Complex spatial feedbacks of tephra redistribution, ice melt and surface roughness modulate ablation on tephra covered glaciers
Complex spatial feedbacks of tephra redistribution, ice melt and surface roughness modulate ablation on tephra covered glaciers
复制标题
火山灰重新分布、冰融化和表面粗糙度的复杂空间反馈调节火山灰覆盖冰川的消融
DOI：
10.1002/esp.3352
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发表时间：
2013
影响因子：
3.3
通讯作者：
B. Jacobs
中科院分区：
文献类型：
--
作者：
J. Nield;R. Chiverrell;S. Darby;J. Leyland;L. H. Vircavs;B. Jacobs
2011年Grímsvötn火山喷发到Svínafellsjökull的火山沉降物，冰岛，形成了一种冰灰景观，这种景观很少被研究，但在冰川火山地区很常见。我们使用地面激光扫描（TLS）在高空间分辨率下测量冰表面地形和吸收，确认在厚（绝缘）和薄（降低反照率）的火山灰沉积下，消融率分别降低或增加。对TLS数据的傅里叶变换分析发现，空气动力学粗糙度增加了三倍，这是由于较大（>·0.2 m）的表面特征增加所致。此外，TLS测量结果还揭示了融水对火山灰再分配的重要性，它可以改变粗糙度和火山灰斑块，从而使这些空间灰冰反馈的净效应可以降低高达59%的消融率。因此，这些先前未记载的反馈对消融速率的调节作用是显著的，如果要正确预测火山灰覆盖的冰川物质平衡，就必须正确地将其参数化。版权所有©2012 John Wiley & Sons， Ltd。
Tephra fallout from the 2011 Grímsvötn eruption onto Svínafellsjökull, Iceland, created an ice‐ash landscape of a type that is rarely studied but is nevertheless common in glacio‐volcanic regions. We used terrestrial laser scanning (TLS) to measure ice surface topography and absorption at high spatial resolution, confirming ablation rates either reduce or increase under thick (insulating) and thin (reduced albedo) ash deposits, respectively. Fourier transform analysis of the TLS data identified that a three‐fold increase in aerodynamic roughness was attributable to an increase in larger (> 0·2 m) surface features. Moreover, TLS measurements revealed the importance of ash redistribution by meltwater in generating differential melting which modifies roughness and ash patchiness, such that the net effect of these spatial ash–ice feedbacks was to reduce ablation rates by up to 59%. The modulating effects of these previously undocumented feedbacks on ablation rates are, therefore, significant and must be correctly parameterized if ash‐covered glacier mass balances are to be predicted correctly. Copyright © 2012 John Wiley & Sons, Ltd.