Mongabay: Global sea level rise this century from a melting Greenland ice sheet may be two to three times greater than current estimates warn researchers writing in journal Nature Geoscience. Analyzing geologic data and computer models to reconstruct the melting of the Laurentide Ice Sheet, a land-based ice mass that covered much of North America, 9,000 to 6,500 years ago, Anders Carlson and colleagues found that ice sheet melt can occur quite rapidly. “We have never seen an ice sheet …