Baltic Sea reanalysis from Copernicus Marine Service – soaked in local knowledge

A regional reanalysis is like a good local restaurant: it builds on local knowledge and focus is on local specialities. For the Baltic Sea, one of the most important local ‘specialities’, or features, is the gateway: the narrow and shallow Danish Straits where the salty North Sea water mass meets with the fresh Baltic Sea water. If this very important process of inflow of saline and oxygen-rich water from the North Sea into the Baltic Sea is not modelled correctly, the results will be of insufficient quality, and not represent the ocean accurately. Currently, global ocean models cannot run with sufficiently high resolution, nor do they focus on local features required to simulate the Baltic Sea adequately. This requires a regional ocean model. Here we present the CMEMS high-resolution ocean reanalysis for the Baltic Sea covering the 30 year period 1993 to 2023. The reanalysis consists of the physical state as well as the bio-geo-chemical state and the waves. Preliminary results from 2 on-going tasks will also be presented: 1) extending the reanalysis back in time to 1980 and 2) expanding the data assimilation from the present parameters (SST and in-situ temperature and salinity profiles) to include sea ice concentration, nutrients and oxygen.