The evolution of ridged ice fields
The evolution of ridged ice fields
复制标题
脊状冰原的演化
DOI：
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发表时间：
2003
期刊：
影响因子：
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通讯作者：
M. Lensu
中科院分区：
文献类型：
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作者：
M. Lensu
冰脊是由局部变形形成的拉长的冰盖特征。在波罗的海，海脊的可见部分，即船帆，通常高1-3米，而海脊的大部分体积都包含在5-15米深的水下龙骨中。在更大的尺度上，冰脊形成了脊状的冰原。冰脊和脊状冰场的建模对于动态冰漂移模型、冰航行船舶以及对海洋结构物施加的冰载荷的估计是重要的。山脊领域量化的山脊高度和山脊间距，这是山脊帆之间的距离。本文建立了一个控制垄间距分布的演化方程。通常的对数正态分布和指数分布模型的间距分布作为解决方案。该方程还解释了从波罗的海和喀拉海的冰面剖面数据分析中发现的几个统计特征。建立了空间分布连续场的守恒方程。这些可以包括在动态冰预报模型中。参数化连接的演变冰面积的减少和浓度和应变率的字段。由此得到了山脊碎石等效厚度的估计值，该值比以前估计的值大得多。参数化需要对山脊进行横截面建模。引入一种新的特征--脊簇来描述龙骨接触中的脊。发展了描述集群结构和集群发生的概念。间距方程是Kolmogorov-Feller方程的一个特殊形式，而Kolmogorov-Feller方程是控制不连续马尔可夫过程的基本方程。另一个具体的公式是冰厚分布演变的方程式。给出了不连续马氏过程的一般表示。它可用于构造冰形态量的演化方程。在本上下文中，它被用来制定替代的间距方程。这些备选方案中最适用的是脊帆数或线段上帆数的分布。
Ridges are elongated ice cover features created by local deformation. In the Baltic the visible part of the ridge, the sail, is typically 1-3 m high while the bulk of the ridge volume is contained to the 5-15 m deep subsurface keel. In larger scales ridging creates ridged ice fields. The modeling of ridges and ridged ice fields is important for dynamic ice drift models, for ice navigating ships, and for the estimation of ice loads exerted against offshore structures. Ridge fields are quantified in terms of ridge heights and ridge spacings which are distances between ridge sails. The present work formulates an equation governing the evolution of ridge spacing distribution. The usual lognormal and exponential distribution models for spacing distributions are obtained as solutions. The equation also explains several statistical features found in the analysis of ice surface profile data from the Baltic and from the Kara Sea. Conservation equations for continuum fields of spacing distributions are formulated. These can be included in dynamic ice forecast models. The parameterisation links the evolution to the decrease of ice area and to the fields of concentration and strain rate. An estimate for the equivalent thickness of ridge rubble is thereby obtained and is much larger than the values estimated previously. The parameterisation requires cross-sectional modelling of the ridges. A new type of feature, a ridge cluster, is introduced to describe ridges in keel contact. Concepts to describe cluster structure and cluster occurrence are developed. The spacing equation is a specific formulation of the Kolmogorov-Feller equation which is the basic equation governing discontinuous Markov processes. Another specific formulation is the equation governing the evolution of ice thickness distribution. A general presentation of discontinuous Markov processes is given. It can be used to construct evolution equations for ice morphological quantities. In the present context it is used to formulate alternatives to the spacing equation. The most applicable of these alternatives govern the distribution of ridge sail number, or the number of sails on line segments.