Physical and optical characteristics of heavily melted “rotten” Arctic sea ice
Physical and optical characteristics of heavily melted “rotten” Arctic sea ice
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DOI：
10.5194/tc-13-775-2019
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发表时间：
2018-07
期刊：
影响因子：
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通讯作者：
C. Frantz;B. Light;S. M. Farley;S. Carpenter;R. Lieb-Lappen;Z. Courville;M. Orellana;K. Junge
中科院分区：
文献类型：
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作者：
C. Frantz;B. Light;S. M. Farley;S. Carpenter;R. Lieb-Lappen;Z. Courville;M. Orellana;K. Junge
抽象的。在融化季节，对严重融化的“腐烂”北极海冰的特性进行了现场调查，对阿拉斯加乌特恰维克（以前的巴罗）海岸的岸冰和流冰进行了实地调查。虽然没有正式的标准来判断冰何时腐烂，但这项研究的目的是在冰的结构和光学特性充分超出夏季高峰时对融化的冰进行采样。 2015 年 5 月和 6 月记录了近岸冰的物理（温度、盐度、密度、微观结构）和光学（光散射）特性的基线数据。2015 年和 2017 年 7 月，小船被用来接近乌特恰维克约 32 公里范围内的漂流腐冰。测量结果表明，随着冰温升高（−8 至 0 ∘C）、冰盐度降低（10 至 0 ppt）和堆积密度降低（0.9 至 0.6 g cm−3），孔隙空间增加。在实验室中通过薄片显微摄影和 X 射线微型计算机断层扫描来表征孔隙空间的变化。这些分析产生了平均盐水包裹体数密度（从 32 减少到 0.01 mm−3）、平均孔径（从 80 µm 增加到 3 mm）、总孔隙率（从 0 % 增加到 > 45 %）和结构各向异性（可变，值通常小于 0.7）的变化。此外，随着冰融化的进行，冰的光散射系数从大约 0.06 增加到 > 0.35 cm−1。总之，这些发现表明，北极海冰在融化季节结束时的特性与经常研究的夏季冰的特性显着不同。如果这种腐冰在融化季节较长的温暖北极变得更加普遍，这可能会对海洋表面的液体和热量交换产生影响。
Abstract. Field investigations of the properties of heavily melted “rotten” Arctic sea ice were carried out on shorefast and drifting ice off the coast of Utqiaġvik (formerly Barrow), Alaska, during the melt season. While no formal criteria exist to qualify when ice becomes rotten, the objective of this study was to sample melting ice at the point at which its structural and optical properties are sufficiently advanced beyond the peak of the summer season. Baseline data on the physical (temperature, salinity, density, microstructure) and optical (light scattering) properties of shorefast ice were recorded in May and June 2015. In July of both 2015 and 2017, small boats were used to access drifting rotten ice within ∼32 km of Utqiaġvik. Measurements showed that pore space increased as ice temperature increased (−8 to 0 ∘C), ice salinity decreased (10 to 0 ppt), and bulk density decreased (0.9 to 0.6 g cm−3). Changes in pore space were characterized with thin-section microphotography and X-ray micro-computed tomography in the laboratory. These analyses yielded changes in average brine inclusion number density (which decreased from 32 to 0.01 mm−3), mean pore size (which increased from 80 µm to 3 mm), and total porosity (increased from 0 % to > 45 %) and structural anisotropy (variable, with values of generally less than 0.7). Additionally, light-scattering coefficients of the ice increased from approximately 0.06 to > 0.35 cm−1 as the ice melt progressed. Together, these findings indicate that the properties of Arctic sea ice at the end of melt season are significantly distinct from those of often-studied summertime ice. If such rotten ice were to become more prevalent in a warmer Arctic with longer melt seasons, this could have implications for the exchange of fluid and heat at the ocean surface.