Antarctic ice sheet GLIMMER model test and its simplified model on 2-dimensional ice flow

The three-dimensional finite difference thermodynamic coupled model on Antarctic ice sheet, GLIMMER model, is described. An idealized ice sheet numerical test was conducted under the EISMINT-1 benchmark, and the characteristic curves of ice sheets under steady-state was obtained. Based on this, this model was simplified from a 3-dimensional one to 2-dimensional one. Improvement of the difference method and coordinate system was proposed. Evolution of the 2-dimensional ice flow was simulated under coupled temperature field conditions. The results showed that the characteristic curves deriving from the conservation of the mass, momentum and energy agree with the results of ice sheet profile simulated with GLIMMER model and with the theoretical results. The application prospect of the simplified 2-dimensional ice flow model to simulate the relation of age-depth-accumulation rate in Dome A region was discussed.     

Ice radar investigation at Dome A, East Antarctica: Ice thickness and subglacial topography

Dome A, located in the central East Antarctic ice sheet (EAIS), is the highest summit of the Antarctic ice sheet. From ice-sheet evolution modeling results, Dome A is likely to preserve over one million years of the Earth’s paleo-climatic and -environmental records, and considered an ideal deep ice core drilling site. Ice thickness and subglacial topography are critical factors for ice-sheet models to determine the timescale and location of a deep ice core. During the 21st and 24th Chinese National Antarctic Research Expedition (CHINARE 21, 2004/05; CHINARE 24, 2007/08), ground-based ice radar systems were used to a three-dimensional investigation in the central 30 km×30 km region at Dome A. The successfully obtained high resolution and accuracy data of ice thickness and subglacial topography were then interpolated into the ice thickness distribution and subglacial topography digital elevation model (DEM) with a regular grid resolution of 140.5 m×140.5 m. The results of the ice radar investigation indicate that the average ice thickness in the Dome A central 30 km×30 km region is 2233 m, with a minimal ice thickness of 1618 m and a maximal ice thickness of 3139 m at Kunlun Station. The subglacial topography is relatively sharp, with an elevation range of 949–2445 m. The typical, clear mountain glaciation morphology is likely to reflect the early evolution of the Antarctic ice sheet. Based on the ice thickness distribution and subglacial topography characteristics, the location of Kunlun Station was suggested to carry out the first high-resolution, long time-scale deep ice core drilling. However, the internal structure and basal environments at Kunlun Station still need further research to determine.     

Antarctic ice sheet GLIMMER model test and its simplified model on 2-dimensional ice flow

The 3-dimensional finite difference thermodynamic coupled model on Antarctic ice sheet, GLIMMER model, is described. An idealized ice sheet numerical test was conducted under the EISMINT-1 benchmark, and the characteristic curves of ice sheets under steady state were obtained. Based on this, this model was simplified from a 3-dimensional one to 2-dimensional one. Improvement of the difference method and coordinate system was proposed. Evolution of the 2-dimensional ice flow was simulated under coupled temperature field conditions. The results showed that the characteristic curves deriving from the conservation of the mass, momentum and energy agree with the results of ice sheet profile simulated with GLIMMER model and with the theoretical results. The application prospect of the simplified 2-dimensional ice flow model to simulate the relation of age-depth-accumulation in Dome A region was discussed.     

Preliminary results of ice radar investigation along the traverse between Zhongshan and Dome A in East Antarctic ice sheet: Ice thickness and subglacial topography

During the 24th Chinese National Antarctic Research Expedition (CHINARE 24, 2007/08), a ground-based ice radar was used to survey ice thickness and subglacial topography along the 1170 km traverse between Zhongshan and Dome A in East Antarctic ice sheet (EAIS). Ice-bedrock interface was detected along 82% of the traverse and data was collected at a horizontal resolution of <5.6 m. The data was processed to produce curves of ice thickness distribution and subglacial topography along the traverse. The results indicate that, along the traverse, the average ice thickness is 2037 m, smaller than the average ice thickness in EAIS; the thickest ice is at 730 km, and the thinnest ice (891 m) is at the edge of the ice sheet, but the slightly larger ice thickness (1078 m) in inland appears at 1020 km; the average subglacial topography elevation is 728 m, greatly larger than the average value in EAIS, and the largest elevation reaches up to 2650 m at 1034 km. The lowest terrain is located at 765 km. In further inland of 900–1170 km, the subglacial topography is relatively high due to the existence of the Gamburtsev Subglacial Mountains in the region. Generally, the influence of subglacial topography on ice surface is not significant, except at 900 km where great rise of subglacial topography causes evident uplift of ice surface. Where ice-bedrock interface was detected, the frequent and strong change of ice thickness and subglacial topography in small-scale means large bedrock roughness along the traverse, and is considered as the result of the integrated influence of ice flow, basal environments and geology. The segment where bedrock was not detected has very large ice thickness. The strong ice flow there also makes internal structure more complicated and induces serious attenuation of radar signals.     

Increasing atmospheric pollution revealed by Pb record of a 7 000-m ice core

Concentrations of Pb in Dasuopu ice core in the Qinghai-Tibetan Plateau have been directly measured by ICP-MS at pg/g level. The Pb profile shows a very significant increase in modern times due to anthropogenic input. The use of leaded gasoline in the South Asian countries may be a main source of Pb in this region. The input of Pb to the Dasuopu Glacier is mainly supplied by Indian summer monsoon moisture which traverses the pass at the head of the Dasuopu Glacier.     

Type distribution pattern and pairing of ordinary chondrites from Grove Mountains, Antarctica

Twenty-eight meteorites were collected on blue ice in the Grove Mountains region, Antarctica, by the 16th Chinese Antarctic Research Expedition (CHINARE). 26 out of the stones are ordinary chondrites, and their chemical-petrographic types are assigned based on electron probe microanalyses, petrography and mineralogy. 6 of them are unequilibrated L-chondrites, and the other 20 chondrites are equilibrated, including 6 H-group (3 H4, 1 H5 and 2 H6), 9 L-group (3 L4, 1 L5 and 5 L6) and 5 LL-group (2 LL4 and 3 LL5). Detailed comparative study suggests that 10 of them (including other 2 chondrites collected by the 15th CHINARE) could be paired, and represent 5 individual fall events. Hence, all 32 meteorites collected from the Grove Mountains probably belong to 27 fall events, suggestive of meteorite transferring and concentrating processes. The Grove Mountains are likely a new meteorite-enriched region. Distribution patterns of chemical-petrographic type and mass of the Grove Mountains meteorites are significantly distinct from those found in other regions, indicative of their unique sources and/or concentration mechanism. However, more studies are required in order to clarify these differences.     

Recent area and ice volume change of Kangwure Glacier in the middle of Himalayas

This paper calculated and evaluated the area and ice volume changes of Kangwure Glacier in Mt. Xixiabangma, middle of Himalayas in the past 3 decades, based on the field survey of glacier boundary position by differential GPS and glacier depth by Ground Penetrating Radar (GPR), together with the topographic map and remote sense data. The studied data showed that the Kangwure Glacier has experienced significant mass deficit since the 1970s, with 34.2% of area loss, 48.2% of ice volume loss and 7.5 m of average thickness decrease. This result revealed that the ice volume loss of Himalayan glaciers was more serious than expected. Analysis of meteorological data from two weather stations in the region of Mt. Xixiabangma, shows that the air temperature of this region has risen from the middle of the 20th century to the beginning of the 21st century. Significant retreat of Himalayas glacier driven by climatic warming will have a remarkable impact on hydrology and ecosystem.     

A new type of ice formation zone found in the Himalayas

Ice formation was studied on the Dasuopu Glacier located in the Mount Xixabangma (28°23′ N, 85°43'E) in the Himalayas. Snow pits and shallow ice cores are analyzed to reveal ice formation process. The results show that the ice formation process, or in other words, the process of densitifica-tion, on the col (7 000 m a.s. I.) of the Dasuopu Glacier is a stable, slow and gradual process. The snow-ice transformation on the glacier is estimated to be 30-40 m below the surface. The temperature on the Dasuopu Glacier is very low (～ - 14℃ at 10 m) and similar to that in polar type ice cap. We, therefore, speculate that the process of snow-ice transformation is undertaken under snow pressure, and that there is a percolation zone on the Dasuopu Glacier. The high altitude of the col and monsoon snow fall accompnied by heavy cloud and high albedo favorite the percolation zone formation.     

电阻率冰厚监测装置在南极海冰考察中的应用

电阻率冰厚监测装置是中国第21次南极考察中海冰厚度监测的技术设备之一。结合南极极端环境,对基于冰、水不同电传导性质的电阻率冰厚监测装置首次在南极海冰考察中所取得的数据进行了分析,总结出极地海冰不稳定的现场环境和低温是影响该装置测量精度的主要因素,并依据分析结果对该装置提出了改进措施。     

Sedimentary environments of the Cenozoic sedimentary debris found in the moraines of the Grove Mountains, east Antarctica and its climatic implications

During the field work of the 1998～1999's and 1999～2000's Chinese National Antarctic Research Expedition (CHNARE) in the Grove Mountains, east Antarctica, some Cenozoic sedimentary debris are found in two terminal moraine banks over the blue ice near Harding Mount in the center of this region. All the debris are of characteristics of glaciogenic diamicton and belong to the products of the glacial movements of the East Antarctic Ice Sheet. In this paper, the authors make a detailed study on the sedimentary environments of the sedimentary debris through petrologic, sedimentological, mineralogical, and geo-chemical methods. Characteristics of their sedimentary textures and structures, grain size distributions, quartz grains' surface textures and features, together with their geo-chemical compositions all show that these sedimentary rocks are a kind of subglacial lodgement tills which are deposited in the ice sheet frontal area by reactions of glacial movements and glaciogenic melt water. Their palaeoenvironmental implications in revealing the retreat history of East Antarctic Ice Sheet are discussed. The authors draw the conclusion from current study that the glacial frontal of the East Antarctica Ice Sheet might have been retreated to this area during the Pliocene Epoch, which represents a warm climate event accompanied by a large-scale ice sheet retreat in Antarctica at that time.     

冰后回弹对南极地区冰盖质量变化影响的研究

全球海平面变化关系着人类的生存和发展,一直以来就是科学界重点关注的问题;而南极地区存储的冰是影响海平面变化最主要的因素。主要详细地阐述了冰后回弹的基本理论,以及利用GRACE重力数据计算冰后回弹的基本理论;并推导了相关的计算公式。最后,利用GRACE月重力场数据对冰后回弹和南极地区质量变化进行了试算。实验结果表明:南极地区冰后回弹效应范围为-0.987~20.3 mm/a;其中在极点附近的冰后回弹效应较强。     

Recent change of the ice core accumulation rates on the Qinghai-Tibetan Plateau

Three ice cores recovered from the Himalayas (i.e. the East Rongbuk Glacier and the Far East Rongbuk Glacier at Mt. Qomolangma (Everest), and the Dasuopu Glacier at Xixiabangma) show a sharp decline in the accumulation rates since the 1950s, which is consistent with the precipitation fluctuation over India and the low northern latitude zone (5°-35°N). Correspondingly, an increasing trend is observed for the ice core accumulations from the central and northern Qingh ai-Tibetan Plateau (i.e. the Xiao Dongkemadi Glacier in the central Tanggula Mountains, the Guliya Ice Cap in the western Kunlun Mountains, and the Dunde Ice Cap in the Qilian Mountains) since the 1950s, which is consistent with the precipi tation fluctuation over the middle-high northern latitude zone (35°-70°N). However, the variation magnitude of the high-elevation ice core accumulations is more significant than that of precipitation at the low-eleva- tion places, suggesti ng its extra sensitivity of high-elevation areas to climatic change. The inter-d ecadal abrupt change of the African-Asian summer monsoon in the1960s may attribute to the recent ice core accumulation change during the recent decades.     

中山站前沿固定冰破冰方案及船舶操纵方法

为了向“雪龙号”提供一条可行的卸货用航行水道，中国第一艘自主建造的破冰船“雪龙2号”急需在南极大陆的中山站前沿复杂的固定冰中制订一条破冰路线。在“雪龙号”过去多年积累数据和经验基础之上，通过详细分析破冰水域的航行环境、固定冰区当年冰情、最新气象辅助资料以及可用的先进设备，制订一条破冰计划路线。采用首尾破冰、进退速度控制、预留距离控制以及操纵船舶辅助破冰等方法，顺利完成破冰开路任务。实际破冰结果证明，计划路线既绕开了危险的冰裂缝和冰山，也为“雪龙号”节省大量的卸货时间。总结“雪龙2号“在固定冰中的破冰能力，指出相应的困难和急需解决的问题；为我国破冰船在极区常态化航行、冰区航行的船舶驾驶员、按极地规则要求进行的冰区航行培训以及相应的业务模拟提供参考。     

Large subglacial lakes in East Antarctica at the onset of fast-flowing ice streams

Water plays a crucial role in ice-sheet stability and the onset of ice streams. Subglacial lake water moves between lakes and rapidly drains, causing catastrophic floods. The exact mechanisms by which subglacial lakes influence ice-sheet dynamics are unknown, however, and large subglacial lakes have not been closely associated with rapidly flowing ice streams. Here we use satellite imagery and ice-surface elevations to identify a region of subglacial lakes, similar in total area to Lake Vostok, at the onset region of the Recovery Glacier ice stream in East Antarctica and predicted by ice-sheet models. We define four lakes through extensive, flat, featureless regions of ice surface bounded by upstream troughs and downstream ridges. Using ice velocities determined using interferometric synthetic aperture radar (InSAR), we find the onset of rapid flow (moving at 20 to 30 m yr(-1)) of the tributaries to the Recovery Glacier ice stream in a 280-km-wide segment at the downslope margins of these four subglacial lakes. We conclude that the subglacial lakes initiate and maintain rapid ice flow through either active modification of the basal thermal regime of the ice sheet by lake accretion or through scouring bedrock channels in periodic drainage events. We suggest that the role of subglacial lakes needs to be considered in ice-sheet mass balance assessments.     

A 780-year record of explosive volcanism from DT263 ice core in east Antarctica

Ice cores recovered from polar ice sheet received and preserved sulfuric acid fallout from explosive volcanic eruptions. DT263 ice core was retrieved from an east Antarctic location. The ice core is dated using a combination of annual layer counting and volcanic time stratigraphic horizon as 780 years (1215-1996 A.D.). The ice core record demonstrates that during the period of approximately 1460-1800 A.D., the accumulation is sharply lower than the levels prior to and after this period. This period coincides with the most recent neoglacial climatic episode, the "Little Ice Age (LIA)", that has been found in numerous Northern Hemisphere proxy and historic records. The non-sea-salt SO42- concentrations indicate seventeen volcanic events in DT263 ice core. Compared with those from previous Antarctic ice cores, significant discrepancies are found between these records in relative volcanic flux of several well-known events. The discrepancies among these records may be explained by the differences in surface topography, accumulation rate, snow drift and distribution which highlight the potential impact of local glaci-ology on ice core volcanic records, analytical techniques used for sulfate measurement, etc. Volcanic eruptions in middle and high southern latitudes affect volcanic records in Antarctic snow more intensively than those in the low latitudes.     

Cenozoic terrestrial palynological assemblages in the glacial erratics from the Grove Mountains, east Antarctica

Fossiliferous glacial erratics have been found in moraines of the Grove Mountains, east Antarctica since 1998 by Chinese National Antarctic Research Expedition (CHNARE) teams. These erratics were derived from a suite of glaciogene strata hidden beneath the Antarctic Ice Sheet in the Lambert glacier drainage system, and thus provide a record of Cenozoic paleoenvironmental conditions and fossil biotas that are so far unknown from outcrops and drill cores in this region.By microfossil analysis, sparse Neogene spores and pollen grains are revealed, including: Toroisporis (Lygodiaceae), Granulatisporites (Pteridaceae?), Osmunda (Osmundaceae), Polypodiaceae, Magnastriatites (Parkeriaceae), Deltoidospora, Araucariaceae, Taxodiaceae, Podocarpus (Podocarpaceae), Dacrydium (Podocarpaceae),Pinus (Pinaceae), Keteleeria (Pinaceae), Picea (Pinaceae), Tsuga (Pinaceae), Chenopodiaceae, Artemisia (Asteraceae), Asteraceae, Gramineae,Fraxinoipollenites (Oleaceae), Oleoidearumpollenites (Oleaceae), Oleaceae, Operculumpollis, Nothofagidites (Nothofagus), Rhus, Quercus (Fagaceae), Juglans (Juglandaceae), Pterocarya (Juglandaceae), Liquidambar (Hamamelidaceae), Ulmus (Ulmaceae), Ulmoidepites (Ulmaceae), Tilia, Proteacidites (Proteaceae) and Tricolpopollenites; but without any marine diatoms. Most of the spores and pollen grains in the erratics are considered to originate from local sources except for some older exotic components that might be recycled from the basement sedimentary rocks by the ice sheet, so they are in situ sporo-palynological assemblages. Furthermore, since the source areas of the glaciogenic sedimentary rocks are assumed to be local or in the up glacier areas, the palynological assemblages in these erratics represent an inland terrestrial flora during a warmer period of the ice-sheet evolutionary history. The ages of these erratics are also discussed based on the occurrence of some diagnostic pollens such as the Artemisia, Chenopodiaceae and Nothofagus, which implies Neogene (most probably Pliocene). As a preliminary conclusion, we think that the existence of the Cenozoic glaciogenic rocks and their palynological assemblages present new evidence for a large scale glacial retreat event in the Grove Mountains of east Antarctica, and thus support a dynamic East Antarctic Ice Sheet (EAIS). Furthermore, the absence of marine fossils in the samples analyzed not only provides additional evidence for a terrestrial sedimentary environment of these erratics, but also indicates that there is no transportation of Cenozoic marine fossils from the adjacent areas of the Grove Mountains.     

基于实测冰芯数据的南极海冰厚度的数值模拟

根据我国第22次南极科学考察现场观测数据以及现场采集的冰芯分析数据,考虑太阳辐射、云量等因素对南极海冰厚度变化的影响,利用最小二乘法辨识气温与冰表面温度之间的关系,并以辨识结果所得到的冰表面温度作为上边界条件,依据实测情况取结冰点-1．81℃作为下边界条件,对一维热传导方程采用Crank-Nicolson格式进行离散,对南极中山站内拉湾附近海域海冰厚度变化进行了数值模拟,并与现场观测的海冰厚度数据进行了对比。     

Formate and acetate records in the Muztagata ice core, Northwest Tibetan Plateau

Formic and acetic acids (HCOOH, CH3COOH), originating mainly from biosphere (release by plants, combustion of biomass, motor exhaust and oxidation of organism, etc.), are two simple organic chemical com- pounds in troposphere. Though the concentration of these two organic acids is low in atmosphere, they are the main [1] sources of free acidity in precipitation of remote regions , and contribute minor chemical constituents to the balance between anions and cations, especially to some atm…     

XPGR结合小波变换的南极冰盖冻融探测

针对微波辐射计的交叉极化比率(cross polarizedgradientratio,XPGR)算法在冰盖冻融探测中存在的问题,提出了不依赖于实地观测数据的XPGR结合小波变换模型进行南极冰盖冻融探测的方法,即运用小波变换模型对XPGR的长时间序列数据做小波变换,得到南极冰盖融化开始、持续和结束时间分布图.此方法由于能自动选取大量样本点且具有一定的去噪效果,不仅提高了冰盖冻融探测的计算效率、实用性和可操作性,而且还在一定程度上提高了冰盖冻融探测的精度,更好地实现了南极地区冰盖冻融监测系统建设的业务化运行目标.     

Influence of interannual variability of Antarctic oscillation on mei-yu along the Yangtze and Huaihe River valley and its importance to prediction

Both correlation analysis and case study indicate that Antarctic oscillation (AAO) is closely related with summer rainfall in eastern China. When AAO is stronger in boreal spring, especially in May, there is more mei-yu rainfall in summer with a longer period along the Yangtze and Huaihe River valley. In contrast, there is less rainfall with a shorter period corresponding to a weaker AAO. Besides, an anomalous AAO changes the position and intensity of several circulation systems, which are important to summer rainfall along the Yangtze and Huaihe River valley. Furthermore, the Antarctic sea ice is negatively correlated with the intensity of AAO with a 6-month leading time. The result in this study provides a new method for the prediction of mei-yu.