气候变化领域集成服务门户(CCPortal): Diagnosing ice sheet grounding line stability from landform morphology

CCPortal

DOI	10.5194/tc-12-2707-2018
	Diagnosing ice sheet grounding line stability from landform morphology
	Simkins L.M.; Greenwood S.L.; Anderson J.B.
发表日期	2018
ISSN	19940416
卷号	12 期号:8
英文摘要	The 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. © Author(s) 2018.
学科领域	continental shelf; data set; depositional environment; grounding line; ice margin; ice sheet; ice shelf; iceberg calving; melting; moraine; morphotype; sea ice; sedimentation; stability analysis; vulnerability; Ross Sea; Southern Ocean
语种	英语
scopus关键词	continental shelf; data set; depositional environment; grounding line; ice margin; ice sheet; ice shelf; iceberg calving; melting; moraine; morphotype; sea ice; sedimentation; stability analysis; vulnerability; Ross Sea; Southern Ocean
来源期刊	Cryosphere
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/119082
作者单位	Department of Earth, Environmental, and Planetary Sciences, Rice University, Houston, TX 77005, United States; Department of Environmental Sciences, University of Virginia, Charlottesville, VA 22904, United States; Department of Geological Sciences, Stockholm University, Stockholm, 10691, Sweden
推荐引用方式 GB/T 7714	Simkins L.M.,Greenwood S.L.,Anderson J.B.. Diagnosing ice sheet grounding line stability from landform morphology[J],2018,12(8).
APA	Simkins L.M.,Greenwood S.L.,&Anderson J.B..(2018).Diagnosing ice sheet grounding line stability from landform morphology.Cryosphere,12(8).
MLA	Simkins L.M.,et al."Diagnosing ice sheet grounding line stability from landform morphology".Cryosphere 12.8(2018).