Project Details
Projekt
Reconciling ocean mass change and GIA from satellite gravity and altimetry (OMCG-2)
Subject Area
Geodesy, Photogrammetry, Remote Sensing, Geoinformatics, Cartography
Term
from 2016 to 2024
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 313917204
Ocean mass change (OMC) is a major component of the sea level budget. Knowledge of OMC is required when inferring steric sea level variability from altimetry, with consequences for ocean heat content estimates and for understanding the Earth energy budget. The GRACE satellite gravity mission has been instrumental for recent OMC estimates, and GRACE-derived OMC is increasingly used in regional studies. Yet, published estimates of OMC, from essentially the same GRACE data, tend to disagree even at the global scale. Recent studies vary from 1.2 to 2.0 mm/a, often claiming unrealistic errors and budget closure at the 0.1-0.2 mm/a level. This is a major obstacle for inferring regional contemporary ocean heat content change from altimetry, e.g. in order to localize the sinks and transports of heat in the ocean. The problem is thus of particular significance for understanding and predicting regional sea level change in South-East Asian seas. The central hypothesis of this project, unchanged to the first phase of the SPP, is that these discrepancies are mostly related to (1) method issues in the analysis of the GRACE data and (2) the unsolved problem of removing the effect of Glacial Isostatic Adjustment (GIA) from the GRACE data. The first phase (OMCG-1) has resolved crucial methodological discrepancies in direct and inverse OMC estimates. In addition, OMCG-1 has improved the understanding of key elements for regional separating the GIA effect from combined geodetic satellite observations. OMCG-1 is further developing the global inverse approach and starting to incorporate results from the regional GIA separation studies into the global framework. The second phase (OMCG-2) will a) investigate improved methods of deriving fingerprints from model ensembles, b) investigate independent estimation of shallow and deep steric components, c) investigate the potential gain of integrating in-situ Argo data, d) implement a time-series-based parameter estimation approach for regional separation of GIA and ice mass change f) assign apparent biases in regional GIA estimates by the use of GNSS, and g) finally, incorporate altimetry over ice sheets as an additional observable in the global inversion to aid the separation of GIA. We will directly quantify physical processes that contribute to sea-level change at global and regional scale. Moreover, we will provide data-sets for modeling projects inside and outside the SPP. Especially our regionalized data for Northern Europe and Southeast Asia will help to improve projections in these areas.
DFG Programme
Priority Programmes
