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Non-belspo (1992-ongoing)

ISMIce - Ice Shelf Marine Ice

Project description

This research project deals with ice-ocean interactions at ice sheet boundaries. The main goal of the project is to study, understand and quantify how ice shelves stability is affected by interactions with ocean water masses, in a changing climate perspective. Focus is put on what is known as “marine ice” i.e. ice formed in the water column below or at the front of ice shelves, as a result of thermohaline circulation loops affecting the water masses in the sub-ice shelf cavity. This ice then floats up and accretes at the bottom of the ice shelf and potentially acts as a welding agent of the large crevasses forming either at the grounding line (where the ice shelf gets afloat) or at ice shelf fronts (degenerating into rifts as iceberg calving proceeds).
The approach is through multiparametric studies of ice from shallow marine ice cores (max. 50 meters) or landfast sea ice cores, in the area fringing the ice shelf. These measurements include: δ180, ice textures and fabrics, bulk salinity, major ions and included particulate matter. Since the project mainly results from a tight collaboration with the Italian “Progetto Nazionale di Ricerce in Antartide”, the area of investigation has been centered on the Terra Nova Bay (Ross Sea) region (Hells Gate and Nansen Ice Shelves). These ice shelves have the peculiar characteristic to show marine ice outcrops at the glacier surface close to the ice shelf front, because of the very strong katabatic winds regime which is also partly responsible of the existence of the Terra Nova Bay polynya. Results indicate a varying intensity of the Deep Thermohaline Convection during the winter (probably driven by major katabatic wind events) and the existence of a Shallow Thermohaline Convection loop, active during the summer in the frontal zone of the ice shelf, as warmer surface waters are forced under the ice shelf’s front by tidal currents. Both convection loops are responsible for marine ice formation in the study area, showing contrasted characteristics.
One of the major peculiarities of marine ice bodies is their very low salinity (down to 0.03 psu) for ice originated from a sea water source. We have proposed a simple two-phase approach model to explain the stable isotope/salinity signal of marine ice that combines fractionation processes occurring during both the individual frazil ice crystal generation and the subsequent consolidation process at the base of the ice shelf, under slow heat conduction.
In parallel with the analytical studies, a model has been developed in collaboration with Drs. A. Khazendar and A. Jenkins, that simulates the marine ice production in rift configurations affecting the ice shelf. It shows, among others, that very high marine ice production rates are the rule, when Ice Shelf Water is transiting under the ice shelf at the rift’s location.

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