The quality of lake ice is of paramount importance for ice safety and lake ecology under ice, but its temporal and spatial variability is largely unknown. An international research team with IGB researcher Hans-Peter Grossart conducted a coordinated sampling campaign of lake ice quality throughout the Northern Hemisphere. The team, led by Sweden's Uppsala University, was able to show that lake ice during this period generally consisted of unstable white ice, which at times accounted for up to 100 percent of the total ice thickness.