Features of visibility variation at Great Wall Station, Antarctica

The variation of visibility at Great Wall Station （GWS） was analyzed using manual observational data for the period of 1986 to 2012. Results show that the frequencies of occurrence of high （≥ 10 km） and low visibility （0-1 km） are 61.0% and 8.0%, respectively. Visibility at GWS shows an evident seasonal variation： The highest visibility between November and March, and the lowest visibility from June to October. Sea fog and precipitation are the main factors for low visibility during summer, whereas frequent adverse weather, such as falling snow, blowing snow, or blizzards, are responsible for low visibility in winter. The frequency of occurrence of low visibility has decreased significantly from 1986 to 2012. Conversely, the frequency of occurrence of high visibility has shown a significant increasing trend, especially during winter. The decreasing tendencies of fog, blowing snow, and snowfall have contributed to the increasing trend of high visibility during winter. Visibility at GWS exhibits significant synoptic-scale （2.1 to 8.3 d）, annual, and inter-annual periods （2 a, 4.1 a, and 6.9 a to 8.2 a）, among which the most significant period is 4.1 a. The visibility observed during 2012 indicates that instrumental observation can be applied in the continuous monitoring of visibility at GWS.     

The distribution and concentration of particulate biogenic silica in surface waters of Prydz Bay, Antarctica, during the austral summer of 2011

The concentrations and distributions of particulate biogenic silica （PBSi） in the upper surface waters of Prydz Bay, Antarctica, were investigated during the 27th Chinese National Antarctic Research Expedition cruises of January 2011. We aimed to characterize the correlations between PBSi and plankton, nutrients and particulate organic carbon. The results showed that the concentrations of biogenic silica ranged from 0.76--19.72 ktmol-dm3 and the average concentration of biogenic silica was 6.06 mol.dm3. The distribution of surface PBSi had significant regional characteristics： The concentrations were higher south of 67S than to the north. The distribution of PBSi, chlorophyll a and particulate organic carbon showed similar patterns, and PBSi distribution had a negative correlation with that of silicate. In the vertical direction, the mole ratio of PBSi and POC （Si/Co） decreased with increasing depth. This trend indicated a higher rate of PBSi dissolution, or a lower rate of organic matter reminer- alization rate, in the upper 200 m.     

VHF meteor radar at King Sejong Station,Antarctica

Since 2002, we have been observing the mesosphere and lower thermosphere （MLT） region over King Sejong Station （KSS; 62.22°S, 58.78°W）, Antarctica, using various instruments such as the Spectral Airglow Temperature Imager （SATI）, All Sky Camera （ASC） and VHF meteor radar. The meteor radar, installed in March 2007, continuously measures neutral winds in the alti- tude region 70-110 km and neutral temperature near the mesopause 24 h.d-1, regardless of weather conditions. In this study, we present results of an analysis of the neutral wind data for gravity wave activity over the tip of the Antarctic Peninsula, where such activity is known to be very high. Also presented is temperature estimation from measurement of the decay times of meteor trails, which is compared with other temperature measurements from SATI and the Sounding of the Atmosphere using Broadband Emis- sion Radiometry （SABER） instrument onboard the Thermosphere Ionosphere Mesosphere Energy and Dynamics （TIMED） satel- lite.     

Phytoplankton community changes indicated by biomarker from sediment in Prydz Bay, Antarctica

Biomarkers including brassicasterol, dinosterol and alkenone in sediments are used as indicators to reconstruct changes to the phytoplankton community in surface and sub-aerial sediments of Prydz Bay, Antarctica. The results indicate that the bio- marker records in surface and core sediment samples changed with time and space. The total content of phytoplankton biomarkers ranges from 391.0--1 470.6 ng.g-l. The phytoplankton biomass has increased in Prydz Bay over the past 100 years. This variation may be mainly related with climate change in the region. The total biomarker contents in surface sediments from 5 stations in Prydz Bay are in the range of 215.8--1 294.3 ng.g4. The phytoplankton biomass in Prydz Bay is higher than that outside of the bay. This is similar to the distributions of chlorophyll a, organic carbon and biogenic silica in surface waters determined through in situ investigation. Such consistency indicates a coupling between the bottom of the ocean and biogeochemical processes in the upper water.     

Progress and prospects in Chinese Antarctic surveying, mapping and remote sensing studies

Antarctic surveying, mapping and remote sensing is one of the important aspects of the Chinese Antarctic geoscience research program that stretch back over 25 years, since the first Chinese National Antarctic Research Expedition （CHINARE） in 1984. During the 1980＇s, the geodetic datum, height system and absolute gravity datum were established at the Great Wall and Zhongshan Stations. Significant contributions have been made by the construction of the Chinese Great Wall, Zhongshan and Kunlun Stations in Antarctica. Geodetic control and gravity networks were established in the King George Islands, Grove Moun- tains and Dome Argus. An area of more than 200 000 km2 has been mapped using satellite image data, aerial photogrammetry and in situ data. Permanent GPS stations and tide gauges have been established at both the Great Wall and Zhongshan Stations. Studies involving plate motion, precise satellite orbit determination, the gravity field, sea level change, and various GPS applications for atmospheric studies have been carried out. Based on remote sensing techniques, studies have been undertaken on ice sheet and glacier movements, the distributions of blue ice and ice crevasses, and ice mass balance. Polar digital and visual mapping tech- niques have been introduced, and a polar survey space database has been built. The Chinese polar scientific expedition manage- ment information system and Chinese PANDA plan display platform were developed, which provides technical support for Chi- nese polar management. Finally, this paper examines prospects for future Chinese Antarctic surveying, mapping and remote sens- ing.     

Source and spatial distributions of particulate organic carbon and its isotope in surface waters of Prydz Bay,Antarctica, during summer

In this study, we investigated the distributions of sea-surface suspended particulate organic carbon （POC） and its stable isotope （δ13C POC） in Prydz Bay, Antarctica, and examined the factors influencing their distribution, sources, and transport. We used measurements collected from 61 stations in Prydz Bay during the 29th Chinese National Antarctic Research Expedition, in combination with remote sensing data on sea surface temperature （SST）, chlorophyll a concentration, and sea ice coverage. The POC concentration in the surface waters of Prydz Bay was 0.28-0.84 mg.L-1, with an average concentration of 0.48 mg.L-1. The δ13C POC value ranged from -29.68‰ to -26.30‰, with an average of-28.01‰. The concentration of suspended POC was highest in near-shore areas and in western Prydz Bay. The POC concentration was correlated with chlorophyll a concentration and sea ice coverage, suggesting that POC was associated with phytoplankton production in local water columns, while the growth of phytoplankton was obviously affected by sea ice coverage. The δ13C poc value in suspended particles decreased gradually towards the outer waters of Prydz Bay, while in eastern Prydz Bay the δ13Cpoc value become gradually more negative from nearshore to deep-water areas, suggesting that δ13C poc was mainly influenced by CO2 fixation by phytoplankton. The δ13C POC value in suspended particles near Zhongshan Station was significantly negative, possibly as a result of the input of terrigenous organic matter and changes in the phytoplankton species composition in the nearshore area.     

Pollen morphology of selected tundra plants from the high Arctic of Ny-(A)lesund, Svalbard

Documenting morphological features of modem pollen is fundamental for the identification of fossil pollen, which will assist researchers to reconstruct the vegetation and climate of a particular geologic period. This paper presents the pollen morphol- ogy of 20 species of tundra plants from the high Arctic of Ny-Alesund, Svalbard, using light and scanning electron microscopy. The plants used in this study belong to 12 families： Brassicaceae, Caryophyllaceae, Cyperaceae, Ericaceae, Juncaceae, Papav- eraceae, Poaceae, Polygonaceae, Ranunculaceae, Rosaceae, Salicaceae, and Scrophulariaceae. Pollen grain shapes included： spher- oidal, subprolate, and prolate. Variable apertural patterns ranged from 2-syncolpate, 3-colpate, 3-（-4）-colpate, 3-（-5）-colpate, 3-colporate, 5-poroid, ulcerate, ulcus to pantoporate. Exine ornamentations comprised psilate, striate-perforate, reticulate, mi- croechinate, microechinate-perforate, scabrate, granulate, and granulate-perforate. This study provided a useful reference for com- parative studies of fossil pollen and for the reconstruction of paleovegetation and paleoclimate in Svalbard region of Arctic.     

GPR Surveying in the kernel area of Grove Mountains,Antarctica

The Grove Mountains, located between the Zhongshan Station and Dome A, are a very important area in inland Antarctic research. China has organized five investigations of the Grove Mountains, encompassing the geological structure, ancient climate, meteorites, ice-movement monitoring, basic mapping, meteorological observations, and other multi-disciplinary observational studies. During the 26th Chinese National Antarctic Research Expedition in 2010, the Grove Mountains investigation team applied specialized ground-penetrating radar(GPR) to survey subglacial topography in the eastern kernel area of the Grove Mountains. In this paper, we processed GPS and GPR data gathered in the field and drew, for the first time, two subglacial topographic maps of the Grove Mountains kernel area using professional graphics software. The preliminary results reveal the mystery of the nunatak landform of this area, give an exploratory sense of the real bedrock landforms, and indicate a possible sedimentary basin under the Pliocene epoch fossil ice in the Grove Mountains area. Additionally, it has been proven from cross-sectional analysis between Mount Harding and the Zakharoff ridge that the box-valley shape between two nunataks has already matured. ′     

Factors influencing small-scale distribution of 10 macrolichens in King George Island,West Antarctica

Lichens are among the main primary colonists in most terrestrial ecosystems of Antarctica, where the effects of environmental factors on spatial distribution of lichens are essential to understanding the functioning of Antarctic terrestrial ecosystems. We measured abundance of 10 frequently observed macrolichens and 15 environmental factors at a small scale （20 cm× 20 cm）, in the ice-free areas of Fildes Peninsula and Ardley Island, King George Island, West Antarctica, and assessed the effects of environmental factors on the local distribution of these lichens. Canonical correspondence analyses （CCA） show that 8 out of 15 environmental factors, belonging to 4 sets of variables, are important in spatial distribution of the 10 lichens. Variation partitioning analyses show that most of the variation in distribution of the 10 lichens is described by the spatial heterogeneity of substrate, bird influence and microclimate and topography, whereas human impact has no significant effects.     

Hydrochemistry and sediment characteristics of polar periglacial lacustrine environments on Fisher Island and Broknes Peninsula,East Antarctica

Fisher Island and Broknes Peninsula in the Larsemann Hills constitute part of a polar lowland periglacial environment between marine and glacial ecosystems. The landscape is characterized by gently rolling hills and broad valleys interspersed with lakes formed in glacially scoured basins. We analyzed the physieochemical parameters and the ionic constituents of water samples from 10 lakes in each of these two locations. Our results showed considerable differences between the two regions and demon- strated the influence of lithology and processes including weathering, evaporation, and atmospheric precipitation. All major cations and anions in the lake waters showed positive correlations indicating balanced ionic concentrations. Unconsolidated sediments were sparsely distributed and scattered over glacial deposits, valley fills, and occasional moraine ridges. The type and rate of sedi- mentation was mainly controlled by surface run-off and aeolian influx. The sediment samples from lake beds and the catchment area on Fisher Island were immature and poorly to very poorly sorted, consisting of gravelly sand with negligible silt and finer fractions. Sediments had a polymodal grain size distribution with the two major populations lying between -2 and 1 phi and be- tween 0 and 1.5 phi. The sediments were lithic arenite to arkosic in composition and the microtextures imprinted over quartz grains were dominated by mechanical textures resulting from several stages of glacial crushing and grinding. The presence of deep disso- lution cavities, cryptocrystalline precipitation, and euhedral crystal growth signified the effect of chemical activity after the deposition of grains in the lacustrine environment.     

Thermodynamic properties of snow cover on sea ice during the austral summer in Prydz Bay,East Antarctica

The thermodynamic properties of snow cover on sea ice play a key role in the ice-ocean-atmosphere system and have been a focus of recent scientific research. In this study, we investigated the thermodynamic properties of snow cover on sea ice in the Nella Fjord, Prydz Bay, East Antarctica(69°20′S, 76°07′E), near the Chinese Antarctic Zhongshan Station. Our observations were carried out during the 29th Chinese National Antarctic Research Expedition. We found that the vertical temperature profile of snow cover changed considerably in response to changes in air temperature and solar radiation during the summer. Associated with the changes in the temperature profile were fluctuations in the temperature gradient within the upper 10 cm of the snow cover. Results of previous research have shown that the thermal conductivity of snow is strongly correlated with snow density. To calculate the thermal conductivity in this study, we measured densities in three snow pits. The calculated thermal conductivity ranged from 0.258–0.569 W?m-1?K-1. We present these datasets to show how involved parameters changed, and to contribute to a better understanding of melting processes in the snow cover on sea ice.     

Concentrations and distribution of biogenic barium in surface sediments of Prydz Bay, Antarctica

Concentrations ofbiogenic barium were investigated in surface sediments of Prydz Bay, Antarctica, during the 21st and 27th CHINARE cruises. Factors controlling the observed distribution are explored. Biogenic barium concentrations obtained from a sequential extraction procedure are compared with total concentrations obtained from the normative calculation based on a total digestion, and differences in the results are examined. Concentrations of biogenic barium, calculated by the normative calculation, were much higher than the concentrations obtained through sequential extraction; this discrepancy is the result of the occurrence of barium associated with Mn/Fe oxides, which represents an important component of total barium in these sediments. Concentrations of biogenic barium obtained from the sequential extraction range from 104 to 445 ktg.g1, and the average concentration was 227 p.g.g-~. The highest concentrations of biogenic barium occur in the central area of the bay, where the seawater is more stable, while lower values occur in the bank and the ice shelf. Biogenic barium is significantly linearly correlated with biogenic barium and organic carbon, and similar in distribution of Chl a, which may indicate that primary productivity of phytoplankton in the surface water column is the main environmental factor regulating barium concentration and distribution.     

Diversity and bioactivity of actinomycetes from Signy Is- land terrestrial soils,maritime Antarctic

The Antarctic represents a largely untapped source for isolation of new microorganisms with potential to produce bio- active natural products. Actinomycetes are of special interest among such microorganisms as they are known to produce a large number of natural products, many of which have clinical, pharmaceutical or agricultural applications. We isolated, characterized and classified actinomycetes from soil samples collected from different locations on Signy Island, South Orkney Islands, in the maritime Antarctic. A total of 95 putative actinomyeete strains were isolated from eight soil samples using eight types of selective isolation media. The strains were dereplicated into 16 groups based on morphology and Amplified Ribosomal DNA Restriction Analysis （ARDRA） patterns. Analysis of 16S rRNA gene sequences of representatives from each group showed that streptomy- cetes were the dominant actinomycetes isolated from these soils; however, there were also several strains belonging to diverse and rare genera in the class Actinobacteria, including Demetria, Glaciibacter, Kocuria, Marmoricola, Nakamurella and Tsukamurella. In addition, screening for antibacterial activity and non-ribosomal peptide synthetase genes showed that many of the actinomycete strains have the potential to produce antibacterial compounds.     

Population distribution,structure and growth condition of Antarctic krill （Euphausia superba Dana） during the austral summer in the Southern Ocean

Antarctic krill （Euphausia superba Dana） was collected using a High Speed Collector and an Isaac-Kidd midwater trawl （IKMT） net during the austral summer of 2007/2008 and 2008/2009 in the circumpolar and Prydz Bay regions of the Southern Ocean, respectively. Combined with the simultaneous recording of environmental factors, spatial distribution, population structure and growth condition of E. superba were studied. The abundance of E. superba in the Weddell Sea was higher than in Prydz Bay. However, the abundance of E. superba in both the Weddell Sea and Prydz Bay was lower than figures reported in previous krill surveys for the same time period. With respect to the total study area, E. superba displayed a normal growing state during the two expeditions. E. superba grew relatively poorly in some stations, which may be due to the late retreat of sea ice or lower chlorophyll a concentrations. The number of juvenile E. superba collected using the High Speed Collector was proportionally greater in stations located at the edge of the sea ice, while adults dominated in long-term non-ice regions. This phenomenon reflects the different distribution pattern between juvenile and adult krill. The population structure of E. superba differed between sea regions, which may affect recruitment.     

The composition and origination of particles from surface water in the Chukchi Sea,Arctic Ocean

Suspended particle samples were collected at 11 stations on the shelf and slope regions of the Chukchi Sea and the central Arctic Ocean during the fifth Chinese National Arctic Research Expedition （summer 2012）. The particle concentration, total organic carbon （TOC）, total nitrogen （TN） and the isotopic composition of the samples were analyzed. The suspended particle concentration varied between 0.56 and 4.01 mg.Ll; the samples collected from the sea ice margin have higher concentrations. The organic matter content is higher in the shelf area （TOC： 9.78%-20.24%; TN： 0.91‰-2.31%）, and exhibits heavier isotopic compositions （δ13C： -23.29‰ to -26.33‰ PDB; δ15N： 6.14‰-7.78‰）, indicating that the organic matter is mostly marine in origin with some terrigenous input. In the slope and the central Arctic Ocean, the organic matter content is lower （TOC： 8.06%- 8.96%; TN： 0.46%-0.72%）, except for one sample （SR15）, and has lighter isotopic compositions （δ13C： -26.93‰ to -27.78‰ PDB; δ15N： 4.13‰-4.84‰）. This indicates that the organic matter is mostly terrestrially-derived in these regions. The extremely high amount of terrigenous organic matter （TOC： 27.94%; TN： 1.16%; δ13C： -27.43‰ PDB; δ15N： 3.81‰） implies that it was carried by transpolar currents from the East Siberian Sea. Material, including sea ice algae, carried by sea ice are the primary source for particles in the sea ice margins. Sea ice melting released a substantial amount of biomass into the shelf, but a large amount of detrital and clay minerals in the slope and the central Arctic Ocean.     

Multiple processes affecting surface seawater N20 satura- tion anomalies in tropical oceans and Prydz Bay, Antarc- tica

Abstract We analyzed the N20 content of surface seawater sampled from Prydz Bay, Antarctica, on a cruise track between 30°S and 30°N during the twenty-second Chinese National Antarctic Research Expedition during austral summer, 2006. The surface water showed an average pN20 value of 311.9a：7.6 nL.L-1 （14.1：t：0.4 nmol-Ll）, which was slightly undersaturated. The air-sea N2O flux in the region was -0.3±0.8 p.mol.mE,dl; howeveh N20 in the surface water was oversaturated in most stations along the cruise track. Saturation anomalies were greater than 10%, with a maximum of 54.7% being observed at the Eqaator, followed by 31% at 10°N in the Sulu Sea. The air-sea fluxes at these locations were 12.4 and 4 μmol-mLd-1, respectively. Overall, the results indicated that surface water in Prydz Bay was near equilibrium with atmospheric N20, and that ocean waters in lower latitudes acted as a N20 source. Physical processes such as stratification, ice-melt water dilution, and solar radiation dominate the factors leading to N20 saturation of surface water of Prydz Bay, while biological production and upwelling are primarily responsible for the N20 oversaturation of surface water observed in subtropical and tropical regions along the cruise track.     

Composition and distribution of fish species collected during the fourth Chinese National Arctic Research Expedition in 2010

There are awareness and concerns caused by the decreasing sea ice coverage around the Arctic and Antarctic due to effects of climate change. Emphasis in this study was on rapid changes in Arctic sea ice coverage and its impacts on the marine ecology during the fourth Chinese National Arctic Research Expedition in 2010. Our purpose was to establish a baseline of Arctic fish compositions, and consequent effects of climate change on the fish community and biogeography. Fish specimens were col- lected using a multinet middle-water trawl, French-type beam trawl, otter trawl, and triangular bottom trawl. In total, 36 tows were carried out along the shelf of the Bering Sea, Bering Strait, and Chukchi Sea in the Arctic Ocean. in total, 41 fish species belonging to 14 families in 7 orders were collected during the expedition. Among them, the Scorpaeniformes, including 17 species, accounted for almost one third of the total number （34.8%）, followed by 14 species of the Perciformes （27.0%）, 5 species of the Pleuronecti- formes （22.3%）, and 2 species of the Gadiformes （15.4%）. The top 6 most abundant species were Hippoglossoides robustus, Bore- gadus saida, Myoxocephalus scorpius, Lumpenus fabricii, Artediellus scaber, and Gymnoeanthus trieuspis. Abundant species var- ied according to the different fishing methods; numbers of families and species recorded did not differ with the various fishing methods; species and abundances decreased with depth and latitude; and species extending over their known geographic ranges were observed during the expedition. Station information, species list, and color photographs of all fishes are provided.     

Influence of sea ice and sea surface temperature on the abundance of Antarctic krill in Area 48.2

In this paper we examine the relationship between Antarctic krill catch, sea ice concentration, and sea surface tempera- ture （SST）. Data on the Antarctic krill catch from 2003 to 2010 in CCAMLR Area 48.2 were combined with sea ice and SST data. Results showed that krill fishing in Area 48.2 took place from February to August each year but the catch was concentrated from March to July, with production during this period accounting for about 99.3% of the annual catch. Regression analysis showed that the catch per unit effort （CPUE） was clearly related to sea ice concentration and SST intervals. CPUE was negatively correlated with the area of sea ice among years （R2=0.64）, and the correlation was strongest （R2=0.71） when sea ice concentration was greater than 90%. Over the months the CPUE initially increased, then decreased as the area of sea ice increased. The relationship was strongest （R2=0.88） when the concentration of sea ice was 60%--70%. There was no negative correlation among years between CPUE and the ice-free area when S ST was between -2 ℃ and 3 ℃ （R2=0.21）, but there was a significant negative correlation when SST was between 1 ℃ and 2℃ （R2=0.82）. Over the months, CPUE initially increased then decreased with increasing sea ice-free area, and the relationship was strongest （R2=0.94） when SST was between 0℃and 1 ℃. This study shows that sea ice concentra- tion and SST have significant effects on the abundance of krill in Area 48.2, and the findings have practical significance for the use and conservation of Antarctic krill resources.     

Scale and scope of maritime cargoes through the Arctic Passages

This paper investigates the sources of goods being shipped through the Arctic passages, and trade generated in the Arc- tic, including oil and gas exploitation. Furthermore, it assesses the present situation for maritime cargo shipped from the Far East to Northwestern Europe and North America. Two main types of cargo are predicted to pass through the Arctic passages in the future. First, about 10 million t of liquefied natural gas will be delivered from Russia and the Nordic Arctic to the Far East by 2030. Second, there will be two-way trade flow of containerized cargo from the Far East to Europe and the United States through the North- east, Central and Northwest Passages. This will relieve pressure on present routes from the Far East to Northwestern Europe and North America. If Arctic navigation is technically possible in all seasons and shipping costs fall to those of ordinary ships, then assuming an equal share of shipping volume with the traditional canal routes, the maximum container freight passing through the Arctic passages by 2030 will be approximately 17.43 million TEUs （Twenty-foot Equivalent Units） per year, which is 85% of the volume transported on traditional canal routes in 2011. We conclude that there will be large-scale gas transportation through the Northeast Passage in the near future, and transit shipping across the Arctic will focus more on container transportation. The differences in shipping costs between Arctic routes and traditional canal routes are also compared.     

Global distributions of storm-time ionospheric currents as seen in geomagnetic field variations

To investigate temporal and spatial evolution of global geomagnetic field variations from high-latitude to the equator during geomagnetic storms, we analyzed ground geomagnetic field disturbances from high latitudes to the magnetic equator. The daytime ionospheric equivalent current during the storm main phase showed that twin-vortex ionospheric currents driven by the Region 1 field-aligned currents （R1 FACs） are intensified significantly and expand to the low-latitude region of-30~ magnetic latitude. Centers of the currents were located around 70~ and 65~ in the morning and afternoon, respectively. Corresponding to intensification of the R1 FACs, an enhancement of the eastward/westward equatorial electrojet occurred at the daytime/nighttime dip equator. This signature suggests that the enhanced convection electric field penetrates to both the daytime and nighttime equa- tor. During the recovery phase, the daytime equivalent current showed that two new pairs of twin vortices, which are different from two-cell ionospheric currents driven by the R1 FACs, appear in the polar cap and mid latitude. The former led to enhanced north- ward Bz （NBZ） FACs driven by lobe reconnection tailward of the cusps, owing to the northward interplanetary magnetic field （IMF）. The latter was generated by enhanced Region 2 field-aligned currents （R2 FACs）. Associated with these magnetic field variations in the mid-latitudes and polar cap, the equatorial magnetic field variation showed a strongly negative signature, produced by the westward equatorial electrojet current caused by the dusk-to-dawn electric field.