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    30 September 2017, Volume 29 Issue 3 Previous Issue    Next Issue

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    Research progress on Antarctic ice sheet grounding line
    Pei Chang, Zhou Chunxia, Lei Haobo
    2017, 29 (3):  305-313.  DOI: 10.13679/j.jdyj.2017.3.305
    Abstract ( 914 )   PDF (5703KB) ( 1194 )  

    Grounding line is the boundary between inland grounded ice sheet and floating ice shelf. The precise
    extraction of its location has a significant impact on the Antarctic ice sheet mass balance. Grounding line
    extraction method has been developed from in situ RES and GPS of small-scale to remote sensing measurements
    of large-scale. Four main techniques of remote sensing measurements, including hydrostatic equilibrium,
    slope analysis, repeated track analysis and differential SAR interferometry, lay the foundation of five
    released grounding line products of the whole Antarctica, named MOA, ASAID, ICESat, MEaSUREs and
    Synthesized grounding line product. With the development of remote sensing technology, multi-source remote
    sensing data will be used for grounding line extraction with high-precision, and its dynamic changes
    monitoring with longer temporal scale in whole Antarctica. Moreover, the change mechanism of the
    grounding line position coupled with bottom melt of ice shelf, bed topography and ocean temperature, and
    building models of its relationship with climate change will be future research hotpots.

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    Advances in paleoenvironmental and sea ice research in the adjacent seas around the Iceland since the last deglaciation
    Wu Yanni, Sha Longbin, Li Dongling, Liu Yanguang, Liang Yuying
    2017, 29 (3):  314-326.  DOI: 10.13679/j.jdyj.2017.3.314
    Abstract ( 690 )   PDF (2283KB) ( 901 )  

    Iceland is one of the most sensitive areas to the global climate changes due to the location in the North Atlantic storm-track path and at the present-day boundary between Polar and Atlantic surface-water masses. Even relatively minor changes in the circulation pattern are likely to be archived in the sedimentary record in this sensitive boundary region. Therefore, further research on the paleoceanography of its adjacent seas is an important component in the study of global climate change. Extensiveness of the sea ice is one of the prominent characters in the area around the Iceland, which plays a significant role in the global climate system. Furthermore, the adjacent seas around the Iceland have widespread tephra layers, which provide dependable chronological data for the study of paleoceanography. In this paper, we firstly reviewed the current studies of paleoenvironment and sea ice changes in the adjacent seas around the Iceland since the last deglaciation, and then discussed the advantages and disadvantages of different paleoceanographic records which are based on diverse proxies in the study area. In addition, the deficiency of different paleoenvironment and sea ice proxies around the Iceland since the last deglaciation were also pointed out in this study. Finally, we prospected the future of paleoclimatic research in the regions around the Iceland in order to fill up the paucity of long-term paleoenvironmental records, like sea ice record.

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    Distribution and seasonal depletion of nutrients in Prydz Bay, Antarctica
    Chen Jiyu, Han Zhengbing, Hu Chuanyu, Sun Weiping, Zhang Haisheng
    2017, 29 (3):  327-337.  DOI: 10.13679/j.jdyj.2017.3.327
    Abstract ( 728 )   PDF (6708KB) ( 898 )  

    Nutrient data collected in Prydz Bay during the CHINARE 25/27/29 cruises were analyzed to study the
    distribution pattern of nutrient concentrations. The consumption, absorption ratio, and structure of nutrients
    (NNU, NPU, and NSiU) in summer were evaluated based on the existence of the Tmin layer. The results
    showed that the spatial distributions of nutrient concentrations in the surface waters of Prydz Bay had obvious
    regional characteristics. The highest, intermediate, and lowest concentrations of nutrients were observed
    in the open sea, continental shelf, and marginal ice shelf areas, respectively. Consumption of nutrients in
    inner areas of Prydz Bay was higher than outer areas partly because of the influence of the phytoplankton
    bloom in austral summer; a period in which nutrients are absorbed by phytoplankton for photosynthesis. The
    NSiU/NNU ratios showed distribution patterns similar to nutrient concentrations but opposite to Chla concentration.
    It is speculated that this difference is mainly due to the higher supply of iron in the continental
    shelf region and inner Prydz Bay area comparted with the open sea. Investigation of the structure and
    changes of nutrient concentrations in Prydz Bay can help us better understand the biogenic element cycle
    processes in the Southern Ocean and provide a basis for predicting the evolution of phytoplankton structure
    in the Southern Ocean.

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    Characteristics of bacterial and protist communities in the summer pack ice zone of Canada Basin, Antarctica
    Zhang Can, He Jianfeng, Huang Tao, Lin Ling, Cao Shunan, Zhang Fang
    2017, 29 (3):  338-348.  DOI: 10.13679/j.jdyj.2017.3.338
    Abstract ( 697 )   PDF (7749KB) ( 461 )  

    During the 6th Chinese Arctic Expedition in August 2014, samples from melting ponds, sea ice, and the
    underlying sea water at seven ice camps in Canada Basin were collected, and the characteristics of the bacterial
    and protist communities were analyzed using epifluorescence microscopy. The results showed the first and
    second dominant groups were bacteria and heteroflagellates, respectively, with biomass percentages of 42.8%,
    37.8%, 50.7%, 40.2%, 34.3%,37.5%, respectively (data from the ICE07 melting pond with an algal bloom were
    not included). Heterotrophic organisms such as bacteria, heteroflagellates, and ciliates dominated within the
    community, suggesting that the microbial loop might play an important role in the community of the pack ice
    zone. Under the background of rapid melting of sea ice in austral summer, the environments of all three habitats
    were unsuitable for rapid growth of the community and the biomass was very low. An autotrophic flagellate
    bloom was observed in a melting pond and within the upper 20 cm of the ice column at ICE07. We suggest that
    suitable quantities of both algal seed and nutrient supplement are essential for the occurrence of algal blooms on
    surface ice.

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    Processing and analyses on shipboard three-component magnetometer data from Prydz Bay, Antarctica
    Wang Wenjian, Gao Jinyao, Wu Zhaocai, Xu Mingju, Wang Wei
    2017, 29 (3):  349-346.  DOI: 10.13679/j.jdyj.2017.1.349
    Abstract ( 645 )   PDF (8367KB) ( 426 )  

    A Shipboard Three-Component Magnetometer (STCM) is easily deployed, unrestricted in its use, and
    capable of multiparameter measurements, which are clear advantages compared with a towed magnetometer
    in harsh polar environments. In this paper, we analyze the influences of a ship’s magnetic field on the STCM
    data acquired during the 29th Chinese Antarctic Research Expedition, and obtain the corrected magnetic
    signature and its corresponding scalar geomagnetic field. Comparison with data acquired from a towed
    magnetometer, there is 47.56 nT of standard deviation for the STCM data, reflecting the tolerable
    performance, reliability, and high quality of data of an STCM in polar regions. This constitutes the first-time
    for Chinese researchers to testify the STCM measurement available in polar seas. Related technical
    refinements will provide effective support for the acquisition of STCM data in upcoming Chinese polar
    expeditions.

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    Recent climate change at the Great Wall and Zhongshan stations in Antarctica and its relationship with the AAO
    Lin Xiang, Bian Lingen
    2017, 29 (3):  357-367.  DOI: 10.13679/j.jdyj.2017.3.357
    Abstract ( 754 )   PDF (8244KB) ( 692 )  

    Climate change in the Antarctic during the recent 15–30 years, the key period of global climate change,
    has been detected in observations acquired at the Great Wall (GW) and Zhongshan (ZS) Stations. Data show
    the Antarctic Peninsula has experienced a cooling trend during the recent 15 years, in conjunction with a
    declining trend in pressure and an increasing trend in precipitation, reflecting some new changes that have
    occurred during the global warming hiatus. Meanwhile, the data from the ZS station show relatively flat
    trends compared with the GW station, implying obvious regional climatic differences between the Antarctic
    Peninsula and the eastern Antarctic continent. Investigation of the correlation between multiple meteorological
    parameters and the Antarctic Oscillation (AAO) indicates significant correlation between the AAO
    and climate at both stations. The different responses to the AAO at the GW and ZS stations might be attributable
    to the regional characteristics of the atmospheric circulation corresponding to the AAO.

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    Comparisons of wind and temperature in Prydz Bay, Antarctica
    Xie Zelin, Wang Zhaomin
    2017, 29 (3):  368-377.  DOI: 10.13679/j.jdyj.2017.3.368
    Abstract ( 732 )   PDF (4357KB) ( 820 )  

    We evaluated the 10-m wind speed, wind direction, and 2-m temperature of the Prydz Bay region (Antarctica)
    using five reanalysis products: the European Centre for Medium-Range Weather Forecasts Interim
    Reanalysis, Japanese 25-year Reanalysis, Japanese 55-year Reanalysis, Climate Forecast System Reanalysis,
    and Modern Era Retrospective-Analysis for Research and Application. The reanalysis products were compared
    with observations acquired by two manual weather stations and three automatic weather stations during 2007.
    Examination of the monthly mean and seasonal differences revealed that reanalysis wind speeds
    were lower than station observations at Mawson but higher at the other stations. Discrepancies in wind direction
    between the observations and the reanalysis datasets were small. The 2-m temperatures of the reanalysis
    datasets were lower than observed at the manual weather stations. There was no consistent characteristic
    in the differences between the 2-m temperatures from the reanalysis datasets and the data from the
    automatic weather stations. We also evaluated 6-hourly data at Mawson. It was found that the reanalysis
    datasets overestimated wind speed at low wind speeds (<5 m/s) and underestimated wind speed at high wind
    speeds (>15 m/s). In addition, the number of strong wind events observed at Mawson was significantly
    higher than indicated by the reanalysis datasets.

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    The inter-annual variation of summer surface water and circumpolar deep water in Prydz Bay, Antarctic
    Wu Chengxiang, Li Bingrui, Zuo Fei, Jia Wang, Li Yuansheng
    2017, 29 (3):  378-389.  DOI: 10.13679/j.jdyj.2017.3.378
    Abstract ( 768 )   PDF (1376KB) ( 1015 )  

    Based on the hydrographic data obtained from four CHINARE (Chinese National Antarctic Research
    Expedition) cruises (27th, 28th, 29th, 31st) in Prydz Bay, we analyze the distribution of water masses, the
    inter-annual variation of SSW (summer surface water) and the formation mechanisms, and the inter-annual
    variation of the upwelling CDW (circumpolar deep water). It is found that SSW has wide ranges of temperature
    and salinity, especially during the cruises of 27th and 29th and higher temperature up to 1.22 ℃ in
    the 27th cruise. Due to less sea ice cover, the area of the SSW during the 29th cruise was much larger. While
    the thickness of the SSW was 50 meters (in the sections of 73°E, 75.5°E and 67.25°S) during the 29th cruise,
    the depth of the SSW during the 31st cruise was 100 meters. The upwelling of CDW is clearly depicted especially
    in the section of 73°E in the cruises of 28th and 29th. It is observed that the CDW upwells to 90 m
    in the cruise of 28th and extends southward to 67.67°S in the 29th cruise. Cyclonic circulation has great effect
    on the transportation of the upwelling of CDW in the bay.

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    Numerical simulations of East Antarctic ice sheet based on the Elmer/Ice model
    Zhang Liangfu, Tang Xueyuan, Yang Shuhu, Xu Shenyuan, Zhang Yun
    2017, 29 (3):  390-398.  DOI: 10.13679/j.jdyj.2017.3.390
    Abstract ( 875 )   PDF (6597KB) ( 1139 )  

    Within the context of global warming, the thickness of the East Antarctic ice sheet has increased according
    to recent observations. However, the lack of observations means it is difficult to perform detailed
    research on the dynamics and thermodynamics of the ice sheet. The section from Dome A to the Zhongshan
    station, which is an important section of the International Trans-Antarctic Scientific Expedition, includes
    many important research sites, e.g., the upstream of the Lambert Glacier, the Gamburtsev Mountains, and
    Dome A. This study used a three-dimensional finite element model to obtain the inland velocity and temperature
    fields of the ice sheet. It was found that the modeled and observational data were identical. The
    bottom temperature of most parts of the ice sheet within this area has reached the pressure melting point. The
    velocity of the inland ice sheet is small. Near the ice shelf, the horizontal velocity increases abruptly, while
    the vertical velocity changes only where the bottom morphology changes rapidly. The prospects for further
    application of the Elmer/Ice model and areas requiring improvement are discussed.

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    Sea ice and weather forecasting information for Arctic sea routes: a synthetic analysis
    Jiang Shan, Yang Qinghua, Liang Yingqi, Teng Junhua, Zhang Lin
    2017, 29 (3):  399-413.  DOI: 10.13679/j.jdyj.2017.3.399
    Abstract ( 672 )   PDF (4978KB) ( 1443 )  

    The reduction in the extent of summer sea ice, associated with global climate change, offers the possibility
    of new sea routes through the Arctic Ocean. Improving the skill of forecasting sea ice and weather
    would strongly support Arctic navigation. Collecting international online information (including observational
    data, forecast products, and historical analysis) of the high Arctic, and analyzing the characteristics of
    sea ice extent and weather forecast information, could support the development of operational Arctic forecasting
    by China. By comparing the information supplied by seven Arctic countries, three non-Arctic countries,
    and three international information suppliers, it was found that sea ice and meteorological forecasting
    capabilities have improved considerably, although further improvements could be made. For example, observational
    data have not been applied fully, the prediction ability in the Central Arctic remains weak, sharing
    of forecast information is insufficient, and comparison is needed when using online information. Furthermore,
    the development of new information technologies is urgently required. To provide improved and
    reliable protection in relation to sea ice and weather for Chinese Arctic expeditions and shipping activities, it
    is strongly suggested that investment in Arctic scientific expeditions be increased, and that international cooperation
    be sought for the development of forecasting technologies in relation to areas affected by Arctic
    sea ice.

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    Research on crash icebreaking pattern recognition of XUE LONG from GPS data
    Gui Dawei, Pang Xiaoping, Shen Quan, Wang Dali, Zhang Jie, Ai Songtao
    2017, 29 (3):  414-419.  DOI: 10.13679/j.jdyj.2017.3.414
    Abstract ( 633 )   PDF (537KB) ( 705 )  

    The XUE LONG is the only icebreaker currently deployed in Chinese polar research. The icebreaking
    status is an important feature of vessels sailing in polar regions. Based on GPS data of the XUE LONG, we
    designed an algorithm to recognize its crash icebreaking status. In the analysis of data obtained during the
    entirety of the Chinese 28th Antarctic Expedition, the recognition rate was >86.1% and the accuracy of recognition
    was >98.0%. Using the developed algorithm to analyze the data obtained during the Chinese 27th
    Antarctic Expedition produced a recognition rate of 85.0%, and accuracy of recognition up to 93.5%. The
    GPS data of these two voyages verified the applicability of the algorithm, and the differences between the
    statistical results showed the different icebreaking states.

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    Study on ice-sheet freeze-thaw detection method in Greenland based on FY-3 data
    Wang Xingdong, Pan Shaohua, Wang Cheng, Li Xinguang
    2017, 29 (3):  420-426.  DOI: 10.13679/j.jdyj.2017.1.420
    Abstract ( 637 )   PDF (1118KB) ( 765 )  

    The Greenland Ice Sheet is of extreme importance in relation to global climate, and the freeze-thaw
    characteristics of the ice sheet reflect Arctic climate change. Using Microwave Radiation Imager (MWRI)
    data acquired by the Chinese FY-3 satellite, the Cross-Polarized Gradient Ratio (XPGR) method is introduced,
    which increases the otherness of dry and wet snow. The Support Vector Machine (SVM) hyperplane,
    which has better detection capability compared with the existing threshold method, is used to detect
    freeze–thaw information on the Greenland Ice Sheet. Comparison of the results with Special Sensor Microwave
    Imager (SSM/I) data (with a threshold of −0.025) showed the proposed method (i.e., XPGR combined
    with SVM) is feasible for the detection of surface freeze–thaw information on the Greenland Ice Sheet.

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