Eight glacial cycles from an Antarctic ice core

The Antarctic Vostok ice core provided compelling evidence of the nature of climate, and of climate feedbacks, over the past 420,000 years. Marine records suggest that the amplitude of climate variability was smaller before that time, but such records are often poorly resolved. Moreover, it is not possible to infer the abundance of greenhouse gases in the atmosphere from marine records. Here we report the recovery of a deep ice core from Dome C, Antarctica, that provides a climate record for the past 740,000 years. For the four most recent glacial cycles, the data agree well with the record from Vostok. The earlier period, between 740,000 and 430,000 years ago, was characterized by less pronounced warmth in interglacial periods in Antarctica, but a higher proportion of each cycle was spent in the warm mode. The transition from glacial to interglacial conditions about 430,000 years ago (Termination V) resembles the transition into the present interglacial period in terms of the magnitude of change in temperatures and greenhouse gases, but there are significant differences in the patterns of change. The interglacial stage following Termination V was exceptionally long--28,000 years compared to, for example, the 12,000 years recorded so far in the present interglacial period. Given the similarities between this earlier warm period and today, our results may imply that without human intervention, a climate similar to the present one would extend well into the future.     

Recent contributions of glaciers and ice caps to sea level rise

Glaciers and ice caps (GICs) are important contributors to present-day global mean sea level rise. Most previous global mass balance estimates for GICs rely on extrapolation of sparse mass balance measurements representing only a small fraction of the GIC area, leaving their overall contribution to sea level rise unclear. Here we show that GICs, excluding the Greenland and Antarctic peripheral GICs, lost mass at a rate of 148?±?30?Gt?yr(-1) from January 2003 to December 2010, contributing 0.41?±?0.08?mm?yr(-1) to sea level rise. Our results are based on a global, simultaneous inversion of monthly GRACE-derived satellite gravity fields, from which we calculate the mass change over all ice-covered regions greater in area than 100?km(2). The GIC rate for 2003-2010 is about 30 per cent smaller than the previous mass balance estimate that most closely matches our study period. The high mountains of Asia, in particular, show a mass loss of only 4?±?20?Gt?yr(-1) for 2003-2010, compared with 47-55?Gt?yr(-1) in previously published estimates. For completeness, we also estimate that the Greenland and Antarctic ice sheets, including their peripheral GICs, contributed 1.06?±?0.19?mm?yr(-1) to sea level rise over the same time period. The total contribution to sea level rise from all ice-covered regions is thus 1.48?±?0.26?mm?(-1), which agrees well with independent estimates of sea level rise originating from land ice loss and other terrestrial sources.     

Paleodietary changes by penguins and seals in association with Antarctic climate and sea ice extent

Positioned near the top of the food web, the dietary composition of Antarctic penguins and seals can be an excellent indicator of the regional food web and thus the status of the marine ecosystem. The dietary composition of modern penguins and seals has been well investigated; a long-term time series of data on penguin and seal diets, however, are rare. Such data, especially any predating the initiation of human harvesting of fish, whales and seals in Antarctica, are crucial for understanding and predicting responses of regional marine food webs to natural climate changes. Here we review recent progress on research of paleodietary change in Antarctic penguins and seals, specifically the Adelie penguin （Pygoscelis adeliae） and Antarctic fur seal （Arctocephalus gazella）. These studies indicate that the dietary changes of penguins correspond quite well with fluctuations in climate and sea ice extent during the Holocene. The depleted δ15N ratios found in modern Adelie penguins support the ＂krill surplus hypothesis＂ in relation to historic human depletion of krilleating fish, seals and whales.     

Mass and volume contributions to twentieth-century global sea level rise

The rate of twentieth-century global sea level rise and its causes are the subjects of intense controversy. Most direct estimates from tide gauges give 1.5-2.0 mm yr(-1), whereas indirect estimates based on the two processes responsible for global sea level rise, namely mass and volume change, fall far below this range. Estimates of the volume increase due to ocean warming give a rate of about 0.5 mm yr(-1) (ref. 8) and the rate due to mass increase, primarily from the melting of continental ice, is thought to be even smaller. Therefore, either the tide gauge estimates are too high, as has been suggested recently, or one (or both) of the mass and volume estimates is too low. Here we present an analysis of sea level measurements at tide gauges combined with observations of temperature and salinity in the Pacific and Atlantic oceans close to the gauges. We find that gauge-determined rates of sea level rise, which encompass both mass and volume changes, are two to three times higher than the rates due to volume change derived from temperature and salinity data. Our analysis supports earlier studies that put the twentieth-century rate in the 1.5-2.0 mm yr(-1) range, but more importantly it suggests that mass increase plays a larger role than ocean warming in twentieth-century global sea level rise.     

从船侧倾斜拍摄图像中提取海冰密集度的方法

为消除提取海冰密集度时因摄影镜头倾斜造成图像变形可能引起的误差,基于摄影测量学原理,对倾斜拍摄引起的图像变形进行修正,建立从倾斜拍摄的图像中提取海冰密集度的精确方法和相应的简化算法.以2006年德国南极威德尔海冬季考察中获取的图像为例,讨论了现场观测时的系统标定方法和不同算法的计算结果.对比分析验证了图像变形修正的必要性,说明简化算法能够同时保证海冰密集度计算的精度和效率.     

冬季覆盖海冰条件下海冰消融过程水盐变化分析

众多国家和地区对非常规水源利用一直给予研究和重视。冬季海冰覆盖条件下,融水质量变化特征不同于常规灌溉,研究和掌握其规律对咸水冰资源综合利用十分重要。利用冬季室外冰柱、土柱实验,以实时监测海冰消融全过程为手段,深入分析冬季覆冰条件下海冰融水水量及总盐动态变化。实验结果表明:融水量最大值出现在下午15时左右;覆盖海冰条件下,海冰消融入渗过程分为集中排盐、深度脱盐、淡水入渗三个阶段。实验结果可为冬季覆冰或咸水结冰灌溉提供技术参考。     

Biodiversity of Early-Middle Ordovician acritarchs and sea level changes in South China

Acritarchs are organic-walled cysts of unicellular pro- tists that cannot be assigned to any known group of or- ganisms. Most acritarchs are probably the resting cysts of marine eukaryotic phytoplankton. Because of their small size, abundance and diversity, as well as widespread distri- bution, acritarchs are very useful in biostratigraphic cor- relation, as well as paleobiogeographic and paleoenviron- mental studies. Furthermore, they represent the fossil re- cord of the base of the marine fo…     

雷达海冰监测系统与数值预报技术在辽东湾冰区作业中的应用

利用航海雷达在辽东湾冰区石油平台上,现场实时进行海冰观测;雷达监测海冰系统,针对海冰类型识别及对应冰厚度、流冰漂移速度、方向、冰边缘线等要素进行观测;应用统计模式分类法,对雷达观测的海冰数据进行分类、验证,其海冰分类识别结果标准率达80％以上,同时开展现场流冰跟踪数值预报业务,检验了现场雷达海冰监测、数值预报的可行性和应用性．     

Origin and fate of Lake Vostok water frozen to the base of the East Antarctic ice sheet

The subglacial Lake Vostok may be a unique reservoir of genetic material and it may contain organisms with distinct adaptations, but it has yet to be explored directly. The lake and the overlying ice sheet are closely linked, as the ice-sheet thickness drives the lake circulation, while melting and freezing at the ice-sheet base will control the flux of water, biota and sediment through the lake. Here we present a reconstruction of the ice flow trajectories for the Vostok core site, using ice-penetrating radar data and Global Positioning System (GPS) measurements of surface ice velocity. We find that the ice sheet has a significant along-lake flow component, persistent since the Last Glacial Maximum. The rates at which ice is frozen (accreted) to the base of the ice sheet are greatest at the shorelines, and the accreted ice layer is subsequently transported out of the lake. Using these new flow field and velocity measurements, we estimate the time for ice to traverse Lake Vostok to be 16,000-20,000 years. We infer that most Vostok ice analysed to date was accreted to the ice sheet close to the western shoreline, and is therefore not representative of open lake conditions. From the amount of accreted lake water we estimate to be exported along the southern shoreline, the lake water residence time is about 13,300 years.     

Similar response of labile and resistant soil organic matter pools to changes in temperature

Our understanding of the relationship between the decomposition of soil organic matter (SOM) and soil temperature affects our predictions of the impact of climate change on soil-stored carbon. One current opinion is that the decomposition of soil labile carbon is sensitive to temperature variation whereas resistant components are insensitive. The resistant carbon or organic matter in mineral soil is then assumed to be unresponsive to global warming. But the global pattern and magnitude of the predicted future soil carbon stock will mainly rely on the temperature sensitivity of these resistant carbon pools. To investigate this sensitivity, we have incubated soils under changing temperature. Here we report that SOM decomposition or soil basal respiration rate was significantly affected by changes in SOM components associated with soil depth, sampling method and incubation time. We find, however, that the temperature sensitivity for SOM decomposition was not affected, suggesting that the temperature sensitivity for resistant organic matter pools does not differ significantly from that of labile pools, and that both types of SOM will therefore respond similarly to global warming.     

Low sea level rise projections from mountain glaciers and icecaps under global warming

The mean sea level has been projected to rise in the 21st century as a result of global warming. Such projections of sea level change depend on estimated future greenhouse emissions and on differing models, but model-average results from a mid-range scenario (A1B) suggests a 0.387-m rise by 2100 (refs 1, 2). The largest contributions to sea level rise are estimated to come from thermal expansion (0.288 m) and the melting of mountain glaciers and icecaps (0.106 m), with smaller inputs from Greenland (0.024 m) and Antarctica (- 0.074 m). Here we apply a melt model and a geometric volume model to our lower estimate of ice volume and assess the contribution of glaciers to sea level rise, excluding those in Greenland and Antarctica. We provide the first separate assessment of melt contributions from mountain glaciers and icecaps, as well as an improved treatment of volume shrinkage. We find that icecaps melt more slowly than mountain glaciers, whose area declines rapidly in the 21st century, making glaciers a limiting source for ice melt. Using two climate models, we project sea level rise due to melting of mountain glaciers and icecaps to be 0.046 and 0.051 m by 2100, about half that of previous projections.     

Reduced nitrogen fixation in the glacial ocean inferred from changes in marine nitrogen and phosphorus inventories.

To explain the lower atmospheric CO2 concentrations during glacial periods, it has been suggested that the productivity of marine phytoplankton was stimulated by an increased flux of iron-bearing dust to the oceans. One component of this theory is that iron-an essential element/nutrient for nitrogen-fixing organisms-will increase the rate of marine nitrogen fixation, fuelling the growth of other marine phytoplankton and increasing CO2 uptake. Here we present data that questions this hypothesis. From a sediment core off the northwestern continental margin of Mexico, we show that denitrification and phosphorite formation-processes that occur in oxygen-deficient upwelling regions, removing respectively nitrogen and phosphorus from the ocean-declined in glacial periods, thus increasing marine inventories of nitrogen and phosphorus. But increases in phosphorus were smaller and less rapid, leading to increased N/P ratios in the oceans. Acknowledging that phytoplankton require nitrogen and phosphorus in constant proportions, the Redfield ratio, and that N/P ratios greater than the Redfield ratio are likely to suppress nitrogen fixation, we suggest therefore that marine productivity did not increase in glacial periods in response to either increased nutrient inventories or greater iron supply.     

Environmental changes and lake level fluctuation recorded by lakes on the plain in northern Xinjiang during the late Holocene

Xinjiang Autonomous Region is located in the arid area of westerly of China and there are many arguments about the changes of past temperature and moisture. Most of the lakes on the plain in northern Xinjiang are sealed lakes and terminal lakes. They can evidently reflect the changes in palaeoclimate. The palaeoenvironmental changes of some plain lakes in northern Xinjiang during the late Holocene will be analysed mainly based on the data of pollen, sedimentary facies, loss on ignition （LOI）, susceptibility and grain size from the Sichang Lake, Dongdaohaizi Lake and Aibi Lake. Results reveal an assembled pattern of temperature and moisture dominated by cold-wet and warm-dry. In addition, the impact factor will be discussed.     

Genetic contributions to stability and change in intelligence from childhood to old age

Understanding the determinants of healthy mental ageing is a priority for society today. So far, we know that intelligence differences show high stability from childhood to old age and there are estimates of the genetic contribution to intelligence at different ages. However, attempts to discover whether genetic causes contribute to differences in cognitive ageing have been relatively uninformative. Here we provide an estimate of the genetic and environmental contributions to stability and change in intelligence across most of the human lifetime. We used genome-wide single nucleotide polymorphism (SNP) data from 1,940 unrelated individuals whose intelligence was measured in childhood (age 11 years) and again in old age (age 65, 70 or 79 years). We use a statistical method that allows genetic (co)variance to be estimated from SNP data on unrelated individuals. We estimate that causal genetic variants in linkage disequilibrium with common SNPs account for 0.24 of the variation in cognitive ability change from childhood to old age. Using bivariate analysis, we estimate a genetic correlation between intelligence at age 11 years and in old age of 0.62. These estimates, derived from rarely available data on lifetime cognitive measures, warrant the search for genetic causes of cognitive stability and change.     

大别山北麓黄土古土壤磁组构参数特征与环境变化研究

文章对大别山北麓黄土-古土壤的磁化率各向异性进行了初步研究,结果表明:剖面上部的磁组构参数P、F、L平均值均低于底部的相应值;在磁组构参数F-L、P-q、P-F组合关系图上,上部样品的数据点集中分布于靠近坐标原点的区域,底部的多远离坐标原点;磁组构特征指示了上部为风成沉积而底部为水成沉积。     

基于GIS和统计的民勤绿洲地下水位模拟

提出了一种GIS与统计相结合的方法,根据民勤绿洲地下水观测井的水位数据,使用地统计学分析和时间序列分析模拟了绿洲地下水1984-2015年的时空分布.结果表明:在过去的18年中,民勤绿洲的地下水位呈持续下降的趋势.若不采取有效的治理措施,至2015年绿洲内75%以上区域的地下水埋深将超过30 m.空间上,从绿洲边缘至绿洲核心地下水埋深持续下降,沉降速度不断加快.     

印度洋赤道海岭钙质软泥天然热释光变化特征与冰川旋回关系

赤道东经90°海岭的MD81349活塞柱状岩芯包含300ka以来类型丰富的环境变化信息.作者应用天然热释光技术对岩芯的全样沉积物和浮游有孔虫壳体进行分析测定,首次得到与氧同位素分期呈良好对应关系的天然热释光变化曲线.实验数据表明,天然热释光的高强度区和低强度分别能够指示间冰期与冰期.初步分析显示,天然热释光强度变化在一定程度上与碳酸钙含量无关;在远洋型抱球虫软泥物质组成基本一致的情况下,其变化特征极有可能受到不同气候条件下形成的有孔虫壳体的晶体类型、晶格缺陷形式、杂质元素的控制.     

长江河口径流量与海平面上升对气候变化及人类活动的响应（英文）

气候变化和人类活动所导致的径流量变化和海平面上升都是数值模式中重要的边界条件。因此,为了得到合适的边界条件,本文给出2030、2050和2100年气候变化和人类活动影响下长江径流量和海平面上升的变化情况.考虑到三峡工程于2003年坝体合拢,利用大通站1865至2002年的历史径流量资料,发现利用资料外推获得的径流量变化率与气候模型所得结果近似,得到在2030、2050和2100年1、2月平均径流量在气候变化影响下分别为12348、12683和13 522 m~3·s~(-1).在过去20年,长江河口绝对海平面上升率约为2.5 mm·a~(-1).根据海平面变化资料分析预报模型,2012年至2030、2050和2100年绝对海平面分别上升49.1、148.1和395.6mm.长江河口的盐水入侵数值模拟需考虑三峡水库和南水北调对入海径流量的影响.同时,相对海平面变化需要考虑地壳下沉和地基沉降.本文给出各个预估时期上述内容的量值.     

Changes in annual accumulation retrieved from Geladaindong ice core and its relationship to atmospheric circulation over the Tibetan Plateau

Annual accumulation records covering 1935 to 2004 were reconstructed using Geladaindong ice core in the source of Yangtze River. A significant positive correlation between annual accumulation and precipitation from nearby meteorological stations was found, suggesting ice core accumulation could be taken as a precipitation proxy in the region. In the past 70 years, precipitation in the Geladaindong region was low from 1930s to early 1960s, and the lowest value occurred in the later 1950s. Since 1960s, precipitation increased dramatically and reached the maximum around 1980s, then decreased slightly in 1990s. By using Mann-Kendall rank statistical test method, a change point for precipitation was determined in 1967. Analysis of the atmospheric circulation over the Tibetan Plateau suggested that, compared with the southwest wind during the low precipitation period （before 1967）, it extended about 2 latitudes northward during high precipitation period （after 1967）. Moreover, during the high precipitation, the trough over the Bal Karshi Lake was also enhanced, and both the meridional wind and vapor transporting displayed a remarkable aggrandizement.