This dataset is the first dedicated SMOS Sea Surface Salinity (SSS) product for the Baltic basin to enhance the science capabilities in the Baltic region and help to fill the gaps and grand challenges identified by the scientific community. These new product has been created under the funded ESA project ITT Baltic+ Salinity dynamics (4000126102/18/I-BG). This basin is one of the most challenging regions for the satellite SSS retrieval. The available EO-based SSS products are quite limited in terms of spatio-temporal coverage and quality. This is mainly due to technical limitations that strongly affect the brightness temperatures (TB), such as the high contamination by interferences and the contamination close to land and ice edges. Moreover, the sensitivity of TB to SSS changes is very low and dielectric models present limitations in this low salinity regime. Baltic+ L4 SSS product comprises 9 years (2011-2019) of daily maps at 0.05 degrees. A detailed explanation of the product algorithms and validation can be found at http://bec.icm.csic.es/doc/BEC_PD_SSS_Baltic_L3_L4.pdf and in the publication: Gonzalez-Gambau et al., “First SMOS Sea Surface Salinity dedicated products over the Baltic Sea“, Earth System Science Data, 2021 We present here the seasonal averaged Baltic+ L4 SSS products for the period 2011-2019. The daily Baltic+ L4 SSS products can be downloaded from the BEC FTP service (sftp://becftp.icm.csic.es) in the directory OCEAN/SSS/SMOS/Baltic/v1.0/L4/daily/

The availability of deep water habitat is based on the occurrence of H2S and describes the suitability of the bottom areas for the Baltic Sea biota, with regard to oxygen conditions of the near-bottom waters. The data used to produce the layer was provided by the Leibniz-Institut für Ostseeforschung Warnemünde (IOW) for the years 2016-2021.

Regional hunting numbers for Harbour seals 2011-2014.

Polluting ship accidents is based on reporting of shipping accidents done by HELCOM Contracting Parties to produce annual within HELCOM MARITIME group. Data was available for 2011-2013

Digitized from Mariners’ Routeing Guide Baltic Sea ISBN 978-3-89871-771-7 (http://www.helcom.dk/map/). The line features are divided in categories, indicated by the the ZONE_TYPE attribute: 0 - Deep water route areas; 1 - Deep water route center line; 4 - Recommended route center; 6 - Traffic separation line; and 7 - Traffic separation scheme.

The dataset contains total landings of herring for years 2011-2016 reported per ICES statistical rectangles (tonnes / ICES rectangle) under EU Joint Research Centre’s data collection framework for fisheries data. Russian data extracted from ICES annual reports.

'Availability of deep water habitat, based on occurrence of H2S' layer describes the suitability of the bottom areas for the Baltic Sea biota, with regard to oxygen conditions of the near bottom waters. The data used to produce the layer was received from Leibniz-Institut für Ostseeforschung Warnemünde (IOW): - areas (polygons) with hydrogen sulfide (H2S) based on point measurements and modelling. Five time periods / year, for years 2011-2016 (altogether 30 layers). The polygons were converted to raster layers in a way, that for each time period (6 years, 5 time periods each year), areas with H2S got a value 0, other areas got the value 1. All layers were summed, (representing 6 years, 5 time periods each year, maximum value 30) and data was normalised. For more detailed information on the data used, please see Feistel et al. 2016.

Regional hunting numbers for Grey seals 2011-2014.

Screening activities for component Hazardous wastes on the Leningrad and Kaliningrad Region territories have been fulfilled within the BALTHAZAR project. The main goal of the Project BALTHAZAR is assistance in protection of the Baltic Sea from pollution through reducing of loading caused by agricultural entities (AE) and hazardous wastes. The component Hazardous wastes is focused on inventory of large landfills and estimation of current regime in hazardous wastes management. The main task of screening was to study impact of large landfills on environment of the Leningrad Oblast and Kaliningrad Oblast and to reveal the landfills causing the main loading on the Baltic Sea with pollutants. Screening results report on Leningrad: http://www.helcom.fi/stc/files/Projects/BALTHAZAR/ScreeningReportForPublication-May2011.pdf Screening results report on Kaliningrad: http://www.helcom.fi/stc/files/Projects/BALTHAZAR/KaliningradScreeningResults-1.pdf

The dataset contains total landings of cod for years 2011-2016 reported per ICES statistical rectangles (tonnes / ICES rectangle) under EU Joint Research Centre’s data collection framework for fisheries data. Russian data extracted from ICES annual reports.