Abstract's details
Estimations of oceanic trends (heat, salt, steric and mass budget) in Mercator Ocean global reanalysis
CoAuthors
Event: 2022 Ocean Surface Topography Science Team Meeting
Session: Science I: Climate data records for understanding the causes of global and regional sea level variability and change
Presentation type: Type Poster
Contribution: not provided
Abstract:
Over the past years, Mercator Ocean International (MOI) has been regularly developing and upgrading its global ocean physical reanalysis through improvements in the ocean model, assimilation scheme and assimilated data sets. In the framework of Copernicus Marine Service (CMS), MOI developed a global eddy-resolving physical reanalysis GLORYS12v1 at 1/12° (Lellouche et al. 2021) and participated to the global multi-reanalysis product GREP at ¼° resolution (Storto et al. 2018). MOI global reanalyses are coupled physical ocean and sea ice systems covering the 1993-present altimetry period. Oceanic observations are assimilated using a reduced-order Kalman filter. Along track altimeter Sea Level Anomaly, satellite sea surface temperature and sea ice concentration, and in situ temperature and salinity vertical profiles are jointly assimilated. All the essential oceanic physical variables from these reanalyses are available with free access through the CMS data portal (https://marine.copernicus.eu/).
Current MOI reanalyses, and particularly GLORYS12v1, have shown their reliability to correctly reproduce the main expected climatic interannual variability signals for ocean and sea ice, the general circulation, and the inter-basins exchanges. Nevertheless, GLORYS12v1 shows an unexpected marked warming trend together with an underestimation of the global mean sea level rise (Lellouche et al. 2021).
In this presentation we show how, through a better balance between the mass entering the system and the steric signal, we plan to tackle the latter issue in the next MOI reanalysis. Considering that NEMO ocean model is not able to reproduce the steric effect (Boussinesq approximation), and that the global mass can be estimated thanks to gravimetry measurements (GRACE), we propose to constrain the global mass toward satellite estimation and to diagnose the global steric elevation from the reanalysis system. Advantages and weaknesses of this method are first discussed. Then, results obtained from experiments performed with a global ¼° resolution are presented with a focus on different components of sea level trend (mass, steric, thermosteric, halosteric) at global and local scale and for different ocean layers. Comparisons with observed data supplement this study.
Current MOI reanalyses, and particularly GLORYS12v1, have shown their reliability to correctly reproduce the main expected climatic interannual variability signals for ocean and sea ice, the general circulation, and the inter-basins exchanges. Nevertheless, GLORYS12v1 shows an unexpected marked warming trend together with an underestimation of the global mean sea level rise (Lellouche et al. 2021).
In this presentation we show how, through a better balance between the mass entering the system and the steric signal, we plan to tackle the latter issue in the next MOI reanalysis. Considering that NEMO ocean model is not able to reproduce the steric effect (Boussinesq approximation), and that the global mass can be estimated thanks to gravimetry measurements (GRACE), we propose to constrain the global mass toward satellite estimation and to diagnose the global steric elevation from the reanalysis system. Advantages and weaknesses of this method are first discussed. Then, results obtained from experiments performed with a global ¼° resolution are presented with a focus on different components of sea level trend (mass, steric, thermosteric, halosteric) at global and local scale and for different ocean layers. Comparisons with observed data supplement this study.