Evolution of basal channels, ice fracture, and surface meltwater, and implications for the stability of the Roi Baudouin Ice Shelf

Channelised basal melt has been hypothesised to reduce the structural integrity of ice shelves as a result of localised ice-shelf thinning, which induces spatially heterogeneous regions of intensified flexural stresses that encourage fracture initiation and possible subsequent calving. Further to this, the formation of surface rivers within the hydrostatic reflections of basal channels has been observed to increase the vulnerability of ice shelves to hydrofracture and/or estuarine weakening. Therefore, through these mechanisms, basal channels are considered to have the potential to precondition ice shelves to instability. The Roi Baudouin ice shelf (RBIS), located within the East Antarctic Ice Sheet, is considered to be a relatively stable ice shelf over decadal to millennial timescales and has a high proportion of actively buttressing ice. Although previous research has widely studied the developed network of basal channels within its western region, no study, to date, has examined changes in the locations and morphologies of basal channels over an extended period of time, nor the potential vulnerability of the RBIS to instability. Therefore, this study seeks to consider, for the first time, the changing patterns over time of basal channel locations and morphologies, and hence the current and future vulnerability of the RBIS to basal channel-induced instability. This study uses Landsat imagery and repeat ICESat laser altimetry measurements alongside other remotely-sensed datasets of surface meltwater, damage, and strain, to carry out a full ice-shelf-wide contemporary assessment of basal channel distribution and geomorphology across the RBIS over a 20 year study period (2002 - 2021). It aims to constrain potential relationships between basal channels, surface meltwater, fracture development, and thus possible calving. Significantly, the findings of this research document the formation, propagation, and advection of two basal channel associated fractures which culminated in a hitherto unreported ~948 km2 calving event from the frontal margin of the western region sometime between January and November 2021. It therefore presents the first evidence for basal channel-induced structural weakening of the RBIS, and provides further supporting evidence for the potential preconditioning of the RBIS to instability through shear margin weakening. Qualitative interpretation of surface melt and channel distributions implied little current risk for potential surface-river driven ice-shelf instability, however observations of subsurface lakes within the western region demands further research of the potential influence of englacial storage on the future vulnerability of the RBIS to destabilisation. Tracking of channel migration over the 2002 to 2021 period revealed evidence for ongoing, active channelised melt, and the recognition of two previously unidentified subglacially-sourced basal ‘mega channels’ within the central region implies that processes of subglacially-driven channelised basal melt at the base of the RBIS are occurring at greater scales than previously thought. These findings motivate future research across other ice shelves, particularly those with high proportions of buttressing ice, as channelised basal melt may have the potential to drive ice-shelf dynamic mass loss and ice-shelf destabilisation.

Level dc:type.qualificationlevel

Masters

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2023

Author dc:creator

• Jackson, Phoebe

Advisor dc:contributor.advisor

• Willis, Ian

Licence

• http://purl.org/NET/rdflicense/allrightsreserved

Language dc:language

eng

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.115389

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/379226