Weak relationship between remotely detected crevasses and inferred ice rheological parameters on Antarctic ice shelves

Abstract

Abstract. Over the past decade, a wealth of research has been devoted to the detection of crevasses in glaciers and ice sheets via remote sensing and machine learning techniques. It is often argued that remotely sensed damage maps can function as early-warning signals for shifts in ice shelf conditions from intact to damaged states and can serve as an important tool for ice sheet modellers to improve future sea-level rise predictions. Here, we provide evidence for Filchner-Ronne and Pine Island ice shelves that remotely sensed damage maps are only weakly related to the ice rate factor field A derived by an ice-flow model when inverting for surface velocities. This technique is a common procedure in ice flow models, as it guarantees that any inferred changes in A relate to changes in ice flow measured through observations. The weak relationship found is improved when investigating heavily damaged shear margins, as observed on Pine Island Ice Shelf; yet, even in this setting, this association remains modest. Our findings suggest that many features identified as damage through remote sensing methods are not of direct relevance to present-day ice-shelf flow. While damage can clearly play an important role in ice-shelf processes and thus be relevant for ice-sheet behaviour and sea-level rise projections, our results imply that mapping ice damage directly from satellite observations may not directly help improve the representation of these processes in ice-flow models.

Inland migration of near-surface crevasses in the Amundsen Sea Sector, West Antarctica

“…Our ice-penetrating radar observations of near-surface crevasses inland and across the grounding zone suggest that near-surface crevasses do not significantly change character as they advect onto the ice shelf and that many of these features are still confined to the near surface (Supplementary figures S6, S7). The depth of these features may explain the weak relationship found by Gerli et al (2023) between ice-shelf crevasses identified by Izeboud and Lhermitte (2023) and inferences of ice-shelf fluidity derived from contemporaneous surface velocity and ice thickness observations. Our results in connection with the findings of Gerli et al (2023) suggest that surface crevasses expressed in satellite remote sensing datasets (e.g.…”

“…The depth of these features may explain the weak relationship found by Gerli et al (2023) between ice-shelf crevasses identified by Izeboud and Lhermitte (2023) and inferences of ice-shelf fluidity derived from contemporaneous surface velocity and ice thickness observations. Our results in connection with the findings of Gerli et al (2023) suggest that surface crevasses expressed in satellite remote sensing datasets (e.g. Lai et al, 2020;Zhao et al, 2022;Surawy-Stepney et al, 2023a;Izeboud and Lhermitte, 2023) only weakly affect the bulk viscosity of ice shelves.…”