Next generation of Bluelink ocean reanalysis with multiscale data assimilation: BRAN2020

• Main Authors: Chamberlain, Matthew A., Oke, Peter R., Fiedler, Russell A. S., Beggs, Helen M., Brassington, Gary B., Divakaran, Prasanth
• Format: Text
• Language: English
• Published: 2021
• Subjects: Southern Ocean; Sea ice
• Online Access: https://doi.org/10.5194/essd-2021-194; https://essd.copernicus.org/preprints/essd-2021-194/

BRAN2020 is an ocean reanalysis that combines ocean observations with an eddy-resolving, near-global ocean general circulation model, to produce four-dimensional estimates of the ocean state. The data assimilation system employed is ensemble optimal interpolation, implemented with a new multiscale approach that constrains the broad-scale ocean properties and the mesoscale circulation in two steps. The reanalysis spans January 1993 to December 2019, and assimilates observations of in situ temperature and salinity, as well as satellite sea-level anomaly and sea surface temperature. Reanalysed fields from BRAN2020 generally show much closer agreement to observations than all previous versions with mis-fits between reanalysed and observed fields reduced by over 30 % for some variables. The BRAN2020 dataset is comprised of daily-averaged fields of temperature, salinity, velocity, mixed-layer depth, and sea-level. Reanalysed fields realistically represent all of the major current systems within 75° S and 75° N, excluding processes relating to sea ice, but including boundary currents, equatorial circulation, Southern Ocean variability, and mesoscale eddies. BRAN2020 is publicly-available at https://doi.org/10.25914/6009627c7af03 (Chamberlain et al., 2021b) and is intended for use by the research community.