Persistent overcut regions dominate the terminus morphology of a rapidly melting tidewater glacier

Abstract Frontal ablation, the combination of submarine melting and iceberg calving, changes the geometry of a glacier's terminus, influencing glacier dynamics, the fate of upwelling plumes and the distribution of submarine meltwater input into the ocean. Directly observing frontal ablation and...

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Bibliographic Details
Published in:Annals of Glaciology
Main Authors: Abib, Nicole, Sutherland, David A., Amundson, Jason M., Duncan, Dan, Eidam, Emily F., Jackson, Rebecca H., Kienholz, Christian, Morlighem, Mathieu, Motyka, Roman J., Nash, Jonathan D., Ovall, Bridget, Pettit, Erin C.
Other Authors: Office of Polar Programs
Format: Article in Journal/Newspaper
Language:English
Published: Cambridge University Press (CUP) 2023
Subjects:
Annals of Glaciology
glacier
Tidewater
Alaska
Online Access:http://dx.doi.org/10.1017/aog.2023.38
https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0260305523000381
Description
Summary:Abstract Frontal ablation, the combination of submarine melting and iceberg calving, changes the geometry of a glacier's terminus, influencing glacier dynamics, the fate of upwelling plumes and the distribution of submarine meltwater input into the ocean. Directly observing frontal ablation and terminus morphology below the waterline is difficult, however, limiting our understanding of these coupled ice–ocean processes. To investigate the evolution of a tidewater glacier's submarine terminus, we combine 3-D multibeam point clouds of the subsurface ice face at LeConte Glacier, Alaska, with concurrent observations of environmental conditions during three field campaigns between 2016 and 2018. We observe terminus morphology that was predominately overcut (52% in August 2016, 63% in May 2017 and 74% in September 2018), accompanied by high multibeam sonar-derived melt rates (4.84 m d −1 in 2016, 1.13 m d −1 in 2017 and 1.85 m d −1 in 2018). We find that periods of high subglacial discharge lead to localized undercut discharge outlets, but adjacent to these outlets the terminus maintains significantly overcut geometry, with an ice ramp that protrudes 75 m into the fjord in 2017 and 125 m in 2018. Our data challenge the assumption that tidewater glacier termini are largely undercut during periods of high submarine melting.

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