What Determines the Shape of a Pine‐Island‐Like Ice Shelf?

Ice shelf shape directly controls ocean heat intrusions, melting near the grounding line, and buttressing. Little is known about what determines ice‐shelf shape because ice‐ocean coupled simulations typically aim at projecting Antarctica's contribution to sea‐level rise and they do not resolve small‐scale ice‐ocean interactive processes. We conduct ice‐ocean coupled simulations for an idealized high‐resolution, Pine‐Island‐like model configuration. We show that ocean melting and ice stretching caused by acceleration thin the ice shelf from the grounding line toward the ice shelf front, consistent with previous studies. In the across‐flow direction, ocean melting and ice advection cancel each other out and flatten the ice shelf. More than one‐third of the ice thinning from grounding line to ice front can be attributed to ocean melting at depths shallower than 500 m. Our results emphasize the importance of interactive processes between the entire ice shelf and the ocean for determining the ice shelf shape. Plain Language Summary Antarctic ice flows into the ocean and forms a floating extension of land ice called an ice shelf. The ice shelf shape directly controls the amount of ocean heat intrusions, melting near the grounding line, and buttressing. However, little is understood about ice‐ocean interactive processes determining ice shelf shape because (a) ocean modelers apply a constant cavity geometry, (b) ice modelers mostly assume simplified melting parameterization, and (c) ice‐ocean coupled simulations typically aim at projections of Antarctica's sea‐level contributions and they require long model integration. We conduct ice‐ocean coupled simulations for an idealized high‐resolution Pine‐Island‐like model configuration. Basal melting and ice stretching create a typical ice shelf shape with steep thinning near the grounding line followed by gradual thinning toward the ice shelf front. In the across‐flow direction, ice divergence from the center advects ice toward edges, compensating for melt‐driven thinning and flattening ice shelf shape. We also show that ice melting at shallow depths contributes to about one‐third of ice‐shelf thinning. Although it is thought that ice shelf melting at the grounding line dominantly controls ice shelf behavior, our results suggest the importance of ice‐ocean interactive processes for the entire ice shelf cavity for determining the ice shelf shape. Key Points Ocean melting and ice stretching caused by ice acceleration both