Impact of transparent exopolymer particles on the dynamics of dissolved organic carbon in the Amundsen Sea,Antarctica

The Southern Ocean is an important carbon sink pool and plays a critical role in the global carbon cycling.The Amundsen Sea was reported to be highly productive in inshore area in the Southern Ocean.In order to investigate the influence of transparent exopolymer particles(TEP)on the behavior of dissolved organic carbon(DOC)in this region,a comprehensive study was conducted,encompassing both open water areas and highly productive polynyas.It was found that microbial heterotrophic metabolism is the primary process responsible for the production of humic-like fluorescent components in the open ocean.The relationship between apparent oxygen utilization and the two humic-like components can be accurately described by a power-law function,with a conversion rate consistent with that observed globally.The presence of TEP was found to have little impact on this process.Additionally,the study revealed the accumulation of DOC at the sea surface in the Amundsen Sea Polynya,suggesting that TEP may play a critical role in this phenomenon.These findings contribute to a deeper understanding of the dynamics and surface accumulation of DOC in the Amundsen Sea Polynya,and provide valuable insights into the carbon cycle in this region.

Pan-African metamorphism and magmatism in the Prydz Belt,East Antarctica:a geochronological perspective

The Prydz Belt in East Antarctica underwent extensive reworking during the late Neoprotertozoic–early Paleozoic Pan-African orogeny,which is characterized by granulite facies,clockwise P–T paths,and high dT/dP values.This study compiles the existing age and composition data of zircon and monazite from metamorphic rocks and links their key characteristics to the metamorphic evolution of the Prydz Belt.The frequency of zircon U–Pb ages starts to increase noticeably from~555 Ma,peaking between 530 Ma and 520 Ma,followed by a dramatic decline after 520 Ma.High Th/U values(>0.1)of zircon are observed from~545 Ma,displaying a noticeable increasing trend in Th/U values before a rapid decline from~520 Ma.The frequency of monazite ages progressively increases from~540 Ma,reaching its peak at 515 Ma,and then rapidly decreases after 490 Ma.Combined with the crystallization behaviors of zircon and monazite,this study suggests that the systematic changes in Th/U values of zircon after 545 Ma indicate a transition in the thermal regime of the Prydz Belt towards the cooling stage.Abundant growth of zircon and monazite corresponds to the post-peak cooling process,while the crystallization peak of monazite lags behind that of zircon by~5–15 Ma,which indicates a relatively low cooling rate.Though the granitic intrusions accompanied the entire metamorphic evolution,the majority of them are younger than 520 Ma.The results suggest that the Pan-African event likely peaked at~555–545 Ma and gradually cooled to near-solidus conditions at~520–510 Ma,with a relatively slow average cooling process.

Polymetamorphism of the ultrahigh-temperature granulites in the Rauer Group,East Antarctica:new evidence from zircon SHRIMP U-Pb ages

The Rauer Group is located on the eastern margin of the early Paleozoic Prydz Belt in East Antarctica,and the typical ultrahigh-temperature(UHT,>900℃)granulites outcrop on Mather Peninsula.However,the timing of UHT metamorphism and P–T path of the UHT granulites have long been debated,which is critical to understanding the tectonic nature and evolution history of the Prydz Belt.Thus,both a sapphirine-bearing UHT metapelitic granulite and a garnet-bearing UHT mafic granulite are selected for zircon SHRIMP U-Pb age dating.The results show that metamorphic zircon mantles yield weighted mean^(206)Pb/^(238)U ages of 918±29 Ma and 901±29 Ma for the metapelitic and mafic granulites,respectively,while zircon rims and newly grown zircons yield weighted mean^(206)Pb/^(238)U ages of 523±9 Ma and 532±11 Ma,respectively.These new zircon age data suggest that the UHT granulites may have experienced polymetamorphism,in which pre-peak prograde stage occurred in the early Neoproterozoic Grenvillian orogenesis(1000–900 Ma),whereas the UHT metamorphism occurred in the late Neoproterozoic to early Paleozoic Pan-African orogenesis(580–460 Ma).This implies that P–T path of the UHT granulites should consist of two separate high-grade metamorphic events including the Grenvillian and Pan-African events,which are supposed to be related to assembly of Rodinia and Gondwana supercontinents respectively,and hence the overprinting UHT metamorphic event may actually reflect an important intracontinental reworking.

Methods for ice velocity mapping in West Antarctica using historical optical satellite images

The Antarctic Ice Sheet harbors more than 90%of the Earth ice mass,with significant losses experienced through dynamic thinning,particularly in West Antarctica.The crucial aspect of investigating ice mass balance in historical periods preceding 1990 hinges on the utilization of ice velocities derived from optical satellite images.We employed declassified satellite images and Landsat images with normalized cross correlation based image matching,adopting an adaptive combination of skills and methods to overcome challenges encountered during the mapping of historical ice velocity in West Antarctica.A basin-wide synthesis velocity map encompassing the coastal regions of most large-scale glaciers and ice shelves in West Antarctica has already been successfully generated.Our results for historical ice velocities cover over 70%of the grounding line in most of the West Antarctic basins.Through adjustments,we uncovered overestimations in ice velocity measurements over an extended period,transforming our ice velocity map into a spatially deterministic,temporally average version.Among all velocity measurements,Thwaites Glacier exhibited a notable spatial variation in the fastest ice flowline and velocity distribution.Overestimation distributions on Thwaites Glacier displayed a clear consistency with the positions of subsequent front calving events,offering insights into the instabilities of ice shelves.

Evaluating Parameterizations for Turbulent Fluxes over the Landfast Sea-Ice Surface in Prydz Bay, Antarctica

It is crucial to appropriately determine turbulent fluxes in numerical models.Using data collected in East Antarctica from 8 April to 26 November 2016,this study evaluates parameterization schemes for turbulent fluxes over the landfast seaice surface in five numerical models.The Community Noah Land Surface Model with Multi-Parameterizations Options(Noah_mp)best replicates the turbulent momentum flux,while the Beijing Climate System Model(BCC_CSM)produces the optimum sensible and latent heat fluxes.In particular,two critical issues of parameterization schemes,stability functions and roughness lengths,are investigated.Sensitivity tests indicate that roughness lengths play a decisive role in model performance.Based on the observed turbulent fluxes,roughness lengths over the landfast sea-ice surface are calculated.The results,which can provide a basis for setting up model parameters,reveal that the dynamic roughness length(z0m)increases with the increase of frictional velocity(u*)when u*≤0.4 m s^(−1) and fluctuates around 10^(−3 )m when u*>0.4 m s^(−1);thermal roughness length(z0t)is linearly related to the temperature gradient between air and sea-ice surface(ΔT)with a relation of lg(z0t)=−0.29ΔT−3.86;and the mean water vapor roughness length(z0q)in the specific humidity gradient(Δq)range ofΔq≤−0.6 g kg^(−1) is 10^(−6) m,3.5 times smaller than that in the range ofΔq˃−0.6 g kg^(−1).

Chemical composition of natural waters at Broknes Peninsula, Larsemann Hills, Antarctica

The article contributes to the study of the content of major and trace elements in various types of natural waters of the Broknes Peninsula,Larsemann Hills,Antarctica collected in January–February 2014 and 2020 during the 7th and 12th Belarusian Antarctic Expeditions.Samples of old(13 samples)and newly fallen snow(5),lakes(23)and groundwater(8)were analyzed.The content of 25 major and trace elements was determined using ICP-MS method,main anions was determined by titrimetric and turbidimetric methods.Good similarity chemical composition of snow,groundwater and lake waters in spite of differences in the content of major ions and trace elements has been obtained.The influence of marine salts on natural waters are analyzed,and their accumulation in lake waters especially in the endorheic small and shallow lakes in spite of ultra-oligotrophic atmospheric precipitates are shown.The spatial heterogeneity of groundwater and temporal and spatial heterogeneity of lake waters have been demonstrated.The results are important for understanding the variabilities of major and trace elements content in snow,groundwater and lake waters,and their relationship,as well as for identifying trends in their change,taking into account anthropogenic loads in the region and climate change.

Call for Papers:Special Issue“Past and Present Climatic Change in Antarctica:Geological Proxies and Biological Processes”

Dear colleagues,We would like to invite you to participate in the special issue of the journal Advances in Polar Science(ISSN 1674-9928)entitled“Past and Present Climatic Change in Antarctica:Geological Proxies and Biological Processes”,which is expected to be published in March 2024 as general issue(Vol.35,No.1).We are honored to invite Dra.Carolina Acosta Hospitaleche,Dr.Javier N.Gelfo,Dr.Marcelo Reguero,Dra.Adolfina Savoretti and Dra.

南极文化遗产保护制度演进及对我国的启示

南极文化遗产保护制度是由英国等南极领土声索国主导建立,通过南极条约体系框架实现的。致力于保护南极环境的《马德里议定书》及附件五生效,确立了保护南极历史文化价值的关键机制。为了解南极大国主导下的南极文化遗产保护制度演进过程和内在动因,掌握南极条约体系对该议题的设置、监管以及在气候变化影响下的最新发展,从而使我国更好地参与南极文化遗产管理及相关议程讨论,及时提出本国文化遗产保护方案,系统梳理60年来南极文化遗产在南极条约体系下的管理情况,从设立历史遗迹和纪念物的时期范围、指定国、地理覆盖以及设立标准等四个维度进行全面分析,揭示南极条约体系下文化遗产管理存在的代表性不均衡、受领土声索国主导以及被领土声索国当作稳固或强化其主权的工具等问题;最后以南极半岛和罗斯海地区为例,结合南极大国文化遗产保护的新动向,探讨我国参与南极文化遗产保护与管理的合理路径。

南极菲尔德斯半岛(Fildes Peninsula)和阿德利岛(Ardley Island)大气中六溴环十二烷(HBCDs)的分析

在2009—2010年南半球夏季,用大流量采样器(high-volume air sampler,HVAS)和聚胺酯泡沫(polyurethane foam,PUF)被动采样器采集了南极菲尔德斯半岛和阿德利岛6个点的大气样品,分析了HBCDs的浓度水平、异构体组成、气相-颗粒相分配和空间分布趋势.主动和被动采集大气样品中ΣHBCDs浓度(α-HBCD、β-HBCD、γ-HBCD的浓度)范围分别为n.d.(未检出)—2.73 pg·m^(−3)和0.41—3.39 pg·m^(−3),与北极和偏远地区浓度水平一致,远低于城市和工业区的污染水平.HBCDs在主动采集的颗粒相和气相中的平均比例分别为67%和33%,颗粒相以α-HBCD(57%)为主,气相以γ-HBCD(53%)为主;被动采集的PUF样品中γ-HBCD(64%)占优势.经过主动采样和被动采样的对比研究,对采样速率进行校正后,PUF被动采样器可以用于南极大气样品的采集.南极大气中HBCDs的检出,表明HBCDs具有持久性和潜在的长距离大气传输能力;南极长城站附近大气中HBCDs浓度水平略高,反映了有限的人类活动对南极环境产生了影响.

Phaeocystis globosa与Phaeocystis antarctica叶绿体psbA基因的比较

测定了2株球形棕囊藻PhaeocystisglobosaP1、P2的 psbA基因序列 ,发现得到的2个序列完全相同。以P2序列对比分析了P.globosa和P.antarctica的psbA基因在DNA序列、氨基酸序列和RNA二级结构上的差异性 ,发现2种棕囊藻psbA基因DNA序列和氨基酸序列非常保守 ,无插入/缺失 ,其核苷酸和氨基酸变异率分别为1.88 %和1.13 %。与核基因核苷酸的碱基替换不同 ,psbA基因核苷酸的碱基替换主要发生在密码子的第1位上 ,且不引起氨基酸的变化 ,引起氨基酸变化的碱基替换都发生在密码子的第2位和第3位上。在RNA二级结构上两序列的1～4茎环结构完全相同 ,表现出明显的棕囊藻属的特异性 ,其它结构区域差异较大 ,种间差异表现明显。由于 psbA基因DNA序列和氨基酸序列非常保守 ,可能不适宜棕囊藻属的系统发育分析。但其RNA二级结构可能对于棕囊藻的分子分类有一定的参考价值。

南极光学天文望远镜控制软件关键技术

南极天文望远镜控制软件是望远镜软件系统的重要组成部分,是控制计算机在望远镜用户层和设备层之间运行的关键技术。对于用户层,控制软件需具备全自动观测的交互接口、卫星通信条件下的远程访问和故障诊断等功能;对于设备层,控制软件不但要完成对天体目标的精确指向和精密跟踪、计算并补偿系统误差和控制关键部件以达到目标像质,而且需实现对电源分配系统、除霜及加热系统的控制、设备及环境信息的采集和监测等。相比于普通台址,在南极大陆运行的光学天文望远镜有其独特的特点,控制软件需进行特殊设计。本文重点从操作系统选择、远程建立望远镜指向误差修正模型方法、全自动观测软件接口、卫星通信及远程运维、望远镜实时状态监测和故障诊断等方面探讨了南极天文光学望远镜控制软件的关键技术和设计原则,并展望未来技术的发展,为南极天文望远镜的研制和控制系统研发提供技术储备。

东南极米洛半岛尖晶石-堇青石麻粒岩变质作用与年代学研究

东南极普里兹构造带被认为受到格林维尔期及泛非期两期构造热事件的影响,分别与罗迪尼亚和冈瓦纳超大陆的演化密切相关,但对两期构造热事件的性质还存在争议。为了进一步完善该构造带的演化历史,从矿物学、岩石学、相平衡模拟、锆石年代学等角度对普里兹构造带米洛半岛尖晶石-堇青石麻粒岩进行了研究。结果表明其主期矿物组合为尖晶石+堇青石+黑云母+矽线石+少量石榴子石+钾长石+钛铁矿,温压条件为870~910℃、0.64~0.69 GPa,晚期退变至810~820℃、0.49~0.53 GPa,并暗示了更高的峰期变质条件(T>910℃,P>0.69 GPa)。CL图像显示锆石具有明显的核-幔-边结构,LA-ICP-MS锆石U–Pb年代学分析显示核部年龄主要集中在613±7 Ma到877±9 Ma,最大值916±11 Ma,比典型的格林维尔期年龄年轻。锆石边部加权平均年龄为526±8 Ma,其Th/U比值范围较大(0.06~1.23),多数Th/U比值较高(>0.1),应代表峰后冷却结晶阶段。尖晶石-堇青石麻粒岩记录了中低压/高温—超高温的变质条件,结合区域已有资料,可能具有顺时针轨迹,其变质演化历史可能反映了碰撞造山之后的伸展阶段,推测与冈瓦纳超大陆的聚合过程有关。

南极中山站伯氏肩孔南极鱼体液和肠道微生物的分离鉴定及功能分析

为研究南极鱼体微生物的功能,对采自南极中山站附近海域的伯氏肩孔南极鱼(Trematomus bernacchii)体液和肠道内容物中的微生物进行筛选培养,挑选代表性菌株进行生理生化特性测定和次级代谢产物功能验证,并在活体上进行功能初探,观察在低温环境下其对宿主的影响。结果表明:分离获得的菌株主要分布在变形菌门(Proteobacteria)和厚壁菌门(Firmicutes),通过16S rDNA基因序列比对发现,菌株Ignatzschineria sp.LJ11可能是一株潜在新种;伊格纳茨氏菌属(Ignatzschineria)和芽孢杆菌属(Bacillus)菌的菌液粗提物对枯草芽孢杆菌(Bacillus subtilis ATCC 6633)、嗜水气单胞菌(Aeromonas hydrophila ATCC 35654)及金黄色葡萄球菌(Staphylococcus aureus)有明显的抑制作用;用菌株Ignatzschineria sp.LJ11和Bacillus sp.hb117饲喂的斑马鱼在低温下存活的时间较对照组更长;肠道微生物多样性分析显示,投喂Bacillus sp.hb117的斑马鱼肠道微生物中气单胞菌属(Aeromonas)细菌占比最高(超过60%),而投喂Ignatzschineria sp.LJ11的斑马鱼肠道微生物中弧菌属(Vibrio)为优势属。研究表明,在低温(18℃)条件下使用不同类型培养基从伯氏肩孔南极鱼体液和肠道内容物中分离出的多为变形菌门和厚壁菌门,这些菌株具有新型抗生素潜力,同时还有增强宿主耐寒的潜质,该发现为进一步探究极地细菌功能提供了新的思路。

吸附-聚合物修饰组合固定化Candida antarctica脂肪酶研究

通过吸附法联合PEG非共价修饰,研发了一种固定化南极假丝酵母脂肪酶(Candida antarctica lipase)的新方法,可以有效提高固定化酶在非水介质中的催化活性。最佳固定化条件为硅藻土:酶粉(W/W)=8,PEG4000:酶粉(W/W)=0.6,缓冲液pH7.5。采用三油酸甘油酯与甲醇的转酯化反应,测定了固定化酶的转酯活性。结果表明,固定化酶同时加入PEG进行非共价修饰,可显著提高固定化酶的转酯活力。PEG修饰的固定化酶转酯比活是未经PEG修饰的固定化酶的4.1倍,转酯酶活回收率为604.8%,说明PEG两性分子的特性对制备用于非水介质的固定化酶有重要作用。该固定化方法可显著提高Candida antarctica脂肪酶在非水介质中的催化效率,且固定化方法简单、成本低,具有工业应用价值。

The absolute gravity measurement by FG5 gravimeter at Great Wall Station,Antarctica

Gravity measurement is of great importance to the height datum in Antarctica. The absolute gravity measurement was carried out at Great Wall Station, Antarctica, using FG5 absolute gravity instrument. The gravity data was processed with corrections of earth tide, ocean tide, polar motion and the atmospher, and the RMS is within -3×10^-8 ms^-2. The vertical and horizontal gravity gradients were measured using 2 LaCoaste ＆ Romberg （LCR） gravimeters. The absolute gravity measurement provides the fundamental data for the validation and calibration of the satellite gravity projects such as CHAMP, GRACE and GOCE, and for the high accuracy geold model.

Petrography and mineral chemistry of 4 carbonaceous chondrites from the Grove Mountains,Antarctica

Petrography and mineral chemistry of four carbonaceous chondrites （ GRV 020017, GRV 020025, GRV 021579, GRV 022459 ） collected from the Grove Mountains （ GRV）, Antarctica, were reported here. All four chondrites are unequilibrated, as indicated by well shaped chondrules and the chemical variations of olivine and low-Ca pyroxene. The modal abundance ratio of matrix/chondrule are 2 （ GRV 020017）, 2. 8 （ GRV 020025 ）, l. 2 （ GRV 021579 ）, 1 （ GRV 022459 ）. GRV 022459 has the largest chondrules （0.6--2.0 ram）. A total of 30 Ca-Al-rich inclu- sions were found in the four meteorites. Most inclusions were highly altered, with a- bundant phyllosilicates in the inclusions of GRV 020017 and GRV 020025. On the base of petrography and mineral chemistry, these chondrites are classified as CM2 （GRV 020017 and 020025）, CO3 （GRV 021579） and CV3 （GRV 022459）.

Preliminary result of imaging riometer at Zhongshan Station, Antarctica

An imaging riometer with 8×8 antenna array was installed successfully at Zhongshan Station, Antarctica in January 1997.The structure and working principle of the instrument are described. The first set of observation data is analyzed and the quiet day curve(QDC) are deduced. Preliminary results show that cosmic noise absorption is very different between night side and magnetic noon. In night side, there are often short duration impulsive absorption events with a large absorption area in the northern side of the station, stretching in an east west direction. In magnetic noon the absorption event is continuous, which lasts for more than 1 h with the absorption area strengthening in the northern and southern sides and weakening in the middle. It is thought that the absorption is caused by aurora particle precipitation in night side and by soft particle precipitation or convection in cusp at magnetic noon.

Weathering,shock metamorphism and type distribution patterns of 98 ordinary chondrites from the Grove Mountains,Antarctica

Petrography and mineral chemistry of ninety-eight ordinary chondrites from Grove Mountains （GRV）, Antarctica, were presented and their. Weathering effect, shock metamorphism and type distribution patterns were discussed in this study. Among them, six are unequilibrated ordinary chondrites, including 3 H3 and 3 L3 ; and 92 meteorites are equilibrated ordinary chondrites, including 24 H-group （ 13 H4, 10 H5, 1 H6）, 64 L-group （2 L4, 44 L5, 18 L6） and 4 LL-group （3 LL4, 1 LL5）. Most GRV ehondrites （ 〉 90% ） displayed minor weathering effect （ W1 and W2）. About half of the meteorites experienced severe shock metamorphism. They commonly contain shock-induced melt veins and pockets. These heavily shocked meteorites provide us with natural samples for study of high-pressure polymorphs of minerals. In addition, the Grove Mountains collection seems to have more abundant unequilibrated and L group ordinary ehondrites compared to the US Antarctic meteorite collection which were mainly found along the Transantarctic Mountains.

Petrology of ureilites from Grove Mountains,Antarctica:Constraints on the origins

Ureilites are a common group of achondrites with a high abundance of carbon. They probably have a genetic relationship with chondrites, hence provide an insight into origin and evdution of terrestrial planets. A new meteorite-rich region, Grove Mountains （ GRV）, was found by the Chinese Antarctic Research Expedition, with discovery of 9834 meteorites. Of 2433 meteorites classified, 9 ureilites have been identified. In this paper, we report petrography of 6 of these ureilites. Four ureilites contain graphite and exhibit triangle conjunction and common reduced margins of divine. GRV 052382 probably experienced heavy shock metamorphism followed by fast coding, as indicated by mosaic texture or fine-grained granular texture of olivine. GRV 022931 was highly reduced of these ureilites, with olivine as isolated grains in abundant carbonaceous matrix. All 9 ureilites are monomict, and arc classified into subtype II （with medium FeO content, Fa15-18 ） and subtype I （with high FeO content, Fa 〉 18） based on compositions of the cores of olivine. The diverse mineral compositions and petrography of these ureilites suggest that they are not paired and reveal a multi-event history of the parent body. Partial melting of the parent body produced carbon-rich magma, followed by crystallization of graphite and silicates. Later, graphite was partially inverted to diamond by shock events. Reburial of the shocked debris experienced various degree of thermal metamorphism. Finally, these rocks were excavated from the parent asteroid and ejected into Earth-cross orbit by another impact event.

Composition of plagioclases in volcanic rocks of King George Island, Antarctica with reference to the petrogenetic significance

Plagioclases occur mainly as phenocrysts in volcanic rocks of King George Island, South Shetland Islands, West Antarctica. In basaltic andesites and andesites of Keller Peninsula and Ullman Spur (Admiralty Bay), they are high structure state labradorite andesines; and in high Al basalts and basaltic andesites of Barton and Weaver peninsulas (Maxwell Bay), they are high structure state bytownite anorthites.∑[WT9.BZ]REE, La/Yb ratios and δEu values of plagioclases from Admiralty Bay are higher than those from Maxwell Bay. All plagioclases have rather identical chondrite normalized transitional element distribution patterns, probably reflecting that crystal structure rather than composition of plagioclase controls their diversity. Compositions of plagioclases depend chiefly on those of their host rocks, compositional differences of plagioclases reveal that basaltic magmas in the Admiralty Bay area are more evolved than in the Maxwell Bay area.