A full Stokes-flow thermo-mechanical model for firn and ice applied to the Gorshkov crater glacier, Kamchatka
A full Stokes-flow thermo-mechanical model for firn and ice applied to the Gorshkov crater glacier, Kamchatka
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DOI：
10.3189/172756407782282543
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发表时间：
2007-10
影响因子：
2.9
通讯作者：
T. Zwinger;R. Greve;O. Gagliardini;T. Shiraiwa;M. Lyly
中科院分区：
文献类型：
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作者：
T. Zwinger;R. Greve;O. Gagliardini;T. Shiraiwa;M. Lyly
摘要 堪察加乌什科夫斯基火山戈尔什科夫火山口冰川具有大纵横比和由局部增强且空间变化的地热热通量引起的基岩特殊热力学条件的特点。此外，该冰川的大部分由冰而不是纯冰组成，这改变了冰川的流变特性（例如粘度和可压缩性）。我们提出了一种新开发的、基于有限元 (FE) 建模软件 Elmer 的热力耦合三维流动模型，并将其应用于戈尔什科夫火山口冰川。通过假设稳态条件，模拟了当今的速度场、温度场、基底熔化速率和年龄分布。我们发现流速一般都很小（每年几十厘米）。水平和垂直速度的大小相当，这表明浅冰近似不适用。由于火山热通量在空间上的变化，冰川深层的热状况是寒冷的，而较浅的部分是温带的。 K2 钻孔测量的温度剖面和年龄层得到了很好的再现，剩余的差异可能归因于瞬态（非稳态）条件。 Firn 压缩性被认为是建模方法的关键要素。
Abstract The Gorshkov crater glacier at Ushkovsky volcano, Kamchatka, is characterized by a large aspect ratio and special thermodynamic conditions at the bedrock caused by a locally enhanced and spatially varying geothermal heat flux. Furthermore, large parts of this glacier consist of firn rather than pure ice, which alters the rheological properties (such as viscosity and compressibility) of the glacier. We present a newly developed, thermo-mechanically coupled, three-dimensional flow model based on the finite-element (FE) modeling software Elmer, and apply it to the Gorshkov crater glacier. By assuming steady-state conditions, the present-day velocity field, temperature field, basal melting rate and age distribution are simulated. We find that flow velocities are generally small (tens of centimeters per year). Horizontal and vertical velocities are of comparable magnitude, which shows that the shallow-ice approximation is not applicable. Owing to the spatially variable volcanic heat flux, the thermal regime at the ice base is cold in the deeper parts of the glacier and temperate in the shallower parts. The measured temperature profile and age horizons at the K2 borehole are reproduced quite well, and remaining discrepancies may be attributed to transient (non-steady-state) conditions. Firn compressibility is identified as a crucial element for the modeling approach.