accelerator mass spectrometry radiocarbon dating of rock varnish accelerator mass spectrometry ams 14c dating off rock varnish provides minimum limiting ages for landforms and archaeological artifacts in arid and semiarid lands that are undatable by conventional radiocarbon methods experiments on sample collection the effect of different individuals preparing samples the influence of different chemical extraction procedures the incorporation of carbonate detritus possible contamination from rock underlying varnish the role of bio geochemical erosion of varnish and other influences reveal procedures that yield reproducible results conventional radiocarbon dates from charcoal beneath lava flows of hualalai volcano hawaii and from arid sites in western north america provide controls to test varnish radiocarbon dating ams radio carbon ages on the very bottom layer of varnishes are typically 10 younger than the 14c ages of these controls applications are illustrated here for fluvial aeolian peri glacial hillslope lacustrine and glacial geo morphology as well as rock art research in archaeology

effects of geomechanical changes on the validity of a discrete fracture network representation of a realistic two dimensional fractured rock abstract this paper aims to examine the validity of the discrete fracture network dfn method in representing a realistic two dimensional fractured rock in terms of their geomechanical response to in situ stresses and hydraulic behaviour in a steady state fluid field first a real fracture network is extracted from the geological map of an actual rock outcrop which is termed the analogue fracture network afn multiple dfn realisations are created using the statistics of the analogue pattern a conductivity parameter that was found to have a linear relationship with the conductivity of 2d fracture networks is included to further enhance network similarity a series of numerical experiments are designed with far field stresses applied at a range of angles to the rock domains and their geomechanical response is modelled using the combined finite discrete element method femdem a geomechanical comparison between the afn and its dfn equivalents is made based on phenomena such as heterogeneity of fracture dependent stress contours sliding between pre existing fracture walls coalescence of propagating fractures and variability of aperture distribution furthermore an indirect hydro mechanical hm coupling is applied and the hydraulic behaviour of the porous rock models is investigated using the hybrid finite element finite volume method fefvm a further comparison is conducted focusing on the hydraulic behaviour of the afn and dfns under the effects of geomechanical changes the results show that although dfns may represent an afn quite well for fixed mechanical conditions such a representation may not be dependable if mechanical changes occur

cation ratio and accelerator radiocarbon dating of rock varnish on mojave artifacts and landforms the first accelerator radiocarbon dates of rock varnishes are reported along with potassium argon ages of lava flows and conventional radiocarbon dates of pluvial lake shorelines in an empirical calibration of rock varnish k ca 2 ti 4 ratios with age in the mojave desert eastern california this calibration was used to determine the cation ratio dates of 167 artifacts although cation ratio dating is an experimental method some dates suggest human occupation of the mojave desert in the late pleistocene

on the persistence of cold season sst anomalies associated with the annular modes abstractin this study a simple stochastic climate model is used to examine the impact of the ocean mixed layer depth surface turbulent energy fluxes and ekman currents on the persistence of cold season extratropical sea surface temperature sst anomalies associated with variability in the annular modes of atmospheric circulation in both hemispheres observational analysis reveals that during the cold season sst anomalies associated with the southern annular mode sstsam persist considerably longer than those associated with the northern annular mode sstnam using the simple model it is shown that the persistence of the cold season sstsam is consistent with the simple stochastic climate paradigm in which the atmospheric forcing is approximated as white noise and the persistence of sst anomalies can be largely determined by the thermal inertia of the ocean mixed layer in the north atlantic however the simple climate model overestimates the persistence of the cold season sstnam it is thought th

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

late quaternary geomorphology and soils in crater flat yucca mountain area southern nevada crater flat is an alluvium filled structural basin on the west side of yucca mountain nevada which is under consideration for a high level nuclear waste repository north trending late quaternary faults offset alluvium in crater flat both along the canyons of the western flanks of yucca mountain and out on the piedmont slope we believe the initial lack of young offsets at yucca mountain was in part due to unrecognized late quaternary stratigraphy we hypothesize that alluviation in the yucca mountain region was more active during the late quaternary than previously thought several techniques were tried to test this hypothesis results are compared with previous soils and surface exposure dating studies and correlated to stratigraphy of other late quaternary units in the southern nevada death valley and mojave desert areas and provide new stratigraphic data relevant to understanding climatic alluvial processes in the basin and range province during the late quaternary 76 refs 7 figs 6 tabs

cross seasonal influence of the december february southern hemisphere annular mode on march may meridional circulation and precipitation abstractnew evidence suggests that interannual variability in zonal mean meridional circulation and precipitation can be partially attributed to the southern hemisphere annular mode sam the dominant mode of climate variability in the southern hemisphere sh extratropics a cross seasonal correlation exists between the december february djf sam and march may mam zonal mean meridional circulation and precipitation this correlation is not confined to the sh it also extends to the northern hemisphere nh subtropics when the preceding djf sam is positive counterclockwise and clockwise meridional cells accompanied by less and more precipitation occur alternately between the sh middle latitudes and nh subtropics in mam in particular less precipitation occurs in the sh middle latitudes the sh tropics and the nh subtropics but more precipitation occurs in the sh subtropics and the nh tropics a framework is built to explain the cross seasonal impact of sam related sst anomalies evidence indic

significance of a midlatitude sst frontal zone in the formation of a storm track and an eddy driven westerly jet abstract in a set of idealized aquaplanet experiments with an atmospheric general circulation model to which zonally uniform sea surface temperature sst is prescribed globally as the lower boundary condition an assessment is made of the potential influence of the frontal sst gradient upon the formation of a storm track and an eddy driven midlatitude polar front jet pfj and on its robustness against changes in the intensity of a subtropical jet stj in experiments with the frontal midlatitude sst gradient as that observed in the southwestern indian ocean transient eddy activity in each of the winter and summer hemispheres is organized into a deep storm track along the sst front with an enhanced low level baroclinic growth of eddies in the winter hemisphere another storm track forms just below the intense stj core but it is confined to the upper troposphere with no significant baroclinic eddy growth underneath the near surface westerlies are strongest near the midlatitude sst front as observe

observations of large scale ocean atmosphere interaction in the southern hemisphere abstract the authors provide a detailed examination of observed ocean atmosphere interaction in the southern hemisphere sh focus is placed on the observed relationships between variability in sh extratropical sea surface temperature sst anomalies the southern annular mode sam and the el nino southern oscillation enso results are examined separately for the warm november april and cold may october seasons and for monthly and weekly time scales it is shown that the signatures of the sam and enso in the sh sst field vary as a function of season both in terms of their amplitudes and structures the role of surface turbulent and ekman heat fluxes in driving seasonal variations in the sam and enso related sst anomalies is investigated analyses of weekly data reveal that variability in the sam tends to precede anomalies in the sst field by 1 week and that the e folding time scale of the sam related sst field anomalies is at least 4 months the persistence of the sam related sst anomalies is

role of in situ cosmogenic nuclides 10be and 26al in the study of diverse geomorphic processes the central premises of applications of the in situ cosmogenic dating method for studying specific problems in geomorphology are outlined for simple and complex exposure settings in the light of these general models we discuss the information that can be derived about geomorphic processes utilizing concentrations of in situ produced cosmogenic radionuclides 10be half life 1 5 ma and 26a1 half life 0 7 ma in a variety of geomorphic contexts glacial polish and tills meteorite impact craters alluvial fans paleo beach ridges marine terraces sand dunes and bedrock slopes we also compare 10be 26al data with results obtained by other dating methods we conclude that the technique of measuring in situ cosmic ray produced nuclides holds promise for quantitative studies of processes and time scales in a wide range of geomorphological problems

wave driven zonal flow vacillation in the southern hemisphere the variability of the zonal mean flow in the southern hemisphere during the period 1985 94 is studied using european centre for medium range forecasts analyses the dominant mode of variability has approximately equivalent barotropic variations of opposite signs centered at 40 8 and 608s this structure is dominant in all seasons and has similar variance in all seasons the temporal variance of the amplitude of this mode is well modeled as gaussian red noise with a correlation e folding time of about 10 days zonal wind anomalies are maintained against frictional drag by variations in the zonal flow accelerations driven by transient eddies and associated mean meridional circulations the eddy structures suggest that equatorward propagation is favored when the jet is displaced poleward and zonal propagation is favored when the jet is displaced equatorward

on the role of extratropical air sea interaction in the persistence of the southern annular mode using the daily atmosphere and ocean reanalysis data this study highlights the role of extratropical air sea interaction in the variability of the southern annular mode sam our analysis shows that the sam induced meridional dipolar sea surface temperature sst anomalies through surface heat fluxes can maintain persistent lower tropospheric temperature anomalies which further results in anomalous eddy momentum forcing enhancing the persistence of the sam with the finite amplitude wave activity diagnosis we illustrate that response of the eddy momentum forcing to sst anomalies can be attributed to changes in both baroclinic processes as baroclinic eddy generation and barotropic processes as wave breaking thus resultant diffusive eddy mixing with the former confined at high latitudes and the latter strongest at midlatitudes spectral analysis further suggests that the above air sea interactions are important for bimonthly and longer time scale sam variations the dipolar sst pattern may be an indicator for predicting subseasonal and interseasonal variabilities of the sam

radiocarbon and cation radio ages for rock varnish on tioga and tahoe marainal boulders of pine creek eastern sierra nevada california and their paleoclimatic implications abstract accelerator mass spectrometry 14 c analyses of organic matter extracted from rock varnishes on morainal boulders yield limiting minimum ages for three crests of the tioga glaciation at pine creek in the eastern sierra nevada varnish started to form on boulders of the outermost tioga moraine before 19 000 yr b p and varnish originated on the innermost tioga moraine before 13 200 yr b p comparisons with lake level paleohydrological paleoecological colluvial and rock varnish micromorphological data indicate that central eastern california and western nevada experienced a moisture effective period during the late pleistocene but after the tioga maximum and perhaps as tioga glaciers receded from the mouth of pine creek canyon varnishes on tahoeage morainal boulders at pine creek have cation ratio ages of about 143 000 156 000 yr b p suggesting that the tahoe glaciation should not be correlated with oxygen isotope stage 4 in the early wisconsin but rather with stage 6 varnishes on morainal boulders of an older glaciation at pine creek are dated by cation ratio at about 182 000 187 000 yr b p

time varying structure of the wintertime eurasian pattern role of the north atlantic sea surface temperature and atmospheric mean flow the eurasian eu pattern was shown to be closely linked to the north atlantic sea surface temperature sst in boreal winter and this study suggest that such linkage varies with time and that the structure of the eu pattern also changes accordingly during the period with strong eu sst linkage 1961 1977 and 1993 2013 denoted as high epoch the eu pattern is a well defined barotropic wave train stretching from the north atlantic towards east asia western north pacific and it facilitates cooling and slight reduction of precipitation over east asia and enhanced precipitation over europe in its positive phase during the period with weak eu sst linkage 1948 1960 and 1978 1992 denoted as low epoch in contrast its centre over northern europe weakens sharply and the wave like structure of the eu pattern is not well established in this case its influences on precipitation over europe almost vanish but its influences on both the surface air temperature and precipitation over east asia amplify significantly the atlantic centre of the eu pattern forms from different mechanism during the two epochs it can be excited by the underlying north atlantic sst via eddy mediated processes during the high epoch while it is likely generated by an incoming rossby wave train from upstream region during the low epoch nevertheless its location and intensity remain similar during the two epochs numerical experiments with a barotropic model suggest that the contrasting structure of the eu pattern is mainly attributed to the changes of the atmospheric mean flow

routing of meltwater from the laurentide ice sheet during the younger dryas cold episode rooth1 proposed that the younger dryas cold episode which chilled the north atlantic region from 11 000 to 10 000 yr bp was initiated by a diversion of meltwater from the mississippi drainage to the st lawrence drainage system the link between these events is postulated to be a turnoff during the younger dryas cold episode of the north atlantic s conveyor belt circulation system which currently supplies an enormous amount of heat to the atmosphere over the north atlantic region2 this turnoff is attributed to a reduction in surface water salinity and hence also in density of the waters in the region where north atlantic deep water nadw now forms here we present oxygen isotope and accelerator radiocarbon measurements on planktonic foraminifera from orca basin core en32 pc4 which reveal a significant reduction in meltwater flow through the mississippi river to the gulf of mexico from about 11 200 to 10 000 radiocarbon years ago this finding is consistent with the record for lake agassiz which indicates that the meltwater from the southwestern margin of the laurentide ice sheet was diverted to the northern atlantic ocean through the st lawrence valley during the interval from 11 000 to 10 000 years before present yr bp

a linkage observed between austral autumn antarctic oscillation and preceding southern ocean sst anomalies abstractin this study the authors apply a lagged maximum covariance analysis mca to capture the cross seasonal coupled patterns between the southern ocean sea surface temperature sosst and extratropical 500 hpa geopotential height anomalies in the southern hemisphere from which nino 3 4 signals and their linear trends are removed to a certain extent statistically significant results show that the dominant feature of ocean atmosphere interaction is likely the effect of atmosphere on sosst anomalies with a peak occurring when the atmosphere leads the sosst by 1 month however the most eye capturing phenomenon is that the austral autumn atmospheric signal characterized by a negatively polarized antarctic oscillation aao is significantly related to the gradual evolution of preceding sosst anomalies suggesting that the sosst anomalies tend to exert an effect on the southern hemisphere atmospheric circulation a regression analysis based on sosst anomaly centers confirms these features it is also

fire climate and the persistence of desert varnish near dampier western australia abstract in the semi arid region near dampier discontinuous black and dark red coatings desert varnish have developed mainly on outcrops of granophyre coatings which have persisted occur on the most stable surfaces of large rather than small boulders rock coatings are absent both from fire affected outcrop margins and around sediment patches within boulder slopes and from the spray zone on the coastal margin sea level rise between about 17 000 and 6000 yr b p would have produced a landward migrating spray zone within which salt weathering probably destroyed varnish before inundation the remaining rock coatings have variable chemistry and include compound coatings with superimpositions of thin fe rich thicker si al mn fe layers and an upper coat of si al fe indicating fluctuatinng environments within major outcrops the best developed coatings occur on large and stable boulders beyond the reach of fire and salt spray and often in summit or mid slope positions much varnish loss can be attributed to factors other than climatic change with coatings presently forming at a slower rate than they are being destroyed

coupled ocean atmosphere ice response to variations in the southern annular mode abstract the coupled ocean atmosphere ice response to variations in the southern annular mode sam is examined in the national center for atmospheric research ncar community coupled climate model version 2 the model shows considerable skill in capturing the predominantly zonally symmetric sam while regional deviations between model and observation sam winds go a long way in explaining the generally small differences between simulated and observed sam responses in the ocean and sea ice systems vacillations in the position and strength of the circumpolar winds and the ensuing variations in advection of heat and moisture result in a dynamic and thermodynamic forcing of the ocean and sea ice both meridional and zonal components of ocean circulation are modified through ekman transport which in turn leads to anomalous surface convergences and divergences that strongly affect the meridional overturning circulation and potentially the pathways of intermediate water ventilation a heat budget analysis de

ambiguities in direct dating of rock surfaces using radiocarbon measurements an attempt was made to date rock surfaces with accelerator mass spectrometry ams radiocarbon measurements of rock varnishes or rock weathering rinds in two case studies samples pretreated in the laboratory of dr ronald dorn prior to ams analysis have been found to contain significant quantities of carbon rich materials of two distinct classes type i material resembles bituminous coal whereas type ii material resembles pyrolized wood charcoal fragments in samples where these type i and type ii materials were separated and ams radiocarbon dated they were found to have widely differing radiocarbon ages in these cases the measurement of the radiocarbon age of the entire sample would yield results that are at best ambiguous neither type i nor type ii materials were found in comparable samples that were independently prepared

coupled ocean atmosphere feedback in the southern annular mode abstract previous studies have demonstrated that while the southern annular mode sam is an intrinsic feature of the atmosphere it projects strongly onto the ocean and sea ice properties and circulation this study investigates the extent of back interaction whereby these oceanic sam anomalies feed back to the atmosphere a comparison between atmosphere only and full coupled climate models demonstrates that air sea interactions in the coupled system act to increase the persistence of the sam in the atmosphere to identify the nature of feedback from the ocean to the atmosphere ensemble experiments are carried out in both atmosphere only and full coupled models whereby a continuous sam like sea surface temperature sst anomaly is imposed both coupled and uncoupled experiments show a direct thermal response that affects the lower tropospheric temperature and surface meridional winds an indirect upper troposphere wide response is also seen whose characteristics are sensitive to the coupling for the

delineating the eddy zonal flow interaction in the atmospheric circulation response to climate forcing uniform sst warming in an idealized aquaplanet model the mechanisms of the atmospheric response to climate forcing are analyzed using an example of uniform sstwarminginanidealizedaquaplanet model a 200 memberensembleofexperiments isconductedwithan instantaneousuniformsstwarming thezonal meancirculationchangesdisplaya rapidpolewardshift in the midlatitude eddy driven westerlies and the edge of the hadley cell circulation and a slow equatorward contraction of the circulation in the deep tropics the shift of the poleward edge of the hadley cell is predominantlycontrolledbytheeddymomentumflux italsoshiftstheeddy drivenwesterliesagainstthesurface friction at a rate much faster than the expectation from the natural variability of the eddy driven jet i e the e folding time scale of the annular mode with much less feedback between the eddies and zonal flow the transient eddy zonal flow interactions are delineated using a newly developed finite amplitude wave activity diagnostic of nakamura applying it to the transient ensemble response to uniform sst warming reveals that the eddy driven westerlies are shifted poleward by permitting more upward wave propagation in the middle and upper troposphere rather than reducing the lower tropospheric baroclinicity the increased upward wave propagation is attributed to a reduction in eddy dissipation of wave activity as a result of a weaker meridional potential vorticity pv gradient the reduction allows more waves to propagate away from the latitudes of baroclinic generation which in turn leads to more poleward momentum flux and a poleward shift of eddy driven winds and hadley cell edge

late pleistocene charcoal in tropical atlantic deep sea sediments climatic and geochemical significance charcoal in late pleistocene marine sediments of the tropical atlantic was measured to examine the regional history of charcoal deposition as it relates to biomass burning on adjacent continents and carbon sequestration in the ocean detailed analysis 1 0 k y resolution of a deep sea core from the eastern tropical atlantic ocean reveals that charcoal from africa is a significant component of total organic carbon sedimentation during glacial intervals of the past 200000 yr these findings alter previous assumptions as to the character of carbon deposition in this region and reduce previous estimates of marine organic carbon burial fluxes by 50 furthermore the tempo of charcoal deposition is mainly linked to the growth and decay of high latitude ice sheets and appears to be caused by changes in wind strength or direction during glacial time

synchronous variability in the southern hemisphere atmosphere sea ice and ocean resulting from the annular mode zonally symmetric fluctuations of the midlatitude westerly winds characterize the primary mode of atmospheric variability in the southern hemisphere during all seasons this is true not only in observations but also in an unforced 15 000 yr integration of a coarse resolution r15 coupled ocean atmosphere model here it is documented how this mode of atmospheric variability known as the southern annular mode sam generates ocean circulation and sea ice variations in the model integration on interannual to centennial timescales that are tightly in phase with the sam the positive phase of the sam is associated with an intensification of the surface westerlies over the circumpolar ocean around 608s and a weakening of the surface westerlies farther north this induces ekman drift to the north at all longitudes of the circumpolar ocean and ekman drift to the south at around 308s through mass continuity the ekman drift generates anomalous upwelling along the margins of the antarctic continent and downwelling around 458s the anomalous flow diverging from the antarctic continent also increases the vertical tilt of the isopycnals in the southern ocean so that a more intense circumpolar current is also closely associated with positive sam in addition the anomalous divergent flow advects sea ice farther north resulting in an increase in sea ice coverage finally positive sam drives increases in poleward heat transport at about 308s while decreases occur in the circumpolar region ocean and sea ice anomalies of the opposite sign occur when the sam is negative the ocean and sea ice fluctuations associated with the sam constitute a significant fraction of simulated ocean variability poleward of 308s year round the robustness of the mechanisms relating the sam to oceanic variability suggests that the sam is likely an important source of large scale variability in the real southern hemisphere ocean

quantifying the eddy feedback and the persistence of the zonal index in an idealized atmospheric model an idealized atmospheric model is employed to quantify the strength of the eddy feedback and the persistence of the zonal index the strength of the surface frictional damping on the zonal index is varied and an external zonal momentum forcing is included to compensate for the momentum change associated with the friction change such that the climatological jet latitude and shape are unchanged the model can generate a nearly identical climatology and leading mode of the zonal mean zonal wind for different frictional damping rates except when the jet undergoes a regime transition for those experiments without a regime transition as the surface friction is increased the strength of eddy feedback is enhanced but the zonal index becomes less persistent a simple feedback model suggests that the e folding decorrelation time scale of the zonal index can be determined by the frictional damping rate and the strength of eddy feedback the strength of eddy feedback is found to be related to the instantaneous vertical wind shears near the surface controlled by the frictional damping furthermore the climate response to an external zonal torque is proportional to the decorrelation time scale although the simple prediction used here overestimates the climate response by a factor of 2

definition of antarctic oscillation index following walker s work about his thmous three oscillations published during the 1920 30s many papers were written about atmospheric oscillations a iburth atmospheric oscillation in the middle and high southern latitudes was lbund and nanted the grotarctic oscillation ao a refiers to a large scale alternation of atmospheric mass between the mid latitudes and high latitudes surthce pressure in order to understand the spatial structure of sea level pressure variation in detail empirical orthogonal fitnction analysis is applied an objective index of the antarctic oscillation index aoi is defined as the diffierence of zonal mean sea level pressure between 40os and 65os the aoi has the potential tbr clarifying climate regimes in the southern hemisphere similar to how the na and the npo has been used in the northern hemisphere were there other oscillation s besides nao npo and s especially in the southern hemisphere it had been supposed that there might be other atmospheric oscillation s in the high southern latitudes although as early as in the first quarter of this century walker 1928 had stated that just as in the north atlantic there is a pressure opposition between the azores and iceland there is an opposition between the high pressure belt across chile and the argentine on the one hand and the low pressure area of weddell sea and the bellingshausen sea on the other the scarcity of data in the southern hemisphere hindered the search tbr new oscillation s during the last two decades more comprehensive data over the southern hemisphere became available and more analyses were carried out see kidson 1975 rogers and van loon 1982 mo and l 7 ite 1985 2 4o 1986 connolley 1997 gong and wang 1998 a tburth atmospheric oscillation in the middle and high southern latitudes was tbund and nanted as the antarctic oscillation a wang 1992 gong and wang 1998 the term ao relrs to a large scale alternation of atmospheric mass between the mid latitude sur hce pressure

endolithic microorganisms in the antarctic cold desert in the frigid desert of the antarctic dry valleys there are no visible life forms on the surface of the soil or rocks yet in certain rock types a narrow subsurface zone has a favorable microclimate and is colonized by microorganisms dominant are lichens of unusual organization they survive not by physiological adaptation to lower temperatures but by changing their mode of growth being able to grow between the crystals of porous rocks their activity results in mobilization of iron compounds and in rock weatherning with a characteristic pattern of exfoliation this simple ecosystem lacks both higher consumers and predators

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

are the benches at mormon point death valley california usa scarps or strandlines the benches and risers at mormon point death valley usa have long been interpreted as strandlines cut by still stands of pluvial lakes correlative with oxygen isotope stage ois 5e 6 120 000 186 000 yr b p and ois 2 10 000 35 000 yr b p this study presents geologic mapping and geomorphic analyses gilbert s criteria longitudinal profiles which indicate that only the highest bench at mormon point 90 m above mean sea level msl is a lake strandline the other prominent benches on the north descending slope immediately below this strandline are interpreted as fault scarps offsetting a lacustrine abrasion platform the faults offsetting the abrasion platform most likely join downward into and slip sympathetically with the mormon point turtleback fault implying late quaternary slip on this low angle normal fault our geomorphic reinterpretation implies that the ois 5e 6 lake receded rapidly enough not to cut strandlines and was 90 m deep consistent with independent core studies of the salt pan no evidence of ois 2 lake strandlines was found at mormon point which indicates that the maximum elevation of the ois 2 lake surface was 30 m msl thus as measured by pluvial lake depth the ois 2 effective precipitation was significantly less than during ois 5e 6 a finding that is more consistent with other studies in the region the changed geomorphic context indicates that previous surface exposure dates on fault scarps and benches at mormon point are uninterpretable with respect to lake history

on the importance of midlatitude oceanic frontal zones for the mean state and dominant variability in the tropospheric circulation 1 observations indicate that midlatitude weather systems are organized into storm tracks near oceanic frontal zones with pronounced sea surface temperature sst gradients a pair of atmospheric general circulation model experiments with zonally uniform sst profiles prescribed show that their observed collocation is not fortuitous in one experiment a storm track is anchored around a midlatitude sst front that maintains near surface thermal gradients and energizes eddies westerly momentum transport by eddies produces a well defined polar front jet along the front even in winter when a subtropical jet stream intensifies in the other experiment removal of the sst front leads to a substantial weakening in eddy activity and the pfj especially in winter it also leads to a weakening of the annular mode the dominant mode of westerly jet variability and its notable structural distortion in winter though idealized our experiments suggest the importance of midlatitude oceanic fronts for the tropospheric circulation and its variability

relationships between mineral surfaces and organic carbon concentrations in soils and sediments abstract relationships between mineral specific surface area and organic carbon oc concentration are examined for sediments and soil a horizons from throughout the world i found published elsewhere that continental shelf sediments from many different regions exhibit downcore loss of oc to a refractory background level which shows a consistent relationship with mineral surface area slope 0 86 mg m 2 oc this trend is equivalent to a monolayer of organic matter over all surfaces and is termed the monolayer equivalent me level sediments and soils from other environments are compared to this empirically derived relationship several continental slope areas show extension of this relationship to considerable depth marked excesses of oc above this trend which persist downcore were found in sediments with high carbonate mineral content or slope sediments with low dissolved oxygen concentrations in the overlying water column about half of the soils examined also adhered to this relationship while soils with high carbonate content low ph or poor drainage showed oc concentrations higher than the me level oc concentrations below the me level are found in deltaic regions and areas with low organic matter delivery such as the deep sea or arid soils the nature of mineral surfaces was examined using n2 adsorption desorption isotherms and most surface area was found to be present as pores with