EGU22-5359
https://doi.org/10.5194/egusphere-egu22-5359
EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Hydrology and -chemistry of a tidal basin (Königshafen, North Sea): A water isotope perspective

Michael E. Böttcher1,2,3, Anna-Kathrina Jenner1, Carla Nantke1, Cátia Milene E. von Ahn1, Iris Schmiedinger1, Antonia Schell1,2, Roeser Patricia1, Ramona Riedel4, Sebastian Janßen5, Benjamin S. Gilfedder4, and Nils Moosdorf5
Michael E. Böttcher et al.
  • 1Leibniz IOW, Geochemistry & Isotope Biogeochemistry, Warnemünde, Germany (michael.boettcher@io-warnemuende.de)
  • 2Marine Geochemistry, University of Greifswald, Greifswald, Germany
  • 3Interdisciplinary Faculty, University of Rostock, Rostock, Germany
  • 4Limnic Research Station, University of Bayreuth, Germany
  • 5ZMT Bremen and University of Kiel, Germany

The role that of fresh surface and ground water sources play on the coastal water balance, element balances, and the associated biogeochemical processes is currently a matter of intense debate and investigation. The measures of fresh and saline water mixing in coastal areas have been found to be challenging, however stable water isotopes (O-16, O-17, O-18), in combination with further hydrochemical tracers, provide a valuable tool to identify different sources, that are furthermore linked to different biogeochemical processes, e.g. impacting the benthic and pelagic carbon cycle.

In the present communication, we report on combined investigations in pore and surface waters of Königshafen Bay (North Frisian island Sylt, Germany), a tidal area in the eastern North Sea. In addition, tidal cycles at the outlet of the bay were sampled. Results are compared to potential surface and subterrestrial fresh water endmembers, open North Sea, submarine groundwater discharge in the backbarrier tidal area of Spiekeroog, as well as the Elbe river estuary. Besides dissolved major and minor elements, the stable water isotope composition is used to characterize the temporal and spatial distribution of different water sources to the bay and the seasonal dynamics in the water column. Porewater gradients indicate different degrees of freshening, locally already in the top 50 cm below the seafloor with spatial heterogeneity. Different fresh water endmembers are indicated both by the water isotope and hydrochemical signatures. It turns that at least two fresh water sources can be identified for sediments under SGD impact, that differ in composition from surface water sources draining into the southern North Sea. Further work is on the way to investigate the dynamics in the (sub)surface fresh water sources for the tidal basin and the link to other geochemical tracers, as well as the coupling to the dissolved carbon system on different temporal and spatial scales.

  

The investigations are supported by the DFG-project KiSNet, the BMBF project COOLSTYLE (CARBOSTORE), the DAAD, the DFG project Baltic Transcoast, and Leibniz IOW.

How to cite: Böttcher, M. E., Jenner, A.-K., Nantke, C., von Ahn, C. M. E., Schmiedinger, I., Schell, A., Patricia, R., Riedel, R., Janßen, S., Gilfedder, B. S., and Moosdorf, N.: Hydrology and -chemistry of a tidal basin (Königshafen, North Sea): A water isotope perspective, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5359, https://doi.org/10.5194/egusphere-egu22-5359, 2022.