The Copernicus global 1/12° oceanic and sea ice reanalysis

Abstract

<p>The GLORYS12V1 system is a global eddy-resolving physical ocean and sea ice reanalysis at 1/12° resolution covering the 1993-present altimetry period, designed and implemented in the framework of the Copernicus Marine Environment Monitoring Service (CMEMS). All the essential ocean physical variables from this reanalysis are available with free access through the CMEMS data portal.</p><p>The GLORYS12V1 reanalysis is based on the current CMEMS global real-time forecasting system, apart from a few specificities that are detailed in this manuscript. The model component is the NEMO platform driven at the surface by atmospheric conditions from the ECMWF ERA-Interim reanalysis. Ocean observations are assimilated by means of a reduced-order Kalman filter. Along track altimeter sea level anomaly, satellite sea surface temperature and sea ice concentration data and in situ temperature and salinity (T/S) vertical profiles are jointly assimilated. A 3D-VAR scheme provides an additional correction for the slowly-evolving large-scale biases in temperature and salinity.</p><p>The performance of the reanalysis is first addressed in the space of the assimilated observations and shows a clear dependency on the time-dependent in situ observation system, which is intrinsic to most reanalyses. The general assessment of GLORYS12V1 highlights a level of performance at the state-of-the-art and the reliability of the system to correctly capture the main expected climatic interannual variability signals for ocean and sea ice, the general circulation and the inter-basins exchanges. In terms of trends, GLORYS12V1 shows a higher than observed  warming trend together with a lower than observed global mean sea level rise.</p><p>Comparisons made with an experiment carried out on the same platform without assimilation show the benefit of data assimilation in controlling water masses properties and their low frequency variability. Examination of the deep signals below 2000 m depth shows that the reanalysis does not suffer from artificial signals even in the pre-Argo period.</p><p>Moreover, GLORYS12V1 represents particularly well the small-scale variability of surface dynamics and compares well with independent (non-assimilated) data. Comparisons made with a twin experiment carried out at ¼° resolution allows characterizing and quantifying the strengthened contribution of the 1/12° resolution onto the downscaled dynamics.</p><p>In conclusion, GLORYS12V1 provides a reliable physical ocean state for climate variability and supports applications such as seasonal forecasts. In addition, this reanalysis has strong assets to serve regional applications and should provide relevant physical conditions for applications such as marine biogeochemistry. In a near future, GLORYS12V1 will be maintained to be as close as possible to real time and could therefore provide a relevant reference statistical framework for many operational applications.</p>

Assessing the Impact of the Assimilation of SWOT Observations in a Global High-Resolution Analysis and Forecasting System Part 1: Methods

“…The retained values are 21 km for ω −1 k and 48 days for ω −1 f . The values used by the current global highresolution CMEMS GLORYS12 reanalysis (Lellouche et al, 2021) are 64 km and 24 days. As a consequence, the current CMEMS system retains a narrower spectral band.…”

Subseasonal‐to‐Seasonal Forecast Skill in the California Current System and Its Connection to Coastal Kelvin Waves

“…To characterize intraseasonal ocean wave variability in the historical record, we use the GLORYS ocean reanalysis version 12v1 (Lellouche et al., 2021). Generated by the Copernicus Marine Environmental Monitoring Service (CMEMS), GLORYS offers daily mean and monthly mean ocean variables at 1/12° horizontal resolution with 50 vertical levels.…”

The Role of Eddies in the North Atlantic Decadal Variability

“…In this study we use two sets of global ocean reanalyses produced by Mercator Ocean International including the Global Ocean Reanalysis 2 version 4 (GLORYS2V4, hereafter G4, Storto et al, 2019) at 1 /4 degree (eddy permitting), and the Global Ocean Reanalysis 12 version 1 (GLORYS12V1, hereafter G12, Lellouche et al, 2021) at 1/12 degree horizontal resolution (eddy resolving), both covering the period from 1993 to 2016. A robust validation of these products can be found in quality information documents (Garric and Parent, 2017;Drèvillon et al, 2021a).…”