Vertical Land Motion by satellite Altimetry and tide gauge Difference

• Applicants: Dr. Marcello Passaro; Dr.-Ing. Laura Sanchez-Drewes
• Subject Area: Geodesy, Photogrammetry, Remote Sensing, Geoinformatics, Cartography
• Term: from 2018 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 411072120

• Final Report Year: 2023

Final Report Abstract

Climate-driven sea level changes due to thermal expansion and land-locked ice melt represent a major threat to coastal population, infrastructures, and habitability. Global mean sea level (GMSL) change is expected to directly affect hundreds of millions of people throughout the upcoming century. Hence, because it is one of the most costly consequences of climate change, understanding the drivers and impacts of sea level change on coastal populations, economies, and ecosystems, has become a central objective of ongoing research. One of the great challenges in estimating future coastal sea level change is that, in addition to climate-driven effects, a large proportion of sea level changes relative to the coast arise from coastal subsidence and uplift due to vertical land motion. However, previous research has applied simplified assumptions of vertical land motion, so far neglecting its non-linear character in regional and global scale analyses, and using limited observational constraints. To overcome these limitations, we developed a new Bayesian approach to reconstruct vertical land motion continuously in space in time, based on a multitude of measurement techniques (i.e., the Global Navigation Satellite System, tide gauges and satellite altimetry) within the DFG project ‘Vertical Land Motion by satellite Altimetry and tide gauge Difference (VLAD)’. Using this reconstruction, we answered the questions of how vertical land motion has contributed to past and present relative sea level change, and to what extent it can be projected into the upcoming century. In light of this novel vertical land motion reconstruction, we disentangled its role in relative sea level changes over 1900-2150. Vertical land motion explains a significant proportion (34%) of the variance of present-day relative sea level change. While projected sea level change in 2150 will be dominated by absolute sea level changes, vertical land motion will account for half of the variance of the deviations in regional relative sea level changes. In contrast to previous research, and against expectations of the initial research plans, we demonstrated that regional vertical land motion should not be considered a linear process, due to a variety of non-linear dynamics, such as tectonic activity, surface mass deformation, or human impacts. When accounting for these processes, non-linear vertical land motion significantly increases uncertainties in coastal sea level projections compared to current estimates such as those in the recent 6th Assessment Report of the IPCC. Accordingly, vertical land motion explains 30% of the combined relative sea level change uncertainties in global coastal sea level projections. Thus, previously neglected time-variable effects significantly impact confidence intervals in projections of relative sea level change. These results reinforce the need to incorporate observation-based vertical land motion in sea level studies to better understand and model these time-varying processes. Given the partially non-linear behavior of vertical land motion, we motivate the reconsideration of its role as a dynamic component of coastal sea level change. We recommend further research to better understand how vertical land motion has changed over the past century and to develop additional process-based scenarios for future changes in vertical land motion.

Publications

• DiscoTime Software
  Oelsmann, J., Passaro, M., Sánchez, L., Dettmering, D., Schwatke, C., and Seitz, F.
  
• Absolute Baltic Sea Level Trends in the Satellite Altimetry Era: A Revisit. Frontiers in Marine Science, 8 (2021, 5, 28).
  Passaro, Marcello; Müller, Felix L.; Oelsmann, Julius; Rautiainen, Laura; Dettmering, Denise; Hart-Davis, Michael G.; Abulaitijiang, Adili; Andersen, Ole B.; Høyer, Jacob L.; Madsen, Kristine S.; Ringgaard, Ida Margrethe; Särkkä, Jani; Scarrott, Rory; Schwatke, Christian; Seitz, Florian; Tuomi, Laura; Restano, Marco & Benveniste, Jérôme
  
• North SEAL: a new dataset of sea level changes in the North Sea from satellite altimetry. Earth System Science Data, 13(8), 3733-3753.
  Dettmering, Denise; Müller, Felix L.; Oelsmann, Julius; Passaro, Marcello; Schwatke, Christian; Restano, Marco; Benveniste, Jérôme & Seitz, Florian
  
• North SEAL: Gridded Sea Level Anomalies and Trends for the North Sea from Multi-Mission Satellite Altimetry (data). Deutsches Geodätisches Forschungsinstitut, München. SEANOE
  Müller F. L.; Oelsmann J.; Dettmering D.; Passaro M.; Schwatke C.; Restano M.; Benveniste J. & Seitz F.
  
• The zone of influence: matching sea level variability from coastal altimetry and tide gauges for vertical land motion estimation. Ocean Science, 17(1), 35-57.
  Oelsmann, Julius; Passaro, Marcello; Dettmering, Denise; Schwatke, Christian; Sánchez, Laura & Seitz, Florian
  
• Bayesian modelling of piecewise trends and discontinuities to improve the estimation of coastal vertical land motion. Journal of Geodesy, 96(9).
  Oelsmann, Julius; Passaro, Marcello; Sánchez, Laura; Dettmering, Denise; Schwatke, Christian & Seitz, Florian
  
• ESA sea level cci+ technical report
  Oelsmann, J. and Passaro, M.
  
• Piecewise trends and discontinuities in GNSS and SATTG time series. SEANOE.
  Oelsmann Julius; Passaro Marcello; Sanchez Laura; Dettmering Denise; Schwatke Christian & Seitz Florian
  
• Sea level along the world’s coastlines can be measured by a network of virtual altimetry stations. Communications Earth & Environment, 3(1).
  Cazenave, Anny; Gouzenes, Yvan; Birol, Florence; Leger, Fabien; Passaro, Marcello; Calafat, Francisco M.; Shaw, Andrew; Nino, Fernando; Legeais, Jean François; Oelsmann, Julius; Restano, Marco & Benveniste, Jérôme