surface mass balance of small glaciers on james ross island north eastern antarctic peninsula during 2009 2015 two small glaciers on james ross island the north eastern antarctic peninsula experienced surface mass gain between 2009 and 2015 as revealed by field measurements a positive cumulative surface mass balance of 0 57 0 67 and 0 11 0 37 m w e was observed during the 2009 2015 period on whisky glacier and davies dome respectively the results indicate a change from surface mass loss that prevailed in the region during the first decade of the 21st century to predominantly positive surface mass balance after 2009 10 the spatial pattern of annual surface mass balance distribution implies snow redistribution by wind on both glaciers the mean equilibrium line altitudes for whisky glacier 311 16 m a s l and davies dome 393 18 m a s l are in accordance with the regional data indicating 200 300 m higher equilibrium line on james ross and vega islands compared with the south shetland islands the mean accumulation area ratio of 0 68 0 09 and 0 44 0 09 determined for whisky glacier and davies dome respectively is similar to the value reported for vega island and within the range of typical values for high latitude glaciers

sinemurian pliensbachian calcareous nannofossil biostratigraphy and organic carbon isotope stratigraphy in the paris basin calibration to the ammonite biozonation of nw europe abstract the biostratigraphy of sinemurian to lower toarcian calcareous nannofossils has been investigated in the sancerre couy core paris basin which contains a mixed assemblage of species with affinities to the northern and southern areas of the peri tethyan realm thus allowing for the use and calibration of the mediterranean province italy s france and nw europe uk biozonation schemes this study is based on semi quantitative analyses of the calcareous nannofossil assemblage performed on 145 samples and the recorded bioevents are calibrated to the nw european ammonite zonation and to a new organic carbon isotope curve based on 385 data points the main bioevents i e the first occurrences of parhabdolithus liasicus crepidolithus pliensbachensis crepidolithus crassus mitrolithus lenticularis similiscutum cruciulus sensu lato lotharingius hauffii crepidolithus cavus and lotharingius sigillatus as well as the last occurrence of parhabdolithus robustus have been identified however we show that a large number of standard biostratigraphic markers show inconsistent occurrences at the base and top of their range possibly accounting for some of the significant discrepancies observed between the different domains in addition to the nine main bioevents used for the biozonation of the core we document an additional 50 distinct bioevents evaluate their reliability and discuss their potential significance by comparison to previous studies a total of five significant negative organic carbon isotope excursions are identified and defined in the paris basin including the well documented sinemurian pliensbachian boundary event one positive excursion is further defined in the pliensbachian interval our calibration of high resolution calcareous nannofossil biostratigraphy to ammonite biostratigraphy and organic carbon isotopes represents a new stratigraphic reference for the lower jurassic series

calibration of early middle toarcian nannofossil events based on high resolution ammonite biostratigraphy in two expanded sections from the iberian range east spain abstract this work deals with refined nannofossil biostratigraphy in two well documented lower middle toarcian sections in the iberian range the sampled shallow carbonate ramp deposits belong to the turmiel fm and consist of an alternation of marls and limestones both lithologies yield common and well preserved ammonite assemblages which provide a refined ammonite biostratigraphic framework a significant calcareous nannofossil composition change has been recognized within the serpentinus zone and a useful succession of nannofossil events has been calibrated to the ammonite biostratigraphy this succession includes fo of lotharingius sigillatus mirabile subzone lo of mitrolithus jansae semicelatum subzone fo of carinolithus cantaluppii strangewaysi subzone los of biscutum grande and biscutum finchii lower part of the serpentinus zone fo of carinolithus superbus strangewaysi falciferum boundary fo of lotharingius velatus falciferum subzone fos of discorhabdus striatus and discorhabdus ignotus serpentinus bifrons boundary and acme end of lotharingius hauffii variabilis illustris boundary in the studied sections the composition changes the biohorizons recognized and their succession are closely comparable with other early middle toarcian boreal sections

the early toarcian anoxia a synchronous event in the western tethys an approach by quantitative biochronology unitary associations applied on calcareous nannofossils during the early toarcian major paleoenvironnemental and paleoceanographical changes occurred leading to an oceanic anoxic event oae and to a perturbation of the carbon isotope cycle although the standard biochronology of the lower jurassic is essentially based upon ammonites in recent years biostratigraphy based on calcareous nannofossils and dinoflagellate cysts is increasingly used to date jurassic rocks however the precise dating and correlation of the early toarcian oae and of the associated 13c anomaly in different settings of the western tethys are still partly problematic and it is still unclear whether these events are synchronous or not in order to allow more accurate correlations of the organic rich levels recorded in the lower toarcian oae this account proposes a new biozonation based on a quantitative biochronology approach the unitary associations ua applied to calcareous nannofossils this study represents the first attempt to apply theuamethod to jurassic nannofossils the study incorporates eighteen sections distributed across western tethys and ranging from the pliensbachian to aalenian comprising 1220 samples and 72 calcareous nannofossil taxa the biograph savary j guex j 1999 discrete biochronological scales and unitary associations description of the biograph computer program memoires de geologie de lausanne 34 282pp and ua graph copyright hammer o guex and savary 2002 softwares provide a discrete biochronological framework based upon multi taxa concurrent range zones in the different sections the optimized dataset generates nine uas using the co occurrences of 56 taxa these uas are grouped into six unitary association zones ua z which constitute a robust biostratigraphic synthesis of all the observed or deduced biostratigraphic relationships between the analysed taxa the ua zonation proposed here is compared to classic calcareous nannofossil biozonations which are commonly used for the southern and the northern sides of tethys the biostratigraphic resolution of the ua zones varies from one nannofossil subzone or part of it to several subzones and can be related to the pattern of calcareous nannoplankton originations and extinctions during the studied time interval the late pliensbachian early toarcian interval corresponding to the ua z ii represents a major step in the jurassic nannoplankton radiation the recognized ua zones are also compared to the carbon isotopic negative excursion and tocmaximum in five sections of central italy germany and england with the aim of providing a more reliable correlation tool for the early toarcian oae and of the associated isotopic anomaly between the southern and northern part of western tethys the results of this work show that the toc maximum and 13c negative excursion correspond to the upper part of the ua z ii i e ua 3 in the sections analysed this suggests that the early toarcian oae was a synchronous event within the western tethys

glacier wastage on southern adelaide island antarctica and its impact on snow runway operations the variations and dynamics of the southern edge of fuchs ice piedmont adelaide island 67845 09 s 68855 04 w antarctic peninsula are presented the snow covered surface of the glacier has been used since the 1960s for landing aeroplanes in support of british and more recently chilean operations at nearby teniente carvajal station formerly known as adelaide t in recent years snow conditions in the runway area have progressively deteriorated due to increasingly early summer melting radio echo sounding global positioning system and remotely sensed data have been analyzed for mapping the crevasse and ice velocity fields as well as the surface and subglacial topography of the area the results show that the runway area is located on a local ice divide surrounded by crevasses which are appearing on the glacier surface progressively earlier in the summer presumably due to higher snowmelt and perhaps higher ice velocities in response to regional atmospheric warming in the near future landing operations will be further affected as more crevasses will appear in the runway area if present warming trends persist this situation affects all coastal areas in the antarctic peninsula hence the need to search for possible new locations of crevasse free runways at higher elevations

rigorous 3d change determination in antarctic peninsula glaciers from stereo worldview 2 and archival aerial imagery abstract this paper presents detailed elevation and volume analysis of 16 individual glaciers grouped at four locations spread across the antarctic peninsula ap the study makes use of newly available worldview 2 satellite stereo imagery to exploit the previously untapped value of archival stereo aerial photography high resolution photogrammetric digital elevation models dems are derived to determine three dimensional glacier change over an unprecedented time span of six decades with an unparalleled mean areal coverage of 82 per glacier the use of an in house robust surface matching algorithm ensured rigorous alignment of the dems to overcome inherent problems associated with processing archival photography most notably the identification and correction of scale error in some datasets the analysis provides insight into one of the most challenging and data scarce areas on the planet by expanding the spatial extent north of the ap to include previously un studied glaciers located in the south shetland islands 81 of glaciers studied showed considerable loss of volume over the period of record the mean annual mass loss for all glaciers yielded 0 24 0 08 m w e per year with a maximum mass loss of up to 62 m w e and frontal retreat exceeding 2 2 km for stadium glacier located furthest north on elephant island observed volumetric loss was broadly though not always correlated with frontal retreat the combined mass balance of all 16 glaciers yielded 1 862 0 006 gt which corresponds to 0 005 mm sea level equivalent sle over the 57 year observation period

ice elevation changes of glaciar chico southern patagonia using aster dems aerial photographs and gps data hielo patagonico sur hps southern patagonia icefield is the largest temperate ice mass at mid latitudes in the southern hemisphere with few exceptions the glaciers in this region have been retreating during the last 50 years based on field data vertical aerial photographs and satellite images ice elevation changes since 1975 on glaciar chico one of the main tongues of hps are presented a maximum ice thinning of 5 4 0 55 m a 1 was observed at the glacier front between 1975 and 1997 global positioning system gps data were used in the accumulation area of the glacier to infer a thinning rate of 1 9 0 14 m a 1 between 1998 and 2001 this thinning rate is three times higher than the snow accumulation rate estimated for that part of the glacier a mean net glacier mass balance of 0 29 0 097 km 3 w e a 1 was estimated between 1975 and 2001 climate data suggest an increase in temperature and a reduction in precipitation during most of the 20th century in the vicinity of hps although these climate changes are the primary explanation for the observed ice elevation changes of the glacier ice dynamics effects are also believed to play an important role

uncertainty in well test and core permeability analysis a case study in fluvial channel reservoirs northern north sea norway reservoir permeability is one of the important parameters derived from well test analysis small scale permeability measurements in wells are commonly made using core plugs or more recently probe permeameter measurements upscaling of these measurements for comparisons with the permeability derived from drill stem tests dsts can be completed by statistical averaging methods dst permeability is commonly compared with one of the core plug averages arithmetic geometric or harmonic questions that commonly arise are which average does the dst derived permeability represent and over what region is this average valid another important question is how should the data sets be reconciled where there are discrepancies in practice the permeability derived from well tests is commonly assumed to be equivalent to the arithmetic in a layered reservoir or geometric in a randomly distributed permeability field average of the plug measures these averages are known to be members of a more general power average solution this pragmatic approach which may include an assumption on the near well geology is commonly flawed owing to several reasons that are expanded in this article the assessment of in situ reservoir permeability requires an understanding of both core plug and probe and well test measurements in terms of their volume scale of investigation measurement mechanism interpretation and integration this article presents a comparison of core and well test measurements in a north sea case study we undertook evaluation of three dsts and associated core plug and probe data sets from jurassic fluvial channel sandstones in a single field the well test permeabilities were generally found to differ from the core estimates begin page 1930 and no consistent explanation could be found for the group of wells however the probe permeameter data were able to further constrain the core estimates this study highlights the uncertainty in effective in situ reservoir permeability resulting from the interpretation of small core and reservoir well test scale permeability data the techniques used are traditional upscaling combined with the lorenz plot to identify the dominant flowing interval fluvial sandstones are very heterogeneous and this exercise is instructive in understanding the heterogeneity for the guidance of reservoir models in such a system

glacier inventory of james ross and vega islands antarctic peninsula this paper presents the results of the glacier inventory of james ross and vega islands based on topographic map sheets at 1 250 000 scale landsat multi spectral scanner imagery in bands 4 and 7 at the same scale and oblique air photographs obtained in 1979 80 work was completed following the method ology proposed by the temporary technical secretariat of the world glacier inventory this is the first such inventory carried out in antarctica

the early toarcian anoxic event in the westernmost tethys subbetic paleogeographic and paleobiogeographic significance a positive delta 13 c excursion reveals an oceanic anoxic event in the subbetic corresponding to the westernmost end of the tethys during the early jurassic this positive delta 13 c excursion exists in five stratigraphic sections consisting of lower and middle toarcian pelagic sediments the positive delta 13 c excursion in the subbetic is located in the upper part of the early toarcian serpentinus approx falciferum biozone while in other tethyan regions alps apennines and dinarides it has been found in the lower part of the same biozone the most significant positive delta 13 c excursion detected in the subbetic is therefore about half a million years younger although other relative peaks had been detected this isotopic anomaly can be correlated with a maximum transgression that occurred earlier in the regions closer to the open sea of the tethys ocean other features of the anoxic event faunal crises and black shale deposits appear at different ages related t

high latitude dust deposition in snow on the glaciers of james ross island antarctica high latitude dust hld depositions on four glaciers of james ross island the ulu peninsula were analysed the deposition rate on the selected glaciers varies from 11 8 to 64 0 g m 2 which is one order of magnitude higher compared to the glaciers in antarctica or elsewhere in the world a strong negative relationship between the sediment amount and altitude of a sampling site was found this is most likely caused by the higher availability of aeolian material in the atmospheric boundary layer general southerly and south westerly wind directions over the ulu peninsula with exceptions based on local terrain configuration help to explain the significantly lower level of sediment deposition on san jose glacier and the high level on triangular glacier x ray fluorescence xrf spectrophotometry was used to estimate the relative proportions of the main and trace lithophile elements in the sediment samples both the sediment amount and the xrf results are analysed in a depth profile at each locality and compared among the glaciers suggesting long range transport of fine mineral material from outside james ross island the distribution of aeolian sediment among the glaciers corresponds well with the prevailing wind direction on the ulu peninsula

probe permeametry applied to a highly laminated sandstone reservoir abstract approximately 5200 permeability measurements were made with an automated probe permeameter on 5 m of centre cut core from a north sea well the material studied is from the lower jurassic cook formation sandstone reservoir which here is heterogeneous in nature it consists of highly laminated sandstone shale interbedding with lamina or bed thickness ranging from a few tenths of a millimetre to upwards of 10 cm the aim of the study was to investigate the probe response in such material and to determine the permeability distribution at a smaller scale of investigation than that possible using core plugs fine grid measurements 1 mm sampling density supported by conventional plug measurements show that the three order of magnitude permeability variations measured are directly related to sedimentary features different facies can be defined each with an associated probe permeameter response and corresponding permeability range and combined with the measured distribution the fraction of each facies is calculated given a definite permeability range the amount of each facies as a fraction of the whole may be determined with an accuracy of 0 01 0 02

continental weathering and redox conditions during the early toarcian oceanic anoxic event in the northwestern tethys insight from the posidonia shale section in the swiss jura mountains abstract the geochemistry and mineralogy of organic rich sediments of the rietheim succession in northern switzerland were studied to evaluate the main impacts of the early toarcian oceanic anoxic event t oae 183 ma ago on the depositional environment in the nw tethys ocean the geochemical data obtained notably 13corg 13ccaco3 rock eval pyrolysis toccff support the hypothesis that the negative c isotope excursion at the onset of the t oae mainly reflects a major perturbation in the global carbon cycle rather than local environmental changes e g basinal restriction productivity rock eval pyrolysis and 13corg 15ntotal crossplots indicate that the organic matter was primarily of marine origin during the t oae and deposited in an epicontinental sea setting detrital proxies notably detritus index siliciclastic balance and ln al2o3 na2o suggest that the elevated pco2 levels and greenhouse climate prevailing during the t oae induced significant acceleration of the hydrologic cycle and an increase in continental chemical weathering rates redox sensitive proxies relative pyrite contents organic and sulfide balances v v ni ratios trace elements enrichment factors trace element toc co variation patterns and toc ptotal molar ratios indicate that the rietheim posidonia shale sediments accumulated under oxic to dysoxic bottom water conditions with more reducing conditions during the t oae anoxic and possibly euxinic these changes in redox conditions were probably induced by substantial thermohaline stratification driven by enhanced freshwater input and the recurrent influx of brackish arctic seawater into the nw tethys through the viking corridor in agreement with previous sedimentological and geochemical evidences from the nw tethys ocean in the studied succession such conditions were perhaps also responsible for sequestration of most of the regenerated p in the deeper water column by adsorption and or co precipitation into authigenic phases overall the major palaeoenvironmental changes documented in this study provide a robust example of earth s possible responses to the rapid onset of extreme greenhouse conditions

the toarcian in the subbetic basin southern spain bio events ammonite and calcareous nannofossils and carbon isotope stratigraphy abstract a detailed carbon isotope stratigraphic study for the uppermost pliensbachian lowermost aalenian interval in the median subbetic palaeogeographic domain external zones of the betic cordillera southern spain has been carried out during the early jurassic the median subbetic which represents a typical basin of the hispanic corridor connecting the tethys and the eastern pacific was located in the westernmost tethys the analyzed sections encompass the entire toarcian stage as represented in the southern iberian palaeomargin rocks are mainly rhythmic sequences of grey marls and marly limestones containing a rich ammonite fauna nannofossils and benthic foraminifers all these provide an accurate biostratigraphic control the lower and upper toarcian boundaries are well represented in some of these sections and therefore represent optimal sites to link the carbon isotope curves to ammonite zones and to nannofossil events 13 c values of bulk carbonates from the different localities of the subbetic basin have similar variations from the uppermost pliensbachian to the lowermost aalenian suggesting changes in the original dic carbon isotope composition along the hispanic corridor the transition from pliensbachian to toarcian is marked by increasing 13 c values from 1 2 to 2 0 interrupted in the serpentinum zone by a negative shift concomitant with the toarcian oceanic anoxic event t oae with the major ammonite extinction event of the toarcian and an important turnover of calcareous nannoplankton the negative shift observed in the serpentinum zone confirms the global perturbation of the carbon cycling documented along the tethys and the palaeo pacific in organic material and in marine carbonates however the amplitude of the negative excursion 1 5 is not compatible with an isotopic homogeneous seawater dic and or co 2 atmospheric reservoirs the interval from the middle to the top of the toarcian 13 c shows relatively constant values minor ammonite turnovers and is associated with increasing diversity of calcareous nannoplankton

multiproxy geochemical analysis of a panthalassic margin record of the early toarcian oceanic anoxic event toyora area japan abstract the early toarcian oceanic anoxic event oae was a significant palaeoenvironmental perturbation that led to marked changes in ocean chemistry and climate and which also had a long lasting impact on marine ecosystems the global significance of the event has been recognised from the widespread occurrence of a 3 7 negative excursion in the carbon isotope 13 c composition of marine organic and inorganic matter and terrestrial plant material this feature of the event is indicative of a pronounced perturbation to the global carbon cycle an inference further supported by widespread evidence for seawater deoxygenation and elevated rates of organic carbon burial nevertheless the precise palaeoenvironmental impacts of this event from sections outside of the boreal and tethyan realms are uncertain here we present the results of a multiproxy geochemical study of an expanded record of the early toarcian event from the northwest panthalassa ocean margin exposed in southwest japan toyora area yamaguchi prefecture our results indicate that in the studied succession organic matter enrichment persisted through the early toarcian event but elemental redox proxies do not support persistent seawater anoxia analyses of terrigenously derived major and trace element abundances coupled with sedimentological observations reveal an increase in coarse grained sediment close to the onset of a 4 excursion in 13 c org and coincident with an inferred increase in terrestrial organic matter flux these observations are consistent with previously published evidence for a marked strengthening of hydrological cycling and increased runoff that occurred contemporaneously with abrupt warming at the onset of the carbon isotope event

a reconciled estimate of glacier contributions to sea level rise 2003 to 2009 glaciers distinct from the greenland and antarctic ice sheets are losing large amounts of water to the world s oceans however estimates of their contribution to sea level rise disagree we provide a consensus estimate by standardizing existing and creating new mass budget estimates from satellite gravimetry and altimetry and from local glaciological records in many regions local measurements are more negative than satellite based estimates all regions lost mass during 2003 2009 with the largest losses from arctic canada alaska coastal greenland the southern andes and high mountain asia but there was little loss from glaciers in antarctica over this period the global mass budget was 259 28 gigatons per year equivalent to the combined loss from both ice sheets and accounting for 29 13 of the observed sea level rise

the impact of a changing southern hemisphere annular mode on antarctic peninsula summer temperatures since the mid 1960s rapid regional summer warming has occurred on the east coast of the northern antarctic peninsula with near surface temperatures increasing by more than 2 degrees c this warming has contributed significantly to the collapse of the northern sections of the larsen ice shelf coincident with this warming the summer southern hemisphere annular mode sam has exhibited a marked trend suggested by modeling studies to be predominantly a response to anthropogenic forcing resulting in increased westerlies across the northern peninsula observations and reanalysis data are utilized to demonstrate that the changing sam has played a key role in driving this local summer warming it is proposed that the stronger summer westerly winds reduce the blocking effect of the antarctic peninsula and lead to a higher frequency of air masses being advected eastward over the orographic barrier of the northern antarctic peninsula when this occurs a combination of a climatological temperature gradient across the barrier and the formation of a fohn wind on the lee side typically results in a summer near surface temperature sensitivity to the sam that is 3 times greater on the eastern side of the peninsula than on the west sam variability is also shown to play a less important role in determining summer temperatures at stations west of the barrier in the northern peninsula similar to 62 degrees s both at the surface and throughout the troposphere this is in contrast to a station farther south similar to 65 degrees s where the sam exerts little influence

marine record of holocene climate ocean and cryosphere interactions herbert sound james ross island antarctica abstract the sediment record offshore james ross island northeast antarctic peninsula presents an unparalleled opportunity to directly compare marine and terrestrial climate records spanning the holocene in maritime antarctica an 11 m drill core was collected between herbert sound and croft bay as part of the shaldril nbp 0502 initiative and produced the southernmost sediment record from the eastern side of the ap thirty eight radiocarbon ages are used to construct an age model of centennial scale resolution multi proxy records including magnetic susceptibility pebble content particle size total organic carbon and diatom assemblages were interrogated in the context of nearby holocene age ice core lake and drift records from james ross island differences in the timing and expression of holocene events reflect marine controls on tidewater glaciers such as water mass configurations and sea ice glacial behavior mimics ice core paleotemperatures during the holocene with the exception of distinct ocean warming events herbert sound was fully occupied by grounded ice during the last glacial maximum and experienced rapid lift off followed by a floating ice phase the canopy of floating ice receded by 10 2 4 cal kyr bp presumably in response to early holocene warming herbert sound and croft bay fully deglaciated by 7 2 cal kyr bp when the mid holocene hypsithermal commenced and the sound became open and productive an extreme peak in productivity 6 1 cal kyr bp indicates an oceanic warming event that is not reflected in atmospheric temperature or lacustrine sediment records increase in sea ice cover and ice rafting mark the onset of the neoglacial 2 5 cal kyr bp when pronounced atmospheric cooling is documented in the james ross island ice core our comparison facilitates more holistic understanding of atmosphere ocean cryosphere interactions that may aid predictions of glacial response to future warming and sea level scenarios

multi decadal glacier surface lowering in the antarctic peninsula from approximately 400 glaciers of the western antarctic peninsula no in situ records of mass balance exist and their recent contribution to sea level is consequently poorly constrained we seek to address this shortcoming by using surface elevations from usgs and bas airborne 1948 2005 and aster spaceborne 2001 2010 stereo imagery combined by using a rigorous semi automated registration approach to determine multi decadal glacier surface elevation changes in the western antarctic peninsula for 12 glaciers all observed glaciers show near frontal surface lowering and an annual mean lowering rate of 0 28 0 03 m yr at the lower portion of the glaciers during the 4 decades following the mid 1960s with higher rates for the glaciers in the north west parts of the antarctic peninsula increased lowering of up to 0 6 m yr can be observed since the 1990s in close correspondence to increased atmospheric positive degree days in all cases surface lowering reduces to zero within 5 km of the glacier front at around 400 m altitude this lowering may have been at least partially compensated for by increased high altitude accumulation

acceleration of snow melt in an antarctic peninsula ice core during the twentieth century over the past 50 years warming of the antarctic peninsula has been accompanied by accelerating glacier mass loss and the retreat and collapse of ice shelves a key driver of ice loss is summer melting however it is not usually possible to specifically reconstruct the summer conditions that are critical for determining ice melt in antarctic here we reconstruct changes in ice melt intensity and mean temperature on the northern antarctic peninsula since ad 1000 based on the identification of visible melt layers in the james ross island ice core and local mean annual temperature estimates from the deuterium content of the ice during the past millennium the coolest conditions and lowest melt occurred from about ad 1410 to 1460 when mean temperature was 1 6 c lower than that of 1981 2000 since the late 1400s there has been a nearly tenfold increase in melt intensity from 0 5 to 4 9 the warming has occurred in progressive phases since about ad 1460 but intensification of melt is nonlinear and has largely occurred since the mid twentieth century summer melting is now at a level that is unprecedented over the past 1 000 years we conclude that ice on the antarctic peninsula is now particularly susceptible to rapid increases in melting and loss in response to relatively small increases in mean temperature

decelerated mass loss of hurd and johnsons glaciers livingston island antarctic peninsula a new 10 year surface mass balance smb record of hurd and johnsons glaciers livingston island antarctica is presented and compared with earlier estimates on the basis of local and regional meteorological conditions and trends since johnsons is a tidewater glacier we also include a calving flux calculation to estimate its total mass balance the average annual smb over the 10 year observation period 2002 11 is 0 15 0 10 m w e for hurd glacier and 0 05 0 10 m w e for johnsons glacier adding the calving losses to the latter results in a total mass balance of 0 09 0 10 m w e there has been a deceleration of the mass losses of these glaciers from 1957 2000 to 2002 11 which have nearly halved for both glaciers we attribute this decrease in the mass losses to a combination of increased accumulation in the region and decreased melt the increased accumulation is attributed to larger precipitation associated with the recent deepening of the circumpolar pressure trough while the melt decrease is associated with lower summer surface temperatures during the past decade

dynamic thinning of glaciers on the southern antarctic peninsula growing evidence has demonstrated the importance of ice shelf buttressing on the inland grounded ice especially if it is resting on bedrock below sea level much of the southern antarctic peninsula satisfies this condition and also possesses a bed slope that deepens inland such ice sheet geometry is potentially unstable we use satellite altimetry and gravity observations to show that a major portion of the region has since 2009 destabilized ice mass loss of the marine terminating glaciers has rapidly accelerated from close to balance in the 2000s to a sustained rate of 56 8 gigatons per year constituting a major fraction of antarctica s contribution to rising sea level the widespread simultaneous nature of the acceleration in the absence of a persistent atmospheric forcing points to an oceanic driving mechanism

the timing of paleoenvironmental change and cause and effect relationships during the early jurassic mass extinction in europe the early jurassic marine mass extinction is one of several crises thought to coincide with anoxia transgression and warming caused by catastrophic release of gas hydrates however high resolution study of expanded sections in yorkshire england reveal that only the first of these factors is truly coincidental with extinction the well known transgression and large negative carbon isotope perturbation attributed to massive release of methane from gas hydrates occur after these events the anoxic event is developed diachronously in the european area with anoxia developing and fading away earlier in the mediterranean region compared with the nw european record however for a brief interval in the mid semicelatum subzone anoxia was simultaneously developed throughout the european region and it is this time that is marked by extinction of both benthic and pelagic marine fossils the sea level curve is also more complex than hitherto assumed with a minor regression occurring late in the semicelatum subzone shortly after the extinction the toarcian crisis occurred during a phase of global warming but the postulated release of methane from gas hydrates is too late to be implicated in the extinction mechanism as indeed is a recently reported cooling event from within the warming trend

precipitation sublimation and snow drift in the antarctic peninsula region from a regional atmospheric model 1 a regional atmospheric model with a horizontal grid spacing x of 14 km is used to study the surface mass balance components precipitation sublimation and snow drift in the region of the antarctic peninsula ap an integration is performed for the 7 year period 1987 1993 using a realistic forcing at the lateral model boundaries and at the sea surface output from this integration indicates that the precipitation reaches its maximum value on the northwestern slope of the ap where the upward motion in the atmosphere is largest uplift occurs upstream of the barrier affecting the precipitation distribution over sea the effect of the barrier on the precipitation distribution over the bellingshausen sea might have important implications for the ocean circulation in this region the mean precipitation over the grounded ice of the ap 1 20 m water eq yr 1 is 6 times larger than the mean value over all the grounded ice of antarctica our estimates for the surface sublimation and wind transport of snow over the grounding line toward the sea are 9 and 6 1 of the precipitation respectively in situ data of the wind distribution at three coastal sites located on the northern eastern and western sides of the ap are used to evaluate the modeled wind field which is important for the snow drift calculations for two of the three sites considered the prevailing wind direction and bimodal wind distribution are correctly represented by the model the calculated distribution of accumulation and ablation due to snow drift shows a complex pattern the wind removes snow from the spine of the ap where the near surface flow field diverges whereas deposition occurs mainly on the eastern slopes where the near surface flow field converges an intercomparison between two 7 year integrations at different horizontal resolution x 14 km and x 55 km shows that the precipitation on the northwestern slope is very sensitive to the model resolution in the x 14 km integration precipitation on the northwestern slope is higher than in x 55 km because of higher vertical velocities resulting in a 35 increase in average precipitation over the grounded ice of the ap

hurd peninsula glaciers livingston island antarctica as indicators of regional warming ice volume changes during the period 1956 2000 johnsons and hurd glaciers are the two main glacier units of hurd peninsula ice cap livingston island south shetland islands antarctica they presently cover an area of about 10 km 2 johnsons is a tidewater glacier while hurd glacier ends on emerged land in this paper we estimate the changes in ice volume during the period 1956 2000 and compare them with the regional meteorological records the volume change estimates are based on the comparison of digital terrain models for the glacier surface constructed from aerial photographs taken by the british antarctic survey in 1956 and from our geodetic measurements in 1999 2000 the total volume estimates are based on an ice thickness map constructed from radio echo sounding profiles 18 25 mhz done in 1999 2001 showing maximum ice thickness of about 200 m we estimate the changes in ice volume during the period 1956 2000 to be 0 108 0 048 km 3 which represents a 10 0 4 5 decrease from the 1956 total volume of 1 076 0 055 km 3 and is equivalent to an average annual mass balance of 0 23 0 10 m w e during 1956 2000 ice thickness changes range from 40 to 20 m averaging 5 5 4 4 m most areas show ice thinning the thickening is limited to a small area within johnsons glacier all glacier fronts except johnsons calving front show retreat these changes are consistent with the regional meteorological records for mean summer temperature which show a trend of 0 023 0 0058 ca 1 during the period 1956 2000

a new inventory of mountain glaciers and ice caps for the antarctic periphery although the glaciers in the antarctic periphery make up a large fraction of all mountain glaciers and ice caps on earth a detailed glacier inventory of the region is lacking we compile such an inventory recording areas area altitude distributions terminus characteristics and volume estimates glaciers on the mainland are excluded the inventory is derived from the antarctic digital database and some manual digitization we additionally rely on satellite imagery digital elevation models and a flowshed algorithm to classify ice bodies we find 1133 ice caps and 1619 mountain glaciers covering a total of 132 867 6643 km 2 estimated total volume corresponds to 0 121 0 010 m sea level equivalent of the total glacier area 99 drains either into ice shelves 63 or into the ocean 36 the inventory will provide a database for glacier mass balance assessments modelling and projections and help to reduce the uncertainties in previous studies

warming driven mass extinction in the early toarcian early jurassic of northern and central spain correlation with other time equivalent european sections abstract causes of the major mass extinction recorded during the early toarcian early jurassic are controversial many authors have concluded that the mass extinction is caused by the widespread oceanic anoxia derived from a postulated early toarcian oceanic anoxic event etoae supposedly synchronous in all basins and global in extent another group of papers links the mass extinction with a major climate change that occurred synchronously with the mass extinction the results of the study of five sections of the uppermost pliensbachian and lower middle toarcian deposits located in northern and central spain are presented detailed ammonite based biostratigraphy coupled with stable isotope analysis of belemnite calcite and bulk carbonates as well as total organic carbon toc analyses have been performed in all sections records of the vertical distribution of mainly benthic fossils have been compiled in four of the studied sections results obtained in the spanish outcrops have been compared and correlated with other european sections the excellent mutual relation between the patterns of the early toarcian progressive warming and the concomitant progressive losses of species evidences a cause and effect relationship between the increase of temperature and the mass extinction from an uppermost pliensbachian cooling interval warming started at the lower toarcian tenuicostatum zone increase of average seawater palaeotemperature is associated with a progressive and substantial drawdown in the number of species of nektonic planktonic and benthic organisms representing the extinction interval a prominent increase in seawater temperature occurred around the lower toarcian tenuicostatum serpentinum zonal boundary average temperatures at the serpentinum zone increased about 7 c marking the extinction boundary the high temperatures continued during the middle toarcian bifrons chronozone representing the repopulation interval the anoxia linked to the postulated etoae cannot be the responsible for the mass extinction because it has been synchronously recorded in the oxygenated environments of many european and northern african platforms deposition of laminated organic rich black shale facies above 5 wt toc indicating anoxic environments was mostly confined geographically to the western europe euxinic basin and mainly deposited after the extinction event during the interval of faunal recovery

western tethys early and middle jurassic calcareous nannofossil biostratigraphy an exhaustive biostratigraphic study based on the calcareous nannofossil content from lower and middle jurassic lusitanian basin sections in portugal is here presented located at the strategic intersection of important jurassic water masses during a period of drastic environmental changes the lusitanian basin conveyed mixed phytoplanktonic communities in its surface waters approximately 800 m of exceptionally continuous lower and middle jurassic series bearing detailed ammonite biostratigraphy and two global stratotype section and point are studied vertical and lateral ubiquity of calcareous nannofossils in marine sediments and rapid evolutionary rate and radiation make this fossil group a remarkable biostratigraphic tool nearly 100 bioevents are acknowledged in 24 myr time span this work refers to bridging 11 nannofossil zones and 29 subzones a thorough revision of the existing literature referring to early and middle jurassic calcareous nannofossil biostratigraphy is presented and causes and implications for zonal marker discrepancies discussed under a palaeoceanographic and jurassic nannofossil evolution angle in order to create a solid biostratigraphic frame and to compare it with c and o stable isotopic trends brachiopod calcite shells were analysed for geochemistry this work yields for the first time a very detailed and inclusive biostratigraphic scheme for the early and middle jurassic epochs

ice wastage on the kerguelen islands 49 s 69 e between 1963 and 2006 1 we observed the wastage of ice masses on the kerguelen islands indian ocean 49 s 69 e using historical information and recent satellite data overall the total ice covered area on the islands declined from 703 to 552 km2 between 1963 and 2001 a reduction of 21 the area of cook ice cap the main ice body decreased asymmetrically from 501 to 403 km2 west flowing glaciers lost 11 of their area while east flowing glaciers lost 28 after 1991 the retreat rate accelerated from 1 9 km2 a 1963 1991 to 3 8 km2 a 1991 2003 between 1963 and 2000 the ice volume loss was 25 30 km3 equivalent to an area average ice thinning rate of 1 4 1 7 m a the glacial retreat took place in the climatic context of a relatively low level of precipitation compared to the 1950s and a 1 c warming that occurred between 1964 and 1982 the acceleration of the ice losses since at least the 1990s indicates that the state of the ice bodies on the kerguelen islands is still far from balanced together with other studies in patagonia south georgia and heard island our analysis is consistent with a pattern of strong and accelerated wastage of ice masses influenced by the southern ocean

ice thickness areal and volumetric changes of davies dome and whisky glacier james ross island antarctic peninsula in 1979 2006 this study calculates area volume and elevation changes of two glaciers on james ross island antarctica during the period 1979 2006 davies dome is a small ice cap whisky glacier is a valley glacier ground penetrating radar surveys indicate ice thickness which was used for calculations of the bed topography and volume of both glaciers maximum measured ice thicknesses of davies dome and whisky glacier are 83 2 and 157 2 m respectively between 1979 and 2006 the area of the ice cap decreased from 6 23 0 05 km2 to 4 94 0 01 km2 20 7 while the area of the valley glacier reduced from 2 69 0 02 km 2 to 2 40 0 01 km2 10 6 over the same period the volume of the ice cap and valley glacier reduced from 0 23 0 03 km3 to 0 16 0 02 km3 30 4 and from 0 27 0 02 km3 to 0 24 0 01 km3 10 6 respectively the mean surface elevation decreased by 8 5 2 8 and 10 1 2 8 m the average areal 0 048 0 011 km2 a 1 and volumetric 0 003 0 001 km3 a 1 changes are higher than the majority of other estimates from antarctic peninsula glaciers

surface elevation changes on lachman crags ice caps north eastern antarctic peninsula since 1979 indicated by dems and icesat data the long term warming on the antarctic peninsula in the second half of the 20th century prompted rapid retreat of glaciers on the peninsula and surrounding islands retreat accelerated until the beginning of the new millennium when the regional warming trend significantly decreased the response of glaciers to the change in temperature trend has been observed around the northern part of the antarctic peninsula but the timing of the shift from the surface lowering to mass gain remains unclear using historical aerial photographs dems and satellite altimeter data from icesat we estimate areal and surface elevation changes of two small ice caps in the northern part of james ross island over the last 39 years the glacierized area on lachman crags decreased from 4 337 0 037 to 3 581 0 014 km2 17 4 between 1979 and 2006 and then increased to 3 597 0 047 km2 0 4 until 2016 surface lowering observed on ice caps after 1979 continued at least until 2008 as indicated by the icesat data the change from the lowering trend to increase in glacier surface elevation probably occurred after the ablation season 2008 09 which ranks among the warmest summers in the north eastern antarctic peninsula since the mid 20th century

probe permeametry an overview and bibliography applications of probe permeameters in both laboratory and outcrop studies of permeability heterogeneity are common we present an overview of the current status of probe permeameter data acquisition analysis and application the multidisciplinary nature of probe permeameter studies has led to their publication in diverse scientific journals we present a bibliography that includes literature covering both the technology and the application of probe permeametry

historically unprecedented global glacier decline in the early 21st century observations show that glaciers around the world are in retreat and losing mass internationally coordinated for over a century glacier monitoring activities provide an unprecedented dataset of glacier observations from ground air and space glacier studies generally select specific parts of these datasets to obtain optimal assessments of the mass balance data relating to the impact that glaciers exercise on global sea level fluctuations or on regional runoff in this study we provide an overview and analysis of the main observational datasets compiled by the world glacier monitoring service wgms the dataset on glacier front variations 42000 since 1600 delivers clear evidence that centennial glacier retreat is a global phenomenon intermittent readvance periods at regional and decadal scale are normally restricted to a subsample of glaciers and have not come close to achieving the maximum positions of the little ice age or holocene glaciological and geodetic observations 5200since 1850 show that the rates of early 21st century mass loss are without precedent on a global scale at least for the time period observed and probably also for recorded history as indicated also in reconstructions from written and illustrated documents this strong imbalance implies that glaciers in many regions will very likely suffer further ice loss even if climate remains stable

late cenozoic glacier volcano interaction on james ross island and adjacent areas antarctic peninsula region hambrey m j smellie john l nelson anna e johnson joanne s 2008 late cenozoic glacier volcano interaction on james ross island and adjacent areas geoantarctic peninsula region geological society of america bulletin 120 5 6 709 731