Can we resolve the basin-scale sea-level trend budget from GRACE ocean mass?

Understanding sea-level changes at a regional scale is important for improving local sea-level projections and coastal management planning. Sea-level budget (SLB) estimates derived from the sum of observation of each component close for the global mean. The sum of steric and GRACE ocean mass contributions to sea level calculated from measurements does not match the spatial patterns of sea surface height trends from satellite altimetry at one degree grid resolution over the period 2005-2015. We investigate potential drivers of this mis-match aggregating to sub-basin regions and find that the steric plus GRACE ocean mass observations do not represent the small-scale features seen in the satellite altimetry. In addition there are discrepancies with large variance apparent at the global and hemispheric scale. Thus the SLB closure on the global scale to some extent represents a cancellation of errors. The SLB is also sensitive to the GIA correction for GRACE and to altimery orbital altitude. Discrepancies in the SLB are largest for the Indian-South Pacific Ocean region. Taking the spread of plausible sea level trends, the SLB closes at the ocean-basin-scale (2σ) but with large spread of magnitude, one third or more of the trend signal. Using the most up-to-date observation products, our ocean-region SLB does not close everywhere and consideration of systematic uncertainties diminishes what information can be gained from the SLB about sea-level processes, quantifying contributions and validating Earth observation systems.