenheit (0 degrees Celsius).
The researchers then measured the top of the aquifer at around 12 m under the surface. This was the depth at which the boreholes filled with water after extracting the ice cores. They determined the amount of water in the water-saturated ice cores by comparing them to dry cores extracted nearby. They determined the depth at which the pores in the ice close, trapping the water inside the bubbles – at this point, there is a change in the density of the ice that the scientists can measure. This depth is about 37 m and corresponds to the bottom of the aquifer.
Once the scientists had the density, depth and spatial extent of the waster reservoir, they were able to come up with an estimated water volume of about 140 metric gigatons.
If this water was to suddenly discharge to the ocean, this would correspond to 0.4 mm of sea level rise.
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Forster RR et al. 2013. Extensive liquid meltwater storage in firn within the Greenland ice sheet. Nature Geoscience, published online December 22, 2013; doi: 10.1038/ngeo2043
Koenig LS et al. 2013. Initial in situ measurements of perennial meltwater storage in the Greenland firn aquifer. Geophysical Research Letters, published online; doi: 10.1002/2013GL058083
