Abstract
Abstract. Estimates of 3D ocean circulation are needed to improve our understanding of ocean dynamics and to assess their impact on marine ecosystems and Earth climate. Here we present the OMEGA3D product, an observation-based time series 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 the data-driven CMEMS-ARMOR3D weekly reconstruction of temperature and salinity as well as ERA Interim fluxes. Outside the equatorial band, vertical velocities were retrieved in the upper 1500 m at 1∕4∘ nominal 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 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 reanalyses spanning a comparable time period but based on data assimilation in ocean general circulation numerical models. The full OMEGA3D product (released on 31 March 2020) is available upon free registration at https://doi.org/10.25423/cmcc/multiobs_glo_phy_w_rep_015_007 (Buongiorno Nardelli, 2020a). The reduced subset used here for validation and review purposes is openly available at https://doi.org/10.5281/zenodo.3696885 (Buongiorno Nardelli, 2020b).
Highlights
The recognition of the key role played by the oceans in the Earth system led the United Nations to proclaim the Decade of Ocean Science for Sustainable Development (2021–2030)
Providing accurate reconstructions of 3D ocean circulation time series is a fundamental part of this effort, aimed at better describing ocean dynamics and assessing their responses and feedbacks to natural and anthropogenic pressures
Mean vertical velocity patterns at 100 m depth and associated variability are computed here from OMEGA3D, SODAv3.4.2 and ECCOv4r3 over their 23-year overlapping period (1993–2015), focusing on the domain covered by the OMEGA3D product and excluding the 5◦ N–5◦ S band and coastal areas
Summary
The recognition of the key role played by the oceans in the Earth system led the United Nations to proclaim the Decade of Ocean Science for Sustainable Development (2021–2030). Major efforts will be made in the years to analyse state-of-the-art observations and models and provide the indispensable knowledge basis to preserve the marine environment through effective, science-informed policies. Two main complementary approaches can be followed to this end: the assimilation of observations in global ocean circulation numerical models (Carrassi et al, 2018; Moore et al, 2019; Stammer et al, 2016) and the combination of diagnostic models and purely data-driven reconstructions. The latter is presently more widely used for surface circulation
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