The Mercator Ocean global “blue” ocean reanalysis: past, present future

The Copernicus Marine Service is the marine component of the Earth Observation Copernicus program of the European Union. It provides free, regular and systematic authoritative information on the state of the Blue (physical), White (sea ice) and Green (biogeochemical) ocean, at global and regional scales. In this context, Mercator Ocean International develops and proposes global (1/12° and 1/4°) blue and white ocean reanalysis (model/data combinations) covering the 3 last decades, among others reanalysis products. With more than 1.2 Peta octet downloaded and 5000 users in 2023, these reanalyzes are ones of the most more downloaded product of Copernicus Marine catalogue. 

This presentation, firstly, provides a description and an overall assessment of each global blue reanalyzes produced by Mercator Ocean International: the 1/12° (GLORYS12V1) targeting a robust representation of meso-scale activity and the 1/4° resolution which is a member of small multi-model ensemble approach (GREP) distributed by the Copernicus Marine Service. 

Then, we describe the ongoing developments and first assessment of the future version of these reanalyzes. The main improvements concern evolution of the ocean (NEMO) and Assimilation (SAM) codes, the control of the mass and steric repartition, the use of ERA5 atmospheric reanalyze, the switch from 50 to 75 vertical levels for 1/12° reanalysis, the use of interannual river discharges. The first statistical comparisons to observed data (temperature, salinity, sea level) show good results and these new reanalysis release show an improvement of general trends (Ocean Heat Content, steric, thermosteric, halosteric, mass).