Applicant

Professor Dr. Reinhard Drews
Eberhard Karls Universität Tübingen
Fachbereich Geowissenschaften
Arbeitsgruppe Geologie und Geodynamik
Schnarrenbergstraße 94-96
72076 Tübingen

Project description 

The polar ice sheets are accelerating sea-level rise (Otosaka et al., 2023), and much of the mass loss is driven by processes at the ice–ocean boundaries, where melt rates are highest. Differences in how these processes are implemented account for a significant spread in model predictions (e.g., Goelzer et al. 2020) for Greenland and Berends et al. (2023) for Antarctica). Much progress has occurred in coupling ice- and ocean models that capture the dynamics of the ice-ocean boundary, which is typically defined as a binary grounding line along an idealized ice-bed-ocean contact point (De Rydt et al., 2024). However, observations (Rignot et al., 2024) and modelling (Bradley et al., 2024) indicate that it is better described as a spatially distributed, estuarine grounding zone that involves a two-way exchange of salt water from the ocean and freshwater from the ice sheet (Parizek, 2024). Processes within this system can trigger a self-amplifying, destabilizing feedback, leading to significantly enhanced basal melting well inland of the idealized grounding line (Bradley et al., 2024). A major unknown in estuarine zones is the role of ocean tides, which are not yet incorporated into model physics because observational evidence is limited. This is where our proposal can provide the critical data and process understanding needed to advance predictions. We hypothesize that water-exchange processes between ice and ocean under marine-terminating glaciers can be identified through centimetre-scale vertical uplift and subsidence of the ice surface, as well as temporally varying water properties at the ice front. The spatiotemporal variability of these metrics will reveal the conditions under which ocean water intrudes upstream. To test this, our project team combines two instruments capable of capturing both metrics concurrently: a terrestrial radar interferometer (TRI) (Drews et al., 2021) and water sampling by uncrewed aerial vehicle (UAV) (Hansen et al., 2025). Greenland provides an ideal environment to test our hypothesis. The processes we observe there serve as an analogue for Antarctic grounding zones, which, due to the absence of fjords and surrounding rock cliffs, cannot be accessed with this instrumentation. The project is timely, as it will synergize with a concurrent major research vessel campaign in the same area (by the Danish Centre of Excellence CIFAR), which will capture far-field ocean forcing and fjord dynamics to complement our grounding-zone measurements. Observations of changing ocean properties and concurrent ice-dynamic changes on tidal timescales have not yet been achieved, and will provide much-needed information on a number of first-order phenomena in glaciology, including grounding-zone migration, temporal changes in subglacial hydrological systems, ice–ocean interactions, and variability in fluxes to the oceans.

DFG Programme Infrastructure Priority Programmes

Term since 2026