Arctic sea ice albedo: Spectral composition, spatial heterogeneity, and temporal evolution observed during the MOSAiC drift
Arctic sea ice albedo: Spectral composition, spatial heterogeneity, and temporal evolution observed during the MOSAiC drift
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DOI：
10.1525/elementa.2021.000103
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发表时间：
2022-08-04
影响因子：
3.9
通讯作者：
Bailey, David A.
中科院分区：
文献类型：
--
作者：
Light, Bonnie;Smith, Madison M.;Bailey, David A.
北极海冰表面反照率的大小、光谱组成和变化是理解和数值模拟地球短波能量收支的关键。在北极气候研究多学科漂流观测站 (MOSAiC) 考察期间，冰上观察者沿着整个阳光照射季节（2020 年 4 月至 9 月）的各个测量线对北极海冰的光谱和宽带反照率进行了空间和时间采样。 MOSAiC 年反照率的季节性演变是根据每条线的空间平均宽带反照率值构建的。特定位置被确定为代表各个冰面类型，包括积累的干雪、融化的雪、裸露和融化的冰、融化和重新冻结的积冰以及充满沉积物的冰。 MOSAiC 期间记录的总反照率的区域平均季节性进展与 22 年前北冰洋表面热量收支 (SHEBA) 探险期间多年海冰记录的数据非常相似。根据这些和其他先前的实地工作，相对较厚、无雪、融化的海冰的光谱反照率显示出不同位置、十年和冰类型的不变性。特别是，无雪、融化的季节性冰的反照率与无雪、融化的第二年冰的反照率没有区别，这表明夏季海冰上形成的高度散射的表面层是坚固且稳定的。相比之下，观察到积冰的反照率在可见光波长下变化很大。在融化和冻结开始、融化池的形成和加深以及充满沉积物的冰的融化演化过程中，记录了反照率的显着时间变化。虽然模型模拟显示与观察到的季节性反照率进展相当一致，但差异表明需要改进积冰和薄冰融化的反照率的模拟方式。
The magnitude, spectral composition, and variability of the Arctic sea ice surface albedo are key to understanding and numerically simulating Earth's shortwave energy budget. Spectral and broadband albedos of Arctic sea ice were spatially and temporally sampled by on-ice observers along individual survey lines throughout the sunlit season (April-September, 2020) during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition. The seasonal evolution of albedo for the MOSAiC year was constructed from spatially averaged broadband albedo values for each line. Specific locations were identified as representative of individual ice surface types, including accumulated dry snow, melting snow, bare and melting ice, melting and refreezing ponded ice, and sediment-laden ice. The area-averaged seasonal progression of total albedo recorded during MOSAiC showed remarkable similarity to that recorded 22 years prior on multiyear sea ice during the Surface Heat Budget of the Arctic Ocean (SHEBA) expedition. In accord with these and other previous field efforts, the spectral albedo of relatively thick, snow-free, melting sea ice shows invariance across location, decade, and ice type. In particular, the albedo of snow-free, melting seasonal ice was indistinguishable from that of snow-free, melting second-year ice, suggesting that the highly scattering surface layer that forms on sea ice during the summer is robust and stabilizing. In contrast, the albedo of ponded ice was observed to be highly variable at visible wavelengths. Notable temporal changes in albedo were documented during melt and freeze onset, formation and deepening of melt ponds, and during melt evolution of sediment-laden ice. While model simulations show considerable agreement with the observed seasonal albedo progression, disparities suggest the need to improve how the albedo of both ponded ice and thin, melting ice are simulated.