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 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.

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.

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.

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.

Regional hunting numbers for Grey seals 2011-2014.

These data sets spans multiple oceanographic, chemical, physical, and geomorphological layers. Bathymetric complexity was captured through broad- and fine-scale Bathymetric Position Indices, along with seafloor depth, slope, and ruggedness. Seafloor characteristics included sediment type* and wave exposure estimates. Water column properties were described using measurements of oxygen, salinity, temperature, pH, and nutrient concentrations (nitrate and phosphate) at both bottom and surface layers, each described by mean values and standard deviations. Stratification were characterized by Secchi depth, mixed layer depth, and sea ice concentration. Productivity was approximated by chlorophyll-a concentration. Surface and subsurface variability in wave conditions and satellite-derived sea surface temperature were also collected. Swedish sediment information published with permission from the Swedish Maritime Authority: Decision 23-06009 (12 Sep 2024). To prepare the layers, we applied a procedure designed to iteratively extrapolate missing values in a raster layer by applying a moving window mean filter. It first aligns the input raster to the target grid (Baltic Sea grid at 250 m resolution) using a specified projection method, then repeatedly fills in missing data based on the mean of neighboring cells within a circular window of user-defined size (2 in this case). This iterative process continues until either all missing values are filled or a predefined number of iterations is reached, with early termination if convergence occurs. This procedure ensures that extrapolation respects the spatial extent of the reference grid and provides progress updates during processing. This metadata covers following predictor layers: Bottom Oxygen (Mean) - Mole concentration of dissolved molecular oxygen in sea water at the bottom (µmol/L) Bottom Oxygen (CV) - Coefficient of variation of dissolved molecular oxygen in sea water at the bottom (%) Bottom Salinity (Mean) - Sea water salinity at seafloor (PSU) Bottom Salinity (CV) - Coefficient of variation of sea water salinity at seafloor (%) Bottom Temperature (Mean) - Sea water potential temperature at seafloor (ºC) Bottom Temperature (CV) - Coefficient of variation of sea water potential temperature at seafloor (%) Broad-Scale Bathymetric Position Index - Bathymetric position index, ratio of average depth within 4 km radius to average depth within 20 km radius (m) Chlorophyll-a (Mean) - Mass concentration of chlorophyll a in sea water (mg/m³) Chlorophyll-a (CV) - Coefficient of variation of mass concentration of chlorophyll a in sea water (%) Coarse substrate - Coarse substrate probability of occurrence (%) Depth attenuated exposure at the seafloor - Depth attenuated exposure at the seafloor Distance from the coastline - Distance from the coastline (m) Distance from the nearest river - Distance from the nearest river (m) Fine-Scale Bathymetric Position Index - Bathymetric position index, ratio of average depth within 500 m radius to average depth within 5 km radius (m) Hard substrate - Hard substrate probability of occurrence (%) Mixed Layer Depth (Mean) - Ocean mixed layer thickness defined by sigma theta (m) Mixed Layer Depth (CV) - Coefficient of variation of ocean mixed layer thickness defined by sigma theta (%) Sand substrate - Sand substrate probability of occurrence (%) Sea Ice Concentration (Mean) - Sea ice fraction (%) Sea Ice Concentration (CV) - Coefficient of variation of sea ice fraction (%) Sea surface height (Mean) - Sea surface height above sea level Sea surface height (CV) - Coefficient of variation of sea surface height above sea level (%) Seafloor Depth - Depth in meters below sea surface (m) Seafloor Rugosity within 3 cell radius - Rugosity within 3 cell radius Seafloor Slope - Steepness of the seafloor slope in degrees (Degrees) Secchi Depth (Mean) - Secchi depth of sea water (m) Secchi Depth (CV) - Coefficient of variation of secchi depth of sea water (%) Soft substrate - Soft substrate probability of occurrence (%) Surface Ammonium (Mean) - Mole concentration of ammonium in sea water (µmol/L) Surface Ammonium (CV) - Coefficient of variation of mole concentration of ammonium in sea water (%) Surface Carbon Dioxide (Mean) - Surface partial pressure of carbon dioxide in sea water (µatm) Surface Carbon Dioxide (CV) - Coefficient of variation of surface partial pressure of carbon dioxide in sea water (%) Surface Nitrate (Mean) - Mole concentration of nitrate in sea water (µmol/L) Surface Nitrate (CV) - Coefficient of variation of mole concentration of nitrate in sea water (%) Surface Oxygen (Mean) - Mole concentration of dissolved molecular oxygen in sea water at the surface (µmol/L) Surface Oxygen (CV) - Coefficient of variation of mole concentration of dissolved molecular oxygen in sea water at the surface (%) Surface pH (Mean) - Sea water pH reported on total scale (pH) Surface pH (CV) - Coefficient of variation of sea water pH reported on total scale (%) Surface Phosphate (Mean) - Mole concentration of phosphate in sea water(µmol/L) Surface Phosphate (CV) - Coefficient of variation of mole concentration of phosphate in sea water (%) Surface Primary Productivity (Mean) - Net primary production of biomass expressed as carbon per unit volume in sea water (mg C/m³/day) Surface Primary Productivity (CV) - Coefficient of variation of net primary production of biomass expressed as carbon per unit volume in sea water (%) Surface Salinity (Mean) - Sea water salinity at surface (PSU) Surface Salinity (CV) - Coefficient of variation of sea water salinity at surface (%) Surface Temperature (Mean) - Sea water potential temperature at surface (ºC) Surface Temperature (CV) - Coefficient of variation of sea water potential temperature at surface (%) Terrain Aspect - Aspect, i.e., direction in which the slope is facing out of 360 degrees (N, S, E, W) Wave Height Max (Mean) - Sea surface wave significant height (m) Wave Height Max (CV) - Coefficient of variation of sea surface wave significant height (%) * Swedish sediment information published with permission from the Swedish Maritime Authority: Decision 23-06009 (12 Sep 2024).

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

The fishing intensity map displays data provided in C-square (0.05 x 0.05 degrees) converted to 1x1 km raster 2011-2016. The value of raster cell is subsurface swept area ratio. The data does not cover Russian waters.