The contribution of solid Earth deformation to sea-level change

Regional relative sea level (RSL) differs from the global mean due largely to Glacial Isostatic Adjustment (GIA), the ongoing deformation of the solid Earth to past land-ice changes. Modelling future GIA contributions to RSL requires knowledge of the evolution of ice extent since the Last Glacial Maximum (LGM, ~20,000 years before present) and rheology of the solid Earth. However, the contribution from solid-Earth deformation is poorly constrained. Understanding of mantle dynamics and its impact on solid Earth deformation can be improved through modelling of observations of the seismic cycle using a novel approach. Earthquakes induce significant stress change into the asthenosphere and provoke transient accelerated deformation. Studies of post-seismic deformation provide inference on the rheological structure of the mantle, which can improve GIA models. Recently, we formulated a new methodology to image the effective viscosity in Earth’s interior using surface deformation data as a linear inverse problem, which has yet to be tested at a global scale. 

Here, we will reconstruct global-scale Earth deformation since the LGM using a global RSL compilation. Unlike instrumental constraints contaminated by other processes, RSL data predominantly record land-ice melting and the associated GIA response. Despite the importance, a global RSL compilation following a standardized approach does not exist. We propose bringing together sea-level researchers producing regional RSL compilations to create the first global synthesis. Through this project, we will be able to achieve:

1. A global synthesis of sea-level data since the LGM.
2. Inferring constraints on the rheological parameters of the lower crust and the asthenosphere.
3. Inversion of GPS velocity field for strain and strain rate in the asthenosphere.
4. Evaluation of the impact of lateral heterogeneity in the Earth model on GIA predictions.
5. A global forward model of GIA since the LGM with lateral variations of mantle viscosity and lithospheric thickness.

Funding Sources: 

  • Earth Observatory of Singapore
  • Ministry of Education, Singapore

Project Years: 


EOS Team: 

Principal Investigator


Nicole Khan, University of Hong Kong

Qiang Qiu, Department of Earth Sciences, University of Southern California