the role of the tropical west pacific in the extreme northern hemisphere winter of 2013 2014 in the 2013 14 winter the eastern usa was exceptionally cold the bering strait region was exceptionally warm california was in the midst of drought and the uk suffered severe flooding it has been suggested that elevated ssts in the tropical west pacific twpac were partly to blame due to their producing a rossby wavetrain that propagated into the extratropics we find that seasonal forecasts with the tropical atmosphere relaxed towards a reanalysis give 2013 14 winter mean anomalies with strong similarities to those observed in the northern hemisphere indicating that low latitude anomalies had a role in the development of the extremes relaxing just the twpac produces a strong wavetrain over the north pacific and north america in january but not in the winter mean this suggests that anomalies in this region alone had a large influence but cannot explain the extremes through the whole winter we also examine the response to applying the observed twpac sst anomalies in two atmospheric general circulation models we find that this does produce winter mean anomalies in the north pacific and north america resembling those observed but that the tropical forcing of rossby waves due to the applied sst anomalies appears stronger than that in reanalysis except in january therefore both experiments indicate that the twpac influence was important but the true strength of the twpac influence is uncertain none of the experiments indicate a strong systematic impact of the twpac anomalies on europe

the role of linear wave refraction in the transient eddy mean flow response to tropical pacific sst anomalies the midlatitude response to tropical pacific sst anomalies involves changes in transient eddy propagation but the processes leading to the transient eddy changes are still not clear in a recent study we used a series of controlled general circulation model gcm experiments in which an imposed tropical pacific sea surface temperature sst anomaly is turned on abruptly and the response is analyzed in terms of its high and low frequency parts to show that the changes in transient eddies induced by el nino southern oscillation enso arise from changes in wave refraction on the altered mean flow in this work we use a quasi geostrophic linear model and a linear stationary wave model to interpret the gcm experiments and obtain the sequence of events that lead from a tropical sst anomaly to the quasi equilibrium change in the mean and transient atmospheric circulation the initial direct response of the mean flow is confined to the tropical and subtropical pacific similar to what is obtained from a stationary wave model this tropical subtropical mean flow change initiates a transient eddy response which induces a midlatitude mean flow anomaly the wave mean flow system evolves towards a state in which the eddy anomalies maintain the mean flow anomalies allowing them to persist it is further shown that while eddy momentum fluxes persistently accelerate and decelerate the subtropical and midlatitude mean flow the eddy heat flux effect on the zonal mean flow is much more variable and only marginally significant the linear quasi geostrophic model calculations capture the evolution of eddy momentum flux anomalies equatorwards of 60 n quite well suggesting linear wave refraction can explain the midlatitude enso anomalies however other processes like stationary waves or changes in the nonlinear stage of eddy life cycles are needed to explain the enso related anomalies at high latitudes polewards of around 60 n copyright 2010 royal meteorological society

missing aragonitic biota and the diagenetic evolution of heterozoan carbonates a case study from the oligo miocene of the central mediterranean abstract several previous studies have addressed the diagenetic evolution of heterozoan carbonate assemblages generally it is assumed that early diagenetic processes in heterozoan settings are mainly destructive including abrasion and dissolution on the sea floor constructive diagenesis cementation is delayed to later stages in the burial environment with pressure solution of calcitic grains acting as a cement source this paper presents a study of oligo miocene inner to outer ramp heterozoan carbonates from the central mediterranean maltese islands and sicily indicating that early diagenetic processes are more important than previously assumed four to five different cement types including fibrous two types of epitaxial bladed and blocky cement are distinguished based on transmitted light microscopy cathodoluminescence microscopy allowed a differentiation between primary high mg calcitic fibrous and epitaxial cement i and primary low mg calcitic epitaxial cement ii bladed and blocky cements stable isotope data indicate cement precipitation from marine marine derived and meteoric waters trace element analyses point to cementation in an open system maltese islands and a closed system sicily our investigations show that the majority of constructive diagenetic processes in these rocks occurs rather early in the shallow marine burial environment which is transitional between the marine seafloor and the deep burial diagenetic environment the main cement source in this environment is assumed to be aragonite we suggest careful consideration of the importance of aragonitic components in fossil heterozoan settings which seem to be more abundant than previously assumed and can act as a major early cement source due to the low preservation potential of these components detailed geochemical studies are necessary to detect aragonite as the cement source our findings also have implications when considering the reservoir qualities of these rocks because primary porosity can be occluded early and secondary porosity is not preserved

midlatitude atmosphere ocean interaction during el nino part i the north pacific ocean abstract atmosphere ocean experiments are experiments are used to investigate the formation of sea surface temperature sst anomalies in the north pacific ocean during fall and winter of the el nino year experiments in which the ncar community climate model ccm surface fields am used to force a mixed layer ocean model in the north pacific no air sea feedback are compared to simulations in which the ccm and north pacific ocean model are coupled anomalies in the atmosphere and the north pacific ocean during el nino are obtained from the difference between simulations with and without prescribed warm sst anomalies in the tropical pacific in both the forced and coupled experiments the anomaly pattern resembles a composite of the actual sst anomaly field during el nino warm ssts develop along the cost of north america and cold ssts form in the central pacific in the coupled simulations air sea interaction results in a 25 to 50 reduction in the magnitude of the sst and mixed layer depth anomalies

evolution of the northwestern iblean mountains sicily uplift plicocene pleistocene sea level changes paleoenvironment and volcanism the late miocene to pleistocene evolution of the northwestern iblean plateau sicily is marked by a complex interplay of subaerial and submarine volcanism subsidence and uplift eustatic sea level changes and shallow water carbonate and clay sedimentation volcanic activity occurred in distinct phases differing drastically in volume chemical composition eruptive and depositional sites and eruptive mechanisms six of the newly defined formations in the northwestern iblean plateau are either entirely volcanic or contain significant amounts of volcanics the eastern part of a shallow marine basin was filled completely by late pliocene tholeiitic lava flows militello formation that had advanced subaerially from the south southeast lava deltas advanced southwestward on top of earlier pillow breccia debris flow deposits intertongued with soft trubi marls and chalks true submarine eruptions monte caliella formation simultaneously produced densely packed pillow piles up to 250 m thick inferred water depths based on volcanologic and paleoecologic criteria of interbedded and overlying calcarenites agree well

the messinian calcare di base sicily italy revisited three different types of carbonate deposits are included within the calcare di base commonly envisaged to record the messinian salinity crisis onset type 1 consists of sulfur bearing limestones representing the biogenic product of bacterial sulfate reduction after original gypsum type 2 comprises dm thick laminated dolomitic limestones interbedded with diatomites sapropels and marls found at the top the tripoli formation type 3 the most common variety consists of m thick brecciated limestones interbedded with shales and clastic gypsum type 3 shows sedimentary features suggesting a clastic origin and deposition from high to low density gravity flows thus these deposits can be regarded as an end member of a large variety of evaporite bearing gravity flow deposits with a dominant carbonate component the genetic and stratigraphic characterization of these carbonates has strong implications for a better comprehension of messinian events the three types of calcare di base seem to have formed during different stages of the messinian salinity crisis msc type 2 formed in the first stage 5 96 5 60 ma and is the only type that can be regarded as the lower gypsum time equivalent type 3 was deposited in the second stage 5 60 5 55 ma and its base is associated with a regional scale hiatus and erosion messinian erosional surface type 1 formed even later likely in post messinian time through diagenetic processes affecting resedimented gypsum deposited during the second stage of the msc it follows that not all the calcare di base deposits record the onset of the messinian salinity crisis as commonly thought thus a detailed facies characterization of these carbonate deposits is fundamental for both stratigraphic reconstructions and a better comprehension of messinian events

tropical oceanic causes of interannual to multidecadal precipitation variability in southeast south america over the past century abstract observations atmosphere models forced by historical ssts and idealized simulations are used to determine the causes and mechanisms of interannual to multidecadal precipitation anomalies over southeast south america sesa since 1901 about 40 of sesa precipitation variability over this period can be accounted for by global sst forcing both the tropical pacific and atlantic oceans share the driving of sesa precipitation with the latter contributing the most on multidecadal time scales and explaining a wetting trend from the early midcentury until the end of the last century cold tropical atlantic sst anomalies are shown to drive wet conditions in sesa the dynamics that link sesa precipitation to tropical atlantic sst anomalies are explored cold tropical atlantic sst anomalies force equatorward flowing upper tropospheric flow to the southeast of the tropical heating anomaly and the vorticity advection by this flow is balanced by vortex stretching and ascent which drives the increased prec

impact of carbonate producing biota on platform architecture insights from miocene examples of the mediterranean region abstract different types of carbonate platforms formed in the mediterranean during the miocene low angle homoclinal types of ramp distally steepened ramps flat topped platforms and reef rimmed shelves the critical differences between these platforms result from differences in the capacities of the carbonate systems to accumulate sediments above hydrodynamic base level ecologically controlled accommodation the various depositional profiles and facies belt distributions resulted from the interplay between different sediment production and redistribution processes and the internal architectures resulted from the response of each type of platform to changes in accommodation heterogeneities driven by high frequency sea level cycles are maximized in platforms ruled by shallow water euphotic framework dominated production and minimized in low angle ramps where sediment resulted from aphotic and oligophotic carbonate production in the mediterranean region there is no direct relationship between type of platform and global temperature as shown by the coeval occurrence of different platforms in similar latitudinal settings although temperature is a key limiting factor other paleoceanographic factors such as trophic resources may have also been along with biological evolution important factors influencing different types of carbonate producing biotas

stratigraphy and sedimentology of phosphate rich sediments in malta and south eastern sicily latest oligocene to early late miocene the maltese archipelago and south eastern sicily include an uppermost oligocene to upper miocene hemipelagic sedimentary succession representing the malta hyblean plateau which limits the eastern mediterranean to the west this succession hosts a unique and well exposed series of condensed and allochthonous phosphate rich beds which were formed in a sedimentary regime of erosion sediment reworking and frequent gravity flow deposition the combination of nannofossil biostratigraphy and 87sr 86sr isotope stratigraphy allows for the precise attribution of ages to the phosphate deposits and for the distinction of three periods of major phosphogenesis the first phase occurred between 24 5 and 21 ma and 25 and 18 9 ma clustering of ages between 25 and 22 5 ma on malta and sicily respectively the second and third phases of phosphogenesis are documented from the maltese islands and are dated as 17 2 to 13 1 ma and 10 9 to 9 8 ma respectively the phosphate rich beds are associated with hiatuses and phases of important condensation which for the oldest phosphogenic period envelop the time period of 23 2 to 22 ma for the fomm ir rhi bay section malta and from 19 1 to 16 3 ma for the sections of sampieri and modica sicily for the second phase of phosphogenesis on the maltese islands a consistent hiatus was found which embraces the time period of approximately 17 to 15 ma also the third phase of phosphogenesis appears to be associated with a major hiatus which probably envelops the time period between 12 5 and 10 9 ma but a better age control is needed here the correspondence in timing of the maltese sicilian phases of phosphogenesis with major phases of phosphogenesis outside the mediterranean realm to maxima in oceanic phosphorus burial rates and maxima in the 13c benthic foraminiferal record suggests that the palaeoceanographic evolution of the eastern mediterranean was well in phase with that of other ocean basins until at least the early late miocene despite its increasing isolation due to the gradual closure of the eurasian arabian strait and progressive sea level fall

neogene coralline algal growth forms and their palaeoenvironments in the almanzora river valley almeria s e spain abstract the almanzora river valley is an elongate e w depression containing mainly neogene sediments during the late tortonian several horizons of crustose coralline algae developed in three distinct sedimentary contexts a on coastal platforms and talus slopes b on fan deltas and c associated with corals in patch reefs growing at the furthermost extremes of coastal fan deltas in the former two cases the predominant growths are as rhodoliths associated with mobile substrates in the coastal systems an increase in depth results in a change in both the morphology and the composition of the rhodoliths with depth there is a significant increase in the diversity of algal species and a concomitant increase in the size of the algal covering compared to the nucleus and thus the morphology of the rhodolith depends less and less on the shape of the nucleus itself the massive crusts and columns which mark the limit of development of the shallow water rhodoliths in the deeper examples are covered by branching and thin leafy laminar growths in the fan deltas the development of the rhodoliths is similar to that of the deeper coastal zones in the patch reefs the specific composition of the algal associations changes somewhat and the growths developed on a stable substrate under low energy conditions are mainly vertical branches arising from thin crusts

was the north american extreme climate in winter 2013 14 a sst forced response this study analyzed the possible causes of the atmospheric circulation anomalies responsible for the severe north american na climate in the winter 2013 14 the seasonal december january february mean circulation anomalies characterized by an extremely strong ridge off the west coast of na and an intense trough over the continental us appeared as a part of wave train across the north pacific na and north atlantic the lack of heating circulation response relationship in the tropics however suggested that the wave train might not be a direct response to tropical heating meanwhile dramatic month to month variations of the atmospheric circulation over the northeastern pacific excluded the possibility that the underlying sea surface temperature sst anomalies played a dominant role a further examination of monthly mean circulation patterns suggests that the wave train was initiated by a heating cooling dipole at the equatorial pacific in december 2013 and subsequently was maintained and modified by the extratropical atmospheric internal dynamics in following months the evolution of tropical heating from december 2013 to february 2014 was associated with the madden julian oscillation mjo instead of a quasi steady response to underlying sst anomalies some features of the circulation anomalies in the extratropics for the season can be captured by an atmospheric general circulation model agcm forced with observed sst but a lack of persistent heating circulation response relationship in the tropics implied a crucial role of internal variability to extreme na climate anomalies in the winter 2013 14

upstream effects of mesoscale mountains abstract the alpine experiment alpex has revealed that low level air is typically diverted around the alps without reaching the mountaintop in pursuit of an understanding of the physical basis of this phenomenon and of its generality we have explored the characteristics of orographic blocking of a rotating continuously stratified quid as revealed in a simple model problem retaining full nonlinear and transient effects hydrostatic dynamics is assumed and the obstacle is taken to be an infinitely long ridge with height h x the key questions treated are the strength of the upstream deceleration of cross mountain flow and the length scale over which the decelerated region extends by means of scale analysis the controlling parameters are found to be the rossby number ro u fl and the froude number fr nhm u where u is the speed of the oncoming flow f is the coriolis parameter l the mountain half width n the brunt vaisala frequency and hm is the maximum mountain height the scale analysis also

iblean diatremes 2 shallow marine volcanism in the central mediterranean at the onset of the messinian salinity crisis iblean mountains se sicily a multidisciplinary approach a multidisciplinary analysis of intraplate volcanic complexes interbedded with shallow and deeper marine sediments of a late miocene carbonate platform iblean plateau sicily has allowed a detailed paleo environmental reconstruction our approach includes sedimentology physical volcanology stratigraphy geochemistry mineralogy paleontology and 40ar 39ar dating four volcanic complexes are distinguished from each other two comprise an eastern shallow water platform diatreme field and carlentini complex and two a western deeper water environment representing a seamount belt on the carbonate ramp valle guffari seamount and mineo complex the late miocene volcanism was not time equivalent episodic eruptions took place from the late tortonian ca 9 38 ma at mt carrubba to early messinian ca 6 46 ma at valle guffari explosive volcanism of the diatreme field may be related geodynamically to the period of periodic sea level oscillations at the onset of the messinian salinity crisis marine diatomites preserved in the crater areas of two diatremes are the only remnants of early messinian diatomites in the eastern iblean mountains

carbonate lithofacies as paleolatitude indicators problems and limitations abstract detailed study of miocene carbonates in the mediterranean region and their analogues on modern carbonate shelves in the mediterranean sea brazil and other areas reveals at least three major types of carbonate platform lithofacies in addition to the classic tropical coral reef chlorozoan lithofacies a chloralgal lithofacies similar to the chlorozoan but without hermatypic corals b rhodalgal lithofacies characterized by abundant encrusting coralline algae and c molechfor lithofacies consisting of benthic foraminifers molluscs echinoids bryozoans and barnacles these carbonate lithofacies present complex distribution patterns seemingly related primarily to latitude and depth that control water temperature although other factors e g water circulation river discharge suspended sediment controlling water salinity and temperature nutrient content light penetration etc also play important roles chloralgal and rhodalgal lithofacies can be considered two transitional terms between the two end members the chlorozoan lithofacies which characterizes shallow tropical shelves and the molechfor lithofacies which characterizes colder and or deeper areas detailed textural and sequential analysis are required for satisfactory interpretation of these lithofacies in ancient rocks

paleobiogeography of scleractinian reef corals changing patterns during the oligocene miocene climatic transition in the mediterranean abstract during the oligocene miocene greenhouse to icehouse climatic transition the biogeography of reef corals or zooxanthellate like scleractinian corals was gradually changing from a pan tropical tethyan province in the eocene to three reef coral provinces of the western atlantic caribbean indo pacific and mediterranean our reefcoral database encompasses updated and homogenized data on paleoenvironmental and systematics of scleractinian corals occurring in the oligocene and miocene outcrops from circum mediterranean regions provided by most of relatively recently published data in the literature and by the study of published and unpublished collections of coral specimens from the same area including the important collections housed at the mnhn paris and our own collections as there is no validated direct criterion for the identification of the coral zooxanthellate symbiosis in the fossil record and considering the difficulty to use the biogeochemical approaches in the context of this study the subjectivity of the morphological criteria and the relative recent age of the fossil corals we are dealing with a uniformitarian approach has been used for inferring the symbiotic status of scleractinian genera in reefcoral among the 158 genera included in our database 93 can be considered as zooxanthellate and 10 have a doubtful zooxanthellate status this relatively exhaustive database was used to reconstruct the temporal and spatial distribution of scleractinian corals in the mediterranean during the oligocene miocene time in order to discuss the interplaying effects of the global cooling at that time the re organization of the tethyan realm resulting from the african arabian and eurasian plate collision and the emergence of the alpine chains driving the gradual northward movement of the whole region outside the tropical subtropical belt it is shown that the structure of the mediterranean z coral oligocene miocene paleobiodiversity was characterized by many geographically restricted genera with a moderate to short stratigraphical range and a few long ranging widespread genera a major consequence of this structure is that the extinction pattern has proceeded through the preferential extinction of rare occurrence genera through time the potential rapid long distance dispersal of most coral larvae compared to the size of the oligocene miocene mediterranean explains why no biogeographical subprovinces can be distinguished for the z coral fauna on a local scale ecological processes tend to sort coral taxa by limiting z coral development to geographically restricted and discontinuous areas this accounts for the large amount of geographically restricted taxa forming the mediterranean coral fauna the interaction of plate tectonics alpine orogenesis and climate at local to subregional scales exerts strong controls over the spatio temporal distribution of z coral assemblages within the circum mediterranean realm in particular we suggest that the richness and composition of the eastern atlantic coral fauna are indirectly related to the opening and closure of the eastern seaway connection with the indian ocean which controlled the e w circulation of surface waters and hence the westwards dispersal of pelagic larvae at the scale of the whole region the gradual regional climatic change produced by the northwards migration of the entire area superimposed on the global cooling appears in large part responsible for the extinction pattern of z corals through time in the mediterranean biogeographical province

adjustment of the atmospheric circulation to tropical pacific sst anomalies variability of transient eddy propagation in the pacific north america sector nas a pattern that is shifted southward northward compared with climatology paths of coherent phase propagation of transient eddies and of the propagation of wave packets are analyzed a coherent path of propagation across the pacific towards north america is identified that is more zonal during el niwinters and during la nihas a dominant path heading northeastward to the pacific northwest a second path heading southeastward from the central pacific to the tropical east pacific is more accentuated during la ni nas than el ni nos these changes in wave propagation are reproduced in an ensemble of seasonal integrations of a general circulation model forced by a tropical pacific sea surface temperature pattern confirming that the changes are forced by changes in the mean atmospheric state arising from changes in tropical sea surface temperature a simplified model with a specified basic state is used to model the storm tracks for el ni no and la ni na winters the results suggest that the changes in transient eddy propagation and the eddy statistics can be understood in terms of the refraction of transient eddies within different basic states copyright c 2010 royal meteorological society

a review of cold fronts with prefrontal troughs and wind shifts the conceptual model of a classical surface based cold front consists of a sharp temperature decrease coincident with a pressure trough and a distinct wind shift at the surface many cold fronts however do not conform to this model time series at a single surface station may possess a pressure trough and wind shift in the warm air preceding the cold front hereafter called a prefrontal trough and prefrontal wind shift respectively although many authors have recognized these prefrontal features previously a review of the responsible mechanisms has not been performed to date this paper presents such a review ten disparate mechanisms with different frontal structures have been identified from the previous literature these mechanisms include those external to the front i e those not directly associated with the cold front itself synoptic scale forcing interaction with lee troughs drylines interaction with fronts in the mid and upper troposphere and frontogenesis associated with inhomogeneities in the prefrontal air mechanisms internal to the front i e those directly associated with the structure and dynamics of the front include the following surface friction frontogenesis acting on alongfront temperature gradients moist processes descent of air ascent of air at the front and generation of prefrontal bores gravity waves given the gaps in our knowledge of the structure evolution and dynamics of surface cold fronts this paper closes with an admonition for improving the links between theory observations and modeling to advance understanding and develop better conceptual models of cold fronts with the goal of improving both scientific understanding and operational forecasting

effects of topography on fronts abstract the hydrostatic boussinesq equations are used to simulate the passage of fronts over a two dimensional mountain in a cyclic domain the fronts are forced by a confluent periodic deformation field that moves with the uniform mean flow over the mountain the initial conditions are selected to give a cold front confined to the lower part of the domain fourth order diffusion terms are included in the numerical model to control energy cascade to the grid size scale a numerical frontogenesis experiment with no topography produces a realistic surface front in about two days numerical solutions for flow over the mountain with no front are found by integrating the equations from the initial conditions which are semigeostrophic steady state solutions various mountains are considered that have the same height but different widths the numerical solutions for wide mountains remain close to the semigeostrophic initial conditions while for narrower mountains vertically propagating waves and a hydraulic

the distribution and palaeoenvironment of early miocene phosphorites of southeast sicily and their relationships with the maltese phosphorites abstract several phosphatic limestone localites occur within the irminio member ragusa formation of the western hyblean of southeast sicily in areas of maximum development such as around sampieri and modica the phosphatized intraslcast dominated deposits attain a thickness of up to 0 6m and are associated with a phosphatized underlying hardground thin and possibly discontinous spreads of phosphatized intraclast form a broader zone beyond the central semi autochthonous zone microfossil analysis of associated strata demonstrates that all occurences of phosphatized strata within the irminio member are restricted to a single level of probable late burdigalian early miocene age the bed correlates well both biostratigraphically and lithologically with the upper main phosphorite conglomerate bed of the maltese islands which lie c 95 km south of the sicilian province five more distinct phosphorite beds occur in the maltese islands being best developed in the western and northern parts of the islands they range in age from aquitanian to late burdigalian these are principally francolite replaced micrate conglomerates which may be associated with phosphatized underlying hardgrounds in places a major central mediterranean phosphatogenic province of early miocene age is postulated inorder to account for the simultaneous occurrence of phosphorites in sicily and malta

sedimentary and tectonic evolution of the eastern hyblean plateau southeastern sicily during late cretaceous to quaternary time abstract two palaeogeographic domains have been distinguished in the cretaceous quaternary sequences which crop out in the hyblean region of southeastern sicily in the northeast shallow water algal bryozoan calcarenites of oligocene miocene age overlie either cretaceous rudist limestones or volcanics further to the northeast the stratigraphic gap increases as the miocene limestone thins and in the a g i p well catania 10 plio pleistocene sediments and volcanics directly overlie upper jurassic rocks in the southwestern part of the hyblean plateau pelagic sediments occupy the cretaceous miocene interval they were deposited in a shallow basin dipping gently towards the southwest the transition between the two zones is marked by much evidence of synsedimentary tectonic activity such as widespread slumping and the development of megabreccias composed of cretaceous and eocene blocks the palaeogeographic picture is one of carbonate reefs and volcanic seamounts developing in the upper cretaceous they formed platforms fault bounded to the west and southwest from which were derived the detrital sediments found in the basin and occasional spectacular gravity slides in present day terms the structural high probably corresponds to the northeastern margin of the hyblean plateau and in part to the siracusa syracuse malta escarpment the pattern is little changed in the upper miocene with volcanoclastics of phreatomagmatic origin intercalated with coral bioherms overlying algal bryozoan calcarenites upper tortonian lower messinian limestones with a restricted fauna indicate a shallow water environment which grades up into continental conditions in the eastern hyblean plateau the tertiary sequence is capped by pliocene submarine to subaerial mafic lava flows lower pleistocene sediments consist of biocalcarenites and clays which fill deep graben delimited by plio pleistocene faults the inshore continuation of the malta syracuse escarpment system of faults from a tectonic standpoint the hyblean region a gently deformed segment of the african continental margin acted as a foreland during tertiary times a cretaceous eocene tectonic phase was responsible for the palaeogeographic pattern which existed during most of the cenozoic the present pattern is the result of three main tectonic phases following the regional upper miocene uplift of early middle pliocene plio pleistocene and middle pleistocene recent age which influenced the tectonic evolution of the present ionian coast and the malta syracuse escarpment

controls on faunal and sediment cyclicity within the tripoli and calcare di base basins late miocene of central sicily abstract cyclicity within the late miocene tripoli and calcare di base formations of sicily was controlled by two processes a partial evaporation of palaeomediterranean waters but with periodic replenishment by atlantic derived inflow on several occasions during the late tortonian and messinian stages b deformation of a regional foreland basin and associated satellite basins perched above south verging sedimentary thrust sheets these were intermittently set in motion by active plate collision onto the passive african plate margin although it is not possible to discriminate fully the world eustatic signal under such a scenario nevertheless sufficient recolonization by marine faunas in these sicilian basins occurred to permit modelling of onlap offlap events for the late miocene intervals basin wide correlation of these variably fossiliferous formations hangs on the recognition of a late tortonian early messinian onlap event marked by coral reef development at the top of the terravecchia formation around the northern margins of the region a further carbonate episode calcare di base formation lies above a transgressive surface and directly overlies fluvial conglomerates at the top of the terravecchia formation around the northern margins of the basin the calcare di base is partly diachronous with the top of the tripoli formation in the foreland basin but further north it oversteps the coral reefs on the southern margins of the madonie mountains a variable number of internal tripoli formation cycles confirmed on both faunal and sedimentological grounds and calcare di base cycles demonstrated only by sedimentation patterns have been recognized this minor cyclicity is considered to have resulted from periodic tectonic uplift and isolation of foreland basin and associated perched basins this isolation controlled both influx of siliciclastic sediment and access by marine biota prolonged basin isolation during the deposition of the tripoli formation lead to rapidly declining diversity patterns in both benthonic and planktonic communities benthonic foraminifera disappeared early in many cycles with oligotypic planktonic foraminifera and radiolaria remaining longest under increasingly hostile conditions only diatoms remained each new cycle is marked at its base by a return to near normal conditions and a relatively diverse biota although faunas were stressed during the isolation events no clear evidence of salinity increase is seen rather we consider that a combination of oxygen depletion especially on basin floors receiving prolific algal bioproduction and toxin build up generally as the by product of algal metabolic processes was the cause the calcare di base cycles are more difficult to interpret on account of the virtual absence of biota here the cycles are clearly related to desiccation and salinity increase during times of restriction the base of each cycle is marked by brine dilution and basin flooding with some evidence of low diversity microfauna input in the early cycles we envisage a late miocene palaeogeography with thrust fold belts well established to the north of sicily and a ne sw oriented seaway developed ahead of them to the south of this seaway lay an en echelon belt of ne sw oriented submarine ridges and localised basins which effected a sill or at times a barrier between the seaway and the tripoli basins a broad diatom dominated perched basin complex extended along the southern margin of the thrust related ridges and was intimately linked to a broad foreland basin also diatomitic lying immediately to the south the foreland basin was separated from a further open sea area in southern sicily by a second ne sw oriented sill now hidden by later overthrusting it is suggested that similar tectonic scenarios were responsible for isolating diatomaceous basin elsewhere in the mediterranean during late miocene times

integrated planktonic foraminifera bolboforma and carbon isotope stratigraphy in a mid early late miocene carbonate ramp setting from the acreide area sicily taxa of bolboforma a marine calcareous microfossil group of uncertain origin with affinities to protophytic algae are generally used for biostratigraphy of lower eocene to lower pleistocene marine sediments from high latitudes biostratigraphy based on bolboforma has been applied only rarely to european outcrop sections and very rarely to mediterranean sections three bolboforma and two planktonic foraminifera events are identified and used to interpret the sedimentation rate of the 90 m of slope sediments from the palazzolo section palazzolo acreide area sicily and spanning the interval from 11 9 to approximately 10 5 ma carbon isotope stratigraphy supports the age assigment based on bolboforma and planktonic foraminifera in particular the sediments of the palazzolo section seem to record the latest pulse of the monterey event a major perturbation in the global carbon cycle related to global intensification of upwelling expanded use of the bolboforma may thus improve stratigraphy in outcropping miocene sequences in temperate regions particularly in shallower water facies with poorly resolved planktonic foraminifera and nannofossil stratigraphy

discrete frontal propagation over the sierra cascade mountains and intermountain west abstract on 25 march 2006 a complex frontal system moved across the sierra cascade mountains and intensified rapidly over the intermountain west where it produced one of the strongest cold frontal passages observed in salt lake city utah during the past 25 yr observational analyses and numerical simulations by the weather research and forecast wrf model illustrate that the frontal system propagated discretely across the sierra cascade mountains and western nevada this discrete propagation occurs in a synoptic environment that features a mobile upper level cyclonic potential vorticity pv anomaly that is coupled initially with a landfalling pacific cyclone and attendant occluded front the eastward migration of the upper level cyclonic pv anomaly ultimately encourages the development of a new surface based cold front ahead of the landfalling occlusion as troughing confluence and convergence downstream of the sierra nevada intensify preexisting baroclinity over nevada trajectories show that the n

miocene phosphate rich sediments in salento southern italy abstract the upper middle to lower upper miocene serravallian to tortonian sedimentary succession in salento southern italy includes glauconite and phosphate rich deposits which are associated with pelagic micrite in baia del ciolo and marittima southern salento the succession is composed of shallow water platform carbonates of late oligocene age chattian porto badisco formation which are overlain by a 20 to 30 cm thick level of glauconite rich micrite with abundant reworked particles and fossils of the underlying porto badisco formation this interval is in turn covered by an up to 15 cm thick phosphatic crust livello ad aturia which itself is overlain either by a hemipelagic chalk like carbonate of middle to late miocene age pietra leccese marittima or directly by a micrite of late miocene age messinian novaglie formation baia del ciolo which shallows upwards into a shallow water platform carbonate a large hiatus is present in this succession which likely includes the lower and lower middle miocene in the region of lecce two discrete levels enriched in glauconite and phosphate each associated with a major discontinuity occur within the pietra leccese the strontium isotope ages derived on phosphate nodules and phosphatized and non phosphatized fossils and calcareous nannofossil ages indicate a time interval of phosphogenesis between 13 5 and 7 5 ma with two clusters at 12 and 10 5 ma the glauconite and phosphate rich sediments resulted from a current dominated regime which was characterized by low overall sedimentation rates erosion and sediment reworking and authigenesis this regime was likely related to a generally westward directed bottom current which was forced to upwell once it arrived at the western border of the eastern mediterranean basin the timing of the principal phosphogenic phases can only partly be correlated to those of other occurrences in this part of the mediterranean malta gozo southern sicily matese latium abruzzi platform the partial diachrony in phosphogenesis may express the effect of lateral switching in and or focusing of upwelling zones

late tortonian lower messinian miocene palaeogeography of se sicily information from two new formations of the sorting group abstract a thick volcanoclastic biohermal and lagoonal sequence of strata succeeds the siracusa limestone member monti climiti formation of se sicily this overlying sequence may be divided into two new formations on the basis of lithostratigraphy petrology and palaeontology the older formation here named the carlentini formation is predominantly a thick volcanoclastic sequence but with two intervening carbonate horizons faunas are rare within the volcanic strata but may be abundant and associated with corals and patch reefs within the two carbonate levels the younger formation here named the monte carrubba formation is almost exclusively composed of oolitic grainstones and lagoonal wackestones peritidal carbonates are developed in the northeast of the area faunas are frequently of low diversity euryhaline mollusc associations are dominant although pecten vigolenesis occurs in the lower beds collectively the new formations span the late tortonian lower messinian time interval and may be correlated with the calcare di base of the main sicilian basin to the west the palaeoenvironmental reconstruction suggests that both formations were deposited around the sw margins to a low island or landmass lying to the north of the hyblean region

bio retexturing early diagenetic fabric modifications in outer ramp settings a case study from the oligo miocene of the central mediterranean abstract bioturbation is ubiquitous in cenozoic outer ramp settings the oligo miocene ramp carbonate sequences of se sicily and the maltese islands provide specific examples to illustrate the effects of sediment retexturing by burrowers and provide significant conclusions which must be taken into account by sedimentologists when interpreting palacoenvironments thalassinoidean burrow systems may penetrate several metres into the underlying beds with evidence of concentrated activity at selected levels the general intra bed process of this crustacean dominated bioturbation is well documented however the effects when several beds are involved can be dramatic 1 a buried homogeneous wackestone beds can be depleted in lime mud by gallery excavation the dumping of this mud at the sediment surface leads to lime mud enrichment of the contemporary accumulating layer and might be a major factor in the development of the tabular outer ramp bedforms 2 b vertical reworking of unlithified sediment between beds both upwards and down is capable of homogenising two distinctly dissimilar lithologies producing a third which in no way reflects the surface processes of the depositional setting 3 c bioturbation often continues during incipient near seafloor lithification this produces random lateral variations in lithology within single beds the degree of lateral dissimilarity is proportional to the intensity longevity of the bioturbation episode bio retexturing destroys primary depositional fabrics and masks inorganic process related structures it can be as effective a remodelling agent as tidal energy it can texturally remodel areas of high primary permeability into irregular interconnected zones of low permeability as the outer ramp provides a potential fluid migration route from basin to shallow water clearly bio retexturing must exert a major influence on longer term formation wide diagenetic processes

magma serpentinite interaction as the origin of diatremes a case study from the hyblean plateau southeastern sicily some diatremes formed in the hyblean plateau in a time span from 6 5 to 9 4 ma producing volcaniclastic deposits which host deep seated xenoliths the origin of the explosive activity that has brecciated the magma and the country rocks is controversial two are the prevalent models phreatomagmatic and magmatic brecciation we propose an alternative explanation based on the thermal and mechanical interaction of a rising basaltic magma with serpentinized mantle rocks representing the main lithologies in the permo triassic hyblean basement we suggest that magma serpentinite interaction could have remobilized fluids from serpentinites that reached the overpressure necessary for the brecciation of country rocks the possible depth of this interaction has been estimated considering variations of porosity and permeability at different depths in the hyblean lithosphere these properties have been taken into account in the dimensionless parameter v e jamtveit et al in physical geology of high level magmatic systems vol 234 geological society london special publications london pp 233 241 2004 which reflects the relative rates of heat and fluid transport since a high fluid flux is enhanced by a high boiling temperature of pore water raised by magma rock heat exchange v e remains less than 1 up to a depth of 7 km corresponding to the average thickness of the sedimentary volcanic sequence characterized by a high permeability k 10 12 10 14 m2 that inhibits fluid overpressure built up in contrast to both phreatomagmatic and magmatic models at deeper levels k 10 19 m2 from 8 km downward the value of v e is greater than 1 therefore we propose that the dehydration of serpentinites upon heating by hot basaltic magma would have liberated huge amounts of fluids whose accumulation at an average depth of 8 km beneath the impermeable serpentinized level induced supercritical fluid overpressure strong enough to exceed the lithospheric pressure fluid overpressure caused the opening of fractures in the overlying permeable upper crust triggering the energetic fluid expansion and hence the brecciation of country rocks finally we suppose that aforementioned conditions for supercritical fluid overpressure could have been gained in other areas of the hyblean region in coincidence with various mesozoic volcanic events even though older diatremes may have been obliterated by subsequent sedimentary cycles and volcanic events as well as in serpentinite diatremes in the navajo volcanic field colorado plateau sw usa

terrain influences on synoptic storm structure and mesoscale precipitation distribution during ipex iop3 abstract the influence of topography on the evolution of a winter storm over the western united states and distribution of precipitation over northern utah are examined using data collected during the third intensive observing period iop3 of the intermountain precipitation experiment ipex the analysis is based on high density surface observations collected by the mesowest cooperative networks special radiosonde observations wind profiler observations next generation weather radar nexrad data and conventional data a complex storm evolution was observed beginning with frontal distortion and low level frontolysis as a surface occluded front approached the sierra nevada as the low level occluded front weakened the associated upper level trough moved over the sierra nevada and overtook a lee trough the upper level trough which was forward sloping and featured more dramatic moisture than temperature gradients then moved across nevada with a weak surface reflection as a pressure trough over no

influence of mesoscale orography on idealized cold fronts abstract a three dimensional numerical model based on the inviscid and adiabatic primitive equations in the boussinesq approximation is used to investigate the retardation of cold fronts by high two and three dimensional mountains approximately the same size as the alps initial and boundary conditions are specified according to an analytical model for an idealized front with constant potential vorticity the study covers cases with uniform neutral or stable stratification in both the cold and warm air masses the model results are compared with previous analytical solutions of a shallow water flow model a scale analysis and a parameter study identify the conditions under which a front is strongly influenced by mountains for two dimensional cases the study shows that the foot of the front is strongly retarded if the kinetic energy is too small to let the cold air climb over the mountain the bulk of the front is strongly retarded if the froude number and the relative front mountain height are small

carbonate ramp depositional systems abstract the classification tectonic settings stratigraphy and early diagenesis of carbonate ramp systems are reviewed carbonate ramps are common in all geological periods but were dominant at times when reef constructing organisms were absent or inhibited ramps can be subdivided into inner mid and outer ramp environments the mid ramp zone extends from fair weather wave base to normal storm wave base although the water depths which these boundaries represent vary an additional outer slope environment occurs on distally steepened ramps as with siliciclastic shelves a range of wave storm and tide dominated ramps can be recognised and this forms the most convenient basis for ramp classification the carbonate productivity profile of ramps differs from that of rimmed shelves with the inner ramp showing lower production rates than comparable shallow water facies on rimmed shelves the zone of greatest organic carbonate sediment production appears to have shifted from the mid ramp to the inner ramp since the late jurassic carbonate ramps occur in most types of sedimentary basin but are best developed where subsidence is flexural and gradients are slight over large areas as in foreland and cratonic interior basins and along passive margins the featureless depositional profiles of many ramps means that sequence geometries are best observed on regional seismic lines some show low angle sigmoidal or shingled clinoforms suggesting that ramps may seldom be homoclinal but possess subtle slope geometries which reflect depositional environments because of their low angle slopes ramps respond differently to rimmed shelves during relative sea level changes although results seem to be strongly dependent on the rate of relative sea level change during a minor fall shallow ramp facies belts will simply shift basinwards in a forced regression in contrast the whole surface of a steep sloped flat topped rimmed shelf may be exposed so that sediment production ceases or is drastically reduced during a major fall shallow ramp bounded basins may empty completely conversely ramps also flood gradually whereas rimmed shelves do so more rapidly homoclinal ramps develop no resedimented lowstand deposits rimmed shelves and distally steepened ramps in contrast may develop lowstand talus or turbiditic wedges distally steepened ramps may behave more like homoclinal ramps during minor base level falls and like rimmed shelves during major base level falls many ramps consist of layered successions of several ramp sequences stacked one upon the other ramp stacks of this sort may show gross vertical accretion but individual ramp sequences seldom appear to develop in a keep up style apart from minor organic buildups as with many rimmed shelves steepening of the outer ramp margin due to tectonism slope inheritance or differential sedimentation may promote the development of a distally steepened ramp or rimmed shelf a wide variety of organisms have constructed buildups in mid and outer ramp environments isolated buildups may seed early in ramp development accrete to wave base or sea level and continue growth by stacking through successive ramp sequences so that depositional and diagenetic features within them are in concert with those of the shallow ramp the location of isolated buildups on ramps is governed by tectonism halokinesis antecedent topography or by the subtle slope geometry of the previous ramp sequence diagenesis on ramps shows some major variations compared with diagenesis on steep sloped flat topped carbonate platforms ramp bounded basins may form prolific petroleum sourcing and reservoiring systems and offer a range of subtle stratigraphic play types and lateral facies variations which determine reservoir quality and distribution isolated buildups in the mid and outer ramp environments represent one of the commonest petroleum reservoirs in ramp systems and tend to have their foundations in transgressive systems tracts grainstone and packstone reservoirs are widespread and range from shoreline carbonate sandbodies to major detached shoal complexes or shoals over offshore highs grainstone sandbodies occur in both highstand systems tracts and in prograding lowstand wedges

gravity slide and resedimentation processes in a miocene carbonate ramp hyblean platcau southeastern sicily abstract more than twenty sharp based channel form structures occur in the miocene palazzolo formation carbonates within a distally steepened se sicilian miocene carbonate ramp contemporaneous biota indicate deposition in water depths of 70 150 m fully exposed structures commonly exceed one kilometre along palacostrike their bases are concordant with the host strata but these steepen to 15 in proximity of their margins internal bedding planes generally are concordant with the basal truncation surface the lithologies of the channel fills are similar to the host sediment there is little evidence that these structures are erosional since they contain neither breccias nor turbidites rather they are interpreted as the product of gravitational sliding involving thin detached sheets of consolidated ramp carbonates the resulting irregular topography was draped by redeposited fine grained carbonate sediments once healed and further oversteepened renewed gravity sliding occurred this resulted in a 250 m thick slide dominated succession in a zone 4 km wide located between the outer ramp apron comprised of coralline algal and foraminifera rich sediments and basin margin pelagic marls this phenomenon although unusual in shallow water settings is well known from modern continental slope environments sliding was probably triggered by seismicity in the region associated with two known mesozoic basement faults an alternative hypothesis involving pressure gradient build up along distally steepened ramp zones during storm surges is dismissed as a cause although this mechanism may have facilitated resedimentation of seafloor sediments over the slide zone

tectonic analysis of a flexed foreland the ragusa platform abstract detailed field studies of fracture patterns and paleostress reconstructions based on analyses of fault slip data sets allow the identification of the late cenozoic stress pattern evolution of the ragusa platform during the late miocene to early pleistocene period a complex extensional pattern developed it was dominated in almost the entire hyblean plateau by nw se to nnw sse extensions related to the flexure of the foreland under the load of the allochthonous units of the sicilian fold and thrust belt these extensional tectonics were characterized by ne sw to ene wsw trending normal faults and grabens in eastern hyblea ne sw to ene wsw extension have prevailed at least since the late cretaceous they are linked to the effects of the malta escarpment in the western ragusa platform a third minor wnw ese extension associated with sets of nne ssw trending normal faults may be correlated with the development of the gela basin in addition these major extensions induced complex patterns of perpendicular normal fault systems through permutations between the principal stress axes 2 and 3 the pliocene pleistocene extensional paleostress field evolution is marked in almost the entire platform by the alternation of two or three main extensional stress patterns ne sw to nnw sse wnw ese and ne sw to ene wsw extensions each of them controlled by particular boundary conditions three minor compressional paleostress orientations have been identified they correspond to three minor compressional events dominated by 020 030 070 080 and 100 110 compressional directions these events occurred in within the general pliocene pleistocene extensive context the 100 110 event is of early middle pliocene age its large regional distribution suggests that this event may have resulted from interactions between the major blocks constituting the africa eurasian boundary the relative chronology shows that the 020 030 compression predates the 070 080 one the origins of these compressional events are still uncertain due to poor regional control

phosphorites hardgrounds and syndepositional solution subsidence a palaeoenvironmental model from the miocene of the maltese islands abstract two major phosphorite conglomerate horizons occur throughout the central mediterranean maltese islands within the lower middle miocene globigerina limestone formation the lower conglomerate lies directly upon a hardground and both conglomerates include lithoclasts of hardground material variation in clast size and bed thickness indicates a source area to the west and north of the present day islands of malta and gozo particularly thick phosphorite conglomerates occur in solution subsidence structures in western gozo being developed as a result of synsedimentary seafloor collapse these structures indicate that phosphorite clasts were deposited during several discrete pulses of turbulence punctuated by periods of non depositional hardground formation or normal marine pelagic sedimentation geochemical analysis of the contained phosphorite clasts within the conglomerates shows that p 2 o 5 generally is concentrated around the outer margins of the pebbles and contributes up to 17 by weight of some samples some 654 580 m 3 and 837 870 m 3 of phosphorite bearing strata are contained within the xlendi and qawra subsidence structures respectively the maltese islands represent part of a miocene carbonate shelf whose margin lay nearby to the west and which was subject to periodic erosion by strong currents transporting phosphorite pebbles eastwards to their present sites these currents further contributed phosphorus to semi autochthonous phosphorite developments located within the present maltese area the maltese phosphorites are related to other phosphorite areas in sicily a major province of miocene phosphogenesis is proposed to account for these occurrences it extends along the western margins of the malta ragusa rise

syndepositional tectonics affecting cenozoic and mesozoic deposition in the malta and se sicily areas central mediterranean and their bearing on mesozoic reservoir development in the n malta offshore region abstract tertiary sedimentation patterns within the maltese islands and se sicily pelagian block of the central mediterranean reflect subtle depositional control by the concurrent evolution of the malta graben lying to the south west and reactivation of regionally important mesozoic fault systems the visible structural style of the maltese islands is the product of malta graben development and commenced some 24 million years ago however north south oriented structures identified from maltese tertiary facies strike patterns can be closely related to reactivated mesozoic faults in se sicily here synsedimentary tectonogenesis is recognized in both mesozoic and cenozoic strata mesozoic synsedimentary faulting was initiated during a former tectonic regime when the pelagian block african plate lay at the southern side of a wide tethys ocean reactivation of these fractures during the tertiary is believed to be related to subsequent african european plate collision the unsuccessful oil search in maltese territorial waters results from the mistaken significance attached to the young malta graben related tectonic pattern of the maltese islands potential traps are more likely to be associated with a cryptic though formerly dominant mesozoic tectonic pattern the hypothesis presented predicts hydrocarbon prospects in horst traps immediately to the north of the malta shelf these can be expected to show many of the characteristics of the gela and ragusa fields

the monte carrubba formation messinian sicily and its correlatives new light on basin wide processes controlling sediment and biota distributions during the palaeomediterranean mediterranean transition abstract a little known marine miocene messinian succession in the hyblean region of south eastern sicily preserves a carbonate ramp sequence which developed on the tectonically stable foreland margins of the african plate pelagian block the ramp monte carrubba formation was distally steepened and contained a shoalwater barrier and lagoonal inner ramp complex the outer ramp is poorly preserved though distal deep water ramp facies tellaro formation in the south hyblean region preserve a full globorotalia mediterranea subzone and major part of the globigerina multiloba subzone succession this ramp sequence faithfully records the subtle interplay between the global eustatic curve and internal palaeomediterranean base level signatures for the late miocene the earliest second order palaeomediterranean lowstand occurred in the late tortonian at about 7 3 ma and a second occurred at about 6 75 ma within the early messinian g mediterranea subzone both were in the order of 40 m and global sea level was probably restored to the palaeomediterranean after the lowstands although the overriding control at the time was the global eustatic curve harmonic discrepencies between it and the palaeomediterranean curve resulted from constriction of the atlantic connection during the latest tortonian from about 6 4 ma until about 5 96 ma increasingly restricted conditions developed across the monte carrubba inner ramp these faithfully reflect many second order constriction driven palaeomediterranean sea level oscillations which were superimposed on to the falling global signal as the connecting atlantic seaways became constricted these oscillations resulted in major reductions in planktonic faunal diversity within the outer ramp followed by total emergence of the inner ramp by about 6 05 ma marine deposition continued until about 5 96 ma in the southern part of the hyblean region however between 6 05 ma and about 5 6 ma the amplitude of successive palaeomediterranean sea level oscillations increased to over 100 m causing prolonged periods of total palaeomediterranean isolation the hyblean carbonate suite also contains post messinian salinity crisis post msc lago mare highstand deposits which are developed unconformably above the monte carrubba formation the widespread distribution of hyposaline to near marine congeria faunas within the lago mare episode argues for high post msc mediterranean water levels in the central mediterranean late messinian in this article we draw together disparate regional evidence from this stable foreland setting and assimilate it with published data from regions lying on the european plate in order to demonstrate that the tectonically stable monte carrubba succession provides an unambiguous record of central palaeomediterranean base level change during the messinian furthermore the post msc sequence demonstrates a prolonged mediterranean base level rise throughout the late messinian leaving little readjustment necessary in order to restore mediterranean base level to global water levels in basal pliocene times

the petrology and palaeoenvironment of the sortino group miocene of se sicily evidence for periodic emergence the sortino group of carbonates consists of three formations which developed on a shallow marine shelf during tortonian and lower messinian times the two lower formations contain three bioherms and are intercalated with thick volcaniclastic sequences the youngest formation is dominated by shoal water lagoonal and peri tidal carbonates early submarine lithification is well developed within the bioherms and consists of construction by both algae and invertebrates the development of peloidal micrites and isopachous fringe growth superimposed upon these are a series of both meteoric phreatic and vadose textures related to episodic emergence of the bioherms these features include bladed cements showing cathodoluminescence pendent cements brecciation alveolar texture and palaeosols the sicilian strata may be directly correlated with the maltese islands sequence and collectively exhibit the effects of fluctuating mediterranean sea levels at an early stage in the late miocene salinity crisis

compounding effects of warm sea surface temperature and reduced sea ice on the extreme circulation over the extratropical north pacific and north america during the 2013 2014 boreal winter unprecedented atmospheric circulations with extreme weather were observed in the extratropical northern hemisphere during the winter of 2013 2014 the anomalous circulations were the manifestation of the pacific pattern or the north pacific oscillation western pacific pattern but with extremely large amplitude simulation results suggest that the anomalous atmospheric circulations were constructively induced by anomalous sea surface temperature in the tropical pacific and extratropical north pacific as well as the low sea ice concentration in the arctic natural variability played a major role in inducing the anomaly pattern whereas the anomalously warm sea surface temperature and low arctic sea ice concentration in the bering sea contributed to the intensity if the anthropogenic warming has a significant impact on causing the synchronization of the aforementioned anomalies in sea surface temperature and sea ice concentration and this trend continues severe winters similar to that in 2013 2014 may occur more frequently in the future

sedimentology and palaeoenvironment of the southeast sicilian tertiary platform carbonates abstract a thick succession of shelf and shelf slope carbonates is developed in southeastern sicily sedimentological aspects of the oligocene to tortonian sequence including distribution and palaeoenvironmental factors are considered a new formation and four new members are proposed in the upper part of the succession the region comprises a western half typically exhibiting the principal deeper water planktonic facies including marls and an eastern area displaying typically inner shelf carbonates and an attenuated succession coralline algal limestones and calcarenites are more typical of this latter region but there are also some volcanic intercalations an attempt is made to relate the hyblean succession to that of the maltese islands which lie at the southern end of this tertiary carbonate platform

frontal interaction with the appalachian mountains part i a climatology abstract a comparison between the climatological structure of retarded and unretarded fronts aligned parallel to the appalachian mountains is investigated with the average height of the appalachians being 1 km retarded and unretarded fronts are common occurrences during the cold season because of the narrow half width of 100 km and the 1000 km length of the mountain chain a comparison to two and three dimensional numerical studies can be performed of the 142 cases of frontal passages over the appalachians during the winters between october 1984 and april 1990 over 55 of all cold fronts were retarded by the mountains statistical analysis showed that retarded fronts have a stronger cross front temperature gradient and a weaker cross front pressure gradient composite fields of sea level pressure 850 500 and 200 mb heights quasigeostrophic potential vorticity and its advection and potential height u n were computed for all retarded and unretarded fronts unretarded fronts were associated wi

active fault kinematics and crustal stresses along the ionian margin of southeastern sicily since the late cretaceous onset of plate convergence between africa and europe the malta escarpment has been converted from a mesozoic passive margin into a mega hinge fault system with an additional sinistral strike slip component the modern tectonic stress regime with nw se directed maximum horizontal stresses has been established since late messinian times since the pleistocene sinistral strike slip deformation and contemporaneous normal faulting along the malta escarpment have induced the opening of oblique trending onshore grabens at the eastern margin of the hyblean plateau in this study we focus on the kinematics the controlling state of stress and the temporal variation of the neotectonic to active strike slip and normal fault structures the stress tensor calculations reveals that the widespread map scaled to meso scaled normal fault structures are governed by the long term extensional state of stress during the quaternary this long term stress tensor is predominantly controlled by gravitational induced stresses due to vertical load 1 sv and lateral extension due to the topographic gradient of the malta escarpment 3 sh ne sw in this case the average tectonic stresses 2 sh nw se transmitted by the regional to plate tectonic stress field are significantly smaller than the gravitational induced stresses in contrast the clear localization of conjugate sets of meso scaled strike slip fault structures and shear zones without accompanying normal fault structures give strong indications for episodic seismotectonic strike slip faulting under critical stress conditions in this state tectonically induced maximum horizontal stresses are successively increased by ongoing plate convergence from low level stress magnitudes 1 sv 2 sh nw se up to critical stress magnitudes 1 sh nw se 2 sv which are significantly larger than gravitational stresses at the critical state seismotectonic stress release occurs by active strike slip faulting as recently indicated in mid crustal levels by the moderate 1990 augusta earthquake and re establishes the long term extensional state of stress because the strike slip faults and shear zones in the study area were formed as surface ruptures they additionally give indications of episodic large earthquakes in this region with magnitudes greater than 6 0 as reported by several large earthquakes devastating e and se sicily in historical times

messinian reef building assemblages of the salento peninsula southern italy palaeobathymetric and palaeoclimatic significance abstract this paper mainly addresses the description and interpretation of different reef building assemblages recognised within an early messinian reef complex recently discovered along the eastern margin of the apulia platform salento peninsula southern italy it is the first late miocene reef recorded for the adriatic region and its location partly changes boundaries of coral reef distribution during this time in the mediterranean the messinian reef complex novaglie formation is interpreted as a succession of fringing reefs accommodated in palaeo reentrances or palaeo embayments of the original messinian rocky shore and overlying discordantly the underlying cretaceous to oligocene units it consists of a discontinuous reef tract and associated clinostratified fore reef slope relatively precise dating of the reef complex has been achieved using benthic foraminifera and ostracods associations three main different reef building assemblages have been recognised 1 halimeda bioherms 2 porites reef and 3 vermetid microbial trottoirs each assemblage is described in detail according to its architecture and structure setting shape quantitative estimation of the framework density biotic components taxonomic composition and relative abundance of the reef builders growth form associated fauna and intra reef sediment texture and fabric palaeoecologic analysis based on physical observation within the margin slope of the reef complex and in comparison with present day analogues and their ecological demands indicates that distribution and vertical succession of the three different reef assemblages are strictly depth related suggesting an ecological replacement consequent on small relative sea level changes fourth order closely comparable with those already indicated for the early messinian special attention is given to the remarkable abundance of vermetids that together with microbial crusts formed scattered trottoirs along the shoreline vermetid occurrences have been extensively cited in the literature for the late miocene of the mediterranean but poorly studied in detail here their palaeoecologic significance is emphasised indicating that these organisms can be used as reliable palaeobathymetric and palaeoclimatic indicators regarding the miocene of the mediterranean development of vermetid microbial reefs so far recorded for the messinian is preferentially associated with low diversity coral reefs and is interpreted as being mainly controlled by climatic constraints

influence of pore system characteristics on limestone vulnerability a laboratory study hyblean limestone of oligo miocene age was widely used as a construction material in the architectural heritage of eastern sicily italy among them the so called pietra bianca di melilli melilli limestone and calcare di siracusa syracuse limestone were prized for their attractive appearance ease of quarrying and workability syracuse limestone shows general weathering whereas melilli limestone is better preserved and only differential erosion or superficial exfoliation can be detected in monuments the cause of the different behavior of these two limestones was investigated from the petrographic and petrophysical points of view the saturation coefficient is higher in melilli limestone and ultrasound measurements indicate that it is less compact than syracuse limestone so that melilli limestone could deteriorate more easily than syracuse limestone however pore interconnections and the size of very small pores play the main role in the durability of both materials the irregularity of the syracuse pore system and its greater number of micropores hinder water flow through the exterior promote stress in pore structure and favor the development of scaling as confirmed by salt crystallization tests in melilli limestone the low concentration of micropores and fast water evaporation allow solutions to reach the surface more easily resulting in less damaging efflorescence

vermetid reefs and their use as palaeobathymetric markers new insights from the late miocene of the mediterranean southern italy crete abstract vermetids are a poorly known family of reef building gastropods characterized by an extremely irregular growth of the shell vermetid reefs are known from the badenian middle miocene to present day and their main importance is related to their use as sea level indicators strictly associated to the intertidal or immediate subtidal zone during their evolution two different vermetid genera have been recognized as reef builders petaloconchus was the major component of vermetid reefs until the holocene when for still unknown reasons it was almost completely replaced by dendropoma in the mediterranean basin petaloconchus reefs have been frequently found in close association to late miocene coral bioconstructions new finding of petaloconchus reefs within the slope facies of the salento messinian reef complex southern italy together with new data from late tortonian early messinian reefs of crete greece provide further information on the palaeoecology of these peculiar bioconstructions stratigraphical and sedimentological contexts of salento and crete vermetid reefs have been described together with an account of their size shape and inner structure biotic vermetids serpulids bryozoans and coralline algae and abiotic components early marine cements and intra reef sediment have been identified by microfacies analysis and their percentage abundance has been reported these data allow the description of vermetid reefs from two different depositional settings along the shelf edge and for the first time within the coral reef slope shelf edge and slope petaloconchus reefs show the same inner structure and composition but they differ by their shape by the density of the framework and by the relative proportion of the associated reef building organisms serpulids bryozoans and coralline algae additional information on their palaeobathymetric setting have been acquired from the presence of other reef building biota porites corals and halimeda green algae which occur in close proximity to slope vermetid reefs together with observations on some anatomical feature of petaloconchus shells results clearly indicate for petaloconchus reefs a palaeobathymetric range spanning from the upper subtidal zone down to 30 50 m of depth the present study confirms vermetid reefs as important tools for the reconstructions of ancient sea level but great attention has to be paid to the identification of the main reef building vermetid actually while a great number of present day dendropoma reefs can be associated to the mean sea level late miocene vermetid reefs from salento and crete indicate for petaloconchus bioconstructions a wider palaeobathymetric range

winter midlatitude cold anomalies linked to north atlantic sea ice and sst anomalies the pivotal role of the potential vorticity gradient abstractthis study establishes a linkage between the north atlantic sea ice concentration sic or sea surface temperature sst and cold anomalies over northern europe and north america through th

the circumglobal north american wave pattern and its relation to cold events in eastern north america extreme large scale north american cold events are associated with strong undulations in the tropospheric jet stream which bring cold polar air southward over the continent here we propose that th

plio quaternary tectonic evolution and structure of the catania foredeep the northern hyblean plateau and the ionian shelf se sicily abstract available multi and single channel seismic reflection profiles calibrated by onshore borehole data have been used for defining the structural styles in the shelf and slope of the ionian sea between catania and augusta se sicily the geological and geophysical data suggest that this area represents a segment of the foredeep foreland system which collapsed after late pliocene times the foundering was controlled by normal faults trending ne sw which flank the southern margin of the catania foredeep onland in outcrop these faults appear largely to be post dated by lower pleistocene sediments nearshore carbonates passing laterally into basinal clays which lie unconformably upon older substrata offshore close to the southern edge of the foredeep seismic lines allow recognition of two distinct units a syn rift wedge upper pliocene submarine tholeiites and sediments and a post rift sequence which can be correlated with lower pleistocene carbonates sands and clays recognisable on land both in outcrop and by borehole data the true frontal part of the thrust belt as detected by the seismic lines occupies the inner part of the area investigated and is buried by upper pliocene and lower pleistocene sediments however the compressive deformation seems to propagate toward the south southeast by means of growing detachment levels developing at depth within pleistocene marine clays for a length of about 10 km ahead of the present day thrust front offshore the faults trending ne sw are dissected towards the east by faults trending nnw sse subparallel to the malta escarpment which flank the edge of the submerged messina rise these faults originating in a steep scarp which drops eastwards to the deep ionian basin have triggered submarine slides and affected the present day seafloor sediments as shown by seismic lines and as stressed by the modern seismicity of the area some of the faults along the malta escarpment could be still active

a geological and paleomagnetic study of the hyblean volcanic rocks sicily abstract the geological and paleomagnetic study of the hyblean volcanic rocks in southeastern sicily permits the following conclusions 1 1 the upper cretaceous volcanics are considerably more extensive than earlier studies indicated they stretch from north of augusta to the vicinity of siracusa their magnetization is identical to that of the better known outcrops around capo passero of the two new age dates reported here one is younger than any so far reported 2 2 the upper tortonian flows are normally magnetized suggesting a correlation of the carlentini formation with magnetic interval 7 the flows at the top of the tellaro formation are also normally magnetized and are tentatively correlated with the carlentini formation flows shorter reversed intervals within interval 7 may be represented by two less well dated flows 3 3 the lowest pliocene flows have an adequate stratigraphie control and their magnetization is consistent with the extrusion of the pillow lavas during the mammoth event the militello flow sequence together with the francofonte flows appear by indirect argument to lie within the oldest reversed interval i e pre kaena of the matuyama epoch the individual flows in which both normal and reversed directions have been found cannot be assigned positions in magneto stratigraphie scale 4 4 the geomagnetic pole positions are consistent with that of the african plate during the cretaceous and a european plate location during both pliocene and miocene time the pole positions are upper cretaceous 212 3 e 69 3 n upper miocene 200 9 e 82 1 n pliocene 339 3 e 85 9 n

pendant bioconstructions cemented by microbial carbonate in submerged marine caves holocene se sicily abstract unusual pendant bioconstructions occur within two submerged caves in the plemmirio marine protected area south of syracuse se sicily these cm to dm sized bioconstructions project downward from the cave roofs the main framework builders are serpulids belonging to the genera protula semivermilia and josephella encrusting bryozoans corals hydrozoans and sponges are subordinately present whereas bivalves and brachiopods are overall rare these faunal associations are characteristic of the studied caves but only in some places they form small bioconstructions that are cemented by microbial carbonates made up by autochthonous peloidal to clotted peloidal and aphanitic micrite the autochthonous micrite stabilizes the pendant bioconstructions herein referred to as biostalactites the microbial carbonate reveals high contents of bacterial lipid biomarkers among the most abundant compounds are mono o alkyl glycerol ethers mages and branched fatty acids 10 me c16 0 iso and anteiso c15 0 and c17 0 interpreted as biomarkers of sulfate reducing bacteria other compounds preserved in the autochthonous carbonates include lipids derived from marine zoo and phytoplankton brassicasterol dinosterol and monounsaturated short chain fatty acids unspecified marine bacteria saturated and monounsaturated short chain fatty acids and land plants long chain fatty acids long chain alcohols stigmasterol sitosterol and campesterol the observed lipid biomarker signatures are remarkably similar to those of post glacial reefal microbialites where microbialite formation in cavities of the coral framework was also mediated by sulfate reducing bacteria in the submerged caves of plemmirio marine protected area serpulid colonies apparently occur preferentially where freshwater is seeping through crevices in the limestone the consequent nutrification is believed to favor serpulid aggregation and the growth of other skeletal i e bryozoans and corals and soft bodied organisms i e sponges and ascidiae the resultant accumulation of biomass and its taphonomy provide niches for sulfate reducing bacteria which induce carbonate precipitation cementing and stabilizing the biostalactites the finding of pendant cemented bioconstructions in the mazzere and granchi caves of the plemmirio marine protected area reveals that sulfate reducing bacteria are involved in microbialite formation in various cryptic environments the formation of such peloidal to clotted peloidal microcrystalline carbonates in cryptic ecosystems is a significant factor for the stabilization of different kinds of bioconstructions spanning from small biostalactites to large reefs

palaeoenvironment and palaeogeography of miocene marls from southeast sicily and the maltese islands abstract tortonian marls and clays are extensively developed in southeast sicily macrofaunas are sparsely distributed in these strata except for a new section at musenna hill in the vittoria scoglitti area this section together with two other coastal sequences of about the same age are described for the first time their abundant faunas are recorded ecological requirements for these faunas are considered and some attempt is made to place them into the known sicilian miocene stratigraphy the musenna hill section shows a particularly close relationship to the upper part of the miocene blue clay formation of the maltese islands both from the viewpoint of sediment and macrofauna the maltese faunas are recorded in detail for the first time and ecological and palaeogeographical information is considered an attempt at an overall regional palaeoenvironmental reconstruction is made for the maltese and southeast sicilian parts of the central mediterranean for tortonian times

the miocene costa giardini diatreme iblean mountains southern italy model for maar diatreme formation on a submerged carbonate platform in this paper we present a model for the growth of a maar diatreme complex in a shallow marine environment the miocene age costa giardini diatreme near sortino in the region of the iblei mountains of southern sicily has an outer tuff ring formed by the accumulation of debris flows and surge deposits during hydromagmatic eruptions vesicular lava clasts accretionary lapilli and bombs in the older ejecta indicate that initial eruptions were of gas rich magma abundant xenoliths in the upper late deposited beds of the ring suggest rapid magma ascent and deepening of the eruptive vent is shown by the change in slope of the country rock the interior of the diatreme contains nonbedded breccia composed of both volcanic and country rock clasts of variable size and amount the occurrence of bedded hyaloclastite breccia in an isolated outcrop in the middle lower part of the diatreme suggests subaqueous effusion at a low rate following the end of explosive activity intrusions of nonvesicular magma forming plugs and dikes occur on the western side of the diatreme and at the margins close to the contact between breccia deposits and country rock they indicate involvement of volatile poor magma possibly during late stages of activity we propose that initial hydromagmatic explosive activity occurred in a shallow marine environment and the ejecta created a rampart that isolated for a short time the inner crater from the surrounding marine environment this allowed explosive activity to draw down the water table in the vicinity of the vent and caused deepening of the explosive center a subsequent decrease in the effusion rate and cessation of explosive eruptions allowed the crater to refill with water at which time the hyaloclastite was deposited emplacement of dikes and plugs occurred nonexplosively while the breccia sediment was mostly still soft and unconsolidated locally forming peperites the sheltered low energy lagoon filled with marine limestones mixed with volcaniclastic material eroded from the surrounding ramparts ultimately lagoonal sediments accumulated in the crater until subsidence or erosion of the tuff ring caused a return to normal shallow marine conditions

pacific sea surface temperature and the winter of 2014 it is shown from historical data and from modeling experiments that a proximate cause of the cold winter in north america in 2013 2014 was the pattern of sea surface temperature sst in the pacific ocean each of the three dominant modes of sst variability in the pacific is connected to the tropics and has a strong expression in extratropical sst and weather patterns beginning in the middle of 2013 the third mode of sst variability was two standard deviations positive and has remained so through january 2015 this pattern is associated with high pressure in the northeast pacific and low pressure and low surface temperatures over central north america a large ensemble of model experiments with observed ssts confirms that sst anomalies contributed to the anomalous winter of 2014

on the role of tropical ocean forcing of the persistent north american west coast ridge of winter 2013 14a abstractthe causes of the high pressure ridge at the north american west coast during winter 2013 14 the driest winter of the recent california drought are examined the ridge was part of an atmosphere ocean state that included anomalies defined relative to a 1979 2014 mean of circulation across the northern hemisphere warm sea surface temperatures ssts in the tropical western and northeastern pacific and the south indian ocean and cool ssts in the central tropical pacific the sst anomalies differ sufficiently between datasets that when used to force atmosphere models the simulated circulation anomalies vary notably in realism recognizing uncertainty in the sst field the authors use idealized tropical sst anomaly experiments to identify an optimal combination of sst anomalies that forces a circulation response that best matches observations the optimal sst pattern resembles that observed but the associated circulation pattern is much weaker than observed suggesting an important but limited

orographic effects on precipitating clouds 1 precipitation over and near mountains is not caused by topography but rather occurs when storms of a type that can occur anywhere deep convection fronts tropical cyclones form near or move over complex terrain deep convective systems occurring near mountains are affected by channeling of airflow near mountains capping of moist boundary layers by flow subsiding from higher terrain and triggering to break the cap when low level flow encounters hills near the bases of major mountain ranges mesoscale convective systems are triggered by nocturnal downslope flows and by diurnally triggered disturbances propagating away from mountain ranges the stratiform regions of mesoscale convective systems are enhanced by upslope flow when they move over mountains in frontal cloud systems the poleward flow of warm sector air ahead of the system may rise easily over terrain and a maximum of precipitating cloud occurs over the first rise of terrain and rainfall is maximum on ridges and minimum in valleys if the low level air ahead of the system is stable blocking or damming occurs shear between a blocked layer and unblocked moist air above favors turbulent overturning which can accelerate precipitation fallout in tropical cyclones the tangential winds encountering a mountain range produce a gravity wave response and greatly enhanced upslope flow depending on the height of the mountain the maximum rain may occur on either the windward or leeward side when the capped boundary layer of the eye of a tropical cyclone passes over a mountain the cap may be broken with intense convection resulting

frontogenesis over a mountain ridge abstract the interaction of developing two dimensional cold and warm frontal systems with a mesoscale mountain ridge is examined the flow of the rotating model atmosphere is assumed to be inviscid adiabatic and boussinesq the geostrophic momentum approximation is made an imposed horizontal deformation field forces the frontogenesis the nonlinear model equations are solved numerically in physical space using terrain following coordinates which incorporate the fully nonlinear lower boundary condition comparison of the model results with and without topography enables assessment of the impact of the mountain on the frontogenesis a scale analysis indicates that the most general problem of frontal interaction with an infinite mountain ridge encompasses a seven dimensional parameter space the scale analysis provides justification for die two dimensional geostrophic momentum approximation and defines an inverse richardson number as a measure of the importance of the ageostrophic advection sensitivity

remote linkages to anomalous winter atmospheric ridging over the northeastern pacific severe drought in california between 2013 and 2016 has been linked to the multi year persistence of anomalously high atmospheric pressure over the northeastern pacific ocean which deflected the pacific storm track northward and suppressed regional precipitation during california s winter rainy season multiple hypotheses have emerged regarding why this high pressure ridge near the west coast of north america was so resilient including unusual sea surface temperature patterns in the pacific ocean reductions in arctic sea ice random atmospheric variability or some combination thereof here we explore relationships between previously documented atmospheric conditions over the north pacific and several potential remote oceanic and cryospheric influences using both observational data and a large ensemble of climate model simulations our results suggest that persistent wintertime atmospheric ridging similar to that implicated in california s 2013 2016 drought can at least partially be linked to unusual pacific sea surface temperatures and that pacific ocean conditions may offer some degree of cool season foresight in this region despite the presence of substantial internal variability

causes of extreme ridges that induce california droughts abstractcalifornia droughts are often caused by high amplitude and persistent ridges near and off the west coast of north america without apparent connections with enso here with a hierarchy of climate models it is demonstrated that extreme ridges in this region are associated with a continuum of zonal wavenumber 5 circumglobal teleconnection patterns that originate from midlatitude atmospheric internal dynamics although tropical diabatic heating anomalies are not essential to the formation and maintenance of these wave patterns certain persistent heating anomalies may double the probability of ridges with amplitudes in the 90th percentile occurring on interannual time scales those heating anomalies can be caused by either natural variability or possibly by climate change and they do not necessarily depend on enso the extreme ridges that occurred during the 2013 14 and 2014 15 winters could be examples of ridges produced by heating anomalies that are not associated with enso this mechanism could p

energetics of the western hemisphere circulation pattern abstractthe western hemisphere wh circulation pattern identified by self organizing maps cluster analysis is a low frequency atmospheric regime that influences the fluctuations of large scale c

the sedimentology and development of terravecchia formation carbonates upper miocene of north central sicily possible eustatic influence on facies development abstract on at least two occasions during the late tortonian siliciclastic deposition ceased and carbonates accumulated at the northern margin of the caltanissetta basin in north central sicily bioclastics dominated in the shallower proximal areas while coral reef facies developed where shallow water sand and cobble substrates existed or where sea floor highs has created local shallows the genetic model proposed is that siliciclastic deposition was repeatedly terminated during the late tortonian by rises in sea level which transgressed fluviatile and deltaic environments carbonate deposition was widespread but later erosion and reworking removed much of the sediments except within abandoned delta distributary channels and minor sea floor depressions reef developments associated with channel mouths and the shelf slope break have been preserved in situ whereas channels in more proximal locations are filled with siliciclastic bioclastic and intraclastic rubble from elsewhere on the delta top the wide lateral extent of the truncated tops of the carbonate beds argues for eustatic rather than tectonic controls of erosion and subsequent reworking these events may be closely related in time to other recorded late tortonian eustatic events in the foreland zones such as the hyblean plateau and the maltese islands further south collectively they give some support to a model involving multiple eustatic fluctuations associated with the onset of the messinian desiccation of the mediterranean

quasi geostrophic frontogenesis over topography abstract the problem of quasi geostrophic frontogenesis due to a horizontal deformation field is re examined exact analytic solutions of all flow fields for all times are found for the case of a vertically semi infinite uniformly stratified boussinesq atmosphere the imposed horizontal deformation field is assumed independent of height but may translate horizontally relative to the initial potential temperature distribution and to the variable bottom topography only straight infinitely long fronts and ridge like topographies are considered the solutions in the absence of orography confirm and extend earlier investigations for surface and occluded fronts it is shown that the presence of monotonically sloping topography below a region of deformation leads to the formation of a surface discontinuity in potential temperature in the absence of an initial horizontal thermal gradient the associated secondary circulation is the sum of a closed thermally direct and indirect component the analysis for a tr

upper tropospheric jet axis detection and application to the boreal winter 2013 14 abstractthis study presents a detection scheme for upper tropospheric jets the scheme identifies locations on the dynamical tropopause where the wind shear perpendicular to the wind direction vanishes and subsequently uses a masking criterion to filter out zero shear locations that do not belong to jets the scheme reliably detects jet axes in era interim data with instantaneous weekly or monthly averaged wind fields the dynamical implications of the detected jet axes and their relation to objectively detected wave breaking and blocking are demonstrated for the synoptic evolution during the boreal winter 2013 14 this winter featured a remarkable episode with a stationary ridge trough couplet over the american continent leading to anomalously cold conditions from central canada to the eastern united states the mean synoptic situation during this episode resembles the climatological winter mean but featured a more spatially focused jet axis distribution in the northeastern pacific the tight distrib

the impact of the appalachian mountains on cyclonic weather systems part i a climatology abstract a climatological study of cold fronts and cyclones crossing the appalachian mountains from the west through northwest has been performed a sample size of 50 fronts and 40 cyclones was derived from the seven winter seasons december through march between 1979 and 1986 the analysis revealed that initially linear cold fronts are slowed and deformed by the mountains with the mean frontal speed decreasing 40 and the fronts developing a pronounced kink just east of the southern appalachians furthermore over the mountains the cross front thermal and pressure gradients are enhanced by about 25 and 63 respectively once past the mountains fronts are weaker and often difficult to locate in particular the cyclonic wind shift is very ill defined and the cross front pressure gradient is reduced to 38 of the premountain value finally small scale 500 km diameter lee lows form on more than half of the fronts though typically benign some of these disturbances may play a role in offshore c

a modeling study of the relative roles of tropical and extratropical sst anomalies in the variability of the global atmosphere ocean system abstract in three parallel experiments an atmospheric general circulation model has been subjected to observed monthly varying sea surface temperature ssi conditions in each of the following domains near global ocean goga run tropical pacific toga run and midlatitude north pacific moga run four independent realizations were obtained for the model response to the sequence of sst anomalies during the 1946 88 period in each of the above regions the principal modes of coupling between the imposed sst forcing and the simulated northern hemisphere wintertime 5 1 5 mb height field in various experiments have been identified using a singular value decomposition svd procedure the leading svd mode for the goga experiment is qualitatively similar to that based on observational data although the amplitudes of the simulated height anomalies are notably lower than the observed value the sst pattern of this mode resembles that associated with el nino events the accompanying 5 1 5 mb height anomaly i

the generation of global rotational flow by steady idealized tropical divergence abstract tropical convective heating is balanced on the large scale by the adiabatic cooling of ascent the horizontal divergence of the wind above this heating may be viewed as driving the upper tropospheric rotational wind field a vorticity equation model is used to diagnose this relationship it is shown that because of the advection of vorticity by the divergent component of the flow the rossby wave source can be very different from the simple fd source often used in particular an equatorial region of divergence situated in easterly winds can lead to a rossby wave source in the subtropical westerlies where it is extremely effective this part of the source can be relatively insensitive to the longitudinal position of the equatorial divergence a divergence field which is asymmetric about the equator can lead to a quite symmetric rossby wave source for a steady frictionless flow the rossby wave source averaged over regions within closed streamfunction or absolute vorticity contours is under cert

late cenozoic subduction complex of sicily abstract besides remnants of hercynian deformations in the peloritani nappe and of pre oligocene alpine structures in the troiani nappe most compressive structures observed in the sicilian accretionary wedge result from the late cenozoic tortonian to present continental subduction of the apulia iblei block and are thus synchronous with distensive structures related to the opening of the tyrrhenian sea syntectonic deposits fill southward migrating foredeeps in a sequential fashion and the dating of these deposits helps to constrain the timing of deformation similarly plio quaternary sediments eroded from the accreted units rest on top of the allochthon in either compressive piggy back depressions or extensional basins the age and configuration of these overlap deposits constrain our reconstructions of the subsurface geometry of the underlying peri tyrrhenian detachment faults or s verging thrust faults post depositional erosion normal faulting and syntectonic filling of basins contribute to maintaining the critical taper of the prism whose geometry is continuously altered owing to frontal accretion underplating and isostatic uplift

internal vs external forcing in shallow marine diatreme formation a case study from the iblean mountains se sicily central mediterranean a model of diatreme evolution in a shallow marine setting is based on a multi disciplinary analysis of diatremes in the iblean mountains sicily the approach includes stratigraphic volcanological structural petrologic and compositional data we invoke a complex interplay of internal rapid ascent and pyroclastic fragmentation of a volatile co2 rich nephelinitic magma at depth and external factors these comprise hydroclastic explosions due to near surface interaction of the rising particle volatile mixture with seawater and water saturated lime mud other external factors contributing to diatreme formation include regional and local tectonics graben formation in pull apart motion combined with lateral pipe enlargement by bedrock spalling and radial block subsidence into the diatreme pipe we suggest that fragmentation of volatile rich magma due to internal eruption forcing was fundamental in the formation of the iblean shallow marine diatremes internal and external factors may act to a variable degree however during diatreme evolution in general

midlatitude atmosphere ocean interaction during el nino part ii the northern hemisphere atmosphere abstract the influence of midlatitude air sea interaction on the atmospheric anomalies associated with el nino is investigated by coupling the community climate model to a mixed layer ocean model in the north pacific prescribed el nino conditions warm sea surface temperatures sst in the tropical pacific cause a southward displacement and strengthening of the aleutian low this results in enhanced reduced advection of cold asian air over the west central northwest pacific and northward advetion of warm air over the eastern pacific allowing air sea feedback in the north pacific slightly modified the el nino induced neu surface wind air temperature and precipitation anomalies the anomalous cyclonic circulation over the north pacific is more concentric and shifted slightly to the east in the coupled simulations air sea feedback also damped the air temperature anomalies over most of the north pacific and reduced the precipitation rate above the cold sst anomaly that develops in the central pacifi

linking the tropical northern hemisphere pattern to the pacific warm blob and atlantic cold blob abstractduring 2013 15 prolonged near surface warming in the northeastern pacific was observed and has been referred to as the pacific warm blob here statistical analyses are conducted to show that the generation of the pacific blob is closely related to the tropical northern hemisphere tnh pattern in the atmosphere when the tnh pattern stays in its positive phase for extended periods of time it generates prolonged blob events primarily through anomalies in surface heat fluxes and secondarily through anomalies in wind induced ocean advection five prolonged 24 months blob events are identified during the past six decades 1948 2015 and the tnh blob relationship can be recognized in all of them although the pacific decadal oscillation and el nino can also induce an arc shaped warming pattern near the pacific blob region they are not responsible for the generation of pacific blob events the essential feature of pacific blob generation is the tnh forced gulf of alaska warming pattern this stu

iblean diatremes 3 volcanic processes on a miocene carbonate platform iblean mountains se sicily a comparison of deep vs shallow marine eruptive processes evolution and magma fragmentation processes of two contrasting well exposed diatreme complexes interbedded with late miocene calcareous marine sediments in distinct sedimentary environments of a carbonate platform iblean plateau sicily are compared with each other the nephelinitic cozzo molino diatreme cmd to the east developed in shallow water 0 80 m water depth the alkali basaltic valle guffari seamount vgs to the west grew on a deeper water carbonate ramp 150 200 m water depth we focus on the dominant boundary conditions inferred to have governed depth of magma fragmentation and subaqueous emplacement mechanisms water depth physical nature of host rocks magma composition and inferred differences in initial volatile concentrations there are gross similarities in the composition of the two moderately evolved magmas the low viscosity magmas in both diatremes were laden with xenoliths originating from mantle to lower crustal sites although similar the eastern shallow water cmd was likely more volatile rich with magma fragmented prior to reaching the surface and the surrounding tephra cone was partly emergent the eruptions of the entirely submarine vgs diatreme complex in the deeper water environment were dominated by interaction of soft sediment and alkali basaltic magma or a pre fragmented volatile particle mixture eruption columns were thus strongly damped and the submarine complex never pierced the water surface

mechanisms of hemispherically symmetric climate variability inspired by paleoclimate evidence that much past climate change has been symmetric about the equator the causes of hemispherically symmetric variability in the recent observational record are examined using the national centers for environmental prediction national center for atmospheric research reanalysis dataset and numerical models it was found that the dominant cause of hemispherically symmetric variability is the el nino southern oscillation during an el nino event the tropics warm at all longitudes and the subtropical jets in both hemi spheres strengthen on their equatorward flanks poleward of the tropical warming there are latitude belts of marked cooling extending from the surface to the tropopause in both hemispheres at all longitudes and in all seasons the midlatitude cooling is caused by changes in the eddy driven mean meridional circulation changes in the transient eddy momentum fluxes during an el nino event force upper tropospheric ascent in midlatitudes through a balance between the eddy fluxes and the coriolis torque the eddy driven ascent causes anomalous adiabatic cooling which is primarily balanced by anomalous diabatic heating using a quasigeostrophic spherical model forced by an imposed surface eddy disturbance of chosen wave number and frequency it is shown that the anomalous eddy momentum fluxes are caused by the impact that the changes in the tropically forced subtropical jets have on the propagation in the latitude height plane of transient eddies changes in zonal winds and associated changes in the meridional gradient of potential vorticity create an anomalous region of low meridional wavenumber in the midlatitudes that refracts waves away both poleward and equatorward tropical forcing of variability in the eddy driven mean meridional circulation is another way in addition to rossby wave teleconnections whereby the tropics can influence extratropical climate unlike teleconnections this mechanism causes climate variability that has strong zonally and hemispherically symmetric components and operates throughout the seasonal cycle

building stone employed in the historical monuments of eastern sicily italy an example the ancient city centre of catania an archaeometric study of the stone materials employed in the late baroque historical monuments of the ancient city centre of catania was carried out lithological maps of a selection of monuments transferred to a digital format revealed that the stone materials are both magmatic and sedimentary rocks the colours of which are matched in a peculiar type of bichromy particular attention focused on sedimentary rocks which consist of various types of limestone quarried near the city of syracuse hyblean plateau south eastern sicily carbonate rocks were characterised in terms of mineralogy petrography and geochemistry by studying rock samples from both monuments and historical extraction sites results showed that although only one name was historically attributed to the above lithotypes i e pietra di siracusa they were quarried from many locations and as they belong to various geological formations they therefore exhibit great variety in order to examine the durability of hyblean limestones employed in works of cultural heritage interest salt crystallisation tests were carried out according to standard procedure norms uni en 12370 1999 determination of resistance to crystallisation of salts 6p results are consistent with the forms of deterioration observed in the monuments and highlight the close relationship between textural characteristics and damage our purpose is to provide a basic tool which may be useful both for conserving monuments of cultural heritage and for their restoration

frontal interaction with mesoscale topography abstract a two dimensional hydrostatic nearly adiabatic primitive equation model is used to study the evolution of a front passing across topography frontogenesis is forced by shearing deformation associated with the nonlinear evolution of an eady wave this study extends previous work by including an upper level potential vorticity pv anomaly and a growing baroclinic wave in a baroclinically unstable basic state results for the eady wave simulations show that the mountain retards and blocks the approaching front at the surface while the upper level pv anomaly associated with the front moves across the domain unaffected warm advection ahead of the lee trough forces convergence and cyclonic vorticity growth near the base of the lee slope this vorticity growth is further encouraged by the approach of the upper level pv anomaly the upper level pv anomaly then couples with this new surface vorticity center and propagates downstream the original surface front remains trapped on the windward slope th

thermal weakening of the carbonate basement under mt etna volcano italy implications for volcano instability abstract the physical integrity of a sub volcanic basement is crucial in controlling the stability of a volcanic edifice for many volcanoes this basement can comprise thick sequences of carbonates that are prone to significant thermally induced alteration these debilitating thermal reactions facilitated by heat from proximal magma storage volumes promote the weakening of the rock mass and likely therefore encourage edifice instability such instability can result in slow gravitational spreading and episodic to continuous slippage of unstable flanks and may also facilitate catastrophic flank collapse understanding the propensity of a particular sub volcanic basement to such instability requires a detailed understanding of the influence of high temperatures on the chemical physical and mechanical properties of the rocks involved the juxtaposition of a thick carbonate substratum and magmatic heat sources makes mt etna volcano an ideal candidate for our study we investigated experimentally the effect of temperature on two carbonate rocks that have been chosen to represent the deep heterogeneous sedimentary substratum under mt etna volcano this study has demonstrated that thermal stressing resulted in a progressive and significant change in the physical properties of the two rocks porosity wet i e water saturated dynamic poisson s ratio and wet vp vs ratio all increased whilst p and s wave velocities bulk sample density dynamic and static young s modulus dry vp vs ratio and dry dynamic poisson s ratio all decreased at temperatures of 800 c the carbonate in these rocks completely dissociated resulting in a total mass loss of about 45 and the release of about 44 wt of co 2 uniaxial deformation experiments showed that high in situ temperatures 500 c significantly reduced the strength of the carbonates and altered their deformation behaviour above 500 c the rocks deformed in a ductile manner and the output of acoustic emissions was greatly reduced we speculate that thermally induced weakening and the ductile behaviour of the carbonate substratum could be a key factor in explaining the large scale deformation observed at mt etna volcano our findings are consistent with several field observations at mt etna volcano and can quantitatively support the interpretation of 1 the irregularly low seismic velocity zones present within the sub volcanic sedimentary basement 2 the anomalously high co 2 degassing observed 3 the anomalously high vp vs ratios and the rapid migration of fluids and 4 the increasing instability of volcanic edifices in the lifespan of a magmatic system we speculate that carbonate sub volcanic basement may emerge as one of the decisive fundamentals in controlling volcanic stability