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30 December 2020, Volume 32 Issue 4 Previous Issue    Next Issue

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Recoveries, research progress, and concentration mechanism of meteorites in the Grove Mountains, Antarctica Chen Hongyi, Miao Bingkui, Xia Zhipeng, Xie Lanfang, Zhao Sizhe 2020, 32 (4):  417-434.  DOI: 10. 13679/j.jdyj.20200006 Abstract ( 973 )   PDF (8400KB) ( 831 )   China has successfully recovered 12 665 meteorites in the previous seven expeditions to the Grove Mountain region of Antarctica, unarguably demonstrating that the Grove Mountains are a meteorite concentration area. However, meteorites recovered from the Grove Mountains display larger numbers, lower average weights and smaller proportions of specific types of meteorites compared with other meteorite concentration areas in Antarctica. A total of 9 802 meteorites (106.5 kg) were collected in the third and fourth Grove Mountains expeditions, accounting for 77.4% and 82.5% of the total amount and weight, respectively. Then, the number and weight of meteorites recovered in the Grove Mountain region continually decreased from 1 618(17.1 kg) to ~600 (~2.0 kg)in the following three missions. Compared with mature meteorite concentration areas in Antarctica, the ice flow rate of the Grove Mountains is fast, the flow direction is complex, the crevasses of glacier are well developed, and the prevailing easterly wind in summer is strong, which may be the reasons for the relative enrichment of meteorite fragments in the Grove Mountains. However, the data of ablation rates of blue ice, glacier velocity, and annual meteorological conditions are insufficient. Therefore, it is of great significance to collect glacier change and meteorological data as soon as possible and to establish a model of the meteorite concentration mechanism in the Grove Mountains for reasonable planning of meteorite scientific expeditions to the Grove Mountains and the exploration of new meteorite concentration areas. References | Related Articles | Metrics

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Monitoring ice front changes of the Pine Island Glacier, West Antarctica, during 1947–2020 Chien Yide, Zhou Chunxia, Chen Yiming, Zeng Tao, Liu Jianqiang 2020, 32 (4):  435-451.  DOI: 10. 13679/j.jdyj.20200010 Abstract ( 943 )   PDF (43663KB) ( 811 )   The Pine Island Glacier (PIG), West Antarctica, has been an area of frequent calving and frontal changes in recent years. We present a comprehensive history of ice front changes of the PIG during 1947–2020 derived from optical satellites (Landsat and HY-1C), Synthetic Aperture Radar (SAR) (ERS-1 and RADARSAT), and aerial images. The open-ended box method was also adopted in this study. There were at least 17 large calving events at the PIG in the past 73 years. The calving cycle was approximately 6 years during 1995–2013 and about 1~2 years from 2013 to the present. The velocity near the calving front calculated by the open-box method increased over the past 73 years. Based on our results combined with studies of calving events between 1947 and 2020, we concluded that El Niño, Circumpolar Deep Water, basal melt rates, basal crevasses, ice mélange, and back stress caused by intermittent contact between the ice shelf and the ridge were possible factors resulting in ice shelf calving events. References | Related Articles | Metrics

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Evaluation of four high-resolution sea ice reanalysis products in the Ross Sea and Amundsen Sea Huang Jia, Zhang Zhaoru, Wang Xiaoqiao 2020, 32 (4):  452-468.  DOI: 10. 13679/j.jdyj.20200007 Abstract ( 1013 )   PDF (11918KB) ( 600 )   Four high-resolution global ocean–sea ice reanalysis products were evaluated against observations in the Ross Sea and Amundsen Sea, Antarctica. The assessed quantities included climatological sea-ice concentration, sea-ice thickness, temperature, salinity, and mixed layer depth. The assessment revealed that the performance of the reanalysis products varied among variables and areas. Overall, the results from UR025.4 (University of Reading) were more consistent with observed sea-ice concentration and thickness, whereas the results from C-GLORS (Global Ocean Reanalysis System) had the largest discrepancies from observations. In the surface layer, during ice-freezing seasons, temperature and salinity data from C-GLORS agreed better with the WOA13 (World Ocean Atlas 2013) observations, whereas those from ORAP5 (Ocean ReAnalysis Pilot 5) deviated most from observations. Temperature and salinity data from the four reanalyses were generally consistent with the WOA13 values in deep layers below 700 m. In the subsurface layers, none of the reanalyses stood out from among the four products in hydrography simulations; the multi-model (reanalyses) mean results can reduce the error if the four reanalyses depart from observations in different directions. References | Related Articles | Metrics

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Ocean front locations in the Southwest Pacific Yang Wei, Li Bingrui, Gao Libao, Li Ruixiang, Liu Changjian, Ma Lei 2020, 32 (4):  469-482.  DOI: 10. 13679/j.jdyj.20200030 Abstract ( 966 )   PDF (13262KB) ( 709 )   Six expendable conductivity–temperature–depth sections from Tasmania, Australia to the Ross Sea, Antarctica, and satellite sea surface temperature (SST) data were used to study the distribution of fronts of the Southwest Pacific Ocean.The analysis showed that seasonal variation had no significant influence on the front locations, but that the frontal vertical structure differed.The Subantarctic Front (SAF) and Polar Front (PF) generally had double branches in the Southwest Pacific. For the double branches of the SAF, the temperature gradient of the South-SAF was generally greater than 2.0°C·(100km)–1, whereas the gradient of the North-SAF was generally greater than 1.0°C·(100km)–1. The front locations identified based on in-field data in this paper were basically consistent with the frontal pattern summarized by Orsi et al. in 1995, but the locations were shifted slightly northward. Because of the topographic influence of the Southeast Indian Ridge, the SAF and PF were obviously shifted to the southeast after passing south of Tasmania, Australia, and reached their southernmost points between 170°E and 175°E. The PF location identified based on the SST gradient was farther south relative to the northern boundary of the 2°C isotherm in the subsurface layer; in the 145°E section, the spacing was more than 5 degrees of latitude, whereas in the 155°E section, the spacing was about 1 degree of latitude. Because the Subtropical Front (STF), SAF, and PF had certain influences on the surface temperature, the corresponding frontal locations identified based on the satellite SST gradient were reliable. References | Related Articles | Metrics

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Analysis of influencing factors of the electrical properties of ice cores using dielectric profiling Xu Sijia, Li Yuansheng, An Chunlei, Shi Guitao, Jiang Su, Ma Tianming, Lu Siyu, Wang Danhe 2020, 32 (4):  483-493.  DOI: 10. 13679/j.jdyj.20190072 Abstract ( 749 )   PDF (4633KB) ( 866 )   The paleoclimate information recorded in ice cores is often extracted and analyzed based on chemical and physical indicators. The electrical properties of ice cores are among the fundamental physical indices. To quantitatively determine the responses of ice cores under alternating current power, dielectric profiling (DEP) was developed and applied to ice core analysis. However, the technical parameters of DEP equipment need to be explored further for field measurement. In addition, the electrical responses to changes in ice core composition are not yet fully understood. Therefore, we first produced artificial ice cores using different ion types and concentration gradients. Based on the DEP measurement method for artificial ice cores developed by China, a method for measuring Antarctic ice cores is developed. Next, the relationships among the DEP signal (conductivity signal and permittivity signal), chemical factors, ice core crystallization rate, ice core gas content, and ice core dust content were investigated using these ice cores. The DEP signal showed a significant linear relationship with hydrogen ions, chloride ions, and ammonium ions in the ice cores. In addition, decrease of the crystallization rate, increase of the ice core gas content, and increase of the dust content (plant ash) may cause decline of the DEP signal in Antarctic ice cores. References | Related Articles | Metrics

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The characteristics of the polar ionosphere in the geomagnetic coordinates system Wu Yewen, Liu Ruiyuan, Zhang Beichen, Hu Hongqiao, Ci Ying, Jiang Mingbo, Lv Jianyong 2020, 32 (4):  494-503.  DOI: 10. 13679/j.jdyj.20200064 Abstract ( 752 )   PDF (1152KB) ( 771 )   The mean Polar Electron Content (mPEC) over the low solar activity years 2007–2010 in Corrected Geomagnetic Latitude and Magnetic Local Time Coordinates (CGLMLT) is calculated to investigate the Universal Time (UT) variations of the polar ionosphere based on the observation of Constellation Observing System for Meteorology, Ionosphere, and Climate satellite (COSMIC). The results show clear UT variations on mPEC both in the Arctic and Antarctic when seen in the geomagnetic coordinate system. The UT variation of the mPEC changed in a sinusoidal way, with the phase difference about 12 hours between the Arctic and Antarctica. In addition, the UT variation is about 2~3 times larger in the Antarctic than in the Arctic. These features should result from the separation between the geographic pole and the geomagnetic pole. Actually in geographic coordinate system, the UT variation of the mPEC is rather small. The reason should be that the UT variations of mPEC come from solar radiation as well as horizontal transportation in geomagnetic coordinates but only horizontal transportation in geographic coordinate systems. References | Related Articles | Metrics

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Biodiversity analysis of cultured agar-degrading bacteria from surfaces of Antarctic macroalgae Gui Yuanyuan, Gu Xiaoqian, Li Jiang, Zhang Peiyu 2020, 32 (4):  504-511.  DOI: 10. 13679/j.jdyj.20190076 Abstract ( 848 )   PDF (4790KB) ( 906 )   To analyze the diversity of cultured agar-degrading bacteria from the surfaces of six Antarctic macroalgae samples collected from King George Island, a selective medium and Lugol’s iodine staining method were used to screen and purify the agar-degrading bacteria, and the phylogenetic relationships of these strains were then investigated according to their 16S rRNA sequences. Thirty-seven strains of agar-degrading bacteria were screened, purified, and identified as belonging to the Gammaproteobacteria, Flavobacteriia, and Actinobacteria, respectively. At the genus level, the strains were classified as Pseudoalteromonas, Colwellia, Shewanella, Psychrobacter, Pseudomonas, Halomonas, Photobacterium, Flavobacterium, Zobellia, and Salinibacterium, in addition to a strain that was classified as belonging to the family Thiotrichaceae. Among them, Flavobacterium and Zobellia belong to the Flavobacteriia, Salinibacterium belongs to the Actinobacteria, and the remaining genera belong to the Gammaproteobacteria. The most dominant genus of agar-degrading bacteria was Pseudoalteromonas (20/37), followed by Psychrobacter(4/37). Shewanella, Psychrobacter, Pseudomonas, Halomonas, Photobacterium, and the member of the family Thiotrichaceaeare the first reported taxa with agar-degrading activity isolated from the surfaces of macroalgae in Antarctica. The results not only expand our knowledge of the diversity of agar-degrading bacteria, but also contribute to the investigation and exploitation of Antarctic microbial resources. References | Related Articles | Metrics

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Bacterial community structure of intertidal sediments in the Fildes Peninsula, Antarctica, and preliminary screening of enzyme-producing strains Wu Leilei, Shang Li, Sun Hao, Shi Xiaochong, Zhang Xiaohua 2020, 32 (4):  512-522.  DOI: 10. 13679/j.jdyj.20190069 Abstract ( 826 )   PDF (1319KB) ( 858 )   To study the composition of the bacterial community and enzyme-producing activity of cultivable bacteria in the intertidal sediments of the Fildes Peninsula, Antarctica, sediment samples from 19 sites of the intertidal zone were collected, and the bacterial community composition of these sediments was sequenced by high-throughput sequencing using Illumina MiSeq technology. The absolute abundance of total bacteria in the sediments was measured by real-time PCR. The plate coating method was used to purify and isolate the culturable bacteria of sediment samples from 16 sites. Thirty-eight strains of bacteria were selected for the screening of enzyme activities. In total, 2 375 operational taxonomic units (OTUs) of the intertidal sediment samples were obtained, and these OTUs were assigned into 42 bacterial phyla, of which Proteobacteria, Bacteroidetes, and Actinobacteria were the dominant groups. The abundance of total bacteria ranged from 2.51 × 107 to 6.65 × 108 copies·g−1. Among culturable bacteria, 129 strains were assigned to four phyla, 25 genera, and 50 species. Proteobacteria, Actinobacteria, and Bacteroides were the predominant groups, which were basically consistent with the results of high-throughput sequencing. Thirty-eight strains were selected for the screening of low-temperature enzyme activities (including lipase, amylase, gelatinase, alginate, and cellulase), and 17 strains were found to produce lipase, 24 strains produced amylase, 18 strains produced gelatin, four strains produced alginate, and four strains produced cellulase. References | Related Articles | Metrics

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Design and application of a real-time temperature and salinity profile observation system under ice for polar regions Wang Deliang, Zhang Suwei 2020, 32 (4):  523-532.  DOI: 10. 13679/j.jdyj.20190073 Abstract ( 813 )   PDF (6530KB) ( 1386 )   The observation of temperature and salinity profiles under ice is an important aspect of polar marine environmental monitoring. The large number of ice floes is the main feature of the polar ocean environment. Conventional ocean observation equipment such as Argo buoys and underwater gliders cannot fixed positions and transfer satellite observations under the ice, which is also the main reason for the relative scarcity of temperature and salinity profile data and space–time discontinuity in the polar regions. To observe temperature and salinity profiles in the depth range of 0–200 m under the ice, we developed a real-time observation system based on the domestic HM2000 profiling buoy, which integrated the ice surface communication equipment and anchor platform. A breakthrough was achieved in the key technology of inductive coupling communication, and a two-way communication link between the shore station and profile buoy was established. In August 2018, the system was successfully deployed and applied in the ninth Arctic scientific expedition of China. References | Related Articles | Metrics

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Delimitation of the continental shelf beyond 200 nautical miles in the Arctic Ocean Yin Jie, Li Jiabiao, Fang Yinxia 2020, 32 (4):  533-543.  DOI: 10. 13679/j.jdyj.20200017 Abstract ( 861 )   PDF (13622KB) ( 496 )   As of 2020, four of the five countries surrounding the Arctic Ocean, excluding the United States, which has not yet approved the United Nations Convention on the Law of the Sea, have introduced submissions for the continental shelf beyond 200 nautical miles (M) in the Arctic Ocean. Among them, Russia, Canada, and Denmark have laid claims to large continental shelf areas based on the large-scale submarine features in the Arctic Ocean. If all claims were approved by the Commission on the Limits of the Continental Shelf, there would be very little international seabed area left. However, considering the particularity of the geological structure in the Arctic Ocean, there are many uncertainties in the application of Article 76 of the United Nations Convention on the Law of the Sea, resulting in multiple possibilities of outer limits. In accordance with Article 76 of the United Nations Convention on the Law of the Sea, Scientific and Technical Guidelines of the Commission, and with consideration of practices on the delimitation of the continental shelf, for this manuscript, comparative study was carried out on the continental shelf claims of coastal states in the Arctic Ocean. Based on current scientific research on the Lomonosov Ridge and the Alpha–Mendeleev Ridge Complex, it is suggested that the ridge issues within Article 76 should be applied with caution. The issue of regionalization of the continental shelf by the coastal states of the Arctic Ocean will likely have a negative impact. References | Related Articles | Metrics

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Modeling and evaluation of ocean wind energy locations in the Arctic Northwest Passage Qian Heng, Zhang Ren 2020, 32 (4):  544-554.  DOI: 10. 13679/j.jdyj.20190053 Abstract ( 831 )   PDF (2541KB) ( 979 )   The grade division of wind energy development is the main basis of site selection for wind power generation. To address the problem of offshore wind energy location in the Arctic Northwest Passage, a set of evaluation systems of wind energy development grades with polar region characteristics was established, which was analyzed by combining with a comprehensive evaluation model (CA-SSTFN) based on triangular fuzzy number stochastic simulation. According to the comparison test results between the model and the evaluation technologies of analytic hierarchy process (AHP) and fuzzy AHP, CA-SSTFN can objectively realize the fusion and reasoning of multi-source environmental information, and the evaluation results expressed in the form of confidence intervals provide more information on the reliability of the evaluation results than do the results of existing conventional methods. The evaluation results are more consistent with the actual situation and have good evaluation performance. At the same time, the model also has updating capability based on information detection, which can realize real-time or quasi-real-time evaluation of value. Finally, the central sea area of Amundsen Bay was taken as an example for analysis. The results indicate that the value of wind energy development in this sea area is generally good, especially in summer, which is also the best passage period for the current Northwest Passage, adding value to wind energy development. Overall, the recommended development pilot area is in the region of 70.5°N, 124°W. References | Related Articles | Metrics

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Spatiotemporal distribution patterns of active fire in the Arctic region Xue Naiting, Zhang Zhen, Du Zhiheng, Hu Kehong, Zhang Shasha, Huang Danni 2020, 32 (4):  555-564.  DOI: 10. 13679/j.jdyj.20190075 Abstract ( 795 )   PDF (5494KB) ( 834 )   Based on Fire Information for Resource Management System (FIRMS), MODIS and VIIRS active fire position data, dynamic changes of active fires in the Arctic region were analyzed at different temporal (yearly, monthly, and hourly) and spatial (country) scales from 2000 to 2018, to provide a basis for the prediction and management of active fires. The results showed that: (1) from 2000 to 2018, MODIS C6 (MODIS NRT 1 km active fire products, MCD14DL) and VIIRS V1 (VIIRS NRT 375 m active fire products, VNP14IMGTDL_NRT) active fire frequency trends were consistent, with maximum and minimum values appearing in 2013 and 2015 respectively. (2) In the Arctic region, the country with the greatest cumulative active fire frequency was Russia, and the country with the lowest active fire frequency was Norway. The interannual variations of the two sets of products were quite similar in different countries. (3) The active fires in the seven countries of the Arctic region (Russia, the United States, Canada, Denmark, Norway, Sweden, and Finland) were mainly concentrated in June–August, and the active fire observation period was mainly concentrated around 12:00 local time in various countries. References | Related Articles | Metrics

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Accuracy evaluation and testing of an AHRS in high-latitude areas Guo Zhengdong, Ben Yueyang, Cui Wentin 2020, 32 (4):  565-570.  DOI: 10. 13679/j.jdyj.20200029 Abstract ( 745 )   PDF (1176KB) ( 899 )   The traditional attitude and heading reference system (AHRS) cannot provide reliable heading data in high-latitude areas. To address this problem, mechanization based on transverse coordinates for an AHRS is proposed for attitude and heading calculations. In terms of the requirements of accuracy evaluations in-high latitude areas, the relative specification evaluation method was employed to remove the adverse effect of latitude variance. Moreover, a scenario of a sailing trial for high-latitude navigation was designed, and a corresponding polar trial was carried out. The trial results showed that a fiber-optic gyro-compass using mechanization based on transverse coordinates could serve as a reliable AHRS in high-latitude areas. References | Related Articles | Metrics

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Research progress on ice sheet mass balance in Antarctica and Greenland Ye Yue, Cheng Xiao, Liu Yan, Yang Yuande, Zhao Liyun, Lin Yijing, Qu Yutong 2020, 32 (4):  571-585.  DOI: 10. 13679/j.jdyj.20190060 Abstract ( 1013 )   PDF (1636KB) ( 1649 )   Ice sheet mass balance is the biggest source of uncertainty in predicting sea level rise and has a large impact on global sea level. With the rapid development of satellite remote sensing, great progress has been made in ice sheet mass balance studies. This paper discusses the methods of estimating ice sheet mass balance and the development of satellite data, with detailed analysis of the uncertainty and sources of error for each method, and provides references for future ice sheet mass balance studies. The results of satellite altimetry, satellite gravimetry techniques, the input and output method, and the reconciled estimate method are also discussed. Ice sheet mass balance will remain a focus of global change research. Moreover, improving satellite performance to reduce the uncertainty of observation data, innovating estimation methods to reduce the uncertainty of results, and strengthening ground observation verification are expected to be future research hotpots. References | Related Articles | Metrics

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Progress of application of eDNA technology in polar water environments Liu Mengyue, Zhao Wenyu 2020, 32 (4):  586-595.  DOI: 10. 13679/j.jdyj.20200004 Abstract ( 882 )   PDF (392KB) ( 803 )   Environmental DNA (eDNA) technology has been applied to efficiently and accurately carry out research works involving species identification and diversity analysis of organisms in polar aquatic ecosystems (such as polar oceans, coastal waters, lakes, and streams). This is of great value for the development of biological resources in polar region, prediction of changes in the balance and stability of global aquatic ecosystems, and research on ecological issues in extreme habitats. In recent years, eDNA technology has developed rapidly, effectively addressing the disadvantages of traditional methods in the study of aquatic ecosystems, and improving the investigation of aquatic animals. This review describes progress in the application of eDNA technology in biodiversity analysis, species identification, population structure analysis, and other ecological research on aquatic organisms such as fish, benthic organisms, plankton, and viruses in polar aquatic environments. As a new biological survey method, eDNA technology can drastically accelerate the updating of modern biodiversity methodologies in the current molecular era, and has infinite prospects in polar aquatic biodiversity research. References | Related Articles | Metrics

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Contributions to the MOSAiC from China Lei Ruibo 2020, 32 (4):  596-600.  Abstract ( 596 )   PDF (271KB) ( 1029 )   References | Related Articles | Metrics