Mesozoic paleomagnetic anomalies south of Ceylon

Ceylon was one of the connecting continental links in the ensemble of the united Indian and Antarctic continents when Gondwana split up. However, the precise position of Ceylon is still undetermined. Some publications attribute its position to different regions near Enderby Land. The analysis of the linear magnetic anomalies in the Central Basin of the Indian Ocean south of Ceylon and near the Antarctic coast (the Cosmonaut Sea and the Riiser-Larsen Sea) yielded evidence for the position of Ceylon in the ensemble of the Indian and Antarctic continents: it was east of Gunnerus Ridge in the Cosmonaut Sea. The breaking away of Ceylon from Antarctica occurred in the period of chron M11r (136.44–136.90 Ma). Before breaking away, the eastern flank of the Gunnerus Ridge was joined to Ceylon and they formed a united continental block.     

Ice Mass Variation in Antarctica from GRACE Over 2002–2011

We detect the mass balance of the Antarctica ice sheet from GRACE for the recent period July 2002 through March 2011. Land hydrology contamination was corrected through global hydrological models and glacial isostatic adjustment (GIA) of the solid Earth since last deglaciation using the IJ05 model, and then a forward model was employed to adjust to bias due to smoothing filters and GRACE's limited resolution. The results show that there are two significant turning points for ice mass losses or gains near the early 2006 and the end of 2008. The ice mass losses in West Antarctica have accelerated dramatically during 2009–2011, while in East Antarctica the rate is positive, mainly caused by snow accumulation. Over the whole studying period, ice loss rates in West Antarctica (?108 ± 36 Gt/yr) are still significantly larger than the increase in East Antarctica (+72 ± 24) Gt/yr. Thus, the total Antarctica contribution to sea level rise is slightly negative ?0.18 ± 0.02 mm/yr. The rapid change of the regional ice mass in Antarctic, in the course of only several years, suggests that the Antarctica ice sheet mass balance is more sensitive to regional climate conditions than considered before.     

中国南极长城站室内空气微生物含量七年前后的比较

中国南极长城站室内空气微生物含量的考察结果表明,七年后,虽然一些室内空气微生物含量有所下降,即空气质量有所改善,但总体来看,略是上升势。与友邻科考站相比,长城站的多少有点偏高。也比非南极的较高纬度的某些室内空气微生物含量高。结果意味着长城站尚有提高空气质量、改善环境状况的余地。     

南极气候和海冰的时空变化特征及其与太平洋海温场的关系

应用1973～1999年南极气温和海冰资料,分别对它们进行了统计分析,结果表明,南极的最低温度中心位于东南极大陆(东方站),这种分布特征是与南极地形相对应的.南极东方站的年平均地面气温是-55.3℃;地面最高气温出现在12月至翌1月,其温度为-32.1℃;地面最低气温出现在8月,其温度为-68.2℃.南极各地区的地面气温具有不同的变化特征.根据温度的变化特征,将南极的气候分为4种类型:南极大陆型、南极半岛型、东南极沿岸型和海湾型.近年来南极半岛的气温有明显升高的趋势,而东南极沿岸的气温有明显下降的趋势,它们的变化呈明显的反位相.南极海冰与南极气温变化有较好的对应关系,气温升高的南极半岛的海冰有减少的趋势,而气温下降的东南极的海冰有增加的趋势.这种结果很难用温室效应来解释南极与全球气候变化的差异.东南极海冰变化与南太平洋的海温场存在密切关系,其影响过程是通过南极海冰范围的异常增加或减少,直接影响南极绕极流的冷暖结构及其异常冷暖水的经向输送,从而导致热带和副热带太平洋上层海温场的异常变化.     

Clay mineral composition in shallow water sediment samples near the Antarctic Peninsula and in deep-sea core samples from the pacific and the Indian-Antarctic Basins

Clay minerals in seven shallow water (100 to 600 m deep) dredged samples and in two deep-sea (3,000 to 5,000 m deep) core samples near West Antarctica were investigated by X-ray diffraction analyses. Variation of montmorillonite concentration appears to be closely related to volcanic activity. Chlorite is the most dominant constituent in most of the dredged samples, though it is not a principal component in core samples. Illite concentration is negatively correlated to that of montmorillonite. Kaolinite is found in four out of seven dredged samples near and around the Antarctic Peninsula while the content of kaolinite in two deep-sea cores from the Pacific-Antarctic Basin and the Indian-Antarctic Basin is more abundant than in the dredged samples. The clay mineral composition in the latter two basins may be closely related to volcanic activity and mechanical weathering products near and on Antarctica.     

The Australian-Antarctic segment of Gondwana

Australia is one of the major continental terranes in Gondwana’s structure. At the same time, the precise position of Australia in this structure has not yet been clearly identified. According to different works, Australia is connected to Antarctica in a number of areas near Wilkes Land, Adelie Land, and Victoria Land. The comprehensive analysis of the geological and geophysical data allows us to reconstruct the optimal relative position of the continents and to reach a conclusion about the propagation of the tectonic structures of Australia towards Antarctica.     

Ocean Tides Observed from A GPS Receiver on Floating Sea Ice Near Chinese Zhongshan Station,Antarctica

Due to limit of coverage in TOPEX/Poseidon (T/P) satellite and sparseness of in-situ tide gauges around Antarctica, the accuracy of global ocean tide models in Antarctic seas is relatively poorer than in low- and mid-latitude regions. To better understand ocean tides in Prydz Bay, east Antarctica, a GPS receiver was deployed on floating sea ice to measure tide-induced ice motion in multiple campaigns. Four online Precise Point Positioning (PPP) services are used to process the GPS data in the kinematic PPP mode, and UTide software is used to separate the major tidal constituents. Comparison between results from different processing methods (relative processing solutions from Track, kinematic PPP solutions from online services) and with bottom pressure gauge (BPG) shows that, high-accuracy tidal information can be obtained from GPS observations on floating sea ice, the root-sum-square (RSS) for the eight major constituents (O1, K1, P1, Q1, M2, S2, N2, K2) is below 4 cm. We have also studied the impacts of data span and filter edge effects at daily boundaries on the accuracy of tide estimates, and found that to obtain reliable tide estimates and neglect the filter edge effects, continuous observation longer than 30 days is necessary. Our study suggests that GPS provides an independent method to estimate tides in Prydz Bay, and can be an alternative to tidal gauges, which are costly and hard to maintain in Antarctica.     

南极海冰边缘区密集度的年际变化与西风的Ekman输运

为了揭示南极海冰年际变化的机制,利用南极海冰边缘区密集度和海面风资料,选择南极海冰边缘区海冰密集度年际变化较大的5个海区进行统计分析.研究表明：南半球冬季在这5个海区海冰密集度年际变化与南侧西风的年际变化有较密切的关系,南半球冬季南极海冰边缘区南侧西风形成向北的Ekman输运对海冰边缘区的海冰密集度有重要的影响,这种影响在南太平洋和南大西洋比在南印度洋东部更明显.     

东南极伏斯特福尔德丘陵地区爱丝湖的有机地球化学特征（一）

本文利用TLC-FID和GC-MS等手段对取自东南极伏斯特福尔丘陵地区爱丝湖的柱状沉积物样的类脂物作了分析鉴定。其结果表明,该湖沉积物中的类脂物主要由烃类、长链脂以及酮、醇和甾醇组成,未发现三酰甘油醇,游离脂肪酸也极少量,而该湖水体颗粒物中却大量存在着三酰甘油醇。类脂物的分布特征表明该湖沉积物的强微生物效应,其中烃类的分布特征则说明该湖在1000年前曾有过全混合状态,从而可推断南极当时曾有过温暖的气候。     

The Bellingshausen—Amundsen basins (southeastern Pacific): Major sea-floor units and problems

The physiography of the Amundsen and Bellingshausen Basins and adjacent continental margin of Antarctica is described based on all existing geologic/geophysical data. The sea-floor morphology is the result of a complex spreading history in this region which commenced in the pre-Cretaceous. Abyssal constructional forms including the location of the abyssal plains reflect this spreading history. Another decisive event was the initiation of the circum-Antarctic current and its resultant redistribution of the sedimentary blanket. The third major controlling factor was the commencement of polar conditions on Antarctica which effected a change in continental erosional patterns.     

Temporal and spatial changes of the basal channel of the Getz Ice Shelf in Antarctica derived from multi-source data

Basal melting is an important factor affecting the stability of the ice shelf. The basal channel is formed from uneven melting, which also has an important impact on the stability of the ice shelf. Therefore, it has important scientific value to study the basal channel changes. This study combined datasets of Mosaics of Antarctica, Reference Elevation Model of Antarctica (REMA) and Operation IceBridge to study the temporal and spatial changes of basal channels at the Getz Ice Shelf in Antarctica. The relationships between the cross-sectional area and width of basal channel and those of its corresponding surface depression were statistically analyzed. Then, the changes of the basal channels of Getz Ice Shelf were derived from the ICESat observations and REMA digital elevation models (DEMs). After a detailed analysis of the factors affecting the basal channel changes, we found that the basal channels of Getz Ice Shelf were mainly concentrated in the eastern of the ice shelf, and most of them belonged to the ocean-sourced basal channel. From 2009 to 2016, the total length of the basal channel has increased by approximately 60 km. Affected by the warm Circumpolar Deep Water (CDW), significant changes in the basal channel occurred in the middle reaches of the Getz Ice Shelf. The change of the basal channels at the edge of the Getz Ice Shelf is significantly weaker than that in its middle and upper reaches. Especially in 2005–2012, the eastward wind on the ocean wind field and the westward wind around the continental shelf caused the invasion and upwelling of CDW. Meanwhile, the continuous warming of deep seawater also caused the deepening of the basal channel. During from 2012 to 2020, the fluctuations of the basal channels seem to be caused by the changes in temperature of CDW.     

Investigations of the Ecosystem in the Atlantic Sector of Antarctica (Cruise 79 of the R/V Akademik Mstislav Keldysh)

Oceanology - Field works on cruise 79 of the R/V Akademik Mstislav Keldysh aimed at investigating the ecosystems in the Atlantic sector of Antarctica were conducted from January 16 to March 1,...     

Sediment geochemistry in coastal maritime Antarctica (Admiralty Bay, King George Island): Evidence from rare earths and other elements

We report the concentrations of 22 elements in short coastal sediment cores of Admiralty Bay (King George Island, Antarctica) determined by Neutron Activation Analysis. We focus the discussion on rare earth elements (REE) because their fractionation patterns in sediments relative to local sources may offer insights about weathering, transportation, deposition, and diagenetic processes. We found strong correlations between REE and Th, indicating detrital origin. Despite strong Eh gradients, the Th-normalized redox-sensitive elements (e.g., Eu, Ce, Fe, As, and others) showed little variability within the sedimentary environment. The exceptions were U (depleted in the upper few centimeters) and Br (enriched in the upper few centimeters). While U appears to be removed from seawater via uptake across the boundary of reducing sediments, the mechanisms driving Br accumulation are unclear, but perhaps related to increasing diatom production driven by regional warming. A comparison with published concentrations from rocks representing the regional eroding units showed that the characteristics of source rock could be recognized in the REE fractionation patterns in our sediments. These results imply no significant alteration during weathering and sediment transport in the coastal region of Admiralty Bay and the prevalence of strong periglacial erosion in ice-free areas of maritime Antarctica in spite of the relatively mild regional environmental setting (e.g., high moisture and high temperatures).     

Bottom Rock Material of Polar Seas: Distribution,Composition, and Genesis

Oceanology - We have summarized the results of studies of bottom rock material in Quaternary sediments in the polar seas of the Arctic, North Atlantic, and Antarctica, obtained by sieve washing on...     

GIS-Supported Airfield Selection near Zhongshan Station,East Antarctica,based on Multi-Mission Remote Sensing Data

Abstract

As Antarctica attracts increasing attention in global climate change studies, the demand for field expeditions has increased in recent decades. Aircraft has become the most efficient mode of transportation because of the advantages of short travel times over long distances, access to unreachable locations and capability to carry different types of sensors to obtain large areal coverages. However, few studies have been published regarding Antarctic airfield site selection for heavy-wheeled aircraft. In this paper, we present methods and results of blue-ice airfield preliminary selection near Zhongshan station, East Antarctica. The geographic information system (GIS)-based method is supported by multi-mission high-resolution images from the ZY-3, WorldView-2 and Landsat-8 satellites along with existing remote sensing products. Ground truth observations were integrated with satellite panchromatic and spectral information to identify runway candidate areas. The information inferred by remote sensing data, including firn type, ice movement, surface slope and ice fracture, is used for evaluation of the airfield selection rules. Finally, the rankings and recommendations of runway candidates were performed in a GIS analysis environment. The site selection approach developed in this paper can be applied in preconstruction studies of other similar cryosphere environments to provide appropriate candidates for a final stage field investigation.     

南极长城湾沉积物中的自然金

作者在南极长城湾沉积物中首次发现金矿化、自然金和含金的碲、铋、锑化合物。本文着重报导了自然金特征、成色、共生矿物和物质来源等问题。     

南极中山站夏季下降风数值模拟个例研究

南极内陆地面辐射冷却产生的近表层冷空气,沿高原斜坡向下流动而形成下降风,其分布形态决定了南极大陆近表层风场的主要特征。我国南极中山站全年均受下降风的强烈影响。夏季晴天时,中山站的下降风一般在傍晚开始出现,风速在午夜达到极值,在次日中午之前逐渐减弱,风速有显著的日循环特征。本文选取南极中山站2010年1月的夏季下降风个例,使用常规地面气象观测资料和Polar WRF极地大气数值模式进行了分析研究。结果表明:中山站夏季夜间晴天出现偏东向的下降风时,近地面风速变化趋势与地面气温呈负相关,相关系数为-0.91。数值模拟发现,中山站下降风在距地面高度约100~150 m之间时风速最大,约为15~21 m/s。在下降风发生时,近地层大气存在逆温现象。下降风较强时,近地层逆温也较强,逆温层厚度约为200~300 m,逆温强度约为4~6℃。在地面摩擦的作用下,中山站近地面下降风风向为东南,随着高度的增加,风向逆时针偏转,最终趋于与地形等高线平行。没有太阳直接辐射时,南极大陆地区存在持续的逆温层,逆温层的出现加强了下降风气流,随着逆温的增强,大风区逐渐西移,且面积不断增加。在夏季太阳辐射造成的逆温消失的短暂时间内,逆温时产生的下降风尚不能完全消失,由此形成了较稳定的风向空间分布特征。     

Depositional environment of near-surface sediments,King George Basin,Bransfield Strait,Antarctica

Four sediment cores were collected to determine the depositional environments of the King George Basin northeast of Bransfield Strait, Antarctica. The cored section revealed three distinct lithofacies: laminated siliceous ooze derived from an increased paleoproductivity near the receding sea-ice edges, massive muds that resulted from hemipelagic sedimentation in open water, and graded sediments that originated from nearby local seamounts by turbidity currents. Clay mineral data of the cores indicate a decreasing importance of volcanic activity through time. Active volcanism and hydrothermal activity appear to be responsible for the enrichment of smectite near the Penguin and Bridgeman Islands.     

Ripple cross-laminated sediments on the East Antarctic Shelf: evidence for episodic bottom water production during the Holocene?

Biosiliceous sediments sampled from a submarine valley system on the continental shelf of East Antarctica contain intervals of ripple cross-lamination interspersed with massively bedded units. Based on radiocarbon dates from one core collected on the Mac.Robertson Shelf, the most intensely cross-laminated sediments were deposited between 6 and 3.5 kyr BP, with isolated cross-laminae deposited at other times in the Holocene. The cross-laminated sediments are interpreted here as a signal of episodic density currents flowing across the outer shelf, which result from the formation of high salinity shelf water (HSSW). This HSSW is formed in winter by brine rejection during sea ice formation and by the exchange and cooling of upwelled saline slope water, and it contributes to the bottom water produced along the continental margin of Antarctica. If this interpretation of the cross-laminae is correct, then bottom water formation and export from the East Antarctic shelf has exhibited temporal, and probably also spatial, variability throughout the Holocene. Such variability would have implications for oceanographers attempting to quantify Antarctic bottom water production rates based only on present day observations.     

南极普里兹湾1.5万年来气候演变的沉积记录

南极普里兹湾两沉积柱样代表了1.5万年来的沉积记录.其粒度特征、矿物成分、硅藻分布和地球化学等沉积特征表明,沉积记录对气候变化的反应十分敏感,尤其是发现14310aBP前后的Heinrich事件,据此将该区1.5万年来的古气候演化划分为8个阶段.