Physical and optical characteristics of sea ice in the Pacific Arctic Sector during the summer of 2018
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Physical and optical characteristics of sea ice in the Pacific Arctic Sector during the summer of 2018 Xiaowei Cao1, Peng Lu1*, Ruibo Lei2, Qingkai Wang1, Zhijun Li1 1 State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116024, China 2 MNR Key Laboratory for Polar Science, Polar Research Institute of China, Shanghai 200136, China
Received 22 October 2019; accepted 2 January 2020 © Chinese Society for Oceanography and Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract
The reduction in Arctic sea ice in summer has been reported to have a significant impact on the global climate. In this study, Arctic sea ice/snow at the end of the melting season in 2018 was investigated during CHINARE-2018, in terms of its temperature, salinity, density and textural structure, the snow density, water content and albedo, as well as morphology and albedo of the refreezing melt pond. The interior melting of sea ice caused a strong stratification of temperature, salinity and density. The temperature of sea ice ranged from –0.8°C to 0°C, and exhibited linear cooling with depth. The average salinity and density of sea ice were approximately 1.3 psu and 825 kg/m3, respectively, and increased slightly with depth. The first-year sea ice was dominated by columnar grained ice. Snow cover over all the investigated floes was in the melt phase, and the average water content and density were 0.74% and 241 kg/m3, respectively. The thickness of the thin ice lid ranged from 2.2 cm to 7.0 cm, and the depth of the pond ranged from 1.8 cm to 26.8 cm. The integrated albedo of the refreezing melt pond was in the range of 0.28–0.57. Because of the thin ice lid, the albedo of the melt pond improved to twice as high as that of the mature melt pond. These results provide a reference for the current state of Arctic sea ice and the mechanism of its reduction. Key words: sea ice, snow, refreezing melt pond, physical properties, albedo Citation: Cao Xiaowei, Lu Peng, Lei Ruibo, Wang Qingkai, Li Zhijun. 2020. Physical and optical characteristics of sea ice in the Pacific Arctic Sector during the summer of 2018. Acta Oceanologica Sinica, 39(9): 25–37, doi: 10.1007/s13131-020-1645-6
1 Introduction Sea ice has been long considered an important factor affecting global systems and an effective climatologic indicator, owing to its sensitivity to climate change (Honda et al., 2009; Huang et al., 2013; Lei et al., 2018; Johannessen et al., 2004). Research has shown that Arctic sea ice has decreased in terms of extent (Comiso et al., 2008; Stroeve et al., 2012), thickness (Cheng et al., 2008; Lindsay and Schweiger, 2015; Renner et al., 2014) and multiyear ice (Comiso, 2012) over the past few decades. In particular for the melting season, the average extent of September Arctic sea ice decreased by 8.76% per decade from 1980 to 2017 (data obtained from the National Snow and Ice Data Center). From 2011 to 2018, the thickness of Arctic sea ice at the end of the melt season has decreased by 2 m, or approximately 6
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