first reported sedimentary occurrence of berlinite alpo4 in phosphate bearing sediments from cioclovina cave romania this paper describes the first reported occurrence of berlinite alpo 4 formed entirely under sedimentary conditions berlinite appears as grayish or colorless fine crystals in vacuoles and along cracks in heavily compacted phosphate rich sediments within the cioclovina cave in romania the x ray powder diffraction pattern and the hexagonal unit cell of the cioclovina berlinite specimen compare well with other published determinations the lattice parameters are a 4 94 4 c 10 87 1 a v 230 1 3 a 3 microprobe analyses confirmed a nearly ideal formula for berlinite in situ guano combustion is responsible for the transformation of taranakite and for the dehydration of variscite into berlinite berlinite was successfully synthesized from these two minerals at atmospheric pressure and temperatures ranging from 350 to 600 c

combined influences of seasonal east atlantic pattern and north atlantic oscillation to excite atlantic multidecadal variability in a climate model the physical processes underlying the internal component of the atlantic multidecadal variability amv are investigated from a 1 000 yr pre industrial control simulation of the cnrm cm5 model the low frequency fluctuations of the atlantic meridional overturning circulation amoc are shown to be the main precursor for the model amv the full life cycle of amoc amv events relies on a complex time evolving relationship with both north atlantic oscillation nao and east atlantic pattern eap that must be considered from a seasonal perspective in order to isolate their action the ocean is responsible for setting the multidecadal timescale of the fluctuations amoc rise leading to a warm phase of amv is statistically preceded by wintertime nao and eap from lag 40 20 yrs associated wind stress anomalies induce an acceleration of the subpolar gyre spg and enhanced northward transport of warm and saline subtropical water concurrent positive salinity anomalies occur in the greenland iceland norwegian seas in link to local sea ice decline those are advected by the eastern greenland current to the labrador sea participating to the progressive densification of the spg and the intensification of ocean deep convection leading to amoc strengthening from lag 10 yrs prior an amoc maximum opposite relationship is found with the nao for both summer and winter seasons despite negative lags nao at that time is consistent with the atmospheric response through teleconnection to the northward shift intensification of the inter tropical convergence zone in link to the ongoing warming of tropical north atlantic basin due to amoc rise amv build up nao acts as a positive feedback for the full development of the model amv through surface fluxes but at the same time prepares its termination through negative retroaction on amoc relationship between eap and amoc is also present in summer from lags 30 10 yrs while winter eap is favored around the amv peak based on additional atmospheric forced experiments both are interpreted as the local seasonal dependent atmospheric response to warmer north atlantic finally advection of fresher water from the tropical basin created by local atmosphere ocean anomalous circulation on one hand and from the arctic on the other hand due to large scale sea ice melting leads to decrease of density in the spg and contributes terminating the model amoc amv events all together the combined effects of nao and eap their intertwined seasonal forcing forced role upon by the ocean and the primary role of salinity anomalies associated with oceanic dynamical changes acting as an integrator are responsible in cnrm cm5 for an irregular and damped mode of variability for amoc amv that takes about 35 40 15 20 years to build up dissipate

tropical pacific atlantic ocean interactions at multi decadal time scales analysis of sea surface temperature sst observations suggests a pan oceanic interaction between the tropical pacific and the atlantic ocean at multi decadal time scales such that periods of anomalously high ssts in the tropical pacific are followed by a basin wide sst dipole in the atlantic ocean with a time delay of a few decades the sst anomaly structure in the atlantic ocean is reminscent of variations in the north atlantic thermohaline circulation the two ocean basins are linked through an atmospheric bridge involving anomalous fresh water fluxes based on the observational findings the atlantic thermohaline circulation may strengthen during the next decades in response to the strong decades long increase in tropical pacific sst which will have strong impacts on the climates of north america and europe through changes in the north atlantic oscillation nao

the north atlantic oscillation and oceanic precipitation variability global north atlantic oscillation nao oceanic precipitation features in the latter half of the twentieth century are documented based on the intercomparison of multiple state of the art precipitation datasets and the analysis of the nao atmospheric circulation and sst anomalies most prominent precipitation anomalies occur over the ocean in the north atlantic where in winter a quadrupole like pattern is found with centers in the western tropical atlantic sub tropical atlantic high latitude eastern atlantic and over the labrador sea the extent of the sub tropical and high latitude center and the amount of explained variance over 50 are quite remarkable however the tropical atlantic center is probably the most intriguing feature of this pattern apparently linking the nao with itcz variability in summer the pattern is tripole like with centers in the eastern mediterranean sea the north sea baltic sea and in the sub polar atlantic in the eastern indian ocean the correlation is positive in winter and negative in summer with some link to enso variability the sensitivity of these patterns to the choice of the nao index is minor in winter while quite important in summer interannual nao precipitation anomalies have driven similar fresh water variations in these key regions in the sub tropical and high latitude atlantic in winter precipitation anomalies have been roughly 15 and 10 of climatology per unit change of the nao respectively decadal changes of the nao during the last 50 years have also influenced precipitation and fresh water flux at these time scales with values lower higher than usual in the high latitude eastern north atlantic labrador sea in the 1960s and the late 1970s and an opposite situation since the early 1980s in summer the north sea baltic region has been drier than usual during the period 1965 1975 when the nao was generally positive

salinity driven thermocline transients in a wind and thermohaline forced isopycnic coordinate model of the north atlantic abstract an isopycnic coordinate oceanic circulation model formulated with the aim of simulating thermodynamically and mechanically driven flow in realistic basins is presented special emphasis is placed on the handling of diabatic surface processes and on thermocline ventilation the model performance is illustrated by a 30 year spinup run with coarse horizontal resolution 2 mesh in a domain with north atlantic topography extending from 10 to 60 n latitude the vertical structure encompasses 10 isopycnic layers in steps of 0 2 units capped by a thermodynamically active mixed layer from an initially isohaline state with isopycnals prescribed by zonally averaged climatology the model is forced by seasonally varying wind stress radiative and freshwater fluxes and by a thermal relaxation process at the surface after a mechanical spinup time of about 15 years a quasi stationary pattern of mean circulation and annual variability ensues characterized by pronounced subtropical mode water formation

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

open ocean convection in the irminger sea open ocean deep convection is known to occur in a very few locations in the present climate convection is important for the ventilation of the oceans and for the operation of the meridional overturning circulation using data from ships and profiling floats we present evidence for the occurrence of convection in the irminger sea of the north atlantic south east of greenland confirmation of this convective site in the north atlantic will influence our understanding of the connection of the atmosphere to the ocean depths and of the mechanisms of climate variability

organic geochemistry and kinetics for natural gas generation from mudstone and coal in the xihu sag east china sea shelf basin china abstract a comparative study on organic geochemistry and kinetics was performed on two representative coal measure mudstone and coal samples of the eocene pinghu formation in the xihu sag east china sea shelf basin china gas chromatography mass spectrometry analysis of the aliphatic fractions of the source rock extracts was performed to characterize the maturity depositional conditions and source materials in the samples the kerogens isolated from the mudstone and coal were pyrolyzed in a closed system at two heating rates to determine the kinetics for natural gas generation and the results were extrapolated to geological conditions biomarker assemblages show that the mudstone type iii kerogen and coal type ii iii kerogen contain predominantly terrigenous source materials with the effect of microbial reworking and were deposited under oxic conditions within an unstratified water column the mudstone has slightly more algal material input and less oxic conditions during deposition than the coal the rocks are at the early mature stage but the coal is slightly more mature than the mudstone the activation energies for natural gas generation from the mudstone and coal distribute mainly in the range of 47 62 kcal mol and 50 69 kcal mol with a frequency factor of 2 0 1011 s 1 and 1 0 1013 s 1 respectively the lower activation energies for the mudstone than the coal suggests an earlier onset of natural generation assuming a constant burial heating rate of 3 c ma for the calculated activation energy distributions the calculated temperature for a given transformation ratio can differ by 60 c indicating varying kinetic stability due to different kerogen composition and structure this significant and unexpected difference suggests that more attentions should be paid to the kinetic heterogeneity of coal bearing source rocks and we must be particularly cautious about selecting appropriate kinetic models in petroleum system modeling

melt inclusions in pegmatite quartz complete miscibility between silicate melts and hydrous fluids at low pressure fluorine boron and phosphorus rich pegmatites of the variscan ehrenfriedersdorf complex crystallized over a temperature range from about 700 to 500 c at a pressure of about 1 kbar pegmatite quartz crystals continuously trapped two different types of melt inclusions during cooling and growth a silicate rich h2o poor melt and a silicate poor h2o rich melt both melts were simultaneously trapped on the solvus boundaries of the silicate fluorine boron phosphorus water system the partially crystallized melt inclusions were rehomogenized at 1 kbar between 500 and 712 c in steps of 50 c by conventional rapid quench hydrothermal experiments glasses of completely rehomogenized inclusions were analyzed for h2o by raman spectroscopy and for major and some trace elements by emp electron microprobe both types of melt inclusions define a solvus boundary in an xh2o t pseudobinary system at 500 c the silicate rich melt contains about 2 5 wt h2o and the conjugate water rich melt about 47 wt h2o the solvus closes rapidly with increasing temperature at 650 c the water contents are about 10 and 32 wt respectively complete miscibility is attained at the critical point 712 c and 21 5 wt h2o many pegmatites show high concentrations of f b and p this is particularly true for those pegmatites associated with highly evolved peraluminous granites the presence of these elements dramatically reduces the critical pressure for fluid melt systems at shallow intrusion levels at t 720 c water is infinitely soluble in a f b and p rich melt simple cooling induces a separation into two coexisting melts accompanied with strong element fractionation on the water rich side of the solvus very volatile rich melts are produced that have vastly different physical properties as compared to normal silicate melts the density viscosity diffusivity and mobility of such hyper aqueous melts under these conditions are more comparable to an aqueous fluid

a 20 year coupled ocean sea ice atmosphere variability mode in the north atlantic in an aogcm in order to understand potential predictability of the ocean and climate at the decadal time scales it is crucial to improve our understanding of internal variability at this time scale here we describe a 20 year mode of variability found in the north atlantic in a 1 000 year pre industrial simulation of the ipsl cm5a lr climate model this mode involves the propagation of near surface temperature and salinity anomalies along the southern branch of the subpolar gyre leading to anomalous sea ice melting in the nordic seas which then forces sea level pressure anomalies through anomalous surface atmospheric temperatures the wind stress associated to this atmospheric structure influences the strength of the east greenland current across the denmark strait which in turn induces near surface temperature and salinity anomalies of opposite sign at the entrance of the labrador sea this starts the second half of the cycle after approximatively 10 years the time scale of the cycle is thus essentially set by advection of tracers along the southern branch of the subpolar gyre and by the time needed for anomalous east greenland current to accumulate heat and freshwater anomalies at the entrance of the labrador sea the atlantic meridional overturning circulation amoc does not play a dominant role in the mode that is confined in the subpolar north atlantic but it also has a 20 year preferred timescale this is due to the influence of the propagating salinity anomalies on the oceanic deep convection the existence of this preferred timescale has important implications in terms of potential predictability of the north atlantic climate in the model although its realism remains questionable and is discussed

simulated variability of the atlantic meridional overturning circulation to examine the multi annual to decadal scale variability of the atlantic meridional overturning circulation amoc we conducted a four member ensemble with a daily reanalysis forced medium resolution global version of the isopycnic coordinate ocean model micom and a 300 years integration with the fully coupled bergen climate model bcm the simulations of the amoc with both model systems yield a long term mean value of 18 sv and decadal variability with an amplitude of 1 3 sv the power spectrum of the inter annual to decadal scale variability of the amoc in bcm generally follows the theoretical red noise spectrum with indications of increased power near the 20 years period comparison with observational proxy indices for the amoc e g the thickness of the labrador sea water the strength of the baroclinic gyre circulation in the north atlantic ocean and the surface temperature anomalies along the mean path of the gulf stream shows similar trends and phasing of the variability indicating that the simulated amoc variability is robust and real mixing indices have been constructed for the labrador the irminger and the greenland iceland norwegian gin seas while convective mixing in the labrador and the gin seas are in opposite phase and linked to the nao as observations suggest the convective mixing in the irminger sea is in phase with or leads the labrador sea newly formed deep water is seen as a slow anomalous cold and fresh plume flowing southward along the western continental slope of the atlantic ocean with a return flow of warm and saline water on the surface in addition fast travelling topographically trapped waves propagate southward along the continental slope towards equator where they go east and continue along the eastern rim of the atlantic for both types of experiments the northern hemisphere sea level pressure and 2 m temperature anomaly patterns computed based on the difference between climate states with strong and weak amoc yields a nao like pattern with intensified icelandic low and azores high and a warming of 0 25 0 5 c of the central north atlantic sea surface temperature sst the reanalysis forced simulations indicate a coupling between the labrador sea water production rate and an equatorial atlantic sst index in accordance with observations this coupling is not identified in the coupled simulation

multidecadal climate variability in the greenland sea and surrounding regions a coupled model simulation pronounced oscillations of ocean temperature and salinity occur in the greenland sea in a 2000 year integration of a coupled ocean atmosphere model the oscillations involving both the surface and subsurface ocean layers have a timescale of approximately 40 80 years and are associated with fluctuations in the inten sity of the east greenland current the greenland sea temperature and salinity variations are preceded by large scale changes in near surface salinity in the arctic which appear to propagate out of the arctic through the east greenland current these anomalies then propagate around the subpolar gyre into the labrador sea and the central north atlantic these oscillations are coherent with previously identified multi decadal fluctuations in the intensity of the north atlantic thermohaline circula tion the oscillations in the g eenland sea are related to atmospheric variability negative cold anomalies of surface air temperature are associated with negative cold sea surface temperature sst anomalies in the greenland sea with amplitudes up to 2oc near green land declining to several tenths of a degree c over north western europe the c01d sst anomalies and intensified east greenland current are also associated with enhanced northerly winds over the greenland sea

what is the thermohaline circulation the term thermohaline circulation is widely used in the context of past and future climate change in his perspective wunsch argues that there are many different and inconsistent definitions for this term he defines ocean circulation in terms of mass fluxes which are largely driven by surface forces such as wind and tides and argues that thermohaline circulation should only refer to the separate transport of heat and salinity in the ocean

interannual to interdecadal variability of sea surface salinity in the atlantic and its link to the atmosphere in a coupled model 1 the interannual to interdecadal variability of sea surface salinity sss in the atlantic is investigated using 200 years of a control simulation of the bergen climate model after verifying that the model behaves realistically we show that most centers of sss variability are located near the mouths of the main rivers of the basin this variability is due primarily to anomalous runoff except in the st lawrence area and to anomalous ekman and geostrophic currents while fluctuations in the freshwater flux play a somewhat lesser role away from the coast sss variability is strong in the northern tropics due largely to anomalous advection and freshwater exchanges regression analysis and a lagrangian technique show that the sss anomalies are advected by the mean oceanic circulation and can be followed along the gyres for several years the link between sss anomalies and the dominant modes of variability of the atmosphere is also investigated the sss response to the north atlantic oscillation nao is dominated by relatively small scales that are forced by anomalous ekman currents but the relative influence of the large scale freshwater fluxes increases at long timescales the nao induced sss anomalies are also strongly advected and distorted by the mean currents so that their pattern at the interannual timescale only reflects in part that of the atmospheric forcing the link between sss anomalies and the east atlantic pattern is similar

observations inferences and mechanisms of the atlantic meridional overturning circulation a review this is a review about the atlantic meridional overturning circulation amoc its mean structure temporal variability controlling mechanisms and role in the coupled climate system the amoc plays a central role in climate through its heat and freshwater transports northward ocean heat transport achieved by the amoc is responsible for the relative warmth of the northern hemisphere compared to the southern hemisphere and is thought to play a role in setting the mean position of the intertropical convergence zone north of the equator the amoc is a key means by which heat anomalies are sequestered into the ocean s interior and thus modulates the trajectory of climate change fluctuations in the amoc have been linked to low frequency variability of atlantic sea surface temperatures with a host of implications for climate variability over surrounding landmasses on intra annual timescales variability in amoc is large and primarily reflects the response to local wind forcing meridional coherence of anomalies is limited to that of the wind field on interannual to decadal timescales amoc changes are primarily geostrophic and related to buoyancy anomalies on the western boundary a pacemaker region for decadal amoc changes is located in a western transition zone along the boundary between the subtropical and subpolar gyres decadal amoc anomalies are communicated meridionally from this region amoc observations as well as the expanded ocean observational network provided by the argo array and satellite altimetry are inspiring efforts to develop decadal predictability systems using coupled atmosphere ocean models initialized by ocean data

first reported sedimentary occurrence of berlinite alpo4 in phosphate bearing sediments from cioclovina cave romania comment in a recent work onac and white 2003 reported on berlinite but also chlorellestadite and churchite from the bivouac room cioclovina cave romania our analyses of materials collected from this site failed to identify berlinite chlorellestadite or churchite due to the nature of the samples collected from the bat guano deposit at cioclovina many possible sources of confusion can occur for example separates from a mixture of taranakite quartz and minor illite could give the same analytical results as those reported by onac and white 2003 for berlinite for this reason we consider that the occurrence of berlinite at cioclovina as well as the occurrence of other exotic species such as chlorellestadite or churchite is not well enough substantiated and their report must be regarded with caution arguments to support this point of view are problems identified with the analytical techniques empa xrd the failure of the experimental synthesis of berlinite in dry conditions at atmospheric pressure and the geochemical context from cioclovina

organic geochemistry and organic petrology of a potential source rock of early eocene age in the beaufort mackenzie basin abstract the biological marker compounds 17 h and 17 h 23 28 bisnorlupane have been identified in a coaly interval at about 3300 3320 m depth within the lower taglu sequence early eocene in the immiugak a 06 well in the beaufort mackenzie basin these biomarkers were previously only known to occur in the lower part of the richards formation and were thus used to infer that the richards was the source for most of the tertiary oils and condensates in the basin the discovery of bisnorlupanes in older much more organic rich rocks indicates that the previous oil source rock correlations may not have been correct and that the coals in the lower taglu sequence are likely the dominant effective source rock especially for the paleocene and early eocene reservoirs in the southern part of the mackenzie delta petrographic and rock eval analyses indicate that the lower taglu sequence coaly section should be mainly a source for gas but with some potential to expel liquids the level of thermal maturity inferred from rock eval tmax 432 438 c equivalent to about 0 65 0 75 ro vitrinite is slightly higher than that inferred from the measured reflectance fluorescence and foraminiferal colouration index which all indicate that the maturity at 3300 m is about 0 60 0 65 ro vitrinite equivalent at the gulf et al immiugak a 06 well site

deep convection in the irminger sea forced by the greenland tip jet open ocean deep convection one of the processes by which deep waters of the world s oceans are formed is restricted to a small number of locations for example the mediterranean and labrador seas recently the southwest irminger sea has been suggested as an additional location for open ocean deep convection the deep water formed in the irminger sea has the characteristic temperature and salinity of the water mass that fills the mid depth north atlantic ocean which had been believed to be formed entirely in the labrador basin here we show that the most likely cause of the convection in the irminger sea is a low level atmospheric jet known as the greenland tip jet which forms periodically in the lee of cape farewell greenland and is associated with elevated heat flux and strong wind stress curl using a history of tip jet events derived from meteorological land station data and a regional oceanic numerical model we demonstrate that deep convection can occur in this region when the north atlantic oscillation index is high which is consistent with observations this mechanism of convection in the irminger sea differs significantly from those known to operate in the labrador and mediterranean seas

interdecadal variations of the thermohaline circulation in a coupled ocean atmosphere model abstract a fully coupled ocean atmosphere model is shown to have irregular oscillations of the thermohaline circulation in the north atlantic ocean with a time scale of approximately 50 years the irregular oscillation appears to be driven by density anomalies in the sinking region of the thermohaline circulation approximately 52 n to 72 n combined with much smaller density anomalies of opposite sign in the broad rising region the spatial pattern of see surface temperature anomalies associated with this irregular oscillation bears an encouraging resemblance to a pattern of observed interdecadal variability in the north atlantic the anomalies of sea surface temperature induce model surface air temperature anomalies over the northern north atlantic arctic and northwestern europe

hydrocarbon geochemistry of the puget sound region ii sedimentary diterpenoid steroid and triterpenoid hydrocarbons cyclic components of the aliphatic hydrocarbon mixtures extracted from puget sound sediment cores include a suite of c19 and c20 diterpenoid hydrocarbons of which fichtelite sandaracopimaradiene and isopimaradiene have been identified although apparently also derived from vascular plants these diterpenoid hydrocarbons have relative abundances distinctly different from the co existing plant wax n alkane suite five c27 c28 and c29 diasteranes and four c29 c30 and c31 17 h 21 h hopanes occur in relatively constant proportion as components of a highly weathered fossil hydrocarbon assemblage these chromatographically resolved cycloalkanes along with the strongly covarying unresolved complex mixture have been introduced to puget sound sediments from adjacent urban centres at increasing levels over the last 100 yr in the absence of any major oil spill naturally occurring triterpenoid hydrocarbons including hop 22 29 ene diploptene are also present a new group of c30 polyenes has been detected which contains compounds apparently structurally related to a co existing bicyclic c25 diene and to c20 and c25 acyclic multibranched hydrocarbons described in a previous paper barrick et al 1980

cyclic terpenoids of contemporary resinous plant detritus and of fossil woods ambers and coals abstract cyclic terpenoids present in the solvent extractable material of fossil woods ambers and brown coals have been analyzed the sample series chosen consisted of wood remains preserved in holocene to jurassic sediments and a set of of ambers from the philippines copalite israel canada and dominican republic the brown coals selected were from the fortuna garsdorf mine and miocene formations on fiji the fossil wood extracts contained dominant diterpenoid or sesquiterpenoid skeletons and aromatized species were present at high concentrations with a major amount of two ring aromatic compounds tricyclic diterpenoids were the predominant compounds in the ambers aromatized derivatives were the major components consisting of one or two aromatic ring species with the abietane and occasionally pimarane skeletons the saturated structures were comprised primarily of the abietane and pimarane skeletons having from three to five carbon c1 c2 etc substituents kaurane and phyllocladane isomers were present in only minor amounts bicyclic sesquiterpenoids as saturated and partial or fully aromatized forms were also common in these samples but only traces of sesterterpenoids and triterpenoid derivatives were found the brown coal extracts were composed of major amounts of one and two ring aromatized terpenoids with a greater proportion of triterpenoid derivatives than in the case of the woods and ambers this was especially noticeable for the german coal where the triterpenoids were predominant open c ring aromatized structures were also present in this coal steroid compounds were not detectable but some hopanes were found as minor components in the german brown coal an overview of the skeletal structure classes identified in each sample as well as the general mass spectrometric characteristics of the unknown compounds are included in the present paper it can be concluded from these structural distributions that aromatization is the main process for the transformation of terrestrial cyclic terpenoids during diagenesis constituting a general pathway for all terpenoids

diterpanes triterpanes steranes and aromatic hydrocarbons in natural bitumens and pyrolysates from different mimic coals abstract there is a significant difference in the distribution of terpanes in natural bitumen extracted from four coals identified as rocky mountain coal rmc australian gippsland latrobe eocene coal gec australian gippsland latrobe cretaceous coal gcc and texas wilcox lignite wl whereas pentacyclic triterpanes are dominant in gec gcc and wl diterpanes strongly predominate in the bitumen of rmc this indicates that resin is a more important constituent of rmc than in the other coals and releases the diterpenoids at an early stage of diagenesis furthermore the composition of diterpanes is also different among these coals for example tricyclic diterpanes are the only diterpanes present in rmc whereas tetracyclic and tricyclic diterpanes are both present in gec and gcc and tetracyclic diterpanes are most abundant in gec however diterpanes are nearly absent in wl surprisingly the diterpenoid content is negligible in the pyrolysates of all coals the sterane and triterpane distributions in the natural bitumen of coals are very different from those in pyrolysates c 31 22r hopane predominates in the m z 191 mass fragmentograms of the natural bitumens whereas a homologous series of hopanes c 27 c 35 except c 28 is present in the coal pyrolysates c 29 steranes dominate in all of the coal bitumens as well as pyrolysates c 27 steranes are absent in the natural bitumen but are generated in pyrolysates during lengthy heating of coal kerogen this indicates that formation of secondary steranes occurs by cracking the side chain c 29 monoaromatic steroid hydrocarbons are abundant in the natural bitumen of the four coals the m z 253 distribution is similar for gec rmc and wl but it differs from the more mature ggc which has a lower content of 20r of both 5 and 5 c 29 ma steroids triaromatic steroid hydrocarbons are only present in gcc whereas significant amounts of tetra and triaromatic triterpenoid hydrocarbons are present in the other three coals gec rmc and wl the ratio of benzo e pyrene perylene may be potentially useful as a maturity parameter because the amount of benzo e pyrene increases with thermal stress whereas perylene decreases with heating time benzohopanes are widely present in four humic coals but become unstable after 10 h heating at 300 c

a two level wind and buoyancy driven thermocline model abstract a simple two level model is designed to simulate the thermocline equations applicable for large scale steady oceanic flow the model serves two functions first it replaces problems with the interpretation of slablike dynamics e g luyten et al 1983 by using continuously horizontally varying buoyancy but at the cost of reducing the vertical resolution drastically the equations used are geostrophy plus a small linear drag to close a stommel like western boundary layer mass conservation and buoyancy conservation with a small but necessary horizontal diffusion inclusion of vertical diffusion has little effect the ocean is driven by an ekman layer whose functions are to provide a given surface input of mass through ekman pumping and buoyancy through a specified buoyancy in the ekman layer i e to maintain the same boundary conditions as in classical thermocline studies sidewall conditions are not well understood and are almost certainly over specified in this formulation s

local and remote impacts of a tropical atlantic salinity anomaly the climatic impacts of an enhanced evaporation prescribed during 50 years in the tropical atlantic are investigated in a coupled ocean atmosphere general circulation model locally the salinity increase leads to a rapid deepening and cooling of the surface mixed layer this induces a deepening of the equatorial undercurrent and an intensification of the south equatorial current a remote atmospheric response to the tropical atlantic perturbation is detected in the north atlantic sector after ten years it has the form of a robust wave like tropospheric perturbation seemingly excited by the weakening of atmospheric deep convection over the amazonian basin meanwhile the salt anomaly is carried northward by the mean oceanic circulation it is traced up to the convection sites and then on its return path at depth towards lower latitudes consistent with the density increase deep convection is enhanced after the arrival of the salt anomaly and the atlantic meridional overturning circulation amoc intensifies about 20 years after the beginning of the perturbation the adjustment of the tropical atlantic to the amoc intensification then modifies its initial response to the freshwater forcing leading to a weaker cooling in the northern tropical atlantic than in the southern tropical atlantic a slight northward shift of the tropical atlantic precipitation pattern and an intensification of the north brazil current on the other hand no significant anomalous precipitations are found in the pacific the initial remote atmospheric response is also modulated by an nao like response to the amoc intensification

interdecadal north atlantic meridional overturning circulation variability in ec earth the atlantic meridional overturning circulation amoc in a 600 years pre industrial run of the newly developed ec earth model features marked interdecadal variability with a dominant time scale of 50 60 years an oscillation of approximately 2 sverdrup 1 sv 106 m3 s 1 is identified which manifests itself as a monopole causing the overturning to simultaneously strengthen weaken and deepen shallow as a whole eight years before the amoc peaks density in the labrador irminger sea region reaches a maximum triggering deep water formation this density change is caused by a counterclockwise advection of temperature and salinity anomalies at lower latitudes which we relate to the north south excursions of the subpolar subtropical gyre boundary and variations in strength and position of the subpolar gyre and the north atlantic current the amoc fluctuations are not directly forced by the atmosphere but occur in a delayed response of the ocean to forcing by the north atlantic oscillation which initiates intergyre gyre fluctuations associated with the amoc is a 60 year sea surface temperature variability in the atlantic with a pattern and timescale showing similarities with the real world atlantic multidecadal variability this good agreement with observations lends a certain degree of credibility that the mechanism that is described in this article could be seen as representative of the real climate system

variability of the simulated meridional heat transport in the north atlantic for the period 1951 1993 a 43 year ocean model simulation for the period 1951 1993 is analyzed with a focus on the meridional heat transport mht as a proxy for the strength of meridional overturning cell moc at 25 n the surface heat flux forcing associated with the north atlantic oscillation nao pattern is related to the variability in mht both on interannual and longer timescales the manifestation of the interannual and decadal oceanic response to nao is nonlocal as evidenced by the concentrated heat content and sea level variability at the gulf stream and north atlantic current regions and shown by the comparison of the model sea level variability to the altimeter data between low mht years in mid 1980s and high mht years in early 1990s the same area is singled out by empirical orthogonal function analysis in the leading mode of the sea level mht and time series of the leading sea level mode are highly correlated which reflects the importance of the moc in determining the variability of the heat content of the whole basin also the model suggests that the mht moc has entered a very strong phase since the mid 1980s and this trend has continued up to the end of 1993 this behavior follows the general trend in the nao index

a study of the interaction of the north atlantic oscillation with ocean circulation observed patterns of wind stress curl and air sea heat flux associated with the north atlantic oscillation nao are used to discuss the response of ocean gyres and thermohaline circulation to nao forcing and their possible feedback on the nao the observations motivate and are interpreted in the framework of a simple mathematical model that couples ekman layers ocean gyres and thermohaline circulation to the atmospheric jet stream meridional shifts in the zero wind stress curl line are invoked to drive anomalies in ocean gyres and north south dipoles in air sea flux drive anomalous thermohaline circulation both gyres and thermohaline circulation play a role in modulating sea surface temperature anomalies and hence through air sea interaction the overlying jet stream the model which can be expressed in the form of a delayed oscillator with ocean gyres and or thermohaline circulation providing the delay identifies key nondimensional parameters that control whether the ocean responds passively to nao forcing or actively couples it suggests that both thermohaline circulation and ocean gyres can play a role in coupled interactions on decadal timescales

immature oil and condensate modification of hydrocarbon generation model for terrestrial organic matter petroleum has been found in canadian frontier basins in reservoirs which have undergone low levels of thermal alteration vitrinite reflectance 0 6 ro paraffin indices stable carbon and hydrogen isotope contents pristane to nc17 ratios and diterpenoid biologic markers have been used to assess the level of maturity of the hydrocarbons in the reservoir independently of the level of maturity of the reservoir itself and of the surrounding shale units in the tertiary of the beaufort mackenzie basin naphthenic oils and condensates have been generated from terrestrially derived organic matter in source rocks juxtaposed with the reservoir at reflectance levels of 0 4 to 0 6 ro however condensates discovered in reservoirs which are th rmally immature on the labrador shelf have undergone extensive vertical migration and can be classed as conventional mature to overmature condensates hydrocarbons discovered in the lower cretaceous of the beaufort mackenzie basin and also those of the scotian shelf are more or less in place in that they are at a level of thermal alteration about equivalent to that of the reservoirs in which they are trapped the source for the early oils and condensates is considered to be resinite occurring dispersed in coal fragments the proportion of resinite liptinite and vitrinite in the organic matter of terrestrial source rocks strongly controls both the level of thermal alteration necessary for the section to function as an effective source rock and the ultimate product gas oil or condensate which will be generated

the formation of labrador sea water part i large scale processes abstract data obtained in the western labrador sea during march 1976 by hudson are analysed to show that new labrador sea water was being formed at this time on the basis of hydrographic and moored current meter data it is hypothesized that a 200 km scale cyclonic gyre forms in winter in the western labrador sea and that this gyre retains the developing deep mixed layers in this general area long enough for the transformation to labrador sea water to take place using a model it is demonstrated that water columns found along the western boundary of the labrador sea can be modified by cooling evaporation and mixing to form deep mixed layers with the properties of labrador sea water approximately 105 km3 of new labrador sea water was formed in 1976 an estimate that is consistent with earlier estimates of mean annual production rates this water 2 9 c 34 84 is some 0 6 c cooler and 0 06 fresher than that defined by lazier 1973 from his data collected in 1966 the variation of labrador sea water

geochemical characteristics of oils from the sirikit oilfield phisanulok basin thailand abstract twelve oils from the sirikit field of the phisanulok basin thailand have been examined to determine the nature of their source materials depositional environment relative maturity and extent of biodegradation the geochemical analyses performed in this study suggested that all of the oils were derived from similar types of organic source matter consisting of a mixture of bacterial algal and higher plant material the sterane contents of the oils were relatively low and conventional maturity parameters based on sterane ratios suggested the oils were relatively immature extensive strike slip faults in the phisanulok basin may have led to rapid burial of the sediments during deposition preventing these ratios from having attained their equilibrium ratios

geochemical characteristics of tertiary coal bearing source rocks in xihu depression east china sea basin abstract this study aims at investigating hydrocarbon generation potential and biological organic source for the tertiary coal bearing source rocks of pinghu formation middle upper eocene in xihu depression east china sea shelf basin another goal is to differentiate coal and mudstone with respect to their geochemical properties the coal bearing sequence has a variable organofacies and is mainly gas prone the coals and carbonaceous mudstones in comparison with mudstones have a higher liquid hydrocarbon generation potential as reflected by evidently higher hi values averaging 286 mg hc g c and h c atomic ratios round 0 9 the molecular composition in the coal bearing sequence is commonly characterized by unusually abundant diterpenoid alkanes dominant c29 sterane over c27 and c28 homologues and high amount of terrigenous related aromatic biomarkers such as retene cadalene and 1 7 dimethylphenanthrene indicating a predominantly terrigenous organic source the source rocks show high pr ph ratios ranging mostly from 3 5 to 8 5 and low mdbts mdbfs ratios

links between the southern annular mode and the atlantic meridional overturning circulation in a climate model abstract the links between the atmospheric southern annular mode sam the southern ocean and the atlantic meridional overturning circulation amoc at interannual to multidecadal time scales are investigated in a 500 yr control integration of the l institut pierre simon laplace coupled model version 4 ipsl cm4 climate model the antarctic circumpolar current as described by its transport through the drake passage is well correlated with the sam at the yearly time scale reflecting that an intensification of the westerlies south of 45 s leads to its acceleration also in phase with a positive sam the global meridional overturning circulation is modified in the southern hemisphere primarily reflecting a forced barotropic response in the model the amoc and the sam are linked at several time scales an intensification of the amoc lags a positive sam by about 8 yr this is due to a correlation between the sam and the atmospheric circulation in the northern north atlantic that reflects a symmetric e

multidecadal ocean temperature and salinity variability in the tropical north atlantic linking with the amo amoc and subtropical cell abstractthe atlantic multidecadal oscillation amo is characterized by the sea surface warming cooling of the entire north atlantic during its warm cold phase both observations and most of the phase 5 of the coupled model intercomparison project cmip5 models also show that the warm cold phase of the amo is associated with a surface warming cooling and a subsurface cooling warming in the tropical north atlantic tna it is further shown that the warm phase of the amo corresponds to a strengthening of the atlantic meridional overturning circulation amoc and a weakening of the atlantic subtropical cell stc which both induce an anomalous northward current in the tna subsurface ocean because the mean meridional temperature gradient of the subsurface ocean is positive because of the temperature dome around 9 n the advection by the anomalous northward current cools the tna subsurface ocean during the warm phase of the amo the opposite is true during the cold phase of the amo it is conclud

atlantic multidecadal oceanic variability and its influence on the atmosphere in a climate model the mechanisms controlling the decadal to multidecadal variability of the atlantic meridional overturning circulation moc and its influence on the atmosphere are investigated using a control simulation with the ipsl cm4 climate model the multidecadal fluctuations of the moc are mostly driven by deep convection in the subpolar gyre which occurs south of iceland in the model the latter is primarily influenced by the anomalous advection of salinity due to changes in the east atlantic pattern eap which is the second mode of atmospheric variability in the north atlantic region the north atlantic oscillation is the dominant mode but it plays a secondary role in the moc fluctuations during summer the moc variability is shown to have a significant impact on the atmosphere in the north atlantic european sector the moc influence is due to an interhemispheric sea surface temperature sst anomaly with opposite signs in the two hemispheres but largest amplitude in the northern one the sst pattern driven by the moc mostly resembles the model atlantic multidecadal oscillation amo and bears some similarity with the observed one it is shown that the amo reflects both the moc influence and the local atmospheric forcing hence the moc influence on climate is best detected using lagged relations between climatic fields the atmospheric response resembles the eap in a phase that might induce a weak positive feedback on the moc

decadal timescale changes of the atlantic overturning circulation and climate in a coupled climate model with a hybrid coordinate ocean component a wide range of statistical tools is used to investigate the decadal variability of the atlantic meridional overturning circulation amoc and associated key variables in a climate model chime coupled hadley isopycnic model experiment which features a novel ocean component chime is as similar as possible to the 3rd hadley centre coupled model hadcm3 with the important exception that its ocean component is based on a hybrid vertical coordinate power spectral analysis reveals enhanced amoc variability for periods in the range 15 30 years strong amoc conditions are associated with 1 a sea surface temperature sst anomaly pattern reminiscent of the atlantic multi decadal oscillation amo response but associated with variations in a northern tropical subtropical gradient 2 a surface air temperature anomaly pattern closely linked to sst 3 a positive north atlantic oscillation nao like pattern 4 a northward shift of the intertropical convergence zone the primary mode of amoc variability is associated with decadal changes in the labrador sea and the greenland iceland norwegian gin seas in both cases linked to the tropical activity about 15 years earlier these decadal changes are controlled by the low frequency nao that may be associated with a rapid atmospheric teleconnection from the tropics to the extratropics poleward advection of salinity anomalies in the mixed layer also leads to amoc changes that are linked to processes in the labrador sea a secondary mode of amoc variability is associated with interannual changes in the labrador and gin seas through the impact of the nao on local surface density

re examination of berlinite alpo4 from the cioclovina cave romania berlinite is a mineral indicative of high temperature formation and therefore it would not be expected to be present in a sedimentary environment in this study we review the characteristics of a berlinite bearing deposit and present a single crystal structure investigation based on x ray data the refinement converged at r 1 f 0 0276 wr 2 f 2 0 0657 for 677 reflections 2 mo k 70 and 31 variables in space group p 3 1 21 a 4 9458 10 c 10 9526 20 a v 232 0 a 3 z 3 alpo 4 the average t o bond distances within the two crystallographically unique t o 4 tetrahedra are 1 734 and 1 526 a respectively from the scattering power at these t sites and the stereochemistry the presence of an alo 4 tetrahedron linked to a po 4 tetrahedron is established consequently the sample from cioclovina cave is verified as alpo 4 modification berlinite reconfirming the first description of this mineral from a sedimentary occurrence which underwent an obvious natural heating process

tropical atlantic sea surface temperature variability and its relation to el nino southern oscillation past analyses of tropical atlantic sea surface temperature variability have suggested a dipole behavior between the northern and southern tropics across the intertropical convergence zone itcz by analyzing an improved 43 year 1950 1992 record of sst smith et al 1996 and other data derived from the comprehensive ocean atmosphere data set coads it is shown that the regions north and south of the itcz are statistically independent of each other at the seasonal to interannual timescales dominating the data confirming the conclusions of houghton and tourre 1992 some dipole behavior does develop weakly during the boreal spring season when there is a tendency for sst anomaly west of angola to be opposite of that in the tropical north atlantic it is further shown that tropical atlantic sst variability is corre lated with pacific e1 nifio southern oscillation enso variability in several regions the ma jor region affected is the north atlantic area of ne trades west of 40ow along 10on 20on and extending into the caribbean there about 50 80 of the anomalous sst variability is associ ated with the pacific enso with atlantic warmings occurring 4 5 months after the mature phases of pacific warm events an analysis of local surface flux fields derived from coads data shows that the enso related atlantic warmings occur as a result of reductions in the surface ne trade wind speeds which in turn reduce latent and sensible heat losses over the region in ques tion as well as cooling due to entrainment this enso connection is best developed during the boreal spring following the most frequent season of maximum enso anomalies in the pacific a region of secondary covariability with enso occurs along the northern edge of the mean itcz position and appears to be associated with northward migrations of the itcz when the north at lantic warmings occur although easterly winds are intensified in the western equatorial atlantic in response to pacific warm events they do not produce strong local changes in sst contrary to expectations from studies based on equatorial dynamics these teleconnected wind anomalies do not give rise to significant correlations of sst in the gulf of guinea with the pacific enso as the teleconnection sequence matures strong se trades at low southern latitudes follow the de velopment of the north atlantic sst anomaly and precede by several months the appearance of weak negative sst anomalies off angola and stronger positive anomalies extending eastward from southern brazil along 15o 30os

open ocean convection observations theory and models we review what is known about the convective process in the open ocean in which the properties of large volumes of water are changed by intermittent deep reaching convection triggered by winter storms observational laboratory and modeling studies reveal a fascinating and complex interplay of convective and geostrophic scales the large scale circulation of the ocean and the prevailing meteorology two aspects make ocean convection interesting from a theoretical point of view first the timescales of the convective process in the ocean are sufficiently long that it may be modified by the earth s rotation second the convective process is localized in space so that vertical buoyancy transfer by upright convection can give way to slantwise transfer by baroclinic instability moreover the convective and geostrophic scales are not very disparate from one another detailed observations of the process in the labrador greenland and mediterranean seas are described which were made possible by new observing technology when interpreted in terms of underlying dynamics and theory and the context provided by laboratory and numerical experiments of rotating convection great progress in our description and understanding of the processes at work is being made

sesquiterpanes diterpanes and other higher terpanes in oils from the taranaki basin of new zealand abstract the bi tri and tetracyclic terpenoids in crude oils from the taranaki basin of new zealand have been studied the distribution of c14 c15 and c16 bicyclanes was essentially invariant amongst the various fields a suggestion is made that the proportion of rearranged to total drimanes may be related to maturity and the ratio of homodrimane to drimane may be related to depositional environment mass spectra are reported for a number of unidentified sesquiterpanes including possibly norbisabolane and bisabolane the distribution of bi tri and tetracyclic diterpanes was very similar to that of crude oils from the gippsland basin of south east australia the occurrence of rimuane was confirmed 8 h labdane was identified and 4 h 18 norisopimarane was tentatively identified isopimarane dominated the diterpane distribution of oils from the maui field in the south west of the basin and its abundance gradually diminished in a north westerly direction until it became a minor component of oil from the new plymouth field this trend coincided with an increase in the complexity of the triterpane distribution and with the oleanane content of the oils these northwards trends also followed the evolution of coal deposits in the region the diterpanes in these oils had the same structure as those which occur in extant trees of the araucariaceae and podocarpaceae which flourish in new zealand today and did so even more extensively in the past coal measures formed from forests of such trees are probably the source of the diterpanes a situation analogous to that in the gippsland basin of south eastern australia tricyclanes of the cheilanthane series were not detected in any of the taranaki oils lending support to the view that these tricyclanes occur most abundantly in oils derived from marine sources c24 tetracyclanes secotriterpanes occurred abundantly in all the oils as they do in terrigenous oils from other parts of the world

isolation and structural characterisation of isopimarane in some new zealand seep oils abstract isopimarane a tricyclic diterpane was isolated from some new zealand late cretaceous seep oils and coals in which it occurs in abundance the structure and absolute stereochemistry of this terrigenous oil biomarker were determined by nmr spectroscopy cd and synthesis

diterpenoid hydrocarbons in sediments from an offshore labrador well abstract aliphatic hydrocarbon fractions isolated from sediments r 0 0 4 of eocene palaeocene age taken between 2860 and 3055 m in an offshore labrador well were shown to be dominated by a number of compounds with kovats retention indices in the range 1875 1975 analyses of these hydrocarbons by gas chromatography and computerized gas chromatography mass spectrometry suggested that they were tricyclic diterpenoids interpretation of the mass spectra allowed structures to be assigned to some of the compounds and to be proposed for others they appear to belong to the primarane abietane and kaurane classes of hydrocarbons the diterpanes have been used to detect cavings in the deeper sediments between 3055 and 3270 m these compounds are either absent or trace components only of the dst 1 condensate 3212 3256 m or oil impregnating a sandstone core 3250 m and are only abundant in the cuttings from the same depth interval this occurrence of diterpanes in cuttings from the reservoir interval is due mostly to cavings resin like materials from which diterpanes are derived have not contributed significantly to the genesis of the condensate

interdecadal variability in a hybrid coupled ocean atmosphere model abstract a hybrid coupled ocean atmosphere model is used to investigate low frequency variability in the climate system the model s atmospheric component is a budyko sellers north two dimensional energy balance model the oceanic component is a simplified general circulation model the coupled model is confined to an idealized rectangular north atlantic basin in the present model version the ocean density depends exclusively on temperature an interdecadal oscillation with a period of 40 50 years is found in the hybrid coupled model when model parameters are within the climatological range even though density does not depend on salinity this interdecadal oscillation is characterized by a pair of vortices of opposite signs that grow and decay in quadrature with each other in the ocean s upper layer their centers follow each other anticlockwise through the northwestern quadrant of the model domain the interdecadal oscillation s physical mechanism resembles that of the interdecadal oscillation anal

stochastically driven multidecadal variability of the atlantic meridional overturning circulation in ccsm3 the atlantic meridional overturning circulation amoc in the last 250 years of the 700 year long present day control integration of the community climate system model version 3 with t85 atmospheric resolution exhibits a red noise like irregular multi decadal variability with a persistence longer than 10 years which markedly contrasts with the preceding 300 years of very regular and stronger amoc variability with 20 year periodicity the red noise like multi decadal amoc variability is primarily forced by the surface fluxes associated with stochastic changes in the north atlantic oscillation nao that intensify and shift northward the deep convection in the labrador sea however the persistence of the amoc and the associated oceanic anomalies that are directly forced by the nao forcing does not exceed about 5 years the additional persistence originates from anomalous horizontal advection and vertical mixing which generate density anomalies on the continental shelf along the eastern boundary of the subpolar gyre these anomalies are subsequently advected by the mean boundary current into the northern part of the labrador sea convection region reinforcing the density changes directly forced by the nao as no evidence was found of a clear two way coupling with the atmosphere the multi decadal amoc variability in the last 250 years of the integration is an ocean only response to stochastic nao forcing with a delayed positive feedback caused by the changes in the horizontal ocean circulation

gulf stream variability and ocean atmosphere interactions abstract time series of gulf stream position derived from the topex poseidon altimeter from october 1992 to november 1998 are used to investigate the lead and lag relation between the gulf stream path as it leaves the continental shelf and the changes in sea level pressure surface wind stress and sea surface temperature sst as given by the ncep reanalysis the dominant signal is a northward southward displacement of gulf stream axis 11 to 18 months after the north atlantic oscillation nao reaches positive negative extrema a sst warming cooling peaking north of the gulf stream is also seen to precede the latitudinal shifts but it is a part of the large scale sst anomaly tripole that is generated by the nao fluctuations there is no evidence that the gulf stream shifts have a direct impact onto the large scale atmospheric circulation a fast passive response of the gulf stream to nao forcing is also suggested by a corresponding analysis of the yearly mean gulf stream position estimated from

effect of igneous intrusion on the organic geochemistry of a siltstone and an oil shale horizon in the midland valley of scotland abstract the effect of rapid thermal stress on the organic geochemistry of a siltstone intruded by a quartz dolerite dyke and an oil shale intruded by an alkali dolerite sill has been studied using optical petrography rock eval pyrolysis gas chromatrography and gas chromatography mass spectrometry maturity dependent ratios derived from both the aliphatic and aromatic hydrocarbon fractions corroborate the observation of raymond and murchison 1988b that the alkali dolerite sills which were intruded soon after sedimentation had a lesser effect than the later quartz dolerite intrusions the maturity parameters based on the alkylnaphthalene and alkylphenanthrene isomer ratios are more suitable for studying maturity variations in heat affected samples than those based on the commonly used aliphatic biological markers these aromatic compounds survive to higher ranks and the isomer ratios continue changing

observations of vertical currents and convection in the central greenland sea during the winter of 1988 1989 during the winter of 1988 1989 five acoustic doppler current profilers adcps were moored in the central greenland sea to measure vertical currents that might occur in conjunction with deep mixing and convection two adcps were looking up from about 300 m and combined with thermistor strings in the depth range 60 260 m two were looking downward from 200 m and one was looking upward from 1400 m first maxima of vertical velocity variance occurred at two events of strong cold winds in october and november when cooling and turbulence in the shallow mixed layer generated internal waves in the thermocline beginning in late november the marginal ice zone expanded eastward over the central greenland sea reaching its maximum extent in late december in mid january a bay of ice free water opened over the central greenland sea leaving a wedge of ice the is odden curled around it along the axis of the jan mayen current and then northeastward and existing well into april 1989 below the ice a mixed layer at freezing temperatures developed that increased in thickness from 60 to 120 m during the period of ice cover corresponding to an average heat loss of about 40 w m 2 through brine rejection mixed layer salinity increased steadily reducing stability to underlying weakly stratified layers roach et al 1993 during the ice cover period vertical currents were at a minimum after the opening of the ice free bay successive mixed layer deepening to 350 m occurred in conjunction with cooling events around february 1 and 15 accompanied by strong small scale vertical velocity variations upward mixing of more saline waters of atlantic origin during this phase reduced the stability further generating a pool of homogeneous water of 50 km horizontal extent in the central greenland sea preconditioned for subsequent convection to greater depths individual convection events were observed during march 6 16 associated with downward velocities at the 1400 m level of about 3 cm s l one event was identified as a plume of about 300 m horizontal scale in agreement with recently advanced scaling arguments and model results and with earlier similar observations in the gulf of lions western mediterranean the deep convection occurred in the center of the ice free bay hence brine rejection did not seem necessary for its generation plume temperatures at 1400 m were generally higher than that of the homogeneous surface pool suggesting entrainment of surrounding warmer waters on the way down mean vertical velocity over a period of convection events was indistinguishable from zero suggesting that plumes served as a mixing agent rather than causing mean downward transport of water masses however different from the surface pool that was governed by mixed layer physics the water between 400 and 1400 m was not horizontally homogenized in a large patch by the sporadic plumes overall and compared to results from the gulf of lions convection activity in the central greenland sea was weak and limited to intermediate depths in winter 1988 1989

long term coordinated changes in the convective activity of the north atlantic the north atlantic is a peculiarly convective ocean the convective renewal of intermediate and deep waters in the labrador sea and greenland iceland sea both contribute significantly to the production and export of north atlantic deep water thus helping to drive the global thermohaline circulation while the formation and spreading of 18 degree water at shallow to intermediate depths off the us eastern seaboard is a major element in the circulation and hydrographic character of the west atlantic for as long as time series of adequate precision have been available to us it has been apparent that the intensity of convection at each of these sites and the hydrographic character of their products have been subject to major interannual change as shown by aagaard 1968 clarke et al 1990 and meincke et al 1992 for the greenland sea in the ows bravo record from the labrador sea eg lazier 1980 et seq and at the panulirus hydrostation s site in the northern sargasso off bermuda eg jenkins 1982 talley and raymer 1982 this paper reviews the recent history of these changes showing that the major convective centres of the greenland and labrador seas are currently at opposite convective extrema in our postwar record with vertical exchange at the former site limited to 1000 m or so but with labrador sea convection reaching deeper than previously observed to over 2300 m as a result greenland sea deep water has become progressively warmer and more saline since the early 70 s due to increased horizontal exchange with the arctic ocean through fram strait while the labrador sea water has become progressively colder and fresher over the same period through increased vertical exchange most recently convection has become deep enough there to reach into the more saline nadw which underlies it so that cooler but now saltier and denser lsw has resulted

initialisation and predictability of the amoc over the last 50 years in a climate model the mechanisms involved in atlantic meridional overturning circulation amoc decadal variability and predictability over the last 50 years are analysed in the ipsl cm5a lr model using historical and initialised simulations the initialisation procedure only uses nudging towards sea surface temperature anomalies with a physically based restoring coefficient when compared to two independent amoc reconstructions both the historical and nudged ensemble simulations exhibit skill at reproducing amoc variations from 1977 onwards and in particular two maxima occurring respectively around 1978 and 1997 we argue that one source of skill is related to the large mount agung volcanic eruption starting in 1963 which reset an internal 20 year variability cycle in the north atlantic in the model this cycle involves the east greenland current intensity and advection of active tracers along the subpolar gyre which leads to an amoc maximum around 15 years after the mount agung eruption the 1997 maximum occurs approximately 20 years after the former one the nudged simulations better reproduce this second maximum than the historical simulations this is due to the initialisation of a cooling of the convection sites in the 1980s under the effect of a persistent north atlantic oscillation nao positive phase a feature not captured in the historical simulations hence we argue that the 20 year cycle excited by the 1963 mount agung eruption together with the nao forcing both contributed to the 1990s amoc maximum these results support the existence of a 20 year cycle in the north atlantic in the observations hindcasts following the cmip5 protocol are launched from a nudged simulation every 5 years for the 1960 2005 period they exhibit significant correlation skill score as compared to an independent reconstruction of the amoc from 4 year lead time average this encouraging result is accompanied by increased correlation skills in reproducing the observed 2 m air temperature in the bordering regions of the north atlantic as compared to non initialized simulations to a lesser extent predicted precipitation tends to correlate with the nudged simulation in the tropical atlantic we argue that this skill is due to the initialisation and predictability of the amoc in the present prediction system the mechanisms evidenced here support the idea of volcanic eruptions as a pacemaker for internal variability of the amoc together with the existence of a 20 year cycle in the north atlantic they propose a novel and complementary explanation for the amoc variations over the last 50 years

hydrothermal petroleums from yellowstone national park wyoming u s a abstract in yellowstone national park oil is actively discharging with thermal waters at several widely separated thermal areas samples from two locations were studied petroleum from calcite springs occurs as vapor condensates in steam vents detailed geochemical analyses show a complex origin for the petroleum fluid deeply buried hydrothermally altered sedimentary rocks are believed to have contributed a high temperature pyrolysate consisting largely of polynuclear aromatic hydrocarbons and heterocyclic compounds shallow sedimentary rocks which are also hydrothermally altered have contributed large amounts of aromatic and polar compounds as well as minor amounts of hydrocarbons the permian phosphoria formation is suggested as a likely source rock for the bulk of the oils autochthonous pyrolysates and lipids from thermally altered surface and near surface bacterial and land plant debris have also been introduced to the vents the latter may have been introduced by downward percolating meteoric water the oil from rainbow springs is a highly paraffinic low s crude oil depleted in light hydrocarbons unlike the calcite springs samples the oil from rainbow springs is believed to have originated from a single sedimentary source rock with little or no hydrocarbon contributions from surface biota the oil contains a unique molecular marker assemblage that suggests both gymnosperm and angiosperm input and places the age of the source unit in the tertiary consideration of the local stratigraphy and water temperatures limits the probable source zone to the eocene aycross formation an intra volcanic lacustrine mudstone calculation of deep water temperatures indicates that this unit is exposed to thermal waters in an extensive near surface aquifer such conditions are consistent with the widespread surface manifestations and biomarker kinetic models consideration of the petroleum chemistry and regional hydrodynamics indicates that the yellowstone park oils did not migrate into the park from distant sources the chemical data are also inconsistent with the oils being generated and trapped prior to tertiary volcanism at both calcite springs and rainbow springs oil generation appears to be contemporaneous and is attributed to thermal alteration of relatively shallow sedimentary rocks by hydrothermal fluids

kinematics of the pacific equatorial undercurrent an eulerian and lagrangian approach from gcm results abstract three dimensional monthly velocity fields from an ocean general circulation model are used to study the annual mean mass balance of the pacific equatorial undercurrent euc eulerian diagnostics are used to evaluate the various meridional vertical and zonal mass fluxes related to the euc there are several distinct regimes along the equator showing clear asymmetries between the western and eastern parts of the basin and between the northern and southern edges of the euc meridional fluxes are decomposed into pure ekman divergence and geostrophic convergence and it is shown that the asymmetries are mainly related to the spatial structure of the ekman divergence and thus to that of the trade winds lagrangian calculations are used to evaluate accurately the mass transfers between various sections of the euc and between the euc domain and the tropics the authors show that geostrophic convergence only ventilates the upper layers of the euc and that the euc really is a tongue of water flowing

crystallization of alpo4 sio2 solid solutions from granitic melt and implications for p rich melt inclusions in pegmatitic quartz aluminum orthoposphate alpo 4 has polymorphs isostructural with tridymite cristobalite and quartz berlinite is the low temperature form that corresponds to quartz we report berlinite quartz solid solutions to crystallize from a synthetic p rich peraluminous granitic melt similar in composition to the most volatile rich silicate melt inclusions found in pegmatites the crystallization took place in experiments performed in cold seal pressure vessels at 450 700 c and 0 1 0 2 gpa h 2 o pressure at these conditions the berlinite quartz mutual solubility is limited to 5 7 mol sio 2 on the phosphate side of the solvus and to the maximum of 1 mol alpo 4 on the silica rich side the mutual solubility appears to decrease with falling temperature at low t the crystals of berlinite quartz solid solutions are strongly zoned and show complex intergrowths between the p rich and silica rich phases they were studied by electron microprobe transmission electron microscopy and raman spectroscopy in the light of our new experimental results the extreme p enrichment reported earlier for some natural quartz hosted melt inclusions may be explained as a post entrapment contamination by the berlinite bearing host

ocean gyre circulation changes associated with the north atlantic oscillation abstract observational evidence is presented for interannual to interdecadal variability in the intensity of the north atlantic gyre circulation related to the atmospheric north atlantic oscillation nao patterns a two point baroclinic pressure difference between the subtropical and subpolar gyre centers an oceanic analogue to the much used sea level pressure slp based atmospheric nao indices is constructed from time series of potential energy anomaly pea derived from hydrographic measurements in the labrador basin and at station s near bermuda representing the upper 2000 db eastward baroclinic mass transport between the two centers the transport index indicates a gulf stream and north atlantic current that gradually weakened during the low nao period of the 1960s and then intensified in the subsequent 25 years of persistently high nao to a record peak in the 1990s the peak to peak amplitude difference was 15 20 megatons per second mt s 1 with a 43 yr mean of about 60 mt s 1 a change of 25 33

variability of the atlantic meridional overturning circulation in ccsm4 abstractatlantic meridional overturning circulation amoc variability is documented in the community climate system model version 4 ccsm4 preindustrial control simulation that uses nominal 1 horizontal resolution in all its components amoc shows a broad spectrum of low frequency variability covering the 50 200 yr range contrasting sharply with the multidecadal variability seen in the t85 1 resolution ccsm3 present day control simulation furthermore the amplitude of variability is much reduced in ccsm4 compared to that of ccsm3 similarities as well as differences in amoc variability mechanisms between ccsm3 and ccsm4 are discussed as in ccsm3 the ccsm4 amoc variability is primarily driven by the positive density anomalies at the labrador sea ls deep water formation site peaking 2 yr prior to an amoc maximum all processes including parameterized mesoscale and submesoscale eddies play a role in the creation of salinity anomalies that dominate these density anomalies high nordic sea densi

spectral characteristics of the response of the meridional overturning circulation to deep water formation abstract the response of the upper limb of the meridional overturning circulation to the variability of deep water formation is investigated analytically with a linear reduced gravity model in basins of simple geometry the spectral characteristics of the model response are first derived by prescribing white noise fluctuations in the meridional transport at the northern boundary although low frequency basin modes are solutions to the eigenproblem they are too dissipative to be significantly excited by the boundary forcing and the thermocline depth response has a red spectrum with no prevailing time scale other than that of a high frequency equatorial mode only flattening at the millennial time scale because of vertical diffusivity the meridional transport is asymmetric about the equator because the northern part of the basin is directly influenced by the boundary forcing while the southern part is mostly set in motion by long rossby waves this results in the equator acting as a low pass filter for

the variability of the atlantic meridional overturning circulation the north atlantic oscillation and the el nino southern oscillation in the bergen climate model abstract the link between the interannual to interdecadal variability of the atlantic meridional overturning circulation amoc and the atmospheric forcing is investigated using 200 yr of a control simulation of the bergen climate model where the mean circulation cell is rather realistic as is also the location of deep convection in the northern north atlantic the amoc variability has a slightly red frequency spectrum and is primarily forced by the atmosphere the maximum value of the amoc is mostly sensitive to the deep convection in the irminger sea which it lags by about 5 yr the latter is mostly forced by a succession of atmospheric patterns that induce anomalous northerly winds over the area the impact of the north atlantic oscillation on deep convection in the labrador and greenland seas is represented realistically but its influence on the amoc is limited to the interannual time scale and is primarily associated with wind forcing the tropical pacific shows a strong variability in the model

processes governing the recovery of a perturbed thermohaline circulation in hadcm3 abstract in an experiment with the latest version of the hadley centre climate model the model response has been analyzed after the thermohaline circulation thc in the atlantic ocean has been suppressed the suppression is induced by a strong initial perturbation to the salinity distribution in the upper layer of the northern north atlantic the model is then allowed to adjust freely salinity gradually increases and deep water formation in the greenland and norwegian seas restarts later also in the labrador sea the meridional overturning recovers after about 120 yr in the first few decades when the overturning is very weak surface air temperature is dominated by cooling of much of the northern hemisphere and weak warming of the southern hemisphere leading to maximum global cooling of 0 9 c the disruption to the atmosphere s radiation balance results in a downward flux anomaly at the top of the atmosphere maximally 0 55 w m 2 in the first decade then decreasing with the thc recovery the processes

petrological palynological and geochemical characteristics of eureka sound group coals stenkul fiord southern ellesmere island arctic canada abstract late paleocene early eocene coal bearing strata are widespread across the canadian arctic archipelago laterally continuous seams of substantial thickness are present in the iceberg bay formation eureka sound group at stenkul fiord ellesmere island sixty four coal seams with a cumulative thickness of 53 m of coal occur in a 450 m sequence the investigation of the composite section is based on examination of 19 samples from seams thicker than 1 m and 7 samples from marker seams used for correlation purposes the coals consist predominantly of wood derived huminite macerals 79 98 vol structured huminite macerals are dominant in the top part of the section whereas detrital components are abundant in the lower part the liptinite fraction is dominated by sporinite and cutinite 1 9 vol inertinite content is very low except at the base of the section 0 14 vol reflectances determined on eu ulminite 0 36 0 43 r o geochemical parameters and thermal alteration indices indicate that the coals are of lignite to subbituminous rank the dominance of diterpanes and the abundance of taxodiaceae and pinaceae pollen suggest that most of the organic matter is of gymnospermous origin pinaceae pollen is abundant in the lower part of the section and taxodiaceae is abundant in the upper part the abundance of angiosperm pollen in most of the section suggests however that angiospermous plants were significant members of the flora the depositional environment for the iceberg bay formation coals at stenkul fiord is that of forested swamps on an alluvial plain pollen assemblages indicate a late paleocene early eocene age for the section and a temperate moist climate