New 3D bathymetry and sediment distribution in Lake Vostok: Implication for pre-glacial origin and numerical modeling of the internal processes within the lake
New 3D bathymetry and sediment distribution in Lake Vostok: Implication for pre-glacial origin and numerical modeling of the internal processes within the lake
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DOI：
10.1016/j.epsl.2008.09.012
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发表时间：
2008-11
影响因子：
5.3
通讯作者：
I. Filina;D. Blankenship;M. Thoma;V. Lukin;V. N. Masolov;Mrinal K. Sen
中科院分区：
文献类型：
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作者：
I. Filina;D. Blankenship;M. Thoma;V. Lukin;V. N. Masolov;Mrinal K. Sen
通过对东南极洲沃斯托克湖冰下水和松散沉积物的航空重力资料反演，得到了该湖水和松散沉积物的新分布。为主岩开发了一个模型，其密度为2550 kg/m3，这是从先前的2D建模推断的。我们的三维测深模型的沃斯托克湖对应地震数据（RMS为125米）比以前的两个模型基于相同的重力数据集。重力模型和地震测量之间的水和沉积物厚度的良好匹配证实了关于沃斯托克湖的两个主要事实：（1）湖泊由沉积岩组成，（2）湖底覆盖着一层松散的沉积物，南部盆地不超过300米，北方盆地厚达400米。我们新的水深测量模型表明，湖的中部和北方的水厚度要浅得多（最多是以前估计的两倍），而南部盆地的水层要厚得多。在湖泊的内部过程的数值模拟揭示了我们的新的测深模型的基础质量平衡的相关性。在较浅的北方盆地中观察到运输的显著减少，以及湍流动能减少33%。然而，与以前的模型相比，在计算的冻结和熔化区的分布中只观察到微小的差异。对六种可能机制的沉积速率进行了估计。可能的沉积机制有：（1）河流和冰缘，即在形成大型冰下湖之前就活跃的沉积机制;（2）覆盖冰盖造成的沉积，包括冰的融化，以及覆盖冰的推土作用;（3）冰下水流产生的悬浮沉积物，包括冰下周期性喷发造成的沉积物。对这些机制的估计表明，所观察到的厚度的未固结沉积物与冰川形成前存在的湖泊最为一致。
A new distribution of water and unconsolidated sediments in subglacial Lake Vostok, East Antarctica was developed via inversion of airborne gravity data constrained by 60 seismic soundings. A model was developed for host rock with a density of 2550 kg/m3that was inferred from prior 2D modeling. Our 3D bathymetry model of Lake Vostok corresponds better with seismic data (RMS of 125 m) than two previous models based on the same gravity dataset. The good match in both water and sediment thicknesses between the gravity model and seismic measurements confirms two major facts about Lake Vostok: (1) the lake is hosted by sedimentary rocks, and (2) the bottom of the lake is covered with a layer of unconsolidated sediments that does not exceed 300 m in the southern basin and thickens almost to 400 m in the northern basin. Our new bathymetry model suggests much shallower water thicknesses (up to twice the previous estimates) in the middle and northern parts of the lake, while the water layer is thicker in the southern basin. Numerical modeling of the internal processes in the lake reveals the relevance of our new bathymetry model to the basal mass balance. A significant decrease in transport is observed in the shallower northern basin, as well as a decrease of 33% in the turbulent kinetic energy. However, only minor differences were observed in the distribution of the calculated freezing and melting zones compared to previous models. Estimates for the sedimentation rates for six possible mechanisms were made. Possible sedimentation mechanisms are: (1) fluvial and periglacial, i.e. those that are active prior to the establishment of a large subglacial lake; (2) deposition due to overlying ice sheet, including melting out of the ice, as well as bulldozering by the overriding ice; and (3) suspended sediments from subglacial water flow including those deposited by periodical subglacial outbursts. The estimates for these mechanisms show that unconsolidated sediments of the observed thickness are most consistent with a lake that existed before glaciation.