Sea ice characteristics at Ice Station Belgica sites Brussels, Patria and Fabra in october 2007, Bellinghausen Sea

Ice Station Belgica was commenced in late winter 2007 in the Bellingshausen Sea as part of Sea Ice Mass Balance in Antarctica (SIMBA), an IPY 2007 cruise on the research vessel N.B. Palmer. A primary objective was to build on the work of previous Antarctic drift station experiments to geophysically characterize sea ice in terms of thickness, surface and ice bottom morphology, and ultimately area-unitized mass. A 24 day drift station was established at approximately 70°S and 93°W in mixed first-year and multi-year ice with three geophysical study sites selected on a 5 km**2 floe. A comprehensive time series assessment of elevation-surveyed transects ranging from 100 m to 300 m in length included snow surface elevation, snow depth, electromagnetic (EM) profiling, and direct drilling for ice draft and ice freeboard. Additional work included a snow surface morphology characterization of a 100 m x 300 m area between the primary time series EM transects. Correlation of EM ice thicknesses with collocated drilled ice thickness yielded equations for the correction of EM underestimation of thick deformed ice, particularly at pressure ridges. Mean ice thickness from corrected EM was compared to isostatic ice thickness calculated from surface elevation, snow depth, ice freeboard and respective snow, slush, ice, and sea water densities. Results were consistent, with mean ice thicknesses for multi-year ice of 2.35 m, 2.34 m, and 2.41 m, with similar variance, for corrected EM, drilling, and buoyancy methods respectively. Additionally, a mean ice thickness of 2.31 m was calculated from ASPeCt observations of the ice field associated with the floe, using the method incorporating mean sail heights and fractional coverage of surface deformities or ridging. Temporal series assessment of ice freeboard indicated a slightly negative mean ice freeboard ( < 0.04 m), with clear evidence of new snow-ice formation from the freezing of slush. The three distinct snow and ice regions assessed on the Belgica floe had mean corrected EM ice thickness of 0.52 ± 0.04 m (± 1 std. deviation), 0.92 ± 0.17 m, and 2.35 ± 1.37 m, and mean snow depths of 0.08 ± 0.03 m, 0.36 ± 0.09 m, and 0.68 ± 0.31 m respectively. Each ice type represented a sizable fraction of the floe's total area (~ 20%, 40%, and 40% respectively from visual estimates) reflecting a complex dynamic and thermodynamic history of formation, as well as the difficulty in characterizing even a single floe by a single class or mean value for thickness and snow depth. Implications of these results are discussed with regards to the resolution of satellite-based altimetry and snow depth products and efforts to generate and validate satellite sea ice and snow thickness products.

贝尔吉卡冰站（Ice Station Belgica）于2007年晚冬在别林斯高晋海（Bellingshausen Sea）启动，作为南极海冰质量平衡（Sea Ice Mass Balance in Antarctica, SIMBA）项目的组成部分，属于依托研究船N.B.帕尔默号执行的2007年国际极地年（IPY）航次的一部分。其核心目标是继承此前南极漂移站实验的研究成果，从厚度、表面与冰底形态，乃至单位面积质量的维度，对海冰开展地球物理特征表征。研究团队在南纬70°、西经93°附近的一年冰（first-year ice）与多年冰（multi-year ice）混合区域建立了为期24天的漂移站，并在一块面积为5 km²的浮冰上选定3处地球物理研究测点。对长度介于100米至300米的高程测量断面开展全面的时间序列评估，测量内容包括雪面高程、积雪深度、电磁（electromagnetic, EM）剖面探测，以及直接钻探获取冰底吃水（ice draft）与冰面干舷（ice freeboard）数据。其余研究工作还包括在主时间序列EM断面之间的100 m × 300 m区域开展雪面形态特征表征。

通过将EM探测得到的冰厚与同位置钻探获取的冰厚进行相关性分析，得到了用于校正厚变形海冰（尤其冰压力脊（pressure ridges）区域）电磁探测低估现象的校正公式。将校正后的EM探测平均冰厚，与基于雪面高程、积雪深度、冰面干舷以及雪、雪泥（slush）、海冰与海水各自密度计算得到的均衡冰厚（isostatic ice thickness）进行对比。二者结果具有一致性：针对多年冰，校正EM法、钻探法与浮力法得到的平均冰厚分别为2.35 m、2.34 m与2.41 m，三者的方差水平相近。

此外，依托与该浮冰相关的海冰场的南极海冰过程与气候（Antarctic Sea Ice Processes and Climate, ASPeCt）观测数据，结合平均冰帆高度与表面变形/冰脊覆盖比例的计算方法，得到平均冰厚为2.31 m。对冰面干舷的时间序列评估结果显示，平均冰面干舷略低于0（< 0.04 m），并有明确证据表明存在由雪泥冻结形成的新生雪冰。

贝尔吉卡浮冰上评估的3处典型冰雪区域，其校正后EM探测平均冰厚分别为0.52 ± 0.04 m（±1倍标准差（standard deviation））、0.92 ± 0.17 m与2.35 ± 1.37 m，平均积雪深度则分别为0.08 ± 0.03 m、0.36 ± 0.09 m与0.68 ± 0.31 m。每类海冰均占浮冰总面积的可观比例（目视估算分别约为20%、40%与40%），这反映出海冰形成过程兼具复杂的动力与热力演化历史，也说明即便单块浮冰也难以通过单一分类或单一厚度、积雪深度均值完成特征表征。

本文还就卫星测高与积雪深度产品的分辨率，以及生成、验证卫星海冰与积雪厚度产品的相关工作，探讨了本研究结果的应用启示。