Morphology of sea ice pressure ridges in the northwestern Weddell Sea in winter
Morphology of sea ice pressure ridges in the northwestern Weddell Sea in winter
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DOI：
10.1029/2011jc007800
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发表时间：
2012-06
影响因子：
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通讯作者：
Bing Tan;Zhijun Li;P. Lu;C. Haas;M. Nicolaus
中科院分区：
文献类型：
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作者：
Bing Tan;Zhijun Li;P. Lu;C. Haas;M. Nicolaus
2006年与德国R/V Polarstein进行的冬季韦德尔流出研究中的高度计。根据海脊高度分布与理论海脊高度和间距分布的最佳拟合度，首次确定了0.62 m的最佳截止高度，用于将压力脊与其他海冰表面起伏区分开来。结果表明，测得的垄高分布符合负指数分布，垄距分布符合对数正态分布。然后，基于脊化强度Ri(平均脊帆高与平均间距之比)，利用改进的k-Means聚类算法将所有剖面聚为三个区域：RI≤0.0 1、0.0 1 0.026(分别记为C1、C2和C3)。风帆高度的平均值(和标准差)分别为0.99(�0.07)m、1.12(�0.06)m和1.17(�0.04)m，平均间距(和标准差)分别为232(�240)m、54(�20)m和31(�5.6)m。这三个冰型与卫星雷达图像上识别的不同海冰区域非常吻合，其中C1对应于边缘冰带的破碎冰和在拉森波尼亚形成的水平冰。C2对应于研究区域中心动力作用形成的第一年和第二年的变形冰，C3对应于威德尔环流流出分支中的严重变形冰。我们的分析结果表明，平均脊高与频率之间的关系可以用对数函数很好地模拟，相关系数为0.8，但当单独考虑每个区域时，这种相关性较弱。在罗斯海测得的海脊高度和频率都比其他报道的要大。与南极其他地区的报道值相比，目前的脊线高度较大，但脊线频率和脊线强度小于最极端的脊线频率和脊线强度。同时，本研究区海脊冰的平均厚度明显大于罗斯海沿岸，说明形变和冰期对威德尔海西北部冰情的重要性。
altimeter during Winter Weddell Outflow Study with the German R/V Polarstern in 2006. An optimal cutoff height of 0.62 m, derived from the best fits between the measured and theoretical ridge height and spacing distributions, was first used to separate pressure ridges from other sea ice surface undulations. It was found that the measured ridge height distribution was well modeled by a negative exponential function, and the ridge spacing distribution by a lognormal function. Next, based on the ridging intensity Ri (the ratio of mean ridge sail height to mean spacing), all profiles were clustered into three regimes by an improved k-means clustering algorithm: Ri ≤ 0.01, 0.01 0.026 (denoted as C1 ,C 2, and C3 respectively). Mean (and standard deviation) of sail height was 0.99 (� 0.07) m in Regime C1, 1.12 (� 0.06) m in C2, and 1.17 (� 0.04) m in C3, respectively, while the mean spacings (and standard deviations) were 232 (� 240) m, 54 (� 20) m, and 31 (� 5.6) m. These three ice regimes coincided closely with distinct sea ice regions identified in a satellite radar image, where C1 corresponded to the broken ice in the marginal ice zone and level ice formed in the Larsen Polynya, C2 corresponded to the deformed first- and second-year ice formed by dynamic action in the center of the study region, and C3 corresponded to heavily deformed ice in the outflowing branch of the Weddell Gyre. The results of our analysis showed that the relationship between the mean ridge height and frequency was well modeled by a logarithmic function with a correlation coefficient of 0.8, although such correlation was weaker when considering each regime individually. The measured ridge height and frequency were both greater than those reported by others for the Ross Sea. Compared with reported values for other parts of the Antarctic, the present ridge heights were greater, but the ridge frequencies and ridging intensities were smaller than the most extreme of them. Meanwhile, average thickness of ridged ice in our study region was significantly larger than that of the Coastal Ross Sea showing the importance of deformation and ice age for ice conditions in the northwestern Weddell Sea.