极地海冰表面和底面形态相关性及其对冰厚反演的影响研究

In the polar regions, the continuous and large scale measurements of sea ice bottom morphology and thickness are still difficult. To solve this problem, in-situ measurement, mathematical modelling and optimal identification are combined to study the relationship between the morphologies of sea ice surface and bottom, and the influence of the obtained relationship on the retrieval of sea ice thickness is explored. Firstly, based on the data measured by the ship/helicopter-borne laser-electromagnetic induction system, the regional ice feature, carrier posture and measurement resolution are considered simultaneously to develop the optimal algorithm of data processing. Moreover, sea ice above and under water are distinguished. Secondly, the optimal model for the cutoff height/depth is established combining to the measured pressure ridge distribution, so that the ridge sail/keel and local roughness separated from the undulations of sea ice surface/bottom with the obtained cutoff height/depth agree well with the actual ice condition. And the relationship between the morphology parameters of local roughness/pressure ridges are estabished. Finally, the relationship between sea ice surface and bottom morphologies are analyzed, their influence on the bottom morphology and thickness of sea ice are assessed, and the retrieval models of sea ice bottom morphology and thickness are established, compatible with season, region and resolution, revealing the variations of sea ice bottom morphology and thickness with the ice surface morphology, and providing theoretical supports and experimental verification for the retrieval of sea ice thickness based on the surface morphology measured by satellite altimeters.

针对大范围、连续性极地海冰底面形态和冰厚难以有效观测的科学问题，结合项目组在现场观测、数学建模及优化辨识等方面的优势，本项目提出“极地海冰表面和底面形态相关性及其对冰厚反演的影响研究”这一科学命题。首先综合考虑冰区特征、载体航行姿态及观测分辨率等因素的影响，对船载/机载激光高度计和电磁感应系统所测的极地海冰形态和冰厚数据进行优化处理，有效识别海冰水上和水下部分。其次结合冰脊实测分布，建立关于切断高度/深度的优化模型，明确区分海冰表/底面起伏中的局部粗糙单元和脊帆/龙骨，建立海冰表面和底面局部粗糙单元、脊帆和龙骨各形态参数的相关关系。最后通过海冰表面和底面形态的相关性分析及其对底面形态和冰厚影响程度的评估，建立基于海冰表面形态的具有季节、区域和空间分辨率兼容性的底面形态和冰厚反演模型，揭示极地海冰底面形态和冰厚随表面形态的变化规律，为卫星测高等冰面高程数据反演冰厚提供新的理论指导和实验验证。

有机结合现场观测、数学建模、参数辨识及统计优化等多种研究方法，对极地海冰表面和底面形态相关性及其对冰厚反演的影响进行了研究。基于南北极海冰科学考察实测数据和实验室物理模拟数据，综合考虑冰区特征、载体航行姿态及观测分辨率、实验室模拟误差等因素的影响，对实测数据进行优化处理，实现了海冰水上和水下部分的有效识别。基于冰脊的实测空间概率分布，建立了关于冰脊切断高度/深度的优化辨识模型，构造了确定该参数的优化算法，明确区分了海冰表/底面起伏中的局部粗糙单元和脊帆/龙骨。结合地理位置、冰龄和生长环境对海冰表/底面的基本形态参数进行了统计分析，并找出了影响海冰表/底面形态的关键参数。建立了海冰表面和底面局部粗糙单元、脊帆和龙骨各形态参数的相关关系，并通过海冰表面和底面形态的相关性分析及其对底面形态和冰厚影响程度的评估，初步构建了基于海冰表面形态的底面形态和冰厚反演模型，可为利用冰面高程数据反演冰厚提供一定理论指导和实验验证。