Preprints
https://doi.org/10.5194/tc-2023-63
https://doi.org/10.5194/tc-2023-63
10 May 2023
 | 10 May 2023
Status: this preprint is currently under review for the journal TC.

Measurement of Ice Shelf Rift Width with ICESat-2 Laser Altimetry: Automation, Validation, and the behavior of Halloween Crack, Brunt Ice Shelf, East Antarctica

Ashley Morris, Bradley P. Lipovsky, Catherine C. Walker, and Oliver J. Marsh

Abstract. Ice shelves influence the mass balance of the Antarctic Ice Sheet by restricting the flow of ice across the grounding zone. Their ability to restrict ice flow is sensitive to changes in their extent or thickness. Full thickness fractures, known as rifts, create tabular icebergs which reduce ice shelf extent. We present a method for measuring rift width using ICESat-2 laser altimetry, as part of a larger effort to detect, catalog and measure various characteristics of Antarctic rifts. We validate the results using optical satellite imagery and data from Global Navigation Satellite System (GNSS) receivers around "Halloween Crack" on Brunt Ice Shelf, East Antarctica. During the study period a further rift, "North Rift" formed and rapidly calved a ~1270 km2 iceberg. In response to this second rift, the opening of Halloween Crack approached stagnation before returning to opening at a reduced rate. We suggest the opening rate is controlled by the ice shelf geometry and degree of contact with a pinning point at McDonald Ice Rumples, and its influence on the large-scale ice flow field. We replicate the general pattern of opening using an inverse finite element model, and discuss the response of the ice shelf to the calving. We use historical satellite imagery and previously published ice-front positions to demonstrate the importance of McDonald Ice Rumples to the long-term calving and advance cycle of Brunt Ice Shelf.

Ashley Morris, Bradley P. Lipovsky, Catherine C. Walker, and Oliver J. Marsh

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on tc-2023-63', Anonymous Referee #1, 13 Jul 2023
  • RC2: 'Great observations of ice-shelf rifting!', William Colgan, 04 Aug 2023
Ashley Morris, Bradley P. Lipovsky, Catherine C. Walker, and Oliver J. Marsh

Data sets

Antarctic Rift Catalog: Rift measurement algorithm and associated scripts/notebooks Ashley Morris, Bradley P. Lipovsky, and Catherine C. Walker https://doi.org/10.5281/zenodo.7839138

Model code and software

"icepack" model runs Ashley Morris and Bradley P. Lipovsky https://doi.org/10.5281/zenodo.7796399

Ashley Morris, Bradley P. Lipovsky, Catherine C. Walker, and Oliver J. Marsh

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Short summary
Floating ice shelves hold back Antarctic ice flow, but they are thinning and retreating. To help predict future mass loss we need a better understanding of the behavior of the rifts from which icebergs detach. We automate rift width measurement using surface elevation data from the ICESat-2 laser altimetry satellite, and validate using satellite images and GPS receivers placed around the "Halloween Crack" on Brunt Ice Shelf. We find rift opening stagnated following calving from an adjacent rift.