factors related to bh horizon depth for artificial and natural e bh sequences abstract aquods occur extensively in the coastal plain of the se usa where podzolization is mainly restricted to fluctuating water table conditions depths to upper boundaries of spodic bh horizons vary from a few cm to 75 cm even under similar drainage conditions hence seasonal water table depth parameters do not explain the wide variation in boundary depth one objective of this study was to experimentally test the following hypotheses h1 depth to the e bh boundary relates inversely to concentration of metal oxides silt and clay content of initial parent material for similar hydrologic conditions and organic acid activity h2 depth to that boundary is greater under higher organic activity for a given soil material and hydrologic condition another objective was to statistically evaluate how the composition of 270 natural spodic horizons collected during the florida cooperative soil survey program related to upper boundary depth thirteen sandy coastal plain soil materials of varying noncrystalline metal oxide al and fe silt and clay contents were packed in columns and subjected to daily cycles of fluctuating water tables and dilute organic acid applications artificial e bh boundaries of variable depths were generated in the columns boundaries tended to be abrupt but topographically irregular clay and extractable noncrystalline al and fe contents were inversely related to final depth of artificial bh horizons for the same water table conditions higher oxalic acid concentrations produced deeper boundaries in the same materials hence local biogeochemical factors related to organic acid production are also likely to influence the ultimate aquod morphology on the landscape silt clay and metal oxide contents were significantly higher in shallower than in deeper natural florida spodic horizons

vegetation variations and associated environmental changes during marine isotope stage 3 in the western part of the chinese loess plateau abstract this study further investigates the reported uniqueness of mis 3 climatic changes in northwestern china by focusing on the mis 3 lacustrine wetland sequences in the western part of the chinese loess plateau the lacustrine wetland sequence at the suancigou section documented four major environmental changes stratigraphic unit i was formed under lake dominated environments 48 420 35 730 14 c yr bp unit ii under wetland dominated environments 35 730 20 480 14 c yr bp and unit iii under eolian dominated environments 20 480 13 090 14 c yr bp unit iv is a fluvially reworked eolian loess unit 13 090 11 450 14 c yr bp pollen zone a 47 210 33 370 14 c yr bp representing a coniferous forest corresponds to stratigraphic unit i zone b 33 370 28 280 14 c yr bp representing a coniferous woodland landscape and zone c 28 280 22 480 14 c yr bp representing a landscape in which coniferous woodlands alternated with steppes correspond to unit ii zone d 22 480 11 450 14 c yr bp representing a steppe landscape corresponds to unit iii and unit iv we propose that the extremely wet mis 3 was a combined result of mildly high summer insolation and constantly higher than normal winter insolation that is mildly high mis 3 summer insolation was probably able to maintain the warmth of the ocean surface to the extent so that the tibetan plateau and northwestern china received an adequate supply of water vapour a constantly higher than normal mis 3 winter insolation might have shortened the duration of the winter monsoon so lengthening the rainy season in addition the soil vegetation air coupled feedback mechanisms under extensively well vegetated wet conditions might have further enhanced the mis 3 wet conditions

thermoluminescence dating of the orkutsay loess section in tashkent region uzbekistan central asia abstract the chronology of loess in central asia was investigated by means of thermoluminescence dating tl in the 1970s when age estimates ranging from 20 ka to over 800 ka were taken as providing an absolute chronology this has caused major misinterpretation of central asian loess stratigraphy and palaeoclimatic reconstruction we present a new tl study of a loess section at orkutsay in the tashkent region uzbekistan nine samples spreading over a large stratigraphic interval yield apparent tl ages ranging from 20 ka to 134 ka we interpret our tl results with reference to recent tl dating studies of loess from other regions we consider most of our tl age estimates obtained by the regeneration method to be underestimated a single tl date of 92 8 ka obtained by the total bleach method for loess just below the first pedocomplex pc 1 of the last interglacial is also significantly younger than expected we attribute the underestimation to sensitivity change induced by the laboratory optical bleach and instability of the tl signal we conclude that the current tl techniques as employed in this study cannot provide a reliable absolute chronology for the sequence below pc 1 and cannot provide even a relative chronology for the loess below pc2 for the orkutsay section the dating limit is around 130 ka the results of this study suggest that the previous central asian loess chronology based on early tl studies is not valid

reexamination of the near surface airflow over the antarctic continent and implications on atmospheric circulations at high southern latitudes abstract previous work has shown that winds in the lower atmosphere over the antarctic continent are among the most persistent on earth with directions coupled to the underlying ice topography in 1987 parish and bromwich used a diagnostic model to depict details of the antarctic near surface airflow a radially outward drainage pattern off the highest elevations of the ice sheets was displayed with wind speeds that generally increase from the high interior to the coast these winds are often referred to as katabatic with the implication that they are driven by radiational cooling of near surface air over the sloping ice terrain it has been shown that the antarctic orography constrains the low level wind regime through other forcing mechanisms as well dynamics of the lower atmosphere have been investigated increasingly by the use of numerical models since the observational network over the antarctic remains quite sparse real time numerical weather prediction for the u s antarctic program has been

east asian monsoon climates and gobi dynamics in marine isotope stages 4 and 3 abstract several thick last glacial loess sequences in the western part of the chinese loess plateau and an eolian colluvial sequence in the central mongolian plateau are used to understand how the summer and winter monsoons responded to global forcing factors during marine isotope stages mis 4 and 3 the magnetic susceptibility data are compared with other climatic proxy data to improve the well publicized reconstruction of the past monsoons this study suggests that different sensitivities between the summer and winter monsoons in responding to the northern insolation resulted in transitional climates between marine isotope stages which were characterised by cold and wet climates in the western part of chinese loess plateau after forest steppe in mis 5 coniferous forest emerged at the mis 5 mis 4 transition in cold and moist conditions these imply that the lower latitude oceans were still capable of supplying water vapour to the continental interior and that the mongolian high became dominant when the northern insolation entered a stadial state mis 4 coniferous forest dominated mis 4 but thereafter deteriorated to a steppe towards the end of the mis 4 probably because the lower latitude oceans failed to supply water vapour to the interiors a coniferous forest emerged again at the mis 3 mis 2 transition after forest steppe in mis 3 consequently the southern boundary of the gobi desert retreated northwards during the coniferous tree dominated periods between 73 and 60 ka and between 27 and 19 ka and expanded to maxima between 60 and 50 ka and between 19 and 10 ka the extent of the gobi desert was considerably smaller for several times around 47 ka and 41 ka and 27 ka during mis 3 than during the holocene and the northern boundary retreated 5 times around 20 ka 24 ka 29 ka 31 ka and 34 ka in just the later part of mis 3

blue ice areas in antarctica derived from noaa avhrr satellite data we have mapped antarctic blue ice areas using the u s national oceanic and atmospheric administration noaa advanced very high resolution radiometer avhrr antarctica cloud free image mosaic established by the united states geological survey the mosaic consists of 38 scenes acquired from 1980 to 1994 our results show that approximately 60 000 km2 of blue ice exist for each of the two main types of blue ice melt induced and wind induced normally the former type is located on slopes in coastal areas where climate conditions i e persistent winds and temperature together with favourable surface orientation sustain conditions for surface and near surface melt the latter blue ice category occurs near mountains or on outlet glaciers often at higher elevations where persistent winds erode snow away year round and combined with sublimation creates areas of net ablation furthermore we have identified an additional area of 121 000 km2 as having potential for blue ice however in these areas features such as mixed pixels glazed snow surfaces crevasses and or shadows make interpretation more uncertain in conclusion a conservative estimate of antarctic blue ice area coverage by this method is found to be 120 000 km2 0 8 of the antarctic continent with a potential maximum of 241 000 km2 1 6 of the antarctic continent

geochemistry of organic rich river waters in amazonia insights on weathering processes of intertropical cratonic terrain abstract in this study eight organic rich rivers that flow through the brazilian craton in the southwestern amazon rainforest are investigated this investigation is the first of its type in this area and focuses on the effects of lithology long term weathering thick soils forest cover and hydrological period on the dissolved load compositions in rivers draining cratonic terrain the major dissolved ion concentrations alkalinity talk sio 2 trace element concentrations and sr isotope contents in the water were determined between april 2009 and january 2010 in addition the isotopic values of oxygen and hydrogen were determined between 2011 and 2013 overall the river water is highly dilute and dominated by the major dissolved elements talk sio 2 and k and the major dissolved trace elements al fe ba mn p zn and sr which exhibit large temporal and spatial variability and are closely correlated with the silicatic bedrock and hydrology additionally rainwater and recycled water vapor and the size of the basin contribute to the geochemistry of the waters the total weathering flux estimated from our results is 2 4 t km 2 yr 1 which is one of the lowest fluxes in the world the co 2 consumption rate is approximately 21 61 10 3 mol km 2 yr 1 which is higher than expected given the stability of the felsic to basic igneous and metamorphic to siliciclastic basement rocks and the thick tropical soil cover thus weathering of the cratonic terrain under intertropical humid conditions is still an important consumer of co 2

the riverine silicon isotope composition of the amazon basin we present here the first large scale study of riverine silicon isotope signatures in the amazon basin the amazon and five of its main tributaries were studied at different seasons of the annual hydrological cycle the 30si signature of the dissolved silicon dsi exported to the estuary weighted for dsi flux for the period considered is estimated at 0 92 a river cross section shows the homogeneity of the amazon river regarding dsi concentration and isotope ratio the biogenic silica bsi concentration measured in surface water from all rivers is generally small compared to the dsi reservoir but large variations exist between rivers very low isotope signatures were measured in the upper rio negro 30si 0 05 0 06 which we explain both by an equilibrium between clay formation and dissolution and by gibbsite formation the si isotope fractionation in the andean tributaries and the amazon main stem can be explained by clay formation and follow either a rayleigh or a batch equilibrium fractionation model our results also suggest that the formation of 2 1 clays induces a fractionation factor similar to that of kaolinite formation

sources and transport pathways of marine aerosol species into west antarctica sixteen high resolution marine aerosol na so4 records from spatially distributed international trans antarctic scientific expedition itase ice cores spanning the last 200 years from the pine island thwaites and ross drainage systems and the south pole are used to examine sources sea spray and frost flowers and transport pathways of marine aerosols into west antarctica factors contributing to the amount of marine aerosols transported inland include sea ice extent the presence of open water features polynyas leads wind strength and direction and the strength and positioning of low pressure systems analysis of so4 na ratios indicates that frost flowers can contribute significantly 40 to the na budget of antarctic ice cores higher na concentrations in the ross drainage system may result from greater production of marine aerosols related to frost flowers in the ross sea region in association with greater sea ice extent and larger open water areas significant positive correlations of sea ice extent and the na time series exist in some regions of west antarctica higher wind speeds in winter and higher na concentrations when slp is

pedogenic factors affecting magnetic susceptibility of the last interglacial palaeosol s1 in the chinese loess plateau the magnetic susceptibility has been used as a quantitative or semi quantitative proxy for reconstructing the summer monsoon intensity in the chinese loess plateau based on extensive studies on climatic or and environmental mechanisms producing the magnetic susceptibility signatures however the precise nature of the link between past climates and the susceptibility signatures has remained uncertain primarily due to lack of our understanding in the nalizing and preserving processes of the signatures this paper attempts to examine the reliability or acceptability of this summer monsoon proxy from non magnetic perspectives of soil forming processes we chose nine sections along two transects one across the western part of the chinese loess plateau and another across the eastern part several conclusions can be drawn from our analytical data first clay translocation within the s1 palaeosol pro les as indicated by eld observed clay coatings on ped faces in bt and bk horizons and demonstrated by laboratory analysed clay contents must have moved some of the magnetic minerals downward so that the susceptibility re ects only the post translocation distribution of the magnetic susceptibility producing minerals second the best developed palaeosol s1s3 at most of the sections studied is not expressed by the magnetic susceptibility because this palaeosol developed in underlying coarse loess l2 and coarse textures tend to lower the susceptibility third carbonate concentration is normally negatively correlated with the magnetic susceptibility or simply suppresses the magnetic susceptibility peak when the susceptibility enhancement exceeds the carbonate dilution effect to conclude extreme caution must be observed when using magnetic susceptibility signatures to retrieve high resolution records of the last interglacial palaeoclimate in the chinese loess plateau copyright 2004 john wiley sons ltd

the second compare exercise a model intercomparison using a case of a typical mesoscale orographic flow the pyrex iop3 summary fifteen models have been evaluated for their ability to simulate the various phenomena of a mesoscale orographic flow sampled during the pyrcnqs experiment pyrex a pure forecast exercise has been conducted and model performances were assessed using numerous observations fio additional experiments were also performed in order to discriminate between small scale errors and large scale induced errors and to discuss an optimal specification of model terrain height and roughness for use with envelope orography and effective roughness length parametrizations the comparison results reveal systematic errors for all the models the local winds are too weak the mountain wave amplitude is too large and the lee vortices are poorly represented since forcing by analyses did not correct the errors they can be therefore mainly attributed to the model representation of orography the blocking created by the model topography at low level is under represented and the model topography does not sufficiently slow the flow a positive consequence of the effective roughness length parametrization is to reduce the mountain wave amplitude negligible benefit occurs from the use of an envelope orography parametrization although it favours the appearance of the lee vortices the latter appear too early the local winds remain too weak and the mountainwave amplitude is enhanced the comparison of the computed pressure drag with the observed one is reasonably good for most of the models but the pressure drag is found to be more correlated to the lee vorticity than to the mountain wave

influence of the orographic roughness of glacier valleys across the transantarctic mountains in an atmospheric regional model glacier valleys across the transantarctic mountains are not properly taken into account in climate models because of their coarse resolution nonetheless glacier valleys control katabatic winds in this region and the latter are thought to affect the climate of the ross sea sector frsater formation to snow mass balance the purpose of this paper is to investigate the role of the production of turbulent kinetic energy by the subgrid scale orography in the transantarctic mountains using a 20 km atmospheric regional model a classical orographic roughness length parametrization is modified to produce either smooth or rough valleys a one year simulation shows that katabatic winds in the transantarctic mountains are strongly improved using smooth valleys rather than rough valleys pressure and temperature fields are affected by the representation of the orographic roughness specifically in the transantarctic mountains and over the ross ice shelf a smooth representation of escarpment regions shows better agreement with automatic weather station observations than a rough representation this work stresses the need to improve the representation of subgrid scale orography to simulate realistic katabatic flows this paper also provides a way of improving surface winds in an atmospheric model without increasing its resolution

a numerical model to simulate snow cover stratigraphy for operational avalanche forecasting laws of snow metamorphism have been introduced in a numerical model which simulates the evolution of temperature density and liquid water profiles of snow cover as a function of weather conditions to establish these laws the authors have summarized previous studies on temperature gradient and on wet snow metamorphism and they have also conducted metamorphism experiments on dry or wet fresh snow samples an original formalism was developed to allow a description of snow with parameters evolving continuously throughout time the introduction of laws of metamorphism has improved significantly the derivation of the settlement of internal layers and of snow covered albedo which depend on the simulated stratigraphy i e the type and size of snow grains of different layers of the snow cover the model was tested during a whole winter season without any re initialization comparison between the simulated characteristics of the snow cover and the observations made in the field are described in detail the model proved itself to be very efficient in simulating accurately the evolution of the snow cover stratigraphy throughout the whole winter season

wind and temperature regime along the slope of adelie land antarctica an analysis was made of data collected from automatic weather stations aws on the slope of adelie land antarctica the data were collected simultaneously at different stations on the ice covered slope of the continent where no data have previously been obtained the stations are classified into three groups according to their location high plateau intermediate plateau or coastal region each having distinct annual temperature and wind speed regimes these classifications also correspond well to the stations slopes change in surface air temperature along the slope with respect to height was smaller than 1 c 100 m between the high plateau and the intermediate plateau stations the wind directions did not follow ball s model which suggests the importance of the gradient of surface potential air temperature along the slope on the wind regime a scale analysis showed the condition in which the gradient of surface potential air temperature along the slope should not be considered negligible when considering the total pressure gradient force this condition in turn indicates that the entrainment of momentum across the top of the katabatic wind layer is also important

the siberian loess record and its significance for reconstruction of pleistocene climate change in north central asia abstract the siberian loess represents the most significant terrestrial proxy record of quaternary climatic history in northern asia loess is extensive in southern siberia between the irtysh basin in the west and the angara basin in the east palaeoenvironmental multi proxy data magnetic susceptibility ms grain size caco 3 toc pollen etc from high resolution loess palaeosol sections provide evidence for a strongly fluctuating climatic sequence in north central asia during the late quaternary displaying the globally diagnostic sequences found in the deep sea oxygen isotope records ms provides the most continuous and detailed record encompassing the last two interglacial glacial cycles in loess sections in the minusinsk basin yenisei area and on the northern altai plains evidence for periodic atmospheric shifts is provided by gradual changes in the main vegetation zones with parkland steppe and mixed taiga during warm interglacial interstadial stages being replaced by boreal tundra forest and arid periglacial tundra steppe during stadials climatic pulses from warm intervals to cold are recorded by incipient forest steppe tundra gleysols the occurrence of the highest sediment accumulation rates in glacial stages ois 4 and ois 2 in the southern plains and depressions indicates that the most intensive aeolian dust deposition followed the glacial maxima with the most recent interval dated to ca 19 15 ka bp because of its zonal distribution and pronounced climatic continentality the siberian loess region represents an important data source for reconstructing past climates in the northern hemisphere it provides a key to the correlation of other loess regions within the west east eurasian continental zone

the effect of blowing snow on katabatic winds in antarctica an acceleration of the katabatic winds during periods of blowing snow was observed in adelie land antarctica data collected by automatic weather stations a ws showed a change in the relationship between the katabatic term of the surface geostrophic wind katabatic force and the wind speed for periods of blowing snow when measurements of the katabatic force were plotted against cube of the wind speed the slope was steeper for wind speeds at less than a threshold speed for blowing snow the difference between these two slopes was partly explained by the effect of blowing snow entrained into the atmospheric boundary layer

podzols in amazonia summary in the area near manaus amazonia brazil soil sequences including oxisols ultisols and spodosols podzols are widely distributed such toposequences occur on slopes leading down into valleys cut in a nearly level plateau the geochemistry of the organic and mineral components of one of these sequences has been investigated spodosols develop on quartzose sands which may be the results of an intense hydrolysis of clays and or an impoverishment of clays through eluviation or selective erosion large analogies with podzolization in the temperate zone were found especially in the organic matter dynamics as the clay content decreases more organic compounds with increased aromaticity and more polycondensed structures were allowed to move forming the bh horizons or reaching the water streams an in situ experimentation was also performed to characterize presently active soil forming processes it was found that podzolization in amazonia was mainly active during the rainy season

alleviation of stationary biases in a gcm through a mountain drag parameterization scheme and a simple representation of mountain lift forces abstract the problem of the representation of the orientation of mountain forces in a gcm is examined first a series of winter simulations is presented with the laboratoire de meteorologie dynamique gcm where the model ground is flat and where the mountains are represented by applying forces to the flow that are either strictly opposite to the local wind i e a drag or strictly perpendicular to it i e a lift these experiments show that the drag forces improve the zonal wind but do not improve the steady planetary wave everywhere while the lift forces scarcely affect the zonal wind but force a steady planetary wave that is everywhere realistic the drag force is formulated following the realistic subgrid scale orographic sso scheme developed recently at ecmwf the lift force essentially enhances vortex stretching over large scale mountains to address issues concerning the representation of sso in gcms experiments with mean orography the ecmwf sso scheme and enhanced lift forces over mounta

tropical spodosols in northeastern amazonas state brazil abstract the white sand formation found in northeastern amazonas state in brazil showed three horizons e b and c the superficial horizon e was formed by sandy friable material of grayish to whitish colour with accumulations of organic matter in the form of wavy bands the b horizon remained essentially sandy but showed a pale yellowish to orangish colour the c horizon was friable with pink to creamy clayey sandy materials in the contact zone between horizons b and c occurred an enrichment of organic matter forming ortsteins the profile structure the upward increasing of quartz grains corrosion and the predominance of quartz in the e horizon and thus of io 2 instead of kaolinite al 2 o 3 fe 2 o 3 and tio 2 that were more abundant in the c horizon suggest that the white sands are the product of podzolization soil horizonation and accumulation of organic matter are governed by the active decomposition of the forest litter these data also allow us to relate the spodosols with the mottled and the saprolitic horizons of truncated lateritic profiles of the alter do chao formation this process of podzolization which continues up to the present moment is very aggressive since the studied profiles have developed in less than 3000 years and beneath the modern forest

magnetic granulometric and geochemical characterizations of loess sections in the eastern arid central asia implication for paleoenvironmental interpretations abstract loess deposits in the arid central asia aca contain sensitive messages concerning the evolution of the westerlies and the interior aridification of asia in this study we conducted a combined study of geophysical and geochemical characterization on loess sections in the eastern aca to discuss possible paleoclimate development since the late pleistocene era results show that the aca loess chiefly exhibited similar geophysical and geochemical compositions with loess deposits in other regions like the chinese loess plateau there are various accumulation rates that would have been responsible for the depositional difference within the aca loess profiles in addition there are three magnetic responses to the bulk grains and geochemical proxies in this study at the bottom segment of the section magnetic enhancement was associated with coarse grain sizes and water leaching magnetic enhancement responded to stronger pedogenesis and moderate paleo wind intensity in the uppermost parts moreover there is a transitional segment in the middle part of the section characterized by inordinately detrital inputs and weak pedogenic contributions thus it may be better to evaluate the magnetic climatology of the aca loess through different depositional stages furthermore this study generally reveals that the paleoclimate pattern in the aca was probably characterized by relatively low moisture during warm intervals and vice versa in the middle and bottom parts of the profiles but relatively enhanced moisture was indicated during the holocene period further studies are still necessary to obtain reliable proxies and chronology for a detailed paleoclimate interpretation of the aca loess

fine grained quartz osl dating chronology of loess sequence from southern tajikistan implications for climate change in arid central asia during mis 2 abstract the desert and semi desert region of arid central asia is one of the most important areas of middle latitude dust emission and deposition in the northern hemisphere marine isotope stage 2 mis 2 was the latest and one of the most representative intervals of dust emission from the region and it is especially important for research into processes of dust transportation and deposition here we report the results of an optically stimulated luminescence study of the hoalin section in southern tajikistan which was deposited during mis 2 the fine grained quartz single aliquot regeneration sar approach was used and its reliability was verified by internal checks in addition grain size analyses calculated dust accumulation rates dars and mass accumulation rates mars were used to reconstruct the pattern of climate change during mis 2 the mean dar for southern tajikistan during mis 2 was 0 43 m ka and the corresponding average mar was 673 g cm2 a for a non river terrace site which is higher than the average mars estimated for the central and southern chinese loess plateau clp in contrast to previous suggestions the high dust dars and mars during the lgm indicate a cold dry climatic pattern rather than a cold humid pattern our results also confirm that the patterns of high dust emission and deposition during the lgm in the mid latitude arid zone of asia were synchronous

micromorphology and chemical weathering of a k rich trachyandesite and an associated sedimentary cover parkes se australia abstract the micromorphology composition and sequential formation of weathering products of a k rich trachyandesite and an associated sedimentary cover at parkes se australia are described this has been achieved using a combination of mineralogical optical x ray microdiffraction and sem edxa microanalysis and chemical x ray fluorescence techniques the weathering profiles have developed in a low altitude relatively flat landscape setting the following processes are dominant a weathering of primary minerals notably feldspars and micas to transient poorly crystalline oxyhydroxide patches smectite and ultimately kaolinite b weathering of sediments in a zone of intense solution activity and redox reactions resulting in development of mottles and ferruginous nodules and c greater thickness up to 350 cm and compositional differences between the soil over weathered sediments and in situ weathered bedrock the dominant profile microsystems evolved under a past humid climate later modified by the prevailing semi arid to arid conditions

abrupt climatic events recorded by the ili loess during the last glaciation in central asia evidence from grain size and minerals abstract the loess record of central asia provides an important archive of regional climate and environmental changes in contrast to the widely investigated loess deposits in the chinese loess plateau central asian loess paleosol sequences remain poorly understood here we present an aeolian loess section in the southern ili basin based on granularity and mineralogical analyses we reconstruct climatic changes during the last glaciation the results indicated that most of the abrupt climatic events such as dansgaard oeschger events and heinrich events were imprinted in this loess section although their amplitudes and ages showed some differences compared with the millennial oscillations recoded in loess and stalagmites in east asia the arid central asia responded more sensitively to the warming events than to the cooling events the shifting trajectory of westerlies across central asia played an important role in dust deposition during the stadials the north atlantic climatic signals may have been transmitted from central asia to the east asian monsoon regions via the westerlies

contrasting iron isotopic compositions in river suspended particulate matter the negro and the amazon annual river cycles abstract iron isotopic compositions fe irmm 14 56 of suspended particulate matter spm from two major rivers in the amazon basin the amazon river itself at the obidos station and the negro river at the serrinha station were investigated in the present study the main objective was to search for temporal variations during their annual river cycles fe irmm 14 56 values for the amazon river at obidos range between 0 00 and 0 15 indistinguishable from the average continental crust value in contrast the iron isotopic compositions of the negro river serrinha station spm vary between 0 34 and 0 82 whereas the dissolved matter is isotopically heavier in this river the lack of significant isotopic variations in the amazon river indicates that one individual spm subsurface sample is representative of the river during the whole annual river cycle in opposition to results obtained for the negro river the data suggest that in organic poor white water rivers such as the amazon iron isotopic signatures of the suspended fraction reflect a detrital crustal component with little isotopic fractionation on the other hand in the organic rich negro river which has tropical podzols as the main iron source the iron redox cycling at the water soil interface influences the iron isotopic composition

penetration of atlantic westerly winds into central and east asia abstract the geographical position of the convergence zone where the western atlantic climate system meets the asian winter monsoonal system depends on their relative strength these individual strengths are determined by the intensities of the air pressure gradients over the north atlantic and the siberian high pressure cell respectively since the factors that forced those gradients varied throughout glacial interglacial cycles the location of the convergence zone should have moved accordingly both the grain size characteristics of wind blown sediments and climate modelling prove that the atlantic influence extended remarkably far eastward at times the northeastern tibetan plateau was at the cross road of western and monsoonal influences during the last glacial this region was dominated by an atlantic signal with millennial scale climatic oscillations that are similar to the north atlantic marine and greenland ice core records in contrast that same region was only under monsoonal influence during the last interglacial it implies that the atlantic winds penetrated more vigorously eastward in full glacial conditions than in interglacial conditions

the effect of small scale hills on orographic drag the purpose of this study is to investigate the extent to which the presence of hills with relatively short horizontal scales can influence the drag due to mountain waves and flow blocking exerted on the flow by larger scale mountains numerical simulations of stratified flow over mountains are presented for flow over orography described by the linear superposition of broad mountains whose length scales are large enough to generate mountain waves and narrow corrugations whose wavelengths fall below the minimum horizontal wavelength for stationary gravity waves results are presented for both two and three dimensional mountain shapes and for a range of corrugation heights it is shown that the corrugations can significantly reduce the amplitude of the mountain waves generated by the broader mountain or they can suppress the unsteadiness of the wake when these mechanisms make an important contribution to the total drag this implies a significant drop in the total drag compared to the sum of the contributions from the two scales of orography from the point of view of drag parametrization the extent to which the effect of the small scale hills can be represented via an effective roughness length is investigated crown copyright 2007 reproduced with the permission of her majesty s stationery office published by john wiley sons ltd

polynya dynamics a review of observations and modeling 1 polynyas are nonlinear shaped openings within the ice cover ranging in size from 10 to 105 km2 polynyas play an important climatic role first winter polynyas tend to warm the atmosphere thus affecting atmospheric mesoscale motions second ocean surface cooling and brine rejection during sea ice growth in polynyas lead to vertical mixing and convection contributing to the transformation of intermediate and deep waters in the global ocean and the maintenance of the oceanic overturning circulation since 1990 there has been an upsurge in polynya observations and theoretical models for polynya formation and their impact on the biogeochemistry of the polar seas this article reviews polynya research carried out in the last 2 decades focusing on presenting a state of the art picture of the physical interactions between polynyas and the atmosphere sea ice ocean system observational and modeling studies the surface heat budget and water mass transformation within these features are addressed

synoptic activity in the seas around antarctica abstract the recent ncep department of energy doe reanalysis 2 update of the original ncep ncar dataset provides what is arguably the highest quality analyses spanning two decades available for the high southern latitudes it therefore offers an excellent starting point from which to assemble a modern comprehensive and reliable picture of synoptic activity in the subantarctic region this set covering the modern satellite era from january 1979 to february 2000 is used herein in addition the exploration in this study has been conducted with sophisticated feature tracking and trajectory analysis software it is shown that the high southern latitude cyclone system density is greatest in the indian ocean and to the south of australia near or to the south of 60 s the numbers in winter exceed those in summer except over a few but important regions such as the bellingshausen sea the antarctic coastal region is confirmed as one of high cyclonicity as is that in the northern part of the antarctic

cyclonically forced barrier winds along the transantarctic mountains near ross island abstract the effect of the transantarctic mountains on cyclonically forced boundary layer winds in the vicinity of ross island antarctica 77 5 s 167 e is discussed when cyclones are present over the western ross ice shelf and ross sea the low level easterly airflow is toward the mountains a barrier wind regime is set up as the flow is turned northward and becomes parallel to the mountain range it is found that cyclonically forced barrier winds occurred around 5 and 8 of the time during 1984 and 1985 respectively the case histories of two well defined barrier wind events lasting for 24 h are discussed in detail with regional analyses based on satellite photographs and automatic weather station data one case is for a katabatic wind forced mesoscale cyclone forming to the north of ross island and the other is for a synoptic scale cyclone moving through the western ross ice shelf ross sea region a numerical model for the vertically integrated boundary layer flow that calculates two horizontal

from oxisols to spodosols and histosols evolution of the soil mantles in the rio negro basin amazonia abstract the upper rio negro basin under a constantly humid equatorial climate is a low altitude peneplain of more than 165 000 km 2 prevailing soils are oxisols and spodosols and their distribution is usually related to the lithology of the parent materials spodosols being generally associated with sandy deposits after exploratory surveys in this extensive region six major soil geomorphic units have been identified in which selected toposequences have been studied by means of micromorphological chemical and mineralogical analyses detailed field analysis of the horizonation of the soil mantle has been carried out in three sequences consisting of oxisols ultisols and spodosols results show that sharp transitions within distances of less than one hundred meters separate the oxisols from the spodosols however the arrangement of the horizons in the soil mantle and similarities in micromorphological features chemical composition and mineral components between the adjacent horizons are evidences that genetic relationships link contiguous profiles the authors propose an alternative explanation for this soil distribution based on the lateral transformation of oxisols and ultisols into spodosols and on the lateral evolution of the giant spodosols into histosols peat and waterlogged ultisols interpretative models of landscape evolution as consequence of soil evolution are thus proposed

late quaternary sediment fluxes from tropical watersheds abstract inherited saprolite stores and continued weathering in quaternary time juxtapose abundant clay and fresh rock in tropical landscapes this influences sediment fluxes and affects the interpretation of sediment sequences derived from tropical watersheds detrital kaolinites derive from inherited saprolite sources as well as from soil clays and appear in delta and ocean sediments these sediments appear to correspond with sub milankovitch millennial scale cycles of climate change but may also record century scale episodes of rapid warming dansgaard oeschger events destabilisation of sediment sources and increased sediment fluxes in the late quaternary followed millennia of climatic deterioration cooling aridity and vegetation change and led to altered patterns of sedimentation during the last glacial maximum lgm sediment yield from slopes increased 10 around the lgm when rainfall was reduced by 30 60 and led to fan building and braided channels rainfall increased 40 80 from the lgm to the early holocene maximum and this led to channel cutting and major sediment fluxes to delta and ocean sinks vegetation recovery lagged the rapid warming by several millennia and was interrupted by younger dryas yd aridity influencing slope and stream behaviour holocene sedimentation has been by both vertical and lateral accretion increasing floodplain sediment stores

stratigraphies and chronologies of late quaternary loess paleosol sequences in the core area of the central asian arid zone abstract the sporadic distribution of the quaternary loess in central asia makes it hard to establish a regional pedostratigraphy through visual tracing of marker strata the pedostratigraphic correlation presented here is thus completely based on the radiocarbon chronologies of the four studied sections the first noticeable feature is that poorly drained conditions predominated in the period between 48 000 and 30 000 14 c bp during which three entisols developed at 45 000 14 c bp 40 000 14 c bp and 35 000 14 c bp after a period of loess deposition between 30 000 and 18 000 14 c bp under poorly drained conditions an entisol at the westernmost site valikhanov south central kazakhstan developed between 18 000 and 10 000 14 c bp also under poorly drained conditions the time equivalent deposits at romantic and zeketai sections to the east do not exhibit any soil forming characteristics although poorly drained conditions are also imprinted in the time equivalent loess the holocene sequences in the central asian domain consist of an early holocene loess unit deposited between 10 000 and 5 000 14 c bp and a late holocene soil formed during the past 5000 years in comparison the climate was also wet between 48 000 and 20 000 14 c bp during which three mollisols developed under well drained conditions in the chinese loess plateau of the east asian domain the loess deposited between 23 000 and 10 000 14 c bp in the chinese loess plateau has neither observable marks of soil formation nor imprints of poorly drained conditions the holocene sequence in the east asian domain exhibits an out of phase relationship with that in the central asian domain consisting of an early holocene soil formed between 9000 and 4000 14 c bp and a late holocene loess unit deposited during the past 4000 years

organic complexation and translocation of ferric iron in podzols of the negro river watershed separation of secondary fe species from al species abstract the development of podzols in lateritic landscapes of the upper amazon basin contributes to the exportation of organic carbon and associated metals in the black waters of the negro river watershed we have investigated the distribution of feiii in the clay size fraction of eight organic rich horizons of waterlogged plateau podzols to unravel the weathering conditions and mechanisms that control its transfer to the rivers the speciation and amount of feiii stored in residual mineral phases of laterites or bound to organic compounds of weakly and well expressed podzols were determined by electron paramagnetic resonance spectroscopy combined with chemical analyses reducing conditions restrict the production of organo fe complexes in the subsoil b horizons of waterlogged podzols and most of the fe2 released from the dissolution of fe oxides is exported to the rivers via the perched groundwater however significant amounts of diluted feiii bound to organic ligands feiiiom and nano fe oxides are produced at the margin of the depression in the topsoil a horizons of weakly expressed podzols due to shorter periods of anoxia the downward translocation of organically bound metals from topsoil a to subsoil b horizons of podzols occurs in shorter distances for fe than it does for al this separation of secondary fe species from al species is attributed to the physical fractionation of their organic carriers in texture contrasted b horizons of podzols as well as to the effect of ph on metal speciation in soil solutions and metal binding onto soil organic ligands mostly for al this leads us to consider the topsoil a horizons of weakly expressed podzols as well as the subsoil bh horizon of better expressed ones as the main sources for the transfer of feiiiom to the rivers the concentration of feiiiom rises from soil sources to river colloids suggesting drastic biogeochemical changes in more oxygenated black waters of the negro river watershed the contribution of soil organic matter to the transfer of fe to rivers is likely at the origin of the peculiar fe isotope pattern recently recognized in podzolic environments

diversity and peculiarities of soil formation in eolian landscapes insights from the mineral magnetic records abstract magnetic properties of loess paleosol sequences are widely utilized as sensitive easily obtained and reliable proxy archives of past climate change in continental settings however soil formation in aeolian landscapes may occur under different and changing conditions of dust sedimentation which will affect the growth and development of the pedogenic magnetic component this phenomenon is explored in our study by analyzing depth variations of the following magnetic characteristics frequency dependent magnetic susceptibility anhysteretic magnetic susceptibility and the ratio between anhysteretic susceptibility and isothermal remanent magnetization acquired in a 100 mt back field arm irm 100 mt along three loess paleosol profiles from ne bulgaria a conceptual model for the time evolution of the grain size of the pedogenic magnetic fraction with soil depth is proposed which is build upon the mechanism of soil formation accretional or in stable land surfaces or a combination of the two another magnetic ratio isothermal remanence acquired in a 300 mt back field divided by low field magnetic susceptibility irm 300 mt is utilized as a proxy for the changes in the ratio of silt to clay fractions indicative of changes in dust sedimentation regimes during glacial interglacial transitions according to the proposed conceptual model verified by the magnetic signature of three holocene soils from ne bulgaria discrimination between accretional soils and soils developed without dust additions during soil forming period can be done accretional soils are characterized by parallel changes in grain size sensitive magnetic proxies soils developed at stable landscape conditions show gradation of the depths at which maximum enhancement of various proxies occurs with deepest occurrence of the maximum in fd followed by depth of maximum arm and arm irm 100 mt another implication of the new conceptual model is that the mean coercivity of the pedogenic component of accretional soils will be higher than that of soils developed without eolian input at equal temperature conditions because of the soils thermal gradient and different depths at which pedogenic minerals form in the two settings the results revealed that the holocene soils so has developed under different soil forming conditions than paleosols from the same sites

pedogenesis on the uplands of the diamantina plateau minas gerais brazil a chemical and micropedological study abstract little is known about the soil distribution on quartzitic uplands of brazil the diamantina plateau where deeply weathered oxisols latosols and shallow sandy soils occur side by side represents part of the higher and oldest planation on the quartzitic uplands of minas gerais state we studied representative soils from the diamantina plateau to help understand the pedogenesis and landscape evolution of this part of minas gerais we found evidence of a lithological and tectonic control on the distribution of soils in the landscape polygenetic oxisols acrustox occur at the top of the landscape at altitudes of 1300 m or more resting uncomformably on quartzitic saprocks xanthic types or mafic rocks rhodic types they change downslope to in situ quartzpsamments and haplorthods in the b horizon of the xanthic acrustox quartz grains smaller than 0 3 mm are surrounded by gibbsitic plasma forming subspherical microaggregates microaggregates in the bw horizon of all upland oxisols display inherited features of intense biological activity regardless of the parent material or texture the nutrient poor catena of xanthic acrustox ustic quartzpsamments oxyaquic haplorthods represents a sequence of increasing hydromorphic conditions downwards in which clay minerals are destroyed in low ph and ferrolysis in the poorly drained soils downslope low ph and eh induce the movement of reduced fe 2 and organic matter om bound al and fe both per descendum and through lateral flow downslope in the bottom micromorphological features and the chemistry of organic matter indicated that some bsh horizons represent buried a horizons subjected to post burial podzolization corroborating morphological field data this indicates the pertinence of the study of humic fractions in defining the bhs spodic horizons of brazilian spodosols

correlation of loess paleosol sequences in east and central asia with se central europe towards a continental quaternary pedostratigraphy and paleoclimatic history abstract as recent small climatic fluctuations on a 102 103 year time scale can be correlated worldwide and represent a decline of mean annual temperature of only 1 c major climatic changes on at least a 105 year scale glacial interglacial cycles and probably a 104 year scale the approximate length of an interglacial must be of similar ages throughout the temperate climatic belt of the northern hemisphere this concept allows continental pedostratigraphical correlations detailed knowledge of the genesis of paleosols is needed to establish loess paleosol stratigraphies that can be used for paleoclimatic reconstruction most paleosols however are truncated and largely recalcified from overlying loess micromorphological studies allow primary and secondary carbonates to be distinguished and provide unequivocal evidence of clay illuviation this enables the recognition of typical loess weathered loess and the recognition of different genetic soil horizons such as cb bc ah bw and bt horizons for the brunhes epoch the sequence at karamaydan tadjikistan is more detailed than the corresponding section in luochuan china and even more than in se central europe except for the last glaciation the very good correlation with the deep sea oxygen isotope record which includes the development of an accurate astronomical time scale allows a detailed chronostratigraphical subdivision of the loess paleosol sequence in karamaydan which therefore should be regarded as a key sequence for reconstructing the climatic history of the brunhes epoch this implies that the loess paleosol sequences in se central europe are less complete than thought earlier pedocomplexes in karamaydan correspond with single paleosols in se central europe e g the f6 paleosol in stari slankamen correlates with pedocomplexes pk vi and v at karamaydan which were formed over a period of about 140 ka although pedogenesis was interrupted several times by loess deposition the f6 soil is therefore an example of a welded paleosol as are the f5 the f4 and the f2 paleosols in se central europe for most of the matuyama epoch the central and lower parts of the sequence at chashmanigar show more pronounced paleosols than the equivalent parts at luochuan in se central europe only at stari slankamen are three strongly developed though truncated paleosols f9 f11 above neogene sediments mineralogical investigations of the silt and clay subfractions show that there is little difference in the type and amount of pedogenic clay mineral formation between the holocene soils and the paleosols of the brunhes epoch at karamaydan and of the matuyama epoch at chashmanigar this suggests that the interglacial climates represented by the b or bt horizons of the buried paleosols of late middle and early pleistocene age were similar to that of the holocene

development of a three dimensional meso γ primitive equation model katabatic winds simulation in the area of terra nova bay antarctica the spatial evolution of antarctic katabatic winds in the area of terra nova bay is examined using the three dimensional version of the universite catholique de louvain modele atmospherique regional ucl mar mesoscale primitive equation models the ability of the model to replicate classical linear mountain wave simulations is verified then three dimensional experiments are performed for the terrain configuration of terra nova ross sea coastal zone using different horizontal resolutions 5 10 and 20 km the model converges for resolutions lower than 10 km results are in qualitative agreement with available observations and previous modeling work strong katabatic winds are simulated with a jet over terra nova bay the model seems able to initiate the mesocyclonic activity in the ross sea due to the katabatic circulation

a numerical study of the western cosmonaut polynya in a coupled ocean sea ice model 1 employing results from a 0 4 40 level fully global coupled ocean sea ice model we investigated the role of physical processes emanating from atmosphere ocean and ice in the initiation maintenance and termination of a sensible heat polynya with a focus on the western cosmonaut polynya that occurred during may july 1999 the cosmonaut polynya first appeared in early may 1999 in the form of an ice free embayment transformed into an enclosed polynya on 5 9 july and disappeared by late july when the ice from the surrounding regions began to encircle the embayment except for the differences in ice concentrations the time of appearance size and shape of the cosmonaut polynya simulated by the model are in approximate agreement with the special sensor microwave imager ssm i observations between may and july 1999 the cosmonaut sea experienced two synoptic storms both lasting 5 days followed by the passage of the first storm on 12 19 june there was a remarkable growth in the size of the embayment by 21 103 km2 associated with this the sea surface temperature sst rose by 0 15 c the upward heat flux jumped from 5 to 94 w m 2 and a net freshwater flux into the ocean increased by 2 cm d 1 by running the model simulation with a 20 wind speed increase it is demonstrated that the twofold increase in sst and upward heat flux increased the embayment area by 15 103 km2 and decreased the ice concentration by approximately 10 from the control run a similar but somewhat weaker wind event that took place on 30 june to 10 july had less influence on the embayment area although the upward heat flux 65 w m 2 was comparable to the first event by examining the vertical displacement of the 1 6 c isotherm depth prior to during and after these two storms we demonstrate that the impetus provided by these storms was able to raise the 1 6 c isotherm depth by 30 m through wind driven mixing making sufficient oceanic heat input from beneath the mixed layer available to prevent freezing and or delay ice formation while ice in the adjacent regions continued to grow a sudden shift in the ice drift direction from southwest to northeast 3 july followed by the second storm accompanied by large air sea temperature differences caused the enclosure of the embayment subsequent formation of the polynya and its termination

simulation of the mesocyclonic activity in the ross sea antarctica the mesocyclonic activity in the southwestern ross sea is examined with emphasis on its forcing by katabatic winds the three dimensional version of the meso gamma scale primitive equation model modele atmospherique regional is used in which a representation of cloud microphysical processes has been introduced idealized boundary conditions are prescribed in particular the ocean is assumed to be completely ice free or partially ice covered the former case corresponds to a fall situation that coincides with the climatological maximum of estimated precipitation at mcmurdo station on ross island due to the propagation of katabatic winds over the ocean boundary layer fronts form clouds are generated in the fronts a surface pressure trough also forms and extends northeastward from terra nova bay mesocyclones are simulated in the trough when the ocean is ice free strong sensible heat fluxes toward the atmosphere amplify the strength of the trough up to typically observed values tn this case snow precipitation is associated with the boundary layer fronts and occurs in particular over mcmurdo sound it is also found that latent heat release due to precipitation formation in the fronts does not significantly affect the deepening of the trough

loess stratigraphy of central asia palaeoclimatic and palaeoenvironmental aspects abstract the loess palaeosol succession of central asia is comparable with that of the loess plateau in north china palaeomagnetic investigations and palaeontological studies in south tadjikistan suggest a date of 2 2 5 ma for the oldest loess indicating that dust storms became frequent in the region since 2 2 5 ma bp under the prevalently arid and semi arid environments of central asia aeolian processes had a gradually increasing influence on subaerial sedimentation during the pleistocene however atmospheric aeolian processes in central asia have mainly developed in accordance with pleistocene climatic cyclicity without extremely high intensification during the late pleistocene as implied by the previous tl dating results the identification of loess and palaeosol horizons with respective glaciations and interglacials is sometimes disputable nevertheless the available data in spite of limited evidence characterise well developed palaeosols of the middle and late pleistocene as warm and wet intervals associated with interglacials palynological studies of loess sections show that loess and palaeosol horizons have palynological spectra that are sometimes difficult to interpret interregional loess palaeosol correlation with glacial interglacial events as well as with oxygen isotope records should be supplied by multidisciplinary investigations

holocene vegetation variations and the associated environmental changes in the western part of the chinese loess plateau abstract the western part of the chinese loess plateau has experienced a series of environmental changes during the holocene a desert steppe of late glacial was succeeded by a forest steppe from 8850 to 7540 14 c years bp and a pinus dominated forest occupied the landscape from 7540 to 6560 14 c years bp a deciduous forest of high density and diversity existed from 6560 to 5790 14 c years bp afterwards the vegetation changed to a pinus dominated forest steppe 5790 4950 14 c years bp and then to an ulmus dominated forest steppe 4950 to 4000 14 c years bp the vegetation subsequently changed to a steppe from 4000 to 3120 14 c years bp and further to a desert steppe from 3120 to 2900 14 c years bp after a period of vegetation improvement steppe from 2900 to 2460 14 c years bp a desert steppe resumed 2460 2020 14 c years bp steppe vegetation was re established around 2020 14 c years bp and seems to have then deteriorated again around 1000 14 c years bp the general trend of aforementioned climatic changes is proposed here to have been modulated by the insolation changes specifically the insolation started to increase around 15 000 years bp and peaked around 9000 years bp when the obliquity driven seasonality reached a maximum with the summer insolation being about 8 more than the present as a result tropical holocene sst increased steadily from 10 000 to 6 000 years bp thus effectively strengthening the east asian summer monsoon in addition the documented high temperatures from 10 000 to 4000 years bp in high northern latitudes might have weakened the strength of the winter monsoon and thus enhanced the strength of the summer monsoon probably via lengthening of the rainy season directly contributing to the megahumid climate between 10 000 and 4000 years bp in the western part of the chinese loess plateau

identification of antarctic ablation areas using a regional atmospheric climate model the occurrence of antarctic ablation areas in dronning maud land the lambert glacier basin victoria land the transantarctic mountains and the antarctic peninsula is realistically predicted by the regional atmospheric climate model racmo2 ant with snowdrift related processes calculated offline antarctic ablation areas are characterized by a low solid precipitation flux in combination with strong sublimation snowdrift erosion and or melt the strong interaction between atmospheric circulation and topography plays a decisive role in the precipitation distribution and hence that of ablation areas three types of antarctic ablation areas can be distinguished all occurring in dry regions type 1 is the erosion driven ablation area caused by 1 d and or 2 d divergence in the katabatic wind field at high elevations 2000 3200 m asl type 2 is the sublimation driven ablation area this type occurs at lower elevations

eolian environmental changes in the northern mongolian plateau during the past 35 000 yr abstract this study focuses on an eolian section shaamar section in the northern mongolian plateau and compares the eolian sequences in the northern mongolian plateau with those along the southern boundary of the gobi deserts to better understand the dynamics of the gobi deserts during the past 35 000 14c yr bp only a weak entisol like paleosol was formed around 29 000 14c yr bp in the exposed mis 3 portion at the shaamar section whereas an eolian colluvium paleosol sequence at nearby bureghkanga section exhibits three paleosols formed around 29 000 14c yr bp 31 000 14c yr bp 34 000 14c yr bp loess paleosol sequences in the western siberian lowland exhibit four paleosols formed from 40 000 to 25 000 14c yr bp i e mis 3 during mis 2 two mollisol like paleosols were formed from 25 000 to 21 000 14c yr bp and from 16 000 to 13 000 14c yr bp and one entisol like paleosol was formed around 9500 14c yr bp at the shaamar section the mis 2 was characterized primarily by silt deposition except for the interval between 21 000 and 16 000 14c yr bp that was dominated by sand deposition the holocene began with the mollisol like paleosol formation from 8600 to 7000 14c yr bp the mid holocene 7000 to 3000 14c yr bp was marked by a relatively poor vegetation cover and the late holocene since 3000 14c yr bp by the densest vegetation cover of the entire holocene in summary the maximal extent of hyperarid and arid areas gobi deserts and gobi like occurred twice 1 from 21 000 to 16 000 14c yr bp and from 13 000 to 8600 14c yr bp when the dominant eolian deposition conditions extended from 56 n to 33 n or even larger the extent of hyperarid and arid areas retreated to the area between 38 n and 48 n or even much smaller several times during mis 3 and during the early holocene considering the uncertainties of dates it seems that the holocene bioclimatic conditions might have changed more or less synchronously between the north and the south and that the bioclimatic conditions varied more frequently in the north than in the south during mis 3 two mollisol like paleosols iic 13 000 to 16 000 14c yr bp and iiia 21 000 to 25 000 14c yr bp were well developed during mis 2 in the north but no corresponding major paleosols were discovered in the south suggesting that the climate did not change synchronously during mis 2 the climates during the stadial interstadial mis 3 2 transition 25 000 to 21 000 14c yr bp and during the last glacial maximum deglacial transition 16 000 to 13 000 14c yr bp were much more humid in the north than in the south

deterministic chaos and historical geomorphology a review and look forward the study of nonlinear dynamics in geomorphology has been dominated by analytical techniques derived largely from other fields ultimately however confronting nonlinear complexity requires problematizing from within a geomorphological context this paper focuses on deterministic chaos the major classes of techniques for detecting chaos in geomorphic systems are reviewed while the long time series most amenable to traditional methods of chaos detection are only occasionally available to geomorphologists there are methods for detecting chaos in spatial data including qualitative and categorical data many of these are similar to or are adaptations of familiar techniques for partitioning within and between unit variation and for identifying elementary uniform landscape units the manifestations of chaos in landforms and landscapes take the form of divergent vs convergent evolution increasing vs decreasing irregularity disproportionality vs proportionality of response to perturbations or initial variations and the lack of geographical consistency or commonality of response these also serve as criteria for distinguishing between achievement of a new steady state and unstable divergence in interpreting geomorphic changes study of nonlinear dynamics in earth science need not be dominated by theoreticians and modellers as complex nonlinear behaviors can be identified and diagnosed using the types of data observations and methods typically available to geomorphologists even more important is the need to further inform the study of nonlinear dynamics on the basis of field based geomorphology

kaolinite dating from acrisol and ferralsol a new key to understanding the landscape evolution in nw amazonia brazil abstract ferralsols and acrisols are major types of soils of the amazon basin observed on various landform units comprising plateau surfaces incised hills at their edges and slopes the present study focuses on an acrisol developed on plateaus surfaces from northwest amazonia and a ferralsol from the convex hills of the incised plateau edges local geomorphologic models of weathering covers suggest that ferralsols are younger than plateau acrisols but the absolute chronology of their formation is still lacking this type of information is however critical to understand the evolution of northwest amazon basin landscapes and to identify its link with major climatic and geomorphologic events in this article kaolinite rich samples from soils and saprolites belonging to a transect in the sao gabriel da cachoeira region amazon state brasil are investigated based on their crystal chemical characters several types of kaolinites are identified using a previously developed methodology based on electron paramagnetic resonance epr spectroscopy crystallization ages are proposed for these different kaolinites saprolite kaolinites are dated from 6 to 3 6 ma in the acrisol profile and display significantly more recent ages

high resolution records of climate change in arid eastern central asia during mis 3 51 600 25 300 cal a bp from wulungu lake north western china detailed records of climate change during the last glaciation in arid central asia are scarce here we present a sedimentological and geochemical record from wulungu lake in north western china providing the first high resolution continuous sedimentary records in this region covering marine isotope stage mis 3 51 600 25 300 cal a bp high lake power end member 2 values and bioproductivity concurrent with low terrigenous clastic input unanimously indicate high lake water levels during 46 180 39 770 31 680 30 080 and 27 780 26 540 cal a bp and moderately wet conditions during 51 600 46 180 and 39 770 31 680 cal a bp the lake attained its lowest water levels after 30 080 cal a bp few dry events characterized by high pool power end member 3 values and terrigenous input are documented for the studied interval and three of them are correlative with heinrich events 5 3 our study supports the hypothesis for a positive northern hemisphere july insolation anomaly which increased the temperature gradient between low and high latitudes increasing the strength of westerlies and increasing sea surface temperatures in the north atlantic resulting in more moisture transported to arid central asian by westerlies

loess deposits from the tajik depression central asia magnetic properties and paleoclimate abstract continuous accumulation of dust during the quaternary has formed widespread loess deposits in southern tajikistan the magnetic susceptibility variations of these aeolian sediments have recorded the paleoclimatic fluctuations in a similar direct and complete way to the well studied sediments from the central loess plateau in china 11 susceptibility measurements were carried out in situ at intervals of 10 cm along seven partly overlapping sections in the loess paleosol sequence of karamaidan ca 100 km east of dushanbe nearly 250 oriented samples were taken for rock magnetic investigations careful field observation revealed a total actual loess thickness of ca 100 m for a composite profile with thirteen intervening pedocomplexes pc standard demagnetization techniques yielded a characteristic component of natural remanent magnetization nrm which was used to obtain a well defined magnetostratigraphy the section covers a total timespan of approximately 1 m y including the brunhes and the youngest part of the matuyama polarity chron the susceptibility variations correlate excellently with those of the chinese loess record at xifeng 22 although minor differences in the relative amplitude of the susceptibility signal occur close correlation with the astronomically tuned oxygen isotope record 26 enables refined dating of the loess sequence at karamaidan and demonstrates the global significance of the recorded paleoclimatic variations especially with respect to paleoprecipitation on land during the quaternary

the loess record from the section at kurtak in middle siberia abstract loess loess like sediments and the intercalated palaeosols along the bluffs of the river yenisei provide a detailed upper pleistocene climate archive for the southern part of middle siberia the section at kurtak is one of the most detailed loess palaeosol sequences in middle siberia two major periods of sediment accumulation were recorded in the sequence the stratigraphically oldest one post dating the last interglacial palaeosol and pre dating the kurtak pedocomplex oxygen isotope stage ois 3 the younger one post dating the kurtak pedocomplex and predating the holocene soil three major phases of soil formation occurred during the upper pleistocene the kameny log pedocomplex ois 5e consists of at least two pedogenetic episodes a lower clayey chernozem forming during a more humid and warmer climate than today and an upper chernozem representing a drier climate than today the latter one including a well pronounced carbonate rich horizon the sukhoy log pedocomplex consists of a chernozem like palaeosol and two kastanozjems ois 5c a and the kurtak pedocomplex ois 3 with two chernozem like palaeosols and up to three humic rich layers additionally weakly developed gleyed horizons are considered to represent palaeohydrological groundwater high levels the results indicate a synchronous evolution of climate and environment change in both the more oceanic driven climate of west and central europe and middle siberia as evidenced by luminescence dating results

equatorial weathering landform development and the formation of white sands in north western kalimantan indonesia abstract the morphology and geochemistry of weathering profiles in miocene granodiorites from the coastal lowlands of nw kalimantan indonesia 1 n lat indicate long term weathering rates landform development and mechanisms for the formation of white sands found widely in valleys and depressions samples are analysed from convex hill piedmont glacis and valley slope profiles all profiles above the saturated zone are strongly gibbsitic but kaolinite minerals are dominant below the water table the profiles are interpreted as expressions of the perhumid equatorial climate rainfall 3000 mm y 1 acting within a dynamic regime of landscape lowering during the neogene the current profiles being largely quaternary 0 4 0 6 ka possible effects of quaternary tectonic and environmental changes are considered including those caused by a late pleistocene drier climate when there was greater water table fluctuation and surface erosion landform evolution is a form of dynamic etchplanation with a long term rate of landscape and weathering profile lowering of ca 50 mm ka 1 within this regime some of the white sands may be residual weathering products locally redistributed by colluvial or alluvial processes they originated in the podzolising environment of the weathering profile and later experienced post depositional diagenetic changes within the hydromorphic regime of the valley floor

a magnetic investigation of a late quaternary loess palaeosol record in siberia summary a late quaternary loess palaeosol sequence at kurtak in the yenisey river valley southern siberia has been studied magnetically the 34 m section 340 samples exhibits variations in magnetic susceptibility which can be correlated with oxygen isotope stages 1 7 a detailed sampling of stage 5 a further 209 samples permits the identification of substages 5a e the susceptibility variations themselves are in the opposite sense to that found in the classic sections of the chinese loess plateau but are in agreement with the wind intensity model which has been put forward to explain similar findings in loess sequences in alaska published results for the susceptibility of magnetite imply volume fractions of 0 2 per cent in glacial stages 2 and 4 dropping to 0 05 per cent in stages 1 3 and 5 these fluctuations match the aeolian flux variations observed in core v21 146 from the north pacific even though the warmer intervals are characterized by lower susceptibilities the observed frequency dependence of susceptibility indicates that new magnetic material is produced as a result of pedogenesis during interglacial and interstadial times

climate change in arid central asia since mis 2 revealed from a loess sequence in yili basin xinjiang china abstract k feldspar pirir dating was used to establish a chronological framework for the ks15 05 loess section in the yili basin northern xinjiang province china in arid central asia the reliability of the dating results was verified from the luminescence characteristics and internal checks the chronology was used to calculate mass accumulation rates mars for the section and the paleoclimatic proxies of grain size and magnetic susceptibility were also analyzed the high dust accumulation patterns during the last glacial maximum in yili basin are consistent with those of the chinese loess plateau clp on a millennial scale the bolling allerod b a interstadial is clearly reflected in the ks15 05 section by the variation of the 2 10 m grain size fraction suggesting the influence of the westerlies which dominate the modern atmospheric circulation of the region however the b a interstadial is poorly recorded in grain size records of the clp and this disparity may provide additional information about the nature of the transmission of climate signals from the north atlantic region to asia specifically the zonal transmission of the b a warm signal to the clp may have been obscured by the cooling effect of high latitude cold air to the north of the clp

distribution and characteristics of mesoscale cyclones in the antarctic ross sea eastward to the weddell sea abstract the mesoscale cyclone activity observed in the portion of antarctica that faces the south pacific ocean and weddell sea area is summarized from a study of 1991 in general area normalized results reveal much greater mesoscale cyclonic activity over the ross sea ross ice shelf and southern marie byrd land than on both sides of the antarctic peninsula more than 50 of the observed mesoscale vortices are of the comma cloud type the average diameter of mesoscale vortices is approximately 200 km near terra nova bay 270 km near byrd glacier and 280 km near siple coast near the antarctic peninsula the average diameter is about 370 km over the bellingshausen sea and 380 km on the weddell sea side the largest percentage of deep vortices occurs over the bellingshausen sea sector 38 of all cases where convective instability frequently occurs over the ross sea ross ice shelf and weddell sea sectors the majority of the mesoscale vortices are low cloud features that probably do not exceed the 700

simulations of topographically forced mesocyclones in the weddell sea and the ross sea region of antarctica abstract mesocyclones mcs are a frequently observed phenomenon in the coastal regions of antarctica numerical simulations of topographically forced mcs in the weddell sea and the ross sea region are presented using a three dimensional mesoscale weather forecast model simulations are performed for an idealized case without synoptic forcing three realistic cases of smaller mcs with diameters of 200 300 km and two larger systems with diameters of up to 1000 km the simulation results show that the orography of the coastal regions can play an important role in mesocyclogenesis one key factor is the katabatic wind system which is able to initiate low level mcs in areas of suitable orography structure the second key factor is the support of the synoptic environment leading to vorticity production by vertical stretching of the synoptically supported katabatic winds besides this stretching mechanism katabatic winds can have a second impact on the generation of mcs by transporting cold air into the coa

holocene dust deposition in the ili basin and its implications for climate variations in westerlies dominated central asia abstract understanding holocene paleoclimate in arid central asia aca is helpful for predicting future climate however holocene climate patterns and their forcing mechanisms across aca are vigorously debated in the context of global climate change here we present a holocene loess profile sgx from the ili basin in the westerlies dominated central asia based on high resolution medium grained 38 63 m quartz optically stimulated luminescence osl dating and grain size and color measurements we reconstruct the holocene paleoclimate osl geochronology indicate that this sgx loess profile covers the last 11 5 ka and grain size analyses reveal that the sediments are sandy loess and the environmentally sensitive fractions are

variation and paleoclimatic significance of organic carbon isotopes of ili loess in arid central asia as an indicator for terrestrial paleovegetation the stable isotopic composition of total organic matter delta c 13 org in loess sediments has been widely used for paleoclimatic reconstruction in western europe the great plains of north america and the chinese loess plateau clp however little is known about the variation and paleoclimatic significance of the loess delta c 13 org in arid central asia aca we report delta c 13 org data from an axike axk loess paleosol profile from the eastern ili basin eastern central asia along the profile the delta c 13 org values were more negative in the paleosol layers observed in the field and were confirmed by environmental magnetic proxies and a higher concentration of total organic carbon toc consistent with results for western europe and the northwestern clp our results demonstrate that the loess delta c 13 org in this region documents mainly the response of delta c 13 of locally predominant c 3 plants to paleoclimatic variation especially paleoprecipitation our results also suggest that the loess delta c 13 org values in the area have the potential for quantitative paleoprecipitation reconstruction on the basis of detailed delta c 13 org results from modern plants and surface soils in the future c 2013 elsevier ltd all rights reserved

reduction of systematic forecast errors in the ecmwf model through the introduction of an envelope orography day 1 forecast errors in the ecmwf model geopotential height fields during wintertime show a distinctive and highly reproducible signature with negative biases over the major mountain barriers these biases are largest on days when the 500mb flow over the mountains is strong and they tend to shift position from day to day so as to remain close to the region where the jet stream crosses the mountain barrier these systematic errors evolve through the forecast interval until by day 10 they assume an equivalent barotropic structure which strongly resembles the upper level stationary wave pattern but has the opposite sign which indicates that the model does not have sufficient presumably orographic forcing to maintain the stationary waves the time evolution of the systematic error pattern is investigated by means of a series of experiments with a barotropic model in which the observed mean wintertime 300 mb flow is perturbed by a steady forcing derived from the day 1 forecast error pattern the day 10 error patterns as simulated by the barotropic model bear a strong similarity to the observed ones the forcing in the vicinity of the northern rockies makes a particularly large contribution to the simulated day 10 error pattern whereas that in the himalaya region appears to be relatively less important the impact of an enhanced orography upon the climate of the ecmwf model is investigated by carrying out a pair of extended integrations out to 50 days the control run is based on the conventional average type orography used for operational forecasting the other run is based on an envelope orography constructed by adding to the conventional grid square averaged orography an increment proportional to the standard deviation of the sub grid scale variance results for this one rather short pair of integrations suggest that the envelope orography may be capable of yielding a more realistic simulation of the observed wintertime flow pattern particularly with respect to features in the pacific and western north american sectors certain aspects of the zonally averaged circulation are also more realistic in this envelope simulation a series of 21 successive ten day forecast integrations has also been carried out with this envelope orography from february 1982 data results indicate that the introduction of the envelope orography results in a slight degradation of the short range forecasts together with a distinct improvement of the forecast beyond four days the beneficial impact towards the end of the forecast interval appears to be large enough to increase the forecast usefulness by perhaps as much as half a day

the loess record in southern tajikistan and correlation with chinese loess in the present study the chashmanigar loess soil sequence in southern tajikistan is studied this loess section has a paleomagnetic basal age of about 1 77 myr magnetic susceptibility color reflectance and grain size were systematically measured for closely spaced samples from the section paleosols consistently have a finer grain size distribution higher magnetic susceptibility redder color reflectance and lower dust sedimentation rate than loess horizons suggesting a colder drier and dustier environment during glacial periods than in interglacial periods the grain size record was tuned to variations in obliquity and precession of the earth s orbit the resulting magnetic susceptibility grain size and color reflectance time series all show well expressed astronomical periodicities during the pleistocene the mid pleistocene climate transition characterized by a shift of dominant climatic periods from 41 kyr to 100 kyr at about 1 0 0 8 myr is clearly documented in these proxy records comparison of the chashmanigar loess record with the lingtai loess section in china and the odp site 677 n 18 o record shows that during the entire pleistocene the climate cycles recorded by the central asian loess can be well correlated to the chinese loess and deep sea oxygen isotope records it is suggested that alternations of loess and soil horizons both in central asia and china could be basically forced by global ice volume variations although different wind systems have controlled the pleistocene loess transport and sedimentation in the two areas 2002 elsevier science b v all rights reserved

influence of coupling on atmosphere sea ice and ocean regional models in the ross sea sector antarctica air sea ice ocean interactions in the ross sea sector form dense waters that feed the global thermohaline circulation in this paper we develop the new limited area ocean sea ice atmosphere coupled model tango to simulate the ross sea sector tango is built up by coupling the atmospheric limited area model mar to a regional configuration of the ocean sea ice model nemo a method is then developed to identify the mechanisms by which local coupling affects the simulations tango is shown to simulate realistic sea ice properties and atmospheric surface temperatures these skills are mostly related to the skills of the stand alone atmospheric and oceanic models used to build tango nonetheless air temperatures over ocean and winter sea ice thickness are found to be slightly improved in coupled simulations as compared to standard stand alone ones local atmosphere ocean feedbacks over the open ocean are found to significantly influence ocean temperature and salinity in a stand alone ocean configuration the dry and cold air produces an ocean cooling through sensible and latent heat loss in a coupled configuration the atmosphere is in turn moistened and warmed by the ocean sensible and latent heat loss is therefore reduced as compared to the stand alone simulations the atmosphere is found to be less sensitive to local feedbacks than the ocean effects of local feedbacks are increased in the coastal area because of the presence of sea ice it is suggested that slow heat conduction within sea ice could amplify the feedbacks these local feedbacks result in less sea ice production in polynyas in coupled mode with a subsequent reduction in deep water formation

on the glaciological meteorological and climatological significance of antarctic blue ice areas this paper presents the current state of our knowledge about antarctic blue ice areas scattered widely over the antarctic continent yet covering only approximately 1 of its surface area blue ice areas have some peculiar characteristics that make them of particular interest for planetary geologists glaciologists meteorologists and climatologists for instance blue ice areas are subject to net ablation mainly by sublimation since any accumulation is easily swept off their smooth surfaces by winds moreover they are significantly warmer than their surroundings and the wind over them is generally more gusty an important feature of blue ice is its relatively low albedo 0 56 compared with that of snow 0 80 blue ice is probably considerably smoother than snow in the aerodynamic sense with roughness lengths as low as 3 10 6 m which indicates that blue ice is probably the only permanent natural surface over which the air flow is mainly in the aerodynamic smooth regime further since it is likely that very old ice is exposed at the surface of some blue ice areas this ice would be of great interest for paleoclimatic studies it has also been suggested that blue ice areas are sensitive to climate change this would make them useful as antarctic climate indicators because they can easily be monitored by satellite finally this paper addresses several gaps in our knowledge about blue ice areas and gives suggestions for future blue ice area research

holocene climatic and environmental changes in the arid and semi arid areas of china a review this paper reviews recently published literature most of which was published in chinese and searches for regional patterns of holocene changes useful in depicting global patterns the holocene in the xinjiang region can be divided into three stages a warming and dry early stage from 11 similar to 10 to 8 similar to 7 ka bp a warm and wet middle stage from 8 similar to 7 to 4 5 similar to 3 ka bp and a fluctuating cool and dry late stage since 4 5 similar to 3 ka bp the holocene in the northern tibetan plateau can also be divided into three stages a warming and wet stage from 10 5 similar to 10 to 5 similar to 4 ka bp followed by a variable drying and probably warm stage 5 similar to 4 to 3 ka bp and ending with a cool and dry stage since 3 ka bp in the inner mongolian plateau the early holocene from 10 5 similar to 9 5 to 8 similar to 7 5 ka bp was warming and dry and a warm and wet climate occurred from 7 5 to 3 5 during which the best time was 6 3 3 8 ka bp the climate has been variably drying and probably cooling since 3 5 ka bp in the northwestern part of the loess plateau several holocene palaeosols have been identified 10 9 7 5 5 4 3 and 2 7 2 ka bp with the 7 5 5 ka bp palaeosol being most strongly expressed the best developed palaeosol equivalent in major valleys is a swamp wetland facies deposited between 8885 and 3805 c 14 yr bp under an extremely wet regime the climate has fluctuated significantly at least three times around a dry and probably cool regime after the swamp wetland facies depositional period our summary shows that the holocene climatic optimum occurred nearly contemporaneously 8 5 ka bp at all sites in the xinjiang region in the inner mongolian plateau and in the northwestern part of the loess plateau a warming and wet early holocene 10 8 ka bp in the northern tibetan plateau is most likely related to high effective soil moisture resulting from snow and ice melting we propose here that the middle holocene climatic optimum 8 5 ka bp in arid to semi arid china was primarily a delayed response of the low latitude oceans to high latitude peak insolation 9 8 ka bp

distribution and composition of loess sediments in the ili basin central asia loess deposits in central asia provide an important record of regional climate and environmental change however in contrast to the intensively investigated loess deposits on the chinese loess plateau clp loess sediments in the ili basin of eastern central asia are poorly understood based on field investigation and existing literature this paper presents a preliminary study of the distribution strata and composition of the ili loess the distribution of the ili loess is clearly controlled by topographic and geomorphic conditions mainly in the river terraces low uplands and slopes of the tianshan mountains the thickness of the loess varies from several meters to over two hundred meters to characterize the ili loess composition the authors analyzed its grain size geochemistry x ray diffraction pattern and heavy mineral assemblage grain size analyses reveal that the ili loess consists predominantly of silt 4 63 mu m with a minor proportion of sand which is coarser than the loess of the clp and suggests a nearby provenance the bulk mineral components of the ili loess are dominated by quartz and feldspar with minor amounts of calcite chlorite mica dolomite and hornblende more than 20 types of heavy minerals were observed with major components of amphibole magnetite and epidote the major elements of the ili loess are characterized by high abundance of sio2 al2o3 and cao and minor amounts of fe2o3 mgo na2o and k2o compared to the clp loess the ili loess is relatively rich in na2o and displays higher na2o al2o3 ratios suggesting weak weathering the distribution patterns of rees indicate that both the ili loess and clp loess are of typical upper crustal composition with enrichment in lree negative eu anomalies and depletion of hree both the heavy mineral assemblage and geochemistry indicate that the local bedrock of the ili basin may have contributed only a little to the loess sediments c 2014 elsevier ltd and inqua all rights reserved

contemporary glacigenic inputs to the dust cycle the importance of glacigenic dust in the earth s system during glacial periods is widely acknowledged under contemporary conditions the world s largest dust sources are in low lying hot arid regions and this is where most aeolian research is focused however the processes of dust production and emissions are still operating in cold climate regions particularly in proglacial areas this paper assesses current understanding of the relationship between glacierised landscapes and dust emissions and inputs to the global dust cycle it focuses on how elements in the glacial and aeolian geomorphic sub systems interact to determine the magnitude frequency and timing of aeolian dust emissions and on feedback mechanisms between the systems where they have been measured dust emission intensity and deposition rates in glacierised catchments are very high in some cases far exceeding those in lower latitudes however few studies span long time scales the impact of future glacier retreat on the balance between sediment supply availability and aeolian transport capacity and implications for glacigenic dust emissions is also considered this balance depends on relative spatial and temporal changes in meltwater suspended sediment concentration and wind strengths which promote dust emissions and patterns and rates of soil development and vegetation succession on recently deglaciated terrain which protect sediments from deflation retreat of the antarctic ice sheet could mean that in future glacigenic contributions to the dust cycle exceed those of non glacigenic sources in the southern hemisphere copyright 2012 john wiley sons ltd

rating curves and estimation of average water depth at the upper negro river based on satellite altimeter data and modeled discharges summary the objective of this study is to derive the stage discharge relationship for 21 virtual gauge stations located at the upper negro river amazon basin brazil a virtual station can be defined as any crossing of water body surface i e large rivers by radar altimeter satellite tracks rating curve parameters are estimated by fitting with a power law the temporal series of water surface altitude derived from satellite measurements and the discharge discharges are calculated using progum a flow routing model based on the muskingum cunge m c approach considering a diffusion cum dynamic wave propagation leon j g bonnet m p cauhope m calmant s seyler f submitted for publication distributed water flow estimates of the upper negro river using a muskingum cunge routing model based on altimetric spatial data j hydrol among these parameters is the height of effective zero flow measured from the wgs84 ellipsoid used as reference it is shown that the height of effective zero flow is a good proxy of the mean water depth from which bottom slope of the reaches can be computed and manning roughness coefficients can be evaluated mean absolute difference lower than 1 1 m between estimated equivalent water depth and measured water depth indicates the good reliability of the method employed we computed the free surface water slope from envisat altimetry data for dry and rainy seasons these profiles are in good agreement with the bottom profile derived from the aforementioned water depths also the corresponding manning coefficients are consistent with the admitted ranges for natural channels with important flows superficial width 30 5 m chow v t 1959 open channel hydraulics mcgraw hill new york and irregular section

how much deep water is formed in the southern ocean three tracers are used to place constraints on the production rate of ventilated deep water in the southern ocean the distribution of the water mass tracer po4 phosphate star in the deep sea suggests that the amount of ventilated deep water produced in the southern ocean is equal to or greater than the outflow of north atlantic deep water from the atlantic radiocarbon distributions yield an export flux of water from the north atlantic which has averaged about 15 sv over the last several hundred years cfc inventories are used as a direct indicator of the current production rate of ventilated deep water in the southern ocean although coverage is as yet sparse it appears that the cfc inventory is not inconsistent with the deep water production rate required by the distributions of po4 and radiocarbon it has been widely accepted that the major part of the deep water production in the southern ocean takes place in the weddell sea however our estimate of the southern ocean ventilated deep water flux is in conflict with previous estimates of the flux of ventilated deep water from the weddell sea which lie in the range 1 5 sv possible reasons for this difference are discussed

mesoscale cyclogenesis dynamics over the southwestern ross sea antarctica previous work has shown that frequent mesoscale cyclogenesis adjacent to franklin island is linked to the strong and persistent katabatic winds from east antarctica which funnel into terra nova bay and then blow out over the southwestern ross sea four mesoscale cyclones that formed near terra nova bay between february 16 and 20 1988 are examined to more clearly define the governing mechanisms these events are investigated using all available observations including automatic weather station data high resolution satellite images satellite soundings and hemispheric synoptic analyses the first two cyclones formed on low level baroclinic zones established by the synoptic scale advection of warm moist air toward the cold continental air blowing gently from east antarctica in the second case baroclinic instability of this small scale cold front was apparently triggered by the enhanced upward vertical motion associated with the approach of a midtropospheric trough the third mesocyclone formed shortly after on a baroclinic zone over the polar plateau the second vortex completely disrupted the usual katabatic drainage over the plateau and forced warm moist air over the coastal slopes all three cyclones moved to the north in the prevailing cyclonic flow but the plateau vortex lasted for only 6 hours the fourth mesoscale low formed in conjunction with an abrupt and intense surge of katabatic air from terra nova bay which resharpened the coastal baroclinic zone at the same time a transiting midtropospheric trough probably associated with lower tropospheric upward vertical motion apparently accelerated the katabatic winds and triggered the vortex formation a similar katabatic wind forced mesocyclone formed near byrd glacier the two vortices moved to the east southeast and northeast respectively apparently being steered by the generating katabatic airstreams and merged just to the north of the ross ice shelf the combined vortex reintensified as another trough passed overhead and moved eastward to west antarctica where it dissipated two days later

surface winds over the antarctic continent a review surface winds over antarctica often classified as katabatic are intimately related to the orientation and steepness of the underlying ice terrain such flows result primarily from the strong radiational cooling of the sloping ice surface which creates a downslope directed horizontal pressure gradient force it is possible to diagnose the time averaged near surface streamline patterns of cold air drainage currents using recently compiled detailed antarctic ice topography maps and appropriate estimates of the strength of the surface temperature inversion the resulting streamlines agree with available observations and illustrate the high degree of nonuniformity of gravity driven flows off the ice sheets in certain interior sections negatively buoyant air from a large catchment area drains through a restricted section of coastline such confluence zones represent regions of enhanced supplies of cold air and are shown to be related to anomalously strong katabatic winds implications for sea ice formation are discussed

contrasting environmental memories in relict soils on different parent rocks in the south western italian alps abstract soils on the alps are usually weakly developed both because of the extensive pleistocene glaciations and because of slope steepness and climate enhancing erosion however on some stable relict surfaces particularly in the outermost sections of the alpine range some highly developed soils are apparently in contrast with holocene soil forming conditions in this work we assess the extent of pedogenesis in some of these soils located under montane level vegetation in the ligurian alps sw piemonte italy and relate it to the effects of climate and parent material the considered well developed profiles showed signs of extremely different pedogenetic processes on the different lithotypes in particular podzols with extremely thick e horizons up to more than 2 m thick and very hard thick ortstein or placic horizons were formed on quartzite reddish terra rossa luvisols were formed on limestone red extremely acidic alisols were formed on shales the chemical properties the micromorphology and the clay mineralogy demonstrated high intensity pedogenic trends and were characteristic of processes usually occurring under different climates they may therefore represent excellent pedo signatures of different specific past climatic environmental conditions as a response of different lithologies to specific soil forming environments which range from warm and humid climates typical of red alisols and luvisols to cool and humid wet climates leading to the formation of podzols with ortstein placic horizons

chronological discord between the last interglacial paleosol s1 and its parent material in the chinese loess plateau abstract an and porter geology 25 1997 603 reported six high dust influx events of millennial timescales recovered from the last interglacial paleosol s1 and correlated them to six cool events of millennial timescale in the north atlantic however the complexity of soil forming processes may have made the chronological correlation with the north atlantic records inadequate to examine the complexity of the s1 formation the s1 paleosol was traced laterally and identified based on the preserved characteristics observed in the field and analyzed in the laboratory our data show that from the northwest to the southeast the s1 paleosol gradually converges from three distinctive soil profiles into a single welded profile because the net rate of loess accumulation was attenuated to the southeast and pedogenic development intensified southeastward during the last interglacial three soil forming events within the s1 paleosol s1s1 s1s2 and s1s3 separated by two loess units s1l1 and s1l2 in the northwestern part of the loess plateau are stratigraphically coeval with a single soil profile in the southeastern margin of the loess plateau in the southeast the s1 paleosol developed into underlying older loess l2 e g at the lantian section the three paleosols s1s1 s1s2 and s1s3 are partially welded in the central part of the chinese loess plateau e g at the tianshui section where the lower portion of s1 paleosol developed in the underlying older loess unit l2 in the northwestern margin of the chinese loess plateau e g at the lanzhou section the preservation of the repeating soil loess sequence s1s1 s1l1 s1s2 s1l2 and s1s3 continuously documented the climatic events of the last interglacial our data also show that the magnetic signatures and particle size information are more or less acceptable climatic proxies only for the northwestern sections where the degree of pedogenesis was lower and the rate of eolian influx was greater during the last interglacial it appears that in all cases investigated the median grain size and the coarse fraction 63 m content define the upper and lower boundaries of the s1 paleosol reasonably well and can be used to estimate the time transgressive nature of the s1 paleosol relative to its parent material soil welding bioturbation and material translocation within the s1 soil profiles make it impossible to preserve the detailed and high resolution information of climate changes in those s1 profiles in the southeastern part including the popularly called central part of the chinese loess plateau

simulation of the net snow accumulation along the wilkes land transect antarctica with a regional climate model regional climate modelling in conjunction with accumulation measurements collected on antarctic traverses of the international trans antarctic scientific expedition itase is presented as a tool for extending the spatial coverage of field measurements the modelling of part of east antarctica spanned the 7 year epoch 1980 86 where data covering the same period are available the agreement between simulation and observation is improved when a parameterization of the snow surface redistribution processes such as wind erosion is included in the regional climate model the modelled spatial distribution of the net snow mass transported in the boundary layer over coastal east antarctica indicates that this mass is a significant component of the surface mass balance

reevaluation of late pleistocene loess profiles at remizovka kazakhstan indicates the significance of topography in evaluating terrestrial paleoclimate records we report on a loess paleosol sequence lps near remizovka located in the northern tian shan piedmont of southeastern kazakhstan this site represents a key record for late pleistocene climatic fluctuations at the intersection of major northern hemisphere climate subsystems this paper develops a synthesized dataset of previous conflicting studies at remizovka by characterizing their paleo topographic context which had remained previously overlooked digital elevation models satellite images and archival photography characterize recent topographic developments two well developed pedocomplexes which we investigate in detail and date by luminescence mark the paleotopography during marine oxygen isotope stage mis 5 peak dust accumulation rates here occurred during the middle mis 5 and mis 4 early mis 3 these are partially comparable with records from neighboring regions but not in phase with global ice volume records this discrepancy may be related to a distinct regional environmental response to larger scale climatic drivers and local topographic influences on dust deposition patterns our findings confirm the potential of the lps remizovka to provide high resolution paleoclimate data for the late pleistocene the three dimensional stratigraphic reconstruction reinforces the caution required to correctly interpret loess formation processes prior to their interpretation as paleoclimate archives and provides guidelines for a more suitable approach

geographic variations in particle size distribution of the last interglacial pedocomplex s1 across the chinese loess plateau their chronological and pedogenic implications abstract due to northwestward attenuation of the summer monsoon and northwestward intensification of loess deposition during the last interglacial the last interglacial pedocomplex s1 gradually differentiated from the northwest to the southeast the three paleosols s1s1 s1s2 s1s3 corresponding to the marine isotope sub stages 5a 5c and 5e and the two intercalated loess units s1l1 s1l2 corresponding to the marine isotope sub stages 5b and 5d are completely preserved at northwestern sections towards southeast both the s1l1 and s1l2 were annexed by the subsequent paleosol development s1s1 and s1s2 and the three paleosols s1s1 s1s2 and s1s3 were partially welded at the southeasternmost site the three soil forming events s1s1 s1s2 and s1s3 repeatedly occurred in a single paleosol profile the three observed orders of particle size variations are interpreted to have imprinted important chronological and pedogenic signatures first order variations i e a remarkable difference between the interglacial pedocomplex s1 and the glacial loess units l1 and l2 implies that the s1 parent material was considerably finer in the source areas or and the proximity to the source areas was much farther during interglacial period than during the preceding l2 and following l1 glacial periods second order variation i e the parenthetical trends in 63 m and

prehistoric maritime migration in the pacific islands an hypothesis of enso forcing long distance human migration across the pacific ocean occurred during the late holocene and originated almost entirely in the west as prevailing tradewinds blow from the east the mechanisms of p

forest changes in the amazon basin during the last glacial maximum we report here the discovery of forest beds in the amazon basin radiocarbon dated to the wisconsin wurm glaciation these are the first dates from the last glaciation determined on amazonian samples the locality is in ecuador at 1 100 m elevation near the upper limit of the present amazonian rainforest both pollen spectra and podocarpus wood in the deposits suggest that vegetation comparable to the present andean forest grew at least 700 m lower than it does now suggesting a temperature depression of at least 4 5 c for the amazon lowlands

paleoenvironmental changes recorded in a luminescence dated loess paleosol sequence from the tianshan mountains arid central asia since the penultimate glaciation abstract mid latitude arid central asia aca is one of the driest regions in the world and is a key source area of global atmospheric dust loess records of paleoclimatic changes in aca are complex and interpretations are problematic due primarily to the lack of robust chronologies quartz osl and k feldspar pirir dating methods were employed to date 8 quartz and 30 k feldspar samples from a 30 m loess sequence byh10 section on the northern slope of the tianshan mountains central aca northwest china the reliability of quartz and k feldspar ages was monitored by internal checks of luminescence characteristics and by comparison of the quartz and k feldspar ages the section lithology proxy indexes of grain size and magnetic susceptibility and the high resolution osl chronology together indicate 1 quartz osl dating can be used to date aca loess samples less than 40 ka while k feldspar pirir dating is reliable for loess samples at least as old as 150 ka from aca 2 aeolian loess began to be deposited on the northern slope of tianshan mountains beginning at least 145 ka ago and was deposited primarily during the penultimate and last glaciation periods 3 rapid loess deposition occurred during mis 6 mis 4 to early mid mis 3 and mis 2 but little or no loess deposition occurred during mis 5 mis 3a and mis 1 4 this loess depositional sequence is comparable to previously published stalagmite growth records in the region on glacial interglacial cycles rapid dust deposition and lack of stalagmite growth during glacials and lack of loess deposition and stalagmite growth during interglacials indicate a climatic pattern of wet warm interglacial and dry cold glacial climatic regimes on orbital cycles in aca 5 variation in the loess deposition rates in aca was much larger than in the central loess plateau during the last glaciation 6 depositional hiatuses of 50 kyr occur in aca loess sequences and high resolution chronologies are needed when reconstructing past climatic changes

asynchronous holocene climate optimum across mid latitude asia abstract the holocene climate optimum hco was an important interval in the development of human civilization and has been the focus of many paleoclimatic studies however there are significant regional differences in the timing of the hco due to the complex response of regional climates to insolation changes associated with internal feedbacks within the climate system here we present the results of a study of magnetic and geochemical properties of loess paleosol sequences from across mid latitude asia with the aim of assessing differences in the timing of the hco the hco generally occurred after 5 ka in tajikistan and xinjiang during 5 2 5 ka in the western chinese loess plateau clp and during 8 2 5 ka in the central clp this asynchroneity reflects differences in the response of regional climates to global climate change specifically the difference in timing between the central and western clp may have been related to shifts in the position of the east asian summer monsoon rain belt due to the changing longitudinal position of the western pacific subtropical high together with changes in the east west thermal gradient in the equatorial pacific i e shifts between la nina and el nino conditions

loess accumulation in the tian shan piedmont implications for palaeoenvironmental change in arid central asia whilst correlations have been made between the loess of europe and china deposits in central asia have remained largely overlooked by scientific investigation the nature of the relationship between loess accumulation and palaeoclimate at the core of the eurasian loess belt is particularly poorly understood here we reconstruct palaeoenvironmental change in central asia over the last 40 ky based on data from the remizovka loess profile in the northern foothills of the tian shan in southern kazakhstan our interpretations are based on synthesis of chronostratigraphic colour and magnetic susceptibility data supported by chronostratigraphies from two additional sites nearby maibulak and valikhanova all three sites record substantially increased loess accumulation during late mis 3 into the global last glacial maximum glgm at remizovka increased loess flux occurred in two pulses at c 38 25 ka and 22 18 ka with the intervening period involving incipient pedogenesis at maibulak two loess pulses at c 40 30 ka and c 28 22 ka are separated by a weakly developed paleosol which may date to the same time as pedogenesis at remizovka there is additional possible periglacial influence at maibulak from c 40 33 5 ka at valikhanova there is some age overlap between paleosol and loess samples but overall loess accumulation appears to have increased at c 42 35 ka c 30 ka and the glgm with pedogenesis occurring 40 ka and c 32 ka at all three sites holocene loess accumulation is minimal this period is characterised by pedogenesis the chronostratigraphic variability between our sites highlights a need to interrogate climate driven models for loess formation in piedmont environments we interpret our data in the context of regional palaeoenvironmental archives to indicate that loess accumulation increased coeval with mis 3 glacial advance in the tian shan which was facilitated by northward expansion of the asian monsoon and associated increase in precipitation we hypothesise that increased ice volume impeded teleconnections with the temperate zone westerlies to the north these were compressed against the piedmont resulting in increased wind strength and facilitating increased loess flux peak loess accumulation during the glgm occurred under colder drier climatic conditions with reduced but sustained glacial ice volume and persistent influence of the westerlies in the arid central asian piedmont loess belt in the absence of more widespread reliably dated palaeoenvironmental records from the region our data become of critical importance for understanding past environmental conditions in central asia relative to elsewhere in eurasia and globally

grus weathering mantles problems of interpretation abstract grus is an ill defined product of deep weathering of coarse grained rocks whose relationships to other weathering changes remain unclear this paper attempts to address this issue by reviewing a number of examples of coarse saprolites from a variety of climatic and topographic settings grus is the category of weathering mantle that possesses the following characteristics sand gravel 75 100 silt clay

a new subgrid scale orographic drag parametrization its formulation and testing a scheme for the representation of subgrid scale orography sso in numerical weather prediction and climate models is presented the new scheme arose in part from a desire to represent nonlinear low level mountain drag effects not currently parametrized an important feature of the scheme is that it deals explicitly with a low level flow which is blocked when the effective height of the subgrid scale orography is sufficiently high in this new scheme it is assumed that for this blocked flow separation occurs at the mountain flanks resulting in a form drag this drag is parametrized on model levels which are intersected by the sso and provides a dynamically based replacement for envelope orography the upper part of the low level flow goes over the orography and generates gravity waves at the model resolutions considered t106 and t213 it is assumed that the length scales characteristic of the sso are sufficiently small for the coriolis force to be neglected the various parameters of the scheme are adjusted using an off line procedure in which the scheme is used to estimate the mountain drag and the momentum profiles above the pyrenees and these estimates are validated with the pyrex data forecasts using t106 and t213 resolutions with this new scheme and with mean orography show that the forecast mountain drag consistently reproduces the drag measured during pyrex whenever the flow component normal to the ridge is large isentropic flow diagnostics further show that the new scheme has a realistic impact on the flow dynamics reinforcing the low level wake observed in mesoscale analyses of the flow with this new scheme and a mean orography the ecmwf model outperformed in forecast skill a version of the model which had an envelope orography and the old gravity wave drag scheme while no longer suffering any disadvantages of envelope orography the proposed low level drag parametrization should also be relevant at model horizontal resolutions much higher than t213

problems arising from fixed depth assessment of deeply weathered sandy soils abstract practicality dictates a limit to the depth of routine soil examination but for some deeply weathered soils the prescribed depth is not sufficient to establish a full genetic context failure to account for all related soil features on a landscape by ignoring features below a fixed depth e g 2 m can result in i inconsistent genetic interpretations and ii an inaccurate and disjointed depiction of soils on the landscape the upper boundary of some b horizons in sandy soils undulates above and below 2 m depth on the same landform considering only the upper 2 m of such soils yields a truncated tip of the iceberg impression some quartzipsamments on older surfaces have horizons below 2 m that are contiguous with b horizons of spatially associated ultisols or spodosols they hence are well developed soils rather than undeveloped a c soils with an illuvial layer below the depth of consideration an e horizon of an ultisol or spodosol does not change to a c horizon as the illuvial horizon dips below an arbitrary depth 2 m and as the order changes to entisol quartzipsamments however are often described in such settings as a c soils soil taxonomic systems can be validly applied with fixed depth maxima as long as full context genetic interpretations are made prior to and independently of the classification it is not necessary to bore routinely below conventional limits since deep horizons can generally be inferred from i periodically encountering them at shallower depths and ii observing them regionally in deep excavations