Evaluating the importance of footloose-type failure in ice island deterioration modeling

IF 3.8 2区 工程技术 Q1 ENGINEERING, CIVIL
Anna J. Crawford , Greg Crocker , Jesse Smith , Derek Mueller , Till J.W. Wagner
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Abstract

The drift and deterioration of large and tabular icebergs, also known as “ice islands” in the Arctic, are modeled for both operational (e.g., offshore risk mitigation) and research (e.g., oceanographic impact of melt water input) purposes. In this paper, we build a theoretical argument to show that the lateral deterioration of ice islands is controlled by the rate of sidewall notch growth at the waterline, with this growth leading to the development of underwater rams and buoyancy-induced calving via the ‘footloose’ mechanism. This dominance of footloose-type lateral deterioration allows for the majority of ice island deterioration to be simulated with only three oceanic variables: wave height, wave period, and sea-surface temperature. Information regarding the size and lineage of ice islands tracked in the Canadian Ice Island Drift, Deterioration and Detection (CI2D3) Database provides opportunity to assess our theoretical work, as the database serves as a validation dataset for simulations of ice island length and area change. When simulating the length reduction over time of ice islands tracked in the CI2D3 Database, the footloose model reduced the mean error over 80 d to +277 m, compared to −1545 and −1403 m with no-melt and thermal-melt models, respectively. We also demonstrate a new approach to simulating the areal deterioration of ice islands resulting from discrete footloose calving events. The approach utilizes two parameters: the length-to-width ratio of the ice island (r) and the width of a footloose calving event relative to the ice island's length (K). With r = 1.6 and K= 0.8, the mean error in modeled area was close to zero after 20 d of simulation. A comparison of stresses associated with footloose events from a 1D-beam model and those simulated with 3D finite-element modeling showed that the 1D and 3D simulations produce broadly similar results. This supports our approaches and parameter assignments for simulating ice island length and area reduction from footloose calving. These approaches can now be incorporated into ice island deterioration models. The benefit of this incorporation will be greatest for those interested in research of longer-term impacts of ice island deterioration on ocean properties given the greater improvements to model error over periods of time that are longer than those that usually concern offshore ice management operations.
评估冰岛劣化模型中 "松脚型 "故障的重要性
北极地区的大型冰山(也称为 "冰岛")的漂移和退化模型,既可用于操作(如减轻近海风险),也可用于研究(如融水输入对海洋学的影响)。在本文中,我们从理论上论证了冰岛的横向恶化受控于水线处侧壁缺口的增长速度,这种增长会导致水下冲撞的发展,并通过 "脚部松动 "机制由浮力引起的开裂。这种 "脚松动 "式横向劣化的主导作用使得大部分冰岛劣化的模拟只需三个海洋变量:波高、波周期和海面温度。加拿大冰岛漂移、退化和探测(CI2D3)数据库中跟踪的冰岛大小和世系信息为评估我们的理论工作提供了机会,因为该数据库是模拟冰岛长度和面积变化的验证数据集。在模拟 CI2D3 数据库中跟踪到的冰岛长度随时间变化的情况时,松脚模型将 80 天内的平均误差减小到+277 米,而无融化模型和热融化模型的平均误差分别为-1545 米和-1403 米。我们还展示了一种新的方法,用于模拟离散浮足压冰事件导致的冰岛面积退化。该方法利用了两个参数:冰岛的长宽比(r)和相对于冰岛长度的塌陷宽度(K)。当 r=1.6 和 K=0.8 时,模拟 20 d 后,建模面积的平均误差接近于零。对一维梁模型和三维有限元模型模拟的松脚事件相关应力进行比较后发现,一维和三维模拟的结果大体相似。这支持了我们模拟冰岛长度和面积减少的方法和参数分配。现在可以将这些方法纳入冰岛退化模型。对于那些有兴趣研究冰岛退化对海洋特性的长期影响的人来说,这种方法的好处是最大的,因为在比通常涉及近海冰管理作业的时间更长的时期内,模型误差会有更大的改善。
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来源期刊
Cold Regions Science and Technology
Cold Regions Science and Technology 工程技术-地球科学综合
CiteScore
7.40
自引率
12.20%
发文量
209
审稿时长
4.9 months
期刊介绍: Cold Regions Science and Technology is an international journal dealing with the science and technical problems of cold environments in both the polar regions and more temperate locations. It includes fundamental aspects of cryospheric sciences which have applications for cold regions problems as well as engineering topics which relate to the cryosphere. Emphasis is given to applied science with broad coverage of the physical and mechanical aspects of ice (including glaciers and sea ice), snow and snow avalanches, ice-water systems, ice-bonded soils and permafrost. Relevant aspects of Earth science, materials science, offshore and river ice engineering are also of primary interest. These include icing of ships and structures as well as trafficability in cold environments. Technological advances for cold regions in research, development, and engineering practice are relevant to the journal. Theoretical papers must include a detailed discussion of the potential application of the theory to address cold regions problems. The journal serves a wide range of specialists, providing a medium for interdisciplinary communication and a convenient source of reference.
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