Scientists have determined how a warming global climate might translate into rising sea levels, but exactly how the change plays out locally is not as well understood, especially when the ground itself is moving. Coastal subsidence or uplift exacerbates the impact of sea level rise, and measuring this vertical land motion is fundamental to estimating the needs of coastal communities and ecosystems.
Here Wöppelmann and Marcos evaluate the statistical accuracy of combining three integrated data sources in order to evaluate the role of vertical land motion in long-term sea level rise.
To track vertical movement of the Earth’s surface, the researchers analyzed data from GPS stations, satellite radar altimetry, and time series mean sea level measures from 598 tide gauge stations located between 66°N and 66°S, recorded between 1993 and 2014. By combining GPS and satellite altimetry data, they were able to measure long-term sea level change and account for the spatial variability recorded by tide gauges. They could account for variability even across regions where sea level is influenced by different kinds of vertical movement. For example, they were able to successfully track long-term trends in the Gulf of Mexico, where subsidence processes dominate, as well as in northern Europe, where uplift dominates.
Overall, satellite altimetry was useful in the scope of the data sets that the authors evaluated. However, they recommend further study to determine how well regional products perform over longer study periods compared to global products. Their results don’t account for systematic errors—like instrumentation or geophysical factors—but they do demonstrate the value of combining satellite and GPS data with tide gauge measures in performing statistical analyses of vertical land motion as it relates to sea level change.
The researchers also acknowledge that a plateau has been reached in the technological ability to evaluate contemporary sea level rise within the current realization of the terrestrial reference frame but point to the potential for progress in ongoing research into newer techniques such as the Geodetic Reference Antenna in Space (GRASP). Further, integrated research will contribute to a better scientific understanding of what a warmer future looks like. (Reviews of Geophysics, doi:10.1002/2015RG000502, 2016)
—Lily Strelich, Freelance Writer
Citation: Strelich, L. (2016), New methods measure how vertical land motion affects sea level, Eos, 97, doi:10.1029/2016EO046611. Published on 23 February 2016.