warming of global abyssal and deep southern ocean waters between the 1990s and 2000s contributions to global heat and sea level rise budgets abyssalglobalanddeepsouthern oceantemperature trendsarequantifiedbetweenthe1990sand2000sto assesstheroleofrecentwarmingoftheseregionsin globalheatandsealevelbudgets theauthors1 compute warming rates with uncertainties along 28 full depth high quality hydrographic sections that have been occupied two or more times between 1980 and 2010 2 divide the global ocean into 32 basins defined by the topography and climatological ocean bottom temperatures and then 3 estimate temperature trends in the 24 sampled basins the three southernmost basins show a strong statistically significant abyssal warming trend with that warming signal weakening to the north in the central pacific western atlantic and eastern indian oceans eastern atlantic and western indian ocean basins show statistically insignificant abyssal cooling trends excepting the arctic ocean and nordic seas the rate of abyssal below 4000 m global ocean heat content change in the 1990s and 2000s is equivalent to a heat flux of 0 027 60 009 w m 22 applied over the entire surface of the earth deep 1000 4000 m warming south of the subantarctic front of the antarctic circumpolar current adds 0 068 60 062 w m 22 the abyssal warming produces a 0 053 60 017 mm yr 21 increase in global average sea level and the deep warming south of the subantarctic front adds another 0 093 60 081 mm yr 21 thus warmingin theseregions ventilatedprimarilyby antarcticbottomwater accounts for a statistically significant fraction of the present global energy and sea level budgets

a new look at the saturn system the voyager 2 images voyager 2 photography has complemented that of voyager i in revealing many additional characteristics of saturn and its satellites and rings saturn s atmosphere contains persistent oval cloud features reminiscent of features on jupiter smaller irregular features track out a pattern of zonal winds that is symmetric about saturn s equator and appears to extend to great depth winds are predominantly eastward and reach 500 meters per second at the equator titan has several haze layers with significantly varying optical properties and a northern polar collar that is dark at short wavelengths several satellites have been photographed at substantially improved resolution enceladus surface ranges from old densely cratered terrain to relatively young uncratered plains crossed by grooves and faults tethys has a crater 400 kilometers in diameter whose floor has domed to match tethys surface curvature and a deep trench that extends at least 270 around tethys circumference hyperion is cratered and irregular in shape iapetus bright trailing hemisphere includes several dark floored craters and phoebe has a very low albedo and rotates in the direction opposite to that of its orbital revolution with a period of 9 hours within saturn s rings the birth of a spoke has been observed and surprising azimuthal and time variability is found in the ringlet structure of the outer b ring these observations lead to speculations about saturn s internal structure and about the collisional and thermal history of the rings and satellites

circulation mixing and production of antarctic bottom water abstract the antarctic source of bottom water to the abyssal layer of the world ocean is examined as well as its large scale flow pattern and ultimate entrainment rate into the deep water above we make use of the available high quality station data in the southern ocean to construct bottom maps of neutral density and mean property maps including chlorofluorocarbon cfc for the abyssal layer underneath a selected neutral density surface the maximum density at the sill depth of drake passage is used to distinguish between the voluminous deep water mass that is a continuous component of the antarctic circumpolar current from the relatively denser bottom water originated along the antarctic continental margins based on water density antarctic bottom water aabw is defined here generically to include all volumes of non circumpolar water of antarctic origin over the shelf regime multiple localized sources of specific aabw types contribute to the abyssal layer of the adjacent antarctic basins characteristics of these dense bottom waters reflect closely those observed on the parent shelf water mass spreading paths of newly formed deep and bottom waters over the slope regime and their subsequent oceanic circulation patterns are analyzed on the basis of global property maps for the aabw layer interior mixing and interbasin exchanges of aabw are deduced from mean characteristic curves following the southern streamline of the antarctic circumpolar current outflow and mixing of aabw from the weddell sea to the argentine basin is depicted using density and cfc distributions of two zonal hydrographic lines recirculation and mixing of deep and bottom waters within the weddell gyre are also detailed using a meridional section along the greenwich meridian the strength of all localized sources of aabw combined is estimated by two independent approaches an estimate of the total production rate of aabw is calculated based on the oceanic cfc budget for the aabw layer offshore of the 2500 m isobath the sum of all downslope inputs of well ventilated bottom water types underneath the top isopycnal must account for the measured cfc content in the bottom layer the resulting total aabw production rate is about 8 sv which is a conservative figure that neglects the loss of cfc bearing waters across the top isopycnal in recent years whereas about 9 5 sv is calculated assuming a well mixed bottom layer making use of their transient nature cfc distributions at the top of the aabw layer indicate that more direct and rapid entrainment of cfc rich bottom waters below occurs over localized areas with relatively strong upwelling rates and enhanced vertical mixing a second more ad hoc but independent oceanic mass budget of the bottom layer is also constructed a typical basin wide rate of deep upwelling of 3 10 7 m s 1 requires 10 sv 1 sv 106 m3 s 1 of newly formed aabw to sink down the slope around antarctica we have also formulated a spatial distribution of deep upwelling on the isopycnal at the top of the aabw it is expressed as a combination of wind topographic and turbulent components which in turn are functions of the isopycnal depth bottom depth and bottom layer thickness this non uniform upwelling field yields about 12 sv of aabw exported across the top isopycnal fortuitously the overall average of upward speed at the top isopycnal 3 7 10 7 m s 1 compares well with previous estimates of deep upwelling in the northern basins a series of likely sites for strong vertical entrainment of aabw are clearly identified in the modeled distribution of deep upwelling consonant with the observed cfc distributions on the top isopycnal altogether regions with relatively high upwelling rates 5 10 7 m s 1 occupy only a quarter of the total areal extent of the top isopycnal but they account for as much as 45 of the total vertical transport

suppression of eddy diffusivity across jets in the southern ocean abstract geostrophic eddies control the meridional mixing of heat carbon and other climatically important tracers in the southern ocean the rate of eddy mixing is typically quantified through an eddy diffusivity there is an ongoing debate as to whether eddy mixing in enhanced in the core of the antarctic circumpolar current or on its flanks a simple expression is derived that predicts the rate of eddy mixing that is the eddy diffusivity as a function of eddy and mean current statistics this novel expression predicts suppression of the cross jet eddy diffusivity in the core of the antarctic circumpolar current despite enhanced values of eddy kinetic energy the expression is qualitatively and quantitatively validated by independent estimates of eddy mixing from altimetry observations this work suggests that the meridional eddy diffusivity across the antarctic circumpolar current is weaker than presently assumed because of the suppression of eddy mixing by the strong zonal current

a linear decomposition of the southern ocean thermohaline structure the thermohaline structure of the southern ocean is deeply influenced by the presence of the antarctic circumpolar current acc where water masses of the world ocean are advected transformed and redistributed to the other basins it remains a challenge to describe and visualize the complex 3d pattern of this circulation and its associated tracer distribution here a simple framework is presented to analyze the southern ocean thermohaline structure a functional principal component analysis pca is applied to temperature and salinity s profiles to determine the main spatial patterns of their variations using the southern ocean state estimate sose this study determines the vertical modes describing the southern ocean thermohaline structure between 5 and 2000 m the first two modes explain 92 of the combined s variance thus providing a surprisingly good approximation of the thermohaline properties in the southern ocean the first mode 72 of total variance accurately describes the north south property gradients the second mode 20 mostly describes salinity at 500 m in the region of antarctic intermediate water formation these two modes present circumpolar patterns that can be closely related with standard frontal definitions by projecting any given hydrographic profile onto the sose based modes it is possible to determine its position relative to the fronts the projection is successfully applied on the hydrographic profiles of the woce sr3 section the southern ocean thermohaline decomposition provides an objective way to define water mass boundaries and their spatial variability and has useful application for comparing model output with observations

physical controls on biogeochemical zonation in the southern ocean the primary control on the n s zonation of the southern ocean is the wind induced transport of the antarctic circumpolar current acc the acc divides the southern ocean into three major zones the subantarctic zone saz north of the acc the acc transport zone and the zone south of the acc saccz the zone of acc transport is most often subdivided into two zones the polar frontal zone pfz and the antarctic zone aaz but it may be appropriate to define more subzones or indeed only one at some longitudes to maintain geostrophic balance isopycnals must slope upwards to the south across the acc thus raising nutrient rich deep water closer to the surface as one goes polewards in addition silicate concentrations increase polewards along isopycnals because of diapycnic mixing with silicate rich bottom water surface silicate concentrations therefore decrease northwards from high levels in the saccz to low levels in the saz within the saz and pfz and even in the northern part of the aaz silicate levels may drop to limiting levels for siliceous phytoplankton production during summer nitrate concentrations also decrease northwards but only become limiting in the subtropical zone north of the saz the second circumpolar control is the changing balance of stratification with temperature dominating near surface stratification in the saz and salinity dominating further south because of fresh water input to the surface from melting ice this results in circumpolar features such as the subsurface 2 c temperature minimum and the subduction of the salinity minimum of antarctic intermediate water which are often but not always associated with frontal jets and large transports the transport of the acc is dynamically constrained into narrow bands the number and latitudinal location of which are controlled by the bathymetry and so vary with longitude thus it is not the fronts that are circumpolar but the total acc transport and scalar properties of the salinity and temperature fields evidence of summer silicate and nitrate uptake in all zones saz pfz and aaz shows that there is productivity despite their high nutrient low chlorophyll status blooms covering large areas say 400 km across in the pfz and aaz are found in the vicinity of submarine plateaux which suggest benthic iron fertilizatio

how does subantarctic mode water ventilate the southern hemisphere subtropics in several regions north of the antarctic circumpolar current acc deep wintertime convection refreshes pools of weakly stratified subsurface water collectively referred to as subantarctic mode water samw samw ventilates the subtropical thermocline on decadal timescales providing nutrients for low latitude productivity and potentially trapping anthropogenic carbon in the deep ocean interior for centuries in this work we investigate the spatial structure and timescales of mode water export and associated thermocline ventilation we use passive tracers in an eddy permitting observationally informed southern ocean model to identify the pathways followed by mode waters between their formation regions and the areas where they first enter the subtropics we find that the pathways followed by the mode water tracers are largely set by the mean geostrophic circulation export from the indian and central pacific mode water pools is primarily driven by large scale gyre circulation whereas export from the australian and atlantic pools is heavily influenced by the acc export from the eastern pacific mode water pool is driven by a combination of deep boundary currents and subtropical gyre circulation more than 50 of each mode water tracer reaches the subtropical thermocline within 50 years with significant variability between pools the eastern pacific pathway is especially efficient with roughly 80 entering the subtropical thermocline within 50 years the time required for 50 of the mode water tracers to leave the southern ocean domain varies significantly between mode water pools from 9 years for the indian mode water pool to roughly 40 years for the central pacific mode water pool

an alternative model for positive shifts in shallow marine carbonate 13c and 18o positive shifts in global seawater d 13 cdic are related to changes in the ratio of organic relative to inorganic carbon burial in oceanic basins whereas factors such as climatic cooling and the accumulation of polar ice are known to cause positive shifts in d 18 o here an alternative model is proposed for the formation of local positive isotope shifts in shallow marine settings the model involves geochemically altered platform top water masses and the effects of early meteoric diagenesis on carbonate isotopic composition both mechanisms are active on modern sub tropical carbonate platforms and result in low carbonate d 13 ca ndd 18 o relative to typical oceanic values during high amplitude transgressive events the impact of isotopically light meteoric fluids on the carbonate geochemistry is much reduced and 13 c depleted platform top water mixes with open oceanic water masses having higher isotope values both factors are recorded as a transient increase in carbonate 13 c and 18 o relative to low background values these processes must be taken into consideration when interpreting the geochemical record of ancient epeiric seas

iapetus near surface thermal emission modeled and constrained using cassini radar radiometer microwave observations abstract since its arrival at saturn the cassini spacecraft has had only a few opportunities to observe iapetus saturn s most distant regular satellite these observations were all made from long ranges 100 000 km except on september 10 2007 during cassini orbit 49 when the spacecraft encountered the two toned moon during its closest flyby so far in this pass it collected spatially resolved data on the object s leading side mainly over the equatorial dark terrains of cassini regio cr in this paper we examine the radiometry data acquired by the cassini radar during both this close targeted flyby referred to as ia49 3 and the distant iapetus observations in the radar s passive mode the receiver functions as a radiometer to record the thermal emission from planetary surfaces at a wavelength of 2 2 cm on the cold icy surfaces of saturn s moons the measured brightness temperatures depend both on the microwave emissivity and the physical temperature profile below the surface down to a depth that is likely to be tens of centimeters or even a few meters combined with the concurrent active data passive measurements can shed light on the composition structure and thermal properties of planetary regoliths and thus on the processes from which they have formed and evolved the model we propose for iapetus microwave thermal emission is fitted to the ia49 3 observations and reveals that the thermal inertias sensed by the cassini radiometer over both cr and the bright mid to high latitude terrains namely ronceveaux terra rt in the north and saragossa terra st in the south significantly exceed those measured by cassini s cirs composite infrared spectrometer which is sensitive to much smaller depths generally the first few millimeters of the surface this implies that the subsurface of iapetus sensed at 2 2 cm wavelength is more consolidated than the uppermost layers of the surface in the case of cr a thermal inertia of at least 50 j m 2 k 1 s 1 2 and most probably 200 j m 2 k 1 s 1 2 is inferred this suggests a gradient in density with depth or more likely that the radiometer has probed the icy substrate underlying the dark layer furthermore the measured thermal emission is found to arise from the upper few meters of the subsurface which points to tholins rather than iron oxide compounds as the primary contaminants of the dark material we also find that although there is a latitudinal decrease probably related to the thinning of the dark layer away from the equator the cr region exhibits a high 2 2 cm emissivity 0 87 in average which is close to the emissivity of phoebe a putative source of the dark matter in the case of rt st model fitting points to a mean thermal inertia of 160 j m 2 k 1 s 1 2 along with the possible presence of an absorbing compound in the regolith of the bright terrains nevertheless this layer is transparent enough for the radiometer to capture the seasonal contrast between the northern and southern hemispheres lastly a global decline of the microwave emissivity with latitude is revealed it is probably indicative of a progressive increase of the water ice content in the near surface

depositional facies and stratal geometry of an upper carboniferous prograding and aggrading high relief carbonate platform cantabrian mountains n spain seismic scale continuous exposures of an upper carboniferous bashkirian moscovian carbonate platform n spain provide detailed information about the lithofacies and stratal geometries quantified with differential global positioning system measurements of microbial boundstone dominated steep prograding and aggrading platform margins progradational and aggradational platform to slope transects are characterized by distinct lithological features and stratal patterns that can be applied to the understanding of geometrically comparable high relief depositional systems the bashkirian is characterized by rapid progradation at rates of 415 970 m my 1 characteristic outerplatform facies are high energy grainstones with coated intraclasts ooids and pisoids moderate energy algal skeletal grainstones to packstones and lower energy algal packstone and boundstone units the moscovian aggradational phase is characterized by aggradation rates of 108 m my 1 coated grain shoals are less common whereas crinoidal bars nucleated in well circulated settings below wave base boundstones form a belt 30 300 m wide at the platform break and interfinger inwards with massive algal skeletal wackestones mud rich banks the progradational phase has divergent outer platform strata with basinward dips of 12 to 2 steep clinoforms with dips of 20 28 are 650 750 m in relief and possibly sigmoidal to concave in the lower part the basinward dipping outer platform strata might be depositional for less than 6 consistent with lithofacies deepening seaward the basinward dip is attributed to the downward shift of upperslope boundstone forced by late highstand and relative sea level fall and to compaction induced differential subsidence during progradation the aggradational phase is characterized by horizontally layered platform strata clinoforms steepen to 30 45 reaching heights of 850 m and are planar to concave the evolution from progradation to aggradation at the bashkirian moscovian boundary is attributed to increased foreland basin subsidence and decreased boundstone accumulation rates progradation was primarily controlled by boundstone growth rather than by highstand shedding from the platform top within the major phases aggradational progradational increments are produced by third to fourth order relative sea level

global ocean meridional overturning abstract a decade mean global ocean circulation is estimated using inverse techniques incorporating air sea fluxes of heat and freshwater recent hydrographic sections and direct current measurements this information is used to determine mass heat freshwater and other chemical transports and to constrain boundary currents and dense overflows the 18 boxes defined by these sections are divided into 45 isopycnal neutral density layers diapycnal transfers within the boxes are allowed representing advective fluxes and mixing processes air sea fluxes at the surface produce transfers between outcropping layers the model obtains a global overturning circulation consistent with the various observations revealing two global scale meridional circulation cells an upper cell with sinking in the arctic and subarctic regions and upwelling in the southern ocean and a lower cell with sinking around the antarctic continent and abyssal upwelling mainly below the crests of the major bathymetric ridges

isotopic records of brachiopod shells from the russian platform evidence for the onset of mid carboniferous glaciation we performed isotopic analyses of carboniferous brachiopod shells from the russian platform to examine global and regional environmental change along the western and eastern margins of laurussia during the formation of pangea and specifically to examine the isotopic evidence for the onset of mid carboniferous glaciation shell preservation was evaluated from shell microstructure cathodoluminescence trace element content and isotopic comparison with matrix material most interior nonluminescent nl prismatic shell appears to be chemically well preserved as indicated by low to undetectable si al fe and mn contents with minor exception nl shell 13c and 18o values are higher than those of corresponding cements and matrix the 13c record for the russian platform clearly shows a 3 increase from 2 4 0 7 to 5 5 0 6 in the serpukhovian or early bashkirian this shift was first reported by popp et al popp b n anderson t f sandberg p a 1986 brachiopods as indicators of original isotopic compositions in some paleozoic limestones geol soc am bull 97 1262 1269 but had not been documented for a single region widespread occurrence of high 13c values in the late carboniferous support the interpretation of popp et al with regard to this shift as a record of increased burial of organic carbon north american sections show a mid carboniferous 13c shift of only 1 5 we hypothesize that the reduced 13c shift reflects enhanced upwelling on the epicontinental seas of north america after the closing of the seaway between laurussia and gondwana the 18o record for the russian platform shows a 1 8 increase in the mid carboniferous correlative with increased occurrence of glacial sediments and a drop in sea level as a first approximation ice volume calculations suggest that 0 7 of the mid carboniferous 18o shift is due to changes in seawater 18o and 1 1 is due to 5 c cooling concurrent positive 13c and 18o shifts provide evidence for a relationship between mid carboniferous glaciation and burial of organic carbon presumably through changes in atmospheric co2 levels

southern ocean thermocline ventilation abstract an approximate mass volume budget in the surface layer of the southern ocean is used to investigate the intensity and regional variability of the ventilation process discussed here in terms of subduction and upwelling ventilation resulting from ekman pumping is estimated from satellite winds the geostrophic mean component is assessed from a climatology strengthened with argo data and the eddy induced advection is included via the parameterization of gent and mcwilliams together with eddy mixing estimates all three components contribute significantly to ventilation finally the seasonal cycle of the upper ocean is resolved using argo data the circumpolar averaged circulation shows an upwelling in the antarctic intermediate water aaiw density classes which is carried north into a zone of dense subantarctic mode water samw subduction although no consistent net production is found in the light samw density classes a large subduction of subtropical mode water stmw is observed the s

on the variability of antarctic circumpolar current fronts inferred from 1992 2011 altimetry abstractantarctic circumpolar current acc fronts defined as water mass boundaries have been known to respond to large scale atmospheric variabilities especially the southern hemisphere annular mode sam and el nino southern oscillation enso distinct patterns of localized variability in meridional front displacements during 1992 2011 are derived from the analysis of satellite sea surface height data major basin scale differences are found between the southeast pacific 150 90 w and the southeast indian 75 150 e sectors of the acc frontal positions in the southeast pacific show large year to year meridional fluctuations attributed mostly to enso and in part sam and no apparent seasonal cycles or long term trends in contrast summer winter frontal locations in the southeast indian extend farther to the south north of their long term mean distribution a southward drift of acc fronts is indicated over the indian sector during the past two decades this long term shift is not directly re

voyager photometry of europa abstract ninety voyager images ranging in phase angle from 3 to 143 and covering the spectral range from 0 34 to 0 58 m were analyzed to derive the photometric properties of europa at small phase angles the disk integrated phase curve is remarkable in that it shows little or no evidence of an opposition effect in agreement with earlier earth based observations by millis and thompson icarus 26 408 1975 the phase integral determined in the voyager clear filter centered near 0 47 m is 1 09 0 11 in good agreement with previous estimates based on radiometry the bolometric bond albedo is 0 62 0 14 the scattering properties of europa in general and of the two major terrain types bright plains and darker mottled terrain in particular cannot be represented by a lunar like photometric law however an equation which is a linear superposition of a lunar like scattering law and a lambert component provides an adequate simple representation of the scattering properties the plains are photometrically more homogeneous than the darker mottled terrain in the voyager clear filter the average normal reflectance is 0 71 for the plains on both the leading and trailing hemispheres for the darker mottled terrain the values are 0 60 on the leading hemisphere and 0 48 on the trailing one

coherent heat patterns revealed by unsupervised classification of argo temperature profiles in the north atlantic ocean abstract a quantitative understanding of the integrated ocean heat content depends on our ability to determine how heat is distributed in the ocean and identify the associated coherent patterns this study demonstrates how this can be achieved using unsupervised classification of argo temperature profiles the classification method used is a gaussian mixture model gmm that decomposes the probability density function of a dataset into a weighted sum of gaussian modes it is determined that the north atlantic argo dataset of temperature profiles contains 8 groups of vertically coherent heat patterns or classes each of the temperature profile classes reveals unique and physically coherent heat distributions along the vertical axis a key result of this study is that when mapped in space each of the 8 classes is found to define an oceanic region even if no spatial information was used in the model determination the classification result is independent of the location and time of the argo profiles two classes show cold anomalies throughout the water column with amplitude decreasing with depth they are found to be localized in the subpolar gyre and along the poleward flank of the gulf stream and north atlantic current nac one class has nearly zero anomalies and a large spread throughout the water column it is found mostly along the nac one class has warm anomalies near the surface 50 m and cold ones below 200 m it is found in the tropical equatorial region the remaining four classes have warm anomalies throughout the water column one without depth dependance in the southeastern part of the subtropical gyre the other three with clear maximums at different depths 100 m 400 m and 1000 m these are found along the southern flank of the north equatorial current the western part of the subtropical gyre and over the west european basin these results are robust to both the seasonal variability and to method parameters such as the size of the analyzed domain

exploring the effects of overburden on the sublimation and transport of h2o on iapetus it has been shown through both measurements and simulations that there exists a measurable ice free porous overburden overlaying water ice on cassini regio mass transfer through this porous media in a vacuum would occur in the knudsen regime which provides sublimation rates orders of magnitude smaller than hertz langmuir sublimation the availability of water ice for transport from this region is thus currently controlled by mass transfer through the dark material overburden thermal segregation suggests that iapetus polar regions have been brightened via ballistic transport of water and its subsequent cold trapping since exogenic deposition models predict dark high latitudes on the leading hemisphere the limiting effect of the dark material on transport of water ice may thus greatly impact the current mass balance at the poles the effects of the overburden on the global stability and transport of h2o is addressed in order to gain insight into its influence on the polar albedo distribution and current state of thermal segregation within the dark terrain results indicate that thermal segregation is currently an inactive or weak process within cassini regio though it is an ongoing process at the inter terrain regions modeling of polar accumulation suggests that even accounting for the current dark material cover within cassini regio there exists sufficient ballistically inbound water to overcome exogenic darkening mechanisms topographic effects on local albedo differences are also simulated to provide a more complete water stability study of iapetus results suggest that topographically induced changes in heat flux may be sufficient to create the observed local albedo contrasts and also support ongoing dark exogenic deposition within cassini regio to explain the lack of bright slopes deep within the dark terrain

sublimation s impact on temporal change of albedo dichotomy on iapetus abstract iapetus one of the saturnian moons has an extreme albedo contrast between the leading and trailing hemispheres the origin of this albedo dichotomy has led to several hypotheses however it remains controversial to clarify the origin of the dichotomy the key approach is to investigate the detailed distribution of the dark material recent studies of impact craters and surface temperature from cassini spacecraft data implied that sublimation of h 2 o ice can occur on iapetus surface this ice sublimation can change the albedo distribution on the moon with time in this study we evaluate the effect of ice sublimation and simulate the temporal change of surface albedo we assume the dark material and the bright ice on the surface to be uniformly mixed with a certain volume fraction and the initial albedo distribution to incorporate the dark material deposits on the surface that is the albedo at the apex is lowest and concentrically increases in a sinusoidal pattern this situation simulates that dark materials existed around the iapetus orbit billions of years ago and the synchronously rotating iapetus swept the material and then deposited it on its surface the evolution of the surface albedo during 4 0 gyr is simulated by estimating the surface temperature from the insolation energy on iapetus including the effect of saturn s eccentricity and iapetus obliquity precession and evaluating the sublimation rate of h 2 o ice from the iapetus surface as a result we found that the distribution of the surface albedo changed dramatically after 4 0 gyr of evolution the sublimation has three important effects on the resultant surface albedo first the albedo in the leading hemisphere has significantly decreased to approach the minimum value second the albedo distribution has been elongated along the equator third the edge of the low albedo region has become clear considering the effect of ice sublimation the current albedo distribution can be reconstructed from the sinusoidal albedo distribution suggesting the apex antapex cratering asymmetry as a candidate for the origin of the albedo dichotomy from the model analysis we obtained an important aspect that the depth of the turn over layer where the darkening process proceeded for 4 gyr should be an order of 10 cm which is consistent with evaluation from the cassini radar observations

bacterial mediation red matrices diagenesis devonian montagne noire southern france abstract two devonian red carbonate rock sections are studied in the montagne noire at coumiac frasnian famennian and at the pic de vissou eifelian givetian the sediments are grey red mudstones and wackestones rich in pelagic fossils they are characteristic of an outer ramp the coumiac sequence is condensed with numerous hardgrounds and hiatuses the pic de vissou succession is more complete and of shallower origin in both cases the origin of the red coloration of the micritic matrix is probably linked to bacterial activity which produced submicronic hematite both iron and manganese concentrations are low average 0 2 bacteria form ferruginous microstromatolites blisters microtufts hedgehogs filling sponge perforations and thin continuous mineralized films probably biofilms hardgrounds are underlined by ferruginous microstromatolites the origin of the matrix color is probably related to the destruction of these bacterial constructions the submicronic hematite ultimately coating the crystal faces of the calcite mosaic during early lithification microfissures appeared and were invaded by microbial colonies scanning electron microscopy sem shows that these colonies are composed of spheroidal beads this suggests continuity of the bacterial activity during early diagenesis later on these early fissures were cut by burrows subsequently a secondary fissure network transected all the previously mentioned sedimentary structures this late fissure network is characterized by diagenetically remobilized hematite and or calcite the latest alterations are stylolites and ultimate tectonic fractures

variability of subantarctic mode water and antarctic intermediate water in the drake passage during the late twentieth and early twenty first centuries a time series of the physical and biogeochemical properties of subantarctic mode water samw and antarctic intermediate water aaiw in the drake passage between 1969 and 2005 is constructed using 24 transects of measurements across the passage both water masses have experienced substantial variability on interannual to interdecadal time scales samw is formed by winter overturning on the equatorward flank of the antarctic circumpolar current acc in and to the west of the drake passage its interannual variability is primarily driven by variations in wintertime air sea turbulent heat fluxes and net evaporation modulated by the el nino southern oscillation enso despite their spatial proximity the aaiw in the drake passage has a very different source than that of the samw because it is ventilated by the northward subduction of winter water originating in the bellingshausen sea changes in aaiw are mainly forced by variability in winter water properties resulting from fluctuations in wintertime air sea turbulent heat fluxes and spring sea ice melting both of which are linked to predominantly enso driven variations in the intensity of meridional winds to the west of the antarctic peninsula a prominent exception to the prevalent modes of samw and aaiw formation occurred in 1998 when strong wind forcing associated with constructive interference between enso and the southern annular mode sam triggered a transitory shift to an ekman dominated mode of samw ventilation and a 1 2 yr shutdown of aaiw production the interdecadal evolutions of samw and aaiw in the drake passage are distinct and driven by different processes samw warmed by 0 3 c and salinified by 0 04 during the 1970s and experienced the reverse trends between 1990 and 2005 when the coldest and freshest samw on record was observed in contrast aaiw underwent a net freshening by 0 05 between the 1970s and the twenty first century although the reversing changes in samw were chiefly forced by a 30 yr oscillation in regional air sea turbulent heat fluxes and precipitation associated with the interdecadal pacific oscillation with a sam driven intensification of the ekman supply of antarctic surface waters from the south contributing significantly too the freshening of aaiw was linked to the extreme climate change that occurred to the west of the antarctic peninsula in recent decades there a freshening of the winter water ventilating aaiw was brought about by increased precipitation and a retreat of the winter sea ice edge which were seemingly forced by an interdecadal trend in the sam and regional positive feedbacks in the air sea ice coupled climate system all in all these findings highlight the role of the major modes of southern hemisphere climate variability in driving the evolution of samw and aaiw in the drake passage region and the wider south atlantic and suggest that these modes may have contributed significantly to the hemispheric scale changes undergone by those waters in recent decades

eddy heat diffusion and subantarctic mode water formation subantarctic mode waters samw form in the deep winter mixed layers occuring north of the subantarctic front saf the recent increase of hydrographic and surface drifter data in the southern ocean allows a better spatial representation of the distinct regions of samw formation this study focuses on the thermodynamical processes acting on the winter mixed layer heat budget eddy heat diffusion play a substantial role in the local heat balance whereas its action vanishes with large scale averaging south of the western boundary currents and north of the saf the eddy heating plays an important role in specific regions counterbalancing the cooling of the mixed layer by ekman advection and air sea fluxes specifically the eddy diffusion term reduces the tendency for mixed layer destabilisation north of the saf in the western indian ocean downstream of the agulhas retroflection and in the western pacific downstream of campbell plateau this role for mixed layer eddy fluxes emphasizes a large scale control of mixed layer properties by topography and mesoscale processes in the southern ocean

nature distribution and origin of co2 on enceladus abstract we present the first map of co2 at the surface of enceladus using data obtained by the cassini visible infrared mapping spectrometer vims in order to measure the weak and narrow co2 absorption band depths around 4 26 m we improved 1 the calibration of vims spectra 2 the calculation of geographic coordinates and 3 the projection techniques we averaged multiple observations of a given area to obtain a signal to noise ratio high enough to map the co2 abundances co2 is reliably detected mostly in the south polar region this region includes active faults tiger stripes the highest observed surface temperatures and locations of active plume eruptions the occurrence here of co2 is consistent with an endogenic origin controlled by tectonics both pure co2 ice and complexed co2 are detected from the positions of absorption bands between 4 27 and 4 24 m the highest concentrations of co2 are between the main active faults of the south polar region where the surface temperature is low pure co2 ice deposits at the surface of enceladus are best modeled by the formation of gas pockets below the icy crust and above the surface of the internal ocean these pockets eventually release cold co2 gas 70 to 119 k at low velocity seeping between the tiger stripes matson et al 2018 icarus 302 18 26 co2 clathrate hydrates may form in the ocean and may be subsequently released when a co2 gas pocket blows out and erupts other mechanisms may contribute to reinforcing the anti correlation of the co2 distribution of any type with respect to the location of the tiger stripes such as successive sublimation of co2 and condensation on colder areas and partial frost cover by h2o releases from plume eruptions

a pennsylvanian microbial boundstone dominated carbonate shelf in a distal foreland margin picos de europa province nw spain abstract a pennsylvanian bashkirian moscovian high rising microbial boundstone dominated carbonate platform 12 000 km2 developed in the external margin of a variscan foreland basin intensely studied in the northern domain cuera area the stratigraphy and sedimentology of the southern domain the picos de europa province is here revisited distribution of the bashkirian facies valdeteja formation defines a ramp low angle platform with an internal zone central and eastern sectors of the picos de europa province consisting of huge amounts of massive cement rich microbial boundstones surrounded by an external zone comprising lower slope boundstone derived breccias and basinal lime mudstones from the bashkirian moscovian transition to the early kasimovian picos de europa formation the carbonate platform moderately aggraded acquiring a high rising and flat topped geometry and then prograded rapidly into the external zone where platform derived carbonate sediment and clay sourced from the orogen were deposited seismic scale exposures of the western margin of the shelf show angular bedding relationship between basin toe of slope slope and platform top stratal domains with slope inclination up to 32 and a topographic relief of 550 m the platform evolution above described for the picos de europa province significantly differs with respect to the cuera area where platform mostly prograded during the bashkirian and subsequently aggraded during early moscovian the evolutionary differences between these two carbonate domains which are geographically close are interpreted as changes in tectonic subsidence distribution acting as the major factor controlling the large scale platform geometries in the active foreland basin context finally the tectonic overload due to the emplacement of the cuera thrust sheets during the moscovian kasimovian transition changed the platform growth style from progradational to aggradational and consequently the stacking pattern of the platform top cycles in the picos de europa province

the roughness of the dark side of iapetus from the 2004 to 2005 flyby abstract the roughness of a planetary surface offers clues to its past geologic history we apply a surface roughness model developed by buratti and veverka buratti b j veverka j 1985 icarus 64 320 328 to cassini iss data from the january 1st 2005 flyby of iapetus this model uses the observed scattering behavior to provide a depth to radius factor q quantifying the size of idealized craters on the surface our findings indicate that the surface on the dark side is significantly smoother than the surfaces of other icy low albedo saturnian satellites we have found that the average depth to radius on the leading dark side is 0 084 corresponding to a hapke mean slope angle of 6 as compared to the 13 33 hapke mean slope angle of other icy satellites buratti b j and 10 colleagues 2008 icarus 193 309 322 our results present a clearly different picture for the leading surface of iapetus suggesting that the dark deposit contributes to the decrease in macroscopic surface roughness of the leading side attempts were made to obtain an average depth to radius value for the trailing bright side however the scans of the bright side from this flyby exhibited large variations in albedo resulting in results that were physically unrealistic

the oman upwelling zone during 1993 1994 and 1995 abstract satellite derived sea surface temperature topex poseidon t p sea level anomalies slas model wind data and hydrographic data are used to characterize the upwelling along the oman coast during the us joint global ocean flux study us jgofs arabian sea process study asps in 1995 as well as to look at interannual variability in the upwelling over the period 1993 1995 empirical orthogonal function eof analysis of the satellite derived sea surface temperature sst at the locations of the us jgofs standard stations shows the first mode which represents a biannual variability contributes 67 of the total variance in addition the sst shows the upwelling front moving offshore with the development of southwest sw monsoon in early june 1995 reaching a maximum distance of approximately 120 km by late august 1995 finally sst shows the persistence of cold upwelling waters for nearly a month after the end of the sw monsoon within the bays along the oman coast topex poseidon slas indicate that with the onset of the sw monsoon a 30 cm drop in steric height is observed along the oman coast associated the presence of the cool upwelled waters this drop in steric height sets up a horizontal pressure gradient and results in a compensating along shore northeastward flowing geostrophic current east arabian current eac during the sw monsoon similarly the altimeter data slow an offshore decrease in steric height during the northeast ne monsoon indicating a seasonal reversal in direction of the eac with flow to the southwest subsurface temperature data indicate that the actual uplifting of isotherms associated with the upwelling can be found to a distance of approximately 260 km from the shore and to a depth of 150 200 m using along track altimetry data we estimate that for a region 260 km in offshore distance and 600 km alongshore 2 2 10 6 1 4 10 6 and 0 55 10 6 m 3 s 1 were upwelled through the 100 m level with upwelling velocities o 2 0 10 5 m s 1 during the sw monsoons of 1993 1994 and 1995 respectively the reduced upwelling in the summer of 1995 is attributed to a reduction in wind stress curl along the arabian coast when compared to 1993 and 1994

on a ring origin of the equatorial ridge of iapetus 1 most recent cassini observations by the imaging science subsystem iss showed that the third largest saturnian satellite iapetus has a curious ridge system exactly aligned with its equator porco et al 2005 because iapetus has a large hill sphere for the trapping of circum satellitary material a ring system might have been present during its formation a scenario is proposed to describe how the equatorial ridge system could have been produced by the collisional accretion of a ring remnant subsequent to the formation of the proto iapetus

voyager photometry of iapetus abstract voyager images of iapetus ranging in phase angle from 8 to 90 were used to define the satellite s photometric properties and construct an albedo map of its surface the images confirm that the albedo distribution has a roughly hemispheric asymmetry as had been inferred from earlier analyses of the disk integrated lightcurve on the darker leading hemisphere albedo contours are roughly elliptical in shape and centered at the apex of orbital motion flattened at the poles and elongated along the equator the reflectance within the darker material is lowest 0 02 0 03 at the apex and increases with increasing distance from the apex the albedo pattern on the brighter trailing hemisphere is more complex reflectance increases gradually with increasing distance from the interface with the darker material and reaches a maximum near the poles reflectances of 0 3 0 4 in the brighter material are common and the highest values probably reach 0 6 the transition in reflectance contours between the two materials is gradual rather than sharp and albedo histograms of images centered on the visually perceived boundary are weakly bimodal the dark material on iapetus is reddish the bright material somewhat less so

iron bacterial and fungal mats bajocian stratotype mid jurassic northern normandy france abstract the oolithe ferrugineuse de bayeux formation is located at the historical bajocian stratotype of sainte honorine des pertes north of bayeux normandy the condensed formation ranges from the base of the humphriesianum zone to the parkinsoni zone and is divided into four beds of decimetric scale three main microfacies are present 1 oncoid rudstones 2 ooid bioclastic packstones and 3 silty burrowed wackestones packstones sedimentation took place in a very quiet environment below the photic zone and below or near the storm wave base the general setting is a distal carbonate ramp its lower part characterized by hemipelagic sedimentation indicated by the presence of planktonic foraminifers the inferred depth is around 100 m free oxygen concentration was low dysaerobic conditions are indicated by a scarcity of benthic macrofauna ferruginous structures are numerous in the first two microfacies and absent in the last hematite staining is not uniform and follows many sedimentary patterns among the more widespread fe structures are perforation infillings with endolithic micro organisms microstromatolites oncoids ooids blisters coatings and hardgrounds these structures can be associated and none are mutually exclusive hematite coated filaments of different sizes and shapes are observed in the micrite matrix the walls of various organisms the calcite crystals associated with the fe cortical laminations the perforations and burrow the hardgrounds and microstromatolites petrographical and sem examinations suggest that the laminated crusts oncoids and hardgrounds are formed by microbial iron mats dominated by filamentous bacteria and fungi seven types of microbes are recognized filaments five morphotypes spheroidal bodies and stalked bodies filamentous microfossils of type 1 to 4 resemble the present day filamentous bacteria beggiatoales and cytophagaceae because of their large diameter and their branching nature filaments of type 5 are possibly filamentous fungi another argument in favor of fungi is the presence of stalked and spheroidal bodies that resemble zoosporangia and oogonia of some oomycota in deep calm and dysaerobic waters many interfaces e g between aerobic and dysaerobic waters are present in the sediments the stability of the soluble reduced state of iron fe 2 is higher at such interfaces and many ferric iron encrusted microbial fossils are observed iron could thus serve as an electron donor for microbial iron oxidation processes other microbial iron deposition pathways are also possible it appears that regardless of geological age paleozoic mesozoic and geographical location the same microbiological mechanisms are probably responsible for the red color in calcareous stratified or unstratified bodies the presence of fossilized iron encrusted bacteria and fungi at interfaces may therefore serve as an indicator of anoxic to dysaerobic conditions in various paleo micro environments

delta 18 and delta 13 c variations in late devonian marine cements from the golden spike and nevis reefs alberta canada abstract for geologists and geochemists concerned about the chemical and thermal evolution of oceans deciphering primary marine 13c and 18o values from ancient marine carbonates can provide useful data for the physical and chemical modelling of ancient oceans although abiotic aragonite and magnesian calcite marine cements have commonly been overlooked because of their susceptibility to diagenetic alteration petrographic and chemical analysis of radiaxial fibrous calcite from two upper devonian frasnian pinnacle reefs golden spike and nevis of central alberta indicates that these magnesium rich cements preserve original marine 18o and 13c values in the pursuit of primary marine isotopic compositions it is necessary to characterize the isotopic compositions of diagenetic cement phases subaerial exposure and meteoric diagenesis of the interior of the golden spike reef is recorded by vadose cements caliche and clear non ferroan meteoric calcite spar with distinctive black and yellow cathodoluminescence cl zones 18o 13c crossplots of caliche and meteoric phreatic cement data form an inverted j curve typical of rock water reactions in meteoric systems a late phase of calcite spar with variable inclusion density and fe2 content and diffusely zoned red orange cl is associated with late fractures and stylolites and it precipitated during subsequent burial of the reef unaltered centers of radiaxial fibrous cement crystals are nonluminescent inclusion free and enriched in magnesium while diagenetically altered crystal terminations inter crystalline boundaries and crystal substrates are brightly luminescent inclusion rich microdolomite and fluid inclusions low mg calcite altered cloudy marine cements have variable 18o and invariant 13c values which define a trend that diverges from isotopically heavier unaltered marine cements the isotopic compositions of inclusionrich marine cement are coincident with those of meteoric phreatic spars although burial spars are present in all samples petrographic and chemical data suggest that portions of the marine cement crystals were altered by meteoric fluids the 18o values of unaltered radiaxial fibrous calcite are similar invariant throughout both reefs although marine cements from older deep parts of both reefs are enriched in 13c relative to younger shallow parts this records temporal changes in the 13c value of marine bicarbonate within the alberta basin variability of 18o and 13c values of unaltered marine cements is very small 0 5 for a given suite of samples making these cements ideal for h gh time resolution studies of the isotopic evolution of ancient oceans the presence of well preserved magnesium rich calcite from late devonian reefal sequences suggests that marine cements throughout the phanerozoic should be examined more carefully as they may preserve primary isotopic signatures independent confirmation of primary isotopic compositions is found in similar values for marine cements from middle frasnian reefs of the canning basin australia and the dinant synelinorium belgium the 18o values for the well preserved marine cements of this study are considerably lower than modern marine carbonate values by 3 to 4 detailed chemical and petrographic analysis indicates that diagenetic alteration is not the cause of these low 18o values in addition such a difference cannot be fully explained by warmer late devonian oceans these data suggest that late devonian seawater had a 18o value lower than modern oceans this in turn suggests that the balance of low temperature silicate weathering and high temperature seawater basalt exchange reactions must have been different from today s

assessment of southern ocean water mass circulation and characteristics in cmip5 models historical bias and forcing response 1 the ability of the models contributing to the fifth coupled models intercomparison project cmip5 to represent the southern ocean hydrological properties and its overturning is investigated in a water mass framework models have a consistent warm and light bias spread over the entire water column the greatest bias occurs in the ventilated layers which are volumetrically dominated by mode and intermediate layers the ventilated layers have been observed to have a strong fingerprint of climate change and to impact climate by sequestrating a significant amount of heat and carbon dioxide the mode water layer is poorly represented in the models and both mode and intermediate water have a significant fresh bias under increased radiative forcing models simulate a warming and lightening of the entire water column which is again greatest in the ventilated layers highlighting the importance of these layers for propagating the climate signal into the deep ocean while the intensity of the water mass overturning is relatively consistent between models when compared to observation based reconstructions they exhibit a slightly larger rate of overturning at shallow to intermediate depths and a slower rate of overturning deeper in the water column under increased radiative forcing atmospheric fluxes increase the rate of simulated upper cell overturning but this increase is counterbalanced by diapycnal fluxes including mixed layer horizontal mixing and mostly vanishes

the role of cementation in the diagenetic history of devonian reefs western canada devonian givetian and frasnian reef reservoirs in alberta and british columbia contain 60 of the conventional recoverable oil and 20 of the recoverable gas in the western canada sedimentary basin although the depositional history of these reefs is well understood it is the diagenetic overprint that is often responsible for their reservoir quality regardless of differences in size depositional history and age most reefs have been subjected to diagenesis in essentially three environments 1 submarine marine to hypersaline pore waters 2 subaerial fresh to brackish pore waters and 3 subsurface below phreatic aquifers saline to brackish pore waters primary porosity and permeability are altered by the overlapping processes of cementation and solution vadose and or phreatic that occur early in the diagenetic history in reef interiors these subaerial processes produce stratified reservoirs with impermeable barriers cemented beds to vertical flow e g golden spike swan hills judy creek submarine cementation is rare in most reefs but can be locally pervasive resulting in occlusion of bank margin and fore reef porosity absence of significant subsurface cementation in many reefs e g redwater golden spike aids in preservation of the reservoirs formed during earlier diagenesis

growth and demise of late carboniferous carbonate platforms in the eastern cantabrian zone asturias northwestern spain abstract geometric relationships of seismic scale stratal patterns observed on aerial photographs of late carboniferous carbonate platforms in the cuera region in asturias northwestern spain allow the identification of two discrete stages of platform development with different styles of deposition the first phase represented by the bashkirian valdeteja formation is characterized by progradation of more than 10 km with steep clinoforms of up to 35 and slope heights up to 650 m during the second phase corresponding to the moscovian picos de europa formation the platform aggraded mainly vertically nearly 850 m both phases of platform growth were terminated by major relative sea level lowstands in conjunction with local filling of the adjacent basins by shales and mudstones that onlap the platform flanks calibration with outcrops suggests a subdivision into the following lithofacies directly related to the depositional profile 1 platform interior parallel well to thick bedded skeletal pack to grainstones 2 margin algal and sponge dominated bioherms with little internal structure 3 slope clinothems of medium to thick bedded margin derived breccia beds 4 toe of slope alternating grain and packstones with spiculites and 5 basin marly shales shales sandstones and calcareous mudstones relative sea level changes caused by regional tectonic movements are suggested to be responsible for the generation of the two platform phases sea level highstands triggered the nucleation and growth of the platforms whereas major sea level lowstands in combination with terrigenous infill of the basins terminated the platform growth in addition it is proposed that the termination of late carboniferous carbonate platforms is caused by the combined effect of a sea level fall subaerial exposure and erosion and finally a rapid transgression that drowned and polluted the platform with shales and mudstones local variations in the infilling of the basins controlled the variations in the style of progradation the subsidence rates for the vertically aggrading phase picos de europa formation were approximately twice that for the progradational phase valdeteja formation and may explain the aggradational versus progradational character

unsupervised clustering of southern ocean argo float temperature profiles the southern ocean has complex spatial variability characterized by sharp fronts steeply tilted isopycnals and deep seasonal mixed layers methods of defining southern ocean spatial structures traditionally rely on somewhat ad hoc combinations of physical chemical and dynamic properties as a step towards an alternative approach for describing spatial variability in temperature here we apply an unsupervised classification technique that is gaussian mixture modelling or gmm to southern ocean argo float temperature profiles gmm without using any latitude or longitude information automatically identifies several spatially coherent circumpolar classes influenced by the antarctic circumpolar current in addition gmm identifies classes that bear the imprint of mode intermediate water formation and export large scale gyre circulation and the agulhas current among others because gmm is robust standardized and automated it can potentially be used to identify structures such as fronts in both observational and model datasets possibly making it a useful complement to existing classification techniques

the nonlinear equation of state of sea water and the global water mass distribution the role of nonlinearities of the equation of state eos of seawater for the distribution of water masses in the global ocean is examined through simulations with an ocean general circulation model with various manipulated versions of the eos a simulation with a strongly simplified eos which contains only two nonlinear terms still produces a realistic water mass distribution demonstrating that these two nonlinearities are indeed the essential ones further simulations show that each of these two nonlinear terms affects a specific aspect of the water mass distribution the cabbeling term is crucial for the formation of antarctic intermediate water and the thermobaric term for the layering of north atlantic deep water and antarctic bottom water

a wunda full world carbon dioxide ice deposits on umbriel and other uranian moons abstract carbon dioxide has been detected on the trailing hemispheres of several uranian satellites but the exact nature and distribution of the molecules remain unknown one such satellite umbriel has a prominent high albedo annulus shaped feature within the 131 km diameter impact crater wunda we hypothesize that this feature is a solid deposit of co 2 ice we combine thermal and ballistic transport modeling to study the evolution of co 2 molecules on the surface of umbriel a high obliquity 98 body considering processes such as sublimation and jeans escape we find that co 2 ice migrates to low latitudes on geologically short 100s 1000 s of years timescales crater morphology and location create a local cold trap inside wunda and the slopes of crater walls and a central peak explain the deposit s annular shape the high albedo and thermal inertia of co 2 ice relative to regolith allows deposits 15 m thick or greater to be stable over the age of the solar system we conclude that wunda located at low latitude 7 9 s and near the center of the trailing hemisphere where co 2 detections are strongest likely contains a solid co 2 ice deposit we discuss prospects for similar co 2 ice deposits on crater floors on the other major uranian moons and predict that they are present on ariel titania and possibly oberon but not miranda or smaller satellites such deposits have likely not been observed due to the limited nature of voyager 2 image coverage

marine red staining of a pennsylvanian carbonate slope environmental and oceanographic significance abstract red stained platform facies are a common feature of many carbonate settings throughout the geological record although the mechanisms involved in red staining of subaerially exposed or argillaceous peri platform limestones are reasonably well understood the environmental and oceanographic significance of red carbonates often remains uncertain here sedimentological sequence stratigraphic geochemical paleontological and quantitative bathymetric data from pennsylvanian red intervals across a well exposed carbonate platform top and slope are documented and interpreted in a process oriented context on the upper slope 80 350 meters below the shelf break red intervals alternate with gray mainly microbial algal boundstones on the lower slope 350 600 meters below the shelf break redeposited red stained mud builds matrix supported breccia tongues interbedded with predominantly redeposited clast supported carbonate debris the presence of large volumes of fibrous calcite biocementstones as well as firmgrounds point to low sedimentation rates or omission in terms of sequence stratigraphy red intervals occur within maximum flooding intervals and reflect near platform drowning elevated 18o values 2 3 and an essentially cool water heterotrophic biotic association in red intervals on platform top and slope suggest deposition during sea level highs associated with colder water masses and high nutrient levels the most likely drivers are an elevated thermocline and upwelling the red staining is the result of iron oxidation which occurred during early diagenesis likely by iron bacteria these red intervals provide an important bathymetric benchmark against which other mainly paleozoic red facies can be tested and calibrated

the thermohaline modes of the global ocean abstractthe first 2000 m of the global thermohaline structure of the ocean are statistically decomposed into vertical thermohaline modes using a multivariate functional principal component analysi

circumpolar structure and distribution of the antarctic circumpolar current fronts 1 mean circumpolar paths 1 high resolution hydrographic sections and maps of the gradient of sea surface height ssh reveal that the antarctic circumpolar current acc consists of multiple jets or frontal filaments here we use a 15 year time series of ssh observations to determine the circumpolar structure and distribution of the acc fronts the jets are consistently aligned with particular streamlines along the entire circumpolar path confirming and extending the results of an earlier study restricted to the region south of australia the intensity of the fronts as measured by the cross front gradient of ssh varies along the fronts and the individual branches merge and diverge often in response to interactions with bathymetry maps of absolute velocity at 1000 m depth derived from argo trajectories confirm the existence of multiple current cores throughout the southern ocean high resolution hydrographic sections and profiles of temperature and salinity from argo floats are used to show that the front locations derived from fitting ssh contours to maps of ssh gradient are consistent with locations inferred from the traditional criteria based on water mass properties suitably modified to account for multiple frontal branches three regions are examined in detail the crozet plateau the kerguelen plateau and the scotia sea these examples show how recognition of the multiple jets of the acc can help resolve discrepancies between previous studies of acc fronts

cool water carbonates in a paleoequatorial shallow water environment the paradox of the auernig cyclic sediments upper pennsylvanian carnic alps austria italy and its implications distinct parts of limestones within the upper paleozoic auernig group of the carnic alps austria and italy are characteristic of cool water carbonates the carnic alps were between 5 n and 10 s paleolatitude during the late carboniferous a position confirmed by dasyclad algae and fossil plants the floral association occurrence of coal seams and absence of evaporites indicate a humid tropical environment the entire section lacks abiotic components of typical warm water limestones no ooids and no aggregates occur within the auernig group parts of the limestones show surprisingly a cool water association of high diversity bryozoans brachiopods crinoids red algae sponge spicules and entomozoan ostracodes the genesis of these limestones atypical for a paleoequatorial setting cannot be explained by changes in salinity bathymetry or terrigenous input the water temperature possibly linked with upwelling nutrient supply and paleoceanographic currents is the most convincing cause of this unusual association paleoceanographic changes are interpreted as linked to contemporaneous glaciation deglaciation cycles in gondwana this paper shows that cool water carbonates in shallow water environments are not necessarily nontropical as generally interpreted future studies should consider water temperature oceanic circulation and availability of nutrients supplementary to bathymetry salinity and latitude related climate in interpretation of carbonate components

the stability and transport of carbon dioxide on iapetus abstract carbon dioxide has been detected associated with iapetus dark material by the cassini spacecraft this co2 may be primordial and or resulting from ongoing production by photolysis of water ice in the presence of carbonaceous material allamandola l j sandford s a valero g j 1988 icarus 76 225 252 although any primordial co2 would likely be complexed with the dark material and thus stable against thermal transport to iapetus poles buratti b j and 28 colleagues 2005 astrophys j 622 l149 l152 active production of co2 would result in some fraction of the co2 being mobile enough to allow the accumulation of co2 at iapetus poles we develop a computer model to simulate ballistic transport of co2 ice on iapetus accounting for iapetus gravitational binding energy and polar cold traps we find that the residence time of co2 ice outside the polar regions is very short a sheet of co2 ice near the equator of iapetus decreases in thickness at a rate of 50 mm year 1 the sublimated co2 will ballistically move around iapetus until it reaches the polar cold traps where it can be sequestered for up to 15 years if the total surface inventory of co2 exceeds 3 10 7 kg the polar ice cap will be permanent while co2 is moving around the surface a small percentage will eventually reach escape velocity and be lost from the system as such a seasonal polar cap is lost at rate of 12 every solar orbit as the co2 moves between the two polar cold traps

an exchange window for the injection of antarctic intermediate water into the south pacific antarctic intermediate water aaiw occupies the intermediate horizon of most of the world oceans formed in the southern ocean it is characterized by a relative salinity minimum with a new denser in situ national oceanographic data center dataset the authors have reanalyzed the export characteristics of aaiw from the southern ocean into the south pacific ocean these new data show that part of the aaiw is exported from the subpolar frontal region by the large scale circulation through an exchange window of 10 width situated east of 90 w in the southeast corner of the pacific basin this suggests the origin of this water to be in the antarctic circumpolar current a set of numerical modeling experiments has been used to reproduce these observed features and to demonstrate that the dynamics of the exchange window is controlled by the basin scale meridional pressure gradient the exchange of aaiw between the southern and pacific oceans must therefore be understood in the context of the large basin scale dynamical balance rather than simply local effects

water mass and biogeochemical variability in the kerguelen sector of the southern ocean a machine learning approach for a mixing hot spot author s rosso isabella mazloff matthew r talley lynne d purkey sarah g freeman natalie m maze guillaume

shell structure patterns and trends of oxygen and carbon stable isotopes in modern brachiopod shells this study investigates 13c and 18o variations in the shells of modern brachiopods representing all extant groups of calcite precipitating brachiopods collected live from 8 locations sem examinations determined the ultrastructural characteristics of each species prior to isotope analyses 13c and 18o analyses of shell carbonate were carried out with samples representing disparate morphological features and ultrastructural shell layers of both ventral and dorsal valves generally 18o values from the fibrous secondary or prismatic tertiary shell layers of the articulated terebratulida and rhynchonellida species were in oxygen isotopic equilibrium with ambient seawater isotopic temperatures extrapolated from these values are close to measured annual mean seawater temperatures 18o values were relatively unaffected by shell specialisation the only exception was antarctic species liothyrella uva which did not have a complete tertiary shell layer typical of this genus and had 18o values of the innermost layer strongly correlated with 13c and mostly not in oxygen isotopic equilibrium with ambient seawater with the exception of the rhynchonellid notosaria nigricans the outer primary layer material was depleted in 13c and 18o and highly variable inclusion of this material even as part of a whole shell sample could lead to misinterpretation of seawater temperature therefore only fossil secondary layer material should be used the anomalous articulated thecideidine brachiopod thecidellina barretti is composed of mainly primary shell material and was not in oxygen isotope equilibrium 18o values from the laminar secondary layer material of the inarticulated craniida are highly variable therefore these species are not recommended for use as palaeoenvironmental proxies this study suggests caution when employing fossil brachiopod shells with similar ultrastructures to modern craniid and thecideidine brachiopods the carbon isotope composition is highly variable in all of the brachiopods studied analysis of samples from specialised regions of the secondary shell layer show a pattern of depletion in 13c relative to non specialised secondary material the carbon isotope variability is independent of 18o and is repeated in most of the articulated species regardless of geographical location this is possibly a vital effect produced by metabolic prioritisation

antarctic bottom water production by intense sea ice formation in the cape darnley polynya antarctic bottom water fills much of the global abyssal ocean and is known to form in three main sites in the southern ocean data from instrumented elephant seals and moorings suggest an additional source of bottom water formation in the cape darnley polynya that is driven by sea ice production

iapetus surface variability revealed from statistical clustering of a vims mosaic the distribution of co2 abstract we present a detailed study of an iapetus mosaic of vims data with high spatial resolution 0 5 0 5 or 6 4 km pixel the spectra were taken in august 2007 and provide the highest vims spatial resolution data for this object during cassini s primary mission we analyze this set of data using a statistical clustering approach to reduce the analysis of a large number of data 10 4 spectra from 0 35 to 5 10 m to the study of seven representative groups accounting for 99 6 of the surface covered by the original sample we analyze the spectral absorption bands in the spectra of the different clusters indicative of different composition over the observed surface we find coherence between the distribution of the clusters and the geographical features on the surface we give special attention to the study of the water ice and co 2 bands we find that co 2 is widespread over the entire surface being studied including the bright and dark areas on iapetus surface and is probably trapped at the molecular level with other materials the strength of the co 2 band in the areas where both h 2 o and carbon bearing materials exist gives support to the hypothesis that this volatile is formed on the surface of iapetus as a product of irradiation of these two components finally we also compare the iapetus co 2 with that on other satellites confirming that there are evident differences on the center depth and width of the band on iapetus and phoebe where co 2 has been suggested to be endogenous

temperatures on europa from galileo photopolarimeter radiometer nighttime thermal anomalies galileo observations of europa s thermal emission show low latitude diurnal brightness temperatures in the range of 86 to 132 kelvin nighttime temperatures form an unexpected pattern with high temperatures on the bright ejecta blanket of the crater pwyll and an equatorial minimum in temperatures after sunset uncorrelated with surface albedo or geology the nighttime anomalies may be due to regional thermal inertia variations of an unknown origin which are equivalent to a two to threefold variation in thermal conductivity or to endogenic heat fluxes locally reaching 1 watt per square meter endogenic heat flow at this high level although consistent with some geological evidence is theoretically unlikely

an eddy permitting southern ocean state estimate abstract an eddy permitting general circulation model of the southern ocean is fit by constrained least squares to a large observational dataset during 2005 06 data used include argo float profiles ctd synoptic sections southern elephant seals as oceanographic samplers seaos instrument mounted seal profiles xbts altimetric observations envisat geosat jason 1 and ocean topography experiment topex poseidon and infrared and microwave radiometer observed sea surface temperature an adjoint model is used to determine descent directions in minimizing a misfit function each of whose elements has been weighted by an estimate of the observational plus model error the model is brought into near agreement with the data by adjusting its control vector here consisting of initial and meteorological boundary conditions although total consistency has not yet been achieved the existing solution is in good agreement with the great majority of the 2005 and 2006 southern ocean observations and better repr