Imaging Brine Infiltration and Basal Marine Ice in Larsen C Ice Shelf, Antarctic Peninsula, From Borehole Measurements and Transient Electromagnetics

The presence and nature of marine ice in ice shelves is important, yet difficult to determine. We present transient electromagnetic results spanning 10 km across a suture zone of Larsen C Ice Shelf (LCIS), Antarctica, supported by central borehole measurements. Our results indicate the presence of two ice-shelf layers. The uppermost layer, ∼300 m thick, has resistivity 10³−10⁶ Ωm. We interpret this as meteoric ice, overlying a lower shelf layer 25–56 m thick with resistivity 3–20 Ωm, consistent with permeable basal marine ice. This reconstruction closely matches modeled marine-ice thicknesses in the area. The porosity of this layer is 0.18–0.40, higher than measured farther down-flow, suggesting the layer consolidates once formed. Within the upper layer at 78.5 m depth, we identify a 2.5 m thick layer, likely linked to brine infiltration. These heterogeneities in ice shelf properties should be accounted for in future LCIS stability assessments.