| Summary: | The rapidly-changing Thwaites Ice Shelf is crucial for understanding ice-shelf instability and its implications for sea-level rise from Antarctica. Fractures play a significant role in this region but are poorly characterized, especially regarding their vertical depth. To address this gap, we developed a robust workflow that adapts to surface topography complexities to characterize time-varying fracture vertical properties over Thwaites using ICESat-2 altimetry measurements. We derived seasonal flow velocities from Sentinel-1 data and analyzed climate reanalysis data to examine flow-fracture interactions in the context of oceanic and atmospheric changes. The results revealed distinct fracturing and flow patterns between the eastern and western sectors of the ice shelf. Significant fracturing was observed along the shear margin and near the grounding line in the eastern sector, correlating with flow speed increases exceeding 90% at shear zones. In contrast, the western glacier tongue exhibited a less progressive fracturing pattern, with an active fracture zone downstream of the historical grounding line and overall flow deceleration. This is likely due to the stabilizing effects of grounding-zone geometry, a subglacial sill, and increased coupling to the slower-moving eastern sector. Atmospheric and oceanic reanalysis data suggest that atmosphere-sea-ice-ocean interactions could destabilize an ice shelf through shallow oceanic warming. Warm winters, reduced sea ice, and favorable winds and ocean currents can cause shoaling of warm Circumpolar Deep Water, facilitating access of warm waters to thin, structurally vulnerable areas such as shear margins and basal channels. This intensifies fracturing and triggers damage-flow-acceleration feedback that could lead to eventual ice-shelf destabilization.
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