Identifying contributions to 20th century coastal sea level rise

Sönke Dangendorf, University of Siegen, Research Institute for Water and Environment, Siegen, Germany; Tulane University, Department of River-Coastal Science & Engineering, New Orleans, United States, Leon Chafik, Stockholm University, Department of Meteorology, Stockholm, Sweden, Christopher G Piecuch, Woods Hole Oceanographic Institution, Woods Hole, MA, United States and Thomas Frederikse, Jet Propulsion Laboratory, Caltech, Pasadena, CA, United States
Abstract:
Over many decades the separation of coastal sea level rise observed at individual tide gauge locations into its sterodynamic (ocean density & ocean circulation changes) and barystatic mass changes due to continental freshwater sources (e.g. glaciers or groundwater) has been an unsolved enigma for the scientific community. At the beginning of the 2000s almost no estimates about the barystatic contributions were available and little knowledge existed about the spatial origin of steric sea level signals and how they propagate from the deep toward the shallow coastal ocean where tide gauges are usually situated.

The last 15 years have seen a rapid progress in almost all disciplines surrounding sea level change including more robust datasets of individual contributions to sea level change as well as deeper understanding of ocean dynamics that control coastal sea level. With these new estimates, we revisit the 20th-century local sea level budget for seven worldwide distributed coastal regions by correcting individual tide gauge records for rates of vertical land motion and contemporary barystatic mass contributions from glaciers, ice-sheets, groundwater depletion and water stored behind dams (summing globally to ~0.9 mm/yr). We further introduce a simple diagnostic tool based on correlations and standard deviations between the residual sea level at tide gauges and steric estimates from hydrography to estimate the sterodynamic signal at individual locations.

Our results based on this diagnostic tool identifies source regions for the sterodynamic signal that are consistent with our present-day understanding of ocean circulation systems and agrees with the residual obtained from tide gauges. Averaged over all stations, this suggests a global steric contribution of about 0.5 mm/yr over the 20th century. Our results provide important new insights for the understanding of past sea level change and hint at modelling needs for downscaling future coastal sea level change.

Back to: Coastal Processes and Climate Change: Scientific Methods and Tools to Characterize the Impacts of Changing Coastal and Nearshore Processes I