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南极洲大部分地区边缘的浮冰架所缓冲。冰架就像天然大坝一样，限制了陆地冰从南极洲进入南大洋，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。冰架在大冰山崩解后的几年内可能会不稳定;例如，1995年1月，拉森B冰架（LBIS）在该地区崩解了一座冰山，并逐渐退缩，直到2002年初在几周内崩溃;随着LBIS的消失，其支流冰川被认为加速并将更多的冰排入海洋。sq.km虽然冰架崩塌的后果是很好的理解，从稳定的冰架过渡到不稳定的过程中所涉及的崩解了解甚少。迄今为止，我们很少有机会研究这种过程，因为大规模的冰山崩解是罕见的。因此，这一紧急提案旨在解决这一问题，在拉森C冰架（LCIS）最近的一次产犊事件之后开展一项研究。2017年7月12日，LCIS崩解了有史以来最大的冰山之一;被称为A68，这座冰山面积为5800（LCIS的12%），经过3.5年的裂谷传播后与大陆架分离。sq.km预测A68丧失后剩余的LCIS将如何演变是我们项目的关键动力，这是一个综合的预测数值模拟，卫星遥感和现场地球物理调查的LCIS活动。许多冰流的模拟突出了冰内破坏在确定LCIS未来稳定性方面的重要作用：现有的弱点（如表面和基底裂缝）在大陆架将倾向于在新的伸展制度中开放。然而，冰架结构的局部不均匀性可能会使这种反应复杂化，而且冰架反应和稳定的时间尺度也不清楚。为了解决这些模糊性，我们的目标是捕捉LCIS的早期响应，以解决这些模糊性，因此我们申请紧急funding.Our项目考虑两个假设：1）LCIS的压力增加将逐步增加产犊率，特别是在大陆架已经被裂缝破坏的情况下。2)LCIS的响应随着大陆架的适应而稳定，但长期稳定性的准确预测需要最早的响应的约束。我们组装的团队是4种关键方法的专家，整合以测试我们的假设。我们将用途：卫星图像，通过绘制裂缝模式的变化来测量冰架表面的应力演变，二）地震勘测，将部署在LCIS上，以测量冰架内深处的损害变化，三）全球定位系统传感器，也部署在LCIS上，以记录冰架运动的短期波动，以及四）数值建模，综合所有数据并预测A68冰山崩解之前、之中和之后损害如何演变，卫星分析和数值建模将在10月初项目启动时开始，并在后勤方面尽早进行实地部署（有待英国南极调查局确认，但可能在2017年11月）。这一至关重要的初步评估将作为2018年进一步拨款申请的基础，其中将包括部署一套全面的现场仪器。我们的项目为LCIS提供了新压力状态的初步描述，为未来的任何研究提供了参考基线。最直接的好处将是对A68产犊事件的具体理解，及其对剩余LCIS稳定性的影响，但我们也提高了对任何等效产犊过程所涉及机制的理解。

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