Detection of sea level fingerprints derived from GRACE gravity data

Mass changes of ice sheets, glaciers and ice caps, land water hydrology, atmosphere, and ocean cause a nonuniform sea level rise due to the self-attraction and loading effects called sea level fingerprints (SLF). SLF have been previously derived from a combination of modeled and observed mass fluxes from the continents into the ocean. Here we derive improved SLF from time series of time variable gravity data from the Gravity Recovery and Climate Experiment (GRACE) mission for April 2002 to October 2014. We evaluate the GRACE-derived SLF using ocean bottom pressure (OBP) data from stations in the tropics, where OBP errors are the lowest. We detect the annual phase of the SLF in the OBP signal and separate it unambiguously from the barystatic sea level (BSL) at two stations. At the basin scale, the SLF explain a larger fraction of the variance in steric-corrected altimetry than the BSL, which has implications for evaluating mass transport between ocean basins. Plain Language Summary As ice sheets and glaciers and ice caps melt into the ocean, the pattern of regional sea level rise is nonuniform and tracked via the sea level fingerprints. Here we provide the first observational evidence that the SLF calculated from satellite observations match the record from ocean stations that measure mass changes over time, i.e., the Gravity Recovery and Climate Experiment-based satellite technique correctly captures the distribution of freshwater fluxes to the ocean and the signal is large enough to be detected by ocean in situ observations in the tropics. The results are critical to improve regional projections of sea level rise and its impact on coastlines and human systems.