| 夏季北极密集冰区范围确定及其时空变化研究 |
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| 引用本文： | 刘成龙,赵进平.夏季北极密集冰区范围确定及其时空变化研究[J].海洋学报,2013,35(4):36-46. |
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| 作者姓名： | 刘成龙 赵进平 |
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| 作者单位： | 中国海洋大学 海洋环境学院, 山东 青岛 266100 |
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| 基金项目： | 全球变化研究国家重大科学研究计划项目(2010CB951403);国家南北极环境综合考察专项 (CHINARE2012-04-04)。 |
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| 摘 要： | 研究夏季北极密集冰区的范围变化是了解北极海冰融化过程的重要手段。密集冰区与海冰边缘区之间没有明确的分界线, 海冰密集度在两者之间平滑过渡, 确定密集冰区范围就需确定一个密集度阈值。文中依据分辨率为6.25 km的AMSR-E遥感数据, 发现不同密集度阈值所围范围在密集冰区边缘处的减小存在由快变慢的过程, 同时与周围格点的密集度差异变化在该处最为显著, 对这两个特征进行统计分析, 获得的阈值同为89%, 具有明确的物理意义和合理性。以此为基础, 运用腐蚀算法剔除海冰边缘区, 同时结合连通域法排除小范围密集冰的影响, 进而确定密集冰区的范围。结果表明, 2002-2006年密集冰区覆盖范围较大, 年际变化较小, 2007年以后明显减小, 2010年与2011年相继出现最小值, 其中2011年的范围最小值仅为2006年的64%。密集冰区范围的变化不同于海冰覆盖范围, 是具有独立特性的海冰变化参数, 反映出高密集度海冰区域的变化特征。海冰的融化与海冰边缘区的变化是导致密集冰区范围发生变化的两个主要因素, 受动力学因素的影响, 海冰边缘区发生伸展或收缩, 发生密集冰区与海冰边缘区互相转化。本文提出了一种研究北极海冰变化的新思路, 密集冰区覆盖范围的减小表明北极中央区域高密集度海冰正持续减少。
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| 关 键 词： | 密集冰区 海冰边缘区 密集度阈值 腐蚀算法 连通域法 |
| 收稿时间： | 3/3/2013 12:00:00 AM |
| 修稿时间： | 2013/5/14 0:00:00 |
Pack ice extent and its spatiotemporal variation in summer Arctic |
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| LIU Chenglong and ZHAO Jinping.Pack ice extent and its spatiotemporal variation in summer Arctic[J].Acta Oceanologica Sinica (in Chinese),2013,35(4):36-46. |
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| Authors: | LIU Chenglong and ZHAO Jinping |
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| Institution: | College of Environmental Oceanography Ocean University of China, Qingdao 266100, China |
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| Abstract: | Variation of pack ice extent (PIE) in summer Arctic is important for understanding the sea-ice change in Arctic Ocean. As the ice concentration smoothly decreases from pack ice to marginal ice zone(MIZ), there is no definite boundary between them. Therefore a threshold of ice concentration, C0, is required to define a margin of the pack ice in order to study the spatiotemporal variation of pack ice coverage. Two characteristics of ice concentration variation were obtained using 6.25 km resolution data of AMSR-E. The pack ice areas decrease with higher thresholds of ice concentration, whereas the decreasing rate with ice concentration is not uniform. A value of ice concentration could be chosen as a threshold at which the decreasing rate shifts from faster to slower. Meanwhile, the differences of ice concentration with neighboring grids will have a biggest statistical change nearby the margin. The suggested thresholds by the two characteristics mentioned above are all 89%, indicating a well defined threshold with clear physical significance. Based on the threshold of ice concentration, an erosion algorithm is used to eliminate the MIZ and a connected domain algorithm is used to remove the small ice pieces out of the pack ice. The larger PIE appeared during 2002-2006 with little annual variation. Since 2007, PIE decreased obviously. The minimum PIE was renewed in 2010 and 2011, especially the PIE of 2011 is only 64% of 2006. The variation of PIE is quite different from the ice-coverage extent (PIE plus MIZ), being an relative independent parameter in reflecting the sea ice variation in the area with high ice concentration. Sea-ice melting and variability of MIZ are two main factors influence the PIE. MIZ could extend or shrink by dynamic factors, which will induce some ice blocks moving from or into pack ice, leading to an associated transition between PIE and MIZ. This paper provides a new insight about sea ice variation in the Arctic, and the decrease of PIE indicates the ongoing reduce of pack ice in central Arctic Ocean． |
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| Keywords: | pack ice marginal ice zone sea-ice concentration threshold erosion algorithm connected domain algorithm |
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