mass changes of the greenland and antarctic ice sheets and shelves and contributions to sea level rise 1992 2002 changes in ice mass are estimated from elevation changes derived from 10 5 years greenland and 9 years antarctica of satellite radar altimetry data from the european remote sensing satellites ers 1 and 2 for the first time the dh dt values are adjusted for changes in surface elevation resulting from temperature driven variations in the rate of firn compaction the greenland ice sheet is thinning at the margins 42 2g t a 1 below the equilibrium line altitude ela and growing inland 53 2g t a 1 above the ela with a small overall mass gain 11 3g t a 1 0 03 mm a 1 sle sea level equivalent the ice sheet in west antarctica wa is losing mass 47 4g t a 1 and the ice sheet in east antarctica ea shows a small mass gain 16 11 gt a 1 for a combined net change of 31 12 gt a 1 0 08 mm a 1 sle the contribution of the three ice sheets to sea level is 0 05 0 03 mm a 1 t he antarctic ice shelves show corresponding mass changes of 95 11 gt a 1 in wa and 142 10 gt a 1 in ea thinning at the margins of the greenland ice sheet and growth at higher elevations is an expected response to increasing temperatures and precipitation in a warming climate the marked thinnings in the pine island and thwaites glacier basins of wa and the totten glacier basin in ea are probably ice dynamic responses to long term climate change and perhaps past removal of their adjacent ice shelves the ice growth in the southern antarctic peninsula and parts of ea may be due to increasing precipitation during the last century

glaciological studies at siple station antarctica potential ice core paleoclimatic record the quality and utility of the records of oxygen isotopic abundances dust concentrations and anionic concentrations preserved in the ice at siple station 75 55 s 84 15 w are assessed from four shallow 20 m cores the combination of high accumulation 0 56 m a 1 w e and low mean annual temperature 24 c preserves the prominent seasonal variations in 18 which are very spatially coherent sulfate concentrations vary seasonally and in conjunction with 18 will allow accurate dating of deeper cores from siple station the concentrations of insoluble dust are the lowest measured in antarctica making siple station an excellent location to examine large increases in atmospheric tubidity the seasonal variations and annual fluxes of the anions are examined for the last two decades ad 1966 85 with regard to probable sources an unusually high sulfate flux in 1976 may reflect the february 1975 eruption of mount ngauruhoe new zealand no annual signal in nitrate concentration is confirmed and no unusually high nitrate fluxes support the suggestion of nitrate production by large solar flares however nitrate flux is higher for the latter half of the 1970s and early 1980s possibly reflecting the recent loss of stratospheric ozone finally comparison of the 18 o record with available surface temperature data ad 1957 85 reveals that multi year trends along the western coast of the antarctic peninsula are recorded at siple more importantly comparison with areally weighted temperature reconstructions suggests that the 18 record may reflect larger scale persistent trends in the high southern latitudes the strong spatial coherence of the preserved records the potential for accurate dating and possible relevance to larger scale processes make siple station an excellent site for paleoenvironmental reconstruction from ice cores

nine centuries of microparticle deposition at the south pole abstract the analysis of microparticles in a 101 m core from amundsen scott south pole station antarctica has revealed a substantial increase in total particle concentration between approximately 1450 and 1850 a d a period encompassing the latest neoglacial interval or little ice age it is likely that this reflects a simultaneous increase in the concentration of particulate material in the antarctic atmosphere this is important climatologically for the antarctic atmosphere may represent the closest approximation to the natural background aerosol thus cores from east antarctica may contain long and detailed records of the natural global background aerosol such records are unavailable from any other medium additionally a cyclical variation which appears to be annual has been detected in the south pole particle record these features allow construction of a relative time scale for ice cores older than 100 yr from regions of low accumulation 1 where many traditional techniques are not applicable this is especially significant as the comparison of climatic data extracted from ice cores with other records of proxy data depends upon the ability to assign an accurate time scale to the ice core an estimated nine century record of net annual accumulation at the south pole has been compiled and the calculated error in the time scale is 90 yr

is the antarctic ice sheet growing a common public perception is that global warming will accelerate the melting of polar ice sheets causing sea level to rise a common scientific position is that the volume of grounded antarctic ice is slowly growing and will damp future sea level rise at present studies supporting recent shrinkage or growth depend on limited measurements that are subject to high temporal and regional variability and it is too early to say how the antarctic ice sheet will behave in a warmer world

temperatures heating rates and vapour pressures in near surface snow at the south pole a finite volume model is used to simulate 9 years 1995 2003 of snow temperatures at the south pole the upper boundary condition is skin surface temperature derived from routine upwelling longwave radiation measurements while the lower boundary condition is set to the seasonal temperature gradient at 6 5 m depth taken from prior measurements at the south pole we focus on statistics of temperature heat fluxes heating rates and vapour pressures in the top metre of snow but present results from the full depth of the model 6 5 m the monthly mean net heat flux into the snow agrees with results from previous studies performed at the south pole on shorter timescales the heating rates and vapour pressures show large variability the net heat flux into the snow which is between 5wm 2 in the monthly mean can be greater than 20 w m 2 on hourly timescales on sub daily timescales heating rates exceed 40 k d 1 in the top 10 cm of the snow subsurface temperatures and therefore heating rates are more variable during winter april september due to increased synoptic activity and the presence of a strong surface based atmospheric temperature inversion the largest vapour pressures 60 70 pa and vertical gradients of vapour pressure are found in the top metre of snow during the short summer december january in contrast during the long winter the low temperatures result in very small vapour pressures and insignificant vapour pressure gradients the high summertime vapour pressure gradients may be important in altering the isotopic composition of snow and ice on the antarctic plateau

isotopic diffusion in cold snow and firn molecular mixing in cold snow and firn is ordinarily controlled by vapor diffusion diffusion through or along the ice matrix is slow whereas diffusion from the air to within separate grains is comparatively rapid thus mixing occurs in the vapor phase and exchange with the local ice involves all the water molecules a quantification of these concepts is applied to the diffusion of oxygen isotopic depth profiles in southern greenland and at dome c antarctica it successfully describes the smoothing of measured profiles the smoothing rate is strongly dependent on temperature and density of the firn

climate since ad 1510 on dyer plateau antarctic peninsula evidence for recent climate change a 480 year record of the oxygen isotope ratios dust content chemical species and net accumulation from ice cores drilled in 1989 90 on dyer plateau in the antarctic peninsula is presented the continuous analyses of small sub annual samples reveal well preserved annual variations in both sulfate content and 18o thus allowing an excellent time scale to be established this history reveals a recent pronounced warming in which the last two decades have been among the warmest in the last five centuries furthermore unlike in east antarctica on dyer plateau conditions appear to have been fairly normal from ad 1500 to 1850 with cooler conditions from 1850 to 1930 and a warming trend dominating since 1930 reconstructed annual layer thicknesses suggest an increase in net accumulation beginning early in the 19th century and continuing to the present this intuitive conflict between increasing net accumulation and depleted 18o cooler climate in the 19th century appears widespread in the peninsula region and challenges our understanding of the physical relationships among moisture sources air temperatures and snow accumulation the complex meteorological regime in the antarctic peninsula region complicates meaningful interpretation of proxy indicators and results in a strong imprint of local high frequency processes upon the larger scale climate picture

recent increase in south pole snow accumulation this paper summarizes the 37 year history of net accumulation measurements at the geographic south pole obtained by numerous investigators using a variety of techniques these data lead to the conclusion that annual net snow accumulation has increased in the vicinity of south pole station sps since 1955 the records were examined for evidence of a station effect and it is concluded that not all of the observed increase can be attributed to snow drift associated with the presence of the station furthermore the accumulation increase at the south pole appears consistent with increases observed at other locations on the east antarctic plateau and in the peninsula region as well these data suggest that the recent accumulation increase at sps may be regionally extensive over the east antarctic plateau

spatial and temporal variability of snow accumulation in east antarctica from traverse data recent snow accumulation rate is a key quantity for ice core and mass balance studies several accumulation measurement methods stake farm fin core snow radar profiling surface morphology remote sensing were used compared and integrated at eight sites along a transect from terra nova bay to dome c east antarctica to provide information about the spatial and temporal variability of snow accumulation thirty nine cores were dated by identifying tritium b marker levels 1965 66 and non sea salt nss so4 2 spikes of the tambora indonesia volcanic event 1816 in order to provide information on temporal variability cores were linked by snow radar and global positioning system surveys to provide detailed information on spatial variability in snow accumulation stake farm and ice core accumulation rates are observed to differ significantly but isochrones snow radar correlate well with ice core derived accumulation the accumulation ablation pattern from stake measurements suggests that the annual local noise metre scale in snow accumulation can approach 2 years of ablation and more than four times the average annual accumulation with no accumulation or ablation for a 5 year period in up to 40 of cases the spatial variability of snow accumulation at the kilometre scale is one order of magnitude higher than temporal variability at the multi decadal secular scale stake measurements and firn cores at dome c confirm an approximate 30 increase in accumulation over the last two centuries with respect to the average over the last 5000 years

late 20th century increase in south pole snow accumulation a compilation of the 37 year history of net accumulation at the south pole mosley thompson et al 1995 suggests an increase in net annual accumulation since 1965 this record is sporadic and its quality is compromised by spatially restricted observations and nonsystematic measurement procedures results from a new spatially extensive network of 236 accumulation poles document that the current 5 year 1992 1997 average annual net accumulation at the south pole is 84 5 8 9 mm water equivalent w e this accumulation rate reflects a 30 increase since the 1960s when the best although not optimal records indicate that it was 65 mm w e identification of two prominent beta radioactivity horizons 1954 1955 and 1964 1965 in six firn cores confirms an increase in accumulation since 1965 viewed from a longer perspective of accumulation provided by ice cores and a snow mine study the net accumulation of the 30 year period 1965 1994 is the highest 30 year average of this millennium limited data suggest this recent accumulation increase extends beyond the south pole region and may be characteristic of the high east antarctic plateau enhanced accumulation over the polar ice sheets has been identified as a potential early indicator of warmer sea surface temperatures and may offset a portion of the current rise in global sea level

retreating glacier fronts on the antarctic peninsula over the past half century the continued retreat of ice shelves on the antarctic peninsula has been widely attributed to recent atmospheric warming but there is little published work describing changes in glacier margin positions we present trends in 244 marine glacier fronts on the peninsula and associated islands over the past 61 years of these glaciers 87 have retreated and a clear boundary between mean advance and retreat has migrated progressively southward the pattern is broadly compatible with retreat driven by atmospheric warming but the rapidity of the migration suggests that this may not be the sole driver of glacier retreat in this region

the 1500m south pole ice core recovering a 40 ka environmental record supported by the us national science foundation a new 1500 m approximately 40 ka old ice core will be recovered from south pole during the 2014 15 and 2015 16 austral summer seasons using the new us intermediate depth drill the combination of low temperatures relatively high accumulation rates and low impurity concentrations at south pole will yield detailed records of ice chemistry and trace atmospheric gases the south pole ice core will provide a climate history record of a unique area of the east antarctic plateau that is partly influenced by weather systems that cross the west antarctic ice sheet the ice at south pole flows at approximately 10m a exp 1 and the south pole ice core site is a significant distance from an ice divide therefore ice recovered at depth originated progressively farther upstream of the coring site new ground penetrating radar collected over the drill site location shows no anthropogenic influence over the past approximately 50 years or upper 15 m depth age scale modeling results show consistent and plausible annual layer thicknesses and accumulation rate histories indicating that no significant stratigraphic disturbances exist in the upper 1500m near the ice core drill site

spatial and temporal variability in snow accumulation at the west antarctic ice sheet divide over recent centuries mean annual accumulation rates of 0 200 0 204 and 0 221 mweq a 1 respectively small scale spatial variability ssv was determined using an analysis of variance of accumulation in the ice core array thereby quantifying the uncertainty in individual accumulation records results indicate that the spatial variability was 0 030 mweq a 1 o r approximately 15 of the average annual accumulation an accumulation record representative of the wais divide local area over recent centuries was developed using a principal component analysis to identify the coherent accumulation signal the wais divide local record exhibited 14 interannual variability 1 standard deviation of the mean with the ssv reduced to 0 017 mweq a 1 correlations of the wais divide local accumulation record with atmospheric indices e g antarctic oscillation exhibited periods when the records oscillate in and out of phase thus reconstructing local and global atmospheric indices from wais divide accumulation records over recent centuries may prove problematic

an 860 km surface mass balance profile on the east antarctic plateau derived by gpr abstract snow accumulation and its variability on the east antarctic plateau are poorly understoodduetosparseandregionallycon nedmeasurements wepresenta5 3ghz c band ground penetratingradar gpr pro lewith atotal length of860kmrecovered duringthe jointnorwegian us internationalpolar year traverse 2007 08 mean surface mass balance smb over the last 200years was derived fromthe gpr data by identifying the volcanic deposition of the tambora eruption in 1815 it varies between9 1 and 37 7kgm 2 a 1 over the pro le with a mean of 23 7kgm 2 a 1 and a standard deviation of4 7kgm 2 a 1 the 200year smb estimated is signi cantly lower than most of the smb estimates overshorter time periods in this region this can be partly explained by a smb minimum in the vicinity ofthe ice divide however it is more likely that a recent increase in smb observed by several studies islargely responsible for the observed discrepancy introduction many recent studies have concentrated on the surface massbalance smb vaughan and others 1999 arthern andothers 2006 monaghan and others 2006 van de berg andothers 2006 and mass changes davis and others 2005 zwally and others 2005 of the antarctic ice sheet in orderto assess antarctica s contribution to changes in global sealevel new techniques such as radar altimetry have madeit possible to study continent wide elevation changes withhigh accuracy these changes are often related to changesin precipitation on the east antarctic plateau eap davisand others 2005 zwally and others 2005 however thesetechniques only cover short time periods it is important toobtain ground truth over longer time periods to understandhow observed changes relate to the past to date there have been very few in situ measurements ofsmb available from the interior of the eap the present smbestimates are mainly based on remote sensing e g arthernand others 2006 or numerical modelling e g monaghanand others 2006 van de berg and others 2006 calibratedby very sparse in situ measurements for the interior ofthe continent there are also indications that there are anon negligible number of zero accumulation sites so calledglazedareas intheinterioroftheeapthatareoftennottakeninto account by mass balance estimates and can changetheirvalue signi cantly frezzotti andothers 2002 scambosandothers 2008 it isclear that moreaccumulation dataarerequired to study the spatial and temporal variability of smband to improve the spatial resolution and accuracy of large scale accumulation studies the smb is the aggregate of many processes such asprecipitation from clouds and clear skies the formationof hoar frost at the surface and within the snowpack sublimation melting and runoff wind scouring and driftdeposition eisen and others 2008 snow accumulation canbe derived using various methods e g eisen and others 2008 snow pit rn and ice core studies provide valuableinformation about mean smb for a certain point location takahashi and others 1994 isaksson and others 1996 ansch utz and others in press these point measurementscan be spatially extended by ground penetrating radar gpr smb is proportional to the re ector depth withinthe rn pack as variations in vertical strain rates can beneglected in the top tens of metres of the ice sheet nye 1963 gpr has previously been successfully used to followisochronous rn layers providing detailed information aboutthe smb variability across antarctica fujita and others 1999 richardson naslund 2004 rotschky and others 2004 spikes and others 2004 arcone and others 2005a although large regions of the eap still remain uncovered we show smb derived by gpr data collected duringthe rst leg of the norwegian us scienti c traverse ofeastantarctica http traverse npolar no duringthe2007 08austral summer nus07 this joint project is part of thelarger trans antarctic scienti c traverses expeditions icedivideofeast antarctica taste idea andthe internationalpartnerships in ice coringsciences ipics goldman 2008

climate variability in west antarctica derived from annual accumulation rate records from itase firn ice cores thirteen annually resolved accumulation rate records covering the last 200 years from the pine island thwaites and ross drainage systems and the south pole are used to examine climate variability over west antarctica accumulation is controlled spatially by the topography of the ice sheet and temporally by changes in moisture transport and cyclonic activity a comparison of mean accumulation since 1970 at each site to the long term mean indicates an increase in accumulation for sites located in the western sector of the pine island thwaites drainage system accumulation is negatively associated with the southern oscillation index soi for sites near the ice divide and periods of sustained negative soi 1940 42 1991 95 correspond to above mean accumulation at most sites correlations of the accumulation rate records with sea level pressure slp and the soi suggest that accumulation near the ice divide and in the ross drainage system may be associated with the mid latitudes the post 1970 increase in accumulation coupled with strong slp accumulation rate correlations near the coast suggests recent intensification of cyclonic activity in the pine island thwaites drainage system

age vs depth of glacial ice at south pole knowledge of age as a function of depth in glacial ice is important for both glaciology and paleoclimatology for sites near a ridge or dome an ice flow model together with information on accumulation rate provides a first approximation if the accumulation rate is high enough annual layering of isotopes and dust measured in a solid core can provide a precise age vs depth relationship for south pole the flow geometry is not simple and no deep core exists nevertheless by remotely sensing peaks in scattering and absorption of light from pulsed sources buried at depths down to 2200 m we have been able to determine age vs depth for ages up to 65 000 years analysis of radar isochrons by siegert and hodgkins provides a rough extension of the age vs depth model to 165 000 years near bedrock

temperature profile for glacial ice at the south pole implications for life in a nearby subglacial lake airborne radar has detected 100 lakes under the antarctic ice cap the largest of which is lake vostok international planning is underway to search in lake vostok for microbial life that may have evolved in isolation from surface life for millions of years it is thought however that the lakes may be hydraulically interconnected if so unsterile drilling would contaminate not just one but many of them here we report measurements of temperature vs depth down to 2 345 m in ice at the south pole within 10 km from a subglacial lake seen by airborne radar profiling we infer a temperature at the 2 810 m deep base of the south pole ice and at the lake of 9 c which is 7 c below the pressure induced melting temperature of freshwater ice to produce the strong radar signal the frozen lake must consist of a mix of sediment and ice in a flat bed formed before permanent antarctic glaciation it may like siberian and antarctic permafrost be rich in microbial life because of its hydraulic isolation proximity to south pole station infrastructure and analog to a martian polar cap it is an ideal place to test a sterile drill before risking contamination of lake vostok from the semiempirical expression for strain rate vs shear stress we estimate shear vs depth and show that the icecube neutrino observatory will be able to map the three dimensional ice flow field within a larger volume 0 5 km3 and at lower temperatures 20 c to 35 c than has heretofore been possible

occurrence frequency of thickness of annual snow accumulation layers at south pole this paper describes the frequency analysis of 2000 annual snow accumulation layers at the south pole it proposes application of this analysis to objective extraction of meteorological parameters from the south pole snow accumulation record we have compared the 200 year snow mine accumulation record of giovinetto and schwerdtfeger and a 2000 layer pit and core record obtained in 1982 frequency analysis of the number of occurrences of layers with respect to thickness or mass of the layer showed the logarithms of thickness or mass to be normally distributed this lognormality is quite robust arbitrary partitioning of the data by depth or systematic partition of the data by densification or firn ice transition does not destroy the lognormality of the accumulation series the geometric standard deviation of the mass of annual layers was the same as the geometric standard deviation of the thickness of these same layers as the layers densified from firn to ice this agrees with kapteyn s theory of transformability of lognormal distributions we have also compared the snow accumulation and marine aerosol sodium accumulation in recent annual layers with the station meteorological record and the surface aerosol record the amounts of snow and sodium accumulated are proportional to the number of warmings salt storms in most years of this short record the accumulation record may be transformable to provide an index of this meridional transport we propose that the magnitude of snow accumulation with respect to frequency of that accumulation provides an objective criterion for comparing individual years of meteorological history and that the geometric standard deviation of accumulation provides an objective index for estimation of climatic fluctuation during the period of accumulation

model based constraints on interpreting 20th century trends in ice core 10be 1 beryllium 10 ice core records are useful for understanding solar magnetic field changes over time and in particular over the 20th century during which there are a variety of relevant observations however differences between 10be snow concentration records from different locations complicate the process of developing a coherent understanding of changes in cosmogenic isotope production we use the goddard institute for space studies modele general circulation model to simulate the production and transport of beryllium isotopes for this time period we compare our results with surface air observations and with ice core records from dye 3 taylor dome and south pole we find that unforced weather related internal variability causes modeled trends in 10be snow concentration to vary from the ensemble mean by 50 and greater at all three ice core locations lower levels of internal variability at taylor dome and south pole relative to dye 3 make the simulated 10be values at these locations better estimates of the ensemble mean trend in 10be snow concentration in addition the ensemble mean concentration trend at dye 3 was significantly different from the expected modeled trend based on applied production changes alone overall the results imply that during the 20th century 10be data from multiple cores are likely to be required to make meaningful inferences about 10be production changes the model simulations imply that data from antarctica are likely to be more robust

topographic control of regional accumulation rate variability at south pole and implications for ice core interpretation snow accumulation rates are known to be sensitive to local changes in ice sheet surface slope because of the effect of katabatic winds these topographic effects can be preserved in ice cores that are collected at non ice divide locations the trajectory of an ice core site at south pole is reconstructed using measurements of ice sheet motion to show that snow was probably deposited at places of different surface slope during the past 1000 years recent accumulation rates derived from shallow firn cores vary along this trajectory according to surface topography so that on a relatively steep flank mean annual accumulation is 18 smaller than on a nearby topographic depression these modern accumulation rates are used to reinterpret the cause of accumulation rate variability with time in the long ice core record as an ice dynamics effect and not a climate change signal the results highlight the importance of conducting ancillary ice dynamics measurements as part of ice coring programs so that topographic effects can be deconvolved from potential climate signals

geometry motion and mass balance of dyer plateau antarctica geodetic surveying and ground based radar profiling were used to determine geometry and surface motion of the ice sheet on the dyer plateau antarctica in the vicinity of an ice core site on a local dome vertical strain measurements in the core hole constrain the depth profile of vertical velocity these geophysical measurements are used to analyze the profiles of density and annual layer thickness measured on the ice core to estimate the current mass balance of the ice column and the past history of accumulation rate consideration of horizontal and vertical mass flow divergence shows that the profiles of density and vertical velocity are not fully consistent with steady state mean density of the firn layer appears to be increasing which leads to the deduction of a small rate of mass increase 0 02 m a 1 ice equivalent thickness over the last 200a there has been a gradual increase in accumulation rate from about 0 46 m a 1 to 0 54 m a 1 ice equivalent thickness in recent time

random fluctuations of snow accumulation over antarctica and their relation to sea level change short term changes in the volume of ice sheets as analyzed by radar altimetry may not be related to long term climatic change indeed the large relaxation time of an ice sheet induces a low frequency response to random fluctuations of snow accumulation however the time scale of the response is big compared to the average human lifetime and the effect of these random fluctuations on sea level change may be important even if they are not linked to climatic change in this study the relaxation time of an ice sheet is expressed with respect to the ice thickness surface slope and ice velocity these parameters are deduced from the precise topography derived from the geodetic cycle of the ers1 radar altimeter the variance of the induced effect on ice elevation is found to be around 3 m over a 30 year scale and with a maximum of 10 m in wilkes land and in the western part of the west antarctic ice sheet near the coast this effect can mask a climatic signal and thus be critical for altimetric mass balance surveys the estimated changes in antarctica s elevation between the seasat 1978 and ers 1993 epochs could be explained at least partially by such processes in terms of sea level change over the 30 year scale the standard deviation of the induced effect is 8 2 8 cm finally we show that the probability of a present day induced sea level rise of between 0 5 and 1 mm year over a 30 year time scale is estimated at 10 10 with coastal areas accounting for half of this signal

ground based measurements of spatial and temporal variability of snow accumulation in east antarctica the east antarctic ice sheet is the largest highest coldest driest and windiest ice sheet on earth understanding of the surface mass balance smb of antarctica is necessary to determine the present state of the ice sheet to make predictions of its potential contribution to sea level rise and to determine its past history for paleoclimatic reconstructions however smb values are poorly known because of logistic constraints in extreme polar environments and they represent one of the biggest challenges of antarctic science snow accumulation is the most important parameter for the smb of ice sheets smb varies on a number of scales from small scale features sastrugi to ice sheet scale smb patterns determined mainly by temperature elevation distance from the coast and wind driven processes in situ measurements of smb are performed at single points by stakes ultrasonic sounders snow pits and firn and ice cores and laterally by continuous measurements using ground penetrating radar smb for large regions can only be achieved practically by using remote sensing and or numerical climate modeling however these techniques rely on ground truthing to improve the resolution and accuracy the separation of spatial and temporal variations of smb in transient regimes is necessary for accurate interpretation of ice core records in this review we provide an overview of the various measurement techniques related difficulties and limitations of data interpretation describe spatial characteristics of east antarctic smb and issues related to the spatial and temporal representativity of measurements and provide recommendations on how to perform in situ measurements

a 150 000 year climatic record from antarctic ice during much of the quaternary the earth s climate has undergone drastic changes most notably successive glacial and interglacial episodes the past 150 kyr includes such a climatic cycle the last interglacial the last glacial and the present holocene interglacial a new climatic time series for this period has been obtained using 18 o data from an antarctic ice core

depth migration and interpretation of the cocorp wind river wyoming seismic reflection data to better understand laramide deformation deep seismic reflection data have been depth migrated focused or imaged in order to more clearly reveal structural features associated with the wind river thrust wyoming major structural features displayed in the migrated data are the wind river fault zone and the pacific creek anticline the wind river fault zone is seen to a depth of at least 25 km and interpretively to 32 km it is a complex zone that includes numerous splays flattening with depth the wind river range was tilted along these arcuate splays as it was compressionally thrust up the pacific creek anticline is asymmetric and thrust cored with the top of basement offset 600 m the pacific creek thrust is viewed as an embryonic wind river thrust

a century of accumulation and temperature changes in dronning maud land antarctica a mass balance program was initiated in the vestfjella heimefrontfjella area of western dronning maud land during the austral summer of 1988 1989 as a part of this program spatial and temporal variations in snow accumulation and temperature stable isotopes are measured using shallow firn cores in this paper we present surface accumulation data and discuss the climatic implications of the stable isotope records from two shallow firn cores one 30 m deep core obtained about 200 km from the coast at 700 m asl 73 36 s 12 26 w covers the period 1932 1991 the other core was drilled at about 500 km from the coast at 2900 m asl 75 00 s 2 00 e and covers the period 1865 1991 the recent accumulation increase that has been reported from several areas of the antarctic continent is not present in either of these records instead our coastal record suggests a significant decrease in accumulation with the strongest trend from about 1975 there is a positive trend in the oxygen isotope signal in both cores which in the coastal core corresponds to a temperature increase of about 1 8 c since the early 1930s and in the high altitude core to about 0 8 c since 1865 however it is likely that part of this increase in 18o is due to a change of moisture source