Research based on 25 years of satellite data has found that the rate of sea level rise is accelerating each year, and could be as much as 10 mm per year by 2100, resulting in a 65 cm sea level rise by then.
The analysis, led by CIRES Fellow Steve Nerem, professor of Aerospace Engineering Sciences at the University of Colorado Boulder, was published in Proceedings of the National Academy of Sciences.
Over the past 25 years, the sea levels have risen 7 cm, Professor Nerem warns that the rate of sea level rise is increasing mainly due to accelerated melting in Greenland and Antarctica, and has the potential to double the total sea level rise by 2100 as compared to projections that assume a constant rate—to more than 60 cm instead of about 30.
"And this is almost certainly a conservative estimate," he added. "Our extrapolation assumes that sea level continues to change in the future as it has over the last 25 years. Given the large changes we are seeing in the ice sheets today, that's not likely."
Sea levels have been measured using satellite altimeter measurements since 1992, including the U.S./European TOPEX/Poseidon, Jason-1, Jason-2, and Jason-3 satellite missions. However, detecting acceleration is difficult due to variability caused by influences such as volcanoes and climate patterns such as El Niños and La Niñas .
Nerem and his team used climate models to account for these influences, and used data from the GRACE satellite gravity mission to determine that the acceleration is largely being driven by melting ice in Greenland and Antarctica. Tide tide gauge data was used to assess potential errors in the altimeter estimate.
The research team consider their findings to be just the first step. The 25-year record is just long enough to provide an initial detection of acceleration—the results will become more robust as the Jason-3 and subsequent altimetry satellites lengthen the time series. Future research will focus on refining the results in this study with longer time series, and extending the results to regional sea level, to better predict local impacts.