enso and solar driven sub milankovitch cyclicity in the palaeogene greenhouse world high resolution pollen records from eocene lake messel germany the annually laminated oil shale from the eocene maar lake at messel germany provides unique palaeoenvironmental and palaeoclimatological information for the palaeogene greenhouse phase two palynological analyses of 6 3 and 70 kyr long records with a temporal resolution of 70 and 700 years respectively confirm vegetation and climate variability in the sub milankovitch range this variability clearly corresponds to cyclic climate fluctuations indicating the influence of solar activity and a millennial scale variability of the el nino southern oscillation also seen during the quaternary icehouse system this provides strong evidence of cyclic fluctuations in the sub milankovitch frequency band that represent a pervasive and persistent system not only of the quaternary icehouse but also throughout the entire neogene and the palaeogene greenhouse this is proof for the long term stability of the driving forces of natural climate change on earth fluctuations in the frequency of palynomorphs indicate cyclic short term quantitative changes in the composition of the vegetation these changes were related to precipitation and corresponding fluctuations of the lake level as well as to changes in pollen production transport and deposition supplementary material a complete list of variables and palynomorphs used for pollen diagrams and statistical analyses as well as additional time series analyses are available at https doi org 10 6084 m9 figshare c 3458778

search for solar periodicities in tree ring widths from concordia s c brazil tree ring studies are usually used to determine or verify climatic factors prevailing at a given place or region that may cause tree ring width variations few studies are dedicated to the solar phenomena which may underlie these tree ring width variations furthermore it is known that some terrestrial phenomena are influenced by short and long time scale solar variability an optical and computational method was set up and applied to tree samples araucaria angustifolia from santa catarina state in southern brazil in order to obtain a growth ring width mean chronology spectral analysis is used for the search of periodicities by maximum entropy and iterative regression methods the results evidenced several embedded signals at periods which may be related to solar activity variations cross correlation analysis between sunspot number and tree ring data was performed and a lag of zero year was obtained from our work it seems that the tropical conifer species araucaria angustifolia may be a good choice for studies on sun earth relationships and their regional effects

new palynology based astronomical and revised 40ar 39ar ages for the eocene maar lake of messel germany the annually laminated oil shale from the eocene maar lake at messel federal state of hessen germany provides unique paleoenvironmental data for a time interval of 640 ka during the paleogene greenhouse phase as a consequence of orbitally controlled changes in the vegetation in the vicinity of the lake the lacustrine laminites can now be astronomically tuned dating is based on the short eccentricity amplitude modulations of the regional pollen rain and their correlation to the astronomical la2010a la2010d solutions in combination with a revised 40ar 39ar age of a basalt fragment from a lapilli tuff section below the first lacustrine sediments depending on different newly suggested ages for the fish canyon sanidine used as monitor for neutron irradiation the age for the eruption at messel is between 48 27 0 22 and 48 11 0 22 ma this allows for the first time the exact correlation of a paleogene lacustrine sequence to the marine record in central europe the messel oil shale becomes now slightly older than previously assumed and includes the ypresian lutetian boundary that moves the base of the european land mammal age geiseltalian mp 11 into the lower eocene this opens a window for establishing an independent chronostratigraphic framework for paleogene terrestrial records and their correlation to the marine realm furthermore the study reveals that higher amounts of pollen from wet and thermophilous plants indicate less seasonal and more balanced precipitation and slightly higher temperatures during a well expressed eccentricity minimum

the evolution of el nino past and future abstract we review forecasts of the future of el nino and the southern oscillation enso a coupled instability of the ocean atmosphere system in the tropical pacific with global impacts enso in the modern world is briefly described and the physics of the enso cycle is discussed particular attention is given to the bjerknes feedback the instability mechanism which figures prominently in enso past and future our knowledge of enso in the paleoclimate record has expanded rapidly within the last 5 yr the enso cycle is present in all relevant records going back 130 kyr it was systematically weaker during the early and middle holocene and model studies indicate that this results from reduced amplification in the late summer and early fall a consequence of the altered mean climate in response to boreal summer perihelion data from corals shows substantial decadal and longer variations in the strength of the enso cycle within the past 1000 yr it is suggested that this may be due to solar and volcanic variations in solar insolation amplified by the bjerknes feedback there is some evidence that this feedback has operated in the 20th century and some model results indicate that it will hold sway in the greenhouse future but it is very far from conclusive the comprehensive general circulation models used for future climate projections leave us with an indeterminate picture of enso s future some predict more enso activity some less with the highly uncertain consensus forecast indicating little change

22 year solar modulation of earth s northern hemisphere temperatures as reported earlier solar particle events originating from the sun s polar regions affect the earth s troposphere in a way that is opposite to solar particle events from the sun s equatorial regions when the sun s magnetic field reverses every 11 years the tropospheric response also reverses these results are based on european temperature data the present extension 712 northern stations to a more worldwide coverage shows that this complex behavior is reversed on the western side of the earth s northern hemisphere the border separating the two regimes east vs west lies close to the meridian crossing the magnetic pole these results imply that the physical mechanism linking the solar and tropospheric changes may be sensitive to the specific spatial conditions and magnetic polarity distributions

tropical ocean atmosphere controls on inter annual climate variability in the cretaceous arctic 1 the first annually resolved sedimentary record from the cretaceous is used to develop time series of inter annual and decadal scale climate variability from the arctic ocean analysis of records spanning 1000 years reveals strong periodicities in the quasi biennial oscillation and el nino southern oscillation enso band as well as a 14 year period which all closely match periodicities typical of modern high latitude climate variability this supports the view that an arctic ocean free of permanent sea ice would be driven by similar forcing to the present state implicating tropical ocean atmosphere interaction and demonstrating that stratosphere troposphere coupling likely played a prominent role in the transmission of cretaceous equatorial climate forcing to polar latitudes as has recently been established for the modern earth system on the other hand the prominent enso periodicities in our records argue against the hypothesized link between past warm climates and permanent el nino states

isotope compositions c o sr nd of vertebrate fossils from the middle eocene oil shale of messel germany implications for their taphonomy and palaeoenvironment abstract the middle eocene oil shale deposits of messel are famous for their exceptionally well preserved articulated 47 myr old vertebrate fossils that often still display soft tissue preservation the isotopic compositions o c sr nd were analysed from skeletal remains of messel s terrestrial and aquatic vertebrates to determine the condition of geochemical preservation authigenic phosphate minerals and siderite were also analysed to characterise the isotope compositions of diagenetic phases in messel diagenetic end member values of the volcanically influenced and due to methanogenesis 12 c depleted anoxic bottom water of the meromictic eocene maar lake are isotopically very distinct from in vivo bioapatite values of terrestrial vertebrates this unique taphonomic setting allows the assessment of the geochemical preservation of the vertebrate fossils a combined multi isotope approach demonstrates that enamel of fossil vertebrates from messel is geochemically exceptionally well preserved and still contains near in vivo c o sr and possibly even nd isotope compositions while bone and dentine are diagenetically altered enamel of the hippomorph perissodactyl propalaeotherium has low 13 c values 9 0 7 typical for c 3 plant feeders dentine of the same teeth has 13 c values 15 17 higher amongst the highest 13 c bioapatite values reported for terrestrial vertebrates this reflects diagenetic carbonate exchange with the strongly 12 c depleted anoxic lake bottom water enamel 87 sr 86 sr values 0 711 0 001 are consistent with propalaeotherium feeding on palaeozoic bedrocks surrounding lake messel and suggests that the basaltic tuff ring around the maar was already eroded 640 ka after its formation dentine has however much lower volcanically influenced 87 sr 86 sr 0 706 due to diagenetic sr uptake from the lake water oil shale enamel 18 o p values 18 0 6 of propalaeotherium are 2 3 lower than those of bones and scales of aquatic vertebrates that lived in the 18 o enriched lake water using transfer functions a 18 o h 2 o value of 5 1 for meteoric water and a mat of 18 2 5 c were reconstructed for messel

holocene paleoclimate data from the arctic testing models of global climate change to evaluate the spatial variability of arctic climate change during the present interglacial cape project members compiled well dated terrestrial marine and ice core paleoenvironmental records spanning the past 10 12 thousand years ka six tundra biomes of increasing summer temperature requirements were defined based on regionally coherent pollen assemblages using a rule based approach pollen spectra were converted to tundra forest tundra or forest biomes ranked by their average growing season requirements marine sea surface reconstructions were based on proxy data following a similar rule based approach from these data based reconstructions departures in summer temperatures from modern normals were calculated in 1 ka time slices through the holocene to test predictive models data based summer temperature reconstructions were compared with general circulation model gcm simulations for 10 ka and 6 ka ago paleodata and model results both show that warming occurred earlier across beringia and asia relative to lands adjacent to the north atlantic and that late holocene cooling was most apparent in the north atlantic region however the gcm over predicts the magnitude of mid holocene warming over northern asia and underestimates the intensification of the north atlantic drift in the early holocene strong spatial variability in environmental response during the holocene despite symmetric insolation forcing suggests that any future changes whether caused by anthropogenic or natural factors are unlikely to result in a uniform change across the arctic adding additional complexity to forecasts of global impacts

search for solar periodicities in miocene tree ring widths we have analysed ring width records of two miocene coniferous trees with an absolute age of 15 20 million years such data may reflect solar periodicities from the prehistoric past evidence for a main period of 12 5 years has been found this is near the present basic solar activity period of 11 years other periodic components appear at 220 150 and 53 years respectively which may also be related to solar variations

laminated eocene maar lake sediments from eckfeld eifel region germany and their short term periodicities abstract the eocene age eckfeld eifel maar lake is interesting both because of the excellently preserved fossil remains and also for the laminated sediment sequence deposited under subtropical conditions the latitude however has a higher seasonal insolation difference than comparable recent environments due to the northward shift of climatic zones during the eocene the overall aim of this investigation was to compare sediment types and lake development of a tertiary subtropical maar lake with recent maar lakes to discuss the origin of laminations and search for their possible periodicities the main sediment types which were exposed during recent paleontological excavations are laminated oilshales partly laminated bituminous siltstones and graded beds mostly turbidites which sometimes include laminated clay tops some deeper parts of the profile drilled in 1980 are dominated by diatomaceous laminites the amount of organic carbon around 8 5 is comparable with recent lakes with low sedimentation rates the high c n ratios 25 30 of the eckfeld sediments as well as the fact that the highest corg values are found in the graded beds shows the importance of terrestrial plant debris for these lake sediments lamination of the oil shales was caused by the complex interrelationship of clastic supply mineral and plant detritus autochthonous organic deposition mainly green algae and early diagenetic siderite formation the darker sublaminae represent the coarser clastic organic and inorganic input together with the autochthonous supply from the lake green algae whereas the lighter sublaminae are composed of settled fine grained mostly siliciclastic detritus derived from the probable yearly turnover of the density stratification of the lake the thickness of the fine siliciclastic and organo clastic layers the morphology and palaeogeographical situation of the maar lake and the occurrence of algal layers strongly suggest that the laminated sediments are varves although there is no definitive proof of this thickness variations from ca 700 oil shale laminae were measured and computed time series analysis yielded at least one certain period of 5 5 yr accepting that the laminae are indeed varves the duration of the laminated lake sequence from eckfeld maar as deduced from sedimentation rates of the different sediment types is ca 82 000 yr and thus within the typical life time of other small maar lakes

periodicity in stromatolitic lamination a potential record of enso nao and sunspot in the miocene lacustrine record of the ebro basin spain abstract the spectral decomposition of time series obtained from ancient rock records can be used to study the similarity between the dynamics of present day and past climate systems a high resolution periodicity analysis of luminance and lamina thickness of lacustrine stromatolites in the ebro basin northeast of iberian peninsula reveals a significant signal of interannual and decadal climatic variability in the miocene this is one out of very few works that presents the use of spectral analysis to estimate the potential of stromatolite lamination as multiple scale recorders of climate parameters the effects of precipitation and evaporation variations on stromatolite lamination have been detected at three orders of cyclicity based on textural and high resolution stable isotope analyses c and o obtained in prior studies these analyses also revealed that the light and dark simple lamina couplets are identified with annual cycles third order isotopic cycles in the present study the spectral analysis results obtained through different paths in five stromatolite specimens reveal significant periods in the power spectrum at around 2 5 3 7 5 7 10 and 22 years these cycles can be correlated with the typical oscillation bands of different climate related agents the 2 5 year period corresponds to the quasi biennial oscillation qbo or to the biennial component of the el nino southern oscillation enso or to the north atlantic oscillation nao the 3 to 5 and 5 to 7 year bands can be linked to enso or nao variability second order isotopic cycles the 8 to 11 year bands fit the 11 year schwabe first order isotopic cycles and 22 to 23 year fit the 22 year hale sunspot cycles thus the stromatolite growth was controlled by enso nao and solar activity cycles the close relationship between these climate related agents makes it difficult to specify the dominant agent controlling the stromatolite growth nevertheless the significant periods obtained from this study within interannual 2 5 3 7 5 7 years decadal 10 22 years and even multidecadal bands 37 42 years support the existence and concurrence of enso and nao precursors during the early and middle miocene

strong evidence for the influence of solar cycles on a late miocene lake system revealed by biotic and abiotic proxies the late miocene paleogeography of central europe and its climatic history are well studied with a resolution of c 106 years small scale climatic variations are yet unresolved observing past climatic change of short periods however would encourage the understanding of the modern climatic system therefore past climate archives require a resolution on a decadal to millennial scale to detect such a short term evolution a continuous 6 m core of the paleo lake pannon was analyzed in 1 cm sample distance to provide information as precise and regular as possible measurements of the natural gamma radiation and magnetic susceptibility combined with the total abundance of ostracod shells were used as proxies to estimate millennial to centennial scale environmental changes during the mid tortonian warm period patterns emerged but no indisputable age model can be provided for the core due to the lack of paleomagnetic reversals and the lack of minerals suitable for absolute dating therefore herein we propose another method to determine a hypothetic time frame for these deposits based on statistical processes including lomb scargle and redfit periodograms along with wavelet spectra several distinct cyclicities could be detected calculations considering established off shore sedimentation rates of the tortonian vienna basin revealed patterns resembling holocene solar cycle records well the comparison of filtered data of miocene and holocene records displays highly similar patterns and comparable modulations a best fit adjustment of sedimentation rate results in signals which fit to the lower and upper gleissberg cycle the de vries cycle the unnamed 500 year and 1000 year cycles as well as the hallstatt cycle each of these cycles has a distinct and unique expression in the investigated environmental proxies reflecting a complex forcing system hence a single proxy analysis as often performed on holocene records should be considered cautiously as it might fail to capture the full range of solar cycles

a 600 k y record of el nino southern oscillation enso evidence for persisting teleconnections during the middle eocene greenhouse climate of central europe the el nino southern oscillation enso is a globally important factor in today s climate dynamics annually laminated oil shales from the maar lake of messel germany provide high resolution sedimentological and paleoenvironmental data of a time interval of 600 k y during the eocene greenhouse phase individual laminae consist of a light spring and summer algal layer tetraedron minimum layer and a dark winter layer composed of terrigenous background sediment four sections were selected from the core of the messel 2001 well in order to count varves and to measure total varve thickness and the thickness of light and dark laminae spectral analyses were done in order to detect possible cyclic fl uctuations in varve thickness fluctuations are signifi cant in the quasi biennial 2 1 2 5 yr and low frequency band 2 8 3 5 yr 4 9 5 6 yr thus showing that algal growth as well as the background sedimentation were controlled by enso effects at least over a time interval of 600 k y this confirms the existence of a previously postulated robust eocene enso significant peaks within a quasi decadal 10 11 yr interdecadal 17 26 yr and multidecadal band 52 yr 82 yr show either the enduring influence of more or less cyclic instabilities or the influence of solar cycles

el nino southern oscillation variability from the late cretaceous marca shale of california changes in the possible behavior of el nino southern oscillation enso with global warming have provoked interest in records of enso from past greenhouse climate states the latest cretaceous laminated marca shale of california permits a seasonal scale reconstruction of water column flux events and hence interannual paleoclimate variability the annual flux cycle resembles that of the modern gulf of california with diatoms characteristic of spring upwelling blooms followed by silt and clay and is consistent with the existence of a paleo north american monsoon that brought input of terrigenous sediment during summer storms and precipitation runoff variation is also indicated in the extent of water column oxygenation by differences in lamina preservation time series analysis of interannual variability in terrigenous sediment and diatom flux and in the degree of bioturbation indicates strong periodicities in the quasi biennial 2 1 2 8 yr and low frequency 4 1 6 3 yr bands both characteristic of enso forcing as well as decadal frequencies this evidence for robust late cretaceous enso variability does not support the theory of a permanent el nino in the sense of a continual el nino like state in periods of warmer climate

enso and sunspot cycles in varved eocene oil shales from image analysis abstract on the premise that sequential changes in varve thickness offer a proxy for climatic variations we investigated varve thickness in three core segments from the distal lacustrine oil shales tipton and laney members of the green river formation by means of an image analysis program of two strong bimodal periodicities one at 4 8 5 6 years is interpreted as an el nino type enso phenomenon of atmospheric dynamics while the other at 10 4 14 7 years is interpreted as the sunspot cycle originally recognized in this formation by bradley 1929 1931 weaker periodicities may exist at ca 8 and 33 years the latter also recognized by bradley taken in conjunction with the work of bradley 1929 1931 and of crowley et al 1986 this suggests that some but not all of the oil shale of the green river formation is truly varved and can be used to infer climatic time series automated instrumental scans have greatly extended the possibilities of varve studies as approaches to climatic variations in time but careful selection of facies in their geological framework is necessary

the wingeol lamination tool new software for rapid semi automated analysis of laminated climate archives geological and biological archives showing an annually laminated internal structure are currently top priority in palaeoclimate research as they are recognized as very high resolution archives of environmental change also the annual origin of laminations can be validated by absolute age dating or by using instrumental data for the most recent period microscopic laminae may span several hundreds to thousands of years and frequently reveal a high degree of internal growth variability quantitative examination of laminations using transmitted light or epifluorescence microscopy is thus a tedious task and may be partly automated we developed a software wingeol lamination tool using c capable of semi automatically detecting and measuring individual lamina thicknesses in archives showing large internal growth variability the lamination tool enables the operator to efficiently and quantitatively examine laminae down to the micron scale and it was successfully tested on a variety of annually banded samples

the pliocene paradox mechanisms for a permanent el nino during the early pliocene 5 to 3 million years ago globally averaged temperatures were substantially higher than they are today even though the external factors that determine climate were essentially the same in the tropics el nino was continual or permanent rather than intermittent the appearance of northern continental glaciers and of cold surface waters in oceanic upwelling zones in low latitudes both coastal and equatorial signaled the termination of those warm climate conditions and the end of permanent el nino this led to the amplification of obliquity but not precession cycles in equatorial sea surface temperatures and in global ice volume with the former leading the latter by several thousand years a possible explanation is that the gradual shoaling of the oceanic thermocline reached a threshold around 3 million years ago when the winds started bringing cold waters to the surface in low latitudes this introduced feedbacks involving ocean atmosphere interactions that along with ice albedo feedbacks amplified obliquity cycles a future melting of glaciers changes in the hydrological cycle and a deepening of the thermocline could restore the warm conditions of the early pliocene

the significance of maar volcanoes for palaeoclimatic studies in china abstract the sediments of maar lakes often provide paleoenvironmental records which are highly suitable for palaeoclimatic studies the main advantages of the records from maar lakes compared with other lacustrine records are as follows first the presence of varves annually laminated layers and tephra layers as well as other materials like terrestrial plant macrofossils charcoals organic carbon organic shells suitable for isotopic dating like ams 14c 210pb 137cs 238u 230th 40ar 39ar provides the possibility of developing several independent chronologies enabling the development of robust high resolution chronologies second maars and maar lakes can provide continuous sedimentary records spanning tens of thousands of years tianyang maar in china is hosted the longest known record spanning at least 400 kyr bp that are ideal for the investigation of climate change on different timescales including orbital millennial centennial and annual decadal third recent studies of biomarkers based on long chain alkenones lcas and glycerol dialkyl glycerol tetraethers gdgts have demonstrated the potential of maar lakes for quantitative paleotemperature reconstruction in this study we review some of the more significant achievements of palaeoclimatic research based on maar lake sediment sequences from china with the focus on chronology multiple timescales and quantitative paleoclimatic reconstruction

eocene el nino evidence for robust tropical dynamics in the hothouse much uncertainty surrounds the interactions between the el nino southern oscillation enso and long term global change past periods of extreme global warmth exemplified by the eocene 55 to 35 million years ago provide a good testing ground for theories for this interaction here we compare eocene coupled climate model simulations with annually resolved variability records preserved in lake sediments the simulations show pacific deep ocean and high latitude surface warming of approximately 10 degrees c but little change in the tropical thermocline structure atmosphere ocean dynamics and enso in agreement with proxies this result contrasts with theories linking past and future hothouse climates with a shift toward a permanent el nino like state

high resolution calcareous nannoplankton palaeoecology as a proxy for small scale environmental changes in the early miocene within a 5 5 m thick succession of upper burdigalian cnp zone nn4 shallow neritic sediments from the north alpine foreland basin in lower austria a high resolution section of finely laminated sediment with a thickness of 940 5 mm was logged the section was continuously sampled resulting in 100 samples covering a thickness of 10 mm each an integrated approach was applied to these samples in order to study proxy records including calcareous nannoplankton geochemical and geophysical data multivariate statistics on the autochthonous assemblage were used to evaluate the ecological preferences of each taxon and to rule out possible contamination of the signal by taphonomic processes in order to assess changes in the assemblage composition throughout the section three taphogroups were defined using both the autochthonous and allochthonous nannofossils based on the distribution of these taphogroups five distinct intervals were defined that are indicative of centennial to decadal changes in palaeoenvironmental conditions combining these results with other proxies geochemistry geophysics we were able to reconstruct short term small scale variations in terms of temperature primary productivity bottom water oxygenation organic matter flux freshwater influx and changes in relative sea level in a highly dynamic shallow marine setting this study represents the first such high resolution analysis performed on a marine succession of late burdigalian age it is also a first attempt to analyse outcrop data on such a high resolution sub milankovitch scale with respect to calcareous nannoplankton in conjunction with geochemical and sedimentological data

quasi decadal variability in paleoclimate records sunspot cycles or intrinsic oscillations 1 paleoclimatic proxies for interannual variability reveal power within the 7 15 year quasi decadal qd band in earth s history despite the fact that the best established sources of qd variability in modern climate are internal this qd variability in paleoclimatic records is commonly attributed to the 11 year sunspot cycle of solar variability intrinsic qd variability has received little attention in paleoclimatology we apply two different modeling frameworks to assess the degree to which qd variability might have occurred in the past and question whether existing paleoclimate records no matter how well resolved distinguish between internally driven and solar driven variability we show that even a simple atmospheric general circulation model gcm driven by constant solar radiation produces climate oscillations with a period of 11 years then motivated by numerous studies arguing for the presence of sunspot cycles in eocene 50 ma paleoclimate records we demonstrate that a fully coupled gcm simulation with constant solar forcing reproduces the full spectrum of reconstructed eocene variability in the examples we consider there is no compelling reason to invoke solar cycles as a cause of interpreted variability we stress the importance of identifying internal modes of variability from paleoclimate records to increase understanding of the climate system

holocene thermal maximum in the western arctic 0 180 w the spatio temporal pattern of peak holocene warmth holocene thermal maximum htm is traced over 140 sites across the western hemisphere of the arctic 0 180 w north of 60 n paleoclimate inferences based on a wide variety of proxy indicators provide clear evidence for warmer than present conditions at 120 of these sites at the 16 terrestrial sites where quantitative estimates have been obtained local htm temperatures primarily summer estimates were on average 1 6 0 8 c higher than present approximate average of the 20th century but the warming was time transgressive across the western arctic as the precession driven summer insolation anomaly peaked 12 10 ka thousands of calendar years ago warming was concentrated in northwest north america while cool conditions lingered in the northeast alaska and northwest canada experienced the htm between ca 11 and 9 ka about 4000 yr prior to the htm in northeast canada the delayed warming in quebec and labrador was linked to the residual laurentide ice sheet which chilled the region through its impact on surface energy balance and ocean circulation the lingering ice also attests to the inherent asymmetry of atmospheric and oceanic circulation that predisposes the region to glaciation and modulates the pattern of climatic change the spatial asymmetry of warming during the htm resembles the pattern of warming observed in the arctic over the last several decades although the two warmings are described at different temporal scales and the htm was additionally affected by the residual laurentide ice the similarities suggest there might be a preferred mode of variability in the atmospheric circulation that generates a recurrent pattern of warming under positive radiative forcing unlike the htm however future warming will not be counterbalanced by the cooling effect of a residual north american ice sheet

inter annual climate variability in europe during the oligocene icehouse abstract new sclerochronological data suggest that a variability comparable to the north atlantic oscillation nao was already present during the middle oligocene about 20 myr earlier than formerly assumed annual increment width data of long lived marine bivalves of oligocene 30 25 ma strata from central europe revealed a distinct quasi decadal climate variability modulated on 2 12 mainly 3 7 year cycles as in many other modern bivalves these periodic changes in shell growth were most likely related to changes in primary productivity which in turn were coupled to atmospheric circulation patterns stable carbon isotope values of the shells 13 c shell further corroborated the link between shell growth and food availability sub decal oscillations in the 3 7 year band in other annually resolved fossil archives were often interpreted as el nino southern oscillation enso cycles this possibility is discussed in the present study however combined shell derived proxy and numerical climate model data lend support to the interpretation of a nao like variability according to numerical climate models winter sea level pressure wslp and precipitation rate wpr across central europe during the oligocene exhibited a pattern similar to the modern nao the simulated nao index for the oligocene shows periodicities coherent with those revealed by the proxy data 2 5 6 years yet on shorter wavelengths than the modern nao biennial and 6 10 year cycles likely the different paleogeography and elevated atmospheric co 2 concentrations not only influenced the sea level pressure pattern but also the temporal variability of the nao precursor the present study represents the first attempt to characterize the inter annual climate variability in central europe during the oligocene and sets the basis for future studies on the early phase of the cenozoic icehouse climate state

what were the primary forcing mechanisms of high frequency holocene climate and glacier variations a compilation of holocene glacial advances throughout the world is compared with summer solar insolation integrated over the northern hemisphere and the magnitudes of global acid fallout from volcanic eruptions north of 20 s estimated from the acidity signal of annual ice layers in the crete and camp century ice cores in greenland correlation analysis between glacial advances versus volcanic eruptions yielded a correlation coefficient of r 0 71 a climatic forcing curve solar insolation and volcanic eruptions weighted 1 1 versus glacial advances increased the correlation coefficient to r 0 90 this suggests that the combined effect of volcanic aerosols and orbital related northern hemisphere summer insolation may have been the primary forcing mechanism of worldwide climate and glacier fluctuations throughout the holocene

an 825 year long varve record from lillooet lake british columbia and its potential as a flood proxy abstract lillooet river in southwest british columbia has produced damaging floods many times during the past century the floods are recorded in lillooet lake into which the river flows as anomalously thick clastic varves in order to determine whether an 825 year long varve record obtained from 12 percussion and vibracores can be used as flood proxy we compare river discharge records dating back to 1914 to the thickness of the varves deposited during the same time period correlations between varve thickness and a variety of historical discharge measures are low to moderate for the periods 1914 2004 r 2 0 37 and 1914 1945 r 2 0 40 but higher for the period 1946 2004 r 2 0 55 the best correlation r 2 0 55 is between maximum fall discharge and varve thickness during the most recent period 1946 2004 varve thickness for the earlier period of hydrometric data 1914 1946 which is a time of rapid glacier retreat and warmer temperatures in british columbia is best explained with a discharge proxy combining nival runoff glacier runoff and maximum fall discharge landslides glacier fluctuations river dyking artificial lowering of lillooet lake as well as lag effects of storms are responsible for the considerable unexplained variance in the relation between discharge measures and varve thickness over the historic period the cores contain many anomalously thick varves some of which we attribute to previously dated prehistoric landslides in the watershed or to local landslides into the lake we conclude that many historic and prehistoric floods are faithfully recorded as anomalously thick clastic varves but that other processes operating in the watershed preclude using this record as a reliable paleo flood proxy