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首页> 外文期刊>Journal of geodynamics >Regional geoid modeling in the area of subglacial Lake Vostok, Antarctica
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Regional geoid modeling in the area of subglacial Lake Vostok, Antarctica

机译：南极冰河沃斯托克湖地区的大地水准面模拟

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摘要

We present a geoid model for the area of Lake Vostok, Antarctica, from a combination of local airborne gravity, ice-surface and ice-thickness data and a lake bathymetry model. The topography data are used for residual terrain modeling (RTM) in a remove-restore approach together with GOCE satellite data. The quasigeoid is predicted by least-squares collocation (LSC) and subsequently converted to geoid heights. Special aspects of that method in presence of an ice sheet are discussed. It is well known that a body freely floating in water is in a state of hydrostatic equilibrium (HE). This usually applies, e.g., to ice shelves or sea ice. However, it has been shown that this is valid also for the ice sheet covering the subglacial Lake Vostok. Thus, we demonstrate the use of such a refined regional geoid model for glaciological and geophysical applications by means of the HE surface of that lake. The mean quadratic residual geoid signal (0.56m) w.r.t. the GOCE background model exceeds the residual variations of the estimated apparent lake level (ALL) (0.26 m) within the central part of the lake. An approach considering the actual geopotential at the ALL has been derived and subsequently applied. In this context, downward continuation of the potential field within the ice sheet as well as the latitudinal tilt of off-geoid equipotential surfaces are discussed. In view of the accuracy of the ice-thickness measurements that dominate the total error budget of the estimated ALL these effects are negligible. Thus, the HE surface of subglacial lakes may safely be described by a constant height bias in small-scale regional applications. However, field continuation is significant with respect to the formal uncertainty of the quasigeoid, which is at the level of 5 cm given that accurate airborne gravity data (±2 mGal) are available.
机译：我们结合当地的航空重力，冰面和冰厚数据以及湖测深模型，提出了南极沃斯托克湖地区的大地水准面模型。地形数据与GOCE卫星数据一起用于删除-恢复方法中的残余地形建模（RTM）。通过最小二乘搭配（LSC）预测拟类群，然后将其转换为大地水准面高度。讨论了在冰盖存在下该方法的特殊方面。众所周知，自由漂浮在水中的物体处于静水平衡（HE）状态。这通常适用于例如冰架或海冰。然而，已经表明，这对于覆盖冰川下的沃斯托克湖的冰盖也是有效的。因此，我们通过该湖的HE表面，证明了这种精细的区域大地水准面模型在冰川学和地球物理应用中的使用。平均二次残留大地水准面信号（0.56m）w.r.t. GOCE背景模型超出了湖中部估计的表观湖水位（ALL）（0.26 m）的残余变化。已经得出并考虑了在ALL处考虑实际地势的方法。在这种情况下，讨论了冰盖内势场的向下延续以及非对地等势面的纬向倾斜。考虑到冰厚测量值的准确性，这些测量值在估算的总误差预算中占主导地位，所有这些影响都可以忽略不计。因此，在小规模区域性应用中，冰川下湖泊的HE表面可以通过恒定的高度偏差安全地描述。但是，就准类星体的形式不确定性而言，场连续性很重要，鉴于可获得精确的空中重力数据（±2 mGal），准连续性在5 cm的水平上。

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