Offshore freshened groundwater in Baffin Bay, reconstructing modern and paleo-fluid salinities in materials from IODP Expedition 400.

• Applicant: Dr. Philip Staudigel
• Subject Area: Geology ; Hydrogeology, Hydrology, Limnology, Urban Water Management, Water Chemistry, Integrated Water Resources Management ; Mineralogy, Petrology and Geochemistry
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 565961027

Due to the global reliance on coastal groundwater for drinking water, and its vulnerability to saltwater intrusion, there is increased scientific interest in offshore freshened groundwater (OFG). During the drilling carried by IODP Expedition #400 off the West Greenland Margin (WGM), a previously undiscovered unit of freshened water was discovered at a depth of 600 - 800 m, about 20 m below the sea floor, which was up to 200 m thick at some sites. There are several candidate sources for this freshened water, including hydrate destabilization and basal melting of glaciers during previous glacial maxima. In contrast to many previously described groundwater systems, the freshwater in West Greenland is not connected to the land mass, and thus is actively being displaced by modern seawater from above. This system therefore offers unique insights into the potential fate of modern coastal freshwater aquifers in regions threatened by sea level rise. Therefore, it is important to characterize the origins of this freshwater, and to study the past variability of groundwater and benthic water in this region. The aim of this project is to isotopically characterize the WGM groundwater in order to constrain potential end-member sources. In addition, the history of groundwater and benthic water temperatures and salinities will be reconstructed using (dual) clumped isotope measurements on bivlaves, glendonites and carbonate concretions. Isotopic analysis of bivalve geochemistry will unlock an archive of benthic temperature and salinity, both important factors governing ice sheet stability. Glendonites (calcite replacing ikaite) potentially record past events where freshwater and seawater were mixing, as modern ikaite is often precipitated from freshwater-seawater mixtures. The presence of glendonites from the Pliocene and Miocene could indicate that fresh groundwater was already present in these periods - a hypothesis that we aim to test using clumped isotope analysis. Carbonate concretions, on the other hand, provide an archive for reconstructing changes in the composition of groundwater over time, as these cemented nodules form during the burial of sediments, and their isotopic composition will reflect the groundwater that was present at that time. This project directly supports the objectives of IODP Expedition 400 by reconstructing temporal variations in the temperature of ocean currents in the WGM from the Miocene to present, which are an important variable governing the stability of its ice sheet. We further contribute by constraining the extent of glacial melting during previous glacial maxima. In addition, our results will be relevant for the upcoming IODP3 Expedition 501, which aims to characterize a freshwater aquifer and its surrounding sediments off the East Coast of the USA.

• DFG Programme: Infrastructure Priority Programmes
• Subproject of: SPP 527: Infrastructure area - International Ocean Drilling Programme³ (IODP³)