Massentransporte und Massenverteilungen im System Erde  
    A closer look at the Earth’s surface processes by merging geodetic and oceanographic datasetsA closer look at the Earth’s surface processes by merging geodetic and oceanographic datasets  
 

 

A closer look at the Earth’s surface processes by merging geodetic and oceanographic datasets

Up to now, short-period mass transport processes, like continental hydrology and ocean dynamics, have been studied using individual datasets. Information from multiple datasets can however be combined to obtain more accurate estimates of mass transport and improve our knowledge of ocean and land processes.

 

In the framework of JIGOG, we have developed a joint inversion scheme, which combines weekly data from satellite gravimetry (GRACE, Gravity Recovery and Climate Experiment), a GPS network solution (IGS) and gridded ocean bottom pressure from a numerical ocean model (FESOM, Finite Element Sea-Ice Ocean Model) developed at AWI.

 

For these combination results we find a good agreement, down to weekly time scales, with time series from in-situ bottom pressure recorders (figure 1). In particular, sub-monthly variability appears to be significant at higher latitudes (figure 2). Furthermore, although GRACE by itself cannot sense geocenter motion variations, we see that the addition of GRACE improves the accuracy and separability of the geocenter motion and low-degree spherical harmonic coefficients.

 

The inversion results are available to SPP1257 users in form of spherical harmonic sets and gridded maps. External users can obtain the datasets upon request (roelof(at_sign)gfz-potsdam.de).

Figure 1. Comparison of the GRACE+GPS+FESOM inversion results with series from in situ bottom pressure recorders in the Southern Indian ocean. Correlations between the combination (black) and the local series (blue) vary between 0.7-0.8.
Figure 2. Temporal autocorrelation between the GRACE+GPS+FESOM inversion results for ocean bottom pressure, for various time lags. The correlation quickly decreases within the time span of a month.

References: Rietbroek, R., S.-E. Brunnabend, C. Dahle, J. Kusche, F. Flechtner, J. Schröter, and R. Timmermann (2009), Changes in total ocean mass derived from GRACE, GPS, and ocean modeling with weekly resolution, J. Geophys. Res., 114, C11004, doi:10.1029/2009JC005449 , final draft