Ice shelf stress response to large iceberg calving

冰架应力对大型冰山崩解的反应

• 批准号: NE/R012334/1
• 负责人: Adam Booth
• 金额: $ 6.66万
• 依托单位: University of Leeds
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2017
• 资助国家: 英国
• 起止时间: 2017 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FR012334%2F1
• 关键词: Ice; shelf; stress; response; large

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, andiv) 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.

南极冰盖的冰损失被整个大陆大部分地区的浮冰架子所缓冲。冰架像天然大坝一样，限制了从南极进入南大洋的陆地冰的传递，因此在预测南极冰对海平面上升的贡献时，冰架的稳定性非常重要。在大型冰山产犊后的几年中，冰架可能会破坏稳定。例如，1995年1月，拉森B冰架（LBIS）在地区的冰山中镇定了1720平方公里，并逐渐退缩，直到2002年初的几周内倒塌。随着LBI的去除，其支流冰川被认为会加速并将更多的冰送入海洋。尽管货架倒塌的后果得到了充分的认识，但对产犊后从稳定到不稳定的冰架过渡涉及的过程却鲜为人知。迄今为止，我们几乎没有机会研究此类过程，因为大规模的冰山产犊很少见。因此，这项紧迫性提案试图通过在最近在Larsen C Ice架（LCIS）上进行产犊事件来动员一项研究来解决这个问题。 2017年7月12日，LCIS镇定了有史以来最大的冰山之一。该冰山被称为A68，面积为5800平方公里（占LCIS的12％），在裂谷繁殖3.5年后与架子分开。预测剩余的LCI在损失A68之后将如何发展是我们项目的关键动机，这是预测性数值建模，卫星遥感以及对LCIS的原位地球物理调查的集成运动。冰流的许多模拟突出了冰纹损害在确定LCI的未来稳定性中的重要作用：架子中现有的弱点（例如表面和基底裂缝）在新的扩展状态下倾向于打开。但是，冰架结构中的局部异质性可能会使这种反应复杂化，并且架子将反应和稳定的时间表也不清楚。为了解决这些歧义，我们的目标是捕获LCI的早期反应，以解决这些歧义，因此我们的紧迫性资金应用。我们的项目考虑了两个假设：1）LCIS上的压力增加将逐渐提高产犊速率，尤其是在架子已经被壁炉架破坏的地方。 2）LCI的响应稳定为架子的适应，但是对长期稳定性的准确预测需要对最早的响应的限制。我们的组装团队是4种关键方法的专家，并集成了测试我们的假设。 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, andiv) numerical modelling, to integrate所有数据并预测A68 Iceberg的产犊之前，通过和之后损害如何演变。Satellite分析和数值建模将在10月初开始该项目的启动时开始，并在最早的后勤机会中进行了现场部署（待在2017年11月的英国南极调查中进行确认，但可能在2017年11月进行。这项至关重要的初步评估将作为整个2018年进一步赠款申请的基础，其中包括部署一套全面的现场工具。最直接的好处将是对A68产犊事件的特定理解及其对剩余LCI的稳定性的影响，但我们还提高了对任何等效产犊过程所涉及的机制的理解。

项目成果

An updated seabed bathymetry beneath Larsen C Ice Shelf, Antarctic Peninsula

南极半岛拉森 C 冰架下更新的海底测深

• DOI: 10.5194/essd-12-887-2020
• 发表时间: 2020
• 期刊: Earth System Science Data
• 影响因子: 11.4
• 作者: Brisbourne A

An updated seabed bathymetry beneath Larsen C Ice Shelf, west Antarctic

南极西部拉森 C 冰架下方更新的海底测深

• DOI: 10.5194/essd-2019-205
• 发表时间: 2019
• 作者: Brisbourne A