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Study on the long-term variability of Subantarctic and Polar Fronts in austral summer during 1980-2015 Quan Shanyuan, Shi Jiuxin 2019, 31 (3):  231-245.  DOI: 10.13679/j.jdyj.20190015 Abstract ( 855 )   PDF (10482KB) ( 688 )   The variability of the Subantarctic Front (SAF) and Polar Front (PF) in austral summer (January–March) during 1980–2015 was investigated using monthly mean potential temperature and salinity reanalysis data, and by applying criteria based on physical phenomena and fixed property values to frontal detection. The results derived from two types of criterion were consistent with each other regarding the long-term trend of frontal position during the 36–year period. In terms of circumpolar average, no significant trend of frontal movement was found between 1980 and 2015, although frontal variability appeared as fluctuation during these years. The migration amplitude, stability and long-term trend of the fronts showed regional differences. Minimal displacement and high stability were found in regions with large topographic obstacles, whereas the fronts move significantly and frequently in deep basins and downstream of obstacles. The regions with the highest stability and the smallest long-term movement of the SAF and PF were found in the Indian and Atlantic sectors, respectively. In the eastern Pacific sector, the SAF showed significant long-term movement with both northward and southward shifts, whereas southward displacement of the PF dominated the Indian sector. On decadal and interannual timescales, evident differences were found between the results of frontal detection derived from the two criteria; thus, the applicability of both criteria was discussed accordingly. For the PF, the criterion based on the temperature phenomenon was found more stable than the isotherm criterion. References | Related Articles | Metrics

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Study on surface elevation changes of Arctic glacier Austre Lovénbreen using RTK-GPS Ding Xi, Ai Songtao, Wang Zemin, Hao Weifeng, Tan Zhi 2019, 31 (3):  246-257.  DOI: 10.13679/j.jdyj.20190003 Abstract ( 727 )   PDF (9868KB) ( 503 )   Mass changes of the Austre Lovénbreen Arctic valley glacier have been studied using elevation changes based on high-precision RTK-GPS measurements. Using RTK-GPS data, several spatial interpolation methods were compared to produce a digital elevation model (DEM) of the glacier surface. Considering the smoothness of the glacier surface, the natural neighbor method was considered most suitable for generating the DEM. Two approaches were compared for evaluating the elevation changes of the glacier during 2013–2015: using DEMs generated from direct surface interpolation of RTK-GPS points and calculating the elevation bias of crossover points from RTK-GPS profiles of different years. The results showed that elevation changes calculated from crossover points were much more accurate than using the direct surface interpolation method, which had obvious errors in GPS empty areas. A density assumption for ice and snow was used to convert elevation change to water equivalent to study the mass balance. Assuming density of 900 and 500 kg m-3 in the ablation and accumulation zones, respectively, the corresponding mass balance in 2013–2014 and 2014–2015 was -0.277 and 0.065 m w.e., respectively. These results differed slightly from classical glaciological mass balances primarily because of the discrepancy of the observation period and potential subglacial mass changes. The correlation between the elevation changes of crossover points and their corresponding altitude was determined. Despite some anomalies in certain regions, strong correlation was found between mass change and altitude, i.e., some mass accumulation occurred in high-altitude areas, while mass loss increased with decreasing altitude. The annual mean gradient of mass change versus altitude was approximately 2.67‰. References | Related Articles | Metrics

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Analyses of Arctic sea ice density variation and its impact on sea ice thickness retrieval Li Bingjie, Pang Xiaoping, Ji Qing 2019, 31 (3):  258-266.  DOI: 10.13679/j.jdyj.20180059 Abstract ( 840 )   PDF (6967KB) ( 631 )   Sea ice density is an important variable of sea ice physics and climate models, and it is key parameter for the retrieval of sea ice thickness from satellite altimeters. Physical investigations of Arctic sea ice have been conducted during many scientific expeditions; however, in situ measurements of sea ice density acquired in recent years still require further sorting and analysis. In this context, we collected 15 years’ data of Arctic sea ice density. We analyzed the variability of sea ice density, calculated sea ice thickness, based on the hydrostatic equation with in situ sea ice density after applying Kriging interpolation, and discussed the influence of sea ice density on sea ice thickness retrieved via satellite altimetry. Results showed that the annual mean sea ice density varied from 750 to 950 kg·m-3 during from 2000 to 2015. From January to September, the monthly mean sea ice density tended to decrease, and it generally decreased with latitude during June–September. Comparative analysis revealed it is more suitable to use sea ice density after data interpolation than to use a fixed constant density for sea ice thickness retrievals. Sorting and analysis of Arctic in situ sea ice density could provide a reference for further research on Arctic sea ice and climate change. References | Related Articles | Metrics

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Projection of long-term changes of mountain glacier based on GIS grid poeration method Ai Songtao, Yan Boya, Wang Zemin, Lin Guobiao 2019, 31 (3):  267-275.  DOI: 10.13679/j.jdyj.20180050 Abstract ( 707 )   PDF (3006KB) ( 994 )   A Geographical Information System (GIS) has powerful functions with which to analyze spatial data. This study constructed a model using GIS methods to simulate long-term changes of the polythermal Austre Lovénbreen Arctic mountain glacier. The GIS methods can be used to quickly and efficiently obtain the ice thickness, length of the mainstream line, surface area and ice volume of the glacier within the simulation. The variation of glacier volume in the time series was found consistent with the curve of the high-order function. Compared with the results of the Elmer/Ice modeling, in the first 90 years, it is feasible to study changes of a glacier on a scale of one to several decades using the GIS simulation methods. The GIS methods can be used to perform rapid quantitative analysis of geometric parameters to support research on mountain glacier change. References | Related Articles | Metrics

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Gridded data generating technology of atmospheric visibility in the Arctic sea based on artificial neural network Shan Yulong, Zhang Ren, Li Ming 2019, 31 (3):  276-283.  DOI: 10.13679/j.jdyj.20180056 Abstract ( 794 )   PDF (795KB) ( 1032 )   With the gradual opening of the Arctic Passage, attention is increasing on the assessment of risk associated with sailing across the Arctic. In addressing the problem of the lack of visibility data in the Arctic region, this study proposed a technique for generating gridded visibility data by fusing reasoning results and measured visibility data. Through determination of the factors influencing visibility, the generation of sample data sets, comparison of the fitting effects between an artificial neural network and a Bayesian network and revision of the inferred results, an inference model of gridded visibility data was constructed based on an artificial neural network and the reasoning and interpolation results of visibility were compared. In comparison with the interpolation technique, the results showed the inference model produced values that were more accurate. Therefore, the developed technique could provide important reference material for risk assessment studies of the Arctic Passage. References | Related Articles | Metrics

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The Moho depth in the Canadian Basin and its tectonic implications Ma Yuanyuan, Zhao Lihong, Ling Zilong, Yang Mingming, Pang Beibei 2019, 31 (3):  284-290.  DOI: 10.13679/j.jdyj.20180026 Abstract ( 786 )   PDF (10984KB) ( 581 )   We correct their gravitational effect of the water depth, sediment thickness and average crustal thickness using the latest gravity data from the Arctic Canada Basin and its surrounding areas. And then we collect the sonar buoy data of the area and digitize 57 control points. We calculate the Moho depth of this area using the interface with controlling point based on the Parker method. The results show that the Moho depth gradually deepens from west to east .It’s shallowest at the junction between the edge and the west of the basin, about 12 km, indicating that there may be insufficient compensation. The Moho in Alaska has the deepest depth, at least 30km, supposing that the area is more strongly squeezed or abundant supplies of sediment thickens the crust. The change of depth is consistent with the changes in the crust structure of the oceanic-continental transition zone-continental crust, which supports a counterclockwise rotation pattern. Related Articles | Metrics

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A comparative study of ionospheric TEC derived from DPS-4 and GPS observations at Zhongshan Station, Antarctic Yu Houfang, Chen Xiangcai, Liu Jianjun, He Fang 2019, 31 (3):  291-300.  DOI: 10.13679/j.jdyj.20190005 Abstract ( 687 )   PDF (3493KB) ( 796 )   Based on the observations of Digisonde Portable Sounder-4 (DPS-4) and GPS receiver in 2013 at Zhongshan Station, Antarctica, a comparative study on the daily and seasonal variation characteristics of ionospheric total electron content (TEC) with solar flux and geomagnetic activity is carried out. The result shows that the average TEC values have positive correlation with solar flux, whereas it’s negative correlation with geomagnetic activity. Although a dawn/dusk asymmetry of average TEC variations can be easily observed, the average TEC variations between DPS and GPS are trend to be largely agreement and similar, and the linear correlation coefficient is generally 0.86. Factors controlling the agreement are briefly analyzed, including GPS elevation angle, topside contribution to DPS TEC, and the variations of plasma convection and neutral atmospheric composition. References | Related Articles | Metrics

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Estimating the profiles of atmospheric turbulence above the South Pole by Thorpe scale Hu Xiaodan, Wu Xiaoqing, Qing Chun 2019, 31 (3):  301-308.  DOI: 10.13679/j.jdyj.20180058 Abstract ( 705 )   PDF (562KB) ( 852 )   Based on analysis of conventional meteorological parameters of sounding data above the South Pole in 2012, this study determined the boundary layer height above the South Pole throughout the entire year and used the Thorpe scale to estimate the refractive index structure constant profiles, atmospheric coherence length, seeing and isoplanatic angle. The seeing above and within the boundary layer and its integrated contribution to the entire layer (0–25 km) was compared with results in the literature. The comparison showed that the estimated profiles of decreased rapidly with height near the ground, decreased slowly above 300 m, presented a bulge after 5 km and decreased steadily after 10 km. Moreover, they were characterized by the fact that most of the turbulence was concentrated below 300 m. In winter above the South Pole, the Thorpe scale estimate of the average seeing and the seeing below 270 m was 1.87" and 0.39", respectively, consistent with the results of other studies. However, in comparison with other models, the estimates can be obtained more easily using the Thorpe scale. References | Related Articles | Metrics

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Occurrence and resource potential of gas hydrate in the Alaska North Slope Basin of the Arctic Yang Chupeng, Liu Jie, Yang Rui, Hu Xiaosan, Yao Yongjian, Wang Zhe, Li Xuejie 2019, 31 (3):  309-321.  DOI: 10.13679/j.jdyj.20180065 Abstract ( 745 )   PDF (5770KB) ( 1182 )   The Alaska North Slope Basin (ANSB) is one of the earliest areas for gas hydrate investigation and research in the world, and it has an exemplary role in global gas hydrate studies. In this work, the metallogenic geological conditions and regularities of natural gas hydrates in the ANSB were summarized systematically by means of literature-based research and analysis. It is believed that the gas hydrate system of the ANSB is a shallow derivation of the underlying Cretaceous–Tertiary petroleum system, which is the result of multiple factors including gas sources, faults, lithology and the special environment (i.e., permafrost, stratum temperature and pressure field). Based on the above inference, three levels of prospective resource areas in the ANSB were determined using simulation calculations, and the gas hydrate resource in the entire Alaska area was estimated to be 6.0 × 1012 m3 standard natural gas. Overall, the Class I prospective areas are distributed mainly in the coastal permafrost and shelf areas of the ANSB, and their resource potential was estimated to be 2.83 × 1012 m3 standard natural gas. References | Related Articles | Metrics

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Analysis on spatiotemporal variation and influencing factors of net primary productivity in the Southern Ocean Wu Yueyuan, Hou Shugui, Wu Shuangye, Pang Hongxi, Liu Ke, Yu Jinhai 2019, 31 (3):  322-333.  DOI: 10.13679/j.jdyj.20180042 Abstract ( 867 )   PDF (10275KB) ( 661 )   It is important to investigate the spatiotemporal distribution and recent trend of net primary productivity (NPP) in the Southern Ocean because the region is the largest carbon sink within the global ocean. Based on NPP, sea surface temperature (SST) and sea ice concentration (SIC) data of the Southern Ocean during 2003–2016, the spatiotemporal distribution and recent trend of NPP in the Southern Ocean, and the correlation of both SST and SIC with NPP were analyzed. The results showed that annual average NPP within the study area was in the range 64.00–2.26 × 105 mg C m?2·a?1, and annual NPP of the Indian Ocean sector, Atlantic Ocean sector and Pacific Ocean sector was 0.568, 0.431 and 0.262 Gt C·a?1, respectively. In the Southern Ocean, NPP presented regional variation. For example, NPP around the Antarctic continent and in the Weddell Sea was low; however, areas near islands showed higher NPP. Moreover, high values were also found near the front of the ice shelf. Because of the seasonal change in solar radiation, NPP in the Southern Ocean has seasonal variation with highest (lowest) values in austral summer (winter). During 2003–2016, significant increase in NPP occurred only in the Indian Ocean sector. Furthermore, the trend of NPP in each sector was found correlated with the variation of SST and SIC. References | Related Articles | Metrics

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Analysis of legal attributes of the International Code for Ships Operating in Polar Waters Yuan Xue, Tong Kai 2019, 31 (3):  334-345.  DOI: 10.13679/j.jdyj.20180048 Abstract ( 829 )   PDF (356KB) ( 1110 )   The International Code for Ships Operating in Polar Waters (referred to as the Polar Code) is a technical international rulebook established by the International Maritime Organization to safeguard shipping in polar waters and prevent environmental pollution. The system of the Polar Code is based on amendments of the MARPOL, SOLAS and STCW conventions and it inherits their technical and forward-looking attributes. However, in terms of universality, the code cannot be regarded as “generally accepted international rules and standards” because of issues concerning the rule maker, legislative structures and actual implementation of the code. China should absorb the advanced legislative concepts and actively strengthen its domestic implementation of the code to meet the requirements of the upcoming peak in Arctic shipping. In addition, given the relative independence between the Polar Code and the “ice-covered areas” clause of the United Nations Convention on the Law of the Sea(referred to as the Convention) , China should actively advocate application of the Polar Code as the core standard in polar regions, while complying with unilateral legislation of coastal countries. China’s use of the Arctic Passage is increasing annually and therefore the legal attributes of the Polar Code must be clarified to safeguard China’s Arctic shipping interests. References | Related Articles | Metrics

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A review on the Arctic research using CiteSpace Wang Li, Yang Linsheng, Huang Jixia, Jinmei Lu 2019, 31 (3):  346-363.  DOI: 10.13679/j.jdyj.20180049 Abstract ( 752 )   PDF (7453KB) ( 519 )   Based on the core collection database of the Web of Science (2001–2017), this study used CiteSpace to review Chinese and international research on the Arctic and to elucidate active research trends and patterns of collaboration. In China, Arctic research has transitioned from its original focus on Arctic climate change and sea ice studies, to concerns related to Arctic shipping and, more recently, to Arctic strategy and/or governance. Internationally, research publications related to the Arctic have experienced three periods of significant increase: 1990, 2000 and 2005, dominated by the arctic countries, Germany, the United Kingdom and France. Most collaborations on Arctic research are domestic, although international institutional collaborations have occurred in recent years, exemplified by the Helmholtz Centre for Polar and Marine Research (Germany), The Arctic University of Norway (Norway), Aarhus University (Denmark) and the Korea Polar Research Institute (South Korea). Hot keywords include “Arctic Ocean,” “climate,” “Arctic temperature,” “variability,” “sea ice” and “model,” indicating the hot research topics are climate change, sea ice, and Arctic oscillation related. Arctic shipping has dominated recent related publications in China. A comparative systematic review of Chinese and international studies on the economic benefits of Arctic shipping revealed that sea ice is the main factor constraining Arctic shipping. In general, Chinese researchers are optimism in terms of economic benefits, international researchers are more pro-dialectic. Chinese studies tend to focus on technical issues, management, human resources, energy consumption, time consumption and navigation, whereas international research additionally considers aspects such as trade demand, willingness for shipping (risks) and climatic impacts. References | Related Articles | Metrics

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Briefing of 35th Chinese National Antarctic Research Expedition Li Bingrui 2019, 31 (3):  364-367.  Abstract ( 611 )   PDF (249KB) ( 1266 )   References | Related Articles | Metrics

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ISPRS Geospatial Week 2019 Tang Xueyuan 2019, 31 (3):  368-369.  Abstract ( 561 )   PDF (208KB) ( 798 )   References | Related Articles | Metrics