The melting of the Greenland and Antarctic ice sheets is speeding up the pace of sea level rise a little bit every year, according to a new analysis of satellite data published in the Proceedings of the National Academy of Sciences. If the current pace continues, the study estimates, seas could rise more than 2 feet by 2100.
But the authors note that sea levels could increase at a much more rapid rate if, as expected, the melting of polar ice sheets intensifies this century.
Global sea levels have risen 2.8 inches since the early 1990s. Over the long term, much of this rise has been driven by the expansion of water as it warms and from meltwater running off ice sheets and glaciers into the oceans. Scientists had previously estimated that global sea levels were increasing at a steady 3 millimeters (0.1 inches) per year. But the new analysis found that the annual rate has accelerated over the last 25 years — increasing at about 0.8 mm per year above the 3 millimeter baseline. This rise is due mainly to the increasing melting of the Greenland and Antarctic ice sheets. The latest paper relied not only on coastal tide gauge data, but also on a longer series of satellite records that now allow scientists to study changes in the open ocean as well.
The new data means the annual rate of sea level rise could be at least 10 mm per year by 2100, resulting in seas being 65 centimeters (26 inches) higher than they are today by the end of the century — double the amount if the rate had stayed constant at 3 mm.
Steve Nerem, an atmospheric scientist at the University of Colorado, Boulder and lead author of the new study, called the findings “almost certainly a conservative estimate.” Other recent studies have projected sea level increases of 3 to 6 feet by 2100.
“Our extrapolation assumes that sea level continues to change in the future as it has over the last 25 years,” he said in a statement. “Given the large changes we are seeing in the ice sheets today, that’s not likely.”