Through analysis of over 64,000 ridge profiles identified from moored upward-looking sonars, we identify a well-defined average shape of pressure ridge keels that is concave or cusped, not triangular as widely assumed in other literature. On the basis of this average shape, we put forward a new, dimensional-definition, of a pressure ridge cross-section that follows a negative exponential form and allows an average pressure ridge cross section to be constructed with knowledge or choice of a single parameter. The horizonal asymptote of the profile represents the draft of the “background” ice in which the ridge is embedded. The draft of this background ice scales with keel depth and is typically greater than can be accounted through thermodynamic growth, indicating that ridges tend to be embedded in fields of mechanically thickened rubble. Using a variational ridge model we simulated keel shapes for a range of ridge building conditions. The model results agree well with the observations and indicate the cusped shape of an average ridge profile arises from the varying angle of horizontal shear in the ice cover when ridges form. The modeling results also explain the elongated tail of the area draft distribution of the pack.

中文翻译：

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海冰脊龙骨的平均形状

通过对从系泊的仰视声纳中识别出的 64,000 多个脊剖面的分析，我们确定了一个明确定义的压力脊龙骨的平均形状，它是凹形或尖头，而不是其他文献中广泛假设的三角形。在这个平均形状的基础上，我们提出了一个新的维度定义, 压力脊横截面遵循负指数形式，并允许通过了解或选择单个参数来构建平均压力脊横截面。剖面的水平渐近线代表嵌入山脊的“背景”冰的吃水。这种背景冰的吃水与龙骨深度成比例，并且通常比通过热力学增长可以计算的要大，这表明山脊往往嵌入机械加厚的碎石场中。我们使用变分山脊模型模拟了一系列山脊建造条件下的龙骨形状。模型结果与观察结果非常吻合，并表明平均山脊轮廓的尖峰形状是由山脊形成时冰盖中水平剪切的不同角度引起的。