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Topic: Sea Level Rise from Mass Gain and Thermal Expansion

Goal: Study what contributes to global mean sea level rise using satellite measurements.

Introduction: Global mean total sea level variations measured by satellite altimeters (TOPEX/Poseidon, Jason-1,2,3) from 1993 to 2021 show a linear rate of 3.36 +/-0.4 mm/yr. The global mean sea level rise is contributed by two main components: (1) eustatic sea level rise and (2) steric sea level rise. The eustatic sea level rise is the expansion of the oceans due to increasing mass, is mostly due to the melting of grounded ice sheets, and can be measured by satellite gravimeters (e.g., GRACE). The steric sea level rise is the expansion of the oceans due to increasing volume, involves both ocean warming and freshening, and can be measured by in-situ conductivity temperature depth profilers (e.g., ARGO, XBT). Disentangling these contributions is very important because it helps us understand ocean heat uptake and project sea level rise.

Datasets:

  • MEaSUREs-SSH multi mission altimetry (based on TOPEX/Poseidon, Jason-1.2.3)
    • Location: /home/jovyan/shared/data/gmsl/GMSL_TPJAOS_5.1_199209_202203.*
  • GRACE water storage (equivalent water height over land and ocean)
    • Location: /home/jovyan/cmda_data/cmip5/others/nasa_grace_*
  • NOAA World Ocean Atlas steric sea level products (based on ARGO, XBT, etc)
    • Location: /home/jovyan/shared/data/gmsl/noaa_gmssl.nc

Scripts:

  • sea_level_rise_v2.ipynb - Main notebook for exercises.

Questions:

  • Use MEaSUREs-SSH multi mission altimetry to fit linear and quadratic (i.e. accelerating) trends to global mean sea level. If these trends are simply projected forward, how much would we anticipate sea level to rise between now and 2100? What issues are associated with such simple projections? What types of processes may be missed?
  • For the period where the records overlap, compare the contribution of mass change (from GRACE) and steric change (from NOAA WOA) to the total rise in GMSL. Why are the total, mass, and steric records available at such different temporal resolutions? Where do the records agree and differ? Do the steric and mass records add up to the total record? What are some possible reasons for the discrepancies between the NOAA derived steric sea level trend and that which can be obtained from the residual between altimetry and mass change?
  • The ocean is gaining mass from the land. Compare timeseries of grace_over_ocean and grace_over_land (discuss possible sources of difference). Map changes in land water storage. Where is most of the mass loss from the land occurring? Do you see anything surprising?

Topic Scientist:  Angelica Rodriguez (angelica.rodriguez@jpl.nasa.gov)

Project Server: https://hub.jpl-cmda.org