Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Volume 14, issue 8
Biogeosciences, 14, 2113-2131, 2017
https://doi.org/10.5194/bg-14-2113-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 14, 2113-2131, 2017
https://doi.org/10.5194/bg-14-2113-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 25 Apr 2017

Research article | 25 Apr 2017

Nutrient transports in the Baltic Sea – results from a 30-year physical–biogeochemical reanalysis

Ye Liu1, H. E. Markus Meier2,1, and Kari Eilola1 Ye Liu et al.
  • 1Swedish Meteorological and Hydrological Institute, Norrköping, Sweden
  • 2Leibniz Institute for Baltic Sea Research Warnemünde, Rostock, Germany

Abstract. Long-term oxygen and nutrient transports in the Baltic Sea are reconstructed using the Swedish Coastal and Ocean Biogeochemical model (SCOBI) coupled to the Rossby Centre Ocean model (RCO). Two simulations with and without data assimilation covering the period 1970–1999 are carried out. Here, the weakly coupled scheme with the Ensemble Optimal Interpolation (EnOI) method is adopted to assimilate observed profiles in the reanalysis system. The reanalysis shows considerable improvement in the simulation of both oxygen and nutrient concentrations relative to the free run. Further, the results suggest that the assimilation of biogeochemical observations has a significant effect on the simulation of the oxygen-dependent dynamics of biogeochemical cycles. From the reanalysis, nutrient transports between sub-basins, between the coastal zone and the open sea, and across latitudinal and longitudinal cross sections are calculated. Further, the spatial distributions of regions with nutrient import or export are examined. Our results emphasize the important role of the Baltic proper for the entire Baltic Sea, with large net transport (export minus import) of nutrients from the Baltic proper into the surrounding sub-basins (except the net phosphorus import from the Gulf of Riga and the net nitrogen import from the Gulf of Riga and Danish Straits). In agreement with previous studies, we found that the Bothnian Sea imports large amounts of phosphorus from the Baltic proper that are retained in this sub-basin. For the calculation of sub-basin budgets, the location of the lateral borders of the sub-basins is crucial, because net transports may change sign with the location of the border. Although the overall transport patterns resemble the results of previous studies, our calculated estimates differ in detail considerably.

Publications Copernicus
Download
Short summary
From the reanalysis, nutrient transports between sub-basins, between the coastal zone and the open sea, and across latitudinal and longitudinal cross sections, are calculated. Further, the spatial distributions of regions with nutrient import or export are examined. Our results emphasize the important role of the Baltic proper for the entire Baltic Sea. For the calculation of sub-basin budgets, the location of the lateral borders of the sub-basins is crucial.
From the reanalysis, nutrient transports between sub-basins, between the coastal zone and the...
Citation
Share