Using Satellite Observations to Improve Our Understanding of Future Regional Sea Level Change and its Impacts

PI: R. Steven Nerem

Co-Is/Collaborators:

John Fasullo, Kris Karnauskas, University of Colorado, Jan Lenaerts, Kristy Tiampo, Mike Willis

Background:

Sea level change is an important indicator of how the Earth is responding to climate change, and it is also a key driver of associated socioeconomic impacts. Therefore, understanding how much sea level will rise in the future, and how it will impact coastal populations centers and infrastructure, is an objective of paramount importance. Satellite measurements, such as satellite altimetry, satellite gravity, and satellite photogrammetry, have the potential to revolutionize our understanding of sea level rise and its impacts. We propose to investigate several different topics important to understanding regional sea level change and its impacts.

Expected Significance:

1. We will produce improved regional sea level projections. We envision three types of projections: (a) Short-term (about 20 years) data-driven extrapolations of the satellite measurements, and (b) Hybrid extrapolations combining the best parts of the observational record and climate modeling for projecting sea level over the next century, and (c) developing improved climate model projections by evaluating the CMIP6 models against the satellite observations.
2. By developing satellite-based techniques (DEMs, coastal mean sea level, etc.) for estimating the socioeconomic impacts of sea level rise, we can perform impact assessments for regions of the world where there is relatively little in situ geodetic and tide-gauge infrastructure, such as developing countries, sparsely populated areas of the U.S. coastline, and other remote, but economically essential, regions on Earth (National Parks, etc.). This would provide a valuable set of tools for assessing the impacts of future sea level change on the human populations that are most vulnerable.
3. Estimates of vertical land motion from DInSAR will be useful for understanding how vertical land motion affects relative sea level change, and in particular how it might significantly exacerbate the impacts of sea level change in areas where long-term subsidence is occurring, provided we separate long and short-term changes in crustal motion.

Objectives:

1. Develop a better understanding of the observed regional patterns of sea level change from satellite altimetry so that we can separate out the Forced Response (FR) into contributions by aerosols and greenhouse gases (GHGs) and reveal the regional pattern of future sea level change including the role of regional climate dynamics such as wind forcing.
2. Develop short-term (about 20 years) data-driven extrapolations of the satellite altimeter record of sea level change and the satellite gravity record of ice mass loss to complement decadal predictions based on coupled models.
3. Develop hybrid longer-term (about 100 years) projections of regional sea level change by combining observations (patterns of sea level change and ice mass loss) with climate model projections.
4. Evaluate models and their projections of global and regional sea level change using satellite altimetry and satellite gravity measurements. This would include both coupled climate models as well as ice sheet models and would use a variety of metrics to assess model performance. These evaluations will be used to determine the most reliable models to use for future projections, assess the uncertainties in these models, and possibly develop improved projections from a calibrated ensemble of the model projections.
5. Perform sea level impact studies at many sites around the world by producing DEMs (from Worldview stereo satellite imagery) and estimates of vertical crustal motion (from DInSAR and GNSS measurements). We will compute future inundation maps using all of these measurements combined with the sea level projections in objectives (2-4).

Deliverables (e.g. Datasets, Tools)