Detecting a forced signal in satellite-era sea-level change

• Published in: Environmental Research Letters
• Main Authors: Richter, Kristin, Meyssignac, Benoit, Slangen, Aimée B A, Melet, Angélique, Church, John A, Fettweis, Xavier, Marzeion, Ben, Agosta, Cécile, Ligtenberg, Stefan R M, Spada, Giorgio, Palmer, Matthew D, Roberts, Christopher D, Champollion, Nicolas
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2020
• Subjects: forced trends; internal variability; detection; sea-level rise; Ice Sheet
• Online Access: http://hdl.handle.net/11585/798997; https://doi.org/10.1088/1748-9326/ab986e; https://iopscience.iop.org/article/10.1088/1748-9326/ab986e/meta

In this study, we compare the spatial patterns of simulated geocentric sea-level change to observations from satellite altimetry over the period 1993–2015 to assess whether a forced signal is detectable. This is challenging, as on these time scales internal variability plays an important role and may dominate the observed spatial patterns of regional sea-level change. Model simulations of regional sea-level change associated with sterodynamic sea level, atmospheric loading, glacier mass change, and ice-sheet surface mass balance changes are combined with observations of groundwater depletion, reservoir storage, and dynamic ice-sheet mass changes. The resulting total geocentric regional sea-level change is then compared to independent measurements from satellite altimeter observations. The detectability of the climate-forced signal is assessed by comparing the model ensemble mean of the ‘historical’ simulations with the characteristics of sea-level variability in pre-industrial control simulations. To further minimize the impact of internal variability, zonal averages were produced. We find that, in all ocean basins, zonally averaged simulated sea-level changes are consistent with observations within sampling uncertainties associated with simulated internal variability of the sterodynamic component. Furthermore, the simulated zonally averaged sea-level change cannot be explained by internal variability alone—thus we conclude that the observations include a forced contribution that is detectable at basin scales.