Investigating Submarine Groundwater Transmissivity in Svalbard Fjord Sediments through the Analyses of Physical Properties and Chemical Composition

We investigate submarine groundwater transmissivity within Svalbard fjord sediments, where offshore freshened groundwater (OFG) was confirmed through analyses of dissolved chloride concentration and water isotope signatures (δ¹⁸O and δ²H). The analyses are comprised of physical, mechanical, and chemical attributes of three cores recovered from Tempelfjorden and Hornsund fjords. Multi-Sensor Core Logger (MSCL) analyses provide high-resolution physical characteristics of the sediment cores, including bulk density, p-wave velocity, magnetic susceptibility, and electrical resistivity. These are integrated with X-ray computed tomography (CT) images, acquired with a Geotek rotating X-ray CT system (RXCT), to identify sedimentary facies, which are used to investigate internal core structures. Discrete measurements of grain density and grain size are used to calculate sediment porosity and to estimate the permeability. Our results indicate a heterogeneous sediment matrix with frequent drop stones and ice-rafted debris interlayered with finer-grained materials. We hypothesize that the sediment matrix packaging and configuration is an important control for the sediment permeability and thus for freshened groundwater transmissivity in the sediments of these fjords. This work is not only relevant for characterizing groundwater transmissivity in Svalbard's fjords but also will contribute to ongoing geological modeling efforts. Our findings pave the way for hydrogeological simulations, enhancing our understanding of OFG occurrence, emplacement mechanisms, and OFG volumes over successive glacial cycles.