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Iceberg A‐68 separated from the Larsen C Ice Shelf in July 2017 and the impact of this event on the local ocean circulation has yet to be assessed. Here, we conduct numerical simulations of ocean dynamics near and below the ice shelf pre‐ and post‐calving. Results agree with in situ and remote observations of the area as they indicate that basal melt is primarily controlled by wintertime sea‐ice formation, which in turn produces High Salinity Shelf Water (HSSW). After the calving event, we simulate a 50% increase in HSSW intrusion under the ice shelf, enhancing ocean heat delivery by 30%. This results in doubling of the melt rate under Gipps Ice Rise, suggesting a positive feedback for further retreat that could destabilize the Larsen C Ice Shelf. Assessing the impact of ice‐front retreat on the heat delivery under the ice is crucial to better understand ice‐shelf dynamics in a warming environment. Plain Language Summary: In July 2017, the Larsen C Ice Shelf, Antarctica, calved one of the largest icebergs ever observed: A‐68. The impact of this event on the ocean circulation near and below the ice remains unknown. Our simulations from an ocean model suggest that the iceberg separation may have led to increased ocean heat delivery under the ice, yielding more vigorous bottom melt. Key Points: We present ocean simulations under Larsen C in good agreement with local ocean, basal melt and sea‐ice observationsThe removal of iceberg A‐68 yields heat intrusion to increase by 30% causing melt around Gipps Ice Rise to doubleOcean models need to consider ice‐front retreat events and realistic ice‐shelf geometry to accurately project sub‐shelf ocean circulation [ABSTRACT FROM AUTHOR]

Greater landward velocities were recorded after six megathrust earthquakes in subduction zone regions adjacent to the ruptured portion. Previous explanations invoked either increased slip deficit accumulation or plate bending during postseismic relaxation, with different implications for seismic hazard. We investigate whether bending can be expected to reproduce this observed enhanced landward motion (ELM). We use 3D quasi‐dynamic finite element models with periodic earthquakes. We find that afterslip downdip of the brittle megathrust exclusively produces enhanced trenchward surface motion in the overriding plate. Viscous relaxation produces ELM when a depth limit is imposed on afterslip. This landward motion results primarily from in‐plane elastic bending of the overriding plate due to trenchward viscous flow in the mantle wedge near the rupture. Modeled ELM is, however, incompatible with the observations, which are an order of magnitude greater and last longer after the earthquake. This conclusion does not significantly change when varying mantle viscosity, plate elasticity, maximum afterslip depth, earthquake size, megathrust locking outside of the rupture, or nature and location of relevant model boundaries. The observed ELM consequently appears to reflect faster slip deficit accumulation, implying a greater seismic hazard in lateral segments of the subduction zone. Plain Language Summary: After six large earthquakes during which one tectonic plate slides under another, the surface of the upper plate hundreds of kilometers away along the plate's edge moved away from the edge faster than before. Proposed explanations include faster motion of the lower plate, greater friction between the two plates, and bending of the plates. We use three‐dimensional numerical simulations to investigate whether bending can explain the observations. We find that flow in the mantle under the upper plate in response to the earthquake produces bending that results in the plate moving away from its edge faster than before, as long as there is an impediment to the horizontal motion some distance from the edge. This impediment is provided by the depth limit to the zone where the lower plate can move faster in response to the earthquake. However, the simulated motion is slower and lasts less than the observed motion. Modifying the simulation's mechanical properties and earthquake size does not change this conclusion. The observed motion therefore appears to result from a greater difference between the large‐scale relative motion of the two plates and the relative motion at their contact, indicating future earthquakes should be larger or occur earlier. Key Points: Postseismic in‐plane bending of the overriding plate enhances landward velocities far from the earthquakeThe modeled landward velocity changes due to bending are smaller, more temporally variable than observed, especially considering afterslipVelocity changes associated with six earthquakes indicate slip deficit accumulates faster locally [ABSTRACT FROM AUTHOR]