Calculating gravitationally self-consistent sea level changes driven by dynamic topography
Calculating gravitationally self-consistent sea level changes driven by dynamic topography
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DOI：
10.1093/gji/ggv371
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发表时间：
2015-12-01
影响因子：
2.8
通讯作者：
Mitrovica, J. X.
中科院分区：
文献类型：
--
作者：
Austermann, J.;Mitrovica, J. X.
我们提出了一种广义的形式主义，用于计算由动态地形、地幔对流引起的大地水准面扰动、冰块波动和变形地球上沉积物重新分布的综合影响驱动的重力自洽海平面变化。我们的数学处理保留了表面（冰加海洋）载荷和固体地球的质量。此外，它还精确考虑了海岸线迁移和相关的海洋载荷。新的形式主义避免了先前由动态地形驱动的海平面变化模型中采用的各种近似，包括“空气加载”动态地形的空间固定均衡放大准确地解释了海洋载荷效应的假设。虽然我们的方法对于任意复杂度的地球模型都有效，但我们给出了一组简单情况的数值结果，其中施加了动态地形模式，对表面质量载荷的响应假设地球结构仅随深度变化，并且始终保持均衡平衡。这些涉及流体洛夫数理论的计算表明，先前由动态地形驱动的海平面变化预测中的最大误差发生在海岸线迁移区域，因此发生在古代海平面的大多数地质标记附近。我们的结论是，在使用此类地质标记来估计古代冰量的任何努力中，对长期海平面变化进行重力自洽处理是必要的。
We present a generalized formalism for computing gravitationally self-consistent sea level changes driven by the combined effects of dynamic topography, geoid perturbations due to mantle convection, ice mass fluctuations and sediment redistribution on a deforming Earth. Our mathematical treatment conserves mass of the surface (ice plus ocean) load and the solid Earth. Moreover, it takes precise account of shoreline migration and the associated ocean loading. The new formalism avoids a variety of approximations adopted in previous models of sea level change driven by dynamic topography, including the assumption that a spatially fixed isostatic amplification of 'air-loaded' dynamic topography accurately accounts for ocean loading effects. While our approach is valid for Earth models of arbitrary complexity, we present numerical results for a set of simple cases in which a pattern of dynamic topography is imposed, the response to surface mass loading assumes that Earth structure varies only with depth and that isostatic equilibrium is maintained at all times. These calculations, involving fluid Love number theory, indicate that the largest errors in previous predictions of sea level change driven by dynamic topography occur in regions of shoreline migration, and thus in the vicinity of most geological markers of ancient sea level. We conclude that a gravitationally self-consistent treatment of long-term sea level change is necessary in any effort to use such geological markers to estimate ancient ice volumes.