JWG C.4: Sea level and vertical land motion

Chair: Roelof Rietbroek (Germany)
Vice-Chair: Riccardo Riva (Netherlands)
(Affiliation: Commission 1, 2 & 4, GGOS)


Global mean sea-level change is an excellent overall indicator of the state of the climate and the cryosphere, but societal impact is better represented by regional to local sea-level change, which can be very different from the global mean. Regional sea-level change may be more accurately described by dedicated time series, which incorporate knowledge of the designated coastal zone and vertical land motion. The non-uniform response of sea level to terrestrial mass changes causes regions in the far field of melting glaciers and ice sheets to be more sensitive to mass loss. Furthermore, long-term changes in wind fields, ocean heat uptake and circulation can change regional sea level. Finally, the difference between relative and geocentric sea level can be significant in places where vertical land motion is present.This can be caused by the ongoing glacial isostatic adjustment of the solid earth, but also by local subsidence from groundwater extraction and sediment compaction and loading.

The construction of sea-level change records which reconcile satellite measurements (e.g. radar altimetry, satellite gravimetry, lidar) with terrestrial measurements (GNSS stations, tide gauges and terrestrial gravimetry) on both global and regional level remains a challenging topic. This working group aims to increase the understanding of local/regional geophysical signals present in geodetic measurements, with the aim of encouraging a more widespread use of geodetic datasets in multi-disciplinary fields.


  • Encourage the use of geodetic datasets for multi-disciplinary studies related to sea-level changes.
  • Communicate the need for a consistent treatment of observations and models of sea-level change and vertical land motion to non-geodetic scientific communities.
  • Advance the science of regional and global sea-level research by identifying open questions and gathering stateof-the-art work.
  • Communicate and coordinate activities with other relevant working groups (specifically: Geodesy for the Cryosphere), in particular on the topic of vertical land motion.

Program of Activities

  • Summarize and gather state-of-the-art papers on sea level on the IAG website for non-geodetic audiences.
  • Create an inventory of geodetic datasets useful for sea-level research, to be organised according to agreed standards and made freely available. Provide and gather, under a creative commons license, free to use visuals for communicating aspects of (regional) sea-level change and its (geodetic) observing system.
  • Schedule a yearly strategy meeting to review the past year and define tasks for the upcoming year.
  • Organize inter-JWG communication directly related to the study of vertical land motion, involving participants from the JWG Geodesy for the Cryosphere (e.g., shared web-page on IAG site, mutual participation in yearly strategy meetings).
  • Communicate activities through IAG’s social media accounts.
  • Report activities back to relevant IAG working groups.


  • Adrian Borsa (USA)
  • Francisco Calafat (UK)
  • Don Chambers (USA)
  • Sönke Dangendorf (Germany)
  • Thomas Frederikse (USA)
  • Ropesh Goyal (India)
  • Erik Ivins (USA)
  • Marta Marcos (Spain)
  • Alvaro Santamaria (France)
  • Aimée Slangen (Netherlands)
  • Karen Simon (Netherlands)
  • Giorgio Spada (Italy )
  • Guy Woppelmann (France)

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