Trends and Uncertainties of Regional Barystatic Sea-level Change in the Satellite Altimetry Era

Abstract. Ocean mass change is one of the main drivers of present-day sea-level change (SLC). Also known as barystatic SLC, it is driven by the exchange of freshwater between the land and the ocean, such as melting of continental ice from glaciers and ice sheets, and variations in land water storage. While many studies have quantified the present-day barystatic contribution to global mean SLC, fewer works have looked into regional changes. This study provides a comprehensive analysis of regional barystatic SLC trends since 1993 (the satellite altimetry era), with a focus on the uncertainty budget. We consider three types of uncertainties: intrinsic (the uncertainty from the data/model itself); temporal (related to the temporal variability in the time series); and spatial-structural (related to the location/distribution of the mass change sources). We collect a range of estimates for the individual freshwater sources, which are used to compute regional patterns (fingerprints) of barystatic SLC and analyse the different types of uncertainty. When all the contributions are combined, we find that the barystatic sea-level trends regionally ranges from −0.43 to 2.55 mm year−1 for 2003–2016, and from −0.39 to 2.00 mm year−1 for 1993–2016, depending on the choice of dataset. When all types of uncertainties from all contributions are combined, the total barystatic uncertainties regionally range from 0.62 to 1.29 mm year−1 for 2003–2016, and from 0.35 to 0.90 mm year−1 for 1993–2016, also depending on the dataset choice. We find that the temporal uncertainty dominates the budget, although the spatial-structural also has a significant contribution. On average, the intrinsic uncertainty is almost negligible. The main source of uncertainty is the temporal uncertainty from the land water storage contribution, which is responsible for at least 50 % of the total uncertainty, depending on the region of interest. The second main contributions come from the spatial-structural uncertainty from Antarctica and land water storage, which show that different locations of mass change can lead to trend deviations larger than 20 %. As the barystatic SLC contribution and its uncertainty vary significantly from region to region, better insights into regional SLC are important for local management and adaptation planning.