For the Helsinki Commission (HELCOM), annual waterborne basin inflows of total nitrogen (N) and total phosphorus (P) were compiled for the seven main Baltic Sea sub-basins (Sect. 1.1). In order to allow the utilization within a regional Earth System or ocean modelling framework, we redistributed these nutrient loads spatially and temporally using a dataset of bias corrected discharge that was generated with the Hydrological Discharge (HD) model (Sect. 1.2). Following the spatial and temporal downscaling procedure described in Sect. 1.3, we generated a dataset of daily riverine and annual direct nutrient loads (N and P) into the Baltic Sea at 1/12° resolution from 1901-2019. Detailed information you can find in the specified sections of the attached PDF https://www.wdc-climate.de/ui/entry?acronym=HELCOM_HD_info In November 2023, the bias corrected discharges were improved after a bug was found (see "Bias corrected high resolution river runoff over Europe (Version 1.0)", https://doi.org/10.26050/WDCC/Biasc_hr_riverro_Eu). Consequently, the redistributed HELCOM loads of nitrogen (N) and phosphorus (P) were also updated using the improved bias corrected discharge dataset (see Version 1.1: https://www.wdc-climate.de/ui/entry?acronym=HELCOM_HD_v1_1). However, changes in the N and P loads into the Baltic Sea are marginal. The annual basin sums are the same, only daily values may have slightly changed.

For the Helsinki Commission (HELCOM), annual waterborne basin inflows of total nitrogen (N) and total phosphorus (P) were compiled for the seven main Baltic Sea sub-basins (Sect. 1.1). In order to allow the utilization within a regional Earth System or ocean modelling framework, we redistributed these nutrient loads spatially and temporally using a dataset of bias corrected discharge that was generated with the Hydrological Discharge (HD) model (Sect. 1.2). Following the spatial and temporal downscaling procedure described in Sect. 1.3, we generated a dataset of daily riverine and annual direct nutrient loads (N and P) into the Baltic Sea at 1/12° resolution from 1901-2019. Detailed information you can find in the specified sections of the attached PDF https://www.wdc-climate.de/ui/entry?acronym=HELCOM_HD_info In November 2023, the bias corrected discharges were improved after a bug was found (see "Bias corrected high resolution river runoff over Europe (Version 1.0)", https://doi.org/10.26050/WDCC/Biasc_hr_riverro_Eu). Consequently, the redistributed HELCOM loads of nitrogen (N) and phosphorus (P) were also updated using the improved bias corrected discharge dataset. However, changes in the N and P loads into the Baltic Sea are marginal. The annual basin sums are the same, only daily values may have slightly changed.

Under the heading of the OSPAR convention (Sect. 1.1), the IGC-EMO database of daily freshwater inflows and nutrient loads was compiled by van Leeuwen and Lenhart (2021), which covers the major rivers discharging into the Baltic Sea, North Sea and Northeast Atlantic (Sect. 1.2). In this database, the data are distributed in separate ASCII files according to the respective country and river. In order to allow an easier utilization within a regional Earth System or ocean modelling framework, we mapped the IGC-EMO data onto the flow grid of the European 1/12° domain of the Hydrological Discharge (HD) model (Sect. 1.3). This mapping was done for daily time series of discharge, total nitrogen (N), total phosphorus (P) and Silicate for the period 1940-2022 following the procedure described in Sect. 1.4. Detailed information you can find in the specified sections of the attached PDF https://www.wdc-climate.de/ui/entry?acronym=IGC-EMO_HD_info

As part of the joint federal state measurement program for the North and Baltic Seas, the parameter "particulate organic nitrogenin sea water" was determined in seawater.

As part of the joint federal state measurement program for the North and Baltic Seas, the parameter "nitrite (NO2-N) in sea water" was determined in seawater.

As part of the joint federal state measurement program for the North and Baltic Seas, the parameter "nitrite (NO2-N) in sea water" was determined in seawater.

As part of the joint federal state measurement program for the North and Baltic Seas, the parameter "dissolved nitrogen in sea water" was determined in seawater.

As part of the joint federal state measurement program for the North and Baltic Seas, the parameter "particulate organic nitrogenin sea water" was determined in seawater.

As part of the joint federal state measurement program for the North and Baltic Seas, the parameter "dissolved organic nitrogen in sea water" was determined in seawater.

As part of the joint federal state measurement program for the North and Baltic Seas, the parameter "dissolved nitrogen in sea water" was determined in seawater.