A multi-year timeseries of observation-based 3D horizontal and vertical quasi-geostrophic global ocean currents
Abstract. Estimates of 3D ocean circulation are needed to improve our understanding of ocean dynamics and to assess its impact on marine ecosystems and Earth climate. Here we present the OMEGA3D product, an observation-based timeseries of (quasi) global 3D ocean currents covering the 1993–2018 period, developed by the Italian Consiglio Nazionale delle Ricerche within the European Copernicus Marine Environment Monitoring Service (CMEMS). This dataset was obtained by applying a diabatic quasi-geostrophic (QG) diagnostic model to CMEMS data-driven ARMOR3D weekly reconstruction of temperature and salinity and ERA-Interim fluxes. Outside the equatorial band, vertical velocities were retrieved in the upper 1500 m, at nominal ¼° resolution, and successively used to compute the horizontal ageostrophic components. Root mean square differences between OMEGA3D total horizontal velocities and totally independent drifter observations at two different depths (15 m and 1000 m) decrease with respect to corresponding estimates obtained from zero-order geostrophic balance, meaning that estimated vertical velocities can also be deemed reliable. OMEGA3D horizontal velocities are also closer to drifter observations than velocities provided by a set of re-analyses spanning a comparable time period, but based on data assimilation in ocean general circulation numerical models. The full OMEGA3D product (released on 31st of March 2020) is available upon free registration at https://doi.org/10.25423/cmcc/multiobs_glo_phy_w_rep_015_007. The reduced subset used here for validation and review purposes is openly available at https://doi.org/10.5281/zenodo.3696885 (Buongiorno Nardelli, 2020).