Model experiments on large tabular iceberg evolution: ablation and strain thinning
Model experiments on large tabular iceberg evolution: ablation and strain thinning
复制标题
大型平板冰山演化模型实验：消融和应变稀疏
作者：
D. Jansen;H. Sandhäger;W. Rack
摘要：南极板状冰山是冰海系统的重要活动组成部分。为了研究固有冰动力与冰山演化的相关性，我们建立了一个基于冰架流动和传热基本方程的数值模型，该模型受冰-海洋-大气系统环境参数的强迫。用等密度理想冰山进行的模型实验表明，对于厚度为250 m、温度为- 15°C的典型冰山，应变变薄速率约为1 m a - 1。对不同环境条件的敏感性研究证实了我们模型的可靠性。对A- 38b冰山演变的5年模拟显示，冰山厚度平均从220 m减少到106.3 m，其中95%是由基底融化引起的，1%是由表面融化引起的，4%是由应变变薄引起的。我们发现冰山的扩张速度减缓了75%左右，冰的温度受到相对温暖的基底层的逐渐侵蚀和最上层变暖的强烈影响。根据模型结果，基底融化是漂移过程中冰山几何形状变化的主要原因，而应变变薄只与基底融化低的寒冷地区有关。
Abstract Antarctic tabular icebergs are important active components of the ice–ocean system. To investigate the relevance of inherent ice dynamics to iceberg evolution, we developed a numerical model based on the fundamental equations of ice-shelf flow and heat transfer, forced by environmental parameters of the ice–ocean–atmosphere system. Model experiments with idealized icebergs of constant density show that the strain thinning rate for a typical iceberg with a thickness of 250 m and a temperature of −15°C is about 1 m a−1. Sensitivity studies for different scenarios of environmental conditions confirmed the reliability of our model. A 5 year simulation of the evolution of iceberg A-38B yielded a mean decrease in thickness from 220 m to 106.3 m, 95% of which was caused by basal melting, 1% by surface melting and 4% by strain thinning. We found iceberg spreading decelerating by about 75%, and ice temperatures being strongly affected by progressive erosion of the relatively warm basal layers and warming in the uppermost part. According to the model results, basal melting is the primary cause of change of iceberg geometry during drift, whereas strain thinning is only relevant in cold areas where basal melting is low.