a generalized additive model for the spatial distribution of stable isotopic composition in antarctic surface snow abstract using the most recent compilation of surface antarctic snow isotopic composition data and a 1 km resolution digital elevation model dem a generalized additive model gam was used to develop a new gridded map of stable isotopic composition in antarctic surface snow the model explained 93 9 of the observed variance in the 18 o data 92 7 of the observed d variance and 66 6 of the observed deuterium excess the performance of the model was evaluated by applying different quantitative approaches to the residuals from a cross validation test this modeling approach is a useful tool for interpolating local surface snow isotopic composition over antarctica both in terms of the low estimated errors and the possibility of understanding the processes that control stable isotopic composition in antarctic surface snow through the response curves of each independent variable we also presented and interpreted the resulting spatial variation patterns of 18 o d and deuterium excess to better use in many hydrological and paleoclimate applications

variability of el nino southern oscillation activity at millennial timescales during the holocene epoch the variability of el nino southern oscillation enso during the holocene epoch in particular on millennial timescales is poorly understood palaeoclimate studies have documented enso variability for selected intervals in the holocene but most records are either too short or insufficiently resolved to investigate variability on millennial scales1 2 3 here we present a record of sedimentation in laguna pallcacocha southern ecuador which is strongly influenced by enso variability and covers the past 12 000 years continuously we find that changes on a timescale of 2 8 years which we attribute to warm enso events become more frequent over the holocene until about 1 200 years ago and then decline towards the present periods of relatively high and low enso activity alternating at a timescale of about 2 000 years are superimposed on this long term trend we attribute the long term trend to orbitally induced changes in insolation and suggest internal enso dynamics as a possible cause of the millennial variability however the millennial oscillation will need to be confirmed in other enso proxy records

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

rapid eocene extension in the robinson district white pine county nevada constraints from 40ar 39ar dating precise 40ar 39ar ages on pretectonic syntectonic and posttectonic rhyolites from the robinson mining district which is within a highly extended domain in east central nevada indicate that extreme extension 400 occurred in fewer than 900 k y during the eocene the duration of extension is tightly delimited by an eocene lacustrine unit that was horizontal prior to extension and by younger rhyolitic units the rhyolites represent at least five eruptive episodes including the preextensional and synextensional rhyolite of white hill emplaced between 37 6 and 37 4 ma and the postextensional rhyolite of garnet hill emplaced at 36 7 ma although some of it is perhaps as old as 37 1 ma thus the duration of extreme extension at robinson was between 0 9 and 0 3 m y comparable to or shorter than other highly extended areas in western north america the extensional domain in east central nevada is a composite feature produced by localized episodic rapid extension that began in early eocene time and continued to at least middle miocene time

seasonal and spatial variations of 17oexcess and dexcess in antarctic precipitation insights from an intermediate complexity isotope model an intermediate complexity isotope model icm is used to investigate the sensitivity of water isotope ratios in precipitation including 17oexcess to climate variations in the southern hemisphere the icm is forced with boundary conditions from seasonal ncep doe ii reanalysis data perturbations to the surface temperature and humidity fields are used to investigate the isotopic sensitivity the response of 17oexcess to a uniform temperature change is insignificant over the ocean while there is a large magnitude response over the ice sheet particularly in east antarctica a decrease of ocean surface relative humidity produces increased 17oexcess and dexcess with a coherent response over both the ocean and antarctica for interior east antarctica the model simulates a seasonal cycle in 17oexcess that is positively correlated with 18o and of large magnitude 50 per meg consistent with the observations from vostok the seasonal cycle in 17oexcess for interior west antarctica is predicted to be considerably smaller in magnitude 12 per meg and is negatively correlated with 18o consistent with new data from a firn core near the west antarctic ice sheet divide site over the ocean the icm predicts much smaller seasonal cycles in 17oexcess oceanic source changes i e humidity are insufficient to explain the amplitude of the simulated seasonal cycle over the antarctic continent spatial differences in the seasonal response of 17oexcess to local temperature reflect the balance of equilibrium and kinetic fractionation during snow formation

regional climate regime classification as a qualitative tool for interpreting multi proxy palaeoclimate data spatial patterns a new zealand case study abstract the precipitation characteristics of three basic circulation types for new zealand weather kidson j w 2000 an analysis of new zealand synoptic types and their use in defining weather regimes international journal of climatology 20 299 316 are explored here as a palaeoclimate reconstruction tool and are utilised as a way to interpret spatial patterns exhibited by diverse multi proxy data assemblages the technique is founded on a modern climate shift analogue for new zealand where regional precipitation spatial changes accompanied the 1976 77 inter decadal pacific oscillation ipo phase change the analysis here indicates multi decadal scale circulation changes both in frequency and strength resulted from the 1976 77 ipo phase change primarily during mid late summer late autumn and late winter and a significant change a zonal regime frequency and strength increase occurred for august from the climatological results the eastern north island along with the western and eastern south island are crucial regions to include in a spatial pattern based palaeoclimate reconstruction because of sensitivities to zonal circulation changes ascribing a climate regime classification to multi proxy data was subsequently attempted for three discrete timeslices in the late holocene and illustrates that many different types of multi proxy terrestrial data can successfully be assimilated with some evident advantages and shortcomings climate regime classification has good potential for highlighting spatial and temporal gaps in regional palaeoclimate proxy networks and in the case of new zealand potential for connecting local and regional palaeoclimate data to conditions associated with westerly circulation changes the ipo and for exploration of australasian and extra tropical palaeoclimate archive connections

the snake range decollement an exhumed mid tertiary ductile brittle transition the snake range decollement srd in east central nevada separates supracrustal rocks extended by normal faulting from ductilely deformed igneous and metamorphic rocks a well known stratigraphy unaffected by earlier faulting permits analysis of both upper and lower plate strain leading to a better understanding of how vastly different rock types and deformational styles are juxtaposed along low angle faults in metamorphic core complexes middle cambrian to permian upper plate rocks are cut by two generations of ne trending east directed normal faults both generations were initiated as high angle 60 planar faults that flattened abruptly into the srd and rotated domino style to low angles yielding a total rotation of bedding of about 80 90 faulting is tertiary in age as 35 m y old volcanic rocks are involved and resulted in about 450 500 extension in a n55w s55e direction the srd developed as a subhorizontal surface 6 7 km deep at the top of the cambrian pioche shale lower plate granitic rocks and their late precambrian cambrian metamorphic country rocks were involved in progressive ductile to brittle extension at low greenschist grade forming a penetrative subhorizontal foliation and n55 70w lineation that increases in intensity eastward and upward toward the srd stretching and thinning in the lower plate is coaxial and comparable in magnitude to upper plate extension and is interpreted as synchronous k ar ages ranging from 20 to 40 m y in the lower plate suggests the n snake range represents a tertiary thermal anomaly we conclude that the srd developed as a ductile brittle transition zone at 6 7 km depth gravity data suggests that the gently domed srd is cut by younger basin and range faults but the geology of adjacent ranges suggests that the srd does not continue more than 60 km in any given direction the lack of stratigraphic omission across the srd rules out large amounts of movement on a surface that originally cut downsection and we suggest that extensional detachment faults such as the srd can be developed locally as boundaries between brittlely extended rocks and underlying ductile extension and intrusion

temperature and vapour trajectory controls on the stable isotope signal in canadian rocky mountain snowpacks the effects of temperature and seasonal air mass trajectories on stable water isotopes in alpine snowpacks are investigated using meteorological and snow pit data at two alpine field sites in the canadian rocky mountains haig glacier alberta and opabin glacier british columbia snow pits were sampled through three accumulation seasons october june 2004 05 2005 06 and 2006 07 for 18 o d temperature and density the isotopic characteristics of precipitation over these time periods including the local meteoric waterline and average 18 o d and deuterium excess were defined using this dataset individual snowfall events over the three seasons were identified in the accumulation records from both sites and then fit to snow pit stratigraphies to determine their mean isotopic characteristics a trajectory classification was produced for all events and the key meteorological characteristics of each trajectory class were investigated using data from alpine field sites and a suite of meteorological records from the region an analysis of the relative influences of temperature and air mass trajectory on snow isotope ratios reveals some separation in mean 18 o between storm classes however the separation appears to be driven primarily by the mean temperature of each class rather then being a direct effect of vapour pathway

frictional properties of natural fault gouge from a low angle normal fault panamint valley california 1 we investigate the relationship between frictional strength and clay mineralogy of natural fault gouge from a low angle normal fault in panamint valley california gouge samples were collected from the fault zone at five locations along a north south transect of the range bounding fault system spanning a variety of bedrock lithologies samples were powdered and sheared in the double direct shear configuration at room temperature and humidity the coefficient of friction was measured at a range of normal stresses from 5 to 150 mpa for all samples our results reinforce the intuitive understanding that natural fault gouge zones are inherently heterogeneous samples from a single location exhibit dramatic differences in behavior yet all three were collected within a meter of the fault core for most of the samples friction varies from 0 6 to 0 7 consistent with byerlee s law however samples with greater than 50 wt total clay content were much weaker 0 2 0 4 expandable clay content of the samples ranged from 10 to 40 wt frictional weakness did not correlate with expandable clays our results indicate that friction decreases with increasing total clay content rather than with the abundance of expandable clays the combination of field relations analytical results and friction measurements indicates a positive correlation between clay content fabric intensity and localization of strain in the fault core a mechanism based upon foliations enveloping angular elements to reduce friction is suggested for weakening of fault gouge composed of mixed clay and granular material we provide broad constraints of 1 5 km on the depth of gouge generation and the depth at which fault weakness initiates we show that slip on the panamint valley fault and similar low angle normal faults is mechanically feasible in the mid upper crust if the strength of the fault is limited by weak clay rich fault gouge

lacustrine evidence of holocene environmental change from three faroese lakes a multiproxy xrf and stable isotope study the vegetation history of the faroe islands has been investigated in numerous studies all broadly showing that the early holocene vegetation of the islands largely consisted of fellfield with gravely and rocky soils formed under a continental climate which shifted to an oceanic climate around 10 000 cal yr bp when grasses sedges and finally shrubs began to dominant the islands here we present data from three lake sediment cores and show a much more detailed history from geochemical and isotope data these data show that the faroe islands were deglaciated by the end of younger dryas 11 700 10 300 cal yr bp at this time relatively high sedimentation rates with high 13c imply poor soil development 13c ti and data reveal a much more stable and warm mid holocene until 7410 cal yr bp characterised by increasing vegetation cover and build up of organic soils towards the holocene thermal maximum around 7400 cal yr bp the final meltdown of the laurentide ice sheet around 7000 cal yr bp appears to have impacted both ocean and atmospheric circulation towards colder conditions on the faroe islands this is inferred by enhanced weathering and increased deposition of surplus sulphur sea spray and erosion in the highland lakes from about 7400 cal yr bp from 4190 cal yr bp further cooling is believed to have occurred as a consequence for increased soil erosion due to freeze thaw sequences related to oceanic and atmospheric variability this cooling trend appears to have advanced further from 3000 cal yr bp a short period around 1800 cal yr bp appears as a short warm and wet phase in between a general cooling characterised by significant soil erosion lasting until 725 cal yr bp interestingly increased soil erosion seems to have begun at 1360 cal yr bp thus significantly before the arrival of the first settlers on the faroe island around 1150 cal yr bp although additional erosion took place around 1200 cal yr bp possibly as a consequence of human activities hence it appears that if humans caused a change in the faroe landscape in terms of erosion they in fact accelerated a process that had already started soil erosion was a dominant landscape factor during the little ice age but climate related triggers can hardly be distinguished from human activities

eight glacial cycles from an antarctic ice core the antarctic vostok ice core provided compelling evidence of the nature of climate and of climate feedbacks over the past 420 000 years marine records suggest that the amplitude of climate variability was smaller before that time but such records are often poorly resolved moreover it is not possible to infer the abundance of greenhouse gases in the atmosphere from marine records here we report the recovery of a deep ice core from dome c antarctica that provides a climate record for the past 740 000 years for the four most recent glacial cycles the data agree well with the record from vostok the earlier period between 740 000 and 430 000 years ago was characterized by less pronounced warmth in interglacial periods in antarctica but a higher proportion of each cycle was spent in the warm mode the transition from glacial to interglacial conditions about 430 000 years ago termination v resembles the transition into the present interglacial period in terms of the magnitude of change in temperatures and greenhouse gases but there are significant differences in the patterns of change the interglacial stage following termination v was exceptionally long 28 000 years compared to for example the 12 000 years recorded so far in the present interglacial period given the similarities between this earlier warm period and today our results may imply that without human intervention a climate similar to the present one would extend well into the future

microsedimentological characterization using image analysis and μ xrf as indicators of sedimentary processes and climate changes during lateglacial at laguna potrok aike santa cruz argentina palaeoclimatic and paleoenvironmental high latitude records in the southern hemisphere are scarce compared to the northern counterpart however understanding global evolution of environmental systems during sudden climate changes is inseparable from an equivalent knowledge of both hemispheres in this context a high resolution study of lacustrine sediments from laguna potrok aike santa cruz province patagonia argentina was conducted for the lateglacial period using concurrent x ray fluorescence xrf and scanning electron microscope analyses peaks of ca si and mn and occurrences of the green alga phacotus lenticularis have been interpreted as variations in ventilation of the water column from 13 6 to 11 1 ka cal bp during this interval mild climate conditions during the younger dryas are characterized by relatively weak westerlies favouring the formation of a stratified water body as indicated by preserved manganese and ca si peaks and high total organic carbon toc values in this environment water in the epilimnion can reach sufficiently high temperature to allow p lenticularis to grow colder conditions are marked by peaks in ca without p lenticularis and occur during the antarctic cold reversal acr in this lateglacial interval micropumices were also detected in large amount image analysis of thin sections allowed the counting and size measurement of detrital particles and micropumices separately micropumices significantly influence the iron and titanium content hence preventing to use them as proxies of detrital input in this interval

itrax description and evaluation of a new multi function x ray core scanner a new automated multi function core scanning instrument named itrax has been developed that records optical radiographic and elemental variations from sediment half cores up to 1 8 m long at a resolution as fine as 200 m an intense micro x ray beam focused through a flat capillary waveguide is used to irradiate samples to enable both x radiography and x ray fluorescence xrf analysis data are acquired incrementally by advancing a split core via a programmable stepped motor drive through the flat rectangular section x ray beam traditional xrf determination of element composition in sediments provides high quality data but it takes a considerable time and normally consumes gram quantities of material that is often only available in limited quantities the itrax core scanner non destructively collects optical and x radiographic images and provides high resolution elemental profiles that are invaluable for guiding sample selection for further destructive detailed sampling this paper presents a description of the construction characteristics and capabilities of the itrax system high resolution itrax data obtained from sediment cores are also presented and compared with results from traditional wavelength dispersive xrf analysis at lower resolution finally some recent technical developments linked to the second generation itrax are presented

anisotropy pore fluid pressure and low angle normal faults low angle normal faults lanfs are commonly associated with high angle normal faults high pore fluid pressures and foliated fault cores explanations for lanf slip based on high pore fluid pressure critically depend on stress rotations in the fault core zone which have been based on an assumption of isotropy anisotropy fundamentally changes the coupling between pore fluid pressure and effective stress the response of saturated fault core rocks in lanfs can be explored by combining the effective medium theory with anisotropic poroelasticity the nucleation and evolution of lanfs are investigated in a framework of local changes in rock properties and the interaction of a pressurised pore fluid with intrinsic lithological and extrinsic damage anisotropies this quantitative approach enables comparison with detailed field and laboratory measurements of fault rock properties

characterizing the glaciological conditions at halvfarryggen ice dome dronning maud land antarctica we present a comprehensive approach including field data remote sensing and an anisotropic ice flow model to characterize halvfarryggen ice dome in coastal dronning maud land antarctica this is a potential drill site for the international partnerships in ice core sciences which has identified the need for ice cores covering atmospheric conditions during the last few millennia we derive the surface topography the ice stratigraphy from radar data and accumulation rates which vary from 400 to 1670 kg m 2 a 1 due to preferred wind directions and changing surface slope the stratigraphy shows anticlines and synclines beneath the divides we transfer dansgaard johnsen age depth scales from the flanks along isochrones to the divide in the upper 20 50 of the ice thickness and show that they compare well with the results of a full stokes anisotropic ice flow model which predicts 1 11 ka bp ice at 90 of the ice thickness 2 a temporally stable divide for at least 2700 4500 years 3 basal temperatures below the melting point 12 degrees c to 5 degrees c and 4 a highly developed crystal orientation fabric cof we suggest drilling into the apices of the deep anticlines providing a good compromise between record length and temporal resolution and also facilitating studies of the interplay of anisotropic cof and ice flow

modern and holocene aeolian dust variability from talos dome northern victoria land to the interior of the antarctic ice sheet abstract high elevation sites from the inner part of the east antarctic plateau sample windborne dust representative of large portions of the southern hemisphere and are sensitive to long range atmospheric transport conditions to polar areas on the periphery of the ice sheet conversely the aeolian transport of particles from high elevation ice free areas can locally represent a relatively important additional input of dust to the atmosphere and the interplay of atmospheric dynamics dust transport and deposition is strictly related to the regional atmospheric circulation behaviour both at present day and in the past the understanding of the spatial extent where local sources can influence the mineral dust budget on the ice sheet is fundamental for understanding the atmospheric dust cycle in antarctica and for the interpretation of the dust history in marginal glaciological settings in this work we investigate the spatial variability of dust flux and provenance during modern pre industrial and holocene times along a transect connecting talos dome to the internal sites of the antarctic plateau and we extend the existing documentation of the isotopic sr nd fingerprint of dust sized sediments from victoria land source areas dust flux grain size and isotopic composition show a marked variability between talos dome mid point d4 and dome c vostok suggesting that local sources play an important role on the periphery of the ice sheet microscope observations reveal that background mineral aerosol in the taldice core is composed by a mixture of dust volcanic particles and micrometric sized fragments of diatoms these latter representing a small but pervasive component of antarctic sediments a set of samples from victoria land mostly consisting of regolith and glacial deposits from high elevation areas was collected specially for this work and the isotopic composition of the dust sized fraction of samples was analyzed results reveal a close relationship with the parent lithologies but direct comparison between source samples and firn ice core dust is problematical because of the ubiquitous volcanic contribution to the environmental particulate input in the talos dome area the frequency of events potentially suitable for peripheral dust transport to talos dome appears relatively high for present day conditions according to back trajectories calculations and the related air flow pattern well defined from a seasonal and spatial perspective also as expected from palaeo data these events appear extremely uncommon for internal sites

the little ice age climate of new zealand reconstructed from southern alps cirque glaciers a synoptic type approach little ice age lia austral summer temperature anomalies were derived from palaeoequilibrium line altitudes at 22 cirque glacier sites across the southern alps of new zealand modern analog seasons with temperature anomalies akin to the lia reconstructions were selected and then applied in a sampling of high resolution gridded new zealand climate data and global reanalysis data to generate lia climate composites at local regional and hemispheric scales the composite anomaly patterns assist in improving our understanding of atmospheric circulation contributions to the lia climate state allow an interrogation of synoptic type frequency changes for the lia relative to present and provide a hemispheric context of the past conditions in new zealand an lia summer temperature anomaly of 0 56 c 0 29 c for the southern alps based on palaeo equilibrium lines compares well with local tree ring reconstructions of austral summer temperature reconstructed geopotential height at 1 000 hpa z1000 suggests enhanced southwesterly flow across new zealand occurred during the lia to generate the terrestrial temperature anomalies the mean atmospheric circulation pattern for summer resulted from a crucial reduction of the hse blocking synoptic type highs over and to the west of nz largely settled conditions and increases in both the t and sw trough synoptic types lows passing over nz enhanced southerly and southwesterly flow relative to normal associated land based temperature and precipitation anomalies suggest both colder and wetter than normal conditions were a pervasive component of the base climate state across new zealand during the lia as were colder than normal tasman sea surface temperatures proxy temperature and circulation evidence were used to corroborate the spatially heterogeneous southern hemisphere composite z1000 and sea surface temperature patterns generated in this study a comparison of the composites to climate mode archetypes suggests lia summer climate and atmospheric circulation over new zealand was driven by increased frequency of weak el nino modoki in the tropical pacific and negative southern annular mode activity

orbital and millennial antarctic climate variability over the past 800 000 years a high resolution deuterium profile is now available along the entire european project for ice coring in antarctica dome c ice core extending this climate record back to marine isotope stage 20 2 800 000 years ago experiments performed with an atmospheric general circulation model including water isotopes support its temperature interpretation we assessed the general correspondence between dansgaard oeschger events and their smoothed antarctic counterparts for this dome c record which reveals the presence of such features with similar amplitudes during previous glacial periods we suggest that the interplay between obliquity and precession accounts for the variable intensity of interglacial periods in ice core records

palaeocirculation across new zealand during the last glacial maximum at 21 ka abstract what circulation pattern drove southern alps glacial advances at 21 ka late 20th century glacial advances in new zealand are commonly attributed to a dual precipitation increase and cooler than normal temperatures associated with enhanced westerly flow that occur under synoptic pressure patterns termed zonal regimes kidson 2000 but was the circulation pattern that supported major southern alps glacial advances during the global lgm similar to the modern analog here a regional climate regime classification rcrc time slice was used to infer past circulation for new zealand during the lgm at 21 ka palaeoclimate information that supported the construction of the 21 ka time slice was derived from the nz intimate climate event stratigraphy ces one new auckland maar proxy record and additional low resolution data sourced from the literature the terrestrial evidence at 21 ka implicates several possibilities for past circulation depending on how interpretations for some proxies are made the interpretation considered most tenable for the lgm based on the agreement between terrestrial evidence marine reconstructions and palaeoclimate model results is an anticyclonic zonal circulation regime characterized by increased influences from blocking highs over the south island during winter and an increase in zonal and trough synoptic types with southerly to westerly quarter wind flow during summer these seasonal circulation traits would have generated lower mean annual temperatures cooler than normal summer temperatures and overall lower mean annual precipitation for new zealand particularly in the western south island at 21 ka the anticyclonic zonal time slice reconstruction presented in this study has different spatial traits than the late 20th century and the early little ice age signatures suggesting more than one type of regional circulation pattern can drive southern alps glacial activity this finding lends support to the hypothesis that temperature over precipitation change is more important as the primary modulator of southern alps ice advances the rcrc approach also demonstrates some subtle advantages of integrating multi proxy data within a palaeocirculation context for new zealand notably because this reconstruction technique enables direct comparisons to coarsely resolved palaeoclimate model outputs that do not have downscaled information

lake kinneret the sea of galilee the effects of diversion of external salinity sources and the probable chemical composition of the internal salinity sources this paper investigates the chemical variations and evolution of lake kinneret lk the sea of galilee after the diversion of onshore saline springs through the salinity diversion channel sdc which reduced the salinity of the lake water the mass balance approach enables to determine the average chemical composition of the unknown internal lake sources of salinity that in addition to other known sources contribute salts and control the chemistry of the lake water this study reveals for the first time the average chemical composition of the internal lake salinity sources mass balances show that the water discharge of the lake internal sources is 61 106 m3 year 1 and that these sources contribute 72 000 tons of chloride annually the sdc operation caused a long term decrease in the concentrations of cl mg na k ca so4 and br in lake water concomitantly the ionic ratios of na cl mg cl ca cl k cl and so4 cl have increased and br cl ratio has decreased the average chemical composition of the lake internal sources is characterized by na cl and mg cl ionic ratios which closely resemble those measured in the two well known submerged saline springs of fulyia a and fulyia b and in water of a deep observation well located north of the lake referred to as kin 8 the decrease in br cl ionic ratio from 3 58 10 3 prior to the sdc operation to 3 29 0 11 10 3 in mid 1990s implies that the major internal sources of cl and br to the lake are characterized by br cl ratios 3 29 10 3 br cl ionic ratios somewhat lower than 3 29 10 3 were found only in fulyia a and fulyia b springs and in kin 8 water it is therefore suggested that fulyia like water is the internal saline source which supplies most of the na cl and br to the lake sulphate however is contributed to the lake mainly over 80 through freshwater streams calcium and alkalinity originate mainly from freshwater sources including internal lake flow of groundwater lower in salinity but saturated with caco3 thus internal sources of solutes are mostly composed of the saline end member of fulyia like water and of fresher groundwater these conclusions have practical implications for lake water management

last glacial pollen climate reconstructions from northland new zealand despite wide ranging interest in the vegetation and climate of northland new zealand during the last glacial cycle the region and timeframe lack quantitative climate reconstructions while land based pollen records have tended to be poorly dated and fragmentary the region is also important for geochronology due to the co occurrence of the rotoehu tephra a widely dispersed isochron near the current limits of radiocarbon dating and extensive subfossil wood remains of agathis australis with strong dendrochronological and dendroclimatological potential we present new pollen records and temperature reconstructions from three sites set in coastal dune belts from western mid northland 35 s all containing rotoehu tephra that collectively span the last 70 ka the phases and amplitude of temperature changes broadly align with those reported from elsewhere in new zealand and with marine isotope climate stratigraphic records including maximum temperature depression of 6 8 c during the last glacial maximum we argue that these climatic patterns are intimately linked to shifts in the southern westerly wind belt the northern margins of which extend to the region today correspondence between the northland temperature shifts and atmospheric co2 supports the model of ocean atmosphere co2 flux modulated by latitudinal migration of the southern westerlies copyright 2017 john wiley sons ltd

cold conditions in antarctica during the little ice age implications for abrupt climate change mechanisms abstract the little ice age lia is one of the most prominent climate shifts in the past 5000 yrs it has been suggested that the lia might be the most recent of the dansgaard oeschger events which are better known as abrupt large scale climate oscillations during the last glacial period if the case then according to broecker 2000a 2000b antarctica should have warmed during the lia when the northern hemisphere was cold here we present new data from the ross sea antarctica that indicates surface temperatures were 2 c colder during the lia with colder sea surface temperatures in the southern ocean and or increased sea ice extent stronger katabatic winds and decreased snow accumulation whilst we find there was large spatial and temporal variability overall antarctica was cooler and stormier during the lia although temperatures have warmed since the termination of the lia atmospheric circulation strength has remained at the same elevated level we conclude that the lia was either caused by alternative forcings or that the sea saw mechanism operates differently during warm periods

pressure solution lithification as a mechanism for the stick slip behavior of faults many major faults including a large fraction of the san andreas appear to be virtually quiescent between great earthquakes the locked sections of the san andreas near san francisco and los angeles have little or no seismic activity on the primary fault trace although secondary faults may be active stick slip behavior on a fault can be explained in terms of a static coefficient of friction which is larger than the dynamic or sliding coefficient in this paper we propose a modification of the friction hypothesis in which chemical lithification cementation occurs on the fault between earthquakes as the stress on the fault increases it becomes large enough to break the cemented bonds between particles causing slip on the fault we treat this problem quantitatively assuming that pressure solution is responsible for the cementation an advantage of this model is that the hydrostatic pressure approaches the lithostatic pressure during cementation so that low fault strengths are predicted

turbidite emplacement on the southern balearic abyssal plain western mediterranean sea during marine isotope stages 1 3 an application of itrax xrf scanning of sediment cores to lithostratigraphic analysis the upper part 0 20 m of a long piston core from the se balearic abyssal plain spanning the past 50 ka has been studied using the itrax micro xrf core scanner to obtain downcore elemental profiles the ca fe ratio was found to be an effective parameter to distinguish between turbidites and pelagites because turbidites generally have higher fe contents and lower ca contents compared with pelagic intervals beds that were obscure when visually logged could be identified as turbidites or pelagites on their geochemical characteristics allowing more complete subdivision of the sequence into genetic units the itrax xrf data also provide useful information on textural grading bioturbative mixing identification of geochemically distinctive marker beds indications of differences in provenance and confirm or query the presence of early arrivals during turbidite emplacement a chronostratigraphic framework for the core based on accelerator mass spectrometry ams radiocarbon dating and correlation with oxygen isotope stages of pelagic intervals in other cores using calcium carbonate stratigraphy was also established this shows that turbidite emplacement on this part of the balearic abyssal plain has been modulated strongly by climate and sea level change with turbidite emplacement most frequent during the early holocene when the rate of post glacial sea level rise was greatest deposition of the coarsest i e sand and silt based turbidites at the core site was restricted to the full and late glacial 11 25 ka turbidite emplacement during oxygen isotope stage 3 was rare most of the turbidites at the site are distal but some coarse grained based turbidites are characterized by higher sr ca ratios possibly indicating a higher aragonite content higher ca and lower fe contents compared to other turbidites and are interpreted as having a more proximal shelf source such turbidites are generally rare however and restricted to full glacial and younger dryas time there is little evidence for large scale seismogenic turbidites expected to be seen as randomly timed emplacement seemingly independent of eustatic control at the core site despite proximity to the seismically active algerian margin 100 km to the south this suggests that seismogenic turbidites must largely bypass this part of the plain although the itrax core scanner provides a rapid and non destructive means of characterizing downcore geochemical distributions in great detail interpretation of the data requires caution and assessment from an informed standpoint analytical artefacts such as those caused by water or organic content degree of compaction grain size and mineral effects unevenness of the cut core surface and poor discrimination of closely spaced element xrf peaks need identification and elimination

the 1 5 ka varved record of lake montcortes southern pyrenees ne spain abstract the karstic lake montcortes sedimentary sequence spanning the last 1548 yr constitutes the first continuous high resolution multi proxy varved record in northern spain sediments consist of biogenic varves composed of calcite organic matter and detrital laminae and turbidite layers calcite layer thickness and internal sub layering indicate changes in water temperature and seasonality whereas the frequency of detrital layers reflects rainfall variability higher temperatures occurred in lake montcortes in ad 555 738 825 875 1010 1322 and 1874 present lower temperatures and prolonged winter conditions were recorded in ad 1446 1598 1663 1711 and 1759 1819 extreme and multiple precipitation events dominated in ad 571 593 848 922 987 1086 1168 1196 1217 1249 1444 1457 1728 1741 and 1840 1875 indicating complex hydrological variability in ne spain since ad 463 the sedimentary record of lake montcortes reveals a short term relation between rainfall variability and the detrital influx pronounced during extended periods of reduced anthropogenic influences in pre industrial times during warm climate episodes population and land use increased in the area after the onset of the industrialization the relationship between climate and human activities decoupled and population dynamics and landscape modifications were therefore mostly determined by socio economic factors

temporal and spatial variation of stable isotope ratios and accumulation rates in the hinterland of neumayer station east antarctica four firn cores were retrieved in 2007 at two ridges in the area of the ekstrom ice shelf dronning maud land coastal east antarctica in order to investigate the recent regional climate variability and the potential for future extraction of an intermediate depth core stable water isotope analysis tritium content and electrical conductivity were used to date the cores for the period 1981 2006 a strong and significant correlation between the stable isotope composition of firn cores in the hinterland and mean monthly air temperatures at neumayer station was r 0 54 0 71 no atmospheric warming or cooling trend is inferred from our stable isotope data for the period 1962 2006 the stable isotope record of the ice firn cores could expand well beyond the meteoro logical record of the region no significant temporal variation of accumulation rates was detected however decreasing accumulation rates were found from coast to hinterland as well as from east halvfarryggen to west sorasen the deuterium excess d exhibits similar differences higher d at sorasen lower d at halvfarryggen with a weak negative temporal trend on halvfarryggen 0 04 a 1 probably implying increasing oceanic input we conclude that halvfarryggen acts as a natural barrier for moisture carrying air masses circulating in the region from east to west

high resolution record of northern hemisphere climate extending into the last interglacial period high resolution record of northern hemisphere climate extending into the last interglacial period

prehistoric maritime migration in the pacific islands an hypothesis of enso forcing long distance human migration across the pacific ocean occurred during the late holocene and originated almost entirely in the west as prevailing tradewinds blow from the east the mechanisms of p

dust and sea salt variability in central east antarctica dome c over the last 45 kyrs and its implications for southern high latitude climate a detailed record of non sea salt calcium a proxy for dust and sea salt sodium a proxy for sea salt covering the last 45 kyr is presented it shows that in the first part of the transition from the last glacial period to the holocene 18 15 kyr bp the changes in dust flux mainly reflect changes at the dust source namely vegetation cover and local climate the changes in the later part of the transition 12 11 kyr bp are similar in extent to the changes seen in sea salt and most likely reflect a reorganization of the atmospheric circulation during the last glacial period considerable variation of dust but not of sea salt is observed pointing to climatic changes in patagonia the main dust source for dome c a comparison of the glacial records from dome c and taylor dome suggests that similar influences controlled aerosol input at both sites during this period

on the role of isostasy in the evolution of normal fault systems the footwalls of west dipping normal faults that separate the west central colorado plateau from the basin and range province record at least 5 7 km and perhaps as much as 15 20 km of west side up neogene uplift with an axis just 10 20 km west of undeformed plateau strata the uplift is expressed as folding and steep faulting in pre tertiary cratonic and disconformably overlying neogene strata forming a basement cored anticline and coincident topographic high on the western margin of the plateau the authors interpret the uplift as a nonelastic response of the crust to buoyancy forces accompanying the tectonic denudation of the plateau margin profound isostatically driven deformation of the footwalls of major normal faults may be common in extensional terrains calling into question several assumptions fundamental to existing models of the evolution of normal fault systems

seasonal variations of accumulation and the isotope record in ice cores a study with surface snow samples and firn cores from neumayer station antarctica at the german wintering base neumayer an intensive glacio meteorological program was carried out during the last two decades a complete meteorological data set and data from surface snow samples snow pits firn cores and weekly accumulation measurements from a stake array are available we first investigated the attenuation of the seasonal d18o signal due to water vapour diffusion in the snow pack a comparison of surface snow samples and firn cores of different age shows that only one third of the seasonal d18o signal of the surface snow samples remains in the cores after the first year no further significant change in the amplitude of the seasonal d18o signal is found later changes in the seasonal distribution of accumulation can lead to a bias in ice core properties this is studied on a short time scale using the available high time resolution data of accumulation stable isotope ratios and air temperature mean annual d18o values from firn cores are not well correlated to annual mean air temperatures however the correlation is improved considerably by weighting the annual mean air temperature by accumulation at neumayer mainly the cyclonic activity in late winter early spring determines whether and how the core data are biased

a multi proxy μ xrf inferred lake sediment record of environmental change spanning the last ca 2230 years from lake kanono northland new zealand abstract reliable interpretation of annual resolution climate proxies for wind precipitation and detrital influx are required for identifying the onset and periodicities of climatic events in particular this is essential for the evaluation of inter annual decadal and centennial trends driven by shifting positions of the southern westerly winds sww and subsequent storm belts associated with the southern annular mode sam and el nino southern oscillation enso here we present a quasi annual data set of xrf time series spanning ca 2230 years from lake sediment cores from lake kanono northland new zealand the xrf time series were interpreted using a combination of principal component analysis pca and cluster analysis then verified with comparison to regionally averaged empirical rainfall and wind climate station data our results show that the wavelet patterns align with the pca results allowing the xrf time series to be classified into group i detrital and group ii biological productivity and normalized climate proxies the normalized group ii xrf time series wavelet analyses displayed periodicities in the 2 16 year frequency likely associated with enso from ca 237 bce 1330 ce the data show clear evidence of both polynesian and european settlement phases in this part of northern new zealand and that polynesian settlement impact was coeval with changes in enso intensity and a phase shift in sam ca 1350 ce the medieval climate anomaly mca and the little ice age lia appear in the xrf time series data as separate clusters this data suggests that the mca is associated with windy dry conditions with intermittent storminess during the lia the 2 16 year periodicity associated with enso decreased and centennial to multi decadal length periodicities increase which may be an indication of an underlying sam signal within the data european settlement also had a direct impact on the lake basin via increased detrital influx likely from farming activities and intensification of local forestry operations

looking at fault reactivation matching structural geology and seismological data abstract we investigate fault reactivation that occurred during the 1997 colfiorito seismic sequence central italy matching detailed structural geology precise earthquake locations and mechanical models of fault interaction the colfiorito area within the northern apennines is characterised by a relatively recent inversion of the tectonic stress field from compression late miocene to extension late pliocene quaternary in september october 1997 the area experienced a protracted seismic sequence consisting of six moderate magnitude earthquakes 5 we analyse the coseismic elastic static stress changes due to the occurrence of the normal fault events in order to investigate the mechanical coupling and interaction between the nw se oriented normal fault system and the intervening n10 inherited fault we show that the elastic stress perturbation increased on the shallow portion of the activated volume where the n10 structure is located and promoted its reactivation with a strike slip motion the different amount of slip experienced along the two normal faults responsible for the greater mainshocks favoured the left lateral strike slip kinematics

interannual extremes in new zealand precipitation linked to modes of southern hemisphere climate variability abstract interannual extremes in new zealand rainfall and their modulation by modes of southern hemisphere climate variability are examined in observations and a coupled climate model north island extreme dry wet years are characterized by locally increased reduced sea level pressure slp cold warm sea surface temperature sst anomalies in the southern tasman sea and to the north of the island and coinciding reduced enhanced evaporation upstream of the mean southwesterly airflow during extreme dry wet years in south island precipitation an enhanced reduced meridional slp gradient occurs with circumpolar strengthened weakened subpolar westerlies and an easterly westerly anomaly in zonal wind in the subtropics as a result via ekman transport anomalously cold warm sst appears under the subpolar westerlies while anomalies of the opposite sign occur farther north the phase and magnitude of the resulting sst and evaporation anomalies cannot account for the rainfall extremes over t

analysis of tilting near normal faults using calculus of variations implications for upper crustal stress and rheology abstract an initially horizontal surface in the surroundings to a normal fault will after extension tilt towards the fault if in the hanging wall or away from it if in the footwall coseismic deformation of these surroundings can be validly modelled as flexure cumulative deformation on geological time scales has been regarded as flexure also but this has led to the apparent paradox that many observed structures require the effective elastic thickness of the brittle upper crust to be much smaller than its seismogenic thickness this article presents a possible alternative that cumulative deformation of the upper crust near some active normal faults may be regarded instead as partitioned into separation of the blocks that comprise their surroundings through the horizontal component of dip slip on the fault and distributed vertical simple shear in their surroundings which causes them to tilt and takes up the vertical slip on the fault a generalized profile of tilting near a normal fault which approximates a parabola can be derived following two assumptions first the brittle layer retains an elastic term in its rheology on geological time scales such that it resists arbitrary length changes second the brittle layer minimizes its overall vertical deflection thus minimizing the buoyancy force acting on it maximum stress and total strain energy associated with observed profiles of tilting are typically smaller for distributed vertical simple shear favouring this mechanism over flexure

centennial scale trends in the southern annular mode revealed by hemisphere wide fire and hydroclimatic trends over the past 2400 years millennial scale latitudinal shifts in the southern westerly winds sww drive changes in southern ocean upwelling leading to changes in atmospheric co2 levels thereby affecting the global climate and carbon cycle our aim here is to understand whether century scale shifts in the sww also drive changes in atmospheric co2 content we report new multiproxy lake sediment data from southwest tasmania australia that show centennial scale changes in vegetation and fire activity over the past 2400 yr we compare our results with existing data from southern south america and reveal synchronous and in phase centennial scale trends in vegetation and fire activity between southwest tasmania and southern south america over the past 2400 yr interannual to centennial scale rainfall anomalies and fire activity in both these regions are significantly correlated with shifts in the sww associated with the southern annular mode sam atmospheric variability of the southern hemisphere thus we interpret the centennial scale trends we have identified as reflecting century scale sam like shifts in the sww over the past 2400 yr we identify covariance between our inferred century scale shifts in the sww and antarctic ice core co2 values demonstrating that the sww co2 relationship operating at a millennial scale also operates at a centennial scale through the past 2400 yr our results indicate a possible westerly driven modulation of recent increases in global atmospheric co2 content that could potentially exacerbate current greenhouse gas related warming

snow precipitation at four ice core sites in east antarctica provenance seasonality and blocking factors snow precipitation is the primary mass input to the antarctic ice sheet and is one of the most direct climatic indicators with important implications for paleo climatic reconstruction from ice cores provenance of precipitation and the dynamic conditions that force these precipitation events at four deep ice core sites dome c law dome talos dome and taylor dome in east ant arctica were analysed with air mass back trajectories cal culated using the lagrangian model and the mean composite data for precipitation geopotential height and wind speed field data from the european centre for med ium range weather forecast from 1980 to 2001 on an annual basis back trajectories showed that the atlantic indian and ross pacific oceans were the main provenances of precipitation in wilkes land 80 and victoria land 40 respectively whereas the greatest influence of the ice sheet was on the interior near the vostok site 80 and in the southwest ross sea 50 an effect that decreased towards the coast and along the antarctic slope victoria land received snowfall atypically with respect to other antarctica areas in terms of pathway eastern instead of western seasonality summer instead of winter and velocity old air age geopotential height patterns at 500 hpa at low 10 days and high 2 6 days frequen cies during snowfall cycles at two core sites showed large positive anomalies at low frequencies developing in the tasman sea eastern indian ocean at higher latitudes 60 70s than normal this could be considered part of an atmospheric blocking event with transient eddies acting to decelerate westerlies in a split region area and accelerate the flow on the flanks of the low frequency positive anomalies

tropical east african climate change and its relation to global climate a record from lake tanganyika tropical east africa over the past 90 kyr abstract forcing mechanisms of tropical climate in continental areas remain poorly understood due in large part to a lack of continuous long term high fidelity records sediment core t97 52v from lake tanganyika provides new insight into the timing and mechanisms behind east african climate change over the past 90 kyr this record is particularly important because other than a recently recovered scientific drill core from lake malawi there are no other continuous well dated records from east africa prior to 60 ka the high resolution age model presented here provides a large degree of age certainty for the past 45 kyr and our suite of proxies allows a thorough examination of lake tanganyika s dynamics from core stratigraphy and chemical analyses we present evidence of a lake level drop greater than 400 m sometime prior to 90 ka much greater than that inferred for the lgm suggesting a period of intense aridity sometime around 100 ka additionally core t97 52 v preserves evidence of worm burrows detected by x radiographic imagery as indicated by burrow shaped deposits of iron oxide indicating a shallow lake at the time of deposition of that material intermittently high lake levels between 78 ka and 72 ka developed at the same time as a weakened asian monsoon and a pluvial phase in northeast brazil suggesting a global reorganization of climate possibly forced by a reduction in orbital eccentricity over the past 60 ka this core preserves the same events recorded in a core collected 100 km away in the southern basin of lake tanganyika including an unexplained increase in biogenic silica at 37 ka suggesting that this vast lake is responding coherently across both major bathymetric basins to regional and global climate forcing

balanced cross section construction from seismic sections in areas of extensional tectonics abstract the application of the technique of balanced section construction initially developed for areas of compressional folding and faulting is reviewed with reference to extensional tectonics a number of examples are discussed where these techniques have been successfully applied in the north sea the interpretation of geoseismic sections is considered to be greatly assisted by careful application of geometrical balance and a consideration of strain even in areas of low crustal extensions the nature of seismic sections however places limitations on the validity of balancing which must be borne in mind with such interpretations and wherever possible the balancing of a geoseismic section should be confirmed by complete depth conversion the rapid testing of the integrity of the geoseismic section by attempting to balance the section at the interpretational phase can eliminate many problems as well as allowing the fullest use to be made of the geophysical information

influence of the tropics on the southern annular mode abstractperturbations in the southern annular mode sam are shown to be significantly correlated with sst anomalies in the central tropical pacific during austral winter and sst anomalies in the eastern tropical pacific during austral summer the sam signature in the pacific sector resembles a tropically forced rossby wave train the so called pacific south american pattern while the signature in the indian ocean sector is a zonally elongated meridional dipole thus the sam contains strong zonally asymmetric variability and tends to behave differently in the eastern and western hemispheres with internal dynamics prevailing in the indian ocean sector and the forced response to tropical sst anomalies exerting a strong influence in the pacific sector the tropically forced component of the sam in the pacific sector is related to a geographically fixed active rossby wave source to the east of australia within the core of the subtropical jet in addition to the well documented positive trend in summer the

stable isotopes in surface snow along a traverse route from zhongshan station to dome a east antarctica samples of surface snow were collected for stable isotope analysis along the traverse route from zhongshan to dome a east antarctica from dec 28th 2007 to feb 8th 2008 the local relationship between d and surface temperature is established to be 6 4 0 2 per c very similar to the average for east antarctic the deuterium excess shows a pattern of high values over antarctica particularly at dome a we compare our data with an atmospheric general circulation model which includes stable water isotopes echam5 wiso the model simulation captures the right levels of d but overestimates 18o this study provides support for the ongoing deep ice core project at dome a

modeling the isotopic composition of antarctic snow using backward trajectories simulation of snow pit records 1 the quantitative interpretation of isotope records d 18 o dd and d excess in ice cores can benefit from a comparison of observed meteorology with associated isotope variability for this reason we studied four isotope records from snow pits in western dronning maud land dml antarctica covering the period 1998 2001 timing and magnitude of snowfall events on these locations were monitored using sonic height rangers for the distinguished snowfall events we evaluated the isotopic composition of the moisture during transport by combining backward trajectory calculations with isotopic modeling using a rayleigh type distillation model mcim the initial isotope ratio of the moisture was determined frommonthlymeanisotopefields fromageneralcirculation model echam4 the trajectory analysis showed that the southern atlantic ocean is the major moisture sourceforprecipitationindml modelingresultsalongthetrajectoriesrevealedthatmostof the isotopic depletion occurred during the last day of the transport finally a diffusion model was applied to describe the diffusion in the firn layer such that the modeled isotopes couldbecomparedwiththeobservedisotoperecords theresultingmodeledisotopeprofiles were mostly in good agreement with the observed seasonal variability in the snow however at low temperatures especially on the antarctic interior magnitude of the total distillation was underestimated regarding the d excess parameter our results show a large influence of advection height on the final value of d excess in precipitation this in turn points to the importance of the vertical structure of d excess over the oceanic source region which obscures the classical interpretation of this parameter in terms of temperature and relative humidity in the moisture source region

recent southern indian ocean climate variability inferred from a law dome ice core new insights for the interpretation of coastal antarctic isotopic records stable isotopes in water have been measured along a very high accumulation ice core from law dome on the east antarctic coast these enable a detailed comparison of the isotopic records over sixty years 1934 1992 with local antarctic station data and remote meteorological observations atmospheric reanalyses and sea surface temperature estimates on a seasonal to inter annual time scale using both observations and isotopic atmospheric general circulation model gcm results we quantify the relationships between stable isotopes 18o d and deuterium excess d d 8 18o with site and source temperature at seasonal and decadal time scales showing the large imprint of source conditions on law dome isotopes these calibrations provide new insights for the quantitative interpretation of temporal isotopic fluctuations from coastal antarctic ice cores an abrupt change in the local meridional atmospheric circulation is clearly identified from law dome deuterium excess during the 1970s and analysed using gcm simulations

a seasonal deuterium excess signal at law dome coastal eastern antarctica a southern ocean signature the snow isotopic composition 18o and d of two shallow cores from the high accumulation summit region of law dome east antarctica was measured at monthly resolution over the 1980 1992 period while the 18o or d signals clearly reflect the local temperature cycle the deuterium excess d d 8 18o is shifted with respect to 18o cycle by a 4 months lag interpretation of this phase lag is investigated using both an atmospheric general circulation model agcm which includes the water isotopic cycles and a simple isotopic model which better describes the microphysical processes within the cloud using this dual approach we show that the seasonality of 18o and d at law dome summit results from a combination of the southern ocean temperature cycle shifted by 2 3 months with respect to the local insolation and seasonal moisture origin changes due to a strong contribution of the local ocean when ice free both approaches are consistent with a dominant temperate to subtropical moisture origin we thus demonstrate from our present day subseasonal study that the record of d in the dome summit south dss deep ice core represents a potential tool for identifying changes in southern ocean temperatures and or sea ice cover at the scale of the past thousand years

thermochronological constraints on the timing and magnitude of miocene and pliocene extension in the central wassuk range western nevada apatite fission track and u th he thermochronological data provide new constraints on the timing of faulting and exhumation of the wassuk range western nevada where east dipping normal faults have accommodated large magnitude ene wsw oriented extension extensional deformation has resulted in the exhumation of structurally coherent fault blocks that expose sections of preextensional mostly granitic upper crust in the grey hills and central wassuk range these fault blocks display westward tilts of 60 and expose preextensional paleodepths of up to 8 5 km based on the structural reconstruction of tilted preextensional tertiary andesite flows that unconformably overlie mesozoic basement rocks apatite fission track and u th he thermochronological data from the fault blocks constrain the onset of rapid footwall exhumation at 15 ma fission track modeling results indicate rapid fault block exhumation occurred between 15 and 12 ma which is in agreement with miocene volcanic rocks that bracket the tilting history in addition fission track and u th he data suggest reduced rates of cooling following major extension as well as renewed cooling related to active high angle faulting along the present day range front starting at 4 ma thermochronological data from structurally restored fault blocks indicate a preextensional miocene geothermal gradient of 27 5 c km the thermochronological constraints on the timing of extensional faulting and the eruptive history in the wassuk range imply a model for extension where crustal heating and volcanism precede the onset of rapid large magnitude extension and where synextensional magmatism is suppressed during the highest rates of extension

abrupt millennial scale changes in intensity of southern hemisphere westerly winds during marine isotope stages 2 4 the strength of mid southern latitude westerly atmospheric circulation plays an important role in global climate due to a lack of long continuous high resolution paleoclimate archives from mid southern latitudes it remains unclear what factors control changes in its intensity and how past changes affected the climates of landmasses in their path here we show growth rate and stable isotope 18 o 13 c profiles from a south island new zealand stalagmite hw3 that permit centennial scale investigation of southern hemisphere westerly paleointensity between 73 and 11 ka correlation between hw3 growth rate and isotope profiles suggests sensitivity to changes in annual precipitation a factor controlled by westerly intensity low growth rates and relatively enriched isotope ratios define long term trends in hw3 supporting existing evidence that weaker westerlies predominated during the last glacial period abrupt millennial scale events occur frequently such that the hw3 record resembles greenland ice core stable isotope profiles furthermore nearly synchronous timing of nine prominent wet and cool intervals with heinrich events supports studies showing that increased westerly intensity is closely linked to north atlantic cooling as well as heinrich events the hw3 profiles also show an antarctic cold reversal like event during deglaciation advocating for a bipolar seesaw of global climate at that time

atmospheric influence on the deuterium excess signal in polar firn implications for ice core interpretation the seasonal deuterium excess signal of fresh snow samples from neumayer station coastal dronning maud land antarctica was studied to investigate the relationship between deuterium excess and precipitation origin an isotope model was combined with a trajectory model to determine the relative influence of different moisture sources on the mean annual course of the deuterium excess focusing on the phase lag between d 18 o and excess d whereas the annual course of d 18 o always shows an austral summer maximum which clearly depends on local temperature and the annual course of moisture source area parameters the deuterium excess of the fresh snow samples shows maximum values already in spring there can be many different reasons for the time lag between d 18 o and deuterium excess in an ice core including post depositional processes and changes in the moisture source of precipitation the use of fresh snow samples enabled us to exclude post depositional processes and study solely the influence of precipitation origin changes in the moisture source connected to systematic changes in the general atmospheric circulation can have a strong influence on the phase lag between deuterium excess and d 18 o which has to be taken into account for climatic interpretation of stable isotope profiles from ice cores

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

the effect of mineralogy and effective normal stress on frictional strength of sheet silicates abstract phyllosilicates are common constituents of upper crustal faults and subduction forearcs we studied the effect of mineralogy and controlled effective normal stress between 5 mpa and 100 mpa on frictional strength although the effect of mineralogy on frictional strength of single phase phyllosilicate gouges has been previously studied the influence of effective normal stress has not we conducted water saturated and vacuum dry frictional tests on single phase phyllosilicate gouges using a triaxial apparatus minerals included talc pyrophyllite kaolinite lizardite illite montmorillonite chlorite muscovite phlogopite and biotite particle size 20 mpa dry friction coefficients are constant and wet friction coefficients show a small increase this is attributed to loss of water and increased contact area the results indicate that frictional strength of clay rich faults increases at depths less than 1 km under hydrostatic pore fluid pressures

borehole versus isotope temperatures on greenland seasonality does matter new simulation results obtained with the hamburg atmosphere general circulation model echam 4 under maximum glacial boundary lgm conditions confirm the paleotemperatures on greenland determined by borehole thermometry the disagreement between 18o isotope based temperatures and the borehole temperatures of the lgm is not only reproduced by the model but the simulation results provide a plausible explanation paleotemperatures inferred from 18o measurements in ice cores are biased by a substantially increased seasonality of precipitation over greenland during the lgm during the glacial winter a much more zonal circulation prevents the effective transport of moisture to the greenland ice sheet and therefore reduces the contribution of isotopically strongly depleted winter snow to the annual mean isotope signal

style and age of late oligocene early miocene deformation in the southern stillwater range west central nevada paleomagnetism geochronology and field relations paleomagnetic and geochronologic data combined with geologic mapping tightly restrict the timing and character of a late oligocene to early miocene episode of large magnitude extension in the southern stillwater range and adjacent regions of west central nevada the southern stillwater range was the site of an oligocene to early miocene volcanic center comprising 1 28 3 to 24 3 ma intracaldera ash flow luffs lava flows and subjacent plutons associated with three calderas 2 24 8 to 20 7 ma postcaldera silicic dikes and domes and 3 unconformably overlying 15 3 to 13 ma dacite to basalt lava flows plugs and dikes the caldera related luffs lava flows and plutons were tilted 60 70 either west or east during the initial period of cenozoic deformation that accommodated over 100 extension directions of remanent magnetization obtained from these extrusive and intrusive caldera related rocks are strongly deflected from an expected miocene direction in senses appropriate for their tilt a mean direction for these rocks after tilt correction however suggests that they were also affected by a moderate 33 4 11 8 component of counterclockwise vertical axis rotation paleomagnetic data indicate that the episode of large tilting occurred during emplacement of 24 8 to 20 7 ma postcaldera dikes and domes in detail an apparent decrease in rotation with decreasing age of individual isotopically dated bodies of the postcaldera group indicates that most tilting occurred between 24 4 and 24 2 ma the onset of tilting immediately following after the final caldera eruptions suggests that the magmatism and deformation were linked deformation was not driven by magma buoyancy however because tilting equally affected the caldera systems of different ages including their plutonic roots it is more likely that regional extension was focused in the southern stillwater range due to magmatic warming and reduction of tensile strength of the brittle crust faults that accommodated deformation in the southern stillwater range initially dipped steeply and cut deeply to expose more than 9 km of crustal section the exposed crustal sections are probably rotated blocks above an unexposed basal detachment that lay near the early miocene brittle ductile transition

the deuterium excess records of epica dome c and dronning maud land ice cores east antarctica new high resolution deuterium excess d data from the two epica ice cores drilled in dronning maud land edml and dome c edc are presented here the main moisture sources for precipitation at edc and edml are located in the indian ocean and atlantic ocean respectively the more southward moisture origin for edml is reflected in a lower present day d value compared to edc the edml and edc isotopic records 18o and d show the main climate features common to the east antarctic plateau and similar millennial scale climate variability during the last glacial period however quite large 18o and d differences are observed during mis5 5 and the glacial inception with a long term behaviour a possibility for this long term difference could be related to uncertainties in past accumulation rate which are used in the glaciological models regional climate anomalies between the two sites during mis5 5 could also be consistent with the observed edml edc 18o and d gradient anomalies simulations performed with the general circulation model echam4 for different time slices provide a temporal temperature isotope slope for the edml region in fair agreement to the modern spatial slope tsite and tsource records are extracted from both ice cores using a modelling approach after corrections for past 18o seawater and elevation changes a limited impact of d on antarctic temperature reconstruction at both edml and edc has been found with a higher impact only at glacial inception the aim antarctic isotope maximum events in both ice cores are visible also after the source correction suggesting that these are real climate features of the glacial period the different shape of the aim events between edc and edml as well as some climate features in the early holocene points to a slightly different climate evolution at regional scale a comparison of our temperature reconstruction profiles with the aerosol fluxes show a strong coupling of the nssca fluxes with antarctic temperatures during glacial period and a tighter coupling of 18o and tsite with ssna flux at edml compared to edc during the glacial period and mis5 5

cenozoic extension and tilting recorded in upper cretaceous and tertiary rocks at the hall molybdenum deposit northern san antonio mountains nevada structural and paleomagnetic data from the 66 to 70 ma hall stock and its environs suggest that extension related tilting has continued in the northern san antonio mountains of nevada since at least 17 18 ma evidence includes both surface and subsurface mapping and paleomagnetic data the stock and its related molybdenum deposit most likely magnetized during a reversed polarity chron have been significantly tilted to the east as have nearby 16 to 29 ma volcanic rocks the data do not preclude the possibility of counterclockwise crustal rotations related to dextral motion of the san andreas and related faults similar horizontal tilt axes for the stock n30 w and the volcanic rocks n n20 w and similar tilt magnitudes among all units however suggest that much or all of the tilting in the district occurred between late oligocene and latest miocene time during west southwest east northeast pre basin range extension maximum pre oligocene post cretaceous tilt is clearly

limnological controls on stable isotope records of late holocene palaeoenvironment change in sw greenland a paired lake study stable isotope records are increasingly being used in palaeoenvironmental studies of arctic lakes here we compare stable isotope and elemental records 13c 15n c n with high resolution xrf derived geochemical and colour data from low arctic lakes ss1220 and ss85 in southwest greenland lake ss1220 sediments are laminated gyttja whereas ss85 consist of homogeneous gyttja both records cover the last c 5000 years 13c and carbon content suggest that organic matter in both lakes is predominantly autochthonous the c n variability ranging between 11 and 15 is interpreted to be a function of nitrogen deficiency which is further supported by 15n values at ss1220 falling close to atmospheric 15natmosphere although some changes in the geochemical stratigraphies presented here can be related to regional environmental change i e hydrology effective precipitation aeolian activity these effects are filtered through the lake catchments these changes alter the nutrient supply and hence lake productivity which appear to be the primary controls on the stable isotope data we suggest that information of past environmental change can only be gained from the stable isotope composition of lake sediments when there is a reasonable understanding of limnological processes and records may be lake specific

water isotopes as tools to document oceanic sources of precipitation the isotopic composition of precipitation in deuterium oxygen 18 and oxygen 17 depends on the climatic conditions prevailing in the oceanic regions where it originates mainly the sea surface temperature and the relative humidity of air this dependency applies to present day precipitation but also to past records which are extracted for example from polar ice cores in turn coisotopic measurements of deuterium and oxygen 18 offer the possibility to retrieve information about the oceanic origin of modern precipitation as well as about past changes in sea surface temperature and relative humidity of air this interpretation of isotopic measurements has largely relied on simple rayleigh type isotopic models and is complemented by lagrangian back trajectory analysis of moisture sources it is now complemented by isotopic general circulation models igcm in which the origin of precipitation can be tagged we shortly review published results documenting this link between the oceanic sources of precipitation and their isotopic composition we then present experiments performed with two different igcms the giss model ii and the lmdz model we focus our study on marine water vapor and its contribution to precipitation over antarctica and over the andean region of south america we show how igcm experiments allow us to relate climatic conditions prevailing in the oceanic source of precipitation to its isotopic composition such experiments support at least qualitatively the current interpretation of ice core isotopic data in terms of changes in sea surface temperature additionally we discuss recent studies clearly showing the added value of oxygen 17 measurements key points link between the isotopic content of precipitation and its oceanic origin application of this method to polar ice cores andean precipitation potential of combining deuterium excess and oxygen 17 excess 2013 american geophysical union all rights reserved

magnitude of isotope temperature scaling for interpretation of central antarctic ice cores 1 the conventional interpretation of ice core deuterium and oxygen 18 isotope profiles based on the use of present day observations spatial slope underestimates glacialinterglacial surface temperature changes in central greenland by up to a factor of two this likely results from changes in the seasonality of the precipitation due to the particular location of the greenland ice sheet next to the highly variable northern polar front in this regard the situation is much simpler for central antarctica and this should be reflected in the temperature interpretation of ice core isotopic records with this in mind we closely examine all relevant information focusing on the east antarctic plateau where both model and empirical isotope temperature estimates are available we point to the fact that correctly accounting for the influence of ocean isotopic change is important when interpreting deuterium profiles from ice cores in this region the evidence presently available indicates that unlike for greenland the present day spatial slope can probably be taken as a surrogate of the temporal slope to interpret glacial interglacial isotopic changes at sites such as vostok and epica dome c corresponding temperature changes are within 10 to 30 of those obtained from the conventional interpretation based on the use of the spatial slope index terms 1040 geochemistry isotopic composition chemistry 1827 hydrology glaciology 1863 3344 meteorology and atmospheric dynamics paleoclimatology 9310 information related to geographic region antarctica keywords water isotopes temperature estimate antarctica deuterium oxygen 18

seasonality of airmass pathways to coastal antarctica ramifications for interpreting high resolution ice core records abstractunderstanding airmass pathways is critical for ice core interpretation and the ability to determine the broadscale characteristics and seasonality of synoptic scale flow using paleoclimate records offers great potential to improve the understanding of past atmospheric circulation the dominant airmass pathways to a coastal antarctic ice core site at the whitehall glacier in the ross sea are modeled using snowfall and high resolution stable isotope data between 1979 and 2006 combined with back trajectories produced from both ncep ncar and ecmwf interim re analysis era interim data back trajectories generated from both datasets produce comparable results they show that high snowfall is associated with cyclonic airflow in the ross sea with a strong meridional component along the western ross sea coast over a 28 yr time frame trajectories also reveal a clear distinction between flow paths associated with above and below average annual temperatures high and low d in the ice core record in

have the southern westerlies changed in a zonally symmetric manner over the last 14 000 years a hemisphere wide take on a controversial problem the prevailing view in the palaeoclimate literature of the last 20 years is that the southern westerly winds sww were intensified over southern australia and tasmania during the warmer than present early holocene 11e8 ka at similar latitudes on the opposite side of the southern mid latitudes palaeoclimate studies have suggested a poleward shift of the northern edge of the westerlies and focusing at 49 s in southern south america this zonal asymmetry contrasts with the modern day zonal symmetry displayed by the sww and poses a formidable challenge to an understanding of the modes of climatic variability of the southern extra tropics this paper presents an updated synthesis of continuous radiocarbon dated palaeoenvironmental data from the westerlies zone of influence in all southern hemisphere continents synchronous multi millennial trends in moisture vegetation fire and hydrologic balance are remarkably consistent with the way the sww changes impact upon the climate in southern hemisphere landmasses in the modern climate considering the modern relationships between local precipitation and zonal wind speeds it is suggested that the sww changed in a zonally symmetric manner at multi millennial scale between 14 and 5 ka regional asymmetry develops after 5 ka across the southern hemisphere with a pattern of precipitation anomalies akin to the modern functioning of el nino e southern oscillation which started w6200 years ago

snow accumulation and its moisture origin over dome argus antarctica the spatial and temporal variability of snow accumulation near dome argus antarctica is assessed using new snow pit and stake measurement data together with existing snow pit ice core and automatic weather station records snow accumulation rate shows large inter annual variations but stable multi decadal levels over the last seven centuries spatial variations in snow accumulation within the space of 50 km of dome argus are relatively small probably thanks to the smooth topography a comparison of theses accumulation observations with ecmwf reanalyses era 40 and era interim suggests ecmwf reanalysis captures the seasonal variations but underestimates the overall snow accumulation at dome argus by 50 the moisture sources for precipitation over dome argus are examined by means of a lagrangian moisture source diagnostic based on the tracing of specific humidity changes along air parcel trajectories for the period 2000 2004 using operational ecmwf analysis data dome argus mainly receives moisture from the mid latitude 46 4 s south indian ocean with a seasonal latitudinal shift of about 6 compared to other central east antarctic deep ice core sites such as dome f dome c vostok and epica dronning maud land dome argus has a more southerly moisture origin probably due to topographic influences on the moisture transport paths these results have important implications for the interpretation of future ice cores at dome argus

seasonal precipitation timing and ice core records this is a commentary on global circulation model experiments of moisture source changes in greenland urging caution in how they are applied because they have important implications for paleoclimate reconstruction from ice cores the work comes from preliminary find is of a ice core gisp2 of the authors the authors conclude that at present anomalies in greenland ice core records should not be interpreted solely in terms of source region variations the combined use of oxygen 18 d and ionic species in the new summit greenland cores should make it possible to answer empirically some of the questions raised by the gcm experiments as to the interpretation of oxygen 18 records in terms of temperature 4 refs 1 fig

high resolution x ray fluorescence core scanning analysis of les echets france sedimentary sequence new insights from chemical proxies the les echets sediment sequence has recently been the subject of a high resolution multi proxy study which revealed shifts in lake productivity linked to greenland stadials and interstadials over the last 40 ka wohlfarth et al 2008 rapid ecosystem response to abrupt climate changes during the last glacial period in western europe 40 16 ka geology 36 407 410 here we present new elemental data for this sequence as acquired using an x ray fluorescence core scanning system which provides in situ high resolution continuous multi element analyses it was found that the strength of associations between the studied elements ti rb k zr si ca sr mn and fe varied over time with changes in lake status which are ultimately driven by changes in climate increases in fine grained detrital input as indicated by ti rb k and zr rb overlap with independently established periods of lower lake productivity and are interpreted to represent more arid conditions several of these arid periods are coincident with low diatom concentrations and the timing of heinrich events h4 h3 and h2 the duration of the environmental impacts linked to the h events varied by proxy with elemental data ti and zr rb estimating shorter events than the diatom data periods of lower detrital input and coarser grain sizes agreed in time with periods of higher lake productivity the elemental data provide new insights into hydrological changes and related sediment processes within the catchment and highlight the need for multi element and multi proxy approaches when reconstructing climate change using lacustrine sediment sequences copyright 2011 john wiley sons ltd

the epica ice core from dronning maud land first results from stable isotope measurements the european project for ice coring in antarctica epica focuses on the drilling of two deep ice cores the first at dome c and the second at kohnen station 75 00 s 0 04 e in dronning maud land dml this paper deals with stable isotope records from ice cores drilled in dml in the first season the deep epica dml core reached a depth of 450 m recovering ice approximately 7000 years old generally the d 18 o record indicates a stable holocene climate and shows low variability however during the last 4000 years based on a preliminary time scale the d 18 o values decrease continuously by about 0 6 and the deuterium excess values increase by about 0 5 t he correlation between d 18 o and the deuterium excess d is investigated for a 50 m long core section and the near surface snow high pass filtered profiles are positively correlated whereas the correlation between low pass filtered profiles is negative a post depositional effect due to diffusion processes can be seen in a sub annually resolved profile from snow pit samples changes in the seasonality of the evolution of the snow cover and the consequences for stable isotope content are demonstrated with data from ice core b31

synoptic variability in the ross sea region antarctica as seen from back trajectory modeling and ice core analysis 1 synoptic variability in the ross sea region antarctica over the last thirty years is investigated using back trajectory modeling and cluster analysis we identify two dominant air mass trajectory clusters oceanic west antarctic and continental east antarctic our analysis shows that the oceanic west antarctic trajectories have an annual cycle similar to the semiannual oscillation and on average peak in frequency during april while continental east antarctic trajectories reach their annual maximum during december we demonstrate a causal association between the el nino southern oscillation enso and the frequency of oceanic west antarctic trajectories originating from the ross sea and amundsen sea regions in contrast we find that the southern annular mode sam has little influence on the trajectory cluster frequencies we then develop proxy records for synoptic variability using a shallow firn core from gawn ice piedmont in southern victoria land continental east antarctic trajectory frequency correlates with concentrations of nitrate no3 which is sourced from stratospheric air masses descending over the antarctic interior at seasonal to inter annual scales the frequency of oceanic west antarctic trajectory clusters strongly correlate with deuterium excess which is sensitive to changes in relative humidity and sea surface temperature in the ross and amundsen seas inter annual variability in the frequency of oceanic west antarctic trajectories is discussed with respect to enso and changes in sst and sea ice extent

effects of seasonal variability of accumulation on yearly mean δ18o values in antarctic snow the annual mean oxygen isotope content of antarctic snow is strongly influenced by the seasonal variability ofaccumulation since the annual mean 18 o value is frequently used to derive mean annual temperatures from ice cores changes in atmospheric circulation pattern can lead to large errors in the deduced temperature record at the german antarctic wintering base neumayer accumulation measurements have been carried out continuously over the last 16 years weekly readings of accumulation stakes combined with snow pits and shallow firn cores are used to investigate the influence of the seasonal variability of accumulation on the annual mean 18 o values and to estimate the possible error in the determination ofannual mean temperatures from ice cores by using the oxygen isotope record

a new zealand perspective on centennial scale southern hemisphere westerly wind shifts during the last two millennia the strength and latitudinal position of the southern hemisphere westerly winds control regional climate and influence the global carbon cycle by physically regulating southern ocean co 2 exchange with the atmosphere however the mechanisms driving interannual to millennial variability of the westerlies remain poorly understood here we present an 1800 yr record of westerly wind variability recorded in new zealand fjord sediments located west of the southern alps fjord basins receive large amounts of westerly driven orographic precipitation 6 m yr 1 and strong winds lead to vigorous fjord mixing because of these links reconstructing precipitation and fjord circulation provides information on westerly wind behavior over southwest new zealand applying a multiproxy approach we find several intervals of inferred regional wind variability the intervals of 1450 1400 825 775 575 550 and 50 0 cal yr bp were anomalously wet while 325 300 and 250 225 cal yr bp were anomalously dry these interpreted intervals appear to be in phase with regional paleoclimate records two centennial scale wet intervals align with a multi centennial warm interval identified in the pages2k australasian temperature reconstruction while the drier intervals generally occur during cooler times the wet dry intervals presented here are matched by opposite wind and or precipitation trends reconstructed from the windfield core in chile and the southern windfield margin in antarctica such spatial patterns support the notion of centennial scale latitudinal wind shifts or contraction expansion of the core consistent with observations all sites show wind strengthening from 50 cal yr bp to present indicating an overall intensification of winds that is observed in modern instrumental and reanalysis data sets

origin of regional rooted low angle normal faults a mechanical model and its tectonic implications rooted listric low angle normal faults 20 of regional extent have been recognized widely in the past few years in the north american cordillera and elsewhere the low angle geometry of these crustal scale normal faults conflicts with anderson s 1942 classic theory of faulting in that theory the orientations of principal stresses are assumed to be vertical and horizontal the predicted dip angle of normal faults is about 60 rather than 20 or less recent geological and geophysical studies in the mid tertiary extensional terrane of southeastern california and western arizona suggest that thick mylonitic gneisses in the lower plates of low angle detachment faults may represent unidirectionally sheared laminar flow in and below the midcrust directed ductile flow possibly related to the gravitational spreading of thickened lower crust may induce a shearing traction on the horizontal or subhorizontal base of the brittle upper crust thus the orientations of the principal stresses can no longer be vertical and horizontal at this interface a simple elastic model incorporates the effect of basal shearing due to gravitational spreading on stress distributions in an elastic upper crust this model shows that parallel belts of compression and extension can be produced if a shearing traction acting on the base of the elastic upper crust is considered in particular appropriate stress conditions for the formation of regional low angle normal faults 20 can be produced by the superposition of two stress fields a basal shear stress field induced by the basal shear traction and a contractional stress field in which the horizontal deviatoric stress is compressional and the vertical gradient of the horizontal normal stress component is constant this superposed stress field may represent a tectonic setting where a stress field with compressional deviatoric stress induced by plate subduction or convergence is superposed on a basal shear stress field induced by gravitational spreading of thickened lower crust these results may explain both puzzling parallel belts of extension and compression and the occurrence of major low angle normal faults in some orogenic systems

synextensional magmatism leading to crustal flow in the albion raft river grouse creek metamorphic core complex northeastern basin and range 1 this study addresses the origin of granitic magmas in the albion raft river grouse creek arg metamorphic core complex and environs and how these inform us about the deep crustal processes leading to crustal flow and the formation of the arg shrimp rg u pb zircon ages whole rock geochemical data major and trace element data as well as sr and nd isotopes and zircon geochemistry in situ o isotope hf isotope and trace element compositions from eocene to oligocene magmas now exposed at three structural levels of the arg show that the 41 32 ma emigrant pass and the 32 25 ma cassia plutonic complexes have a common origin sharing a deep crustal hot zone that remained above solidus temperatures for at least 16 myr this magmatism is part of the protracted magmatism that swept southward across the western u s between 42 and 21 ma inferred to be the result of foundering of the shallow farallon slab isotopic modeling of geochemical data from these magmas suggests that between 41 and 32 ma the influx of mantle derived basalt into the lower crust triggered large scale hybrid magmatism generating calc alkaline magmas that erupted and intruded the upper crust and significantly weakened the lower and middle crust between 32 and 25 ma this hot zone incorporated large amounts of continental crustal melts resulting in greater mobility of the lower and middle crust driving middle crustal flow and the formation of granitic plutons that rose to shallower levels of the crust forming the granite cored gneiss domes of the arg

the origin of present day antarctic precipitation from surface snow deuterium excess data the deuterium excess d is defined as a linear combination of the d h and 18 o 16 o ratios in natural waters we present an interpretation of deuterium excess data in surface antarctic snow using an isotopic model to derive information on the origin of present day antarctic precipitation the data come from near the coast d47 adelie land and from inland south pole 1000 km from the sea the one dimensional isotopic model belongs to the rayleigh family but fully accounts for mixed cloud processes between 0 c and 30 c modeling d in polar snowfalls meets the problem of a large sensitivity to the saturation conditions prevailing at snow formation therefore we decided to tune the saturation in the model in order to yield realistic mean d values but we use the seasonal phase of d versus which is less sensitive to the saturation conditions as an independent validation of the model predictions both inland and near the coast our model can simulate the observed phase between d and in snow with moisture of subtropical origin 40 20 s although we do not treat specifically storm precipitation near the coast this study indicates that the observed phase between d and brings up a new validation of isotopic models it supports a distant vapor source for large scale precipitation delivered to the antarctic continent

implications for the interpretation of ice core isotope data from analysis of modelled antarctic precipitation by consideration of model generated atmospheric data dominant anomalies in the synoptic circulation patterns are observed under conditions of high ant arctic precipitation this is associated with strong moisture advection of marine origin examining precipitation at individual locations reveals a strong relationship between local surface temperature and precipitation amount days with 5 mm of precipitation which on average corresponds to about 8 of days over antarctica have surface tem peratures that are around 10 c warmer than the mean this bias suggest that abnormal conditions are captured in the ice core record and that interpretation or reconstruction of palaeotemperatur es will succeed only under the possibly flawed assumption that similar abnormal conditions existed at the time of deposition although isotopic analysis of ant arctic ice cores has been used successfully in palaeoclimate studies a complete under standing of the underlying processes affecting the deposition of the core remains to be found it is reasoned that by obtaining such an understanding it may be possible to recon struct the synoptic conditions under which accumulation occurred

trajectories in the antarctic lower troposphere the statistics of air mass transport to the neumayer antarctic station 8 22 w 70 7 s are derived from three dimensional 5 day backward trajectories on the basis of a numerical weather prediction model the global model of the german weather service for the period april 1993 to march 1996 trajectory errors are discussed in detail and errors of individual trajectories may sum up to from a few hundred to more than a thousand kilometers during 5 days traveling time despite the high quality of the global model and trajectory module described the most frequent easterly flow at neumayer consists of advection from oceanic and continental regions during southeasterly flow mean trajectories document oceanic air passing coastal continental regions during the 3 days preceding arrival air arriving from above the antarctic continent south of 75 s usually descends over the marginal plateau and especially over the slope region advection from the central plateau regions poleward of 80 s is rare marine trajectories from latitudes north of 60 s mostly start in 0 3 km height the modeled transport for the arrival levels at 950 hpa and 850 hpa at neumayer station document that the frequency of oceanic source regions increases with height trajectories for 15 other coastal destinations show that near surface easterly winds with a downslope component dominate along the eastern shore of the weddell sea the prevailing transport from the south at the filchner ronne ice shelf arises from deflected barrier winds along the transantarctic mountains at the northern tip of the peninsula westerly winds prevail and the air usually originates from the bellingshausen sea the probability of contact with air masses from ice free continents is small for all coastal sites