Variability in manometric sea level from reanalyses and observation-based products over the Arctic and North Atlantic oceans and the Mediterranean Sea

Abstract

Abstract. Regional variations in the mass component of sea level (manometric sea level) are intimately linked with the changes in the water cycle, volume transports, and inter-basin exchanges. Here, we investigate the consistency at the regional level of the manometric sea level from the Copernicus Marine Service Global Reanalysis Ensemble Product (GREP) and compare with observation-based products deduced from either gravimetry (GRACE missions) or altimetry and in situ ocean observations (sea level budget, SLB, approach) for some climate-relevant diagnostics such as interannual variability, trends, and seasonal amplitude. The analysis is performed for three basins (the Mediterranean Sea and Arctic and North Atlantic oceans) and indicates very different characteristics across the three. The Mediterranean Sea exhibits the largest interannual variability, the Arctic Ocean the largest trends, and the North Atlantic a nearly linear increase that is highly correlated to global barystatic sea level variations. The three datasets show significant consistency at both the seasonal and the interannual timescales, although the differences in the linear trends are sometimes significant (e.g. GRACE overestimates the trend in the Arctic and underestimates it in the Mediterranean Sea when compared to the other products). Furthermore, the Gravity Recovery and Climate Experiment (GRACE) and GREP data prove to be mutually more consistent than SLB in most cases. Finally, we analyse the main modes of climate variability affecting the manometric sea level variations over the selected ocean basins through regularised regression; the North Pacific Gyre Oscillation, the Arctic Oscillation, and the Atlantic Multidecadal Oscillation are proven to be the most influential modes for the North Atlantic Ocean, Mediterranean Sea, and Arctic Ocean manometric sea levels, respectively.