Loading...

Archive

    30 March 2019, Volume 31 Issue 1 Previous Issue    Next Issue

    For Selected: Toggle Thumbnails
    Tectonic and sedimentary characteristics of the Wilkes Land and Terre Adélie continental margin, East Antarctica
    Wang Chunyang, Ding Weiwei, Dong Chongzhi, Fang Yinxia, Zhao Yanghui, Niu Xiongwei
    2019, 31 (1):  1-12.  DOI: 10.13679/j.jdyj.20180032
    Abstract ( 835 )   PDF (11076KB) ( 618 )  

    The continental margin of Wilkes Land and Terre Adélie, East Antactic, occupies a key position for understanding the separation process of Australia and Antarctica in the Late Cretaceous. However, the geology of this area is still poorly understood, especially in the structural-sedimentary evolution. Based on the interpretation of multi-channel seismic profiles across the Wilkes Land and Terre Adélie continental margin, the characteristics of structure and sedimentation in this area are studied. Two regional unconformities are recognized in the seismic profiles, named tur unconformity and eoc unconformity, respectively. Three structural units, rift sequence S3, post-rift sequences S2 and S1, are divided by the two unconformities. The S3 is mostly constituted by syn-rift volcaniclastic rock and fault titled volcanics. On the contrary, hemipelagic turbidity sediments, ooze mud and clay comprise the post-rift sequences S2 and S1. The structural deformation characteristics of different parts of Wilkes Land Terre Adélie continental margin vary dramatically. In western Wilkes Land, S3 was limited and rarely developed in the transition region of slope to deep-sea basin while thick S2 and S1 deposited. In eastern Wilkes Land, thick S3 was deposited and many high angle normal faults developed. The deformation of Terre Adélie was characterized by the development of Adélie Rift Block which was a submarine plateau detached from the continental margin and a major boundary normal fault may developed in the continental side of the block. The differences in structural deformation among the west and east Wilkes Land, Terre Adélie, may due to the heterogeneities of rifting The continental margin of Wilkes Land and Terre Adélie, East Antarctic, occupies a key position for understanding the separation process of Australia and Antarctica in the Late Cretaceous. However, the geology of this area is still poorly understood, especially in the structural-sedimentary evolution. Based on the interpretation of multi-channel seismic profiles across the Wilkes Land and Terre Adélie continental margin, the characteristics of structure and sedimentation in this area were studied. Two regional unconformities were recognized in the seismic profiles, named tur unconformity and eoc unconformity. Three structural units, rift sequence S3 and post-rift sequences S2 and S1, were divided by the two unconformities. The S3 is mostly constituted by syn-rift volcaniclastic rock and fault titled volcanics. Conversely, hemipelagic turbidity sediment, ooze mud, and clay comprise the post-rift sequences S2 and S1. The structural deformation characteristics of the different parts of the Wilkes Land and Terre Adélie continental margin varied dramatically. In western Wilkes Land, S3 was limited and rarely developed in the transition region of the slope to deep-sea basin while thick S2 and S1 were deposited. In eastern Wilkes Land, thick S3 was deposited, and many high angle normal faults developed. The deformation of Terre Adélie was characterized by the development of the Adélie Rift Block, which was a submarine plateau detached from the continental margin. A major boundary normal fault may have developed on the continental side of the block. The differences in structural deformation between the west and east Wilkes Land and Terre Adélie might attribute to the heterogeneities of rifting resulting from the anticlockwise rotation of the Australia plate during the separation with the Antarctic. On the seismic profiles, basement ridges in the COT(Continent-Ocean Transition) area were clearly recognized. These basement ridges may be serpentinized peridotite formed by mantle intrusion in the crust extension area, which resulted in the magnetic anomaly in the COT.which results from the anticlockwise rotation of Australia plate during the separation with Antarctic. In the seismic profiles, basement ridges in the COT area were clearly recognized. These basement ridges may be the serpentinized peridotite formed by the mantle intrusion in the most crust extension area, which resulted in the magnetic anomaly in the COT.

    Related Articles | Metrics
    Radiosonde observations at the southwest continent and analysis of atmospheric vertical structure characteristics of the Antarctic  
    Liu Kai, Wei Lixin, Chen Zhikun, Chen Jianqiao, Chai Xiaofeng
    2019, 31 (1):  13-24.  DOI: 10.13679/j.jdyj.20180003
    Abstract ( 790 )   PDF (1241KB) ( 1068 )  

    Based on the 33rd Antarctica expedition radiosonde data collected at the Great Wall and Feri stations, the vertical structure characteristics of the atmosphere in the summer and the variations of tropopause height under different synoptic systems around the Great Wall station were analyzed with reanalysis data and radiosonde data from eight World Meteorological Orgation stations. The results show that the height of the lapse rate tropopause at the Great Wall station was 8 500 m and the height of cold point tropopause was 9 000 m. The tropopause temperature was approximately –50℃ and the mean wind velocity of the tropopause was 21 m·s–1. The mid-troposphere lapse rate was –6.34℃·km–1. The height of the boundary layer was 600 m and its mean wind velocity was 10 m·s–1. The tropopause height and vertical lapse rate at the Great Wall station varied considerably under different synoptic systems. When the east side of the Antarctic Peninsula is controlled by a cyclone or polar anticyclone, the Antarctic Great Wall station is affected by the cold dry southerly airstream. The development of convection is inhibited, leading to a low tropopause height and small vertical atmospheric lapse rate; the opposite is also true. Comparison with the WMO station data found that the tropopause height of the southeast continent is higher than that of the southwest. The height of the South Pole is the lowest, which may be closely related to the development source of a circumpolar cyclone. For the variation trend of the tropopause on a large scale, the reanalysis data (NCEP and ERA-interim) are reliable. However, on a synoptic scale, the NCEP data has a better performance than ERA-interim data compared with the radiosonde data results.

    Related Articles | Metrics
     
    Community structure of picoeukaryotes in the Chukchi Sea and their relationship with environmental factors
    Wu Yue, Cao Shunan, He Jianfeng, He Peimin, Luo Guangfu, Lan Musheng
    2019, 31 (1):  25-33.  DOI: 10.13679/j.jdyj.20180012
    Abstract ( 718 )   PDF (6521KB) ( 984 )  

    Field measurements and samplings were conducted during the 5th Chinese National Arctic Research Expedition in Summer 2012. Pyrosequencing was used to study the picoeukaryote community structure and correlation analysis was conducted to reveal the relationship between picoeukaryotes and environmental factors in the Chukchi Sea. The results show that Mamiellophyceae (37.5%), Chrysophyceae (36.4%), Dinophyceae (8.9%), Tremellomycetes (7.1%), Mediophyceae (2.4%), and Spirotrichea (1.1%) are the dominant groups at the class level. Picophytoplankton accounted for 85.2% of the picoeukaryotes in the Chukchi Sea, which indicates that the community was at the stage of rapid growth. Spearman analysis shows that environmental factors play an important role in the community structure of picophytoplankton. Mediophyceae had a very significant positive correlation with NO3– (P < 0.01) and a significant positive correlation with salinity and NO2– (P < 0.05). NO3– had a significant negative influence on Mamiellophyceae (P < 0.05). The results suggest that the nitrogen limitation of the Arctic Ocean and the rapidly melting sea ice affect the structure and spatial distribution of picoeukaryotes and that further attention is needed in the future.

    Related Articles | Metrics
    Distributions and influence factors of dissolved N2O in the Kongsfjorden and Bayelva River in Ny-Ålesund, Arctic
    Gu Xueji, Zhang Guiling, Zhu Zhuoyi, Zhang Ruifeng, Jin Jie, Zhang Guosen
    2019, 31 (1):  34-44.  DOI: 10.13679/j.jdyj.20180013
    Abstract ( 810 )   PDF (5346KB) ( 864 )  

    Distributions and saturations of nitrous oxide (N2O) were investigated in the Kongsfjorden and Bayelva River of the Svalbard islands in August 2013 and 2015. The concentrations of dissolved N2O in the surface water of the Kongsfjorden ranged from 10.95 to 13.32 nmol·L–1 with an average of (12.47 ± 0.71) nmol·L–1 in August 2013. In August 2015, the concentrations ranged from 11.40 to 13.07 nmol·L–1 with an average of (12.39 ± 0.53) nmol·L–1. Dissolved N2O concentrations in the surface waters of the Bayelva River ranged from 10.66 to 16.83 nmol·L–1 with an average of (14.65 ± 1.54) nmol·L–1 in August 2013. In August 2015, the concentrations ranged from 9.38 to 15.45 nmol·L–1 with an average of (12.99 ± 1.98) nmol·L–1. The warm and saline Atlantic water flow was thought to be the dominant factor in the N2O distributions in northwestern Kongsfjorden, while the N2O distributions in southeastern Kongsfjorden were mainly regulated by glacier meltwater. Meanwhile, sediment N2O produced through denitrification might be an important contributor to the accumulation of N2O in the Kongsfjorden. Negative correlations were found between the ΔN2O and apparent oxygen utilization (AOU), indicating that biological activities had limited contributions to the N2O production and consumption in the Kongsfjorden. N2O in the glacier meltwater of Ny-Ålesund was undersaturated (78%) in August 2013. N2O saturations in the Bayelva River increased from the upper stream to the estuary because of the water-air exchange and temperature. The N2O undersaturation in the Kongsfjorden was the result of dilution by sea ice meltwater. N2O saturations in the surface waters of the Kongsfjorden ranged from 77% to 98% with an average of (89 ± 6)% in August 2013 and from 90% to 101% with an average of (95 ± 4)% in August 2015. Furthermore, other factors including temperature had an effect on the saturation of N2O in the different water bodies of Ny-Ålesund. Because of the undersaturation of dissolved N2O, the Kongsfjorden and Bayelva River were sinks for atmospheric N2O.

    Related Articles | Metrics
    Distribution and prediction of dimethyl sulfur sea-air flux in south Australian
    Jiang Limei, Qu Bo
    2019, 31 (1):  45-55.  DOI: 10.13679/j.jdyj.20180018
    Abstract ( 695 )   PDF (1050KB) ( 694 )  

    The sea-to-air flux of marine biological dimethylsulfuide (DMS) can have an effect on cloud condensation and regional solar radiation, hence reducing the global surface temperature. Meanwhile, the DMS flux influence on climate cooling is more obvious because of a large quantity of melting ice in the polar region. This paper studied the distributions and annual variations of wind speed (WIND), cloud cover (CLOUD), sea surface temperatures (SST), chlorophyll (CHL), and mixed layer depth (MLD) in the Subantarctic nearly ice-free region (South Australia) (40°S—60°S, 110°E—140°E) for the years 2012—2014. A genetic algorithm technique was used to calibrate the main parameters in the DMS model. Simulation and analysis of the sea-air flux was also conducted. Finally, we used the CMIP5 (5th Coupled Model Intercomparison Project) to predict changes in the DMS flux for 4×CO2 (year 2100), compared with 1×CO2 (the contemporary case for the years 2012—2014). The results show that the increased rates of 4×CO2 for SST, CLOUD, and WIND were 0.9, 5.6, and 12.3%, respectively. However, the MLD reduced rate was 41.0% and the increased rate of transfer velocity (kw) was 58.8%. Because of the distinction of the melting ice, the DMS flux increased by only 9.4%. Therefore, the increased rate of the DMS flux is far less than the Polar Regions. The research results show that DMS has less effect on the greenhouse conditions in the Subantarctic nearly ice-free region (South Australia).

    Related Articles | Metrics
    Numerical simulation of barotropic tide in the Bransfield Strait, Antarctica
    Zhou Xiangqian, Hu Song, Zhang Yu
    2019, 31 (1):  56-68.  DOI: 10.13679/j.jdyj.20180023
    Abstract ( 737 )   PDF (8738KB) ( 484 )  

    In this paper, the high resolution finite volume community ocean model (FVCOM) was used to simulate the four main tides of M2, S2, K1, and O1 in the Bransfield Strait, Antarctica. The co-tide chart was plotted using the tide harmonic constant. Using these data, the tidal form was calculated, which in this sea area is a mixed semi-diurnal tide. The diurnal tide in this area near the southwestern part of the Antarctic Peninsula was greater than that of the northeast around the South Shetland Island. By calculating the four dominant tidal fluxes respectively, we found that the tidal fluxes of M2 were from the Pacific Ocean and Weddell Sea. The tidal fluxes of S2, K1, and O1 were from the Atlantic Ocean and Weddell Sea. In the Bransfield Strait area, there was 90.6 MW of total dissipated energy for the four tides, with the largest tidal dissipation occurring in O1, accounting for approximately 49.09% of the total tidal energy dissipated. Before the Weddell tidal energy fluxes entered the Bransfield Strait, Antarctica, the four tides dissipated a total of 278.87 MW. The S2 sub-tidal accounted for approximately 39.09% of the total energy dissipation.

    Related Articles | Metrics
    Investigation of Arctic first-year and multi-year sea ice based on OSI-SAF microwave remote sensing data
    Man Fukang, Xia Wentao, Zhang Jie, Ke Changqing
    2019, 31 (1):  69-83.  DOI: 10.13679/j.jdyj.20180033
    Abstract ( 997 )   PDF (7516KB) ( 703 )  

    Based on the OSI-SAF daily Arctic sea ice type and concentration data from October 2005 to April 2017, the spatial-temporal characteristics of the changes in first-year ice (FYI) and multi-year ice (MYI) in the Arctic were analyzed. A result of this research was that the multi-year mean sea ice growth rate of FYI was faster during October to December of each growth period, with a mean rate of 1.87?106 and 1.77?106 km2·month–1, for sea ice extent and area, respectively. The growth rate was slower from January to March of each growth period, with a mean growth rate of 0.50?106 and 0.43?106 km2·month-1, respectively. The FYI decreased from March to April, with a mean rate of –0.38?106 and –0.24?106 km2·month-1, respectively. The extent/area of the MYI varied during the different growth periods, with no identical pattern observed in the MYI extent/area time series. The variation characteristics of the sea ice extent in eight sea areas were different, and the Arctic Ocean core region played a leading role in the change in the Arctic MYI. During the growth period, the FYI grew to the south of the Arctic Ocean, and the MYI was mostly distributed in the center of the Arctic. The overall sea ice extent in October and November had significant negative correlations (significance level at 0.05) with the average Arctic air temperature of the last six months. The FYI extent in March and April also had significant negative correlations with the average temperature of the last six months (significance level at 0.05). There were no significant correlations between the MYI extent and monthly mean air temperature in the Arctic.

    Related Articles | Metrics
    Dynamic simulation of process risk on ship navigation at the Arctic Northeast Route
    Hu Shenping, Xuan Shaoyong, Liu Yu, Fu Shanshan, Xi Yongtao
    2019, 31 (1):  84-93.  DOI: 10.13679/j.jdyj.20180025
    Abstract ( 827 )   PDF (3810KB) ( 1280 )  

    In recent years, with the opening and successful navigation of the Arctic ice waterway, the safety of ship navigation in polar waters has been highly valued. Because there are many variable factors affecting the safety of ship traffic in the ice area, it is necessary to analyze the process risk for en-route navigation in the Arctic ice waterway. Combining the characteristics of maritime traffic risks, the effects of special attributes, such as low temperature, ice drift, and high latitude, were evaluated on the navigation safety of ships. The navigation risk on the Northeast Route in the Arctic was analyzed and then the navigational risk transition model for ships in the Arctic northeast route was constructed. The Markov process theory was introduced to establish a cloud simulation model based on the Markov Chain Monte Carlo (MCMC) Algorithm, thereby simulating the risk of ship navigation in the Arctic with continuous time. This study indicates that during the summer season, the risk of navigation in the northeastern route of the Arctic is as low as reasonably navigable. The risk level continuously changes with time, showing an overall M-type curve trend, with significant risk fluctuations.

    Related Articles | Metrics
    A feasibility study on navigation in a key sea area of the Northeast Passage of the Arctic based on the Dynamic Bayesian Network
    Shan Yulong, Zhang Ren, Li Ming
    2019, 31 (1):  94-102.  DOI: 10.13679/j.jdyj.20180021
    Abstract ( 923 )   PDF (1616KB) ( 1210 )  

    Continued climate change has led to the melting of polar ice and the opening of the Arctic passage. Because of the uncertainty of navigability in a key sea through Arctic Northeast Passage and the typical time series nature of the statistical data, the assessment and forecasting technology for the risk affecting the navigability of the Northeast Passage based on Dynamic Bayesian Network is proposed. Through determination of the key sea and index; construction of the structure and parameter learning of the Bayesian Network; reasoning and computation based on evidence; and testing of the superiority of Dynamic Bayesian Network, a risk assessment and forecasting model based on Dynamic Bayesian Network is established. The results show that the Dynamic Bayesian Network technology can not only deal with the dynamic data but can also reduce the effect of inaccurate data on the results. The Dynamic Bayesian Network is superior to the traditional evaluation technology, and the predicted results of the model are more accurate in the short term. This result has an important significance for judging the navigability of the Arctic Northeast Passage.

    Related Articles | Metrics
    Evaluation and reflection of CCAMLR measures for regulation of IUU fishing
    Wu Ningbo
    2019, 31 (1):  103-113.  DOI: 10.13679/j.jdyj.20180024
    Abstract ( 863 )   PDF (390KB) ( 1192 )  

    Since the 1980s, rampant illegal, unreported, and unregulated (IUU) fishing has led to the exhaustion of marine living resources in the Southern Ocean. As the most important regional fishery management organization in the Southern Ocean, the Commission on the Conservation of Antarctic Marine Living Resources (CCAMLR) has issued conservation measures for the marine living resources. The measures have had a good effect among contracting parties. However, there is no doubt that the existing inherent limitations in the flag state jurisdiction regulations of international marine law have given rise to uninhibited IUU fishing from vessels associated with non-contracting parties in the Convention area. At this stage, these limitations have been the greatest challenge for managing the Antarctic marine living resources.

    Related Articles | Metrics
    Briefing of 9th Chinese National Arctic Research Expedition
    Lei Ruibo
    2019, 31 (1):  114-116. 
    Abstract ( 616 )   PDF (219KB) ( 1271 )  
    Related Articles | Metrics