The extent of ice loss at the top of the world, as seen by satellites, is literally the tip of the iceberg. Although the Arctic ice cap's shrinkage is often expressed in terms of area, the change in volume is just as striking. Between 1980 and 2016 the amount of summer ice in cubic kilometers has decreased by an estimated 72 percent. The numbers for 2016 only buttressed the trend: ice hit record lows for the months of October and November. The Arctic may be free of ice by midcentury if we continue emitting greenhouse gases at the current rate, says Julienne Stroeve, a researcher at the U.S. National Snow and Ice Data Center.

Credit: Amanda Montañez; Source: Piomas Monthly Ice Volume Data, 1979–Present, Polar Science Center, University of Washington http://psc.apl.uw.edu/research/projects/arctic-sea-ice-volume-anomaly/data