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Subglacial conditions and processes of the Antarctic ice sheet based on bedrock roughness: A review Li Yanjun , Cui Xiangbin, Qiao Gang, Lang Shinan 2022, 34 (4):  401-418.  DOI: 10.13679/j.jdyj.20210085 Abstract ( 1130 )   PDF (9859KB) ( 816 )   Subglacial topography is an important indicator that both reflects and itself influences subglacial conditions and processes of the Antarctic ice sheet. Ice sheet dynamics and basal erosional processes erode pre-glacial topography. As such, bedrock roughness metrics can act as indicators of subglacial conditions and processes (including spatial variability thereof). More specifically, bedrock roughness data can help deduce the material composition of the bedrock, the conditions of sub-glacial erosion and basal sliding, ice dynamics, and subglacial geomorphology. In this study, the potential utility of bedrock roughness characterization and the development of associated quantitative methods are introduced. We focus on the evolution of two methods, one is based on the statistical characteristics of the topography-derived (topographic) roughness and the other is the scattering-derived roughness. Then, relevant studies on subglacial conditions and ice sheet evolution using bedrock roughness were reviewed by evaluating the relationship between bedrock roughness and ice dynamics, subglacial geomorphology, basal thermal mechanism, subglacial geology, and so forth. Finally, the current situation and future potential developments around the study subglacial conditions and processes using bedrock roughness are considered. References | Related Articles | Metrics

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Spatiotemporal variations of Arctic multi-year ice from 2000 to 2019 Hu Haihan , Zhang Zhilun, Li Xinqing, Hui Fengming, Zhao Jiechen, Zhuang Qifeng 2022, 34 (4):  419-431.  DOI: 10.13679/j.jdyj.20210070 Abstract ( 1327 )   PDF (2285KB) ( 1285 )   Multi-year sea ice is a critical component of the Arctic ecosystem and can act as an indicator of Arctic climate change. For instance, the spatial and temporal variability of multi-year ice in the Arctic region can reveal broader regional climatic trends. Based on sea ice age and thickness data from the U.S. National Snow and Ice Data Center (NSIDC), this paper analyzed the temporal and spatial variation characteristics of multi-year Arctic ice extent and age from 2000 to 2019. Ice thickness and volume dynamics between 2011 to 2019 are also assessed. An attribution analysis of multi-year ice variations was then carried out based on the reanalysis data provided by the European Center for Medium-Term Weather Forecasting (ECMWF). The results showed that the majority of Arctic multi-year ice (65.6%) was mainly distributed in the central part of the Arctic. Compared with 2000, the extent of multi-year ice decreased by 1.61×106 km2 in 2019, and the proportion of sea ice, which persists for at least five years or more, decreased by 21%. The fastest reductions occurred in the Chukchi Sea and Beaufort Sea. From 2011 to 2019, the average thickness of multi-year ice was 2.35±0.18 m. The increase of ice thickness and volume fluctuated greatly from year to year during the icing period, and the decrease rate during the melting period was generally faster than the increase rate during the icing period. Among the correlation analysis of various environmental parameters, the 2-m air temperature and sea surface temperature exhibited the strongest significant negative correlations with multi-year ice variations, with the correlation coefficients are –0.78 and –0.77, respectively. In light of continued global warming and “Arctic amplification”, more attention should be paid to the future variations of Arctic sea ice, especially multi-year ice changes with greater thickness and longer retention, which have a major impact on the Arctic ice mass balance. References | Related Articles | Metrics

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The spatial distribution of icebergs around Antarctica from 2015 to 2020 based on remote sensing Zhang Zhuoyu , Liu Lei , Liu Xuying , Qi Mengzhen 2022, 34 (4):  432-440.  DOI: 10.13679/j. jdyj.20210078 Abstract ( 1131 )   PDF (2602KB) ( 1116 )   Icebergs are large pieces of ice produced by the disintegration of ice shelves following crack growth due to the uneven movement speed of each part of ice shelves. The movement and melting of icebergs can transport and subsequently release freshwater to parts of the Southern Ocean that are distant from the Antarctic continent. Accordingly, studying the temporal and spatial distribution of icebergs can provide insights related to the hydrology, ecology, and even the impacts of global climate change across the Southern Ocean. Extracting the iceberg area distribution from remotely sense imagery provides a data basis for such investigations. Using Google Earth Engine, the image dataset of ESA Sentinel-1 SAR images from August 2015 to August 2020 were synthesized. After block resampling, downloading, and splicing, a mosaic map of 400 km around the South Pole within 3 days in winter was obtained; a binary image was then obtained using the grid analysis function, and the area and perimeter of each iceberg was extracted by using data conversion and geometric calculation functions. The results show that many Antarctic icebergs are concentrated within 50 km of the coastline, of which ultra-small icebergs account for nearly 50%. As such, small icebergs may play an important role in the input of fresh water in Antarctica. References | Related Articles | Metrics

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Temporal and spatial variation of Chlorophyll a concentration in Nuup Kangerlua Fjord, Greenland Tian Jiahui, Cheng Xiao, Zhang Yannan 2022, 34 (4):  441-451.  DOI: 10.13679/j.jdyj.20210086 Abstract ( 876 )   PDF (15259KB) ( 479 )   The temporal and spatial distribution of Chlorophyll a (Chl a) concentration in Nuup Kangerlua Fjord is an indicator of climate change. The spatiotemporal distribution of Chl a concentration in this region from 2016 to 2020 was therefore analyzed by combining the Chl a data obtained from Sentinel-3 OLCI inversion by C2RCC algorithm, Operational Sea Surface Temperature and Ice Analysis (OSTIA) sea surface temperature (SST) data, and data from a nearby meteorological station (at Nuuk). The results show that the distribution of Chl a was mainly affected by wind speed, wind direction and SST at the fjord inlet. The peak time of Chl a concentration was about one month later than that of SST and is most widespread when the winds are at their strongest in September. At the outlet of the glacier, in addition to being influenced by wind and water temperature, the spring bloom of Chl a is followed by a second bloom in autumn, driven by meltwater from glaciers. References | Related Articles | Metrics

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Spatial distribution of Antarctic krill and their relationship with chlorophyll concentration in the Amundsen Sea in summer Li Shuai, Yang Jialiang, Zhao Guoqing, Li Lingzhi, Rao Xin, Huang Hongliang 2022, 34 (4):  451-458.  DOI: 10.13679/j.jdyj.20210075 Abstract ( 1061 )   PDF (599KB) ( 1161 )   Antarctic krill (Euphausia superba) are widely distributed in the Southern Ocean. It is a key species in the Southern Ocean ecosystem and an important food source for whales, fish, penguins and birds, and their density and distribution are strongly affected by environmental factors. Based on acoustic evaluation and survey data from the 36th Chinese Antarctic Research Expedition, One-way ANOVA and bivariate correlation analysis were used to study the spatial distribution characteristics and the relationship with chlorophyll concentration of Antarctic krill in the Amundsen Sea from January 9, 2020 to February 5, 2020. The results showed that the average resource density of Antarctic krill in the Amundsen Sea was 6.36 g·m–2, with the highest proportion (68.18%) falling in the density range of 0~5 g·m–2. Spatial variability in Antarctic krill density was statistically significant (P<0.05). Antarctic krill resources were concentrated in the inshore (72.75°S—76.25°S) and western regions (150°W—158°W) of the Amundsen Sea. The average chlorophyll concentration in the study area was 3.54 mg·m–3, with the highest proportion (38.31%) falling in the 2~3 mg·m–3 concentration range. There was also significant spatial variability in chlorophyll concentrations (P<0.05), which were higher in the coastal waters (72.75°S—76.25°S) and on the eastern and western sides (114°W—119°W and 140°W—158°W) of the Amundsen Sea. A significant positive correlation between chlorophyll concentration and the resource density distribution of Antarctic krill was detected (P<0.05). References | Related Articles | Metrics

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Evaluation of Arctic sea ice extent according to Chinese CMIP6 models Zhao Liqing, Wang Xiaochun, Li Jiaqi 2022, 34 (4):  460-470.  DOI: 10.13679/j.jdyj.20210071 Abstract ( 1000 )   PDF (689KB) ( 1061 )   The Coupled Model Intercomparison Project Phase Six (CMIP6) organized by the World Climate Research Project (WCRP) is in progress. Nine earth climate system models from China contribute to CMIP6. The seasonal cycle, long-term linear trend, and intra-annual variability of Arctic sea ice extent (SIE) from the nine models are evaluated by comparing them with observations from 1980 to 2014. The results show that eight models are capable of reproducing the seasonal cycles of Arctic SIE well, except one of nine models in which the maximum value of seasonal cycle is delayed by one month. Most of the models (8/9) overestimate the maximum sea ice extent values of seasonal cycle. In terms of long-term trends, five models overestimate the declining trends of Arctic sea ice in March, and four models underestimate the declining trends of Arctic sea ice in September. Compared with the results of the CMIP6 multi-model ensemble mean, it is found that there is one model for which the seasonal cycle and long-term linear trend of SIE are both within the range of the multi-model ensemble mean’s standard deviation. The difference in long-term September and March SIE trends leads to a significant increasing trend of SIE intra-annual variability as measured by the standard deviation of SIE within a calendar year. Two models can reproduce this feature reasonably well. Finally, it is worth pointing out that four models from the same institution that contributed to both CMIP5 and CMIP6 show improvements in terms of SIE seasonal cycle and its long-term linear trend of annual averaged SIE. References | Related Articles | Metrics

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Comparative analyses of Arctic sea ice monitoring capability of three sea ice concentration products Huang Rui, Wang Changying, Li Jinhua, Sui Yi 2022, 34 (4):  471-484.  DOI: 10.13679/j.jdyj.20210087 Abstract ( 1338 )   PDF (7919KB) ( 735 )   In this paper, three sea ice concentration products are compared: i) data from the Scanning Microwave Radiometer carried on the HY-2B satellite combined with NASA’s TEAM algorithm (“the HY2 dataset”), ii) data from the Microwave Radiometer Imager carried on FY-3D satellite combined with the DT-ASI algorithm provided by Ocean University of China (“the OUC dataset”), and iii) the sea ice concentration product provided by the Ice and Snow Center of the United States (“the NSIDC dataset”). Using the BRM sea ice concentration product with higher spatial resolution and the Moderate Resolution Imaging Spectrometer (MODIS) remote sensing images as reference datasets, we report that: At low latitudes (≤70°N), HY2 is most consistent with. In the mid-latitude region (70°N–80°N), OUC was the most consistent with BRM. At high latitudes (80°N–87°N), the NSIDC dataset is most consistent with the BRM dataset. In the Northeast Passage region, the HY2 dataset is most suitable for sea ice monitoring in the Chukchi Sea and Norwegian Sea segments of the Arctic Northeast Passage during navigation window periods.The NSIDC dataset performs better in each section of the Arctic Northeast Passage near the navigable window period, especially for sea ice monitoring in the East Siberian Sea. The OUC dataset is suitable for the sea ice monitoring needs of most sections of the Arctic Northeast Passage. References | Related Articles | Metrics

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Legal changes and issues related to Northwest Passage navigation following the entry into force of the Polar Code Wang Zelin 2022, 34 (4):  485-493.  DOI: 10.13679/j.jdyj.20210054 Abstract ( 1042 )   PDF (293KB) ( 916 )   Ships navigating in the Northwest Passage should observe Canadian domestic rules and regulations and, since it came force on 1 January 1 2017, the Polar Code. To ensure the safety of ships navigating in Polar waters and prevent environmental pollution caused by ships, the Polar Code stipulates mandatory measures and additional guidance. Canada has subsequently abolished the old regulation and formulated new regulations in line with the provisions of the Polar Code. At the same time, the new Canadian regulations have some specific standards that are more stringent than those in the Polar Code. The Polar Code requires ships navigating the Northwest Passage to meet technical standards and does not resolve problems associated with the mandatory reporting system for certain foreign ships which was stipulated in Canadian domestic law, as well as the application and permission system for foreign vessels entering the Arctic archipelago waters. These problems involve disputes regarding the interpretation of the scope of the authorization of Article 234 of the United Nations Convention on the Law of the Sea, and “historical waters” in the theory and practice of international law. References | Related Articles | Metrics

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Institutional arrangements of economic rights and interests in the Spitsbergen Treaty and Norway’s policies Liu Han 2022, 34 (4):  494-502.  DOI: 10.13679/j.jdyj.20210046 Abstract ( 1059 )   PDF (309KB) ( 1146 )   In 1920, the Spitsbergen Treaty granted the sovereignty of Svalbard to Norway and gave the contracting states the rights to engage in economic activities such as fishing, hunting, and mining in Svalbard. Since the Treaty came into force, the Norwegian government has enacted laws and regulations to strengthen the management of economic activities in Svalbard, gradually nationalized the land and important businesses on the island, promoted the general economic activities of Norwegian companies and citizens, and planned its mainland economic development blueprint of Svalbard. This paper attempts to clarify the institutional arrangement of economic rights and interests of the Spitsbergen Treaty and Norway's associated policies from the three perspectives of history, policy, and practice. It also seeks to provide a useful reference for Chinese citizens to potentially carry out economic activities in Svalbard in the future. References | Related Articles | Metrics

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Legal issues associated with Article IV of the Antarctic Treaty Ma Zhongfa, Xu Ziyun 2022, 34 (4):  503-515.  DOI: 10.13679/j.jdyj.20210067 Abstract ( 1048 )   PDF (335KB) ( 886 )   Article Ⅳof the Antarctic Treaty was successful in setting aside many territorial sovereignty disputes between countries. For 60 years, many countries with disputes over the Antarctic issue have been able to cooperate in science and other fields in the Antarctic without being hindered by sovereign competition. However, many countries have sought more flexible methods to continuously enhance their substantive existence by enhancing scientific research capacity and setting up “quasi territorial jurisdiction” under its “fuzziness”. At the same time, many countries have improved their treaty’s status in global Antarctic governance. Furthermore, they strengthened the soft power of Antarctic governance by promoting Antarctic environmental protection measures, Antarctic legislation, and exploration and development strategies for Antarctic resources. These practices are undoubtedly undermining Article Ⅳ. Therefore, China should take the concepts of “building a community with a shared future for humanity” as the basic concept and direction for China’s participation in Antarctic governance, work to overcome the shortcomings of Article Ⅳ by promoting the establishment of a cooperation mechanism, improve the official domestic translation of Article Ⅳ, and constantly strengthen and improve the domestic legislative system related to Antarctica, strengthen our “hard power” and “soft power” in the global governance of Antarctica, and safeguard our own rights and the rights and interests of all humanity in Antarctica. References | Related Articles | Metrics

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Ultra-high temperature metamorphism in the Prydz Bay region, East Antarctica#br# Biao Xuan Wang Wei Wu Jiang Bao Hong Liu Xiaochun Zhao Yue 2022, 34 (4):  516-529.  DOI: 10.13679/j.jdyj.20210074 Abstract ( 961 )   PDF (2516KB) ( 1105 )   The Prydz Bay region of East Antarctica consists of different terrains including the Vestfold Hills, the Rauer Group, the Larsemann Hills, and Søstrene Island. The Prydz Bay region has undergone high to ultra-high temperature (UHT) metamorphism, with the Rauer Group typically experiencing UHT conditions. Recent studies suggest that UHT metamorphism may occur more widespread, and the Larsemann Hills, Søstrene Island may also have undergone UHT metamorphism. The UHT metamorphism in the Prydz Bay region resulted in various mineral assemblages. The assemblages of orthopyroxene+sillimanite and sapphirine+ quartz can reliably indicate UHT metamorphism in the region. Mineral assemblages including sapphirine (without quartz), spinel-quartz, or corundum may indicate UHT conditions, but whether these mineral assemblages reflect UHT conditions need to be further constrained by reliable thermometry or phase equilibrium modelling based on mineral composition analysis. Different heat sources for UHT metamorphism have been proposed and can be generally classified into two types: autogenic heat and external heat. Autogenic heat mainly includes radioactive heat and mechanical heat, whereas external heat can be provided through conduction and/or convection of a deep heat source. UHT may occur in different tectonic settings including ridge subduction, back-arc basins, and delamination of the lower crust. Previous studies have shown that the Prydz Bay region is a typical orogenic belt with overprinting of different metamorphic events. Recent studies support that UHT metamorphism occurred during the Pan-African period. However, the exact timing, evolutional process, tectonic setting, and heat source of UHT metamorphism are still controversial and thus call for further study. References | Related Articles | Metrics

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Polar ice core-based climate and environmental research: A review and perspective Liu Ke Hou Shugui Pang Hongxi Shi Guitao Geng Lei Hu Huanting Song Jing Zhang Wangbin Zou Xiang An Chunlei Yu Jinhai 2022, 34 (4):  530-545.  DOI: 10.13679/j.jdyj.20210091 Abstract ( 1272 )   PDF (4768KB) ( 1800 )   Ice cores record past changes in precipitation, temperature, volcanic activity, and solar activity, and are therefore good proxies for studying global climate and environmental change. Polar ice cores play are unmatched in their capacity to extend the time scale of high-resolution paleoclimate records hundreds of thousands or even millions of years into the past. In recent years, a series of new research advances have been made in the study of polar ice cores, but there is still a lack of a systematic summary on this topic. In this paper, the latest research progress related to polar ice cores is reviewed. We mainly focus on polar ice cores’ physical properties, stable water isotopes, soluble and insoluble substances, and trapped gases. Finally, possible future directions of polar ice core research that could provide important new insights are discussed. References | Related Articles | Metrics

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Progress in the study of bacterioplankton community structures in the Southern Ocean Sun Yurong Ma Yuxin Cao Shunan Luo Guangfu Lan Musheng He Jianfeng 2022, 34 (4):  546-554.  DOI: 10.13679/j.jdyj.20200079 Abstract ( 1048 )   PDF (328KB) ( 1397 )   Bacterioplankton is an important part of the marine microbial loop, playing a role in maintaining the stability of the marine ecosystem and material circulation. This paper summarizes the community composition of bacterioplankton and its influencing factors in different parts of the Southern Ocean. The results show that the dominant groups are α-proteobacteria, γ-proteobacteria, and Cytophaga-Flexibacter-Bacteroides (CFB), while less abundant groups exhibit strong spatial variability. Temperature and dissolved organic carbon concentrations are two of the main environmental factors that regulate the community structure. There is an obvious interaction between bacterioplankton and other compnents of the microbial food web. Environmental changes such as increasing water temperature and ocean acidification caused by climate change may affect the bacterioplankton community. In the future, research on the bacterioplankton in the pelagic waters, pack ice zone, and deep waters, should be strengthened. In addition, research on seasonal community changes in nearshor waters should be conducted, as should attempts to predict the potential changes and regulation mechanisms of the bacterioplanktonic community in the Southern Ocean via both field investigations and modeling. References | Related Articles | Metrics

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Progress on RINGS Action Group (ice sheet margin), Scientific Committee on Antarctic Research (SCAR) Tang Xueyuan 2022, 34 (4):  555-556.  Abstract ( 817 )   PDF (190KB) ( 888 )   Related Articles | Metrics