EGU2020-10685
https://doi.org/10.5194/egusphere-egu2020-10685
EGU General Assembly 2020
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

The Barents Sea Benthic Silica Cycle and its Sensitivity to Change: a Stable Isotopic and Reaction-Transport Model Study

James Ward1,2, Felipe Sales de Freitas1,2, Hong Chin Ng1, Katharine Hendry1, Sandra Arndt2, Rebecca Pickering3,4, Sian Henley5, Rachael Ward1, Christian März6, and Johan Faust6
James Ward et al.
  • 1University of Bristol, Earth Sciences, United Kingdom of Great Britain and Northern Ireland (JamesPJ.Ward@bristol.ac.uk)
  • 2Université Libre de Bruxelles, Brussels, Avenue Franklin Roosevelt 50, 1050, Belgium
  • 3Dauphin Island Sea Lab, Dauphin Island, AL 36528, USA
  • 4University of South Alabama, Mobile, AL 36688, USA
  • 5The University of Edinburgh, Edinburgh, EH9 3FF, UK
  • 6University of Leeds, Leeds, LS2 9JT, UK

Biogeochemical cycling of silicon (Si) in the high latitudes has an important influence on the marine Si budget. The Barents Sea is divided aproximately equally into Arctic and Atlantic water (ArW and AW respectively) domains.  However, increases in the temperature and inflow of AW across the Barents Sea opening is driving an expansion of the AW realm. While the sensitivity of pelagic processes pertaining to primary production is receiving increasingly more attention, less is known of the effect on the benthic Si cycle. This knowledge gap could prove integral, as the flux of Si across the sediment-water interface (SWI) from Arctic shelf sediments could be up to 20% higher than that of riverine sources. This benthic flux is largely controlled by early diagenetic processes in sediment pore waters, including biogenic silica (bSi) dissolution and authigenic precipitation.

To improve our understanding of benthic Si dynamics in the Barents Sea and examine its sensitivity to future change, we analysed pore water and sediment samples from both the AW and ArW realms between 2017-2019 for dissolved silica (dSi) concentrations and stable silicon isotopic compositions. Moreover, to determine the composition and content of bSi, as well as Si sorbed onto metal oxides, we conducted a sequential digestion of surface sediment. Following this we coupled our analyses with reaction transport modelling to further improve our mechanistic understanding of the system and to quantitatively disentangle the relative importance of these diagenetic processes to pore water Si chemistry and benthic fluxes.

Our work suggests that both interannual and spatial variability of dSi are increased in the southern, AW region of the Barents Sea. Benthic flux estimates for the southern sites have been found to more than double (~30 to 100 mmol m-2 yr-2) between cruise years, compared to a more consistent flux in the north (~80 mmol m-2 yr-2). Therefore, future Atlantification of the northern region may enance the variability of dSi supply from the benthos to bottom waters, with potential consequences for diatom productivity in the region.

How to cite: Ward, J., Sales de Freitas, F., Chin Ng, H., Hendry, K., Arndt, S., Pickering, R., Henley, S., Ward, R., März, C., and Faust, J.: The Barents Sea Benthic Silica Cycle and its Sensitivity to Change: a Stable Isotopic and Reaction-Transport Model Study, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10685, https://doi.org/10.5194/egusphere-egu2020-10685, 2020.

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