Scientists believe the other half may have come from melting glaciers, melting ice sheets or groundwater. But they don't know how much each of these sources contributed. Although Antarctica holds 90 percent of the water stored in ice sheets, the ice on Greenland can have a more immediate effect on sea levels because water cycles faster through it. Snow at higher elevations forms ice that slowly inches toward the coast. After centuries of travel, the ice reaches the coast and the ice sheet loses mass at its margins through iceberg calving and melting.
Some studies indicate that the ice sheet margins are shrinking.
We need to understand these trends before we can say if the whole ice sheet is changing. To develop that understanding, Bales and his students have spent the past five years drilling ice cores at higher elevations in Greenland and analyzing them at their labs in Tucson. By doing this they are developing a centuries-long historical record of snow accumulation. Some of the results from this study were published in August in Nature magazine. The article was written by Bales, and seven other researchers from the University of Nevada, University of Washington, Ohio State University, University of Missouri-Columbia, University of Nebraska, and the NASA Wallops Flight Facility.