北冰洋中央密集冰区海冰对太阳短波辐射能吸收的观测研究

The Shortwave Solar Radiation Energy Absorbed by Packed Sea Ice in the Central Arctic

太阳辐射能是海冰融化的最主要能源，基于在2008年8月21～27日北极加拿大海盆中部为期8天的冰站考察中海冰光学观测数据，研究了北冰洋中央密集冰区海冰吸收的太阳辐射能。通过现场直接观测，确定了海冰透射率、反照率、吸收率及其随冰厚的变化，得出海冰对太阳短波辐射的吸收率大约为到达冰面太阳辐射的16％，大部分被冰雪表面反射。为期3天的对太阳辐射的观测表明，虽然到达北冰洋中央密集冰区的太阳辐射能并不少，但由于云和雾覆盖的时间所占的比例很大，有将近57％被大气削弱，其余的又有77％左右被冰雪表面反射回太空，海冰吸收的热量只有10．2W／m。，相当于每天融化2．6mm的冰，1nq厚海冰全部融化需要380天，不足以为海冰融化提供足够的热量。-因此北冰洋中央密集冰区终年被海冰覆盖，即使在北冰洋海冰面积骤减的现状下，那里的海冰密集度仍然接近100％。然而，文章的结果指出：大气中云和雾大幅度减少、积雪层融化、海冰厚度减小、融池的比例增加等因素都会大幅度增加海冰吸收的热量，未来这些过程的发生有可能导致北冰洋密集冰区的海冰快速融化。

The solar energy is the main energy source to melt sea ice in the Arctic. The solar energy absorbed by the packed ice in the central Arctic is studied in this paper based on the optical observations of the Third Chinese Arctic Expedition on an ice camp during the period of August 21-27, 2008. The transmission, albedo, and the absorption rates of the sea ice and their variation with ice thickness are calculated from the observed data. On average, the absorption rate of sea ice for shortwave solar radiation is about 16%, meanwhile, about 77% of the incident energy is reflected back to the space. A three-day optical observation was conducted to determine the a- mount of the arriving solar radiation. Although the solar radiation arriving on the upper atmosphere was still strong in August, but about 57 % of them was reduced by the atmosphere, as the coverage of cloud and fog caused obvious absorption to the shortwave radiation. Therefore, the heat flux absorbed by sea ice was only 10.2 W/m2, corresponding to the heat in melting 2.6 mm ice per day or 1 m ice within 380 days. It means that the weak heat flux did not provide sufficient heat to melt the sea ice there. Therefore, the packed ice still covers the central Arctic O- cean even though the ice coverage becomes nearly the minimum in the whole Arctic. However, the result also indi- cated that some other factors, if appeared, could cause the increased melting of the packed ice, such as the de- crease of cloud and fog, the total melting of snow layer, the reduction of ice thickness, and the increase of the ponds which could especially endanger the permanent packed ice. In the future, it is possible for the sea ice in central Arctic to collapse if more heat is absorbed under the condition different to that of the summer of 2008.