by Mary Caperton Morton Friday, August 21, 2015
Studies tracking sea-level rise over the past few decades have been all over the map, with reports variously indicating that the rate of rise has accelerated, stayed constant or declined. Now, a new GPS-based study published in Nature Climate Change indicates that sea-level rise has indeed been accelerating over the last decade.
Past studies have usually relied on satellite data to track coastlines changing due to sea levels. But most have not taken into account vertical land movement, which can be caused by tectonic changes, compaction of sedimentary deposits, isostatic rebound in formerly glaciated regions, or processes like pumping of subsurface gases or groundwater, Christopher Watson of the University of Tasmania in Australia and his colleagues reported.
By combining GPS data tracking vertical land movement over time with hourly data from a global network of tide gauges, the team corrected inaccuracies accrued in satellite measurements of sea levels and produced a more refined sea-level record over the last 20 years.
The team found that the overall rate of global mean sea-level rise between 1993 and 2014 was lower than previously measured, down from 3.2 millimeters per year to 2.6 to 2.9 millimeters per year. The first six years of the record (from 1993 to 1999) were most affected by the team’s corrections, resulting in a scaling down of estimates by 0.9 to 1.5 millimeters per year in that period. This recalculation means that, since about 2000, the rate of rise has actually accelerated compared to the latter decades of the 20th century.
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