Evolution of Shear-Zone Fractures Presages the Disintegration of Thwaites Eastern Ice Shelf

Abstract

Thwaites Eastern Ice Shelf (TEIS) is a partially confined floating extension of Thwaites Glacier, anchored by an offshore pinning point at its northern terminus. Over the past two decades, the shelf has experienced progressive fracturing around a prominent shear zone upstream of its pinning point, gradually compromising its structural integrity. Here we present an analysis of shear-zone fracture evolution from 2002 to 2022 and its control on the flow dynamics of the ice shelf using satellite remote sensing and in situ GPS observations. We compiled multi-year statistics of fracture length and orientation from Landsat and Sentinel-1 imagery and compared their changes with evolving flow dynamics and surface strain rates. Ongoing disintegration driven by the shelf's shearing against the pinning point occurred in two stages: propagation of large shearing fractures approximately parallel to flow earlier in the record, followed by the rapid formation of smaller tensile fractures approximately perpendicular to flow later in the record. We also observed velocity perturbations originating from the shear zone and propagating across the main ice shelf, observationally demonstrating the direct impact that shear-zone disintegration has on the dynamics of TEIS.