北极冰边缘区海冰动力过程研究

For the marginal ice zone (MIZ), the contribution of the form drag to momentum exchange and the large variability in ice conditions are always not fully presented by the traditional sea ice dynamic models. To solve this problem, 1) considering the existence of shallow ocean mixed layer in the summer marginal ice zone, both laboratory experiments and numerical modeling are carried out, in which stratified flow is used to simulate the density structure of the upper ocean, to study the dynamic interactions between ice ridge keel and stratified flow, to setup the quantitative representation of the keel form drag coefficient with ridge geometry and stratified flow properties, to obtain the influence of ridge keel on the flow field and internal waves, and then to consummate the parameterization of ice-ocean drag coefficient; 2) digital photography equipments are installed on aircraft and shipboard to systemically observe the MIZ on the cruises during Arctic field investigations, automatic image processing algorithms are developed to analyze the sea ice images of the Arctic MIZ, and then obtain the spatial distributions of floe size, shape, ice thickness, concentration and ice ridge. Finally the sea ice dynamic model suitable for the MIZ is developed which takes into account the parameterization of drag coefficients, wave force and ice internal force. Moreover, based on in-situ ice conditions in the Arctic MIZ, calculations using the developed model are conducted to study the sea ice drift in the MIZ, and its variations with wind and current as well as ice morphology. The results will provide solid supports for the studies on climate change, Arctic shipping and industrial activities.

针对传统海冰动力学模型无法全面反映海冰边缘区内形拖曳力贡献以及冰情多变特点的问题，通过1）考虑夏季海冰边缘区海洋混合层深度较浅的实际情况，开展实验室物理模拟和数值模拟实验研究，以分层流体模拟上层海洋的密度层化，深入研究冰脊与分层流体的动力作用过程，建立冰脊形拖曳系数随冰脊形态和流体性质变化的定量表达，获得冰脊对冰下流场和内波生成的影响规律，从而完善冰-水拖曳系数参数化方案；2）在北极现场考察中，利用飞机和船舶上搭载的数码影像设备对走航经过的海冰边缘区进行系统观测，发展海冰图像的自动处理算法，获得北极海冰边缘区内浮冰尺寸、形状、厚度、密集度及冰脊的分布规律。最终在充分考虑拖曳系数参数化、波浪力和冰内应力基础上，发展适用于海冰边缘区的动力学模型；并基于现场观测浮冰、冰脊分布，利用模型计算研究北极海冰边缘区浮冰运动规律，以及随冰形态和风、流场的变化，为气候变化研究和北极航运工业活动提供有益支持。

通过参加中国北极科学考察，开展了基于图像的海冰现场观测，发展了海冰图像的处理技术，结合历史数据分析，获得北极海冰以及边缘区内浮冰的形态特征和分布规律。通过在实验室内开展的物理模拟实验研究，深入了理解冰脊与均匀流体以及分层流体的动力相互作用过程，建立冰脊形拖曳系数随冰脊形态和流体性质变化的定量表达，获得冰脊对冰下流场和分层流体界面上内波生成的影响规律。利用FLUNET开展的数值模拟实验研究，得到的结果较好的吻合了物理模拟实验结果，从而验证的数值模拟研究的可行性，在此基础上推广获得的水深无关结果为从实验室尺度到原形尺度的应用提供了支持。在此基础上，对海冰拖曳系数参数化方案进行了完善，并将其应用于自由漂流的海冰动力学模型，讨论了边缘区海冰运动随冰形态和风、流场变化的规律。通过参与课题研究工作，共培养6名硕士研究生，目前4人已获得硕士学位。另有博士后在站1名。共发表相关研究论文19篇，其中SCI检索10篇，EI检索1篇，各项研究成果均已达到了预期目标。