garnet and tourmaline as provenance indicators of terrigenous material in epicontinental carbonates middle triassic s poland abstract heavy mineral grains contained in epicontinental carbonates are very rarely used for provenance analysis this study deals with detrital heavy minerals separated from marly limestones and marlstones of the gogolin formation gf middle triassic s poland to determine their source rocks and alimentary areas the gf carbonates typically contain 1 wt of heavy minerals within the very fine sand fraction the heavy mineral assemblages consist predominantly of garnets 53 0 92 2 and tourmalines 3 8 30 4 epma analyses reveal four groups of garnets low grs almandines with 30 50 mol prp almandines with 20 35 mol prp and up to 35 mol grs almandines with up to 20 mol sps and rare pyrope grains 60 mol prp the composition of the garnets indicates that hp felsic granulites were their main source rocks but more mafic hp rocks eclogites retrograded eclogites and mafic granulites gneisses mica schists and garnet peridotites also contributed the detrital tourmalines are represented mainly by dravite and less frequently by schorl which were derived mostly from paragneisses and mica schists and in minor part from granitoids and pegmatites the e ne part of the bohemian massif is the most probable location of the source rocks the presumed source rocks presently outcrop in the moldanubian zone the kutna hora unit the svratka unit and the gory sowie massif nowadays the bodies formed by the hp rocks within these units are insufficiently large to act as sources for delivering detrital material in the determined proportions the high content of hp metamorphic grains thus indicates the past existence of extensively exposed and abundant high pressure metamorphic rocks eroded during and or after the middle triassic

multi proxy evidence of holocene climate variability in volhynia upland se poland recorded in spring fed fen deposits from the komarow site radiocarbon dated spring fed fen deposits from the komarow site volhynia upland se poland with its multi proxy data macrofossils molluscs geochemistry pollen stable isotopes of oxygen and c

shallow marine carbonate sedimentation in a tectonically mobile basin the muschelkalk middle triassic of upper silesia southern poland abstract earthquakes and resulting tsunamis are important geological phenomena however their sedimentary paleorecord is difficult to identify because some fabrics can be generated by other processes and the criteria for discrimination of seismic and non seismic triggers are not fully established this paper presents several deformation and sedimentary structures in the middle triassic carbonates of upper silesia and discusses their seismogenic and tsunami origin and controls on the deformation type intensity preservation potential and geographic distribution the deformation type and intensity were controlled by the primary lithology whereas the lateral continuity of deformed horizons depended on the lateral extent of hosted facies the thickness and abundance of these structures increase towards the krakow lubliniec fault zone which bounded the area from the east and is considered as the main epicentrum of earthquakes and tsunami initiation the discussed fabrics have a universal significance and can potentially be found in other shallow marine carbonate successions

timing of recovery from the end permian extinction geochronologic and biostratigraphic constraints from south china four volcanic ash beds bracket the early middle triassic boundary as defined by conodont biostratigraphy in a stratigraphic section in south china high precision u pb dates of single zircons allow us to place the early to middle triassic olenekian anisian boundary at 247 2 ma magnetic reversal stratigraphy allows global correlation the new dates constrain the early triassic interval characterized by delayed biotic recovery and carbon cycle instability to 5 m y this time constraint must be considered in any model for the end permian extinction and subsequent recovery

spatial fingerprint and magnitude of changes in the atlantic meridional overturning circulation during marine isotope stage 3 pronounced millennial scale climate variability during marine isotope stage 3 mis3 is considered to be linked to changes in the state of the atlantic meridional overturning circulation amoc i e a warm interstadial cold stadial state corresponds to a strong weak amoc based on a series of freshwater hosing extraction experiments with the state of the art community climate system model version 3 we construct a global spatial fingerprint of oceanic temperature anomalies in response to amoc changes under mis3 boundary conditions highest sensitivity to amoc changes especially in summer is found in northeastern north atlantic sea surface temperature but a characteristic temperature fingerprint is also found at subsurface levels after testing significance of the linear sea surface temperature sst amoc regressions the model results are combined with paleo sst records to estimate the magnitude of millennial scale dansgaard oeschger amoc variations during mis3 the results suggest a mean difference in amoc strength between interstadial and non heinrich stadial states of 9 2 1 2 sv 1

peridotite derived detrital pyropes versus high pressure felsic granulite derived pyrope almandine garnets from the lower triassic deposits of the ne foreland of the bohemian massif s poland central europe

surface changes in the eastern labrador sea around the onset of the little ice age despite the relative climate stability of the present interglacial it has been punctuated by several centennial time scale climatic oscillations the latest of which are often colloquially referred to as the medieval climatic anomaly mca and the little ice age lia the most favored explanation for the cause of these anomalies is that they were triggered by variability in solar irradiance and or volcanic activity and amplified by ocean atmosphere sea ice feedbacks as such changes in the strength of the atlantic meridional overturning circulation amoc are widely believed to have been involved in the amplification of such climatic oscillations the labrador sea is a key area of deep water formation the waters produced here contribute approximately one third of the volume transport of the deep limb of the amoc and drive changes in the north atlantic surface hydrography and subpolar gyre circulation in this study we present multi proxy reconstructions from a high resolution marine sediment core located south of greenland that suggest an increase in the influence of polar waters reaching the labrador sea close to mca lia transition changes in freshwater forcing may have reduced the formation of labrador sea water and contributed towards the onset of the lia cooling

authigenic potassium feldspar a tracer for the timing of palaeofluid flow in carbonate rocks northern calcareous alps austria

decadal variability of subpolar gyre transport and its reverberation in the north atlantic overturning 1 analyses of sea surface height ssh records based on satellite altimeter data and hydrographic properties have suggested a considerable weakening of the north atlantic subpolar gyre during the 1990s here we report hindcast simulations with high resolution ocean circulation models that demonstrate a close correspondence of the ssh changes with the volume transport of the boundary current system in the labrador sea the 1990s decline of about 15 of the long term mean appears as part of a decadal variability of the gyre transport driven by changes in both heat flux and wind stress associated with the north atlantic oscillation nao the changes in the subpolar gyre as manifested in the deep western boundary current off labrador reverberate in the strength of the meridional overturning circulation moc in the subtropical north atlantic suggesting the potential of a subpolar transport index as an element of a moc monitoring system

permian to early triassic magnetostratigraphy from the central european basin in poland implications on regional and worldwide correlations abstract permian early triassic rocks sampled in 15 outcrops 93 hand samples and 11 unoriented boreholes 630 hand samples from the polish part of the central european basin were studied paleomagnetically in spite of extensive remagnetization affecting 50 of samples from the boreholes a magnetic polarity sequence was compiled the polarity pattern is not only common for many sections from the investigated area but also convergent with the global synthetic magnetostratigraphic scale the lower rotliegend early permian rocks contain a reversed polarity record while the upper rotliegend late permian early triassic sediments are characterized by mixed polarity magnetization within the buntsandstein part of that mixed megazone 14 magnetic zones were found buntsandstein sedimentation started with a normal polarity zone which may be compared with that of early griesbachian defined in several places in the world the polarity record noted in the middle buntsandstein sediments could indicate significant stratigraphic gaps or condensations near the middle buntsandstein and rot boundary the comparison of the upper buntsandstein polarity with the early middle triassic magnetostratigraphic data from other basins suggests that the majority or even all the rot sediments should be included in the anisian

palaeomagnetism and the age of the cracow volcanic rocks s poland summary permian rhyodacites melaphyres and tuffs from the cracow area south poland were sampled for the palaeomagnetic and isotope studies single grain u pb dating of most zircon grains separated from the rhyodacites gave mean age of magma emplacement of 294 2 2 1 ma some zircons however displayed younger ages 268 7 3 4 ma probably related to the metasomatic alterations of these rocks two permian components of magnetizations related to these processes were isolated and together with previously defined late carboniferous permian palaeomagnetic poles from south poland were used for construction of the regional apparent polar wander path apwp the early permian segment of this apwp shows a certain departure from the coeval part of the fennoscandian apwp due to anticlockwise rotations of studied rocks most probably caused by mid permian sinistral tectonic movements along reactivated prominent variscan faults of central europe this sense of tectonic mobility does not support the hypothesis about transformation from pangea b to pangea a along an intra pangea dextral megashear during the permian older than previously assumed ages of the post variscan igneous rocks of central europe reduce overlap of gondwana s and laurussia s parts of the early permian pangea a

magnetobiostratigraphy of the spathian to anisian lower to middle triassic kcira section albania summary magnetobiostratigraphic data are presented from three early middle triassic hanbulog limestone successions from kqira northern albania a total of 206 standard palaeomagnetic samples were obtained for thermal demagnetization and statistical analysis from the 42 10 and 5m thick sections the reversal bearing characteristic component carried by haematite and magnetite defines a composite sequence of six main polarity intervals kqln to kq3r in which are embedded four short polarity intervals one at the base of kqln and three towards the top of kqlr the early acquisition of the characteristic remanence is supported by the lateral correlation of magnetozones between sections the early middle triassic boundary approximated by the first occurrence of the conodont chiosella timorensis falls close to the kqlr kq2n polarity transition this is in good agreement with recently published magnetobiostratigraphic data from the coeval chios greece sections the palaeomagnetic pole calculated from the kqira characteristic directions lies close to the triassic portion of the apparent polar wander path for laurussia in european coordinates however a 40 45 clockwise rotation of the external zone of the albano hellenic belt to the south of the scutari pec line is thought to have occurred since the early middle miocene the kqira pole acquires a west gondwana affinity when restored for the neogene clockwise rotation if the clockwise rotation was entirely related to neogene tectonics the kqira area was evidently associated with west gondwana and located at 12 16 n of the western tethys margin

origin of cone in cone calcite veins during calcitization of dolomites and their subsequent diagenesis a case study from the gogolin formation middle triassic sw poland abstract although bedding parallel cone in cone structure calcite veins are present in the middle triassic gogolin formation in opole silesia their occurrence is limited to the emilowka cellular limestone member marly limestones dedolomites consisting of calcite pseudospar are the host rocks the veins which are up to 3 mm high and 30 cm long are built of densely packed cone columns with individual cones up to 0 7 mm high and 0 6 mm wide at their bases and with vertex angle values ranging from 30 to 50 the cones are microfractured and the adjacent cones are vertically shifted in oblique planes the exceptionally small veins consist of calcite fibres up to 0 15 mm high the veins are built of low magnesium and non ferroan calcite characterized by low 18o values ranging from 6 8 to 7 4 and low 13c values ranging from 2 9 to 4 5 vs pdb these isotopic values are similar to those obtained from the host rocks 18o from 6 8 to 7 4 and 13c from 3 2 to 3 6 vs pdb and they are strongly depleted in comparison with the isotopic values of other carbonate particles from the gogolin formation the veins only formed in one lithostratigraphic member suggesting that their origin is related to processes which acted only locally there are two unique processes that the emilowka cellular limestone member alone in the gogolin formation underwent early diagenetic evaporitic dolomitization of lime mud in the sabkha environment and subsequent calcitization of dolomite dolomitization led to sediment cohesion loss porosity increase and initial horizontal laminae separation as a result of the transformation of calcium carbonate to dolomite within anisotropic deposits similar values of geochemical parameters obtained from the vein calcite and the host rock calcite are evidence that vein filling precipitation was contemporary with dedolomitization geochemical data combined with sedimentological research and burial history show meteoric derived waters saturated with respect to calcite as a source of the vein calcite dedolomitization and vein precipitation may have taken place from the norian early jurassic to the late jurassic when the study area became eroded land and the emilowka cellular limestone member may have acted as a local paleoaquifer conducting the meteoric derived waters solid inclusions in the veins detached from the host rock and the calcitized nodules show that the force of calcite crystallization was the main factor responsible for vein widening vertical shifts of adjacent cones remnants of primary fibrous calcite crystals as well as the burial history justify the application of tarr s theory in interpreting the origin of the secondary cone in cone structure within the fibrous structure veins the timing and the particular conditions required for the cones to develop are uncertain

timing and climate forcing of volcanic eruptions for the past 2 500 years volcanic eruptions contribute to climate variability but quantifying these contributions has been limited by inconsistencies in the timing of atmospheric volcanic aerosol loading determined from ice cores and subsequent cooling from climate proxies such as tree rings here we resolve these inconsistencies and show that large eruptions in the tropics and high latitudes were primary drivers of interannual to decadal temperature variability in the northern hemisphere during the past 2 500 years our results are based on new records of atmospheric aerosol loading developed from high resolution multi parameter measurements from an array of greenland and antarctic ice cores as well as distinctive age markers to constrain chronologies overall cooling was proportional to the magnitude of volcanic forcing and persisted for up to ten years after some of the largest eruptive episodes our revised timescale more firmly implicates volcanic eruptions as catalysts in the major sixth century pandemics famines and socioeconomic disruptions in eurasia and mesoamerica while allowing multi millennium quantification of climate response to volcanic forcing

amplified inception of european little ice age by sea ice ocean atmosphere feedbacks abstractthe inception of the little ice age 1400 1700 ad is believed to have been driven by an interplay of external forcing and climate system internal variability while the hemispheric signal seems to have been dominated by solar irradiance and volcanic eruptions the understanding of mechanisms shaping the climate on a continental scale is less robust in an ensemble of transient model simulations and a new type of sensitivity experiments with artificial sea ice growth the authors identify a sea ice ocean atmosphere feedback mechanism that amplifies the little ice age cooling in the north atlantic european region and produces the temperature pattern suggested by paleoclimatic reconstructions initiated by increasing negative forcing the arctic sea ice substantially expands at the beginning of the little ice age the excess of sea ice is exported to the subpolar north atlantic where it melts thereby weakening convection of the ocean consequently northward ocean heat transport is reduced reinf

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

holocene sea surface temperature and sea ice extent in the okhotsk and bering seas accurate prediction of future climate requires an understanding of the mechanisms of the holocene climate however the driving forces mechanisms and processes of climate change in the holocene associated with different time scales remain unclear we investigated the drivers of holocene sea surface temperature sst and sea ice extent in the north pacific ocean and the okhotsk and bering seas as inferred from sediment core records by using the alkenone unsaturation index as a biomarker of sst and abundances of sea ice related diatoms f cylindrus and f oceanica as an indicator of sea ice extent to explore controlling mechanisms in the high latitude pacific temporal changes in alkenone content suggest that alkenone production was relatively high during the middle holocene in the okhotsk sea and the western north pacific but highest in the late holocene in the eastern bering sea and the eastern north pacific the holocene variations of alkenone ssts at sites near kamchatka in the northwest pacific as well as in the western and eastern regions of the bering sea and in the eastern north pacific track the changes of holocene summer insolation at 50 n but at other sites in the western north pacific in the southern okhotsk sea and the eastern bering sea they do not in addition to insolation other atmosphere and ocean climate drivers such as sea ice distribution and changes in the position and activity of the aleutian low may have systematically influenced the timing and magnitude of warming and cooling during the holocene within the subarctic north pacific periods of high sea ice extent in both the okhotsk and bering seas may correspond to some periods of frequent or strong winter spring dust storms in the mongolian gobi desert particularly one centered at 4 3 thousand years before present kyr bp variation in storm activity in the mongolian gobi desert region may reflect changes in the strength and positions of the aleutian low and siberian high we suggest that periods of eastward displacement or increased intensity of the aleutian low correspond with times of increased extent of sea ice in the western okhotsk sea and eastern bering sea

impact of the atlantic multidecadal oscillation on north pacific climate variability 1 in this paper we found that the atlantic multidecadal oscillation amo can contribute to the pacific decadal oscillation pdo especially the component of the pdo that is linearly independent of el nino and the southern oscillation enso i e the north pacific multidecadal oscillation npmo and the associated pacific north america pna pattern using a hybrid version of the gfdl cm2 1 climate model we show that the amo provides a source of multidecadal variability to the north pacific and needs to be considered along with other forcings for north pacific climate change the lagged north pacific response to the north atlantic forcing is through atmospheric teleconnections and reinforced by oceanic dynamics and positive air sea feedback over the north pacific the results indicate that a north pacific regime shift opposite to the 1976 77 shift might occur now a decade after the switch of the observed amo to a positive phase around 1995 citation zhang r and t l delworth 2007 impact of the atlantic multidecadal oscillation on north pacific climate variability geophys res lett 34 l23708

persistent positive north atlantic oscillation mode dominated the medieval climate anomaly the medieval climate anomaly mca was the most recent pre industrial era warm interval of european climate yet its driving mechanisms remain uncertain we present here a 947 year long multidecadal north atlantic oscillation nao reconstruction and find a persistent positive nao during the mca supplementary reconstructions based on climate model results and proxy data indicate a clear shift to weaker nao conditions into the little ice age lia globally distributed proxy data suggest that this nao shift is one aspect of a global mca lia climate transition that probably was coupled to prevailing la nina like conditions amplified by an intensified atlantic meridional overturning circulation during the mca

on the relationship between atmospheric circulation and the fluctuations in the sea ice extents of the bering and okhotsk seas monthly and 3 day averaged nimbus 5 electrically scanning microwave radiometer sea ice data have been analyzed to document the fluctuations of the bering sea and sea of okhotsk ice covers for the four winters 1972 1973 through 1975 1976 on the short term seasonal and interannual time scales and to define those periods for which there is an out of phase relationship between the fluctuations of the two sea ice covers the sea ice fluctuations are shown to be related to changes in the position and intensity of quasi stationary high and low pressure systems associated with large scale standing wave patterns in the atmosphere through a comparison of the areal changes in ice cover with changes in the amplitude and phase of zonal harmonics 1 2 and 3 of the sea level pressure field on the seasonal time scale the sea level pressure for december the month of most rapid seasonal sea ice growth for both the bering and okhotsk seas is dominated by harmonic 2 which explains almost 60 of the total sea level pressure variance on average over the four winters the phase of harmonic 2 which is associated with the position of the aleutian low shifts from 156 e in 1972 1973 to 190 e in 1975 1976 thus providing a connection between the increasingly heavy bering sea ice cover over these four winters and the general circulation of the atmosphere on the short term episodes of midwinter bering sea ice retreat are generally preceded by or coincident with the breakdown of harmonic 1 and the intensification of harmonics 2 and 3 these episodes are also related to the coincidence of the phases of harmonics 2 and 3 with a mean position of 165 e this result is in excellent agreement with a study of the north pacific oscillation showing that the two modes of the oscillation are associated with the longitudinal position of the aleutian low it is suggested here that these two modes result from changes in the amplitudes and phases of atmospheric long waves 1 2 and 3 evidence is also presented indicating that the interaction of standing and transient components of wave 1 may play an important role in these fluctuations finally these results establish an observational connection relating climate dynamics to changes in ice covers in seasonal sea ice zones

geochemical constraints on the origin of secondary magnetizations in the cambro ordovician royer dolomite arbuckle mountains southern oklahoma abstract geochemical and paleomagnetic results from cambro ordovician royer dolomite in the arbuckle mountains southern oklahoma suggest a connection between dolomite type and magnetizations one dolomite type which is most common in the vicinity of the arbuckle anticline has a dull luminescence low 18 o values coeval to slightly lower 87 sr 86 sr ratios and contains an easterly cambro ordovician magnetization in magnetite to the southeast closer to the ouachita mountain front most of the royer dolomite contains a southeasterly and shallow magnetization in magnetite that is interpreted to be late paleozoic in age in contrast to the other dolomites these dolomites contain abundant authigenic k feldspar and pyrite radiogenic 87 sr 86 sr ratios and have a bright red luminescence all of which are consistent with alteration by basinal fluids at one site a stromatolitic bioherm dolomites similar to those at the arbuckle anticline are surrounded by the altered dolomites the distribution of specimen directions at this site is streaked between a cambro ordovician and late paleozoic direction the results of this study suggest a connection either direct by causing precipitation or indirect by increasing permeabilities for another fluid between a radiogenic fluid and a chemical magnetization in magnetite the relatively unaltered dolomites at the stromatolitic bioherm site escaped the almost pervasive alteration and remagnetization caused by the basinal fluids close to the ouachita mountains a potential source for the fluids

volcanic forcing of climate over the past 1500 years an improved ice core based index for climate models 1 understanding natural causes of climate change is vital to evaluate the relative impacts of human pollution and land surface modification on climate we have investigated one of the most important natural causes of climate change volcanic eruptions by using 54 ice core records from both the arctic and antarctica our recently collected suite of ice core data more than double the number of cores ever used before reduces errors inherent in reconstructions based on a single or small number of cores which enables us to obtain much higher accuracy in both detection of events and quantification of the radiative effects we extracted volcanic deposition signals from each ice core record by applying a high pass loess filter to the time series and examining peaks that exceed twice the 31 year running median absolute deviation we then studied the spatial pattern of volcanic sulfate deposition on greenland and antarctica and combined this knowledge with a new understanding of stratospheric transport of volcanic aerosols to produce a forcing data set as a function of month latitude and altitude for the past 1500 years we estimated the uncertainties associated with the choice of volcanic signal extraction criteria ice core sulfate deposition to stratospheric loading calibration factor and the season for the eruptions without a recorded month we forced an energy balance climate model with this new volcanic forcing data set together with solar and anthropogenic forcing to simulate the large scale temperature response the results agree well with instrumental observations for the past 150 years and with proxy records for the entire period through better characterization of the natural causes of climate change this new data set will lead to improved prediction of anthropogenic impacts on climate the new data set of stratospheric sulfate injections from volcanic eruptions for the past 1500 years as a function of latitude altitude and month is available for download in a format suitable for forcing general circulation models of the climate system

simulated response to recent freshwater flux change over the gulf stream and its extension coupled ocean atmosphere adjustment and atlantic pacific teleconnection abstractrecent observation has shown that the dominant mode of the net freshwater flux variations over the north atlantic ocean is the significant trend of freshwater loss over the gulf stream region and its extension in this paper the coupled ocean atmosphere response to this freshwater flux change is investigated based on a series of the fast ocean atmosphere model coupled model experiments the model demonstrates that the freshwater loss over the gulf stream and its extension region directly forces an anomalous cyclonic gyre and triggers a sst dipole with cooling in the western subtropical and warming in the eastern subpolar north atlantic the freshwater loss also forces a significant response in the atmosphere with a negative nao like response in early winter and a basin scale ridge resembling the eastern atlantic mode eam in late winter the salinification also strengthens the atlantic meridional overturning circulation and thus the poleward heat transport leading to tropical cooling the freshw

middle triassic magnetostratigraphy and biostratigraphy from the dolomites and greece abstract magnetostratigrapic and biostratigraphic data across the anisian ladinian middle triassic boundary were obtained from the frotschbach seceda section from the dolomites region of northern italy and the vlichos section from the greek island of hydra where the aghia triada published section was also resampled the frotschbach seceda section includes two radiometrically dated u pb tuff levels and covers two of the three chief candidates for the position of the base of the ladinian namely at the base of the secedensis zone or the subsequent curionii zone the aghia triada section yields biochronological evidence for the base of the secedensis zone whose significance is however critically discussed in the light of the magnetostratigraphic correlation with frotschbach seceda the vlichos section can be correlated with aghia triada and frotschbach seceda by means of magnetic polarity stratigraphy and sparse fossil occurrences the satisfactory correlation of the magnetozones allows us to construct a composite geomagnetic polarity sequence tied to tethyan ammonoid and conodont biostratigraphy for about a 2 4 myr interval across the anisian ladinian boundary

topographic coupling of the atlantic overturning and gyre circulations abstractthe vorticity dynamics associated with the mean and time varying gyre and overturning circulations of the atlantic ocean are examined in a realistic ocean model hindcast simulation of the late twentieth century abyssal flow interaction with sloping bottom bathymetry gives rise to the bottom pressure torque bpt term of the vertically integrated vorticity equation the dominance of this term in the closure of the barotropic gyre circulation noted in previous studies is corroborated here for both non eddy resolving and eddy resolving versions of the parallel ocean program pop model this study shows that bpt is also a dominant term in the vorticity balance of the atlantic meridional overturning circulation amoc and therefore represents a key dynamical link between the overturning and gyre streamfunctions the interannual variability of the atlantic circulation over the last several decades viewed in terms of time varying integral vorticity balances demonstrates the fundamental role played by

challenges and perspectives for large scale temperature reconstructions of the past two millennia knowledge of the temperature variability during the last one to two millennia is important for providing a perspective to present day climate excursions for assessing the sensitivity of the climate to different forcings and for providing a test bed for climate models since systematic instrumental temperature records only extend back to the nineteenth century such knowledge mainly relies on climate sensitive proxy data here we critically assess some of the many challenges related to large scale multiproxy temperature reconstructions we begin with a review of available large scale temperature reconstructions focusing on the differences in low frequency variability and the response to natural forcings such as major volcanic eruptions and changes in total solar irradiance then we discuss different proxy selection strategies review previously used reconstruction methods and discuss their ability to reconstruct the amplitude of the low frequency variability to shed additional light on the challenges of large scale reconstructions we investigate the spatial and temporal correlation structures in the observed temperature field and discuss the implications of these correlation structures regarding the required number and positions of proxies we demonstrate how the unavoidable uncertainty related to noisy proxies will show up as bias and variance in the reconstruction and that the partition between these forms of errors depends on the reconstruction method pseudo proxy experiments are conducted to further discuss the influence of noise and the requirements regarding the geographical location and number of proxies necessary for reliably reconstructing the low frequency variability we conclude with recommendations for future large scale temperature reconstructions

the apparent polar wander path of the european plate in upper triassic lower jurassic times and the liassic intraplate fracturing of pangaea new palaeomagnetic constraints from nw france and sw germany summary in order to constrain the european plate motions during triassic lower jurassic times new palaeomagnetic data were acquired from various triassic liassic sediments of northeastern france and southwestern germany a carnian palaeopole 49 n 131 e k 193 a95 7 n 4 was obtained for keuper marls with consistent directions of normal and reversed polarities rhaetian sandstones also with both polarities and carnian dolomites with a magnetization of probable secondary origin provide a mean pole 51 n 112 e k 109 a95 6 n 6 more westerly than that given above the lower hettangian sampled in limestones of the xeuilley quarry near nancy shows a n r n polarity sequence with well defined anti parallel directions the mean hettangian pole is 55 n 100 e k 123 a95 11 n 3 induan sandstones from the northern vosges show two distinct overprints one consistent with the ladinian carnian magnetizations already observed in the same region the second consistent with the recalculated mean lower jurassic pole of europe five other sites with different rock types also exhibit late overprints with lower jurassic directions the mean pole calculated from these overprints is 74 n 124 e k 125 a95 6 n 6 the revised apparent polar wander path apwp presented here shows that for the mid permian to the earliest jurassic the palaeopoles of europe stayed around 50 latitude while the longitudes drifted from 185 e to 100 e the previously established upper triassic lower jurassic loop of the apwp is shifted westwards by about 25 the revised apwp involves the following plate motions after the late alleghanian tectonic phase which marked the end of the variscan orogeny central western europe rotated counterclockwise during about 70 myr up to the earliest jurassic the south north drift in latitude by 35 nearly 4000 km remained regular from 320 to 205 ma with a constant rate of 3 4cm yr 1 around 205 ma this motion ceased probably because of a collision somewhere in the north of eurasia then in the lower liassic the plate underwent a rapid counterclockwise rotation with a eulerian pole located in northeastern asia synchronous with fracturing in the atlantic and the neotethys areas it is proposed that the intraplate fracturing of pangaea was initiated by the rapid change of the megacontinent motion at the end of the trias

mechanisms behind the temporary shutdown of deep convection in the labrador sea lessons from the great salinity anomaly years 1968 71 abstractfrom 1969 to 1971 convection in the labrador sea shut down thus interrupting the formation of the intermediate dense water masses the shutdown has been attributed to the surface freshening induced by the great salinity anomaly gsa a freshwater anomaly in the subpolar north atlantic the abrupt resumption of convection in 1972 in contrast is attributed to the extreme atmospheric forcing of that winter here oceanic and atmospheric data collected in the labrador sea at ocean weather station bravo and a one dimensional mixed layer model are used to examine the causes of the shutdown and resumption of convection in detail these results highlight the tight coupling of the ocean and atmosphere in convection regions and the need to resolve both components to correctly represent convective processes in the ocean they are also relevant to present day conditions given the increased ice melt in the arctic ocean and from the greenland ice sheet the analysis herein shows that the shutdown was initiat

solar forcing of north atlantic surface temperature and salinity over the past millennium there were several centennial scale fluctuations in the climate and oceanography of the north atlantic region over the past 1 000 years including a period of relative cooling from about ad 1450 to 1850 known as the little ice age1 these variations may be linked to changes in solar irradiance amplified through feedbacks including the atlantic meridional overturning circulation2 changes in the return limb of the atlantic meridional overturning circulation are reflected in water properties at the base of the mixed layer south of iceland here we reconstruct thermocline temperature and salinity in this region from ad 818 to 1780 using paired 18o and mg ca ratio measurements of foraminifer shells from a subdecadally resolved marine sediment core the reconstructed centennial scale variations in hydrography correlate with variability in total solar irradiance we find a similar correlation in a simulation of climate over the past 1 000 years we infer that the hydrographic changes probably reflect variability in the strength of the subpolar gyre associated with changes in atmospheric circulation specifically in the simulation low solar irradiance promotes the development of frequent and persistent atmospheric blocking events in which a quasi stationary high pressure system in the eastern north atlantic modifies the flow of the westerly winds we conclude that this process could have contributed to the consecutive cold winters documented in europe during the little ice age

radiative forcing and climate impact resulting from so2 injections based on a 200 000 year record of plinian eruptions along the central american volcanic arc we present for the first time a self consistent methodology connecting volcanological field data to global climate model estimates for a regional time series of explosive volcanic events using the petrologic method we estimated so2 emissions from 36 detected plinian volcanic eruptions occurring at the central american volcanic arc cava during the past 200 000 years together with simple parametrized relationships collected from past studies we derive estimates of global maximum volcanic aerosol optical depth aod and radiative forcing rf describing the effect of each eruption on radiation reaching the earth s surface in parallel aod and rf time series for selected cava eruptions are simulated with the global aerosol model maecham5 ham which shows a relationship between stratospheric so2 injection and maximum global mean aod that is linear for smaller volcanic eruptions 5 mt so2 and nonlinear for larger ones 5 mt so2 and is qualitatively and quantitatively consistent with the relationship used in the simple parametrized approximation potential climate impacts of the selected cava eruptions are estimated using an earth system model of intermediate complexity by rf time series derived by 1 directly from the global aerosol model and 2 from the simple parametrized approximation assuming a 12 month exponential decay of global aod we find that while the maximum aod and rf values are consistent between the two methods their temporal evolutions are significantly different as a result simulated global maximum temperature anomalies and the duration of the temperature response depend on which rf time series is used varying between 2 and 3 k and 60 and 90 years for the largest eruption of the cava dataset comparing the recurrence time of eruptions based on the cava dataset with the duration of climate impacts based on the model results we conclude that cumulative impacts due to successive eruptions are unlikely the methodology and results presented here can be used to calculate approximate volcanic forcings and potential climate impacts from sulfur emissions sulfate aerosol or aod data for any eruption that injects sulfur into the tropical stratosphere

paleomagnetic constraints on the permian triassic boundary in terrestrial strata of the karoo supergroup south africa implications for causes of the end permian extinction event the closure of the palaeozoic witnessed the greatest biotic crisis in earth history surprisingly little is known about the effects and timing of the terrestrial counterpart of the well described end permian mass extinction from known marine successions worldwide in the present study reliable paleomagnetic results were obtained from a pt boundary section in the terrestrial karoo basin of south africa permo triassic aged mudstones from a locality in the eastern cape province yielded two magnetic chrons reverse followed by normal with the boundary possibly close to the reversal this extends to results from a previous study thereby jointly identifying a r n r polarity pattern for this boundary interval the ptb interval is constrained below the red mudstones of the beaufort group at the present locality and within reverse magnetised green mudstone implying a diachronic relation between the marine and terrestrial end permian mass extinction events

magnetostratigraphy of the sherwood sandstone group lower and middle triassic south devon uk detailed correlation of the marine and non marine anisian the sherwood sandstone group in south devon consists of the budleigh salterton pebble beds and the otter sandstone formation the otter sandstone formation comprises four lithostratigraphic sub units from the base labelled a d and contains tetrapods corresponding to the perovkan land vertebrate faunachron and is consequently a key european non marine anisian succession a total of 181 palaeomagnetic specimens from 92 horizons were measured to determine the palaeomagnetic signal the magnetic properties and characteristic remanence is predominantly carried by haematite most of which probably formed early in the depositional and diagenetic history the lower part of the sherwood sandstone group budleigh salterton pebble beds and otter sandstone formation unit a lower part of unit b has predominantly normal polarity magnetozones bs1 bs2 and bs3n with three thin reversed polarity magnetozones the lower part of unit b to the lower part of unit c of the otter sandstone formation is predominantly reverse polarity magnetozones bs3r bs4 and bs5 but includes three short normal polarity intervals the upper ca 50 m of unit c shows a mix of normal and reverse polarity bs6 bs7 with normal dominating the ca 15 m thick unit d is entirely of normal polarity bs8n the magnetostratigraphy allows unambiguous comparison with conodont and ammonite calibrated magnetostratigraphies from elsewhere in europe these show that the bs2 and bs3n magnetozones of the otter sandstone formation are lower aegean to middle pelsonian lower to middle anisian the bs3r to bs5r magnetozone interval is middle pelsonian to lower illyrian middle to upper anisian and the bs6 to bs8n magnetozone interval is middle illyrian to lower fassanian the top of unit d is correlated to an interval in the middle of the nevadites zone close to the anisian ladinian boundary consequently the otter sandstone formation correlates with the muschelkalk in the polish basin but is equivalent to only part of the germanic basin muschelkalk the continuous magnetostratigraphy from the sherwood sandstone group provides additional details of the polarity pattern through the pelsonian to illyrian interval which appears to be lacking in discontinuous marine sections a synthesis of adjacent european sedimentary basins in combination with the magnetostratigraphy suggests that the budleigh salterton pebble beds are probably late spathian to lower aegean

holocene history of landscape instability in iceland can we deconvolve the impacts of climate volcanism and human activity abstract biogeochemical proxy records from icelandic lake sediment track large scale shifts in north atlantic holocene climate and highlight the impact that north atlantic ocean and atmospheric circulation has on iceland s climate and environment following early holocene warmth centennial scale climate change is superimposed on millennial scale cooling culminating in the transition to the little ice age 1300 1900 ce although the long term cooling trend is presumably driven by variations in earth s orbit and the concomitant decline in northern hemisphere nh summer insolation the centennial scale variability has been linked to the strength of the atlantic meridional overturning circulation amoc volcanism coupled with sea ice ocean related feedbacks internal modes of atmospheric variability and plausibly variations in solar irradiance one manifestation of these regional climate changes on iceland is the intensification of soil erosion resulting in the degradation of ecosystems and landscape in recent millennia persistent and severe soil erosion has also been linked to human impact on the environment following the settlement 870 ce rapid population growth introduction of livestock and the poorly consolidated nature of tephra dominated soils lake proxy composite records suggest that although event dominated landscape instability and soil erosion from the early to middle holocene were likely triggered by large volcanic eruptions the landscape was capable of recovering however a threshold was reached 5 ka bp resulting in a state change whereby the icelandic landscape could no longer fully recover from cold events and or tephra fall landscape sensitivity to climate further intensified at 1 5 ka bp as identified by regime shift analysis hence widespread and irreversible soil erosion began several centuries before the acknowledged settlement of iceland with a second acceleration 1250 ce a 2 ka fully coupled climate transient simulation using cesm1 1 shows a 0 5 c reduction in summer temperature around iceland in the first millennium ce consistent with increased landscape instability and soil erosion in iceland a second phase of persistent summer cooling in the model occurs after 1150 ce with stronger cooling after 1450 ce reaching a maximum shortly after 1850 ce 1 c lower than at the start of the simulation our results suggest that natural variations in regional climate and volcanism are likely responsible for soil erosion prior to human impact with intensification of these processes following settlement particularly during the cooling associated with the little ice age given that the conclusions drawn in this review diverge from the standard paradigm of human induced soil erosion history in iceland research should continue to focus on this complex question from multiple disciplines in particular a combination of emerging biogeochemical techniques e g lipid biomarkers and ancient dna may be best poised to test and quantify the relative roles of natural environmental variables and human settlement in the history of soil erosion on iceland

indo pacific variability on seasonal to multidecadal time scales part i intrinsic sst modes in models and observations abstractthe variability of indo pacific sst on seasonal to multidecadal time scales is investigated using a recently introduced technique called nonlinear laplacian spectral analysis nlsa through this technique drawbacks associated with ad hoc prefiltering of the input data are avoided enabling recovery of low frequency and intermittent modes not previously accessible via classical approaches here a multiscale hierarchy of spatiotemporal modes is identified for indo pacific sst in millennial control runs of ccsm4 and gfdl cm3 and in hadisst data on interannual time scales a mode with spatiotemporal patterns corresponding to the fundamental component of enso emerges along with enso modulated annual modes consistent with combination mode theory the enso combination modes also feature prominent activity in the indian ocean explaining a significant fraction of the sst variance in regions associated with the indian ocean dipole and suggesting a deterministic relationship between these patterns a p

north pacific climate response to freshwater forcing in the subarctic north atlantic oceanic and atmospheric pathways abstract sudden changes of the atlantic meridional overturning circulation amoc are believed to have caused large abrupt climate changes over many parts of the globe during the last glacial and deglacial period this study investigates the mechanisms by which a large freshwater input to the subarctic north atlantic and an attendant rapid weakening of the amoc influence north pacific climate by analyzing four different ocean atmosphere coupled general circulation models gcms under present day or preindustrial boundary conditions when the coupled gcms are forced with a 1 sv sv 106 m3 s 1 freshwater flux anomaly in the subarctic north atlantic the amoc nearly shuts down and the north atlantic cools significantly the south atlantic warms slightly shifting the atlantic intertropical convergence zone southward in addition to this atlantic ocean atmosphere response all of the models exhibit cooling of the north pacific especially along the oceanic frontal zone consistent with paleoclimate recons

was common era glacier expansion in the arctic atlantic region triggered by unforced atmospheric cooling abstract the timing and causes of common era ce glacier growth in the arctic atlantic region remain elusive there is mounting evidence of advances that predate the little ice age 1250 1850 ce this challenges the view that 13th century volcanic eruptions triggered change by spurring sea ice expansion recent climate model simulations indicate this response does not require external forcing under contemporaneous pre industrial boundary conditions here we try to reconcile these new insights by combining regional proxy evidence of glacier and sea ice change with a climate model experiment collated recently published reconstructions demonstrate that regional climate shifted towards a colder mean state around 650 950 ce a period marked by low radiative forcing unforced model simulations reproduce the time transgressive evolution of this response which emerged east of greenland and progressed towards svalbard the inferred pattern is associated with sea ice feedbacks triggered by stochastic atmospheric cooling we argue that this mechanism may explain the timing and pattern of ce glacier growth in the region

indo pacific variability on seasonal to multidecadal time scales part ii multiscale atmosphere ocean linkages abstractthe coupled atmosphere ocean variability of the indo pacific domain on seasonal to multidecadal time scales is investigated in ccsm4 and in observations through nonlinear laplacian spectral analysis nlsa it is found that enso modes and combination modes of enso with the annual cycle exhibit a seasonally synchronized southward shift of equatorial surface zonal winds and thermocline adjustment consistent with terminating el nino and la nina events the surface winds associated with these modes also generate teleconnections between the pacific and indian oceans leading to sst anomalies characteristic of the indian ocean dipole the family of nlsa enso modes is used to study el nino la nina asymmetries and it is found that a group of secondary enso modes with more rapidly decorrelating temporal patterns contributes significantly to positively skewed sst and zonal wind statistics besides enso fundamental and combination modes representing the tropospheric biennial oscillation tbo are found to

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

northern hemispheric cryosphere response to volcanic eruptions in the paleoclimate modeling intercomparison project 3 last millennium simulations 1 we analyzed last millennium simulations circa 850 1850 common era from the paleoclimate modeling intercomparison project 3 pmip3 project to determine whether current state of the art models produce sudden changes and persistence of cold conditions after large volcanic eruptions as inferred from geological records and previous climate modeling snow cover over baffin island in the eastern canadian arctic shows large scale expansion as seen in proxy records in two of the five models with snow cover information available although it is not sustained beyond a decade sea ice expansion in the north atlantic is seen in some pmip3 models after large eruptions although none of these models produce significant centennial scale effects warm baffin island summer climates stunt snow expansion in some models completely and model topography tends to miss the critical plateau elevations that could sustain snow on the island northern hemisphere sea ice extent is lower in six of the eight models than in reconstructions over the past millennium annual average northern hemisphere mean climates have a range of 3 k across models while arctic summer land only climates span more than 6 k this has critical consequences on ice and snow formation and persistence in regions such as the arctic where temperatures are near the freezing point and small temperature changes affect ice and snow feedback that could induce further climate changes thus it is critical that models accurately represent absolute temperature

platy corals from the middle triassic of upper silesia poland implications for photosymbiosis in the first scleractinians abstract coral patch reefs from middle triassic upper pelsonian lower illyrian strata in the upper silesia region of southern poland germanic domain of the peri tethys are rare examples of the first scleractinian buildups the shallowing upward succession in the tarnow opolski quarry records a transition from sponge to coral patch reefs interbedded with bioclastic limestones coral pillarstones built by thin branching volzeia szulci are succeeded by platy pamiroseris silesiaca constructing two platestone layers each up to 50 cm thick serial sections through platestones revealed flat to undulose growth form of p silesiaca the maximum observable dimension of the coral plates is 24 cm wide typically up to 12 cm while thickness of most plates is 1 1 5 cm coral plates are interlayered with crinoidal wacke to packstone and microbialites which are locally important component of the platestone platy corals grew in a shallow turbid water environment with changing but dominantly moderate hydrodynamics net sedimentation was low as indicated by the epibionts encrusted to the undersides of the coral plates and locally common microbial fabrics growth interruptions of p silesiaca record events of storm induced sediment input and resuspension of carbonate mud based on the euphotic floor model the flattened morphology of p silesiaca is interpreted as an optimal growth form in a turbid low light environment platy scleractinian assemblages from silesia are the oldest occurrences of this ecological coral group mostly representing deeper mesophotic habitats and support the hypothesis that some of the earliest scleractinians had photosymbionts like modern zooxanthellae

do paleoclimate proxies agree a test comparing 19 late holocene climate and sea ice reconstructions from icelandic marine and lake sediments geochemical mineralogical and biological indicators preserved in sediments are widely used to reconstruct past climate change but proxies differ in the degree to which their utility as climate indicators has been validated via laboratory experiments modern spatial calibrations or down core comparisons with instrumental climate data multi proxy studies provide another means of evaluating interpretations of proxies this paper presents a multi proxy assessment comparing 19 sub centennially resolved late holocene proxy records covering the period 300 1900 ad from seven icelandic marine and lacustrine core sites we employ simple statistical comparisons between proxy reconstructions to evaluate their correlations over time and ultimately their utility as proxies for regional climate proxies examined include oxygen isotopic composition of benthic and planktonic foraminifera abundance of the sea ice biomarker ip25 allochthonous quartz in marine sediments a proxy for drift ice around iceland marine carbonate abundance total organic carbon concentration chironomid assemblages lacustrine biogenic silica and carbon nitrogen ratios in lake sediments most of the examined proxy records including temperature and sea ice proxies correlate strongly with each other over multi centennial timescales and thus do appear to record changes in regional climate copyright 2011 john wiley sons ltd

non linear holocene climate evolution in the north atlantic a high resolution multi proxy record of glacier activity and environmental change from hvitarvatn central iceland abstract iceland is well situated to monitor north atlantic holocene climate variability terrestrial sites there offer the potential for well dated high resolution continuous records of environmental change and or glacier activity laminated sediments from the proglacial lake hvitarvatn provide a continuous record of environmental change and the development of the adjacent langjokull ice cap for the past 10 2 ka replicate lake sediment cores collected from multiple locations in the basin are placed in a secure geochronology by splicing a varve chronology for the past 3 ka with a tephra constrained paleomagnetic secular variation derived chronology for older sediments multiple proxies including sedimentation rate bulk density ice rafted debris sediment organic matter biogenic silica and diatom abundance allow annual to multi decadal resolution and reveal a dynamic holocene terrestrial climate following regional deglaciation of the main iceland ice sheet summer temperatures were high enough that mountain ice caps had already melted or were contributing insignificant sediment to the lake pronounced increases in sedimentation rate sediment density and the influx of terrestrial organic matter between 8 7 and 7 9 ka suggest early holocene warmth was interrupted by two distinct pulses of cold summers leading to widespread landscape destabilization and possibly glacier growth the holocene thermal maximum htm 7 9 to 5 5 ka was characterized by high within lake productivity and ice free conditions in the watershed neoglaciation is recorded as a non linear transition toward cooler summers landscape destabilization and the inception and expansion of langjokull beginning ca 5 5 ka with notable increases in ice cap size and landscape instability at 4 2 and 3 0 ka the past two millennia are characterized by the abrupt onset of sustained cold periods at ca 550 and 1250 ad separated by an interval of relative warmth from ca 950 to 1150 ad the greatest holocene extent of langjokull occurred in the nineteenth century and is coincident with peak landscape instability followed by ice recession throughout the twentieth century

coupled modes of north atlantic ocean atmosphere variability and the onset of the little ice age hydroclimate extremes in north america europe and the mediterranean are linked to ocean and atmospheric circulation anomalies in the atlantic but the limited length of the instrumental record prevents complete identification and characterization of these patterns of covariability especially at decadal to centennial timescales here we analyze the coupled patterns of drought variability on either side of the north atlantic ocean basin using independent climate field reconstructions spanning the last millennium in order to detect and attribute epochs of coherent basin wide moisture anomalies to ocean and atmosphere processes a leading mode of broad scale moisture variability is characterized by distinct patterns of north atlantic atmosphere circulation and sea surface temperatures we infer a negative phase of the north atlantic oscillation and colder atlantic sea surface temperatures in the middle of the 15th century coincident with weaker solar irradiance and prior to strong volcanic forcing associated with the early little ice age

centennial scale climate change from decadally paced explosive volcanism a coupled sea ice ocean mechanism northern hemisphere summer cooling through the holocene is largely driven by the steady decrease in summer insolation tied to the precession of the equinoxes however centennial scale climate departures such as the little ice age must be caused by other forcings most likely explosive volcanism and changes in solar irradiance stratospheric volcanic aerosols have the stronger forcing but their short residence time likely precludes a lasting climate impact from a single eruption decadally paced explosive volcanism may produce a greater climate impact because the long response time of ocean surface waters allows for a cumulative decrease in sea surface temperatures that exceeds that of any single eruption here we use a global climate model to evaluate the potential long term climate impacts from four decadally paced large tropical eruptions direct forcing results in a rapid expansion of arctic ocean sea ice that persists throughout the eruption period the expanded sea ice increases the flux of sea ice exported to the northern north atlantic long enough that it reduces the convective warming of surface waters in the subpolar north atlantic in two of our four simulations the cooler surface waters being advected into the arctic ocean reduced the rate of basal sea ice melt in the atlantic sector of the arctic ocean allowing sea ice to remain in an expanded state for 100 model years after volcanic aerosols were removed from the stratosphere in these simulations the coupled sea ice ocean mechanism maintains the strong positive feedbacks of an expanded arctic ocean sea ice cover allowing the initial cooling related to the direct effect of volcanic aerosols to be perpetuated potentially resulting in a centennial scale or longer change of state in arctic climate the fact that the sea ice ocean mechanism was not established in two of our four simulations suggests that a long term sea ice response to volcanic forcing is sensitive to the stability of the seawater column wind and ocean currents in the north atlantic during the eruptions

la icp ms analysis of rare earth elements in marine reptile bones from the middle triassic bonebed upper silesia s poland impact of long lasting diagenesis and factors controlling the uptake abstract the rare earth elements ree contained in fossil bones are widely used for provenance and palaeoenvironmental studies earlier works suggested that the ree uptake is limited to early diagenesis but more recent research provided evidence of long term open system diffusion in fossil bones we analysed thin walled reptile bones all collected from the same middle triassic 245 ma marine bonebed comprising vertebrate remains of likely different ages to check the influence of the long term diagenesis on the concentrations of ree in terms of impact of pore water the upper parts of the bones are contained in a low permeability crinoidal limestone whereas their lower parts have been affected by diagenetic fluids for a long time we measured ree and other trace element contents in 29 bones using la icp ms totally 660 spots in 45 depth profiles neither the absolute concentrations of the ree and the ree intra bone paas normalised patterns nor the inter element ratios and the la ce and eu anomalies appear useful to distinguish between the likely older and younger bones in the bonebed the mree n enrichment combined with the flat intra bone distributions of the ree lead to conclusion that ree fractionation and substitution for ca were the most important processes responsible for the selective uptake the low permeability host rock and diagenetic fluids had a significant impact on the trace element uptake and their intra bone distribution patterns the lower parts of the bones that likely had a long lasting contact with the diagenetic fluids reveal a relative enrichment in the ree and their easier diffusion into the bone centres the ability of fossil bones to incorporate trace elements over a long time span strongly limits the usage of particularly the older samples for provenance and palaeoenvironmental reconstructions additionally the presented new analyses fill the gap between the available databases of trace element concentrations in fossil bones with regard to middle triassic samples

poleward ocean heat transports sea ice processes and arctic sea ice variability in noresm1 m simulations results from the noresm1 m coupled climate model were used to examine relationships between arctic sea ice area and ocean heat transports through the primary arctic gateways comparisons were made with two other models cnrm cm5 and mri cgm3 that are part of the cmip5 archive which have the required outputs for calculating ocean heat transports based on an evaluation noresm1 m was found to be best suited to study the effects of heat transports on sea ice area and conclusions are based on results from this model the arctic ocean was divided into two regions the barents sea and the central arctic ocean the sea ice area variability was further analyzed in terms of frazil and congelation growth top and bottom melting and heat transports in the barents sea opening bso and the fram strait fs in the barents sea increased heat transport in the bso has a strong influence on sea ice area in terms of reduced congelation growth while bottom melting is important for the variability in the central arctic ocean the negative trend in sea ice area is considerably greater in the barents sea than in the central arctic ocean despite the central arctic ocean area being much larger and reflects the major trend in the bso heat transport the model results in this study suggest that the ocean has stronger direct impact on changes in sea ice mass in terms of freezing and melting than the atmosphere both in the mean and with respect to variability

the permian triassic boundary in the central european basin magnetostratigraphic constraints some stratigraphic interpretations concerning correlation of the permian triasssic transition beds from the central european boreal and tethyan basins are inconsistent with the existing magnetostratigraphic data in addition the suggestion that the permian triassic boundary is located in the lower part of the calvorde formation of the central european basin cannot be supported by magnetostratigraphic data results of magnetostratigraphic correlation show that in the polish part of the central european basin the permian triassic boundary is close to the boundary between the uppermost zechstein and the lower buntsandstein it is located within the reversed magnetozone pzr1 identified in the upper part of the rewal formation in the german part of the central european basin the permian triassic boundary can be located within the reversed magnetozone zrz that covers most of the brockelschiefer a higher stratigraphic location of this boundatry i e inside the lowermost buntsandstein requires a reversed polarity record to be found within the basal triassic normal polarity zone

a middle triassic paleomagnetic pole for the eurasian plate from heming france the paleomagnetic study of middle triassic limestones 91 cores 160 samples from a 40 m thick section in heming france yields a paleomagnetic pole for stable europe at lat 53 5 n lon 140 8 e dp 2 3 dm 3 9 this pole fills an important gap of the apparent polar wander path apwp of the eurasian plate the comparison of this pole with available data shows a standstill of the eurasian plate from the late paleozoic to the middle triassic followed by a rapid drift until the lower jurassic the beginning of the rapid drift is contemporaneous with the initiation of main rifting processes in the tethyan oceans

the origins of late twentieth century variations in the large scale north atlantic circulation abstractsurface forcing perturbation experiments are examined to identify the key forcing elements associated with late twentieth century interannual to decadal atlantic circulation variability as simulated in an ocean sea ice hindcast configuration of the community earth system model version 1 cesm1 buoyancy forcing accounts for most of the decadal variability in both the atlantic meridional overturning circulation amoc and the subpolar gyre circulation and the key drivers of these basin scale circulation changes are found to be the turbulent buoyancy fluxes evaporation as well as the latent and sensible heat fluxes these three fluxes account for almost all of the decadal amoc variability in the north atlantic even when applied only over the labrador sea region year to year changes in surface momentum forcing explain most of the interannual amoc variability at all latitudes as well as most of the decadal variability south of the equator the observed strengthening of southern ocean westerly wi

long term river discharge and multidecadal climate variability inferred from varved sediments southwest alaska abstract sedimentological analyses of 289 years ad 1718 2006 of varved sediment from shadow bay southwest alaska were used to investigate hydroclimate variability during and prior to the instrumental period varve thicknesses relate most strongly to total annual discharge r2 0 75 n 43 p

high resolution estimate for the depositional duration of the triassic latemar platform a new magnetostratigraphy and magnetic susceptibility cyclostratigraphy from basinal sediments at rio sacuz italy 1 a new magnetostratigraphy and magnetic susceptibility cyclostratigraphy from middle triassic basinal sediments at rio sacuz northern italy suggests a depositional duration of 1 myr for most of the 670 m carbonate latemar platform giving a high resolution estimate for the duration for the latemar s deposition the new magnetostratigraphy from rio sacuz clarifies the ambiguities in a previous magnetostratigraphic study of the latemar caused by lightning strike remagnetizations our rio sacuz study was unaffected by lightning using thermal demagnetization we show a normal reversed normal reversed sequence at the latemar correlated locality of rio sacuz with a polarity interval duration of 0 25 0 5 myr for the middle triassic this gives a depositional duration of 1 2 myr rock magnetic experiments show that the magnetic carrier is magnetite suggesting a primary depositional age remanence measurement of magnetic susceptibility at 1 m intervals from rio sacuz reveals eight short eccentricity cycles 95 125 kyr bundled into slightly more than two 405 kyr long eccentricity cycles indicating a more precise duration for the rio sacuz section of 0 8 to 1 myr the shorter depositional duration required by this study forces a sub milankovitch time scale of 1 2 kyr for the latemar platform s meter scale rhythmic bedding and provides strong evidence for nonorbitally driven climate change in the middle triassic

modern solar maximum forced late twentieth century greenland cooling the abrupt northern hemispheric warming at the end of the twentieth century has been attributed to an enhanced greenhouse effect yet greenland and surrounding subpolar north atlantic remained anomalously cold in 1970s to early 1990s here we reconstructed robust greenland temperature records north greenland ice core project and greenland ice sheet project 2 over the past 2100 years using argon and nitrogen isotopes in air trapped within ice cores and show that this cold anomaly was part of a recursive pattern of antiphase greenland temperature responses to solar variability with a possible multidecadal lag we hypothesize that high solar activity during the modern solar maximum approximately 1950s 1980s resulted in a cooling over greenland and surrounding subpolar north atlantic through the slowdown of atlantic meridional overturning circulation with atmospheric feedback processes

the middle triassic magnetostratigraphy from the peri tethys basin in poland abstract the paper presents the first complete magnetic polarity scale obtained for the middle triassic of the northern peri tethys area the roetian and muschelkalk deposits of southern poland upper silesia the holy cross mountains were studied paleomagnetically the obtained paleopole a 52 n 143 e fits well to the middle triassic ca 240 ma segment of the stable european apwp a set of various quality characteristic directions isolated in 106 samples was used for construction of the composite polarity scale this peritethyan scale has been tied with conodont zonation and referred to the scale erected earlier in the tethyan realm comparison of both scales indicates that the whole roetian succession in the southern polish basin should be correlated with the latest olenekian the normal marine sedimentation ceased in the polish basin as early as in the late fassanian time the obtained magnetostratigraphic scale combined with the sequence stratigraphic framework enables a reliable chronological correlation of the late olenekian ladinian succession over the entire peri tethys basin

the biostratigraphic importance of conchostracans in the continental triassic of the northern hemisphere conchostracans or clam shrimp order conchostraca sars are arthropods with a carapace consisting of two chitinous lateral valves triassic conchostracans range in size from 2 to 12 5 mm long and are common in deposits that formed in fresh water lakes isolated ponds and brackish areas their dessication and freeze resistant eggs can be dispersed by wind over long distances therefore many conchostracan species are distributed throughout the entire north ern hemisphere in the late permian to middle triassic interval several of these forms are also found in gondwana many wide ranging conchostracan species have short stratigraphic ranges making them excellent guide forms for subdivision of triassic time and for long range correlations the stratigraphic resolution that can be achieved with conchostracan zones is often as high as for ammonoid and conodont zones found in pelagic marine deposits this makes con chostracans the most useful group available for biostratigraphic subdivision and correlation in continental lake deposits upper triassic gondwanan conchostracan faunas are different from conchostracan faunas of the northern hemisphere in the norian some slight provincialism can be observed even within the northern hemisphere for example the sevatian redondestheria seems to be restricted to north america and acadiestheriella n gen so far has been found only in the sevatian deposits from the fundy basin of southeastern canada here we establish a con chostracan zonation for the changhsingian late permian to hettangian early jurassic of the northernhemispherethat forthemostpart isverywellcorrelatedwiththemarinescale thiszona tion is especially robust for the changhsingian to early anisian late ladinian to cordevolian and rhaetian to hettangian intervals for most of the middle and upper triassic this zonation is still preliminary five new genera six new species and a new subspecies of conchostracans are described that are stratigraphically important half of the eight stage boundaries of the triassic have been defined by a bio event within a marine global stratotype and point gssp locality and these definitions have been accepted by both the international subcommission on triassic stratigra phy and the international commission on stratigra phy the remaining four stage boundaries are nearing final definition in the lower triassic both the base of the induan priority brahmanian stage base of triassic and the base of the next younger olenekian stage have been firmly defined in the middle triassic there is wide agree ment that the defining species for the base of the anisian stage should be chiosella timorensis in the gssp candidate site at desli caira romania but there has not yet been a formal vote on this the base of the overlying ladinian stage however has been firmly defined in the upper triassic the base of the carnian has been firmly likewise defined but there is not yet a final defi nition for the boundaries of the overlying norian and rhaetian stages a consensus has not been reached on a defining species for the base of the norian or its gssp locality but all of the different proposals under consideration do at least fall within a rather narrow stratigraphic interval for the base of the rhaetian misikella posthernsteini kozur mock has been chosen as the defining species by the international working group on the rhaetian stage and the gssp candidate locality at steinbergkogel austria has been studied in detail by a group under the leadership of l krystyn vienna and presented to the participants of the international conference on upper triassic sub divisions zonations and events in bad goisern in the autumn of 2008 the base of the overlying hettangian stage base of the jurassic has been defined so far only by a working group as the fad first appearance datum of psiloceras spelae guex taylor rakus bucher the final definition of the triassic stages within marine gssp sections will be completed in the near future but more than 50 of known triassic rocks are of continental origin therefore the main task of triassic stratigraphers in thefuture will besubdivid ing and correlating terrestrial strata both between

distribution of sedimentary organic matter in anisian carbonate series of s poland evidence of third order sea level fluctuations the stratigraphic distribution of sedimentary organic matter in anisian carbonate series of southern poland is studied with respect to relative sea level fluctuations palynofacies patterns clearly reflect transgressive regressive trends that are interpreted in terms of third order cyclicity major flooding phases are detected by maximum abundance of marine plankton in the upper bithynian and pelsonian transgressive and highstand deposits are recognized by changes in the terrestrial input of organic particles and the relative percentages and diversity of the plankton group the palynological data support the sequence stratigraphic interpretation based on sedimentological features and geochemical signatures the corresponding eustatic signals of sedimentary and organic facies are discussed the study highlights the potential of palynofacies analysis for sequence stratigraphical interpretation

early namaqua low pressure metamorphism deformation and porphyroblast growth in the zoovoorby staurolite schist south africa this paper describes the deformation and metamorphism recorded in the zoovoorby staurolite schist a sliver of pelitic supracrustal material in the 1 3 1 0 ga eastern namaqua province south africa the supracrustal biesjepoort group of which the schist is a part has undergone at least four phases of deformation d1 d4 d1 and d2 are preserved in the pelitic schists staurolite and garnet grew during d1 with staurolite growth persisting to the very earliest d2 crenulation andalusite found in more mg rich schists grew during d2 overprinting both s1 schistosity and s0 banding s2 has been rotated both with respect to s1 preserved as parallel orientated inclusion trails in garnet and staurolite and with respect to its original orientation preserved as open d2 crenulations in staurolite staurolite is dissolved against s2 in zones of progressive shear the pseudomorphing of staurolite and andalusite by cordierite and the preservation of relic grains of both minerals in a wide range of garnet cordierite pelites throughout the eastern namaqua province infers that what is preserved fortuitously in the zoovoorby locality is representative of the early metamorphic history of a much larger terrane the high thermal gradients needed to attain estimated conditions of 540 550 c and 1 6 2 4 kbar require substantial heat input large amounts of foliated syn d2 granite amongst the supracrustal succession are inferred to be the result of delamination of a thickened crust at a destructive plate margin generating an elevated thermal gradient during d1 d2 times

the great salinity anomaly in the northern north atlantic 1968 1982 the widespread freshening of the upper 500 800m layer of the northern north atlantic which this paper describes represents one of the most persistent and extreme variations in global ocean climate yet observed in this century though a range of explanations have been advanced to explain this event including in situ changes in the surface moisture flux this paper describes the great salinity anomaly as largely though not entirely an advective event traceable around the atlantic subpolar gyre for over 14 years from its origins north of iceland in the mid to late 1960s until its return to the greenland sea in 1981 1982 the overall propagation speed around this subpolar gyre is estimated at about 3cm s 1 of the total salt deficit associated with the anomaly as it passed south along the labrador coast in 1971 1973 about 72 109 tonnes a deficit equivalent to about two thirds of this figure 47 109 tonnes ultimately passed through the faroe shetland channel to the barents sea arctic ocean and greenland sea during the mid 1970s possible effects on deep water formation and on the representativeness of historical section data are discussed

impact of volcanic eruptions on decadal to centennial fluctuations of arctic sea ice extent during the last millennium and on initiation of the little ice age abstractthis study evaluates different hypotheses of the origin of the little ice age focusing on the long term response of arctic sea ice and oceanic circulation to solar and volcanic perturbations the authors analyze the last millennium ensemble of climate model simulations carried out with the community earth system model at the national center for atmospheric research the authors examine the duration and strength of volcanic perturbations and the effects of initial and boundary conditions such as the phase of the atlantic multidecadal oscillation they evaluate the impacts of these factors on decadal to multicentennial perturbations of the cryospheric oceanic and atmospheric components of the climate system the authors show that at least in the last millennium ensemble volcanic eruptions are followed by a decadal scale positive response of the atlantic multidecadal overturning circulation followed by a centennial scale enhancement of the northern hemispheric sea ice extent it is hypothesiz

a 9000 year record of cyclic vegetation changes identified in a montane peatland deposit located in the eastern carpathians central eastern europe autogenic succession or regional climatic influences abstract we present a high resolution continuous plant macrofossil remains record complemented by a pollen sequence from t ul muced bog in the eastern carpathian mountains romania the record spans the last 9000 years and we test whether peatland development in the eastern carpathians is linked to climate change or to autogenic succession we find that sphagnum magellanicum was the dominant peat forming species for ca 8000 years but we also identify ten phases of increased representation of eriophorum vaginatum at approximately 8100 7550 6850 6650 5900 4650 3150 1950 1450 and 750 cal yr bp visual inspection and wavelet analysis show that the episodic increases in the relative abundances of eriophorum vaginatum were simultaneous with decreased abundances of sphagnum magellanicum and sphagnum angustifolium comparison with published palaeoclimatic records in this region suggests that these cyclical successions of s magellanicum and e vaginatum appear to be primarily a result of climate changes with e vaginatum developing mainly during dry phases and s magellanicum during wetter periods we therefore suggest that the development of this peatland was largely influenced by changing climatic conditions although the role of autogenic plant succession cannot be excluded our results show the value of ombrotrophic peat deposits as archives of past climate change

variability of trace element uptake in marine reptile bones from three triassic sites s poland influence of diagenetic processes on the host rock and significance of the applied methodology abstract diagenetic alternation of apatite building vertebrate bioclasts is a complex process it is influenced by numerous factors but the impact of diagenetic processes affecting the host rock is commonly underestimated the present study aims at identifying the causes of different concentration levels and distribution patterns of ree and at examining the significance of the material chosen for normalisation we measured ree and other trace element concentrations in three bone assemblages of triassic marine reptiles using la icp ms and in the host rocks using icp ms two groups of hard parts reveal clearly different trace element contents and distribution patterns the remains from gogolin show a distinct mreen enrichment which must have been caused by replacement involving numerous substitutions that was possible due to a relatively high porosity of the host rocks and the presence of pore water the mreen enrichment and low concentrations of mg and sr combined with a relatively high content of u in these bones indicate solutions derived from meteoric water as the source of the incorporated ions the reductive dissolution of fe oxyhydroxides that are abundant in the host rock matrix and that likely were an important source of ree may have influenced and controlled the ree uptake the significant hreen enrichment over lreen as revealed in the rust coloured bones from raciborowice gorne is likely connected with local acidification of the pore water resulting from aqueous oxidation of pyrite infilling the pore spaces in the bones the material selected for normalisation of the chemical composition of apatite can have a significant impact on values of the normalised data used further for interpretations particularly when vertebrate bioclasts from carbonate host rocks are involved the carbonate rocks have element ratios that differ from those characterising the commonly used paas and nasc normalisation materials in particular ce anomaly values can distinctly vary depending on the applied normalisation procedure vertebrate hard parts that definitely spent more time in a host rock than in an animal body must be rigidly handled as a constituent of a specific rock never as a separate item

reconstructing climate change and ombrotrophic bog development during the last 4000 years in northern poland using biotic proxies stable isotopes and trait based approach article i nfo in this study we present a record spanning the last 4000 years from a baltic bog kusowskie bagno in northern poland using numerous biotic and abiotic proxies such as testate amoebae depth to water table reconstruc tions stable carbon isotopes 13 c plant macrofossils proxies for local vegetation and mire surface wetness pollen and spores proxies for regional vegetation and human impact we reconstructed and identified the re gional hydro climatic signal of kusowskie bagno bog and compared it to other bog records around the baltic sea our aims were to 1 combine the species traits of bryophytes and testate amoebae and more common proxies isotopes plant micro and macro remains to infer past peatland development 2 compare the hydro climatic signal of kusowskie bagno bog to existing records around the baltic sea we found that kusowskie bagno bog was very wet during the last 4000 years and even drainage and peat exploitation had not disturbed its hydrology in northern part in the last 200 years carbon isotopes and plant macrofossils were significantly re latedtospecifictraitsoftestateamoebae whichinturnreflectedthewatertablechangesoverthelast4000years kusowskie bagno recorded at least the following wet shifts ad 250 550 850 1250 and 1700 while wet condi tions occurred during the migration period at ca ad 550 furthermore the testate amoeba based quantitative wetness reconstruction in kusowskie bagno bog resembles the pattern observed in other sites around the baltic i e estonia finland ireland northernbritainandthe7500 yearrecordfromthe st zkibog northern poland our results provided statistically validated evidence that interactions between plant and microbe need to be more considered further to reconstruct past hydrological this is the first study of past hydro climatic changes in peatlands based upon a trait based approach

influence of the atlantic subpolar gyre on the thermohaline circulation during the past decade record high salinities have been observed in the atlantic inflow to the nordic seas and the arctic ocean which feeds the north atlantic thermohaline circulation thc this may counteract the observed long term increase in freshwater supply to the area and tend to stabilize the north atlantic thc here we show that the salinity of the atlantic inflow is tightly linked to the dynamics of the north atlantic subpolar gyre circulation therefore when assessing the future of the north atlantic thc it is essential that the dynamics of the subpolar gyre and its influence on the salinity are taken into account

the drift history of iran from the ordovician to the triassic new late ordovician and triassic palaeomagnetic data from iran are presented these data in conjunction with data from the literature provide insights on the drift history of iran as part of cimmeria during the ordovician triassic a robust agreement of palaeomagnetic poles of iran and west gondwana is observed for the late ordovician earliest carboniferous indicat ing that iran was part of gondwana during that time data for the late permian early early tri assic indicate that iran resided on subequatorial palaeolatitudes clearly disengaged from the parental gondwanan margin in the southern hemisphere since the late early triassic iran has been located in the northern hemisphere close to the eurasian margin this northward drift brought iran to cover much of the palaeotethys in approximately 35 ma at an average plate speed ofc 7 8 cm year 21 and was in part coeval to the transformation of pangaea from an irvin gian b to a wegenerian a type configuration

the little ice age signature in a 700 year high resolution chironomid record of summer temperatures in the central eastern alps despite the fact that the little ice age lia is well documented for the european alps substantial uncertainties concerning the regional spatio temporal patterns of temperature changes associated with the lia still exist especially for their eastern sector here we present a high resolution 4 10 years 700 year long mean july air temperature reconstruction based on subfossil chironomid assemblages from a remote lake in the austrian eastern alps to gain further insights into the lia climatic deterioration in the region the record provides evidence for a prolonged period of predominantly cooler conditions during ad 1530 1920 broadly equivalent to the climatically defined lia in europe the main lia phase appears to have consisted of two cold time intervals divided by slightly warmer episodes in the second half of the 1600s the most severe cooling occurred during the eighteenth century the lia temperature minimum about 1 5 c below the long term mean recorded in the mid 1780 s coincides with the strongest volcanic signal found in the greenland ice cores over the past 700 years and may be at least in part a manifestation of cooling that followed the long lasting ad 1783 1784 laki eruption a continuous warming trend is evident since ca ad 1890 1 1 c in 120 years the chironomid inferred temperatures show a clear correlation with the instrumental data and reveal a close agreement with paleotemperature evidence from regional high elevation tree ring chronologies a considerable amount of the variability in the temperature record may be linked to changes in the north atlantic oscillation

reconstruction of the extratropical nh mean temperature over the last millennium with a method that preserves low frequency variability abstracta new multiproxy reconstruction of the northern hemisphere extratropical mean temperature over the last millennium is presented the reconstruction is performed with a novel method designed to avoid the underestimation of low frequency variability that has been a general problem for regression based reconstruction methods the disadvantage of this method is an exaggerated high frequency variability the reconstruction is based on a set of 40 proxies of annual to decadal resolution that have been shown to relate to the local temperature the new reconstruction shows a very cold little ice age centered around the 17th century with a cold extremum for 50 yr smoothing of about 1 1 k below the temperature of the calibration period ad 1880 1960 this cooling is about twice as large as corresponding numbers reported by most other reconstructions in the beginning of the millennium the new reconstruction shows small anomalies in agreement with previous studies however the new temperature reconstructi

high frequency depositional cycles in the muschelkalk middle triassic of southern poland origin and implications for germanic basin astrochronological scales abstract high frequency depositional cycles are often used for long distance correlations within sedimentary basins and constructing high resolution chronostratigraphic scales calibrated to the orbital clock such an approach has been used for the tropical epicontinental muschelkalk sea covering most of europe in the middle triassic this paper aims at establishing the spatial extent and internal architecture of shallow marine muschelkalk cycles within a small 120 by 50 km area of the germanic basin to identify their local vs regional distribution and cycle forming mechanisms three groups of cycles are distinguished 1 peritidal cycles representing a tidal flat lagoon system which experienced longer periods of emersion 2 shallow subtidal cycles formed around the fair weather wave base and 3 deep subtidal cycles developed around the storm wave base the three cycle types differ markedly in the composition facies homogeneity sedimentary trends hierarchical organization continuity and degree of lateral changeability and complexity which collectively translates into the ease of cycle recognition despite the differences the defined cycles do not extend laterally beyond the studied area and have laterally variable facies heterogeneities sedimentary trends and thicknesses this variability resulted from more or less mosaic infilling of accommodation space reflecting local bathymetry physicochemical conditions and carbonate production and accumulation rates on the platform accommodation space evolved by the interplay of eustatic sea level fluctuations regional subsidence and synsedimentary tectonic block movements but the contribution of these factors changed over time and was to varying degrees masked for each of the three cycle types by intrinsic sedimentary processes the study shows that middle triassic cycles of the germanic basin have a local to sub regional distribution and thereby are inappropriate for basin wide correlations and chronostratigraphic inferences it also strengthens the opinion of several workers that correlation of idealized cycles is unrealistic without checking the horizontal continuity of facies and key surfaces directly in the field

genesis of the lower triassic bonebeds from gogolin s poland the impact of microbial mats on trapping of vertebrate remains abstract three bone bearing horizons consisting of seven bone bearing beds with fish and reptile remains were recently discovered in the uppermost rot buntsandstein lower triassic peritidal and shallow marine carbonates in the vicinity of gogolin s poland the aim of this study is to recognize the genesis and depositional environments of the bonebeds detailed fieldwork microfacies analysis and sem eds analysis reveal that the vertebrate remains occur to a great extent alongside evidence for former microbial activity the reptile remains represent at least dactylosaurus and nothosaurus sauropterygia genera while the fish remains belong to the chondrichthyes and actinopterygii the vertebrate remains were deposited in a transitional zone between the costal sabkha and the epicontinental sea the first bone bearing horizon originated in the most landward setting in the uppermost intertidal zone likely at the margins of a pond or coastal lagoon the second bone bearing horizon was formed in the upper intertidal zone the vertebrate remains of the third bone bearing horizon were accumulated in two different settings in the lower intertidal zone in a small palaeopond and in the subtidal zone in a protected back shoal lagoon three bone accumulations occur within planar stromatolites while the other bone bearing beds reveal more indirect evidence for former microbial activity in our opinion the presence of the sticky microbial mats in the intertidal settings was the crucial factor that allowed the establishment of and controlled these accumulations of vertebrate remains the soft gluey substrates trapped vertebrate remains that were transported across them once trapped the vertebrate bioclasts were efficiently immobilized and thus protected against damage due to sedimentological agents the lack of any orderly arrangement of the vertebrate bioclasts suggests that they may have been delivered to the individual mat surfaces by diverse media from various directions and also at different times

exploring mechanisms of variability and predictability of atlantic meridional overturning circulation in two coupled climate models abstractmultidecadal variability in the atlantic meridional overturning circulation amoc of the ocean is diagnosed in the ncar community climate system model version 3 ccsm3 and the gfdl coupled model cm2 1 common diagnostic approaches are applied to draw out similarities and differences between the two models an index of amoc variability is defined and the manner in which key variables covary with it is determined in both models the following is found i amoc variability is associated with upper ocean top 1 km density anomalies dominated by temperature on the western margin of the basin in the region of the mann eddy with a period of about 20 years these anomalies modulate the trajectory and strength of the north atlantic current the importance of the western margin is a direct consequence of the thermal wind relation and is independent of the mechanisms that create those density anomalies ii density anomalies in this key region are part of a larger scale pattern that propagates ar

coprolites of marine vertebrate predators from the lower triassic of southern poland abstract numerous coprolites are described for the first time herein from the lower triassic olenekian shallow marine sedimentary rocks in southern poland x ray diffraction and geochemical analyses show that they are preserved as calcium phosphate with small admixtures of quartz and calcite additionally sem and thin section studies revealed that they contain highly fragmented faunal remains crinoids molluscs and vertebrates the size shape geochemistry biostratigraphic distribution and co occurrence with vertebrate skeletal remains imply that the coprolites at hand were likely produced by nothosaurids the durophagous sauropterygian reptiles and actinopterygian ray finned fish the large number of recorded coprolites implies that durophagous predation has been intense during the early triassic and suggests that the so called mesozoic marine revolution probably started soon after the end permian extinction furthermore discovery of sinusoidal trails attributable to nematodes in some coprolites implies that the intestinal parasitic associations with these predators had already evolved by at least the early triassic

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

abrupt onset of the little ice age triggered by volcanism and sustained by sea ice ocean feedbacks 1 northern hemisphere summer temperatures over the past 8000 years have been paced by the slow decrease in summer insolation resulting from the precession of the equinoxes however the causes of superposed century scale cold summer anomalies of which the little ice age lia is the most extreme remain debated largely because the natural forcings are either weak or in the case of volcanism short lived here we present precisely dated records of ice cap growth from arctic canada and iceland showing that lia summer cold and ice growth began abruptly between 1275 and 1300 ad followed by a substantial intensification 1430 1455 ad intervals of sudden ice growth coincide with two of the most volcanically perturbed half centuries of the past millennium a transient climate model simulation shows that explosive volcanism produces abrupt summer cooling at these times and that cold summers can be maintained by sea ice ocean feedbacks long after volcanic aerosols are removed our results suggest that the onset of the lia can be linked to an unusual 50 year long episode with four large sulfur rich explosive eruptions each with global sulfate loading 60 tg the persistence of cold summers is best explained by consequent sea ice ocean feedbacks during a hemispheric summer insolation minimum large changes in solar irradiance are not required

potential role of atlantic warm pool induced freshwater forcing in the atlantic meridional overturning circulation ocean sea ice model simulations recent studies have indicated that the multidecadal variations of the atlantic warm pool awp can induce a significant freshwater change in the tropical north atlantic ocean in this paper the potential effect of the awp induced freshwater flux on the atlantic meridional overturning circulation amoc is studied by performing a series of ocean sea ice model experiments our model experiments demonstrate that ocean response to the anomalous awp induced freshwater flux is primarily dominated by the basin scale gyre circulation adjustments with a time scale of about two decades the positive negative freshwater anomaly leads to an anticyclonic cyclonic circulation overlapping the subtropical gyre this strengthens weakens the gulf stream and the recirculation in the interior ocean thus increases warm cold water advection to the north and decreases cold warm water advection to the south producing an upper ocean temperature dipole in the midlatitude as the freshwater salty water is advected to the north atlantic deep convection region the amoc and its associated northward heat transport gradually decreases increases which in turn lead to an inter hemispheric sst seesaw in the equilibrium state a comma shaped sst anomaly pattern develops in the extratropical region with the largest amplitude over the subpolar region and an extension along the east side of the basin and into the subtropical north atlantic based on our model experiments we argue that the multidecadal awp induced freshwater flux can affect the amoc which plays a negative feedback role that acts to recover the amoc after it is weakened or strengthened the sensitivity of amoc response to the awp induced freshwater forcing amplitude is also examined and discussed

analysis of marrow cavity fillings as a tool to recognise diverse taphonomic histories of fossil reptile bones implications for the genesis of the lower muschelkalk marine bone bearing bed middle triassic żyglin s poland abstract the bone bearing bed from yglin s poland which likely represents the oldest lower muschelkalk accumulation of reptile remains in the se part of the germanic basin has been investigated in order to determine its genesis the basic methods were supported by petrographic analysis of the marrow cavity and large inter trabecular pore space fillings of fossil bones which was used to check its usefulness to identify the environments where the bones were initially deposited and to decipher taphonomic histories of the remains the bone bearing bed is a composite deposit which consists of three distinct layers from bottom to top micritic limestone mudstone bioturbated autochthonous mud crinoidal limestone grainstone to packstone calcirudite and shell rich limestone packstone to wackstone calcirudite the crinoidal limestone layer the main bone bearing bed is recognised as the proximal tempestite deposited in the mid ramp zone the petrographic analysis of the fillings reveals the prevalence of minute ostracod carapaces accompanied by other grains embedded together with micrite to microspar such compositions suggest that these sediments may have been inserted into the bone pore spaces in lagoons and tidal flat ponds features of some bones record their early diagenetic burial and lithification before the final redeposition the isopachous spar blocky spar and weathered pyrite document changes in the chemical composition of fluids that flowed into the bone interiors the burrow found in the marrow cavity of specimen iguam zov 7 provides evidence that some remains were inhabited by minute or juvenile invertebrates all recognised features indicate that both invertebrate and vertebrate bioclasts included in the tempestite were initially deposited in various settings of the carbonate ramp and in the end redeposited as a result of a heavy storm or a hurricane the examined bone bearing bed represents time averaged assemblage which originated due to hydraulic concentration of the vertebrate bioclasts the petrographic analysis of the fillings is a valuable tool to identify complex taphonomic pathways of vertebrate bioclasts

high resolution upb dating of middle triassic volcaniclastics time scale calibration and verification of tuning parameters for carbonate sedimentation abstract we report high resolution single zircon u pb age data for middle triassic volcaniclastic intercalations in biostratigraphically calibrated pelagic successions of the southern alps the results require a redefinition of the chronometric scale for the middle triassic moreover they do not support current models relating cyclic sedimentation in platform carbonates of the dolomites to orbital tuning tight concordant age clusters were obtained for five volcaniclastic layers in three ammonoid biozones of late anisian to early ladinian age two layers in the nevadites secedensis zone yielded identical mean 206 pb 238 u ages of 241 2 0 8 0 8 ma and 241 2 0 8 0 6 ma errors given at the 95 confidence level a layer in the gredleri zone is dated at 238 8 0 5 0 2 ma and two horizons in the archelaus zone yield similar ages of 237 9 1 0 0 7 ma and 238 0 0 4 0 7 ma these results are significantly older than the age values of 233 235 ma assigned to the anisian ladinian boundary by several current time scales 1 4 moreover our estimate of 240 7 241 3 ma depending on biostratigraphic collocation for the anisian ladinian boundary casts doubts on the reliability of age values of 245 250 ma proposed by most time scales for the permian triassic boundary the occurrence of pelagic fossils in basinal sediments as well as in age equivalent shallow marine middle triassic platform carbonates in the dolomites allows the sedimentary sequences of both environments to be correlated the 800 m thick latemar platform western dolomites is characterized by cyclic stacking patterns which have been interpreted as results of milankovitch type high frequency low amplitude sea level fluctuations the 12 m y interval of platform growth postulated from the assignment of orbital periodicities to the platform carbonate cycles 5 6 is in conflict with a maximum time span of 4 7 m y allowed by the present zircon data

bi decadal variability excited in the coupled ocean atmosphere system by strong tropical volcanic eruptions decadal and bi decadal climate responses to tropical strong volcanic eruptions sves are inspected in an ensemble simulation covering the last millennium based on the max planck institute earth system model an unprecedentedly large collection of pre industrial sves up to 45 producing a peak annual average top of atmosphere radiative perturbation larger than 1 5 wm 2 is investigated by composite analysis post eruption oceanic and atmospheric anomalies coherently describe a fluctuation in the coupled ocean atmosphere system with an average length of 20 25 years the study provides a new physically consistent theoretical framework to interpret decadal northern hemisphere nh regional winter climates variability during the last millennium the fluctuation particularly involves interactions between the atlantic meridional overturning circulation and the north atlantic gyre circulation closely linked to the state of the winter north atlantic oscillation it is characterized by major distinctive details among them the most prominent are a a strong signal amplification in the arctic region which allows for a sustained strengthened teleconnection between the north pacific and the north atlantic during the first post eruption decade and which entails important implications from oceanic heat transport and from post eruption sea ice dynamics and b an anomalous surface winter warming emerging over the scandinavian western russian region around 10 12 years after a major eruption the simulated long term climate response to sves depends to some extent on background conditions consequently ensemble simulations spanning different phases of background multidecadal and longer climate variability are necessary to constrain the range of possible post eruption decadal evolution of nh regional winter climates