A water isotope approach to fresh water sources for the North German coast

Michael E. Böttcher1, Ernst O. Böttcher2, Tillman M.C. Böttcher3, Julia Westphal1, Marko Lipka1, Iris Schmiedinger1, Vera Winde1
1 Geochemie & Isotopenbiogeochemie, Leibniz Institute für Ostseeforschung (IOW)
2 21339 Lüneburg
3 CvO Universität Oldenburg

P 9.1 in Groundwater-surface water-interactions - processes and methods

The hydrological cycle is reflected by specific water isotope signatures found in precipitation, surface, and ground waters under the influence by climate boundary conditions. Since fresh waters of different evolution paths and ages enter the coastal areas of the North and Baltic Sea it is expected that they may carry characteristic stable isotope signatures. Informations about the specific composition of different fresh water sources allows for a use in mixing models for the origin of coastal waters. Typically, investigations focus on the partitioning of the isotopes H-1, H-2, O-16, and O-18, but also the new tracer O-17 is included.

We investigated the multi-isotope composition of different sources for fresh waters at sites with relevance for the southern coastal North and Baltic Sea areas (precipitation, river waters, coastal wells, coastal beach springs, fresh waters emerging in and from coastal marine sediments (SGD), coastal peatlands). The composition of precipitation (rain, snow) at different locations in Northern Germany (Lüneburg, Oldenburg, Warnemünde) and the Netherlands (Texel Island) was analyzed to derive local meteoric water lines. Results are compared to measurements at the GNIP station in Cuxhaven (NW-Germany) and the GMWL and meteorological characteristics, like water sources amount- and below-cloud effects for precipitation are evaluated.

Additionally, the hydrogeochemical composition of fresh water samples is analyzed, too, and combined with the multi-isotope results, to better define source-related signatures.

Acknowledgements: The presented research is supported by the DFG GK Baltic TRANSCOAST, and Leibniz IOW.