thinning and volume loss of the arctic ocean sea ice cover 2003 2008 1 we present our best estimate of the thickness and volume of the arctic ocean ice cover from 10 ice cloud and land elevation satellite icesat campaigns that span a 5 year period between 2003 and 2008 derived ice drafts are consistently within 0 5 m of those from a submarine cruise in mid november of 2005 and 4 years of ice draft profiles from moorings in the chukchi and beaufort seas along with a more than 42 decrease in multiyear my ice coverage since 2005 there was a remarkable thinning of 0 6 m in my ice thickness over 4 years in contrast the average thickness of the seasonal ice in midwinter 2 m which covered more than two thirds of the arctic ocean in 2007 exhibited a negligible trend average winter sea ice volume over the period weighted by a loss of 3000 km3 between 2007 and 2008 was 14 000 km3 the total my ice volume in the winter has experienced a net loss of 6300 km3 40 in the 4 years since 2005 while the first year ice cover gained volume owing to increased overall area coverage the overall decline in volume and thickness are explained almost entirely by changes in the my ice cover combined with a large decline in my ice coverage over this short record there is a reversal in the volumetric and areal contributions of the two ice types to the total volume and area of the arctic ocean ice cover seasonal ice having surpassed that of my ice in winter area coverage and volume became the dominant ice type it seems that the near zero replenishment of the my ice cover after the summers of 2005 and 2007 an imbalance in the cycle of replenishment and ice export has played a significant role in the loss of arctic sea ice volume over the icesat record

distribution of terrigenous lipids in marine sediments off northeastern taiwan surface sediments on the continental margin off northeastern taiwan have been analyzed for terrigenous lipids including n alkanes n fatty alcohols and sterols marine input to the sediments is particularly low based on the average n c17 n c29 alkane and n c16 n c28 fatty alcohol ratios 0 15 0 13 and 0 13 0 06 respectively this may be due to the fact that marine lipids are more prone to degradation than terrestrial ones the study area has the highest plant wax n alkane contribution average carbon preference index 3 9 1 2 among the coastal marine areas surrounding taiwan lateral particle transport from the southern east china sea shelf and river runoff from the east taiwan coast are considered to be the major contributors the distributions of plant wax n alkane and n alkanol concentrations normalized to total organic carbon toc in the study area generally show maximum values on the upper slope of the southernmost okinawa trough but not for phytosterols linear regression of toc versus plant wax n alkane concentrations show a weak relationship r 0 64 p 0 001 and an even weaker relationship r 0 42 p 0 05 between toc and plant wax n fatty alcohol concentrations is found this could be attributed to several factors 1 a complex input not a point source of terrigenous organic matter to the study area 2 toc also including marine organic matter 3 temporal variations in river flow due to flooding and 4 different rates of degradation for toc and individual biomarkers however in spite of those factors toc and phytosterol concentrations are positively linearly correlated r 0 85 p 0 001 implying that the dilution of phytosterols in terrigenous organic carbon with marine organic carbon with or without the phytosterols follows a nearly constant ratio which is remarkable in addition the predominant source of diploptene in the sediments does not appear to be of higher plant origin

poleward deflection of storm tracks an analysis of 11 years of european centre for medium range weather forecasts data focuses primarily on the vertically averaged high frequency transients the conclusions are discussed in the context of a the winter storm track b monthly variability and c interannual variability a winter storm track results show that the pattern of the forcing by the high frequency eddies along the storm track is highly correlated with the stationary circulation and the forcing itself is primarily responsible for the location of the trough ridge system associated with the stationary flow the results also clarify the role of wind component covariance terms u9y9 and y9 2 2 u9 2 in the column averaged vorticity forcing the simpler term u9y9 has the well known effect of intensifying the anticyclonic cyclonic tendencies on the southern northern side of the jet thereby producing an increase in the barotropic component of the zonal jet the y9 2 2 u9 2 term displays a quadrupole pattern which is also approximately in phase with the trough ridge system associated with the stationary flow b monthly variability eddy activity has been shown to possess a seasonal life cycle increasing during the early fall and reaching a maximum around the month of november then decaying for most of the winter months month to month variations in eddy activity over the pacific ocean show that energy levels increase up through november decreasing thereafter at the same time the trough ridge circulation pattern is intensifying by december baroclinicity in the western pacific has increased substantially and low level eddies are found to break by the middle of the ocean upper level eddies start to break well before reaching the west coast of north america resulting in a displacement of the maximum in y9 2 2 u9 2 westward from its november position and increasing the trough ridge forcing by the high frequency eddies c interannual variability wintertime eddy kinetic energy is seen to extend further eastward through the pacific ocean during the warm phase but displays an abrupt termination during the cold phase anomalies in the eddy transient forcing tend to be quite similar to that of the pacific north american pattern itself the extension of the storm track during the warm phase resembles that of fall conditions and is present in the winter season because the source of low level baroclinicity

denudation history of eastern indian peninsula from apatite fission track analysis linking possible plume related uplift and the sedimentary record abstract the late archaean early proterozoic 2 5 ga eastern dharwar craton edc eastern india which underlies much of the drainage basins of the krishna and godavari rivers has undergone an erosionally controlled evolution since the pan african event 500 550 ma this evolution has been responsible for the sedimentation and overall development of the krishna godavari kg sedimentary basin in order to reconstruct the denudation history of the edc which forms the hinterland to the petroliferous kg basin we report apatite fission track aft data from 41 samples thermal history modelling suggests that little denudation occurred before mid cretaceous time however during the late cretaceous accelerated cooling commenced from a temperature range of 60 75 c assuming a low palaeogeothermal gradient of 10 c km similar to that of the present day cooling of the edc translates to 0 5 2 km of denudation during the late cretaceous and a total of 4 km since that time the denudation history is closely related to the sedimentary record in the kg basin the episode of accelerated cooling in the late cretaceous is interpreted as a geomorphic response to uplift of the indian peninsula possibly resulting from an ascending mantle plume which produced the voluminous deccan traps at the k t boundary the denudation history coupled with previous palaeocurrent studies in the kg basin suggest that the krishna godavari drainage system was established in late cretaceous time

one dimensional evolution of the upper water column in the atlantic sector of the arctic ocean in winter a one dimensional model is employed to reproduce the observed time evolution of hydrographic properties in the upper water column during winter between 26 january and 11 march 2015 in a region north of svalbard in the nansen basin of the arctic ocean from an observed initial state vertical diffusion equations for temperature and salinity give the hydrographic conditions at a later stage observations of microstructure are used to synthesize profiles of vertical diffusivity k representative of varying wind forcing conditions the ice ocean heat and salt fluxes at the ice ocean interface are implemented as external source terms estimated from the salt and enthalpy budgets using friction velocity from the rossby similarity drag relation and the ice core temperature profiles we are able to reproduce the temporal evolution of hydrography satisfactorily for two pairs of measured profiles suggesting that the vertical processes dominated the observed changes sensitivity tests reveal a significant dependence on k variation in other variables such as the temperature gradient of the sea ice the fraction of heat going to ice melt and the turbulent exchange coefficient for heat are relatively less important the increase in salinity as a result of freezing and brine release is approximately 10 significantly less than that due to entrainment 90 from beneath the mixed layer entrainment was elevated during episodic storm events leading to melting the results highlight the contribution of storms to mixing in the upper arctic ocean and its impact on ice melt and mixed layer salt and nutrient budgets

on the origin of the chemical properties of the arctic ocean halocline profiles of chemical constituents in seawater above the alpha ridge in the central arctic ocean obtained during the canadian expedition to study the alpha ridge cesar support a model in which the halocline is maintained by dense saline water produced on the continental shelves within the arctic ocean by the formation of sea ice it is argued that nutrient regeneration on the continental shelves largely accounts for the nutrient maximum that has been observed in the upper halocline over a wide region of the arctic ocean and that while the bering sea and north altantic can be recognized as origins of halocline water water masses from these regions undergo sufficient changes in their chemical properties within the arctic ocean significant that they no longer retain their identity in the halocline

hydrographic conditions during the 2002 sbi process experiments abstract a review of the hydrographic data from the 2002 western arctic shelf basin interactions sbi process cruises permits the following conclusions 1 temperature salinity relationships were similar to canonical descriptions but at five stations in the outer shelf slope region warm high salinity atlantic layer water appeared to have risen displaced the lower halocline and mixed with shelf upper halocline water 2 primary production in the sbi study region was strongly influenced by the advection of dissolved inorganic nitrogen din entering via bering strait this import of din ammonium nitrate nitrite is modified by local processes but without the bering strait inflow biological productivity in the sbi region would be much lower 3 in comparison to the inflowing atlantic waters din urea phosphate and din urea silicate ratios in the pacific waters that dominated the upper 150 m of the water column were low they were also low relative to redfield uptake ratios for phytoplankton 4 microbial processes continue to destroy din in significant quantities as the pacific waters transit the sbi region 5 nitrate and ammonium were the principal contributors to din nitrite concentrations were always

the first record of the permian glossopteris flora from sri lanka implications for hydrocarbon source rocks in the mannar basin strata exposed near tabbowa tank tabbowa basin western sri lanka have yielded thefirst representatives of the distinctive permian glossopteris flora from that country the assemblageincludes gymn

fixed point observation of mixed layer evolution in the seasonally ice free chukchi sea turbulent mixing due to gale winds and internal gravity waves abstracta fixed point observation using the r v mirai was conducted in the ice free northern chukchi sea of the arctic ocean during september of 2013 during the program the authors performed repeated microstructure measurements to reveal the temporal evolution of the surface mixed layer and mixing processes in the upper water column the shelf region was initially characterized by a distinct two layer system comprising a warmer fresher top layer and a colder saltier bottom layer during the two week observation period the top layer water showed two types of mixing processes near surface turbulence due to strong wind forcing and subsurface mixing due to internal gravity waves in the first week when the top layer was stratified with fresh sea ice meltwater turbulent energy related to internal waves propagated through the subsurface stratification resulting in a mechanical overturning near the pycnocline followed by enhanced mixing there in the second week gale winds directly stirred up the upper w

anisotropy of heterogeneity scale lengths in the lower mantle from pkikp precursors summary the anisotropy of heterogeneity scale lengths in the lower mantle is investigated by modelling its evect on the high frequency precursors of pkikp scattered by the heterogeneities although models having either an isotropic or an anisotropic distribution of scale lengths can fit the observed coda shapes of short period precursors the frequency content of broad band pkikp precursors favours a dominantly isotropic distribution of scale lengths precursor coda shapes are consistent with 1 per cent fluctuations in p velocity in the wavenumber band 0 05 0 5 km 1 extending to 1000 km above the core mantle boundary and with a d region open to circulation throughout the lower mantle the level of excitation of pkikp precursors observed in the frequency band 0 02 2 hz requires a power spectrum of heterogeneity that is nearly white or slowly increasing with wavenumber anisotropy of scale lengths may exist in a d layer having larger horizontal than vertical scale lengths and produce little or no detectable evects on pkikp precursors for p velocity perturbations as high as 3 per cent when averaged over a vertical scale of several kilometres and much higher when averaged over scales of hundreds of metres or less

late quaternary environmental and sea level changes from kolleru lake se india inferences from mineral magnetic geochemical and textural analyses abstract the present study employs mineral magnetic geochemical and textural parameters to elucidate the climate and sea level change signatures from kolleru lake sediments representing the inter deltaic part of the krishna godavari sedimentary basin kg basin for this purpose four cores were obtained which included significant peat the conventional radiocarbon dating suggested that the peat formation took place during 9 ka 6 ka with an average sedimentation rate of 0 31 cm y thermomagnetic analysis identifies titanomagnetite magnetite and hematite as the dominant magnetic mineralogy of the kg basin sediments the variation in magnetic mineralogy is related to paleoclimatic and paleoenvironmental processes the transitions between titano magnetite and hematite coincide with peat layers of the cores as indicated by sirm saturation isothermal remanent magnetization magnetic susceptibility and s ratio defined by irm 0 3t sirm values the various mineral magnetic parameters and s ratio along with major elemental concentrations of ti al fe and zr show signatures of an arid event before 10 ka between 9 ka 8 ka periods and during the last 5 5 ka the overall climate of warm and humid type was inferred from 10 ka to 9 ka which correlates with early holocene optima and 6 ka to 5 5 ka of middle holocene the presence of evaporite crystals in the lowermost part of the cores corroborated by mineral magnetic and geochemical proxies indicates sub aerially weathered facies of the arid late pleistocene similarly the peat layers rich in mangrove pollen indicate sea level changes between 10 ka and 6 ka the sub surface position of the pleistocene weathered layer and the holocene peat layer suggests tectonic subsidence of the area which is situated over the basement graben known as gudiwada sub basin

anisotropic shear wave velocity structure of the earth s mantle a global model 1 we combine a new large data set of surface wave phase anomalies long period waveforms and body wave travel times to construct a three dimensional model of the anisotropic shear wave velocity in the earth s mantle our modeling approach is improved and more comprehensive compared to our earlier studies and involves the development and implementation of a new spherically symmetric reference model simultaneous inversion for velocity and anisotropy as well as discontinuity topographies and implementation of nonlinear crustal corrections for waveforms a comparison of our new three dimensional model s362ani with two other models derived from comparable data sets but using different techniques reveals persistent features 1 strong 200 km thick high velocity anomalies beneath cratons likely representing the continental lithosphere underlain by weaker fast anomalies extending below 250 km which may represent continental roots 2 weak velocity heterogeneity between 250 and 400 km depths 3 fast anomalies extending horizontally up to 2000 3000 km in the mantle transition zone beneath subduction zones 4 lack of strong long wavelength heterogeneity below 650 km suggesting inhibiting character of the upper mantle lower mantle boundary and 5 slow velocity superplumes beneath the pacific and africa the shear wave radial anisotropy is strongest at 120 km depth in particular beneath the central pacific lateral anisotropic variations appreciably improve the fit to data that are predominantly sensitive to the uppermost and lowermost mantle but not to the waveforms that control the transition zone and midmantle depths tradeoffs between lateral variations in velocity and anisotropy are negligible in the uppermost mantle but noticeable at the bottom of the mantle

effect of fe enrichment on seismic properties of perovskite and post perovskite in the deep lower mantle recent experimental measurements of the equation of state of perovskites and post perovskites in the mg fe sio3 and mg fe al fe al si o 3 systems over a wide range of iron contents are used to constrain the effects of fe and al on density and bulk modulus of these phases at deep mantle pressures the density of fe bearing perovskite follows a linear relationship with fe content at a representative mid mantle depth of 1850 km 80 gpa 80 g cm 3 5 054 1 1 270 3 x fe the bulk modulus of silicate perovskite is not sensitive to fe content and follows the relationship k 80 gpa 546 2 12 25 x fe the velocity heterogeneity parameter partial derivative ln v b partial derivative x fe determined by experimental values for the bulk sound speed is 0 10 1 in agreement with theory and the behaviour of other fe bearing silicates near the core mantle boundary fe rich post perovskite is observed to be more compressible than the mg end member in contrast to theoretical predictions from experimental data the densities of perovskite and post perovskite at 125 gpa 2700 km depth are 125 pv g cm 3 5 426 11 1 38 4 x fe and 125 ppv g cm 3 5 548 1 1 41 3 x fe the density contrast across the post perovskite transition is similar to 2 per cent irrespective of fe content but the contrast in bulk sound speed increases with fe content al rich silicates exhibit no significant differences in density or compressibility relative to al free silicates but may be responsible for seismic heterogeneities due to differences in the depth and width of the post perovskite transition observations of increased densities in large low shear velocity provinces and ultra low velocity zones may be consistent with local iron enrichment from mg 90 to mg 78 88 and mg 50 respectively

time and temperature in petroleum formation application of lopatin s method to petroleum exploration n v lopatin in the soviet union has developed a method for taking both time and temperature into account as factors in thermal maturation of kerogen lopatin s time temperature index of maturity tti values correlate with the thermal regimes corresponding to generation and preservation of hydrocarbons because such information is potentially of great interest for oil exploration a calibration and evaluation have been made of lopatin s method within the limitations of the data presently available the following statements can be made 1 the rate of the chemical reactions involved in thermal maturation of organic material appears to double with every 10 c 18 f rise in temperature 2 threshold values of lopatin s time temperature index of maturity tti are 15 onset of oil generation 75 peak oil generation 160 end oil generation 500 40 oil preservation deadline 1 000 50 oil preservation deadline 1 500 wet gas preservation deadline 65 000 dry gas preservation deadline 3 tti values calculated from lopatin reconstructions consistently agree with other maturation parameters commonly used by petroleum geochemists potential applications of lopatin s method for oil exploration include timing of oil generation calculation of volume of hydrocarbons generated within a basin and determination of economic deadlines

east west differences in water mass nutrient and chlorophyll a distributions in the sea ice reduction region of the western arctic ocean 1 the r v mirai conducted hydrographic surveys in the western arctic ocean during summer 2004 across a front between cold arctic water and warm water from the pacific ocean where sea ice cover has been largely reduced in recent summers the hydrographic data indicate a new type of vertical temperature minimum water west of the front along isohaline surfaces with approximate salinity s of 32 which is fresher than the typical temperature minimum s 33 caused by spreading of pacific winter water pww mainly to the east of the front both of the temperature minimum waters are characterized by low potential vorticity with near freezing temperature suggesting that they are formed by winter convection with sea ice formation a difference between the waters results from a large contribution of sea ice meltwater to the fresh temperature minimum frtmin water of s 32 the distributions of the sea ice meltwater contribution and nitrogen deficit suggest that summer shelf water largely influenced by the sea ice melt in the chukchi sea is modified by winter convection on its way to the chukchi abyssal plain to form the frtmin water this water supplies nutrients through the water distribution to the west of the front at depths shallower than the nutrient maximum layer caused by the pww spreading the shallower nutrient supply by the frtmin water combined with light penetration without sea ice cover could produce a prominent chlorophyll a maximum layer west of the front

stable isotope geochemistry of coals humic kerogens and related natural gases isotope systematics are well defined for conventional sapropelic type i ii kerogens and their associated bacterial and thermogenic natural gas products these geochemical tools are used to estimate source type maturity and depositional environment and as a correlation technique in many cases the natural gas signatures in near surface samples and drill cuttings can be used to classify or predict a deeper lying source rock or reservoir corresponding interpretative schemes for coals type iii kerogens and their associated hydrocarbons are progressing quickly the shift in attention to humic sources is driven primarily by depletion of conventional oil and gas resources and the economic and societal requirements of coal and coal bed methane carbon hydrogen and nitrogen stable isotope variations can be large between different coals and humic kerogens these differences can often be recognized in their bulk 13corg dorg and 15norg values isotope signatures of coals can be diagnostic of several factors including deposit age type geographic location maturity and generation history however these characteristic isotopic variations are substantially better defined by the c h and n isotope ratios of the separate maceral groups such as vitrinite exinite and inertinite this new application of stable isotopes at the maceral and compound levels have great potential to improve the interpretative precision over conventional whole coal or bulk techniques hydrocarbon gases including coal gases derived from coals and humic kerogens can be distinguished from type i ii sources based on their molecular rations i e c1 c2 c3 and by comparing their stable isotope compositions especially 13cch4 and dch4 the 13cc2h6 can also be valuable but ethane is generally present in small amount 1 vol and requires

ab initio study of the composition dependence of the pressure induced spin crossover in perovskite mg1 x fex sio3 abstract we present ab initio calculations of the zero temperature iron high to low spin crossover in mg 1 x fe x sio 3 perovskite at pressures relevant to earth s lower mantle equations of state are fit for a range of compositions and used to predict the fe spin transition pressure and associated changes in volume and bulk modulus we predict a dramatic decrease in transition pressure as fe concentration increases this trend is contrary to that seen in ferropericlase and suggests the energetics for spin crossover is highly dependent on the structural environment of fe both local density approximation lda and generalized gradient approximation gga exchange correlation methods are used and both methods reproduce the same compositional trends however gga gives a significantly higher transition pressure than lda the spin transition is made easier by the decreasing spin flip energy with pressure but is also driven by the change in volume from high to low spin volume trends show that high spin fe 2 is larger than mg 2 even under pressure but low spin fe 2 is smaller at ambient conditions and approximately the same size as mg 2 under high pressure indicating that low spin fe 2 is less compressible than high spin fe 2 we find large changes between high and low spin in the slope of volume with fe concentration although these changes are small in absolute magnitude for small fe content they are still important when measured per fe and could be relevant for calculating partitioning coefficients in the lower mantle

environmental influence on the biohopanoid composition of recent sediments abstract bacteriohopanepolyols are the biological precursors of extended hopane biomarkers which are ubiquitous in the geosphere the abundance and composition of these biohopanoids were determined for modern sediments from eight depositional environments by gc ms analysis of hopanols derived from a side chain cleavage reaction periodic acid and sodium borohydride of the bacteriohopanepolyols we report quantitative data for bacteriohopanetetrol bht composite tetrafunctionalised biohopanoids pentafunctionalised biohopanoids and hexafunctionalised biohopanoids bht was found in concentrations higher than previously reported up to ca 1500 g g toc but comprised only a relatively small proportion 0 26 of the total biohopanoids in all except one sample composite tetrafunctionalised biohopanoids were the dominant group of bacteriohopanepolyols in all other sediments and are likely to be a major source of the geologically occurring extended hopanes hexafunctionalised biohopanoids were most abundant in lake sediments particularly two small highly productive stratified lakes where they comprised 20 40 of total biohopanoids this feature is interpreted to be due to greater contribution to the organic matter of these sediments from type i methanotrophic bacteria which produce dominantly hexafunctionalised biohopanoids consistent with the environmental settings in the marine environments where sulphate reduction is dominant hexafunctionalised biohopanoids are relatively minor constituents 2 6 of total biohopanoids these data comprise the first clear demonstration that bacteriohopanepolyols vary in composition between depositional environments and have the potential to preserve specific bacterial source information in sedimentary organic matter

circulation on the north central chukchi sea shelf abstract mooring and shipboard data collected between 1992 and 1995 delineate the circulation over the north central chukchi shelf previous studies indicated that pacific waters crossed the chukchi shelf through herald valley in the west and barrow canyon in the east we find a third branch through the central channel onto the outer shelf the central channel transport varies seasonally in phase with bering strait transport and is 0 2 sv on average although some of this might include water entrained from the outflow through herald valley a portion of the central channel outflow moves eastward and converges with the alaskan coastal current at the head of barrow canyon the remainder appears to continue northeastward over the central outer shelf toward the shelfbreak joined by outflow from herald valley the mean flow opposes the prevailing winds and is primarily forced by the sea level slope between the pacific and arctic oceans current variations are mainly wind forced but baroclinic forcing associated with upstream dense water formation in coastal polynyas might occasionally be important winter water mass modification depends crucially on the fall and winter winds which control seasonal ice development an extensive fall ice cover delays cooling limits new ice formation and results in little salinization in such years bering shelf waters cross the chukchi shelf with little modification in contrast extensive open water in fall leads to early and rapid cooling and if accompanied by vigorous ice production within coastal polynyas results in the production of high salinity 33 shelf waters such interannual variability likely affects slope processes and the transport of pacific waters into the arctic ocean interior

nutrient supply and biological response to wind induced mixing inertial motion internal waves and currents in the northern chukchi sea a fixed point observation station was set up in the northern chukchi sea during autumn 2013 and for about 2 weeks conductivity temperature depth ctd water samplings 6 h and microstructure turbulence measurements 2 to 3 times a day were performed this enabled us to estimate vertical nutrient fluxes and the impact of different types of turbulent mixing on biological activity there have been no such fixed point observations in this region where incoming low salinity water from the pacific ocean river water and sea ice meltwater promote a strong pycnocline halocline that stabilizes the water column previous studies have suggested that because of the strong pycnocline wind induced ocean mixing could not change the stratification to impact biological activity however the present study indicates that a combined effect of an uplifted pycnocline accompanied by wind induced inertial motion and turbulent mixing caused by intense gale force winds 10 m s 1 did result in increases in upward nutrient fluxes primary productivity and phytoplankton biomass particularly large phytoplankton such as diatoms convective mixing associated with internal waves around the pycnocline also increased the upward nutrient fluxes and might have an impact on biological activity there for diatom production at the fixed point observation station it was essential that silicate was supplied from a subsurface silicate maximum a new feature that we identified during autumn in the northern chukchi sea water mass distributions obtained from wide area observations suggest that the subsurface silicate maximum water was possibly derived from the ventilated halocline in the canada basin

electronic spin transitions in iron bearing mgsio3 perovskite the electronic spin state of iron in perovskites with the chemical composition mg0 9375fe0 0625sio3 mg0 8750fe0 1250sio3 and mg0 9375fe0 0625si0 9375fe0 0625o3 have been determined at 0 k and various pressures between 40 160 gpa using ab initio methods the results indicate that ferric iron exhibits a wide range of spin transition pressures between about 60 160 gpa while ferrous iron has a much narrower span between about 130 145 gpa in general the lowest spin transition pressures are associated with the most energetically favorable substitution configurations where iron atoms are closest together the effect of spin state on calculated elastic properties is found to be small c 2006 elsevier b v all rights reserved

the role of sea ice and other fresh water in the arctic circulation salinity stratification is critical to the vertical circulation of the high latitude ocean we here examine the control of the vertical circulation in the northern seas and the potential for altering it by considering the budgets and storage of fresh water in the arctic ocean and in the convective regions to the south we find that the present day greenland and iceland seas and probably also the labrador sea are rather delicately poised with respect to their ability to sustain convection small variations in the fresh water supplied to the convective gyres from the arctic ocean via the east greenland current can alter or stop the convection in what may be a modern analog to the halocline catastrophes proposed for the distant past the north atlantic salinity anomaly of the 1960s and 1970s is a recent example it must have had its origin in an increased fresh water discharge from the arctic ocean similarly the freshening and cooling of the deep north atlantic in recent years is a likely manifestation of the increased transfer of fresh water from the arctic ocean into the convective gyres finally we note that because of the temperature dependence of compressibility a slight salinity stratification in the convective gyres is required to efficiently ventilate the deep ocean

wind driven shelf basin exchange on an arctic shelf the joint roles of ice cover extent and shelf break bathymetry 1 the efficiency of shelf basin exchange sbe in polar regions during summer is strongly moderated by the location of the ice edge relative to underlying topography numerical model calculations suggest that upwelling favorable winds generate very little sbe so long as the ice edge remains shoreward of the shelf break but an abrupt onset of shelf break upwelling takes place when the ice edge retreats beyond the shelf break a climatology 1968 2000 of ice conditions from the canadian shelf of the beaufort sea shows large interannual variability in ice edge extent and duration of ice free conditions in summer similarly available hydrographic data reflect a corresponding variability in water mass properties under scenarios of climate warming associated with greenhouse gas build up both the extent and duration of summer melt back are predicted to increase and this may have dramatic impacts on sbe and biological productivity

electronic spin state of fe al containing mgsio3 perovskite at lower mantle conditions abstract we have investigated silicate perovskite with composition mg 0 83 fe 0 21 al 0 06 si 0 91 o 3 relevant for the lower mantle at pressures up to 81 gpa and temperatures up to 2000 k using conventional mossbauer spectroscopy and synchrotron nuclear forward scattering nfs combined with double sided laser heating in a diamond anvil cell room temperature mossbauer and nfs spectra at low pressure are dominated by high spin fe 2 with minor amounts of fe 3 and a component assigned to a metastable position of high spin fe 2 in the a site predicted by computational studies nfs data show a sharp transition 2 to a new component with extremely high quadrupole splitting similar to previous studies mossbauer data show the same transition but over a broader pressure range likely due to the higher pressure gradient the new fe 2 component is assigned to intermediate spin fe 2 consistent with previous x ray emission studies nfs data at high temperatures and high pressures comparable to those in the lower mantle are consistent with the presence of fe 2 only in the intermediate spin state and fe 3 only in the high spin state our results are therefore consistent with the occurrence of spin crossover only in fe 2 in fe al containing perovskite within the lower mantle

barrow canyon volume heat and freshwater fluxes revealed by long term mooring observations between 2000 and 2008 1 barrow canyon in the northeast chukchi sea is a major conduit for pacific water to enter the interior arctic basins assemblies of annual september 2000 to august 2008 temperature salinity and velocity data acquired from a mooring array in the mouth of barrow canyon and high resolution hydrographic and velocity transects along the mooring array in 2002 2010 and 2011 have enabled a direct computation of volume heat and freshwater fluxes annual mean volume transport through barrow canyon was 0 45 sv which consisted of 0 44 sv of pacific water and 0 01 sv of atlantic water annual mean pacific water transport through barrow canyon represents 55 of the long term mean pacific water inflow through the bering strait during summer more of the pacific inflow was advected to an eastern path as the alaskan coastal current that flows along the alaskan coast to barrow canyon the freshwater flux through barrow canyon was 904 km3 yr which is equivalent to 5 of the freshwater content of the canada basin the annual averaged heat flux displayed substantial interannual variability ranging from 0 93 to 3 02 tw which could melt 88 000 290 000 km2 of 1 m thick ice a relationship exists between the measured barrow canyon transport and local winds such that under southerly winds the northward flow of water through the canyon increases such wind conditions are induced by the weaker sea level pressure contrast between the arctic and north pacific caused by a decrease in the pressure over the arctic and an increase over the north pacific

origin of petroliferous bitumen from the buyuk menderes gediz geothermal graben system denizli saraykoy western turkey abstract the kb 5 well is located at the intersection of the geothermally active menderes and gediz graben systems in western turkey significant volumes of petroleum like material plm with its associated thermal water 120 c erupted onto the surface during drilling from a depth of 120 132 m i e from the claystone and marl rich early to middle pliocene kolonkoya formation the purpose of this paper is 1 to characterize this plm 2 to assess the source characteristics from which the plm was likely generated and 3 to recognize the generation mechanism considering the geothermal gradual versus the hydrothermal rapid processes analytical organic geochemistry using thin layer chromatographic separation followed by gas chromatography mass spectrometry gc ms was carried out the plm is composed primarily of polar nso compounds asphaltenes 77 this feature is similar to hydrothermal petroleums e g calcite springs yellowstone national park wyoming the plm shows n alkanes ranging from n c 19 to n c 38 i e with a maximum at n c 30 but n alkanes are depleted in n c 19 an absence of acyclic isoprenoids pristane and phytane and considerably large ucm unresolved complex mixture indicate that the plm has been subjected to a moderate degree of alteration possibly by the accompanying hot geothermal waters the source specific biomarkers i e low c 29 nh c 30 h ratio presence of gammacerane and 18 h oleanane high c 35 c 34 homohopane ratio and c 29 sterane concentration n c 28 n c 27 n c 29 c 28 27 29 r steranes c 29 r c 27 r suggest that the plm is a petroleum and was most likely generated from a tertiary source rock with a carbonate clay rich lithology the source organic matter was predominantly terrestrial and bacterial detritus deposited in relatively saline anoxic environmental conditions maturity sensitive biomarker parameters i e t m t s c 29 sterane 20 s 20 s 20 r 0 35 c 32 hopane 22 s 22 s 22 r 0 57 low diasterane regular sterane ratio correspond to a maturity level of approximately 0 50 0 60 r o this level of maturation could not be reached by such a young upper miocene lower pliocene and shallow sedimentary column max 600 m in the absence of instantaneous hydrothermal activity pahs are not detectable but series of alkylbenzenes alkyltoluenes alk 1 enes and triaromatic steranes are present the lack of organic richness and maturity in the drilled section of the kb 5 well indicates that the petroleum was generated in the deeper sections of the formation the temperature profile of the well and composition of the hydrocarbons in the petroleum suggest that the temperature of the hydrothermal activity during hydrocarbon generation was

kerogen origin evolution and structure kerogen commonly defined as the insoluble macromolecular organic matter om dispersed in sedimentary rocks is by far the most abundant form of om on earth this fossil material is of prime importance as the source of oil and natural gas moreover kerogen can provide essential information on major topics such as past environments climates and biota this review reports the main advances in kerogen studies since the comprehensive synthesis edited by durand durand b ed kerogen insoluble organic matter from sedimentary rocks editions technip paris 1980 it is organized into eight sections the first two are concerned with the successive definitions of kerogen and the definition used here the different techniques used for kerogen isolation without loss or degradation and basic kerogen analysis the third and fourth focus on sedimentary om sources and preservation processes in relation to depositional environment including sedimentation conditions favourable for kerogen accumulation and extrapolation to past geological time great strides have been made in the latter topics over the last 25 years owing to a combination of classical studies in organic geochemistry and studies in other domains such as biogeochemistry oceanography hydrology and soil science along with the development of powerful analytical tools the next two sections deal with the different kerogen classifications by type and kerogen evolution and maturation upon burial in sediments structural modelling of coal and kerogen based on physical and or chemical structural analysis is described in the following section although only statistical the models thus derived provide a synthetic view of the main structural resemblances and differences among various samples in relation to source maturity or physicochemical properties finally the last section explores some of the advances in kerogen understanding expected for the near future the review includes a list containing about 500 references

spatial patterns of primary production on the shelf slope and basin of the western arctic in 2002 in the spring and summer of 2002 primary production in the chukchi sea was measured using 14 c uptake experiments our cruise track encompassed the shelf and continental slope area of the chukchi and beaufort seas progressing into deep water over the canada basin the study area experienced upwards of 90 ice cover during the spring with ice retreating into the basin during the summer production in the spring was light limited due to ice cover with average euphotic zone production rates of o0 3 g c m 2 d 1 values of 8 g c m 2 d 1 were observed in association with surface bloom conditions during the initial ice breakup considerable nutrient reduction in the surface waters took place between the spring and summer cruise and although not observed this was attributed to a spring bloom decreased ice cover and increased clarity of surface waters in the summer allowed greater light penetration the highest rates of production during the second cruise were found at 25 30 m coincident with the top of the nutricline daily euphotic zone productivity in the summer averaged 0 78 g c m 2 d 1 on the shelf and 0 32 g c m 2 d 1 on the edge of the canada basin these data provide an estimated annual production of 90 g c m 2 yr 1 in the study area

effect of normal faulting on in situ stress a case study from mandapeta field krishna godavari basin india abstract the horizontal compressive stress orientations for mandapeta field in krishna godavari k g basin had been calculated from borehole breakout data using four arm dipmeter caliper logs the minimum horizontal stress magnitude for mandapeta field was calculated from pore pressure data using poroelastic equation three dimensional 3 d stress modeling using finite element analyses has been carried out for layered sediments and faulted layered sediments in the mandapeta sub basin the length and width of the models are chosen as 5 km and 2 km respectively vertical depths of models are considered for sediments at depth 2 km to 5 km this paper presents a numerical study of stress distributions contours and trajectories around fault models of layered geometries submitted to overburden and unequal horizontal compressive loads reorientation and magnitude variation of in situ stresses near faults and stress discontinuities across faults are observed changes in the stress patterns are observed at the interfaces between sediments due to faulting and sediment basement layers due to contrast in elastic constants remarkable stress gradients are observed between the sediment and basement magnitudes of normal component of stress decrease near the faulting whereas shear stress magnitudes increase at the faulting site there is increase of horizontal principal stresses in the downthrown faulted layers the maximum horizontal principal stress rotates about 90 just adjacent to the fault fluid flow at depth of oil reservoir could be indirectly influenced by the stress contours and by geometries of the stress trajectories fluid migration in low permeability reservoir may occur in response to mean stress gradients induced by the tectonic loading the areas of high mean stress gradient are located at the interface between sediment and basement whereas the areas of low mean stress gradient is exactly coinciding with the areas of upper sediments

use of ammonium and other nitrogen tracers to investigate the spreading of shelf waters in the western arctic halocline 1 the contribution of nutrient regeneration in summer to the nutrient maximum associated with bering sea winter water bsww is estimated from the ammonium data which was obtained in the outer shelf region of the chukchi sea for the first time by the r v mirai in 2002 the contribution rate reaches 20 30 which is larger than the rate studied earlier inside the chukchi shelf such bsww influenced by the regeneration spreads to the chukchi shelf slope up to the isobath of 3000 m however was not found in the canada basin the ammonium and a nitrogen deficit are also useful tracers to study the spreading of shelf waters that are less saline than bsww in the canada basin a small amount of ammonium 2 m was observed east of the northwind ridge this small amount of ammonium would be associated with the spreading of eastern chukchi summer water via the barrow canyon around the chukchi borderland a prominent nitrogen deficit layer was found it would be accompanied by western chukchi summer water via the hope valley herald valley channel the water flows into the chukchi abyssal plain and then spreads eastward to the west of the northwind ridge with the decrease of nitrogen deficit signal

the thermal history of the eastern officer basin south australia evidence from apatite fission track analysis and organic maturity data the eastern officer basin in south australia contains a neoproterozoic to devonian succession overlain by relatively thin 500 m permian mesozoic and tertiary deposits within the basin fill there are several major unconformities representing uncertain amounts of erosion three of these surfaces are associated with regional deformational events regional unconformities formed between 560 and 540 ma petermann ranges orogeny approximately 510 490 ma delamerian orogeny 370 300 ma alice springs orogeny 260 150 ma and 95 40 ma afta results from 13 samples of neoproterozoic cambrian and permian sedimentary rocks in five wells giles 1 manya 2 5 and 6 and lake maurice west 1 show clear evidence for a number of distinct thermal episodes results from all samples are consistent with cooling from the most recent thermal episode beginning at some time between 70 and 20 ma maastrichtian miocene afta results from giles 1 indicate at least two pre cretaceous thermal episodes with cooling beginning between 350 and 250 ma carboniferous permian and between 210 and 110 ma late triassic albian results from manya 2 5 and 6 and lake maurice west 1 show evidence for at least one earlier higher temperature event with cooling from elevated paleotemperatures beginning between 270 and 200 ma late permian to late triassic these episodes can be correlated with other cooling erosional events outside the study area and the afta derived paleotemperatures are consistent with kilometre scale erosion for each of the episodes identified integration of the afta data with organic thermal maturation indicators mpi in the manya and giles 1 wells suggests that the cambrian and neoproterozoic successions in the northern part of the study area reached peak maturation prior to the permian while limited data from lake maurice west 1 allows peak maturation to have occurred as young as the late permian to late triassic thermal episode revealed by afta the approach outlined in this study is relevant to all ancient basins as it emphasises the importance of understanding events associated with neighbouring regions the thermal history of the officer basin as with most other ancient basins has been strongly affected by significant tectonic events throughout its history even though younger deposits are not preserved in the basin itself the recognition of these younger events and the implications of these events for the depositional history is important as it allows identification of the best regions for preservation of early generated hydrocarbons and in some cases suggests areas where generation of hydrocarbons could have occurred more recently than previously thought

stable intermediate spin ferrous iron in lower mantle perovskite iron has the ability to adopt different electronic configurations and transitions in its spin state in the lower mantle can significantly influence mantle properties and dynamics experimental results for two lower mantle perovskite compositions show that the intermediate spin state of iron is stable throughout the bulk of the lower mantle

intermediate spin ferrous iron in lowermost mantle post perovskite and perovskite the earth s lowermost mantle displays an important mineralogical transition from perovskite to post perovskite but the spin state of iron in these phases remains poorly known experimental results suggest that iron occurs in the intermediate spin state in both of these phases which implies that changes in physical properties of the lower mantle must be governed by factors other than spin transitions in iron

generation and hydrocarbon entrapment within gondwanan sediments of the mandapeta area krishna godavari basin india abstract the discovery of hydrocarbons mainly gas in commercial quantities from gondwanan sediments in the mandapeta field of krishna godavari basin india provided impetus for intensified exploration in mandapeta and the adjoining kommugudem draksharama and endamuru fields both oil and gas have been found in the reservoirs of mandapeta triassic and golapalli early cretaceous formations mature localised basal shales 1 0 1 1 ro in the mandapeta formation have sourced the oils from the mandapeta sandstone reservoir triassic the oils being produced from golapalli sandstone reservoir early cretaceous are relatively less mature and have been sourced by the underlying shales in the mandapeta formation at a maturity level of 0 80 0 85 ro the source and maturity data preclude liquid hydrocarbon sourcing from the kommugudem permian sequence permian coals and shales of the kommugudem formation are the major source rocks for gaseous hydrocarbons in this area the hydrocarbon generation started in early cretaceous in the kommugudem formation but the intermittent tectonic activity with associated structural developments has resulted in reorientation and redistribution of the then existing trap configurations the present day maturity level of the permian sediments in the mandapeta field is 1 2 ro or greater capable of generating gas dominantly the raghavapuram shale in the mandapeta area is adequately mature and has good hydrocarbon potential for oil generation the probability of finding hydrocarbon reserves in the sands of raghavapuram shales and other suitable traps is high modern seismic information together with geologic models can give new exploration leads

is the spin transition in fe2 bearing perovskite visible in seismology 1 we determine the elasticity of fesio3 perovskite for various spin configurations using density functional theory calculations the elastic moduli and the bulk seismic wave velocities are weakly affected by the spin transition however we show that the intrinsic differences in seismic anisotropy between the high spin and low spin phases of fe bearing perovskite coupled with lattice preferred orientation that can develop due and during the convection may lead to distinct seismic signatures between the top and the bottom of the lower mantle these signatures should be detectable in observations and they need to be taken into account in tomographic studies of the earth s lower mantle

shoaling of the nutricline with an increase in near freezing temperature water in the makarov basin 1 the water mass changes in the makarov basin and adjacent areas associated with the recent loss of arctic sea ice had not been studied in detail we combined data obtained from multiple cruises in these regions and used chemical tracers to investigate the spatial and temporal changes in water masses our data show that a previously present temperature maximum water has disappeared from the makarov basin and chukchi abyssal plain due to enhanced cooling and convection in the east siberian sea in addition a large volume of water has formed by cooling and convection and is flowing into the makarov basin producing a temperature minimum with relatively high nutrients and resulting in a shoaling of the nutricline this temperature minimum water likely originated from the eastern part of the east siberian sea where significant open water areas appeared after 2005 in the freeze up season the water mass boundary between this temperature minimum water and the pacific origin temperature minimum water shifted westward from the chukchi plateau in the early 2000s to the mendeleyev ridge in the late 2000s probably owing to a westward flow of the enhanced beaufort gyre associated with recent sea ice loss in the canada basin although the shoaling of the nutricline in the makarov basin could increase phytoplankton production such production could decrease in the southern makarov basin because a large amount of sea ice meltwater covers that region and might decrease the nutrient supply from the subsurface layer

influence of floral assemblage facies and diagenesis on petrography and organic geochemistry of the eocene bourgas coal and the miocene maritza east lignite bulgaria abstract numerous differences in the petrography and organic geochemistry of two tertiary low rank coal deposits of bulgaria formed within comparable depositional environments are outlined different floral assemblages are indicated as the main sources of organic matter for the eocene bourgas sub bituminous coals a warm climate plant community dominated by angiosperms is reflected in the biomarker composition whereas a coniferous flora was the main source of the resinous organic matter of the miocene maritza east lignite the results are in agreement with palaeobotanical data these differences in the peat forming vegetation of the paleogene compared to the neogene of bulgaria are attributed to decreasing temperature during the tertiary the abundance of resinous compounds relative to lipids from plant waxes long chain n alkanes as well as the preservation of plant tissue are mainly controlled by gymnosperm angiosperm ratios pristane phytane and diasterenes sterenes ratios reflect variations in redox conditions and the ph of the depositional environments caused by eustatic sea level changes freshwater inflow or varying ground water table changing eh and ph values are associated with differences in microbial activity controlling the extent of gelification of plant tissue bacteria most probably contributed to the aromatisation of triterpenoids in the mire enhanced thermal maturation of organic matter during diagenesis is reflected in higher contents of n alkanes and the presence of alkyl naphthalenes in the bourgas coals alkyl naphthalenes are thought to have been formed from pentacyclic triterpenoids rather than from resinous compounds

beaufort gyre freshwater reservoir state and variability from observations 1 we investigate basin scale mechanisms regulating anomalies in freshwater content fwc in the beaufort gyre bg of the arctic ocean using historical observations and data collected in 2003 2007 specifically the mean annual cycle and interannual and decadal fwc variability are explored the major cause of the large fwc in the bg is the process of ekman pumping ep due to the arctic high anticyclonic circulation centered in the bg the mean seasonal cycle of liquid fwc is a result of interplay between the mechanical ep and thermal ice transformations factors and has two peaks one peak occurs around june july when the sea ice thickness reaches its minimum maximum ice melt the second maximum is observed in november january when wind curl is strongest maximum ep and the salt input from the growing ice has not yet reached its maximum interannual changes in fwc during 2003 2007 are characterized by a strong positive trend in the region varying by location with a maximum of approximately 170 cm a 1 in the center of ep influenced region decadal fwc variability in the period 1950 2000 is dominated by a significant change in the 1990s forced by an atmospheric circulation regime change the center of maximum fwc shifted to the southeast and appeared to contract in area relative to the pre 1990s climatology in spite of the areal reduction the spatially integrated fwc increased by over 1000 km 3 relative to climatology