Abstract
Arctic sea ice concentration (SIC) has been studied extensively using passive microwave (PM) remote sensing. This technology could be used to improve navigation along vessel cruise paths; however, investigations on this topic have been limited. In this study, shipborne photographic observation (P-OBS) of sea ice was conducted using oblique-oriented cameras during the Chinese National Arctic Research Expedition in the summer of 2016. SIC and the areal fractions of open water, melt ponds, and sea ice (Aw, Ap, and Ai, respectively) were determined along the cruise path. The distribution of SIC along the cruise path was U-shaped, and open water accounted for a large proportion of the path. The SIC derived from the commonly used PM algorithms was compared with the moving average (MA) P-OBS SIC, including Bootstrap and NASA Team (NT) algorithms based on Special Sensor Microwave Imager/Sounder (SSMIS) data; and ARTIST sea ice, Bootstrap, Sea Ice Climate Change Initiative, and NASA Team 2 (NT2) algorithms based on Advanced Microwave Scanning Radiometer 2 (AMSR2) data. P-OBS performed better than PM remote sensing at detecting low SIC (< 10%). Our results indicate that PM SIC overestimates MA P-OBS SIC at low SIC, but underestimates it when SIC exceeds a turnover point (TP). The presence of melt ponds affected the accuracy of the PM SIC; the PM SIC shifted from an overestimate to an underestimate with increasing Ap, compared with MA P-OBS SIC below the TP, while the underestimation increased above the TP. The PM algorithms were then ranked; SSMIS-NT and AMSR2-NT2 are the best and worst choices for Arctic navigation, respectively.
Highlights
Arctic sea ice cover has undergone substantial changes in recent decades, such as reductions in sea ice thickness [1,2] and extent [3,4], loss of sea ice volume [5] and multiyear ice coverage [6,7], and a rapid decline in sea ice concentration (SIC) in summer and early autumn [8,9]
With the objective to perform a detailed evaluation on the performances of passive microwave (PM) algorithms in estimating SIC along the vessel routes from the perspective of guiding Arctic navigation, a shipborne photographic observation (P-OBS) program was conducted as a part of the Chinese National Arctic Research Expedition in the summer of 2016
The sea ice concentration (SIC) and areal fractions of open water, melt ponds, and sea ice (Aw, Ap, and Ai, respectively) along the strip were calculated based on the collected images, which were processed using image partitioning and geometric orthorectification
Summary
Arctic sea ice cover has undergone substantial changes in recent decades, such as reductions in sea ice thickness [1,2] and extent [3,4], loss of sea ice volume [5] and multiyear ice coverage [6,7], and a rapid decline in sea ice concentration (SIC) in summer and early autumn [8,9]. Several algorithms have been developed to estimate Arctic SIC based on PM data, such as NASA Team (NT) and its enhanced version (NASA Team 2, NT2), Bootstrap, Arctic radiation and turbulence interaction study (ARTIST) sea ice (ASI), and the European Space Agency (ESA) Sea Ice Climate Change Initiative (SICCI) algorithms. Based on these algorithms, more variability and unknown aspects of the SIC in the Northern Polar Region have been revealed [15,16,17]
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