sedimentary pyrite formation an update sedimentary pyrite formation during early diagenesis is a major process for controlling the oxygen level of the atmosphere and the sulfate concentration in seawater over geologic time the amount of pyrite that may form in a sediment is limited by the rates of supply of decomposable organic matter dissolved sulfate and reactive detrital iron minerals organic matter appears to be the major control on pyrite formation in normal non euxinic terrigenous marine sediments where dissolved sulfate and iron minerals are abundant by contrast pyrite formation in non marine freshwater sediments is severely limited by low concentrations of sulfate and this characteristic can be used to distinguish ancient organic rich fresh water shales from marine shales under marine euxinic conditions sufficient h2s is produced that the dominant control on pyrite formation is the availability of reactive iron minerals calculations based on a sulfur isotope model indicate that over phanerozoic time the worldwide average organic carbon to pyrite sulfur ratio of sedimentary rocks has varied considerably high cs ratios during permo carboniferous time can be explained by a shift of major organic deposition from the oceans to the land which resulted in the formation of vast coal swamps at that time low cs ratios compared to today during the early paleozoic can be explained in terms of a greater abundance of euxinic basins combined with deposition of a more reactive type of organic matter in the remaining oxygenated portions of the ocean the latter could have been due to lower oceanic oxygen levels and or a lack of transportation of refractory terrestrial organic matter to the marine environment due to the absence of vascular land plants at that time

quantitative reconstruction of middle and late eocene paleoclimate based on palynological records from the huadian basin northeastern china evidence for monsoonal influence on oil shale formation abstract the eocene was an interval of climate evolution when the extreme high temperatures of the earliest cenozoic gave way to a global cooling trend fine grained lacustrine sediments of eocene age from northeastern china represent an excellent archive to study long term environmental and climatic changes at high resolution the huadian basin is a cenozoic fault bounded basin in jilin province northeastern china though small in area it contains numerous oil shale and coal bearing layers which provide an abundant middle to late eocene palynoflora eighty five palynomorph genera and one hundred palynomorph species were identified in the huadian formation allowing to distinguish 4 palynozones the nearest living relatives of the recovered palynomorph taxa suggest the presence of subtropical evergreen and deciduous broad leaved forests during deposition of the huadian formation using the coexistence approach ca we calculated seven paleoclimatic parameters which indicate a subtropical warm and humid climate with a mean annual temperature above 13 6 c and a mean annual precipitation of at least 887 mm however the climate became cooler and drier during the transition from the lower oil shale member to the upper carbonaceous shale member palaeoclimatic data from the various middle and late eocene basins of northeastern china i e the huadian fushun yilan hunchun and jishu basins were compared with data from north american and european basins middle eocene climate in the northern hemisphere was generally warm and humid and the mean annual temperature and precipitation in northeastern china were similar to those in north america though slightly lower than those of europe similar trends in temperature and precipitation on different continents support the existence of a global mid eocene cooling event this paper is the first systematic study of middle to late eocene seasonality in the huadian basin our results show an apparent differentiation in both temperature and precipitation between summer and winter supporting the view that the east asian monsoon was established in northeastern china already during the middle to late eocene this middle and late eocene monsoon was likely driven by the development of pacific trade winds and an alternating seasonal high and low pressure system over siberia the climatic changes observed in our dataset especially the precipitation changes appear to have played an important role in controlling oil shale formation in the huadian basin a warmer and more humid climate with abundant precipitation and high subsidence rates formed a deeper huadian depositional lake high productivity and stable stratification provided the abundant organic matter and favorable preservation conditions necessary for oil shale accumulation

spatial variability of antarctic peninsula net surface mass balance 1 measurements from ice cores and snow pits collected over the last 50 years are used to examine how net surface mass balance varies across the antarctic peninsula to give the first detailed map of mass balance for the region a total of 211 reliable mass balance measurements were available for the preparation of the map but some areas were found to be very data sparse the analysis suggests that the largest values of mass balance are found along the spine of the northern part of the peninsula where over 2 5 m yr 1 water equivalent we has been measured a secondary peak of more than 2 0 m yr 1 we is determined along the mountains of eastern alexander island precipitation minus evaporation p e fields from the european centre for medium range weather forecasts reanalysis project are compared with our analysis of in situ data the model fields are found to have peak values of p e of only half the amounts found from the measurements the greatest model values are located on the western side of the peninsula areas where a high density of in situ data is available including king george vi sound and the high south central plateau part of the peninsula show a high spatial variability of net surface mass balance suggesting that local orographic features play a major part in dictating the mass balance

biomarkers of oligocene lacustrine source rocks beibuwan song hong basin junction offshore northern vietnam abstract highly oil prone source rocks containing sapropelic type i and mixed types i and iii kerogen are found in 233 m of the 500 m deep fully cored enreca 3 well drilled on bach long vi island located at the junction between the beibuwan and the song hong basins offshore northern vietnam the cored succession is made up entirely by oligocene deep lacustrine deposits the origin of the organic matter om in 62 samples is evaluated on the basis of gas chromatography mass spectrometry gc ms and gc ms ms om in 55 samples is sourced primarily from lacustrine organisms and contains abundant 4 methylsteranes tetracyclic polyprenoids tpp and lycopane and no markers for marine organic matter the proportion of triterpanes derived from angiosperms is low in most saturated fractions and only traces of gymnosperm diterpanes are detected in contrast all aromatic fractions have a high proportion of compounds having an origin from both gymnosperms and angiosperms very high concentrations of hopanoids in both fractions suggest significant bacterial alteration of the original om most samples have a high concentration of rare c31 diaromatic 8 14 secohopanes with a fluorene moiety low pristane phytane pr ph ratios indicate that anoxic suboxic bottom water conditions existed during om accumulation the presence of carotane gammacerane and traces of arylisoprenoids could indicate a stratified water column om in a few samples with lower than average hydrogen index hi is mainly of terrestrial origin with a higher proportion of c29 steranes diterpanes and oleanoids and lower concentrations of both saturated and aromatic hopanes higher pr ph a higher c34 isohopane ratio ihr34 and a lower homohopane index hhi indicate that this low hi om was originally deposited under more oxic conditions and subsequently transported to deeper water low sterane and hopane isomerization ratios show that no samples have reached the oil window some novel maturity parameters for immature lacustrine samples are proposed

depositional environment of oil shale within the second member of permian lucaogou formation in the santanghu basin northwest china abstract the non marine santanghu basin in northwest china hosts one of the richest and thickest permian lacustrine source rock intervals in the world conventional oil in jurassic sandstone reservoirs and tight oil in the tuffaceous permian tiaohu formation were sourced from mudrocks in the underlying second member of lucaogou formation which also have tight oil potential proved by recent commercial discoveries based on inorganic and organic geochemistry organic petrography and stable isotope geochemistry the depositional environment and the tight oil potential of the second member of permian lucaogou formation were investigated the data imply a gradual evolution of the depositional environment from a stratified saline to a freshwater lake the succession can be subdivided into a lower middle and an upper unit each characterized by decreasing water salinity high bioproductivity has been caused by the bloom of algae and photosynthetic cyanobacteria water column stratification accelerated the activity of methanothrophs as indicated by low 13c values of hopanes biomarker composition provides evidence for decreasing contributions of cyanobacteria to the biomass and increasing abundance of prasinophytae compared to other algae with decreasing salinity enhanced terrigenous organic matter input appeared during periods of high freshwater inflow low total organic carbon toc contents in the lower unit are most likely caused by rapid sedimentation rate high bioproductivity and excellent preservation conditions resulted in high toc contents in the middle unit terrigenous organic matter input increased together with fresh water inflow in the upper unit resulting in high toc values during periods of possibly low sedimentation rates in a deep water column the samples of the second member exhibit a good to very good potential to generate conventional oil high toc and extractable organic matter yields together with the thickness of the fine grained sediments show that the middle and upper units of the second member of lucaogou formation hold significant tight oil potential mineralogical composition of this dolomite rich shale with respect to abundance of brittle minerals including quartz and carbonates and rare clay testifies a good tight oil potential

spatial patterns of variability in antarctic surface temperature connections to the southern hemisphere annular mode and the southern oscillation 1 the 17 year 1982 1998 trend in surface temperature shows a general cooling over the antarctic continent warming of the sea ice zone with moderate changes over the oceans warming of the peripheral seas is associated with negative trends in the regional sea ice extent effects of the southern hemisphere annular mode sam and the extrapolar southern oscillation so on surface temperature are quantified through regression analysis positive polarities of the sam are associated with cold anomalies over most of antarctica with the most notable exception of the antarctic peninsula positive temperature anomalies and ice edge retreat in the pacific sector are associated with el nino episodes over the past two decades the drift towards high polarity in the sam and negative polarity in the so indices couple to produce a spatial pattern with warmer temperatures in the antarctic peninsula and peripheral seas and cooler temperatures over much of east antarctica

breakup and conditions for stability of the northern larsen ice shelf antarctica the breakup of ice shelves has been widely regarded as an indicator of climate change1 with observations around the antarctic peninsula having shown a pattern of gradual retreat associated with regional atmospheric warming and increased summer melt and fracturing processes2 3 4 5 6 7 8 9 the rapid collapse of the northernmost section of the larsen ice shelf larsen a over a few days in january 1995 indicated that after retreat beyond a critical limit ice shelves may disintegrate rapidly here we use a finite element numerical model that treats ice as a continuum without fracture10 to examine the breakup history2 between 1986 and 1997 of the two northern sections of larsen ice shelf larsen a and larsen b from which we establish stability criteria for ice shelves analysis of various ice shelf configurations reveals characteristic patterns in the strain rates near the ice front which we use to describe the stability of the ice shelf on larsen a only the initial and final ice front configurations show a stable pattern larsen b at present exhibits a stable pattern but if the ice front were to retreat by a further few kilometres it too is likely to enter an irreversible retreat phase

methylhopanoids molecular indicators of ancient bacteria and a petroleum correlation tool abstract methylhopanoids are organic compounds synthesized by certain bacteria that when preserved in sediments act as molecular fossils or biomarkers for organic matter inputs from specific bacterial sources two series of methylhopanoids occur each mainly deriving from a distinct bacterial source cyanobacteria 2 methyl and methanotrophic bacteria 3 methyl the abundance and composition of methylhopanoids within sediments of modern depositional environments varies widely apparently due to different bacterial communities contributing to the sedimentary organic matter comparable molecular characteristics are found in oils and their source rocks consequently methylhopanoids are valuable in oil oil and oil source rock correlations distinguishing between samples related to different depositional environments in particular abundant 3 methylhopanoids from methanotrophic bacteria or an additional unknown bacterial source are characteristic of some modern alkaline saline lake environments comparable compositional features in the methylhopanes of oils allow the assignment of lacustrine oils offshore west africa to two distinct lacustrine source rock facies and to distinguish between different marine source facies thus refining oil source rock correlation

paleoenvironmental reconstruction of the coal and oil shale bearing interval in the lower cretaceous muling formation laoheishan basin northeast china abstract the laoheishan basin in northeast china has been filled with lower cretaceous coal and oil shale bearing sediments the basin fill includes from base to top alluvial conglomerate lower member of muling formation fan delta sediments interbedded with coal and oil prone mudstone denominated as oil shale layers in the upper member of muling formation and volcaniclastic rocks dongshan formation in the present study the maturity of organic matter oil shale quality and paleoenvironment of the coal and oil shale accumulation are investigated based on macro and micropetrographic data proximate and ultimate analyses bulk geochemical parameters biomarkers analysis and stable isotope geochemistry in the laoheishan basin both coal and oil shale layers are derived from land plant organic matter this contrast the oil shale of this basin from oil shale coal intercalations in fault related basins in which oil shale has been found to be of algal origin the coal is sub bituminous in rank hydrogen rich and oil prone the oil shale is of low medium grade and the relatively low oil yield may relate to the abundant resinite and sporinite because of their lower generation potential compared with alginite accumulation of the high ash coal commenced in low lying mire drowned during frequent floodings subsequently high ash low sulfur coal was deposited in a stable low lying mire under oxic conditions and limited bacterial activity afterwards the mire was drowned and formed a freshwater dysoxic to oxic shallow lake in which oil shale layers accumulated finally the depositional environment returned to low lying mire but probably with a brackish influence as indicated by elevated sulfur contents in the uppermost samples petrography and biomarker based proxies indicate that gymnosperms dominated the paleovegetation of the mire accompanied by variable amounts of herbaceous plants such as ferns

palaeoclimatic evolution during eocene and its influence on oil shale mineralisation fushun basin china the fushun basin is a small explored coal and oil shale bearing cenozoic fault basin in the liaoning province northeast china the basin mainly consists of eocene swamp to lacustrine deposits of the guchengzi to xilutian formation and contains the biggest opencast oil shale mine in asia this mine has provided an ideal opportunity to undertake palaeoclimate reconstruction in this basin based on a single geological profile and the analyses of 93 samples using various approaches namely field geological observation clay mineralogical and geochemical sr ba sr cu stable c and o isotope analyses all of which were compared with palaeobotanical data the eocene climate of fushun basin evolved from warm temperate to north subtropical and generally changed from warm humid to subhumid semiarid paleoclimatic and geochemical parameters shows that the very warm and humid climate during jijuntun formation increased the initial productivity of lake water and caused a steady stratification of the lake water then caused oxygen lack in the bottom of water productivity of the lake provides the mean origin of organic matters for oil shale formation and steady anoxic environment is beneficial for the conservation of organic matters

paleoenvironment of the eocene coal seam in the fushun basin ne china implications from petrography and organic geochemistry abstract the fushun basin in northeast china is a strike slip basin filled with coal bearing eocene sediments the basin fill includes from base to top volcaniclastic rocks a 20 to 145 m thick coal seam lower eocene guchengzi formation and lacustrine oil shale up to 300 m thick jijuntun formation the sub bituminous coal of the guchengzi formation famous for the amber inclusions is exploited in the largest opencast coal and oil shale mine in asia in the present contribution the depositional environment and the thermal history of the guchengzi formation are investigated based on macro and micropetrographic data bulk geochemical parameters biomarker analysis stable isotope geochemistry and vitrinite reflectance measurements according to our interpretation accumulation of the low sulfur coal commenced in a low lying mire near a shallow lake subsequently low ash coal was deposited either in a low lying mire protected from clastic influx or in a raised mire finally high subsidence rates typical for strike slip basins caused the flooding of the mire and terminated peat accumulation pristane phytane ratios suggest a gradual change from oxic to less oxic conditions during the drowning phase of the seam organic rich shales accumulated in the newly formed freshwater lake and resulted in the deposition of the overlying oil shale bearing jijuntun formation the coal is rich in liptinite macerals especially sporinite gymnosperms dominated the paleovegetation of the mire something that is also reflected by the frequent occurrence of resinite and amber and their biomarker composition the coal reached the sub bituminous or even the high volatile bituminous stage despite the limited burial depth simple 1d models suggest that this is a result of high heat flow rather than of deep burial and erosion the hydrogen rich coal is oil prone

variations in abundances and distributions of isoprenoid chromans and long chain alkylbenzenes in sediments of the mulhouse basin a molecular sedimentary record of palaeosalinity abstract the abundances and distribution patterns of mono di and trimethylated 2 methyl 2 4 8 12 trimethyltridecyl chromans mttcs and long chain alkylbenzenes in extracts of marl 66 samples anhydrite 15 and halite 1 strata of the salt iv formation of the oligocene mulhouse basin are reported the distributions of the methylated mttcs indicate salinity changes of the upper part of a density stratified water column of the basin these variations are explained by a tectonically or climatically induced change in the supply of water of relative lower salinity to form a layer overlying the deeper water brine hence it is suggested that mesohaline 3 5 15 conditions in the surface waters were established as a result of periodic incursions of marine water and subsequent evaporation conversely during periods when the surface water was derived mainly from fresh water from the hinterland lower average salinity in the surface layer resulted the distributions of long chain alkylbenzenes also appear to record these changes

divergent trajectories of antarctic surface melt under two twenty first century climate scenarios ice shelves modulate antarctica s contributions to sea level rise regional climate model simulations and observations suggest historical ice melt intensification before collapse of antarctic peninsula shelves and project future melt evolution

annular modes in the extratropical circulation part i month to month variability the leading modes of variability of the extratropical circulation in both hemispheres are characterized by deep zonally symmetric or annular structures with geopotential height perturbations of opposing signs in the polar cap region and in the surrounding zonal ring centered near 458 latitude the structure and dynamics of the southern hemisphere sh annular mode have been extensively documented whereas the existence of a northern hemisphere nh mode herein referred to as the arctic oscillation ao has only recently been recognized like the sh mode the ao can be defined as the leading empirical orthogonal function of the sea level pressure field or of the zonally symmetric geopotential height or zonal wind fields in this paper the structure and seasonality of the nh and sh modes are compared based on data from the national centers for environmental prediction national center for atmospheric research reanalysis and supplementary datasets the structures of the nh and sh annular modes are shown to be remarkably similar not only in the zonally averaged geopotential height and zonal wind fields but in the mean meridional circulations as well both exist year round in the troposphere but they amplify with height upward into the stratosphere during those seasons in which the strength of the zonal flow is conducive to strong planetary wave mean flow interaction midwinter in the nh and late spring in the sh during these active seasons the annular modes modulate the strength of the lagrangian mean circulation in the lower stratosphere total column ozone and tropopause height over mid and high latitudes and the strength of the trade winds of their respective hemispheres the nh mode also contains an embedded planetary wave signature with expressions in surface air temperature precipitation total column ozone and tropopause height it is argued that the horizontal temperature advection by the perturbed zonal mean zonal wind field in the lower troposphere is instrumental in forcing this pattern a companion paper documents the striking resemblance between the structure of the annular modes and observed climate trends over the past few decades

climatic change during the palaeocene to eocene based on fossil plants from fushun china abstract by applying the coexistence approach ca to palynological data from the laohutai lizigou guchengzi jijuntun and xilutian formations in fushun northeastern china a quantitative reconstruction of the palaeocene to eocene climate is made during that time mean annual temperature changed from 11 3 to 21 c mean annual precipitation from 654 to 1540 mm mean temperature of the warmest month from 19 4 to 28 2 c mean temperature of the coldest month from 3 6 to 13 9 c mean annual range of temperature from 12 8 to 23 5 c mean maximum monthly precipitation from 175 to 354 mm and mean minimum monthly precipitation from 8 to 27 mm all the parameters in the five formations indicate a subtropical climate this situation is different from the current climate at the same site a mid temperate and continental monsoon climate with a mean annual temperature of 6 6 c and a mean annual precipitation of 804 mm in addition the climatic parameters obtained from megafossil data only found in the jijuntun formation were analyzed and approximate those from the palynological data the parameters from the palynological data support the view that the palaeogene climate of northeast asia and north america was similar but unlike that of europe

new insights into the origin of perylene in geological samples abstract the origin of the polycyclic aromatic hydrocarbon pah perylene in sediments and petroleum has been a matter of continued debate reported to occur in phanerozoic organic matter om fossil crinoids and tropical termite mounds its mechanism of formation remains unclear while a combustion source can be excluded structural similarities to perylene quinone like components present in e g fungi plants crinoids and insects potentially suggest a product precursor relationship here we report perylene concentrations 13c 12c and d h ratios from a holocene sediment profile from the qingpu trench yangtze delta region china perylene concentrations differ from those of pyrogenic pahs and rise to prominence in a stratigraphic interval that was dominated by woody vegetation as determined by palynology including fungal spores in this zone perylene concentrations exhibit an inverse relationship to the lignin marker guaiacol d h ratios between 284 and 317 similar to the methoxy groups in lignin as well as co variation with spores from wood degrading fungi 13c 12c of perylene differs from that of land plant wax alkanes and falls in the fractionation range expected for saprophytic fungi that utilise lignin which is isotopically lighter than cellulose and whole wood during progressive lignin degradation the relative carbon isotopic ratio of the perylene decreases we therefore hypothesise a relationship of perylene to the activity of wood degrading fungi to support our hypothesis we analysed a wide range of phanerozoic sediments and oils and found perylene to generally be present in subordinate amounts before the evolutionary rise of vascular plants and to be generally absent from marine sourced oils few exceptions being attributed perhaps to a contribution of marine and or terrestrial derived fungi anoxia especially under marine conditions and or contamination of core material by fungi a series of low molecular weight aromatic quinones bearing the perylene backbone were detected in devonian and cretaceous sediments potentially representing precursor components to perylene

petrology and hydrocarbon potential of microalgal and macroalgal dominated oil shales from the eocene huadian formation ne china abstract a series of oil shales of middle to late eocene age occur in the huadian area of jinlin province northeast china analytical results from 22 rock samples collected from an underground mine in the guanglangtou district in the huadian basin show that the total organic carbon toc contents of the oil shale layers are very high 10 6 wt to 39 6 wt with vitrinite reflectance ro values of 0 41 0 02 and rock eval hydrogen index hi values up to 887 biomarker analyses show a high proportion of hopenes and hopanes with stereochemistry indicative of low maturity detailed organic petrologic analysis demonstrates that the organic matter is dominated by lamalginite and telalginite the presence of botryococcus in the telalginite indicates that the depositional environment of the oil shale is lacustrine this is consistent with low si and s contents and high c s ratios fragments from a newly identified benthic macroalgal rhodophyte were found in some thin layers raising the possibility that the depositional environment of some oil shale layers may have been influenced by marine flooding since rhodophyta are uncommon in freshwater systems two oil shale samples with different algal compositions were selected for assessment of hydrocarbon generation potential sample hd 21 is dominated by phytoplanktic lamalginite with a high hi value of 869 mg hc g toc while sample hd 20 has a lower hi value 490 mg hc g toc and contains high contents of the benthic rhodophyte as well as some phytoplanktic lamalginite hi values and thermal simulation experiments showed that the phytoplankton dominated shale hd 21 has a much higher hydrocarbon generation potential than the rhodophyte dominated oil shale hd 20 even though the toc content of hd 20 was much higher indicating that the benthic macroalgal macerals have a much lower capacity to generate oil when thermally mature

the relationship between the southern hemisphere annular mode and antarctic peninsula summer temperatures analysis of a high resolution model climatology abstract the large regional summer warming on the east coast of the northern antarctic peninsula ap which has taken place since the mid 1960s has previously been proposed to be caused by a trend in the southern hemisphere annular mode sam the authors utilize a high resolution regional atmospheric model climatology 14 km grid spacing to study the mechanisms that determine the response of the near surface temperature to an increase in the sam t sam month to month variations in near surface temperature and surface pressure are well represented by the model it is found that north of 68 s t sam is much larger on the eastern lee side than on the western windward side of the barrier this is because of the enhanced westerly flow of relatively warm air over the barrier which warms and dries further as it descends down the lee slope the downward motion on the eastern side of the barrier causes a decrease in surface mass balance and cloud cover south of 68 s vertical deflection across

organic matter accumulation in the oil shale and coal bearing huadian basin eocene ne china abstract the huadian basin located in northeastern china is a fault controlled basin filled by eocene non marine sediments assigned to the huadian formation the formation is subdivided from bottom to top into three members pyrite member oil shale member and carbonaceous shale member using bulk geochemical data from borehole hd3 and core descriptions from a high number of wells the factors controlling organic matter accumulation have been evaluated the organic matter content of the pyrite member is relatively low average toc 0 9 wt mudstones deposited in shallow lacustrine environments contain between 1 and 2 wt toc max 6 wt and a kerogen type ii hi 400 600 mg hc g toc an arid climate prevented the accumulation of thick coal the overlying oil shale member contains 13 oil shale layers which are mined underground the oil shale member has been interpreted as a 3rd order sequence significant differences exist between oil shales deposited in different systems tracts 2 m thick coaly oil shale of low quality oil yield 3 5 wt developed in the lowstand systems tract oil shale up to 7 m thick of moderate quality oil yield 4 1 8 0 wt was deposited during the transgressive systems tract tst thinner the carbonaceous shale member representing the balanced fill to overfilled stage of basin evolution hosts economic coal seams which are occasionally accompanied by shallow lacustrine shales with abundant hydrogen rich organic matter otherwise non coal layers are typically low in organic matter average toc 0 9 wt in contrast to the huadian basin a very thick coal seam overlain by a single oil shale layer more than 100 m thick developed in the eocene fushun basin this indicates major differences in the evolution of basins with similar tectonic setting and age

strong surface melting preceded collapse of antarctic peninsula ice shelf 1 during the austral summer of 2001 02 melting at the surface of larsen ice shelf in the antarctic peninsula was three times greater than the average of five previous summers this exceptional melt event lasted for three months and was followed by the collapse of larsen b ice shelf during which 3 200 km2 of ice shelf surface was lost the strong melting was caused by a persistent atmospheric circulation anomaly which depleted sea ice concentrations in front of larsen ice shelf and transported warm air to the ice shelf throughout the 2001 02 summer this supports the theory that large meltwater fluxes accelerate the retreat of antarctic peninsula ice shelves

interpretation of recent antarctic sea ice variability 1 trends in the satellite derived antarctic sea ice concentrations 1979 2002 show pronounced increase decrease in the central pacific sector bellingshausen western weddell sector by 4 10 per decade confidence levels for these regional trends exceed 95 positive polarities of the antarctic oscillation aao lead to more less ice in the eastern ross amundsen sector bellingshausen northern weddell sector which are qualitatively opposite to the impacts of positive polarities of the el nino southern oscillation enso the mechanisms responsible for the covariability between the ice and the a aao and b enso are demonstrated over the last 24 years a positive aao trend and a slightly negative enso trend produce a spatial pattern of ice changes similar to the regional ice trends however the magnitude of the ice changes associated with the aao and enso is much smaller than the regional ice trends more local or less understood large scale processes should be investigated for the explanations

glacier acceleration and thinning after ice shelf collapse in the larsen b embayment antarctica 1 ice velocities derived from five landsat 7 images acquired between january 2000 and february 2003 show a two to six fold increase in centerline speed of four glaciers flowing into the now collapsed section of the larsen b ice shelf satellite laser altimetry from icesat indicates the surface of hektoria glacier lowered by up to 38 6 m in a six month period beginning one year after the break up in march 2002 smaller elevation losses are observed for crane and jorum glaciers over a later 5 month period two glaciers south of the collapse area flask and leppard show little change in speed or elevation seasonal variations in speed preceding the large post collapse velocity increases suggest that both summer melt percolation and changes in the stress field due to shelf removal play a major role in glacier dynamics

evolution of lacustrine systems along the miocene mur murz fault system eastern alps austria and implications on source rocks in pull apart basins tectonically controlled lakes developed during miocene lateral extrusion of the eastern alps mineralogy and the inorganic and organic geochemistry of rocks from three boreholes were investigated to reconstruct the evolution of lake ingering and lake groisenbach and to study the distribution of source rocks in pull apart basins gas prone coal and oil prone sapropelic shale accumulated during the initial shallow stages of lake ingering thereafter the lake deepened rapidly 125 m thick prodelta shale containing a type ii kerogen was deposited in the brackish several hundred meter deep hydrologically closed lake afterwards decreasing subsidence allowed the filling of the lake by prograding deltas during the advance of the deltaic systems the lake became shallower hydrologically open and the brackish influence terminated source rock quality decreased significantly during the filling stage of the lake a consequence of dilution of autochthonous organic matter and of enhanced input of land plants despite its considerable dimensions formation and filling of lake ingering lasted only two million years lake groisenbach was considerably smaller and more susceptible to high frequency changes in lake chemistry although the water body was temporarily oligosaline brackish conditions did not occur high sulphur contents were due to anoxic events and the inflow of ca rich waters abundant dissolved silica favoured diatoms blooms

changes in antarctic temperature wind and precipitation in response to the antarctic oscillation output of a 14 year integration with a high resolution 55 km 55 km regional atmospheric climate model is used to study the response of antarctic near surface climate to the antarctic oscillation aao the periodical strengthening and weakening of the circumpolar vortex in the southern hemisphere in spite of the relatively short record wind temperature and precipitation show widespread and significant aao related signals when the vortex is strong high aao index northwesterly flow anomalies cause warming over the antarctic peninsula ap and adjacent regions in west antarctica and the weddell sea in contrast cooling occurs in east antarctica the eastern ross ice shelf and parts of marie byrd land most of the annual temperature signal stems from the months march august the spatial distribution of the precipitation response to changes in the aao does not mirror temperature changes but is in first order determined by the direction of flow anomalies with respect to the antarctic topography when the vortex is strong high aao index the western ap becomes wetter while the ross ice shelf parts of west antarctica and the lambert glacier basin east antarctica become drier

latest permian to middle triassic cyclo magnetostratigraphy from the central european basin germany implications for the geomagnetic polarity timescale in central germany the about 1 km thick mainly clastic germanic lower triassic buntsandstein consists of about 60 sedimentary cycles which are considered to reflect variability in precipitation within the epicontinental central european basin most probably due to solar induced short eccentricity cycles they provide a high resolution cyclostratigraphic framework that constitutes the base for creating a composite geomagnetic polarity record in which this paper presents a middle buntsandstein to lowermost muschelkalk magnetostratigraphy obtained from 6 outcrops and 2 wells where a total of 471 samples was collected combined with recently established records a well documented magnetostratigraphy for the upper zechstein to lowermost muschelkalk latest permian to middle triassic of central germany has been constructed encompassing an overall stratigraphic thickness of about 1 3 km and 22 magnetozones derived from about 2050 paleomagnetic samples along with available biostratigraphy this multi disciplinary study facilitates detailed links to the marine realm in order to directly refer biostratigraphically calibrated triassic stage boundaries as well as radioisotopic ages to the buntsandstein cyclostratigraphy and conversely to contribute to calibrating the geologic timescale 2007 elsevier b v all rights reserved

deposition of coal and oil shale in ne china the eocene huadian basin compared to the coeval fushun basin abstract the huadian and fushun basins located along the dunmi fault zone ne china are filled with non marine coal and oil shale bearing sediments of eocene age despite similar tectonic setting the habitat of coal and oil shale differs significantly during this study the depositional environment of organic rich sediments in the huadian basin and factors controlling differences between both basins were investigated early in the history of the huadian basin thin coaly and bituminous mudstones accumulated in shallow lake environments pyrite member water depth increased during deposition of the oil shale member but did not exceed a few tens of meters preventing stable water column stratification moreover deposition of fan delta sediments interrupted accumulation of fine grained rocks nevertheless algal blooms and oxygen depleted conditions resulted in accumulation of 13 thin high subsidence rates in the fushun basin favored deposition of thick coal during the transgressive stage and of oil shale in a deep lake in contrast minor subsidence in the huadian basin resulted in a lake with moderate water depth and deposition of several oil shale layers with varying quality in this basin economic coal developed only during the regressive stage

identification of aryl isoprenoids in source rocks and crude oils biological markers for the green sulphur bacteria abstract a series of c13 to c31 aryl isoprenoids 1 alkyl 2 3 6 trimethylbenzenes have been identified in reef hosted oils and their source rocks from the middle and upper silurian of the michigan basin and middle devonian of the alberta basin canada their structure has been confirmed by unambiguous synthesis of the c14 member of the series their structure and isotopic composition indicate that they are derived from isorenieratene from the chlorobiaceae family of sulphur bacteria these results are consistent with geological and geochemical studies that show that the source rocks were deposited under metahaline to hypersaline sulphate and sulphide rich water columns the distribution of other biomarkers in these oils and source rocks indicates that a diverse biota contributed organic matter to the source environment in conjunction with the aryl isoprenoids they show that there is a remarkable similarity in composition between the two sets of oils and source rocks despite their great temporal and geographic separation this reflects the similarity of their environments and emphasizes the importance of sedimentary facies in controlling the composition of organic matter in source rocks and their derived oils

foehn jets over the larsen c ice shelf antarctica previously unknown foehn jets have been identified to the east of the antarctic peninsula ap above the larsen c ice shelf these jets have major implications for the east coast of the ap a region of rapid climatic warming and where two large sections of ice shelf have collapsed in recent years during three foehn events across the ap leeside warming and drying is seen in new aircraft observations and simulated well by the met office unified model metum at 1 5 km grid spacing in case a weak southwesterly flow and an elevated upwind inversion characterise a highly nonlinear flow regime with upwind flow blocking in case c strong northwesterly winds characterise a relatively linear case with little upwind flow blocking case b resides somewhere between the two in flow regime linearity the foehn jets apparent in aircraft observations where available and metum simulations of all three cases are mesoscale features up to 60 km in width originating from the mouths of leeside inlets through back trajectory analysis they are identified as a type of gap flow in cases a and b the jets are distinct being strongly accelerated relative to the background flow and confined to low levels above the larsen c ice shelf they resemble the shallow foehn of the alps case c resembles a case of deep foehn with the jets less distinct the foehn jets are considerably cooler and moister relative to adjacent regions of calmer foehn air this is due to a dampened foehn effect in the jet regions in case a the jets have lower upwind source regions and in the more linear case c there is less diabatic warming and precipitation along jet trajectories due to the reduced orographic uplift across the mountain passes

the impact of a changing southern hemisphere annular mode on antarctic peninsula summer temperatures since the mid 1960s rapid regional summer warming has occurred on the east coast of the northern antarctic peninsula with near surface temperatures increasing by more than 2 degrees c this warming has contributed significantly to the collapse of the northern sections of the larsen ice shelf coincident with this warming the summer southern hemisphere annular mode sam has exhibited a marked trend suggested by modeling studies to be predominantly a response to anthropogenic forcing resulting in increased westerlies across the northern peninsula observations and reanalysis data are utilized to demonstrate that the changing sam has played a key role in driving this local summer warming it is proposed that the stronger summer westerly winds reduce the blocking effect of the antarctic peninsula and lead to a higher frequency of air masses being advected eastward over the orographic barrier of the northern antarctic peninsula when this occurs a combination of a climatological temperature gradient across the barrier and the formation of a fohn wind on the lee side typically results in a summer near surface temperature sensitivity to the sam that is 3 times greater on the eastern side of the peninsula than on the west sam variability is also shown to play a less important role in determining summer temperatures at stations west of the barrier in the northern peninsula similar to 62 degrees s both at the surface and throughout the troposphere this is in contrast to a station farther south similar to 65 degrees s where the sam exerts little influence

rapid collapse of northern larsen ice shelf antarctica in january 1995 4200 square kilometers of the northern larsen ice shelf antarctic peninsula broke away radar images from the ers 1 satellite complemented by field observations showed that the two northernmost sections of the ice shelf fractured and disintegrated almost completely within a few days this breakup followed a period of steady retreat that coincided with a regional trend of atmospheric warming the observations imply that after an ice shelf retreats beyond a critical limit it may collapse rapidly as a result of perturbated mass balance

biomarker and n alkane isotope profiles for tertiary oils relationship to source rock depositional setting abstract biomarker and n alkane isotope profiles have been measured for 29 late cretaceous tertiary oils from se asia china papua new guinea new zealand and the u s a the results are interpreted with respect to six kinds of source rock depositional setting fluvio deltaic fd freshwater transitional tr lacustrine lac saline lacustrine sal marine deltaic md and marine carbonate mc a comparison of biomarker and n alkane isotope results suggests that parameters such as the oleanane hopane ratio may overestimate the higher plant contribution to marine oils the abundance of bicadinanes is much more variable than that of oleanane probably because of a specific association with the highly resinous dipterocarp hardwoods of se asia however traces do occur in an oil from outside the paleogeographic range of the dipterocarp family confirming that there is also a more general angiosperm source the bicadinane isomeric distribution is shown to depend on maturity leading to new maturity parameters which are resistant to even very heavy biodegradation retention indices based on the regular hopane series are provided for the main bicadinane and methyl bicadinane isomers and for a group of oleanane related triterpanes of unknown structure the presence of the latter compounds may indicate locally deposited as opposed to transported higher plant matter in the source source rock depositional setting is the primary control on the shape of the n alkane isotope profile with negatively sloping curves being characteristic of fd and tr oils and flat or positively sloping curves typical of marine oils the difference is probably related to the bacterial reworking of higher plant matter in the fd environment a slight isotopic anomaly at n c 17 correlates with the abundance of algal derived steranes and may indicate a minor marine contribution to the source of an fd oil

paleoweathering and paleoenvironmental change recorded in lacustrine sediments of the early to middle eocene in fushun basin northeast china deciphering the long term interaction among continental silicate weathering global climate and atmospheric co2 concentrations is helpful in understanding the mechanisms of the cenozoic climate change and accessing the future climatic and environmental response to anthropogenic carbon emissions the eocene which is characterized by the early eocene climatic optimum eeco and the following global cooling represents an ideal test case here we generate geochemical data of the eocene lacustrine sediments from the fushun basin northeast china to explore the regional climatic response to the global climate change the chemical index of alteration cia and plagioclase index of alteration pia consistently show a gradual long term decrease indicating a climatic transition from warm and humid to relatively cold and arid during the eocene in the fushun basin this climatic trend is broadly coincident with the global cooling and decreasing co2 concentration implying that the regional climate is closely correlated with the global climate change over geological time scales additionally the extreme silicate weathering and high lake productivity as reflected by relatively positive 13c values of lacustrine organic matter are associated with the eeco this consistency may demonstrate that enhanced continental weathering and lake productivity had served as effective sinks to lower atmospheric co2 across the eeco collectively our new geochemical data add supporting evidence for a long term close coupling among continental silicate weathering climate and global carbon cycle during the eocene

perylene as an indicator of conifer fossil wood degradation by wood degrading fungi the occurrence of perylene in middle jurassic fossil wood and miocene xylites from poland is described along with its correlation with unsubstituted polycyclic aromatic hydrocarbons pahs as well as cellulose content both middle jurassic and miocene wood remnants were of relatively low maturity ca 0 2 0 3 vitrinite reflectance rr had excellent preservation of biomarkers and biomolecules and in the case of the middle jurassic fossil wood samples generally good preservation of anatomical structures due to early diagenetic mineralisation the results from 42 middle jurassic and 8 miocene most taxonomically defined fossil wood fragments demonstrated a negative correlation between the concentration of perylene and those of generally typical conifer biomarkers e g cadalene dehydroabietane simonellite and retene in addition good correlation r2 0 81 was observed between the ratio of perylene to the above conifer biomarkers and the ratio of pahs phenanthrene and fluoranthene and pyrene to the conifer biomarkers this implies that the high concentration of perylene in fossil wood indicate its extensive degradation during decay transport and early diagenesis we defined a conifer wood degradation index as cwdi perylene perylene cadalene retene simonellite dehydroabietane cwdi perylene perylene cadalene retene simonellite dehydroabietane and observed a wide range of values 0 001 for less degraded wood to 0 95 for highly degraded samples anatomical wood preservation was associated with cwdi values in most of the samples characterised by poorly preserved anatomy high cwdi values were observed while anatomically well preserved samples generally had lower cwdi values we determined similar 13c values for perylene from the fossil wood samples 26 4 to 27 8 whereas the values for the conifer biomarkers were slightly higher and varied from 25 6 to 26 6 in contrast pyrene was depleted in 13c 27 5 to 28 2 the carbon isotope values of perylene are consistent with an origin from wood degrading fungi

interpretation of recent southern hemisphere climate change climate variability in the high latitude southern hemisphere sh is dominated by the sh annular mode a large scale pattern of variability characterized by fluctuations in the strength of the circumpolar vortex we present evidence that recent trends in the sh tropospheric circulation can be interpreted as a bias toward the high index polarity of this pattern with stronger westerly flow encircling the polar cap it is argued that the largest and most significant tropospheric trends can be traced to recent trends in the lower stratospheric polar vortex which are due largely to photochemical ozone losses during the summer fall season the trend toward stronger circumpolar flow has contributed substantially to the observed warming over the antarctic peninsula and patagonia and to the cooling over eastern antarctica and the antarctic plateau

precipitation sublimation and snow drift in the antarctic peninsula region from a regional atmospheric model 1 a regional atmospheric model with a horizontal grid spacing x of 14 km is used to study the surface mass balance components precipitation sublimation and snow drift in the region of the antarctic peninsula ap an integration is performed for the 7 year period 1987 1993 using a realistic forcing at the lateral model boundaries and at the sea surface output from this integration indicates that the precipitation reaches its maximum value on the northwestern slope of the ap where the upward motion in the atmosphere is largest uplift occurs upstream of the barrier affecting the precipitation distribution over sea the effect of the barrier on the precipitation distribution over the bellingshausen sea might have important implications for the ocean circulation in this region the mean precipitation over the grounded ice of the ap 1 20 m water eq yr 1 is 6 times larger than the mean value over all the grounded ice of antarctica our estimates for the surface sublimation and wind transport of snow over the grounding line toward the sea are 9 and 6 1 of the precipitation respectively in situ data of the wind distribution at three coastal sites located on the northern eastern and western sides of the ap are used to evaluate the modeled wind field which is important for the snow drift calculations for two of the three sites considered the prevailing wind direction and bimodal wind distribution are correctly represented by the model the calculated distribution of accumulation and ablation due to snow drift shows a complex pattern the wind removes snow from the spine of the ap where the near surface flow field diverges whereas deposition occurs mainly on the eastern slopes where the near surface flow field converges an intercomparison between two 7 year integrations at different horizontal resolution x 14 km and x 55 km shows that the precipitation on the northwestern slope is very sensitive to the model resolution in the x 14 km integration precipitation on the northwestern slope is higher than in x 55 km because of higher vertical velocities resulting in a 35 increase in average precipitation over the grounded ice of the ap

characteristics of summer airflow over the antarctic peninsula in response to recent strengthening of westerly circumpolar winds abstract summer near surface temperatures over the northeast coast of the antarctic peninsula have increased by more than 2 c over the past 40 years a temperature increase 3 times greater than that on the northwest coast recent analysis has shown a strong correlation between this striking warming trend and significant change in the summer southern hemisphere annular mode sam which has resulted in greatly increased summer westerlies across the northern peninsula it has been proposed that the strengthening westerlies have resulted in increased vertical deflection of relatively warm maritime air over the northern peninsula contributing significantly to the observed warming and the recent collapse of northern sections of the larsen ice shelf in this study laboratory and numerical modeling of airflow incident to the peninsula are employed to further understand this mechanism it is shown that the effect of the strengthening westerlies has led to a distinct transition from a blocked regime to a flow

diverse sedimentary conditions during deposition of coal and oil shale from the meihe basin eocene ne china the meihe basin in northeastern china is a normal fault controlled basin filled with eocene nonmarine deposits the sediments assigned to the meihe formation sediment grain sizes core study well log analysis and micropetrographic study combined with sedimentary facies analysis indicate that the main sedimentary facies of the meihe basin represent fan delta lake and turbidite deposits thick coal seams that are mainly distributed in the eastern part of the studied area were deposited in the swamp facies of the lower coal bearing member oil shale was mainly deposited in the deep lake represented by the mudstone member and is mainly distributed in the southern part of the studied area in the lower coal bearing member organic rich sediments are characterized by toc content between 0 6 wt and 43 1 wt and contain type ii and iii kerogen the thick coal seams are the result of high landplant productivity and good preservation conditions thin coal seams in the fan delta plain resulted from the migration and erosion of the fan delta channel in the shallow lake and fan delta front limited productivity coupled with dilution by inorganic matter resulted in lower organic matter content in themudstonemember oil shale and mudstone rich in organic matter were deposited in a deep lake with an average toc content of 3 4 wt the origin of the organic matter was mainly algae and aquatic plants mixed with land plants the improved preservation conditions and high bioproductivity in this environment resulted in three oil shale layers in the lower part of this sedimentary succession three coal bearing and oil shale bearing fault basins lie adjacent to the dunhua mishan fault zone among which the fushun basin is located in the southwest the meihe basin is in themiddle and thehuadian basin is in the southeast from the fushun basin to the huadian basin the oil shale and coal seams have distinct sedimentation characters laterally vertically in each basin the organic matter sources all have the same variation trend from land plants to land plants mixed with algae to algae then to algae mixed with land plants and the toc content also shows a similar trend from high to medium high then to low in each basin

depositional environment of oil shale within the eocene jijuntun formation in the fushun basin ne china abstract the non marine fushun basin in ne china is a fault controlled basin filled with eocene sediments it hosts the largest opencast coal and oil shale mine in asia a single thick oil shale layer overlying sub bituminous coal occurs within the middle eocene jijuntun formation based on mineralogy inorganic and organic geochemistry organic petrography stable isotope geochemistry and vitrinite reflectance measurements the depositional environment and the oil shale potential of the oil shale bearing succession were investigated the jijuntun formation is subdivided into a lower and an upper unit characterized by a low and high quality oil shale respectively the thick oil shale layer of the jijuntun formation developed under long lasting stable conditions in a deep freshwater lake after drowning of a swamp the organic matter in the lower unit is characterized by landplant derived macerals the sediments containing a type ii kerogen hi 400 mghc gtoc were deposited during warm and humid conditions lacustrine organisms predominant in the upper unit are forming kerogen type i hi 700 mghc gtoc high bioproductivity and excellent preservation conditions resulted in high toc contents up to 23 6 wt in the upper unit the organic matter preservation was controlled by photic zone anoxia originating in a temperature stratified water column in the deep lake without significant changes in bottom water salinity mid eocene cooling during deposition of the upper unit of the jijuntun formation is reflected by clay mineral composition a hot and arid climate favoring brackish conditions in a shallow lake prevailed during accumulation of the overlying carbonate rich xilutian formation individual geochemical parameters in the fushun basin have to be used with caution e g the maturity proxy tmax is affected by kerogen type the redox proxy pr ph ratio is probably biased by different sources of isoprenoids this demonstrates the importance of multi proxy studies

a low level explanation for the recent large warming trend over the western antarctic peninsula involving blocked winds and changes in zonal circulation 1 we demonstrate a mechanism whereby the impact of stronger circumpolar westerly winds on the mountains of the antarctic peninsula contributes significantly to the enhanced warming trend observed over its western side in the last 50 years numerical and laboratory meteorological modelling demonstrate how when westerly winds impinge on this side warm air below the height 1 5 2 0 km of the peninsula is advected in a southerly direction the strength of the annual mean westerly winds has increased by about 15 20 since the 1960s while the modelling results indicate that contemporaneously the air advected to its western side originates from an increasingly northerly and warmer location this gives rise to increased northerlies and a greater transport of warm air into this region consequently there is a reduction in the sea ice extent further amplifying the local warming this low level orographic mechanism for the local climate trend is supported by observational evidence

recent atmospheric warming and retreat of ice shelves on the antarctic peninsula in 1978 mercer1 discussed the probable effects of climate warming on the antarctic ice sheet predicting that one sign of a warming trend in this region would be the retreat of ice shelves on the antarctic peninsula analyses of 50 year meteorological records have since revealed atmospheric warming on the antarctic peninsula2 3 and a number of ice shelves have retreated4 8 here we present time series of observations of the areal extent of nine ice shelves on the antarctic peninsula showing that five northerly ones have retreated dramatically in the past fifty years while those further south show no clear trend comparison with airtemperature data shows that the pattern and magnitude of ice shelf retreat is consistent with the existence of an abrupt thermal limit on iceshelf viability the isotherm associated with this limit having been driven south by the atmospheric warming ice shelves therefore appear to be sensitive indicators of climate change

foehn warming distributions in nonlinear and linear flow regimes a focus on the antarctic peninsula the structure of lee side warming during foehn events is investigated as a function of cross barrier flow regime linearity two contrasting cases of westerly flow over the antarctic peninsula ap are considered one highly nonlinear the other relatively linear westerly flow impinging on the ap provides one of the best natural laboratories in the world for the study of foehn owing to its maritime setting and the larsen c ice shelf lcis providing an expansive homogeneous and smooth surface on its east side numerical simulations with the met office unified model at 1 5 km grid size and aircraft observations are utilized in case a relatively weak southwesterly cross peninsula flow and an elevated upwind inversion dictate a highly nonlinear foehn event with mountain wave breaking observed the consequent strongly accelerated downslope flow leads to high amplitude warming and ice shelf melt in the immediate lee of the ap however this foehn warming diminishes rapidly downwind due to upward ascent of the foehn flow via a hydraulic jump in case c strong northwesterly winds dictate a relatively linear flow regime there is no hydraulic jump and strong foehn winds are able to flow at low levels across the entire ice shelf mechanically mixing the near surface flow preventing the development of a strong surface inversion and delivering large fluxes of sensible heat to the ice shelf consequently in case c ice melt rates are considerably greater over the lcis as a whole than in case a our results imply that although nonlinear foehn events cause intense warming in the immediate lee of mountains linear foehn events will commonly cause more extensive lee side warming and over an ice surface higher melt rates this has major implications for the ap where recent east coast warming has led to the collapse of two ice shelves immediately north of the lcis

a new look for the southern hemisphere jet stream a new jet stream description defined as the geostrophic streamline of maximum average velocity is proposed an objective algorithm for detecting and tracking the jet has been developed tested and applied to the ncep ncar 200 hpa geopotential height in the southern hemisphere for the period 1958 2002 the results show the variability of the double character of the southern hemisphere jet with a marked seasonality during the warm season a single jet can be found around 40 s while autumn and winter are characterized by a clear double jet structure with a strong and dominant subtropical jet located around 30 s and a polar front jet progressively displaced toward southern latitudes and reaching 60 s by the end of the cold season in general a trend toward slower subtropical jets and stronger polar front jets has been detected during the study period the southern annular mode appears as a main modulator of the latitude and strength of the polar front jet influencing to a minor extent its subtropical counterpart the enso cycle strongly modifies the latitude and specially the strength of the subtropical jet affecting its preferred wavenumber as well nevertheless the effect of this oscillation seems fairly restricted in the pacific thus limiting the ability of this jet to drive the el nino teleconnections along the southern hemisphere the consistency of the results when compared with previous jet climatologies suggests that the new approach is a reliable jet tracking method thus providing a new tool to analyze climatic variability at hemispheric scales

influence of the southern annular mode on the sea ice ocean system 1 the global sea ice ocean model orca2 lim driven by the ncep ncar national centers for environmental prediction national center for atmospheric research reanalysis daily 2 m air temperatures and 10 m winds and by monthly climatologies for precipitation cloud cover and relative humidity is used to investigate the impact of the southern annular mode sam on the antarctic sea ice ocean system our results suggest that the response of the circumpolar southern ocean consists of an annular and a nonannular component for the sea ice cover the non annular component seems to be the most important the annular component strongly affects the overall patterns of the upper ocean circulation when the sam is in its positive phase a northward surface ekman drift a downwelling at about 45 degreess and an upwelling in the vicinity of the antarctic continent are simulated the non annular component has a significant impact at the regional scale especially in the weddell ross amundsen and bellingshausen seas in those regions the pressure pattern associated with the sam induces meridional winds which advect warmer air in the weddell sea and around the antarctic peninsula and colder air in the amundsen and ross seas this implies a dipole response of sea ice to the sam with on average a decrease in ice area in the weddell sea and around the antarctic peninsula and an increase in the ross and amundsen seas during years with a high sam index the long term trend in the observed sea ice area does not appear to be related to the trend in the sam index

interpreting rock eval pyrolysis data using graphs of pyrolizable hydrocarbons vs total organic carbon kerogen the major organic component of sedimentary rocks is commonly analyzed by rock eval pyrolysis plotting the data on a graph of s 2 vs total organic carbon toc and determining the regression equation is the best method for determining the true average hydrogen index and measuring the adsorption of hydrocarbon by the rock matrix such a plot also indicates the type of kerogen present and avoids the problem of increasing hydrogen index with total organic carbon content with the s 2 vs toc diagram the organic component of different suites of samples may be compared and their petroleum generation potentials established as an example the diagrams are used to evaluate the sedimentary environments and petroleum potential of the paleogene evaporitic sediments of the mulhouse basin alsace france

depositional environment of the lower cretaceous muling formation of the laoheishan basin ne china implications from geochemical and petrological analyses abstract the laoheishan basin located in northeastern china is filled with non marine coal and oil shale oil prone mudstone sediments of the lower cretaceous muling formation based on petrological mineralogical and geochemical methods the depositional environment during organic matter om accumulation is investigated for the first time the coal is subbituminous in rank petrological and bulk geochemical data indicate sapropelic coal deposited in low lying mire under freshwater conditions high pristane phytane ratios provide evidence for a land plant origin of om and oxic conditions during deposition a neutral to slightly alkaline ph is reflected by the presence of carbonate high liptinite contents and terpenoid biomarker composition indicate high amounts of resinous om during oil shale deposition a raised water table was favorable for om preservation under oxic to dysoxic conditions the oil shales in the lower unit of the succession not associated with coal are characterized by high hydrogen index and resinite contents interpreted to reflect deposition at elevated water depths in contrast to the findings of previous studies on oil shales in china indicating its origin from algal om a predominance of terrigenous om rich in waxy and resinous lipids is implied from biomarker and maceral composition the lower cretaceous oil shale and coal in the laoheishan basin contain high amounts of land plant derived terpenoid biomarkers derived from coniferales e g pinaceae cupressaceae taxodiaceae araucariaceae podocarpaceae and ferns the results are in agreement with palynological data the data highlight the potential of resinous and waxy om to form excellent hydrocarbon source rocks

sensitivity of resolved mountain drag to model resolution for map case studies seven mountain wave case studies from the mesoscale alpine programme map have been used to investigate the behaviour of the resolved alpine pressure drag with model horizontal resolution three independent modelling systems show that the magnitude of the resolved surface pressure drag increases monotonically as the horizontal model resolution is increased from 125 km down to a few kilometres a substantial proportion of the drag will still need to be parametrized in the next generation of mesoscale models with horizontal resolutions of 3 or 4 km this is particularly true for the most important drag cases when the jet stream directly above the mountains produces larger wind speeds near mountain crest level resulting in much larger total alpine drags copyright 2006 royal meteorological society

sesqui and diterpenoid biomarkers preserved in taxodium rich oligocene oxbow lake clays weisselster basin germany several diterpenoids of the abietane pimarane and phyllocladane type and three cadalanetype sesquiterpenoids have been identified in the organic solvent extracts of lower oligocene clay sediments haselbach strata saxony germany the sediment contains needles and cone scales of a fossil taxodium species which represents the only conifer in the samples a clear correlation between the observed conifer biomarkers and taxodium is evident apart from diterpenoids detected previously in other sediments a new diaromatic totarane diterpenoid is reported in isolated fossil and recent taxodium needles and cone scales as well as in the haselbach clays a phenolic diterpenoid of the abietane type ferruginol has been identified the results indicate that the taxodium rich clay samples contain several diterpenoids which so far have been used as biomarkers for other conifer families and thus the chemotaxonomical use of diterpenoid biomarkers for the differentiation of fossil conifer families has to be revised

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

observed antarctic interannual climate variability and tropical linkages abstractthis study reviews the mechanisms associated with antarctic tropical climate linkages and presents new analyses of the seasonality and spatial patterns of tropical climate signals in the antarctic for the late 1950s to the present tropical climate signals are primarily communicated to the antarctic via the pacific south america psa pattern and the southern annular mode sam the impacts of these circulation patterns and their tropical linkages are evident in regressions of seasonally stratified antarctic station temperature data and annually resolved ice core records on global fields of sea surface temperature sea level pressure and precipitation temperature and ice core anomalies in the antarctic peninsula region and adjoining areas of west antarctica are significantly impacted by the psa interpreted as a rossby wave train driven by anomalous tropical deep convection during enso events this pattern is most evident in the austral spring consistent with recent studies suggesting that atm

spectral nudging to eliminate the effects of domain position and geometry in regional climate model simulations 1 it is well known that regional climate simulations are sensitive to the size and position of the domain chosen for calculations here we study the physical mechanisms of this sensitivity we conducted simulations with the regional atmospheric modeling system rams for june 2000 over north america at 50 km horizontal resolution using a 7500 km 5400 km grid and ncep ncar reanalysis as boundary conditions the position of the domain was displaced in several directions always maintaining the u s in the interior out of the buffer zone along the lateral boundaries circulation biases developed a large scale structure organized by the rocky mountains resulting from a systematic shifting of the synoptic wave trains that crossed the domain the distortion of the large scale circulation was produced by interaction of the modeled flow with the lateral boundaries of the nested domain and varied when the position of the grid was altered this changed the large scale environment among the different simulations and translated into diverse conditions for the development of the mesoscale processes that produce most of precipitation for the great plains in the summer season as a consequence precipitation results varied sometimes greatly among the experiments with the different grid positions to eliminate the dependence of results on the position of the domain we used spectral nudging of waves longer than 2500 km above the boundary layer moisture was not nudged at any level this constrained the synoptic scales to follow reanalysis while allowing the model to develop the small scale dynamics responsible for the rainfall nudging of the large scales successfully eliminated the variation of precipitation results when the grid was moved we suggest that this technique is necessary for all downscaling studies with regional models with domain sizes of a few thousand kilometers and larger embedded in global models

first survey of antarctic sub ice shelf sediments reveals mid holocene ice shelf retreat the retreat of five small antarctic peninsula ice shelves in the late 20th century has been related to regional possibly anthropogenic climate warming we use the record of ice rafted debris ird in cores to show that the prince gustav channel ice shelf also retreated in mid holocene time early and late holocene age sediments contain ird derived entirely from local ice drainage basins which fed the section of ice shelf covering each site core top and mid holocene 5 2 ka sediments include a wider variety of rock types recording the drift of far traveled icebergs which implies seasonally open water at the sites the period when the prince gustav ice shelf was absent corresponds to regional climate warming deduced from other paleoenvironmental records we infer that the recent decay cannot be viewed as an unequivocal indicator of anthropogenic climate perturbation