modeling co2 chemistry δ13c and oxidation of organic carbon and methane in sediment porewater implications for paleo proxies in benthic foraminifera i present a numerical diffusion advection reaction model to simulate co2 chemistry 13c and oxidation of organic carbon and methane in sediment porewater the model takes into account detailed reaction kinetics of dissolved co2 compounds h2o h oh boron and sulfide compounds these reactions are usually assumed to be in local equilibrium which is shown to be a good approximation in most cases the model also includes a diffusive boundary layer across which chemical species are transported between bottom water and the sediment water interface while chemical concentrations and 13ctco2 13ctco2 at these locations are frequently assumed equal i demonstrate that they can be quite different in this case shells of benthic foraminifera do not reflect the desired properties of bottom water even for species living at the sediment water interface z 0 cm environmental conditions recorded in their shells are strongly influenced by processes occurring within the sediment the model is then applied to settings in the santa barbara basin and at hydrate ridge cascadia margin locations of strong organic carbon and methane oxidation in contrast to earlier studies i show that a limited contribution of methane derived carbon to porewater tco2 in the santa barbara basin cannot be ruled out simulation of methane venting shows that at oxidation rates greater than fch4 50 molcm 2y 1 the 13c of porewater tco2 at z 1 cm is depleted by more than 15 relative to bottom water depletions of this magnitude have not been observed in living benthic foraminifera even at methane vents with much higher oxidation rates this suggests that foraminifera at these sites either calcify at very shallow sediment depth or during times when oxidation rates are much lower than 50 mol cm 2 y 1

foraminiferal response to an active methane seep environment a case study from the adriatic sea abstractit has been analysed the taxonomic structure and isotopic composition of the cytoplasm and tests of living rose bengal stained protoplasm full and dead empty tests benthic foraminifera 63 m in surface sediments from sites with and without methaneseepage at water depths of about 25 m water in the northern adriatic sea and compared these data to isotope analyses of carbonaterocks at the same locations foraminiferal density is higher in seep samples than in control ones despite the low oxygen and highsulphide contents in sediments the 13 c values in foraminiferal cytoplasm at the seep sites are lower than those in cytoplasm ofthe same species in control samples suggesting that beggiatoa may be a food source for the foraminifera and explaining thehigher foraminiferal density at the seep site in contrast the 13 c values of tests of living and dead benthic foraminifera at seep siteswere not significantly different from those in tests of the same species collected at the control sites therefore the carbon isotopevalues of foraminiferal tests in this area do not reflect the ones of the methane seepage although the authigenic carbonate incalcareous sandstones of the methane seepage area is significantly negative and indicates the contribution of methane seepage thesimilar carbon isotope values measured in the foraminiferal tests from shallow settings of the north eastern adriatic sea seemtherefore to be independent of methane seepages 2006 elsevier b v all rights reserved

eddy zonal flow feedback in the southern hemisphere abstract the variability of the zonal mean zonal wind in the southern hemisphere is studied using eof analysis and momentum budget diagnostics of ncep reanalysis data 1978 97 the leading eof of the zonal mean zonal wind is well separated from the remaining eofs and represents the north south movement of the midlatitude jet analysis of the momentum budget shows that a positive feedback between the zonal mean wind anomalies and the eddy momentum fluxes accounts for the unusual persistence of eof1 and plays an important role in the selection of the leading eof of midlatitude variability further analysis also shows a propagating feedback common to both eof1 and eof2 which is responsible for the poleward drift of wind anomalies with time the observations support the following feedback mechanism anomalous baroclinic wave activity is generated at the latitude of anomalous temperature gradient that by thermal wind coincides with the latitude of the anomalous zonal jet the net propagation of baroclinic

the normality of el nino the amplitude of the el nino southern oscillation enso would be normally distributed if the coupled pacific ocean atmosphere were a linear system forced by gaussian weather noise moment estimates of skewness and kurtosis demonstrate that this is not the case for monthly mean anomalies in pacific sea surface temperatures during 1950 97 the noted predominance of el nino events compared to la nina events is related to the high skewness in the eastern pacific skewness and kurtosis both exhibit an intriguing geographical variation from positive in the eastern to negative in the western pacific we have also examined nino 3 indices generated by three climate models having widely different complexity these exhibit a wide range of skewness and kurtosis values rather different from those found for the observations skewness and kurtosis can be used to diagnose non linear processes and provide powerful tools for validating models and for testing observed sea surface temperatures for the presence of possible climate change

el nino southern oscillation influences on the interannual variability of leaf appearance dates in central siberia 1 this paper analyses the role of the el nino southern oscillation enso on the interannual variability of the leaf appearance dates of boreal forests in the northern hemisphere 1982 2004 we find significant negative correlations between the enso quantified by means of the southern oscillation index soi and the leaf appearance dates in central siberia with up to 9 months lag the correlations between leaf appearance dates and summer sea surface temperatures sst show a pattern that resembles the enso phenomena with positive and significant correlations in the east pacific and negative in the west these findings are explained by the role of soi on sea level pressures 500 hpa geopotential and the wind flow direction and intensity during the months of leaf appearance april and may and on average temperatures which determine noticeably the date of leaf appearance citation vicente serrano s m n delbart t le toan and m grippa 2006 el nino southern oscillation influences on the interannual variability of leaf appearance dates in central siberia geophys res lett 33 l03707

stable isotope fractionation in benthic foraminifera from the peruvian continental margin abstract stable isotope ratios of the carbonate tests of benthic foraminifera are now widely used to reconstruct past changes in ocean circulation and chemistry such studies depend on the accuracy with which changing environmental conditions are recorded and preserved in the tests of foraminifera found in deep sea deposits assessment of this aspect of the method is best accomplished through rigorous study of modern core tops collected from a wide range of depths and bottom water temperatures stable isotope analyses of eighteen taxa of benthic foraminifera from surface sediments of the peru continental margin indicate that most foraminifera are slightly depleted in 18o relative to the benthic foram uvigerina peregrina for at least five taxa we observed subparallel 18 o temperature relationships with slopes nearly equal to that predicted by shackleton 1974 for uvigerina for seven taxa isotopic analysis of six size fractions in the range 210 590 mm reveals that with the exception of u peregrina variation between different size classes for each species is small for 18 o and for 13 c a slight inverse correlation between foraminiferal 18o and 13c content implies a complex interplay of biological and environmental factors which control isotopic composition

depth profiles of δ13c in bottom water and core top c wuellerstorfi on the ontong java plateau and emperor seamounts we have measured the carbon isotopic composition of dissolved inorganic carbon in bottom waters of the ontong java plateau western equatorial pacific and on the northern emperor seamounts northwest pacific each of these locations is several hundred miles from the nearest geochemical ocean sections study geosecs stations and the observed 13c values at each site differ substantially from regionally averaged geosecs 13c profiles we discuss the possible causes of these differences including horizontal variability near bottom effects and problems with the pacific geosecs 13c data we also measured the isotopic composition c and o of core top c wuellerstorfi from a depth transect of cores at each location the 18o data are used to verify that our samples are holocene comparison of foraminiferal and bottom water 13c values shows that this species faithfully records bottom water 13c at both sites and demonstrates that there is no depth related artifact in the dissolved inorganic carbon c wuellerstorfi 13c relationship at these sites

unusual extremes in the negative phase of the arctic oscillation during 2009 1 during 2009 the arctic oscillation ao index was exceptionally negative during four months which was unprecedented in a 60 year record extending back to 1950 the negative phase of the ao corresponded to a nearly zonally symmetric anomaly of temperature and pressure over the middle to high latitudes of the northern hemisphere consistent with the strong negative phase of the ao below average temperatures were also observed over north america and parts of eurasia during june july october and december 2009 although the impact of the ao on 2 meter temperatures was near zero when averaged over the entire hemisphere 20 90 n positive anomalies were evident in the residual pattern of observed temperature the residual along with observed below average stratospheric temperatures are consistent with anthropogenic climate projections the possible implication of the recent negative values on the long term ao trend is also discussed

recent intensified impact of december arctic oscillation on subsequent january temperature in eurasia and north africa this study reveals an intensified influence of december arctic oscillation ao on the subsequent january surface air temperature sat over eurasia and north africa in recent decades the connection is statistically insignificant during 1957 58 1979 80 p1 which becomes statistically significant during 1989 90 2011 12 p2 the possible causes are further investigated associated with positive december ao during p2 significant anomalous anticyclone emerges over the central north atlantic which is accompanied with significant westerly and easterly anomalies along 45 65 n and 20 40 n respectively this favors the significant influence of december ao on the subsequent january sat and atmospheric circulation over eurasia and north africa via triggering the north atlantic tripole sea surface temperature sst anomaly that persists into the subsequent january by contrast the december ao related anomalous anticyclone during p1 is weak and is characterized by two separate centers located in the eastern and western north atlantic correspondingly the westerly and easterly anomalies over the north atlantic ocean are weak and the related tripole sst anomaly is not well formed unfavorable for the persistent impact of the december ao into the subsequent january further analyses indicate that the different anomalous anticyclone associated with the december ao over the north atlantic may be induced by the strengthened synoptic scale eddy feedbacks over the north atlantic which may be related to the interdecadal intensification of the storm track activity additionally the planetary stationary wave related to the december ao propagates from surface into upper stratosphere at mid latitudes during p2 which further propagates downward to the troposphere and causes anomalous atmospheric circulation in the subsequent january

multiple flow regimes in the northern hemisphere winter part i methodology and hemispheric regimes abstract recurrent and persistent flow patterns are identified by examining multivariate probability density functions pdfs in the phase space of large scale atmospheric motions this idea is pursued systematically here in the hope of clarifying the extent to which intraseasonal variability can be described and understood in terms of multiple flow regimes bivariate pdfs of the northern hemisphere nh wintertime anomaly heights at 700 mb are examined in the present paper using a 37 year dataset the two dimensional phase plane is defined by the two leading empirical orthogonal functions eofs of the anomaly fields pdfs on this plane exhibit synoptically intriguing and statistically significant inhomogeneities on the periphery of the distribution it is shown that these inhomogeneities are due to the existence of persistent and recurrent anomaly patterns well known as dominant teleconnection patterns that is the pacific north american pna pattern its reverse and zonal and blocked phases of the

limits to the sensitivity of living benthic foraminifera to pore water carbon isotope anomalies in methane vent environments episodic 13c depletions in the carbon isotopic composition of benthic foraminiferal tests preserved in the stratigraphic record have been interpreted as an active incorporation of methane derived carbon understanding the extent to which these isotope excursions reflect basin wide fluxes of methane carbon to bottom waters versus a local supply of methane carbon within the sediments in which benthic foraminifera live or a postmortem diagenetic imprint is critical to the interpretation of 13c paleoceanographic proxies here we evaluate the impact of chemical gradients measured in pore waters adjacent to active methane vents on carbon assimilation by living benthic foraminifera and show that those living near methane vents do not assimilate the distinctly 13c depleted methane derived dissolved inorganic carbon into their tests from the pore water in which they were found our observations can be explained by the recently articulated physiological limits imposed on deep sea fauna by low oxygen and high pco2 environments understanding the importance of the different processes involved in the observed disequilibrium between the carbon isotopic composition of the benthic forams and the pore waters where they were found has important implications on the reliability of carbon isotopic composition of benthic foraminifera for paleoceanographic reconstructions in particular the observation on the inhospitability of these environments for benthic foraminifera at least for reproduction and growth raises the issue on the overprint either in the late adult stages of foraminifera that grew in a different neighboring environment or during early diagenesis in these geochemically active environments

acoustically detected hydrocarbon plumes rising from 2 km depths in guaymas basin gulf of california plumes extending nearly 1000 m from the 1500 2000 m deep seafloor of guaymas basin were detected from below the 23 5 khz inverted echo sounder of the scripps deep two vehicle individual sound reflectors bubbles or drops rise at approximately 17 cm s in one plume the deep tow side scan records provide more information on the plumes structure at the altitude of the vehicle 75 m where some form multiple side scan targets one 20 m across near bottom 4 khz profiles show that plumes overlie young fault traces associated with extensional faulting at the basin s spreading centers of outcrops of tilted beds beside strike slip faults we infer from analysis of the deep tow observations field relationships and knowledge of the geology of this basin that the plumes are made of light hydrocarbons perhaps mainly methane that emanate from seabed seeps one of the acoustically detected plumes was at a spreading axis hydrothermal field which has many buoyant acoustically transparent thermal plumes some of which are rich in dissolved hydrocarbons

abrupt deep sea warming palaeoceanographic changes and benthic extinctions at the end of the palaeocene a remarkable oxygen and carbon isotope excursion occurred in antarctic waters near the end of the palaeocene 57 33 myr ago indicating rapid global warming and oceanographic changes that caused one of the largest deep sea benthic extinctions of the past 90 million years in contrast the oceanic plankton were largely unaffected implying a decoupling of the deep and shallow ecosystems the data suggest that for a few thousand years ocean circulation underwent fundamental changes producing a transient state that although brief had long term effects on environmental and biotic evolution

does the oxidation of methane leave an isotopic fingerprint in the geologic record 1 pore water co2 and 13c data are presented for the dysoxic santa barbara and santa monica basins in an attempt to constrain the influence of methane oxidation on the pore water gradients and benthic foraminiferal 13c although these two basins are adjacent to one another santa barbara basin has steeper pore water co2 and 13c gradients methane oxidation could be contributing to the higher gradients in this basin the isotope mass balance for pore water co2 indicates however that the pore water gradients in the upper 2 cm of both basins are controlled only by the rate of photosynthate carbon oxidation and the rate of diffusion methane derived co2 has no discernable influence on pore water or carbonate 13c values at these sediment depths in either basin benthic foraminiferal species inhabiting different depth horizons in the top centimeter incorporate these steep isotopic gradients in their calcite tests and can be used therefore to reconstruct the history of carbon oxidation within the basins on the basis of these modern geochemical constraints a more likely explanation for the apparent 13c excursions recorded in the late pleistocene sediments from santa barbara basin involves enhanced carbon rain and carbon oxidation in the basin sediments rather than clathrate destabilization

two paradigms of baroclinic wave life cycle behaviour two idealized baroclinic wave 6 life cycles examined here suggest a framework of opposite extremes a in which to view the behaviour of real synoptic scale disturbances in middle latitudes and b in which to interrelate the synoptic and wave theoretic viewpoints using the saturation propagation saturation sps picture of wave 6 life cycle behaviour the two life cycles dented by lc1 and lc2 are higher resolution versions of the simmons hoskins basic and anomalous cases showing strong and weak late decay of eddy kinetic energy eke they illustrate in varying degrees two extreme types of behaviour here disignated anticyclonic and cyclonic and epitomized by strongly contrasting upper air trough behaviour anticyclonic behaviour dominates the late stages of lc1 and is characterized by backward tilted thinning troughs being advected anticyclonically and equatorward as in the commoner cases of planetary scale mid stratospheric rossby wave breaking cyclonic behaviour dominates lc2 and is characterized by forward tilted broadening troughs wrapping themselves up cyclonically and poleward producing major cut off cyclones in high latitudes these morphologies are visualized by upper air maps of potential temperature on the nominal tropopause defined as a constant potential vorticity surface some atmospheric mid latitude disturbances examined here using the same visualization applied to operational analyses show the same two extreme types of trough behaviour together with intermediate cases the sps picture is re examined using eliassen palm and refractive index cross sections it is shown in particular by reference to a wave activity theorem of haynes that the late stages of lc2 can be looked upon as a remarkably clear and morphologically novel large amplitude counterpart of the nonlinear reflection scenario of rossby wave critical layer theory the late stages of lc1 by constrast look more akin to an nonlinear critical layer absorption scenario lc2 exhibits region of largely undular pv contours adjacent to a nonlinear of irreversiby deformen pv contous in the latter region pv rearrangement and hence absorption of rossby wave activity has largely ceased this accounts for the more persistent ekee in the lc2 case

an increasing trend of diffuse co2 emission from teide volcano tenerife canary islands geochemical evidence of magma degassing episodes multiple soil co 2 efflux surveys have been undertaken at the summit cone of teide volcano tenerife from 1997 to 2011 to determine the total co 2 emissions from the summit cone and to evaluate the temporal variations of co 2 efflux and their relationships with seismic volcanic activity our results reveal significant fluctuations in degassing rate which do not seem to be masked by atmospheric variations these geochemical observations provide evidence for the unrest of the volcanic system as has been suggested previously by anomalous seismic activity recorded in tenerife during 22 29 april 2004 a new trend of increasing co 2 efflux and co 2 ch 4 ratio in fumarolic gas discharges was observed from 2006 to 2009 suggesting that subsurface magma movement is the cause for the observed changes in the total output of diffuse co 2 emission at the summit cone of teide

annular modes in the extratropical circulation part i month to month variability the leading modes of variability of the extratropical circulation in both hemispheres are characterized by deep zonally symmetric or annular structures with geopotential height perturbations of opposing signs in the polar cap region and in the surrounding zonal ring centered near 458 latitude the structure and dynamics of the southern hemisphere sh annular mode have been extensively documented whereas the existence of a northern hemisphere nh mode herein referred to as the arctic oscillation ao has only recently been recognized like the sh mode the ao can be defined as the leading empirical orthogonal function of the sea level pressure field or of the zonally symmetric geopotential height or zonal wind fields in this paper the structure and seasonality of the nh and sh modes are compared based on data from the national centers for environmental prediction national center for atmospheric research reanalysis and supplementary datasets the structures of the nh and sh annular modes are shown to be remarkably similar not only in the zonally averaged geopotential height and zonal wind fields but in the mean meridional circulations as well both exist year round in the troposphere but they amplify with height upward into the stratosphere during those seasons in which the strength of the zonal flow is conducive to strong planetary wave mean flow interaction midwinter in the nh and late spring in the sh during these active seasons the annular modes modulate the strength of the lagrangian mean circulation in the lower stratosphere total column ozone and tropopause height over mid and high latitudes and the strength of the trade winds of their respective hemispheres the nh mode also contains an embedded planetary wave signature with expressions in surface air temperature precipitation total column ozone and tropopause height it is argued that the horizontal temperature advection by the perturbed zonal mean zonal wind field in the lower troposphere is instrumental in forcing this pattern a companion paper documents the striking resemblance between the structure of the annular modes and observed climate trends over the past few decades

observed relationships between the el nino southern oscillation and the extratropical zonal mean circulation abstract there is increasing evidence indicating that the climate response to variations in the el nino southern oscillation enso includes not only thermally forced zonal wind anomalies in the subtropics but also eddy driven zonal wind anomalies that extend into the mid high latitudes of both hemispheres in this study new insights into the observed seasonally varying signature of enso in the extratropical zonal mean circulation are provided and the associated linkages with the dominant patterns of extratropical variability are examined the zonal mean extratropical atmospheric response to enso is characterized by two principal features an equivalent barotropic dipole in the southern hemisphere sh zonal mean zonal flow with centers of action located near 40 and 60 during austral summer and a weaker but analogous dipole in the northern hemisphere nh with centers of action located near 25 and 45 during early and late boreal winter both structures are accompanied by eddy momentum flux ano

relationships between the distribution and stable isotopic composition of living benthic foraminifera and cold methane seep biogeochemistry in monterey bay california 1 as part of an ongoing effort to explore the use of foraminifera as a means to assess modern and ancient methane release we compared ambient pore water chemistry with the distribution and stable isotopic composition of living rose bengal stained foraminifera in mbari rov ventana tube cores taken from modern seepage areas about 1000 m water depth in monterey bay california benthic foraminiferal isotopic differences between sites clearly indicate that methane influenced pore waters affect foraminiferal distributions and carbonate isotope geochemistry carbon isotope signatures of living benthic foraminifera did not conform to the very negative 30 to 48 methane influenced carbon isotope values of the pore waters they live in instead the influence of methane seep pore waters was reflected in the greater range and carbon isotopic variability of living seep foraminifera compared with published 13c values of foraminifera living in nonseep habitats it is not clear what relative influences biological ecological and physical factors have on the carbon isotopic signatures observed in seep foraminifera substantial carbon isotope differences can exist between individuals of the same seep species for instance 13c values of living globobulimina pacifica varied by as much as 2 9 between seeps within 8 km of each other whereas 13c values of living uvigerina peregrina varied by as much as 1 95 within the same seep provided there is no diagenetic alteration of the test carbonate isotopic results of individual seep foraminifera support the hypothesis that foraminifera can be used to assess past and present methane seepage

benthic pelagic coupling in the southern california bight relationships between sinking organic material diatoms and benthic foraminifera abstract in an effort to understand the relationship between surface water processes and seafloor sediment characteristics in the southern california bight opal concentrations organic carbon weight percent measurements diatom abundances and assemblages and living benthic foraminiferal abundances were examined in surface sediments from two sites along the continental margin of southern california although opal and organic carbon weight percentages in the top 1 cm of surface sediments reflect spatial changes in productivity between sites our results indicate that they are not sensitive indicators of seasonal changes in surface water productivity at either site the close correspondence between seasonal diatom flux in the adjacent santa barbara basin sbb abundances of diatoms indicative of upwelling conditions and opportunistic benthic foraminifera indicate that there is a rapid weeks to months opportunistic response of the benthic species nonionella fragilis to input from changes in surface water characteristics these results highlight the close association of surface water conditions and preservable microfauna and flora and confirm the influence of surface characteristics on seafloor ecosystems in bathyal environments on the california margin additional information on these associations will further improve our ability to discern seasonal and spatial changes in paleoproductivity from the geologic record

boreal winter links between the madden julian oscillation and the arctic oscillation abstract there is increasing evidence that the madden julian oscillation mjo modifies the mid to high latitude circulation and in particular appears to have a relationship to the leading mode of extratropical variability the arctic oscillation ao in this study new insights into the observed similarities between the mjo and the ao are explored it is shown that the eastward progression of the convectively active phase of the mjo is associated with a corresponding shift in the tendency and sign of the ao index moreover the ao and the mjo share several analogous features not only in the global circulation but also in surface temperature fields also the ao is linked to a pattern of eastward propagating mjo like variability in the tropics that is partially reproduced in free runs of the ncep climate forecast system cfs model finally it is shown that the structure of the ao as defined by the leading mode in the 1000 hpa geopotential height field is significantly altered based on the phase o

patterns of wintertime jet stream variability and their relation to the storm tracks abstract a new approach is put forward for defining extratropical teleconnection patterns the zonal wind field at 250 hpa is analyzed separately in the north atlantic and north pacific ocean sectors during the winter season december march teleconnectivity of this field is found to be particularly strong eof analysis of the zonal wind field yields patterns that i are robust with respect to the range of frequencies included in the data ii relate clearly to the position of the climatological mean jets and iii are broadly consistent with their traditionally defined counterparts in terms of climatic impacts the patterns are characterized by a north south shifting or an extension retraction of the eddy driven jet in its exit region and similar changes at the entrance region of the subtropical jet the patterns also reflect the degree of separation between the subtropical and eddy driven jets atlantic eofs 1 and 2 are counterparts of the north atlantic oscillation nao and eastern atlantic patter

relations between annular modes and the mean state southern hemisphere winter in a zonally symmetric climatology with a single eddy driven jet such as prevails in the southern hemisphere summer the midlatitude variability is dominated by fluctuations of the jet around its mean position as described by the southern hemisphere annular mode sam to study whether this result holds for a zonally asymmetric climatology the observed variability of the southern hemisphere winter is analyzed the mean state in this case is characterized by relatively weak stationary waves yet there exist significant zonal variations in the mean strength and meridional structure of the subtropical jet stream as in summer the winter sam signature is annular in shape and the corresponding wind anomalies are dipolar but it is associated with two different behaviors of the eddy driven jet in different longitudinal ranges over the indian ocean the sam is associated primarily with a latitudinal shift of the jet around its mean position over the pacific sector it is instead characterized by a seesaw in the wind speed between two distinct latitudes corresponding to the positions of the midlatitude and subtropical jets composites of eddy forcing and baroclinicity over both sectors appear consistent with the two different behaviors as in the zonal mean case high frequency eddies both force and maintain the low frequency wind anomalies associated with the sam the positive feedback by eddies is however not local changes in the eddy forcing are influenced most strongly by zonal wind anomalies located upstream

the preferred structure of variability of the northern hemisphere atmospheric circulation a nonlinear generalisation of principal component analysis pca is applied to the 500mb geopotential height field of the northern hemisphere extratropical atmosphere it is found that the low frequency variability of the mid troposphere is characterised by three distinct quasi stationary states the states are described and compared to those obtained from applications of cluster analyses and linear pca to the height field evidence is provided that modes obtained through pca notably the arctic oscillation ao are not independent dynamical modes of variability of the northern hemisphere extratropics rather they arise as the optimal linear compromise between the preferred quasi stationary states of the circulation

rotational atmospheric circulation during north atlantic european winter the influence of enso the dominant variability modes of the north atlantic european rotational flow are examined by applying a principal component analysis pca eof to the 200 hpa streamfunction mid winter anomalies jan feb monthly means the results reveal that when this norm is used the leading mode eof1 does not correspond to the traditional north atlantic oscillation nao which appears in our analysis as the second leading mode eof2 but is the local manifestation of the leading hemispheric streamfunction eof the regression of this regional mode onto the global sst field exhibits a clear el nino signature with no signal over the atlantic while the associated upper height anomalies resemble the tropical northern hemisphere tnh pattern east of north america this tnh like wavetrain produces a meridional dipole like pattern at lower levels although in some ways this pattern resembles the nao eof2 the dynamics of these two modes are very different in that only eof2 is associated with a latitudinal shift of the north atlantic stormtrack thus the choice of the streamfunction norm in the eof analysis allows the separation of two different phenomena that can produce similar dipolar surface pressure anomalies over the north atlantic but that have different impact on european climate these two modes also differ on their contribution to variability at lower levels while nao eof2 is mostly confined to the north atlantic tnh eof1 has a more annular global character at upper levels nao eof2 also produces a global pattern but with no annular structure reminiscent of the circumglobal teleconnection

isotope paleontology growth and composition of extant calcareous species abstract isotope paleontology uses the isotopic composition of fossil remains of organisms to make inferences about the physical surroundings of growth of the organisms especially temperature and to obtain clues about life history and modes of growth in calcareous fossils oxygen isotopes are mainly used in the former and carbon isotopes in the latter however since physical surroundings and organism response are intimately associated both types of information are contained in each of the isotopic signals to explore the potential of isotope paleontology and to provide a basis for reconstruction a broad range of extant organisms has been studied taking the pioneering work of epstein and associates as a starting point results are summarized for a representative sampling of these studies with emphasis on work at the laboratories of the authors from the mid seventies to the present the organisms considered are nannoplankton benthic algae planktonic and benthic deep sea foraminifera larger foraminifera sponges corals bryozoans polychaetes arthropods bivalves gastropods cephalopods and vertebrates fish otoliths the survey broadly suggests that regarding oxygen isotopes materials tend to be precipitated close to equilibrium with the surrounding seawater as postulated by urey and that for carbon isotopes disequilibrium is the rule life spans growth rates differential seasonal growth and age of reproductive activity can be extracted under favorable circumstances from individual shells and skeletal parts in detail the interpretation of isotope records of individual shells is quite complicated and simple models will fail to give satisfactory results in many or most cases

observational constraints on the tropospheric and near surface winter signature of the northern hemisphere stratospheric polar vortex a composite analysis of northern hemisphere s mid winter tropospheric anomalies under the conditions of strong and weak stratospheric polar vortex was performed on ncep ncar reanalysis data from 1948 to 2013 considering as additional grouping criteria the coincidental states of major seasonally relevant climate phenomena such as el nino southern oscillation enso quasi biennial oscillation and strong volcanic eruptions the analysis reveals that samples of strong polar vortex nearly exclusively occur during cold enso states while a weak polar vortex is observed for both cold and warm enso the strongest tropospheric and near surface anomalies are found for warm enso and weak polar vortex conditions suggesting that internal tropospheric circulation anomalies related to warm enso constructively superpose on dynamical effects from the stratosphere additionally substantial differences are found between the continental winter warming patterns under strong polar vortex conditions in volcanically disturbed and volcanically undisturbed winters however the small size samples obtained from the multi compositing prevent conclusive statements about typical patterns dominating effects and mechanisms of stratosphere troposphere interaction on the seasonal time scale based on observational reanalysis data alone hence our analysis demonstrates that patterns derived from observational reanalysis time series need to be taken with caution as they not always provide sufficiently robust constraints to the inferred mechanisms implicated with stratospheric polar vortex variability and its tropospheric and near surface signature notwithstanding this argument we propose a limited set of mechanisms that together may explain a relevant part of observed climate variability these may serve to define future numerical model experiments minimizing the sample biases and thus improving process understanding

relation between annular modes and the mean state southern hemisphere summer abstract the annular modes emerge as the leading mode of extratropical month to month climate variability in both hemispheres here the influence of the background state on the structure and dynamics of the southern hemisphere annular mode sam during the austral summer when the climatology is characterized by a single well defined eddy driven jet is studied subsets of the climatology are constructed for early and late summer and for contrasting polarities of the enso cycle the analysis is based both on observations and on perpetual state gcm experiments the main differences between the subsets involve variations of the latitude of the mean jet it is found that in all the cases the sam is characterized by latitudinal shifts of the jet about its mean position reinforced by a positive momentum flux feedback from baroclinic waves this result is consistent with previous studies of the dynamics of the zonally averaged circulation but is found here to hold over all longitudes and for different positi

the interaction of the madden julian oscillation and the arctic oscillation abstract tropical and extratropical interactions on the intraseasonal time scale are studied in the context of the arctic oscillation ao and the madden julian oscillation mjo to simplify the discussion a high low mjo phase is defined as strong suppressed convective activity over the indian ocean in the northern hemisphere nh winter season a high low ao phase is found more likely coupled with a high low mjo phase based on the regressed patterns and composites of various dynamical fields and quantities possible mechanisms linking the ao and the mjo are examined the analysis indicates that the mjo influence on extratropical circulations seems more evident than the ao influence on tropical circulations the mjo interacts with the ao through meridional dispersion of rossby waves in the pacific sector the geopotential height anomaly center over the north pacific associated with the mjo can either reinforce or offset the ao pacific action center as a result the ao pattern can be greatly a

the signature of the annular modes in the tropical troposphere the extratropical annular modes are coupled with a distinct pattern of climate anomalies that spans the circulation of the tropical troposphere the signature of the annular modes in the tropical troposphere exhibits a high degree of equatorial symmetry it is associated with upper tropospheric zonal wind anomalies centered about the equator midtropospheric temperature anomalies located 208n and 208s and opposing mean meridional circulation anomalies that span the subtropics of both hemispheres the linkages between the annular modes and the tropical circulation are only evident during the cold season months and are most robust in association with the northern hemisphere annular mode nam the coupling between the annular modes and the circulation of the tropical troposphere is consistent with forcing by waves originating at extratropical latitudes both annular modes are characterized by anomalies in the eddy momentum flux convergence at tropical latitudes that act to reinforce the changes in the tropical wind and temperature fields the most pronounced tropical anomalies lag indices of the annular modes by 2 weeks and are found over the eastern tropical pacific where climatological westerlies permit extratropical waves to propagate into the deep tropics the linkages between the nam and the tropical tropospheric circulation are

enso influence on the north atlantic european climate a non linear and non stationary approach el nino southern oscillation enso impact on the north atlantic european sector nae is still under discussion recent studies have found a non stationary feature of this teleconnection suggesting an effective modulating role of the ocean mean state nevertheless physical explanations about the underlying mechanisms have been little studied in the available literature in addition enso events show different sst spatial patterns phases and amplitudes which can also influence on the related remote impacts in view of all this in the present study a set of partially coupled experiments have been performed with a global atmospheric general circulation model in which different sst enso patterns are superimposed over distinct pacific and atlantic sst mean states these sst background conditions are constructed according to the observational difference between periods with a distinct impact of enso on the leading euro mediterranean rainfall mode in late winter early spring our results point to two distinct mechanisms associated with enso that can be modulated by the sst mean state 1 the thermally driven direct circulation walker and hadley cells connecting the atlantic and pacific basins and 2 the rossby wave propagation from the tropical pacific to the north atlantic the former elucidates that the positive nao like pattern usually related to la nina events could be only valid for selected decades the latter explains a reinforced signature of eastern pacific ninos on the euro mediterranean rainfall when the tropical pacific is warmer than usual and the north atlantic is colder than usual this feature is consistent with the changing enso impact identified in previous studies and demonstrates how the enso teleconnection with the nae climate at interannual timecales could be modulated by multidecadal changes in the sst according to our results the assumption of stationarity which is still common to many studies of enso teleconnections clearly has to be questioned

volcanic eruptions large scale modes in the northern hemisphere and the el nino southern oscillation abstract the author analyzes the impact of 13 major stratospheric aerosol producing volcanic eruptions since 1870 on the large scale variability modes of sea level pressure in the northern hemisphere winter the paper focuses on the arctic oscillation ao and the north atlantic oscillation nao to address the question about the physical nature of these modes the hypothesis that the phase of the el nino southern oscillation enso may control the geographical extent of the dominant mode in the northern hemisphere is also investigated as well as the related possibility that the impact of the eruptions may be different according to the phase of enso the author finds that both the ao and the nao are excited in the first winter after the eruptions with statistical significance at the 95 level both the signal and the significance are larger for the nao than for the ao the excitation of the ao and the nao is connected with the excitation of a secondary mode which resembles an augmented pacific north ame

spring arctic oscillation east asian summer monsoon connection through circulation changes over the western north pacific in the present study the links between spring arctic oscillation ao and east asian summer monsoon easm was investigated with focus on the importance of the north pacific atmospheric circulation and sea surface temperature sst to reduce the statistical uncertainty we analyzed high pass filtered data with the inter annual time scales and excluded the el nino southern oscillation signals in the climate fields using a linear fitting method the significant relationship between spring ao and easm are supported by the changes of multi monsoon components including monsoon indices precipitation and three dimensional atmospheric circulations following a stronger positive spring ao an anomalous cyclonic circulation at 850 hpa appears in southeastern asia and the western north pacific in summer with the easterly anomalies spanning from the pacific to asian continent along 25 n 30 n and the westerly anomalies south of 15 n at the same time the summer western north pacific subtropical high becomes weaker consistently the positive precipitation anomalies are developed over a broad region south of 30 n stretching from southern china to the western pacific and the negative precipitation anomalies appear in the lower valley of the yangtze river and southern japan the anomalous cyclone in the western north pacific persisting from spring to summer plays a key role in modulating easm and monsoon precipitation by a positive air sea feedback mechanism during spring the ao associated atmospheric circulation change produces warmer ssts between 150 e 180 near the equator the anomalous sensible and latent heating in turn intensifies the cyclone through a gill type response of the atmosphere through this positive feedback the tropical atmosphere and sst patterns sustain their strength from spring to summer that consequently modifies the monsoon trough and the western north pacific subtropical high and eventually the easm precipitation moreover the sst response to ao circulation is supported by the numerical simulations of an ocean model and the anomalous atmospheric circulation over the western north pacific is also reproduced by the dedicated numerical simulations using the coupled atmosphere ocean model the observation evidence and numerical simulations suggest the spring ao can impact the easm via triggering tropical air sea feedback over the western north pacific

response of baroclinic life cycles to barotropic shear abstract cyclonic barotropic shear of incrementally increasing magnitude is imposed on an idealized midlatitude jet and the life cycles of baroclinically unstable wavenumber 6 perturbations growing on these jets are studied when the barotropic shear parameter passes a critical value the life cycle makes an abrupt transition from anticyclonic to cyclonic behavior the abrupt transition in behavior is most evident in the barotropic decay of eddy kinetic energy in the structure of the eddies as seen in potential vorticity maps and in the nature of the zonal flow accelerations produced during the life cycle it is suggested that the abrupt transition can be interpreted as arising from a positive feedback between eddy propagation and eddy induced zonal flow accelerations dependences on the zonal scale of the eddy are also investigated wavenumber 8 exhibits cyclonic behavior while wavenumber 4 exhibits anticyclonic behavior for all values of cyclonic shear considered this dependence on zonal scale is c

interdecadal variations in northern hemisphere winter storm track intensity abstract in this paper the interannual variations in the northern hemisphere winter storm tracks have been examined based on 51 winters december january february of ncep ncar reanalysis data the leading empirical orthogonal function eof corresponds to the simultaneous strengthening weakening of both the pacific and atlantic storm tracks interannual and month to month variations in the pacific and atlantic storm tracks are found to be significantly correlated the principal component associated with the leading hemispheric eof exhibits pronounced interdecadal variability there appears to be a transition during the early 1970s from a weak storm track state prior to 1972 73 to a strong storm track state subsequently decadal mean storm track intensity during the 1990s is about 30 stronger than that during the late 1960s and early 1970s the relationship between variations in storm track intensity and low frequency seasonal mean flow anomalies has also been examined it is shown that storm track va

dependence of the structure of the northern hemisphere annular mode on the polarity of enso 1 the structure of the northern hemisphere annular mode nam is shown to be significantly different during warm and cold winters of the enso cycle during warm winters the arctic center of action of the annular mode is more prominent and extends deeper into siberia its related surface air temperature signal is stronger and the compensating outer ring in the sea level pressure field is much broader encompassing the entire tropics during cold winters the nam signature is much more pronounced over the pacific sector the sea level pressure pattern exhibits a north pacific center of action positively correlated with the atlantic center and pronounced deflections of the storm track are also evident it is suggested that the former features are associated with the equatorward displacement of the jet stream and the storm tracks during warm winters of the enso cycle and the latter is related to the the more pronounced break in the subtropical jet stream over the pacific sector during cold winters

interannual variability of tehuantepec eddies 1 topex poseidon satellite altimeter observations and the naval research laboratory layered ocean model simulations show interannual variability in the number and intensity of tehuantepec eddies off the mexican southwest coast analysis of the results illustrates that downwelling coastally trapped waves which are generated in the equatorial pacific play a crucial role in the modulation and generation of tehuantepec eddies and a dominant role in tehuantepec eddy interannual variability this introduces a new paradigm in which the generation and modulation of tehuantepec eddies is not exclusively explained in terms of the strong and intermittent tehuantepec wind events in fact the results show anticyclonic eddy formation during periods of calm tehuantepec winds that is specifically exemplified by the formation of two anticyclonic tehuantepec eddies during a 5 month period of weak gulf of tehuantepec winds during summer of 1997 furthermore the satellite observed and nlom simulated proliferation of tehuantepec eddies during el nino years is explained by the corresponding increase in downwelling coastally trapped waves and a lack of increase in the number and strength of tehuantepec wind events during el nino years

stratosphere troposphere evolution during polar vortex intensification stratosphere troposphere evolution associated with polar vortex intensification vi events is examined during the northern hemisphere winter the incipient stage of a vi event is marked by anomalously low wave activity and descending westerly anomalies over the depth of the polar stratosphere reduced poleward planetary wave heat flux occurs as the circumpolar wind becomes strongest and pressure anomalies penetrate toward the surface descending pressure patterns project strongly onto the positive state of the northern hemisphere annular mode nam concurrently anomalous poleward momentum flux develops in the upper troposphere and the related tropospheric mean meridional circulation maintains the attendant wind and temperature anomalies against surface drag the gross behavior of the composite vi event is similar in shape but opposite in sign to that associated with sudden stratospheric warming events ssws however the descent of the wind and temperature anomalies over the vi life cycle is generally weaker and slower than its ssw counterpart preceding the maximum vortex anomaly similarly after the maximum wind event the weakening of the winds is faster than the strengthening of the winds after a ssw this is because stratospheric wind reduction anomalies are produced by wave driving which can be rapid and increases in wind speed are associated with the radiative cooling of the polar cap which happens more gradually while the contributions of the anomalous momentum fluxes by the quasi stationary and synoptic eddies are similar to ssws the much stronger anomalous momentum flux observed during vi can be attributed to the larger role of eddies with timescales between 15 and 40 days and of wave number 2 scale notable differences between vi and ssw appear in the tropical region in particular anomalous vortex intensification seems to occur preferentially during la nina conditions

zonal asymmetry of the annular mode and its downstream subtropical jet an idealized model study abstractthis study investigates linkages between the zonal asymmetry of the annular mode am zonal pattern and the subtropical jet stj over its downstream regions of the storm track by using an idealized model observational analyses show that the am zonal patterns are more zonally asymmetric during days when the stj downstream of the storm track is unusually strong and vice versa in the idealized model the stj downstream of the storm track is varied by introducing an additional zonally localized tropical heating the model s am variability exhibits a nearly zonally uniform structure when there is no or only weak tropical heating however the signatures of the am are locally strengthened in the heating sector thus the am zonal pattern is zonally asymmetric when the tropical heating is large enough to create a strong stj the model results also show that the percentage of the variance explained by the am the persistence of the am index and the intensity of eddy feedback are also increased when t

the arctic oscillation signature in the wintertime geopotential height and temperature fields the leading empirical orthogonal function of the wintertime sea level pressure field is more strongly coupled to surface air temperature fluctuations over the eurasian continent than the north atlantic oscillation nao it resembles the nao in many respects but its primary center of action covers more of the arctic giving it a more zonally symmetric appearance coupled to strong fluctuations at the 50 hpa level on the intraseasonal interannual and interdecadal time scales this arctic oscillation ao can be interpreted as the surface signature of modulations in the strength of the polar vortex aloft it is proposed that the zonally asymmetric surface air temperature and mid tropospheric circulation anomalies observed in association with the ao may be secondary baroclinic features induced by the land sea contrasts the same modal structure is mirrored in the pronounced trends in winter and springtime surface air temperature sea level pressure and 50 hpa height over the past 30 years parts of eurasia have warmed by as much as several k sea level pressure over parts of the arctic has fallen by 4 hpa and the core of the lower stratospheric polar vortex has cooled by several k these trends can be interpreted as the development of a systematic bias in one of the atmosphere s dominant naturally occurring modes of variability

a time series study of the carbon isotopic composition of deep sea benthic foraminifera 1 variation of the 13c of living rose bengal stained deep sea benthic foraminifera is documented from two deep water sites 2430 and 3010 m from a northwest atlantic ocean study area 275 km south of nantucket island the carbon isotopic data of hoeglundina elegans and uvigerina peregrina from five sets of multicorer and soutar box core samples taken over a 10 month interval march may july and october 1996 and january 1997 are compared with an 11 5 month time series of organic carbon flux to assess the effect of organic carbon flux on the carbon isotopic composition of dominant taxa carbon isotopic data of hoeglundina elegans at 3010 m show 0 3 lower mean values following an organic carbon flux maximum resulting from a spring phytoplankton bloom this 13c change following the spring bloom is suggested to be due to the presence of a phytodetritus layer on the seafloor and the subsequent depletion of 13c in the pore waters within the phytodetritus and overlying the sediment surface carbon isotopic data of h elegans from the 2430 m site show an opposite pattern to that found at 3010 m with a 13c enrichment following the spring bloom this different pattern may be due to spatial variation in phytodetritus deposition and resuspension or to a limited number of specimens recovered from the march 1996 cruise the 13c of uvigerina peregrina at 2430 m shows variation over the 10 month interval but an analysis of variance shows that the variability is more consistent with core and subcore variability than with seasonal changes the isotopic analyses are grouped into 100 m size classes on the basis of length measurements of individual specimens to evaluate 13c ontogenetic changes of each species the data show no consistent patterns between size classes in the 13c of either h elegans or u peregrina these results suggest that variation in organic carbon flux does not preferentially affect particular size classes nor do 13c ontogenetic changes exist within the 250 to 750 m size range for these species at this locality on the basis of the lack of ontogenetic changes a range of sizes of specimens from a sample can be used to reconstruct 13c in paleoceanographic studies the prediction standard deviation which is composed of cruise core subcore and residual replicate variability provides an estimate of the magnitude of variability in fossil 13c data it is 0 27 for h elegans at 3010 m and 0 4 for u peregrina at the 2430 m site since these standard deviations are based on living specimens they should be regarded as minimum estimates of variability for fossil data based on single specimen analyses most paleoceanographic reconstructions are based on the analysis of multiple specimens and as a result the standard error would be expected to be reduced for any particular sample the reduced standard error resulting from the analysis of multiple specimens would result in the seasonal and spatial variability observed in this study having little impact on carbon isotopic records

transport mechanism and paleoclimatic significance of terrigenous silt deposited in varved sediments of an african rift lake we analyzed a varved sequence of sediment from a 350 m depth in the north basin of lake malawi east africa for the size distribution of the sortable silt fraction 10 64 m mean size of the sortable silt mean ss varies measurably in sediments spanning the past 650 yr and covaries with the mass accumulation rate of terrigenous silt and clay tmar over much of the interval most of the silt and clay is delivered to the offshore basin in benthic nepheloid plumes of unknown duration and frequency tmar appears to be related to annual rainfall which is related to the north atlantic oscillation because it roughly tracks the historical record of lake level that extends back to 1860 mean ss should be related to density or thickness of underflow thus related to resuspension intensity or river flood loading it also tracks lake level and regional wind strength as determined by national center for environmental prediction ncep reanalysis

el nino la nina and the nonlinearity of their teleconnections the paradigm of an atmospheric system varying linearly with respect to extreme phases of the el nino southern oscillation is questioned it is argued that the global response to tropical pacific sea surface temperature forcing will be inherently nonlinear a physical basis for this intrinsic nonlinearity is the thermodynamic control on deep convection climate statistics for warm and cold events of the tropical pacific are analyzed separately for the northern winter periods during 1950 96 composite analysis of 500 mb heights reveal planetary scale teleconnection patterns as noted in earlier studies a new result is the evidence for an appreciable 358 longitude phase shift between the warm and cold event circulation composites and the two wave trains appear to have different tropical origins a large nonlinear component in north american surface climate anomalies is also found which is consistent with such a phase shift in teleconnections in the tropics rainfall anomalies also show evidence of nonlinear behavior the maximum rain anomalies along the equator are located east of the date line during warm events but west of the date line during cold events the interpretation of this behavior is complicated however by the fact that composite warm event sst anomalies are not the exact inverse of their cold event counterparts idealized atmospheric general circulation model agcm experiments are performed in order to test the question of whether the observed nonlinearity is an intrinsic property of the atmospheric system the model is forced with a composite sst anomaly that undergoes a realistic seasonally varying enso life cycle as described by e rasmusson and t carpenter both positive and negative phases of the sst anomaly are used and a 40 member ensemble of warm and cold event model simulations is conducted a nonlinear climate response in the agcm is found that closely resembles the observed composites including a shift in the equatorial positions of the maxmium rain responses and a phase shift of teleconnection patterns in the upper troposphere barotropic model experiments indicate that the inherent nonlinearity in the tropical rain response may itself be responsible for the phase shift in the extratropical teleconnection patterns

eddy zonal flow feedback in the northern hemisphere winter abstract the variability of the zonal mean zonal wind in the northern hemisphere winter december march is studied using eof analysis and momentum budget diagnostics of ncep ncar reanalysis data 1976 2001 the leading eof of the zonal mean zonal wind is well separated from the remaining eofs and represents the north south movement of the midlatitude westerlies analysis of the momentum budget shows that a positive feedback between the zonal mean wind anomalies and the eddy momentum fluxes selects the leading eof of midlatitude variability like the southern hemisphere the baroclinic eddies reinforce the zonal wind anomalies while external rossby waves damp the wind anomalies in the northern hemisphere the quasi stationary eddies also reinforce the zonal wind anomalies but the baroclinic eddies are most important for the positive eddy zonal flow feedback the observations support the following feedback mechanisms 1 above normal baroclinic wave activity is generated in the region of enhanced wester