(Table 1) Summary statistics of in situ sea-ice characteristics of Ice Station Belgica sites Fabra, Patria/Liège and Brussels in October 2007

Three ice type regimes at Ice Station Belgica (ISB), during the 2007 International Polar Year SIMBA (Sea Ice Mass Balance in Antarctica) expedition, were characterized and assessed for elevation, snow depth, ice freeboard and thickness. Analyses of the probability distribution functions showed great potential for satellite-based altimetry for estimating ice thickness. In question is the required altimeter sampling density for reasonably accurate estimation of snow surface elevation given inherent spatial averaging. This study assesses an effort to determine the number of laser altimeter 'hits' of the ISB floe, as a representative Antarctic floe of mixed first- and multi-year ice types, for the purpose of statistically recreating the in situ-determined ice-thickness and snow depth distribution based on the fractional coverage of each ice type. Estimates of the fractional coverage and spatial distribution of the ice types, referred to as ice 'towns', for the 5 km**2 floe were assessed by in situ mapping and photo-visual documentation. Simulated ICESat altimeter tracks, with spot size ~70 m and spacing ~170 m, sampled the floe's towns, generating a buoyancy-derived ice thickness distribution. 115 altimeter hits were required to statistically recreate the regional thickness mean and distribution for a three-town assemblage of mixed first- and multi-year ice, and 85 hits for a two-town assemblage of first-year ice only: equivalent to 19.5 and 14.5 km respectively of continuous altimeter track over a floe region of similar structure. Results have significant implications toward model development of sea-ice sampling performance of the ICESat laser altimeter record as well as maximizing sampling characteristics of satellite/airborne laser and radar altimetry missions for sea-ice thickness.

2007年国际极地年（International Polar Year）框架下的SIMBA（南极海冰质量平衡，Sea Ice Mass Balance in Antarctica）科考项目中，研究团队对贝尔吉卡冰站（Ice Station Belgica, ISB）的三种冰型分布开展了特征描述，并针对高程、积雪深度、冰面干舷与冰厚进行了评估。对概率分布函数的分析表明，星载测高技术在海冰厚度估算领域具备巨大应用潜力。本研究核心探讨的问题是：考虑到固有的空间平均效应，要实现积雪表面高程的合理精准估算，所需的测高仪采样密度应为多少。本研究针对代表南极混合一年冰与多年冰典型特征的ISB浮冰，开展了激光测高仪击中点（laser altimeter 'hits'）数量的评估工作，旨在基于各冰型的占比，通过统计方法还原原位实测得到的海冰厚度与积雪深度分布。针对这片5平方千米的浮冰，研究团队通过原位测绘与影像目视记录，对被称为“冰区斑块（ice 'towns'）”的各冰型占比与空间分布进行了估算。研究模拟了ICESat测高仪的飞行轨迹（光斑直径约70米，点间距约170米），对浮冰的各冰区斑块进行采样，由此生成基于浮力原理的海冰厚度分布。若要通过统计方法还原由三种冰型斑块组成的混合一年冰与多年冰区域的厚度均值与分布，需获取115个测高仪击中点；若仅针对由两种冰型斑块组成的纯一年冰区域，则仅需85个击中点——这分别等效于在结构相似的浮冰区域上，获取总长19.5千米与14.5千米的连续测高仪采样轨迹。本研究结果对于ICESat激光测高仪海冰采样性能的模型构建，以及优化星载/机载激光与雷达测高任务在海冰厚度探测中的采样特性，均具有重要参考价值。