Lead
Prof. Dr. Gudrun Massmann (Hydrology and Landscape Hydrology Group)
PhD student
Nele Grünenbaum (Hydrology and Landscape Hydrology Group)
Research scientist
Dr. Janek Greskowiak (Hydrology and Landscape Hydrology Group)
Objective
Budgeting nutrients and trace elements that enter the oceans via submarine groundwater discharge (SGD) requires detailed knowledge on the groundwater flow system and its dynamics in the subterranean estuary, especially for meso- to macrotidal high energy-beaches which are currently understudied. Spiekeroog Island was chosen as study site because of its exposed high-energy beach system with a meso-tidal amplitude. A combination of field investigations and numerical modelling in this study will help to extent the previous information about subterranean estuaries, quantifying subsurface residence times and delineating flow and salinity patterns.
Groundwater-Surface Water Dynamics
In coastal aquifers, SGD includes a terrestrial freshwater component as well as saline proportion originating from tidally driven recirculation of seawater. However, there is hardly any field data about the actual volumes of water circulating in the intertidal zone in such high energy systems. Accordingly, it is necessary to collect long time data about the dynamics and volumes of submarine groundwater discharge depending on tides, storm floods and seasonal groundwater recharge variations.
Self-made lysimeters and seepage meters are used to estimate the volumes of infiltrating seawater and exfiltration groundwater. The rates are assumed to be dependent on the beach morphology and tidal amplitudes. Therefore, a 3D-laser scanner is used to determine the change in the beach topography on short and medium time scales. Additionally, observation wells are installed and equipped with data loggers to monitor water levels and electrical conductivities with a high frequency over several tidal cycles.
Numerical Modelling
Numerical models are set up with the density-dependent groundwater flow modeling code SEAWAT in order to process the collected field data and existing hydrological and hydrogeological information of the barrier island. The models will continuously be updated, refined and recalibrated as soon as new data becomes available within the later stages of proposed projects. Tritium-helium measurements in the intertidal zone and the islands freshwater lens will help to improve the knowledge of groundwater pathways and residence times in the subterranean estuary and serve as calibration constraint in the numerical models.
Internships
Johannes Degen: Identifizierung von Zirkulationsmustern im Intertidal eines Hochenergiestrandes anhand von hydrochemischen Parametern des Porenwassers
Nils Schelling: Räumliche Muster des Porenwasserchemismus im Intertidal am Standort Spiekeroog
Mirijam Hannah Steinmetz: Seasonal variations in beach topography and nutrient cycling
Lukas Brennecke: Bestimmung von In- und Exfiltrationsraten bei mesotidalen Verhältnissen an einem hochenergetischen Strand am beispiel einer Barriereinsel (Spiekeroog, Nordwestdeutschland)
Alina Harms: Untersuchung der (ungesättigten) Rezirkulation am Strand Spiekeroogs von In- bis Exfiltration
Presentations at national and international symposia
Grünenbaum N, Greskowiak J,Sültenfuß J, Massmann G (2019) Quantification of in- and exfiltration rates from the subterranean estuary of a high energy beach systesm. 1-day workshop on SGD, Bremen, Germany (Oral presentation).
Grünenbaum N, Greskowiak J, Sültenfuß J, Massmann G (2019) Hydrogeologische Untersuchungen im subterranen Ästuar unter einem hochenergetischen und meso tidalen Strand. ARGE-Tagung, Bremen, Germany (Oral presentation).
Greskowiak J, Ahrens J, Ahmerkamp S, Grünenbaum N, Kossack M, Schnetger B, Ehlert C, Holtappels M, Beck M, Pahnke K, Brumsack H-J, Massmann G (2018). Modelling reactive transport of Si and 222Rn to constrain tide-induced seawater rates at a meso-tidal beach. SWIM, Gdansk, Poland (Oral presentation).
Grünenbaum N, Greskowiak J, Sültenfuß J, Massmann G (2018) Messung und Modellierung der Grundwasseraltersverteilung im subterranen Ästuar unter einem hochenergetischen und mesotidalen Strand einer Barriereinsel (Spiekeroog, Nordwestdeutschland). 26. FH-DGGV-Tagung, Bochum, Germany (Oral presentation).
Grünenbaum N, Greskowiak J, Massmann G, Harms A, Waska H (2017) Recirculation rates within beach sediments under meso-tidal conditions (Spiekeroog, Northern Germany). IAH44th, Dubrovnik, Croatia (Oral presentation).
Grünenbaum N, Greskowiak J, Massmann G (2017) Investigation of the recirculation on the beach of Spiekeroog from in- to exfiltration. EGU, Wien, Austria (Poster presentation).
Grünenbaum N, Greskowiak J, Massmann G (2017) Investigation of the recirculation on the beach of Spiekeroog from in- to exfiltration. PhD Student Meeting, Erlangen, Germany (Oral presentation).