Ice shelf stress response to large iceberg calving

GSTDTAP

项目编号	NE/R012334/1
	Ice shelf stress response to large iceberg calving
	Adam David Booth
主持机构	University of Leeds
项目开始年	2017
	2017-10-09
项目结束日期	2019-04-08
资助机构	UK-NERC
项目类别	Research Grant
国家	英国
语种	英语
英文摘要	Ice loss from the Antarctic ice sheet is buffered by the floating ice shelves that fringe much of the continent. Acting like natural dams, ice shelves restrict the delivery of terrestrial ice from Antarctica into the southern oceans, therefore the stability of ice shelves is highly important when predicting the contribution of Antarctic ice to sea-level rise. Ice shelves can destabilise in the years following the calving of large icebergs; for example, in January 1995, Larsen B Ice Shelf (LBIS) calved an iceberg 1720 sq.km in area, and progressively retreated until collapsing in a matter of weeks in early 2002; with the removal of LBIS, its tributary glaciers were seen to accelerate and discharge more ice into the ocean. While the consequences of shelf collapse are well-appreciated, the processes involved in the transition from stable to unstable ice shelves following calving are poorly understood. To date, we have had few opportunities to study such processes because large-scale iceberg calving is rare. This urgency proposal therefore seeks to address this issue, by mobilising a study in the aftermath of a recent calving event on Larsen C Ice Shelf (LCIS). On 12th July 2017, LCIS calved one of the largest icebergs ever recorded; termed A68, this iceberg has an area of 5800 sq.km (12% of LCIS) and separated from the shelf following 3.5 years of rift propagation. Predicting how the remaining LCIS will evolve following the loss of A68 is the key motivator for our project, which is an integrated campaign of predictive numerical modelling, satellite remote sensing and in situ geophysical survey on LCIS. Many simulations of ice flow highlight the important role of englacial damage in determining the future stability of LCIS: existing weaknesses (such as surface and basal crevasses) in the shelf would tend to open in the new extensional regime. However, local heterogeneities in the structure of the ice shelf may complicate this response, and the timescale on which the shelf will react and stabilise is also unclear. To resolve these ambiguities, it is our goal to capture the early-stage response of LCIS to resolve these ambiguities hence our application for urgency funding. Our project considers two hypotheses: 1) Increased stresses on LCIS will progressively increase calving rates, particularly where the shelf is already damaged by crevasses. 2) The response of LCIS stabilises as the shelf adapts, but accurate forecasts of long-term stability require constraint of the earliest responses. Our assembled team are experts in 4 key methods, integrated to test our hypotheses. We will use: i) satellite imagery, to measure stress evolution at the surface of the ice shelf, by mapping changes in crevasse patterns, ii) seismic surveys, to be deployed on LCIS, to measure variations in damage at depth within the shelf, iii) GPS sensors, also deployed on LCIS, to record short-term fluctuations in the motion of the shelf, and iv) numerical modelling, to integrate all data and predict how damage evolved before, through and after the calving of the A68 iceberg. Satellite analysis and numerical modelling will commence at the initiation of the project in early October, with field deployment taking place at the earliest logistical opportunity (to be confirmed with the British Antarctic Survey, but likely in November 2017). This vital initial appraisal will serve as the basis of further grant applications through 2018, which will include the deployment of a comprehensive suite of field instruments. Our project offers an initial description of the new stress-state for LCIS, providing a reference baseline for any future study. The most immediate benefits will be for the specific understanding of the A68 calving event, and its implications for the stability of the remaining LCIS, but we also improve the understanding of the mechanisms involved with any equivalent calving process.
来源学科分类	Natural Environment Research
文献类型	项目
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/86838
专题	环境与发展全球科技态势
推荐引用方式 GB/T 7714	Adam David Booth.Ice shelf stress response to large iceberg calving.2017.