Migration of a Late Cretaceous fish

Late Cretaceous sediments from the Western Interior of North America yield exceptionally well preserved fossils that serve as proxies for the rapidly changing climate preceding the Cretaceous/Tertiary boundary (about 67-65 Myr ago). Here we reconstruct the ontogenetic history of a Maastrichtian-age fish, Vorhisia vulpes, by using the carbon, oxygen and strontium isotope ratios of four aragonite otoliths collected from the Fox Hills Formation of South Dakota. Individuals of V. vulpes spawned in brackish water (about 70-80% seawater) and during their first year migrated to open marine waters of the Western Interior Seaway, where they remained for 3 years before returning to the estuary, presumably to spawn and die. The mean delta(18)O from the marine growth phase of V. vulpes yields a seawater temperature of 18 degrees C, which is consistent with leaf physiognomy and general-circulation-model temperature estimates for the Western Interior during the latest Maastrichtian.     

棕榈在北方不同生态环境下越冬栽培适应性的生理研究

在设置的不同生态环境小区内栽培棕榈，通过分析越冬栽培期间不同小区内的温度、风速及空气相对湿度等气候因子，观察植株寒害反应及来年生长状况，并结合植株叶片组织水分、可溶性糖及可溶性蛋白的质量分数和过氧化物酶(POD)及超氧歧化酶(SOD)比活性的测定，揭示了棕榈北方越冬栽培适应性的生理基础和伤害发生的可能机制。结果表明，背风向阳的生态环境、一定程度的低温、大风，引发叶片组织中水的质量分数降低、渗透调节物质可溶性糖和可溶性蛋白等的质量分数以及膜的保护酶POD和S0D的比活性提高，这有利于植株抵御寒害，安全越冬。自然裸地生态环境内的低温，尤其是大的风速加之较低的空气相对湿度，使叶片组织的POD和SOD比活性下降、质膜透性增强，叶片呈现生理干旱的伤害性特征，且部分植株生长点部位严重受害，翌年死亡。冬季寒潮所造成的极端低温以及大风引发的生理干旱，是棕榈树在北方户外越冬的限制因子。     

埋藏古木树轮碳、氢、氧同位素研究与古气候重建

树轮作为自然档案的一种,其同位素研究对探讨全球气候和环境变化具有重要的意义.文章系统地介绍了树轮碳、氢、氧同位素的分馏原理, 研究方法以及纤维素的提取等.研究表明,树轮同位素作为环境变化的示踪剂,是古环境再造和了解现代环境气候变化的一个强有力工具.尤其是在过去全球变化(PAGES)研究中,埋藏古木纤维素中的碳、氢、氧同位素分析已成为环境演化研究的主要量化手段.另外,对于中国这样典型的季风气候国家,开展树轮稳定同位素随季节性变化的研究具有重要的意义. 我国在树轮研究方面起步较晚,研究方法和研究内容上也比较简单,还存在不小差距,既要进一步积累基础资料,又要做区域对比,加强与相关学科的交叉研究.     

Past temperature and delta18O of surface ocean waters inferred from foraminiferal Mg/Ca ratios

Determining the past record of temperature and salinity of ocean surface waters is essential for understanding past changes in climate, such as those which occur across glacial-interglacial transitions. As a useful proxy, the oxygen isotope composition (delta18O) of calcite from planktonic foraminifera has been shown to reflect both surface temperature and seawater delta18O, itself an indicator of global ice volume and salinity. In addition, magnesium/calcium (Mg/Ca) ratios in foraminiferal calcite show a temperature dependence due to the partitioning of Mg during calcification. Here we demonstrate, in a field-based calibration experiment, that the variation of Mg/Ca ratios with temperature is similar for eight species of planktonic foraminifera (when accounting for Mg dissolution effects). Using a multi-species record from the Last Glacial Maximum in the North Atlantic Ocean we found that past temperatures reconstructed from Mg/Ca ratios followed the two other palaeotemperature proxies: faunal abundance and alkenone saturation. Moreover, combining Mg/Ca and delta18O data from the same faunal assemblage, we show that reconstructed surface water delta18O from all foraminiferal species record the same glacial-interglacial change--representing changing hydrography and global ice volume. This reinforces the potential of this combined technique in probing past ocean-climate interactions.     

Strong coherence between solar variability and the monsoon in Oman between 9 and 6 kyr ago

Variations in the amount of solar radiation reaching the Earth are thought to influence climate, but the extent of this influence on timescales of millennia to decades is unclear. A number of climate records show correlations between solar cycles and climate, but the absolute changes in solar intensity over the range of decades to millennia are small and the influence of solar flux on climate is not well established. The formation of stalagmites in northern Oman has recorded past northward shifts of the intertropical convergence zone, whose northward migration stops near the southern shoreline of Arabia in the present climate. Here we present a high-resolution record of oxygen isotope variations, for the period from 9.6 to 6.1 kyr before present, in a Th-U-dated stalagmite from Oman. The delta18O record from the stalagmite, which serves as a proxy for variations in the tropical circulation and monsoon rainfall, allows us to make a direct comparison of the delta18O record with the Delta14C record from tree rings, which largely reflects changes in solar activity. The excellent correlation between the two records suggests that one of the primary controls on centennial- to decadal-scale changes in tropical rainfall and monsoon intensity during this time are variations in solar radiation.     

Climatic changes documented by stable isotopes of sedimentary carbonate in Lake Sugan, northeastern Tibetan Plateau of China, since 2 kaBP

Lake Sugan at the northern edge of the Qaidam Basin was selected as the research object. The temporal sequence of sedimentary cores retrieved from Lake Sugan since 2 kaBP was reconstructed using the ^210Pb, AMS 14C and conventional 14C dating methods. Carbon and oxygen isotopes of carbonate in the fine-grained lake sediments were analysed. Combined with the changes of 8180 values of surface water and air temperature observation data in the study area, it might be thought that the δ^18O value of the carbonate indicates effective moisture, and the changes in δ^13C values are related to annual freeze-up duration of the lake and indirectly indicate air temperature changes in winter half year. From the above, the sequence of climatic changes in the region since 2 kaBP was established. The climatic changes experienced five stages： Warm-dry climate during 0-190 AD： cold-dry climate during 190-580 AD; warm-dry climate during 580-1200 AD （MWP）; cold-wet climate during 1200-1880 AD （LIA）; cold-dry climate during 1880-1950 AD： and climate warming since 1950s. The air temperature changes in winter half year reflected by carbon isotope since 2 kaBP are in good agreement with the historical literature records and other geologic records, which shows that the climate changes recorded by the stable isotopes from Lake Sugan since 2 kaBP are of universal significance.     

北京大学未名湖沉积物中公元1747年以来气候变化的氧碳同位素记录

对北京大学未名湖底泥层做了²¹⁰Pb计年法和¹³⁷Cs时标法定年以及氧碳同位素分析。结果表明厚度约50cm的底泥层形成于公元1747—1997年之间,湖泥中碳酸盐的氧碳同位素组成和有机物含量记录了北京地区公元1747年以来的气候变化：1866年以前冬季风盛行,气候比较寒冷干燥;1887年以后夏季风盛行,气候比较温暖湿润,其中1907—1926年是近250年以来气候最为温暖湿润的时期;介于两者之间的1867—1886年是气候急剧转型的时期,也是自然灾害频繁出现的时期。     

基于暖体假人实验的防刺服热阻和湿阻研究

为有效提高防护服装舒适性、降低人员体力消耗、加快人体防护装备研制与开发,开展了利用出汗暖体假人测量防刺服在不同环境下的热阻与湿阻特性的研究.根据国际标准,假人只适用于常温环境下服装的热阻和湿阻测量.对原有热阻模型进行修正,结合热电偶测量方法以及暖体假人测量技术,实现高温下防刺服热阻和湿阻测量.在温、湿度可控制的气候室内,设置不同环境工况,获得两套防刺服的热阻和湿阻特性,比较了不同防刺基板材料对防刺服热阻和湿阻的影响,以及防刺服不同部位热阻和湿阻的差异.实验结果表明,防刺服热阻随着温度升高而降低;而湿阻随着环境温度升高而增大,随着湿度增加而减少.      

影响新疆阜康荒漠地区红砂光合日变化因素的分析

目的 研究新疆阜康荒漠区域优势植物红砂（Reaumuria soongorica）光合及其影响因子的日变化，分析蒸腾速率、光合有效辐射、空气温度、气孔导度、相对湿度、叶面温度、胞间CO2浓度和空气CO：浓度对光合速率的影响。方法利用CI-301 CO2气体分析仪，测定光合及其影响因子的日变化，并进行相关性和多重线性回归分析。结果光合速率日变化形成典型的双峰型；蒸腾速率的日变化曲线呈双峰型；光合有效辐射、空气温度日变化和叶面温度的日变化曲线相近，在午后均呈逐步降低趋势；气孔导度与生境相对湿度的日变化为先下降，然后保持在一定的水平上；水分利用率全天递减。空气CO2浓度、空气温度、相对湿度及叶面温度和气孔导度对红砂光合速率具有显著的影响。结论红砂光合速率日变化曲线形成典型的双峰型，温度是影响红砂光合特性的重要因子之一，气孔因素则是导致其光合速率下降的决定因素。     

A humid climate state during the Palaeocene/Eocene thermal maximum

An abrupt climate warming of 5 to 10 degrees C during the Palaeocene/Eocene boundary thermal maximum (PETM) 55 Myr ago is linked to the catastrophic release of approximately 1,050-2,100 Gt of carbon from sea-floor methane hydrate reservoirs. Although atmospheric methane, and the carbon dioxide derived from its oxidation, probably contributed to PETM warming, neither the magnitude nor the timing of the climate change is consistent with direct greenhouse forcing by the carbon derived from methane hydrate. Here we demonstrate significant differences between marine and terrestrial carbon isotope records spanning the PETM. We use models of key carbon cycle processes to identify the cause of these differences. Our results provide evidence for a previously unrecognized discrete shift in the state of the climate system during the PETM, characterized by large increases in mid-latitude tropospheric humidity and enhanced cycling of carbon through terrestrial ecosystems. A more humid atmosphere helps to explain PETM temperatures, but the ultimate mechanisms underlying the shift remain unknown.     

Temperature variations in the past 6000 years inferred from δ18O of peat cellulose from Hongyuan, China

Trends of the temperature variations recorded in δ18O in Hongyuan peat cellulose are similar to those recorded in δ 18O of Jinchuan peat cellulose and inδ18O of Dunde ice core. Climate events have been identified to be globallyhomogeneous. Two notable climate transition periods have been detected in the past 6000 years, namely 4000 aBP with climate shifting from cold to warm and 1500aBP with climate shifting from warm to relatively cold. Power spectrum analysiswas performed to investigate the periodical signals in the δ18O time series. Typical periodicities of 1200-1087 a, 752 a, 444 a, 325 a, 213 a, 127-123 a, 88a, 79 a were discovered, indicating an integrated influence on Hongyuan climatefrom solar, monsoon and ocean activities. Solar forcing has been addressed to be the main driving forcing of Hongyuan climate.     

短期区域气候预测系统及回报试验

为了提高短期区域气候预测准确率,针对我国大陆区域及周边海域,通过国家气候中心全球海气耦合模式嵌套一个区域大气-海洋耦合模式,建立了一套短期区域气候预测系统。利用该预测系统对2006-2011年逐年7月的气候特征进行了回报试验,对比分析了区域模式相对于全球模式预测高空形势场的差异,评估了预测系统对地面温度和降水的预测能力。试验表明:同化后,初估场质量显著提高;区域模式在预测高空形势场方面优于全球模式;相对于单独的大气模式,海气耦合模式在预测中低空的温度和湿度方面有一定的改善;系统对地面气温和降水均具有一定的预报能力,其中降水预测稍好。     

Low-latitude seasonality of Cretaceous temperatures in warm and cold episodes

The Cretaceous period is generally considered to have been a time of warm climate. Evidence for cooler episodes exists, particularly in the early Cretaceous period, but the timing and significance of these cool episodes are not well constrained. The seasonality of temperatures is important for constraining equator-to-pole temperature gradients and may indicate the presence of polar ice sheets; however, reconstructions of Cretaceous sea surface temperatures are predominantly based on the oxygen isotopic composition of planktonic foraminifera that do not provide information about such intra-annual variations. Here we present intra-shell variations in delta18O values of rudist bivalves (Hippuritoidea) from palaeolatitudes between 8 degrees and 31 degrees N, which record the evolution of the seasonality of Cretaceous sea surface temperatures in detail. We find high maximum temperatures (approximately 35 to 37 degrees C) and relatively low seasonal variability (< 12 degrees C) between 20 degrees and 30 degrees N during the warmer Cretaceous episodes. In contrast, during the cooler episodes our data show seasonal sea surface temperature variability of up to 18 degrees C near 25 degrees N, comparable to the range found today. Such a large seasonal variability is compatible with the existence of polar ice sheets.     

Distribution of <Emphasis Type="Italic">δ</Emphasis><Superscript>18</Superscript>O in surface snow along a transect from Zhongshan Station to Dome A,East Antarctica

Surface snow samples were collected during the 14th (1997/1998) and 24th (2007/2008) Chinese National Antarctica Research Expeditions along a transect from Zhongshan Station to Dome A. The stable oxygen isotope ratios of these samples were measured to investigate their relationships with temperature and geographical parameters (latitude, longitude, altitude and distance to the coast). The results reveal a strong positive correlation (R=0.945) between δ¹⁸O and mean annual temperature, with a gradient of 0.84‰°C ^–1, which is a little higher than that in Terre Adelie Land. Regression analyses also show that the δ¹⁸O of surface snow is strongly correlated with distance to the coast (R=0.942), latitude (R=0.942), and altitude (R=0.941). But no significant correlation was found between δ¹⁸O and longitude in study area. Altitude should be the most important factor influencing the δ¹⁸O distribution because of distinctive topography. The δ¹⁸O-altitude and T-altitude gradients along this transect are determined to be –1.1‰/100 m and 1.31°C/100 m, respectively.     

Climatic significance of stable carbon isotope in tree rings of Abies spectabibis in southeastern Tibet

The annually cross-dated stable carbon isotope of tree-ring a-cellulose of Abies spectabibis collected from the southeastern Tibetan Plateau is used to examine its rela-tionship with climatic parameters. The residual D13C series in treerings is constructed after removing the effects of age trend and rising CO2. We found a close relationship between D13C in tree rings and the relative humidity of September—November of the previous year measured at the nearby Ny-ingchi Meteorological Station, albeit a strong 搇agged effect? Thus we developed a transfer function to reconstruct the autumn relative humidity for the Nyingchi region, which explained 37.9% of the total variance (p < 0.001). Our results suggest a high frequency and moderate amplitude variance of the relative humidity before 1800, and the variance re-versed afterwards.     

Coupling of surface temperatures and atmospheric CO2 concentrations during the Palaeozoic era

Atmospheric carbon dioxide concentrations seem to have been several times modern levels during much of the Palaeozoic era (543-248 million years ago), but decreased during the Carboniferous period to concentrations similar to that of today. Given that carbon dioxide is a greenhouse gas, it has been proposed that surface temperatures were significantly higher during the earlier portions of the Palaeozoic era. A reconstruction of tropical sea surface temperatures based on the delta18O of carbonate fossils indicates, however, that the magnitude of temperature variability throughout this period was small, suggesting that global climate may be independent of variations in atmospheric carbon dioxide concentration. Here we present estimates of sea surface temperatures that were obtained from fossil brachiopod and mollusc shells using the 'carbonate clumped isotope' method-an approach that, unlike the delta18O method, does not require independent estimates of the isotopic composition of the Palaeozoic ocean. Our results indicate that tropical sea surface temperatures were significantly higher than today during the Early Silurian period (443-423 Myr ago), when carbon dioxide concentrations are thought to have been relatively high, and were broadly similar to today during the Late Carboniferous period (314-300 Myr ago), when carbon dioxide concentrations are thought to have been similar to the present-day value. Our results are consistent with the proposal that increased atmospheric carbon dioxide concentrations drive or amplify increased global temperatures.     

Acclimatization of soil respiration to warming in a tall grass prairie.

The latest report by the Intergovernmental Panel on Climate Change (IPCC) predicts a 1.4-5.8 degrees C average increase in the global surface temperature over the period 1990 to 2100 (ref. 1). These estimates of future warming are greater than earlier projections, which is partly due to incorporation of a positive feedback. This feedback results from further release of greenhouse gases from terrestrial ecosystems in response to climatic warming. The feedback mechanism is usually based on the assumption that observed sensitivity of soil respiration to temperature under current climate conditions would hold in a warmer climate. However, this assumption has not been carefully examined. We have therefore conducted an experiment in a tall grass prairie ecosystem in the US Great Plains to study the response of soil respiration (the sum of root and heterotrophic respiration) to artificial warming of about 2 degrees C. Our observations indicate that the temperature sensitivity of soil respiration decreases--or acclimatizes--under warming and that the acclimatization is greater at high temperatures. This acclimatization of soil respiration to warming may therefore weaken the positive feedback between the terrestrial carbon cycle and climate.     

Oxygen isotope variation in the water cycle of the Yamzho lake Basin in southern Tibetan Plateau

Given the potential use of stable isotope in the paleoclimate reconstruction from lacustrine records as well as in the local hydrology cycle, it is crucial to understand the processes of stable isotope evolution in catchment in the Tibetan Plateau region. Here we present a detailed study on the water oxygen isotope based on 2 years observation including precipitation, river water and lake water in the Yamzho Lake, south of the Tibetan Plateau. Temporal variation of local precipitation 5180 shows an apparent ＂monsoon cycle＂. In monsoon season, 5180 in waters is lower. In non-monsoon season, δ^18O in precipitation and lake water is higher and higher river δ^18O exists in spring, probably reflecting the effect of land surface evaporation, together with the higher δ^18O values in spring precipitation. It is also found that the surface lake water δ^18O varies seasonally and annually. The lower lake water δ^18O in the late summer is apparently related to the summer monsoon precipitation. The mean δ^18O value of lake water in 2007 is 1.2‰ higher than that in 2004, probably due to the less monsoon precipitation in summer of 2007, as can be confirmed from the precipitation data at the Langkazi meteorological data. It is also found that an obvious shift of vertical lake water δ^18O reflects the fast mixture of lake water. δ^18O values of lake water are over 10‰ higher than those of precipitation and river water in this region due to the evaporation fractionation. The modeled results show that the evaporation process of the lake water is sensitive to relative humidity, and the present lake water δ^18O reflects a relative humidity of 51% in the Yamzho Lake. It shows that the lake will take 30.5 years to reach present lake water δ^18O given a large shift in the input water δ^18O. The modeled results also reveal that surface lake water temperature and inflow δ^18O have slight effect on the isotopic balance process of lake water in the Yamzho Lake.     

济南市旅游气候的舒适度研究

根据济南市气象站1951～2000年气象资料,分析与人体舒适度有关的气温、相对湿度、风速等气象要素的基本气候特征,研究济南市人体舒适度的时空分布特征,进而对济南市的旅游人体舒适度进行评价,探讨各气象要素对不同季节舒适度的影响以及舒适度的变化趋势,分析济南市最佳旅游时间.     

Process-based modeling analyses of Sabina przewalskii growth response to climate factors around the northeastern Qaidam Basin

Sabina przewalskii is the longest living endemic tree species in the northeastern Tibetan Plateau,and has been widely employed in tree ring based climate research in China.However,most dendroclimatic reconstructions have been primarily based on empirical relationships between tree growth and climate factors identified by statistical assessment.To date,the physiological relationships between tree growth and their limiting climate factors have not been properly assessed.Here,we simulated the physiological response of Sabina przewalskii tree growth to major limiting climate factors based on the Vaganov-Shashkin (VS) model.The VS modeled results validated the relationships between tree ring and climate factors constructed by statistical models,both approaches suggesting that precipitation during the early growing season,especially in May and June,has significant effect on tree growth,while temperature mainly affects tree growth by warming-induced drought and by extending the growing season.Under current and projected climate scenarios,our modeling results predict an increase in radial growth of Sabina przewalskii around the Qaidam Basin,with the potential outcome that regional forests will increase their capacity to sequester carbon.