南极海冰导温系数与孔隙率关系初探

PRELIMINARY RESULTS ON RELATIONSHIP BETWEEN THERMAL DIFFUSIVITY AND POROSITY OF SEA ICE IN THE ANTARCTIC

利用南极中山站附近固定冰不同季节的温度垂直廓线,冰芯盐度、密度数据,基于Cox等发展的冰内孔隙率计算方法,获得冰内孔隙率的垂直廓线。再通过建立分布参数系统最优控制模型,优化辨识在无热源条件下冰内温度垂直廓线对应的海冰导温系数。通过比较7种冰导温系数同孔隙率的关系,选择出海冰导温系数和孔隙率的最优关系式。用该关系式对同一地点不同年份的海冰进行温度垂直廓线计算,比较辨识的导温系数同孔隙率的关系相对于前人理想海冰模型中的导热系数、比热等公式计算对应条件的海冰垂直温度廓线的优势。两种计算结果说明,辨识得到的关系所引起的偏差在趋势和量级上同理想模式计算的结果相同,但辨识得到的关系更简洁,且更具有物理背景。

Used sea-ice temperature, salinity and density the Cox and Weeks formula to calculate porosity in data from Chinese Antarctic Expedition and ice, the vertical profile of porosity in ice is calculated. Then the vertical profile of sea-ice thermal diffusivity is obtained by establishing an optimal control model about distributed parameter system. According to seven assumed relations of sea-ice thermal diffusion and porosity, the best relation between the diffusion and porosity is identified. In order to illuminate the reliability of the expression identified, the simulation is al- so done correspondingly by employing sea-ice specific heat, thermal conductivity empirical for- mulae in the ideal model and field measured data from the winter of 2005 which performed in the same site, not same winter. The simulation results show the two relationships between Ant- arctic sea-ice thermal diffusivity and porosity are reasonable and can describe the variation of thermal diffusivity with porosity well, but the new one from inverse method is more clear and has the physical background. Key words sea ice, porosity, optimal identification, numerical simulations, Antarctica.