Project Details
Projekt
Reconstructing Environmental Effects of Freshwater-Seawater Dynamics via Submarine Groundwater Discharge (REEF-SGD)
Applicants
Professor Dr. Norbert Frank; Dr. Sophie Warken
Subject Area
Geology
Term
since 2026
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 569219220
This project aims to investigate submarine groundwater discharge (SGD) in tropical and subtropical regions by employing a novel, multiproxy approach that combines high-resolution coral geochemistry, satellite observations, and climate data. SGD is increasingly recognized as an important yet underexamined source of freshwater, nutrients, and trace elements to coastal environments, influencing both reef ecosystems and global biogeochemical cycles. However, quantifying its variability across different geological settings and through time remains challenging. The project focuses on four diverse study sites—Tahiti, Hawai’i, the Seychelles, and the Yucatán Peninsula—each offering unique hydrogeological conditions, from volcanic basaltic aquifers to karstic limestone platforms and coral atoll systems. By analysing modern coral skeletons, we will reconstruct SGD fluxes over annual to decadal timescales using uranium isotopes (δ234U), which reliably track groundwater-derived U distinct from typical seawater values. Together with Ba/Ca and rare earth element (REE) ratios this will help differentiate fresh groundwater from recirculated saline discharge and identify local environmental influences (e.g., upwelling or riverine inputs). By capturing subannual to decadal signals, the project will illuminate the temporal variance of SGD, revealing both episodic extremes and longer-term trends in freshwater fluxes. The research strategy integrates satellite-based GRACE data on groundwater storage, sea-level reconstructions, and precipitation records, alongside climate indices such as ENSO, IOD, and NAO. This framework will test five core hypotheses regarding the controls on SGD, including the influence of hydrogeology, sea-level changes, and climate-driven precipitation on discharge variability. Spectral and wavelet analyses will quantify correlations between coral-derived geochemical signals and major climate modes. Ultimately, this project will fill key knowledge gaps in understanding how SGD responds to sea-level fluctuations and climatic extremes—including hurricanes and monsoonal rainfall—and how these interactions affect tropical coral reef ecosystems. The outcomes will inform global hydrological models by incorporating more accurate SGD estimates and elucidate long-term freshwater availability in tropical coastal zones. By generating a publicly accessible dataset of δ234U, Ba/Ca, and REE measurements, the project provides a foundation for future interdisciplinary studies on coastal resource management and reef sustainability in a changing climate.
DFG Programme
Priority Programmes
International Connection
Mexico, USA
Cooperation Partners
Professor Dr. Juan Pablo D' Olivo Cordero; Dr. Nancy Prouty
