Basal Channel Evolution on the Getz Ice Shelf, West Antarctica

• Published in: Journal of geophysical research. Earth surface Vol. 125; no. 9
• Main Authors: Chartrand, A. M., Howat, I. M.
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 01-09-2020
• Subjects: Altimetry; Antarctica; basal channels; Buttresses; Channels; cryosphere; Digital Elevation Models; Evolution; Flow velocity; Freeboard; Geophysical data; Ice; Ice shelves; Interferometric synthetic aperture radar; Land ice; Ocean models; Oceans; Radar; Sea level rise; Stability; Synthetic aperture radar interferometry; Temporal variability; Temporal variations; Variability; Antarctica
• ISSN: 2169-9003; 2169-9011
• DOI: 10.1029/2019JF005293

Ice shelves regulate the ice‐ocean boundary by buttressing the flux of grounded ice into the ocean and are vulnerable to basal melt, which can lead to ice‐shelf thinning and loss of buttressing. Localized, enhanced basal melt can form basal channels, which may impact ice‐shelf stability. Here we investigate the evolution of the Getz Ice Shelf Basal Channel (GISBC) in West Antarctica using a novel suite of geophysical data, including Reference Elevation Model of Antarctica (REMA) digital elevation models, ICESat‐1 and ‐2 altimetry, Operation IceBridge altimetry and radar, and InSAR‐derived ice flow velocities. We describe basal‐channel and ice‐shelf change in both Eulerian and Lagrangian frameworks and document changes in the channel's shape and its lateral motion and estimate basal melting. We find a high degree of spatial and temporal variability in GISBC evolution, with several locations of active basal incision. Incision occurs at rates of up to 22 m a−1 at the head of the channel, which is extending toward the grounding line at a rate of ~1 km a−1. Freeboard heights over areas of rapid basal incision are out of hydrostatic equilibrium. The GISBC is also migrating to the northwest, perpendicular to the northeasterly ice flow direction, at an average rate of 70–80 m a−1. The spatiotemporal variability of evolution of the GISBC motivates further characterization of basal channels and their impact on ice‐shelf stability, so that these effects may more readily be incorporated in ice‐ocean models predicting ice flow and sea‐level rise.
Key Points
The recently released Reference Elevation Model of Antarctica and ICESat‐2 data sets enable detailed observations of basal channel evolution
The Getz Ice Shelf Basal Channel evolves over annual‐decadal timescales as evidenced by observations from 2004–2019
The Getz Ice Shelf Basal Channel is growing in length, width, and depth at its head, and is migrating toward a shear margin at its tail