Melting and fragmentation laws from the evolution of two large Southern Ocean icebergs estimated from satellite data
Melting and fragmentation laws from the evolution of two large Southern Ocean icebergs estimated from satellite data
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DOI：
10.5194/tc-12-2267-2018
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发表时间：
2018-07-12
期刊：
影响因子：
5.2
通讯作者：
Gourves-Cousin, Rozenn
中科院分区：
文献类型：
--
作者：
Bouhier, Nicolas;Tournadre, Jean;Gourves-Cousin, Rozenn
通过对高度计数据和可见卫星图像的综合分析，对在开放水域漂流一年多的两座南大洋大冰山的厚度和面积的演变进行了估计。所观察到的厚度演变与冰山融化的预测，从两个常用的融化配方，使我们能够测试其有效性的大型冰山。基于流体动力学方法的第一种公式往往低估了基础熔化速率，而考虑热力学预算的第二种公式似乎与观察结果更一致。对于大冰山的腐烂来说，碎裂比融化更重要。尽管不成体系问题很重要，但有关这一问题的文献仍然很少。观测到的两座冰山的体积损失与环境参数之间的相关性突出了最有可能促进碎片化的因素。利用这些信息，建立了一个取决于海洋温度和冰山速度的整体碎裂模型。该模型是有效的再现所观察到的体积变化。使用高度计数据和可见光图像的大小分布的calved件估计，并发现与以前的结果和典型的脆性破碎过程是一致的。这些结果对于解释模式中大冰山对淡水通量的限制具有重要意义。
The evolution of the thickness and area of two large Southern Ocean icebergs that have drifted in open water for more than a year is estimated through the combined analysis of altimeter data and visible satellite images. The observed thickness evolution is compared with iceberg melting predictions from two commonly used melting formulations, allowing us to test their validity for large icebergs. The first formulation, based on a fluid dynamics approach, tends to underestimate basal melt rates, while the second formulation, which considers the thermodynamic budget, appears more consistent with observations. Fragmentation is more important than melting for the decay of large icebergs. Despite its importance, fragmentation remains poorly documented. The correlation between the observed volume loss of our two icebergs and environmental parameters highlights factors most likely to promote fragmentation. Using this information, a bulk model of fragmentation is established that depends on ocean temperature and iceberg velocity. The model is effective at reproducing observed volume variations. The size distribution of the calved pieces is estimated using both altimeter data and visible images and is found to be consistent with previous results and typical of brittle fragmentation processes. These results are valuable in accounting for the freshwater flux constrained by large icebergs in models.