Diagnosing ice sheet grounding line stability from landform morphology

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dc.citation.firstpage2707en_US
dc.citation.journalTitleThe Cryosphereen_US
dc.citation.lastpage2726en_US
dc.citation.volumeNumber12en_US
dc.contributor.authorSimkins, Lauren M.en_US
dc.contributor.authorGreenwood, Sarah L.en_US
dc.contributor.authorAnderson, John B.en_US
dc.date.accessioned2018-11-09T15:00:04Zen_US
dc.date.available2018-11-09T15:00:04Zen_US
dc.date.issued2018en_US
dc.description.abstractThe resilience of a marine-based ice sheet is strongly governed by the stability of its grounding lines, which are in turn sensitive to ocean-induced melting, calving, and flotation of the ice margin. Since the grounding line is also a sedimentary environment, the constructional landforms that are built here may reflect elements of the processes governing this dynamic and potentially vulnerable environment. Here we analyse a large dataset (n=6275) of grounding line landforms mapped on the western Ross Sea continental shelf from high-resolution geophysical data. The population is divided into two distinct morphotypes by their morphological properties: recessional moraines (consistently narrow, closely spaced, low amplitude, symmetric, and straight) and grounding zone wedges (broad, widely spaced, higher amplitude, asymmetric, sinuous, and highly variable). Landform morphotypes cluster with alike forms that transition abruptly between morphotypes both spatially and within a retreat sequence. Their form and distribution are largely independent of water depth, bed slope, and position relative to glacial troughs. Similarly, we find no conclusive evidence for morphology being determined by the presence or absence of an ice shelf. Instead, grounding zone wedge construction is favoured by a higher sediment flux and a longer-held grounding position. We propose two endmember modes of grounding line retreat: (1) an irregular mode, characterised by grounding zone wedges with longer standstills and accompanied by larger-magnitude retreat events, and (2) a steady mode, characterised by moraine sequences that instead represent more frequent but smaller-magnitude retreat events. We suggest that while sediment accumulation and progradation may prolong the stability of a grounding line position, progressive development of sinuosity in the grounding line due to spatially variable sediment delivery likely destabilises the grounding position by enhanced ablation, triggering large-magnitude retreat events. Here, the concept of “stability” is multifaceted and paradoxical, and neither mode can be characterised as marking fast or slow retreat. Diagnosing grounding line stability based on landform products should be considered for a wider geographic range, yet this large dataset of landforms prompts the need to better understand the sensitivity of marine-based grounding lines to processes and feedbacks governing retreat and what stability means in the context of future grounding line behaviour.en_US
dc.identifier.citationSimkins, Lauren M., Greenwood, Sarah L. and Anderson, John B.. "Diagnosing ice sheet grounding line stability from landform morphology." <i>The Cryosphere,</i> 12, (2018) Copernicus Publications: 2707-2726. https://doi.org/10.5194/tc-12-2707-2018.en_US
dc.identifier.digitaltc-12-2707-2018en_US
dc.identifier.doihttps://doi.org/10.5194/tc-12-2707-2018en_US
dc.identifier.urihttps://hdl.handle.net/1911/103315en_US
dc.language.isoengen_US
dc.publisherCopernicus Publicationsen_US
dc.rightsThis work is distributed under the Creative Commons Attribution 4.0 License.en_US
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/en_US
dc.titleDiagnosing ice sheet grounding line stability from landform morphologyen_US
dc.typeJournal articleen_US
dc.type.dcmiTexten_US
dc.type.publicationpublisher versionen_US
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