Variation of Stable Isotopes in Surface Snow along a Traverse from Coast to Plateau's interior in East Antarctica and Its Climatic Significance

The variations of stable water isotopes of surface snow in east Antarctic Ice Sheet, are discussed by a total of 251 samples, which were taken along a 330 km traverse from Zhongshan Station to the outer edge of the Antarctic plateau and from four snow pits excavated along the route. Analyzing results of the samples showed the expected linear relationship between the parameters ?D and ?18O with slope S1 and intercept d1. When the data set was examined using a sliding window with a width of 5 samples, it was found that there were two areas with different ratios of S1 and d1. The boundary between these two areas occurred at an elevation of about 2,000 m, suggesting two different sources of water vapour. Nearly half (47%) of the fresh-snow samples had negative deuterium excess (d=?D? 8?18O) values, but few of the snow pit samples did, suggesting that variations of ? are quickly smoothed by isotopic diffusion in the near-surface firn. Analysis of the phase relationship between ?D and deuterium excess in the snow pit stratigraphies showed that they were mostly in phase from Jan. 1994 to Sept. 1995, but mostly out of phase from Sept. 1995 to Jan. 1997.

Mg/Ca Variation in Planktonic Foraminiferal Tests:Assessing Influence of Salinity and Diagenetic Carbonate Dissolution for Reconstruction of Palaeo-seawater Temperature

Over the past decade,the Mg/Ca ratio in foraminiferal tests has emerged as a valuable paleotemperature proxy.In this study we describe the application of the Mg/Ca paleothermometer with the aim of illustrate its use in the Mediterranean Basin.We value the influence of the salinity and diagenetic carbonate processes besides temperature as an important environmental factor controlling the foraminiferal Mg/Ca.For this purpose 3 species of

Towards a better understanding of pathways of multiple co-occurring erosion processes on global cropland

Soil erosion is a complex process involving multiple natural and anthropic agents,causing the deterio-ration of multiple components comprising soil health.Here,we provide an estimate of the spatial pat-terns of cropland susceptibility to erosion by sheet and rill,gully,wind,tillage,and root crops harvesting and report the co-occurrence of these processes using a multi-model approach.In addition,to give a global overview of potential future changes,we identify the locations where these multiple concurrent soil erosion processes may be expected to intersect with projected dry/wet climate changes by 2070.Of a modelled 1.48 billion hectares(B ha)of global cropland,our results indicate that 0.56 B ha(-36%of the total area)are highly susceptible(classes 4 and 5)to a single erosion process,0.27 B ha(-18%of the total area)to two processes and 0.02 B ha(1.4%of the total area)to three or more processes.An estimated 0.82 B ha of croplands are susceptible to possible increases in water(0.68 B ha)and wind(0.14 B ha)erosion.We contend that the presented set of estimates represents a basis for enhancing our founda-tional knowledge on the geography of soil erosion at the global scale.The generated insight on multiple erosion processes can be a useful starting point for decision-makers working with ex-post and ex-ante policy evaluation of the UN Sustainable Development Goal 15(Life on Land)activities.Scientifically,this work provides the hitherto most comprehensive assessment of soil erosion risks at the global scale,based on state-of-the-art models.

雪冰黑碳的气候效应研究

黑碳气溶胶沉降到雪冰表面后,使雪冰反照率降低从而导致气候增暖的效应日益引起人们的关注。首先提出了雪冰黑碳的气候效应问题,然后介绍了国际上相关研究的进展,并提出加强此项研究对提高中国区域气候认识的意义。

印度尼西亚弗洛勒斯海LGM以来的古海洋学记录

弗洛勒斯海位于印度尼西亚穿越流通道上,它的古海洋学特征对于理解LGM以来穿越流活动历史,及其与全球气候变化的关系具有重要意义.通过对弗洛勒斯海SHI9011岩心δ18O、δ13C、浮游有孔虫组合及碳酸盐含量等古海洋学记录的研究,认为研究区沉积速率不高,生物生产力却并不低于高沉积速率的近陆地区.冰期时海平面下降,陆源物质输入量增加,使得古生产力上升.冰消期终止期IA海平面快速上升,陆源营养物质供应减少,同时穿越流活动增强,抑制了下部水体向上运动,古生产力开始下降.8～6 ka前后,强烈的东南季风使得研究区上升流活动增强.

爪哇海末次冰盛期以来的季风与穿越流活动记录

文章通过SHl9034岩芯氧同位素曲线、AMS ^14C测年、浮游有孔虫组合及其所反映的温盐变化特点，并与爪哇海北部的SHl9006岩芯对比研究，获得如下认识：末次冰期2l～15kaB．P．阶段，爪哇海区东南季风强而西北季风微弱，气候冷干，混合层薄，生物生产力高；15～10kaB．P．和10～7kaB．P．阶段由于海平面迅速上升，望加锡海峡和龙目海峡通道变宽，出现较强的表层穿越流活动；早全新世东南与西北季风都有增强，说明当时研究区气候有着更强的季节性；7～3kaB．P．阶段，爪哇海北部的穿越流主要在温跃层水中传输，到达爪哇上升流区时，上升至表层，使得混合层增厚，同时也抑制了上升流活动；约3kaB．P．以来，研究区穿越流活动表现与现代相近的性质，主要在温跃层水中传输。

印度尼西亚多岛海末次冰期最盛期以来的穿越流活动

印度尼西亚穿越流是西太平洋和印度洋之间热量传输的重要载体 ,穿越流的活动由潜在地影响ElNino和季风现象进而影响到全球气候变化 .通过对爪哇海SHI90 0 6岩心LGM以来氧同位素、有孔虫与CaCO3 沉积量、浮游有孔虫浅层水种与深层水种比值反映的古温跃层变化等的研究 ,得出结论 :研究区末次冰期氧同位素 2期穿越流活动微弱 ,冰后期穿越流活动增强 ;特别是冰消期终止期ⅠA,穿越流活动由弱迅速增强 ,是冰川消融、海平面上升 ,印度尼西亚岛弧古海水通道开放的结果 .

The B/Ca and Cd/Ca of a subsurface-dwelling foraminifera Pulleniatina obliquiloculata in the tropical Indo-Pacific Ocean: implications for the subsurface carbonate chemistry estimation

Pulleniatina obliquiloculata shells from 16 core-top samples from the tropical Indo-Pacific Oceans are analyzed for the ratios of boron and cadmium to calcium(B/Ca and Cd/Ca). The B/Ca ratios show a very weak positive relationship with [B(OH)_4^-] and the dissolved carbonate species at the apparent calcification depth of P.obliquiloculata. The boron partition coefficients(K_D) between P. obliquiloculata B/Ca and seawater[B(OH)_4^-]/[HCO_3^-] distribute around 1.1×10^(-3)-1.3×10^(-3) with a mean value of(1.19±0.12)×10^(-3),and are significantly related to the nutrient concentration, especially phosphate. The lack of any clear correlation between the P. obliquiloculata B/Ca and seawater carbonate chemical parameters suggests that the physiochemical controls on boron incorporation are masked by the complexity of natural seawater condition. But the significant dependence of Ku on nutrient may likely be explained by a nutrient related growth-rate effect. Cd/Ca of P.obliquiloculata shows significant correlation with seawater phosphate concentration, and its partition coefficients(D_(cd)) are significantly related to temperature. A first-principle methodology of P. obliquiloculata B/Ca is applied;with the aid of Cd/Ca as a phosphate proxy and a constraint on K_D, to estimating sea water carbonate chemistry(e.g., pH). The results are fairly promising and allow us to propose the possibility to apply the combination of B/Ca and Cd/Ca proxies(and also Mg/Ca and δ^(18)O for estimating temperature and salinity) for the paleoreconstruction of seawater carbonate chemistry.

Map of Mafic Dyke Swarms and Related Units of Russia and Adjacent Regions

Work is currently underway to produce a map in Arc GISTM 10 of the mafic dyke swarms and related units(volcanics,sills and layered intrusions)of Russia and adjacent regions at a scale of 1:5,000,000.Over the past

Saturation-excess overland flow in the European loess belt:An underestimated process?

A major challenge in runoff and soil erosion modelling is the adequate representation of the most relevant processes in models while avoiding over parameterization.In the European loess belt,pro-gressive soil crusting during rainfall events,resulting in infiltration-excess runoff,is usually considered the dominant process generating runoff on catchments covered with silty soils.Saturation-excess may also occur and affect their runoff and erosion behavior.However,saturation-excess runoff occurrence and quantification have rarely been performed and is usually not taken into account when modelling runoff and erosion in these environments.Accordingly,a continuous simulation of the Austreberthe catchment(214 km^(2)),located in the European loess belt(Normandy,France),was conducted with the new Water and Sediment(WaterSed)model over 12 years,corresponding to more than 780 individual rainfall events,at a 25 m spatial resolution.The inter-annual variability of runoff and erosion was closely linked to the number of intense events per year and their distribution through the year.The model was properly calibrated over a representative set of 35 rainfall events,considering either infiltration-excess and/or saturation-excess runoff.It was also able to reproduce the measured runoff volume for most of the monitoring period.However,the three years with most rainfall were adequately modelled only including saturation-excess runoff.An analysis performed at the seasonal scale revealed that saturation was modelled in the catchment during almost all of the modelling period,suggesting the importance of this often overlooked process in current modelling attempts.

Mapping global forest biomass and its changes over the first decade of the 21st century

Forests played an important role in carbon sequestration during the past two decades. Using a model tree ensemble method(MTE) to regress the seven reflectance bands of EOS-Terra-MODIS satellite data against country level forest biomass carbon density(BCD) of 2001–2005 provided by United Nations' s Forest Resource Assessment(FRA), we developed a global map of forest BCD at 1 km×1 km resolution for both 2001–2005 and 2006–2010. For 2006–2010, the total global forest biomass carbon stock is estimated as 279.6±7.1 Pg C, and the tropical forest biomass carbon stock is estimated as 174.4±5.4 Pg C. During the first decade of the 21 st century, we estimated an increase of global forest biomass of 0.28±0.75 Pg C yr^(-1). Tropical forest biomass carbon stock slightly decreased(-0.31±0.60 Pg C yr^(-1)); by contrast, temperate and boreal forest biomass increased(0.58±0.28 Pg C yr^(-1)) during the same period. Our estimation of the global forest biomass carbon stock and its changes is subject to uncertainties due to lack of extensive ground measurements in the tropics, spatial heterogeneity in large countries, and different definitions of forest. The continuously monitoring of forest biomass carbon stock with MODIS satellite data will provide useful information for detecting forest changes.

Annual Maps of Forests in Australia from Analyses of Microwave and Optical Images with FAO Forest Definition

The Australian governmental agencies reported a total of 149 million ha forest in the Food and Agriculture Organization of the United Nations(FAO)in 2010,ranking sixth in the world,which is based on a forest definition with tree height>2 meters.Here,we report a new forest cover data product that used the FAO forest definition(tree cover>10%and tree height>5 meters at observation time or mature)and was derived from microwave(Phased Array type L-band Synthetic Aperture Radar,PALSAR)and optical(Moderate Resolution Imaging Spectroradiometer,MODIS)images and validated with very high spatial resolution images,Light Detection and Ranging(LiDAR)data from the Ice,Cloud,and land Elevation Satellite(ICESat),and in situ field survey sites.The new PALSAR/MODIS forest map estimates 32 million ha of forest in 2010 over Australia.PALSAR/MODIS forest map has an overall accuracy of~95%based on the reference data derived from visual interpretation of very high spatial resolution images for forest and nonforest cover types.Compared with the canopy height and canopy coverage data derived from ICESat LiDAR strips,PALSAR/MODIS forest map has 73%of forest pixels meeting the FAO forest definition,much higher than the other four widely used forest maps(ranging from 36%to 52%).PALSAR/MODIS forest map also has a reasonable spatial consistency with the forest map from the National Vegetation Information System.This new annual map of forests in Australia could support cross-country comparison when using data from the FAO Forest Resource Assessment Reports.

冲绳海槽200ka的孢粉记录及冰期-间冰期旋回古环境重建

本文对冲绳海槽中部MD982194钻孔29.78m近200kaBP的岩芯进行了孢粉研究.结果表明,孢粉组合主要表现为裸子植物与草本植物花粉之间的交替.带气囊类的松属、铁杉在间冰期的1,3,5和7氧同位素期显著增高,而草本则在冰期阶段占优,两者的含量变化显示出对冰期-间冰期环境变化的敏感响应.本钻孔发现莎草科花粉在冰期阶段含量大幅度增加,伴随蒿属、禾本科、菊科、藜科和淡水藻类的显著升高.它们与轨道尺度的海平面变化呈现十分吻合的负相关关系.草本花粉总量的周期性变化可以作为该区域海平面变化的替代性指标.末次盛冰期的海平面下降导致陆地与冲绳海槽的距离大幅缩小,源于长江的物质随河流进入大陆架后因流速急剧降低发生沉降,导致上游物质难以被远距离搬运到海槽.因此,冰期阶段冲绳海槽的孢粉物质可能主体来自于大陆架前缘的地表植被,而间冰期带气囊类花粉的比例增大与海岸距离较远和风力搬运物质的比例增加有关.钻孔的孢粉组分更替与气候变化也有显著的对应关系,反映出氧同位素7,5和1期木本含量高,并与东亚夏季风增强和降雨量增大有关.其中MIS5.3,MIS5.1和MIS3.3段的松属花粉峰值可能与轨道和亚轨道周期的地表太阳辐射和季风增强有密切联系.研究认为,盛冰期的东海陆架平原的气温和降雨量都有较明显的下降,但低海面时期裸露的大陆架平原可能并非由半干旱的地带性草原所覆盖,而是以疏林草地及密布的隐域性植被(河流补给淡水湖沼和湿地)组成.海平面变化引起的海岸距离伸缩和源区气候变化对陆源物质通量和孢粉组分更替起到联合制约的作用,而冲绳海槽冰期-间冰期尺度的海岸线距离变化在孢粉信号中的表现要明显强于陆源区域的气候变化.

A^200 ka pollen record from Okinawa Trough:Paleoenvironment reconstruction of glacial-interglacial cycles

Pollen analysis was carried out on the Core MD982194 of 29.78 m retrieved from the Middle Okinawa Trough which was dated as old as -200 ka BP. The results revealed that pollen assemblages mainly presented an alternation of coniferous and herb pollen. The coniferous saccate pollen, principally Pinus and Tsuga, predominated in most parts of the core, especially highlighted in the interstadial stages including MIS 1,3, 5 and MIS7, whereas the herb pollen significantly increased in the gla- cial periods. Thus the pollen flora and their percentages showed the sensitive changes under the influence of ice volume during the glacial and interglacial periods. Our record from this core has first documented that the percentage of Cyperaceae was ex- tremely high in the glacial stages with a notable increase in Artemisia, Gramineae, Asteraceae, Cbenopodiaceae, and freshwa- ter algae, which can be used as a proxy for sea-level change at the study site because of their close negative correlation of the orbital-scale changes in sea level. The distance between the continental coastline and the Okinawa Trough has deeply short- ened due to the sea-level drop in the LGM. As a result, the sediment materials from Yangtze River were extensively deposited on the flat, exposed continental shelf owing to the rapid decline of river flow speed, leading to that pollen grains from Okinawa Trough are derived mainly from the flat coastal vegetation of exposed continental shelf at glacial stages. Changes of pollen as- semblage were consistent with the variation of temperature and humidity, which showed that the percentage of arboreal pollen was highly augmented at MIS 7, 5 and MIS 1, corresponding to the strengthening of the East Asian summer monsoon and in- creasing of rainfall. Moreover, the peak of Pinus percentage in MIS 5.3, 5.1 and MIS 3.3 may be closely linked by orbital and sub-orbital cycles of solar radiation and monsoonal variability. The present study of core MD981294 implied lower tempera- ture and precipitation during the lowest sea-level stage （LGM）, and more visibly testified that the vegetation of the flat plain on the exposed continental shelf was dominated by intrazonal communities such as halophyte grasslands and freshwater wetlands instead of zonal steppe or semi-arid desert. All above evidence demonstrated that the fundamental changes of pollen assem- blage and their origins in Okinawa Trough since -200 ka BP were affected by combine factors including the coastline position and climate fluctuation. Moreover, the substantial shortening of distance between shoreline and the Okinawa Trough driven by orbital insolation cycles was clearly indicated by the pollen spectra, whereas the source-area climate signal of the pollen record was largely weakened.

Extreme fire weather is the major driver of severe bushfires in southeast Australia

In Australia,the proportion of forest area that burns in a typical fire season is less than for other vegetation types.However,the 2019-2020 austral spring-summer was an exception,with over four times the previous maximum area burnt in southeast Australian temperate forests.Temperate forest fires have extensive socio-economic,human health,greenhouse gas emissions,and biodiversity impacts due to high fire intensities.A robust model that identifies driving factors of forest fires and relates impact thresholds to fire activity at regional scales would help land managers and fire-fighting agencies prepare for potentially hazardous fire in Australia.Here,we developed a machine-learning diagnostic model to quantify nonlinear relationships between monthly burnt area and biophysical factors in southeast Australian forests for 2001-2020 on a 0.25°grid based on several biophysical parameters,notably fire weather and vegetation productivity.Our model explained over 80%of the variation in the burnt area.We identified that burnt area dynamics in southeast Australian forest were primarily controlled by extreme fire weather,which mainly linked to fluctuations in the Southern Annular Mode(SAM)and Indian Ocean Dipole(IOD),with a relatively smaller contribution from the central Pacific El Niño Southern Oscillation(ENSO).Our fire diagnostic model and the non-linear relationships between burnt area and environmental covariates can provide useful guidance to decision-makers who manage preparations for an upcoming fire season,and model developers working on improved early warning systems for forest fires.

四极杆电感耦合等离子体质谱仪测定动物牙化石中U和Th同位素

四极杆电感耦合等离子体质谱仪(Inductively Coupled Plasma-Quadrupole Mass Spectrometry,简称ICP-QMS)可用于U和Th同位素分析。目前,ICP-QMS能实现精度大约为0.3%(U)和1%(Th)的测量分析,可提供误差在1%～10%的^(230)Th/U年代数据。本文用ICP-QMS分析了采自意大利南都Loreto旧石器地点的4颗马牙化石样品,并对已发表的UTEVA树脂提纯U和Th的流程做了进一步改进,使其适用于动物牙化石样品。样品中的U和Th含量的平均测量精度(2σ)分别为0.3%和0.6%;^(234)U/^(238)U和^(230)Th/^(238)U活度比平均精度(2σ)分别为0.3%和0.8%。数据表明同一颗牙化石的不同组织的U含量可有数量级差别,同时它们的U-Th同位素活度比也可显著地离散(>2σ),从而导致不一致的^(230)Th/U年代结果。如今测定的各牙组织的U-Th同位素数据可用于模拟U的迁移历史;U-系分析与电子自旋共振测年技术相结合或可更好地估计样品的地质年代。