elevation changes of ice caps in the canadian arctic archipelago 1 precise repeat airborne laser surveys were conducted over the major ice caps in the canadian arctic archipelago in the spring of 1995 and 2000 in order to measure elevation changes in the region our measurements reveal thinning at lower elevations below 1600 m on most of the ice caps and glaciers but either very little change or thickening at higher elevations in the ice cap accumulation zones recent increases in precipitation in the area can account for the slight thickening where it was observed but not for the thinning at lower elevations for the northern ice caps on the queen elizabeth islands thinning was generally 0 5 m yr 1 which is consistent with what would be expected from the warm temperature anomalies in the region for the 5 year period between surveys and appears to be a continuation of a trend that began in the mid 1980s farther south however on the barnes and penny ice caps on baffin island this thinning was much more pronounced at over 1 m yr 1 in the lower elevations here temperature anomalies were very small and the thinning at low elevations far exceeds any associated enhanced ablation the observations on barnes and perhaps penny are consistent with the idea that the observed thinning is part of a much longer term deglaciation as has been previously suggested for barnes ice cap on the basis of the regional relationships between elevation and elevation change in our data the 1995 2000 mass balance for the archipelago is estimated to be 25 km3 yr 1 of ice which corresponds to a sea level increase of 0 064 mm yr 1 this places it among the more significant sources of eustatic sea level rise though not as substantial as the greenland ice sheet alaskan glaciers or the patagonian ice fields

the mid cretaceous earth paleogeography ocean circulation and temperature atmospheric circulation a reconstruction of the global paleogeography of the mid cretaceous 100 m y ago including adjustment of continental outlines to account for microplate movements cmstal shortening and accretion in mid cretaceous and later orogenic regions is described and a map presented on the modified continents coastlines and significant mountain ranges are added this paleogeography is used as a framework for a reconstruction of ocean surface circulation and temperature distribution then the main features of the atmospheric circulation are deduced using the paleogeography and ocean temperatures as boundary conditions relative to the present these features are a much weaker westerly wind belt and greater seasonality of wind patterns leading to more extreme surface climates over the continents slightly equatorward positions of the subtropical anticyclones and monsoonal regimes over the continental margins bordering tethys and the central atlantic a comparison of the results with climatic evidence from t

ocean circulation and calcareous nannoplankton evolution during the jurassic and cretaceous abstract spatial and temporal distribution of calcareous nannoplankton aid in the reconstruction of ocean circulation during the cretaceous biogeographic patterns of calcareous nannoplankton during the late cretaceous are mostly zonal reflecting mostly latitudinal gradients of surface water temperature during the middle cretaceous calcareous nannofossil assemblages are more strongly affected by surface water fertility concentration of limiting nutrients especially in a wide tropical belt between 50 and 45 n latitudes major upwelling regions off northwest africa in the south atlantic and the equatorial pacific divergence are apparent temporal changes in the composition of middle cretaceous nannofloras are indicative of changes in surface water fertility and vertical mixing at frequencies of tens to hundreds of kiloyears ka changes in the intensity of atmospheric circulation with frequencies close to the milankovitch cycles appear to be the ultimate cause of these minor changes in the circulation of the upper ocean calcareous nannofossil preservation patterns show that during the middle cretaceous deep waters were quite homogeneous with respect to carbonate saturation in the atlantic ocean but not in the indo pacific ocean where a more distinctive calcite compensation depth ccd is apparent water mass structure of the major oceans during the mesozoic was thus quite different taxonomic evolution of calcareous nannofossils was also strongly affected by ocean circulation and fertility major peaks in the rates of diversification coincide with anoxic events that is periods of increased preservation of organic carbon in the oceans which coincide with high sea level stands during anoxic events ocean circulation was sluggish vertical mixing was slow deep ocean ventilation poor and the concentration of limiting nutrients in surface waters was low increased competition for limiting nutrients and possibly preferential cropping of the dominant forms by zooplankton resulted in increased rates oof speciation during anoxic events periods of major production of nannofossil carbonate coincided with low sea level stands when oceans were more vigorously stirred and surface waters were more fertile the first such period was the latest jurassic when calcareous nannoplankton invaded the open oceans and became the major carbonate producers in the pelagic realm during the mesozoic the frequency of peaks and troughs in evolutionary rates is on the order of 10 30 ma and appears to be irregular the coincidence of periods of anoxia with high sea level stands which in turn appear to be caused by more rapid sea floor spreading indicates that the ultimate diving forces of nannoplankton evolution are processes in the earth s mantle these major tectonically driven fluctuations in ocean atmosphere circulation with frequencies of a few million to a few tens of millions of years are hereby named fischer cycles superimposed astronomically driven milankovitch cycles affected relative abundance patterns but not taxonomic evolution of calcareous nannoplankton rates of nannoplankton extinction are about five times higher than background rates at the end of the jurassic and orders of magnitude higher in the latest cretaceous possibly indicating a terrestrial or extraterrestrial catastrophe

cretaceous sedimentation in the outer eastern carpathians implications for the facies model reconstruction of the moldavide basin abstract the mid cretaceous is characterized by high eustatic sea levels with widespread oxic conditions that made possible the occurrence of globally correlated oceanic red beds however very often these eustatic signals have been overprinted by local tectonics which in turn resulted in lower cretaceous closed and anoxic basins as in the eastern carpathians there the black shale to red bed transition occurs in the latest albian up to the early cenomanian although earlier studies discussed the large scale basin configuration no detailed petrography and sedimentology study has been performed in the eastern carpathians this paper describes the hauterivian to turonian lithofacies and interprets the depositional settings based on their sedimentological features the studied sections crop out only in tectonic half windows of the eastern carpathians part of the vrancea nappe the lithofacies comprises black shales interbedded with siderites and sandstones calcarenites marls radiolarites and red shales the siliciclastic muddy lithofacies in general reflects accumulation by suspension settling of pelagites and hemipelagites in anoxic black shale to dysoxic dark gray and gray to green shales and oxic red shales conditions the radiolarites alternate with siliceous shales and are considered as evidence of climate changes the sandstones represent mostly low and high density turbidite currents in deep marine lobes as well as channel levee systems the source area is an eastern one e g the eastern carpathians foreland given the abundance of low grade metamorphic clasts the hauterivian lower albian sediments are interpreted as deep marine linear and multiple sourced mud dominated systems deposited in a mainly anoxic to dysoxic basin the anoxic conditions existed in the early to late albian but sedimentation changed to a higher energy mud sand dominated submarine channels and levees this coarsening upwards tendency is interpreted as the effect of the aptian to albian compressional tectonics of the carpathians the deepening of the moldavide basin from the cenomanian is most probably linked to a significant sea level rise

seasonal variation in boreal early cretaceous calcareous nannofossils the laminated munk marl bed of barremian early cretaceous age in the central trough of the north sea consists of alternating laminae of calcareous nannofossils 15 70 m thick and clay laminae 3 15 m thick comparison with laminated marls from the deeper parts of the modern black sea suggests that the nannoplankton laminae in the munk marl record annual variations in the nannofossils production the production rate of calcareous nannoplankton in the munk marl sea was comparable to that of modern seas the species composition was determined on 64 bedding planes distributed on three samples on the basis of sem photographs of bedding planes forty bedding planes comprising a total of 48 species were examined in the lowermost sample the species composition fluctuated strongly and 19 bedding planes were almost monopolized by a single species at least nine different species occasionally attained complete dominance succession of different floras within a single lamina was demonstrated in the uppermost sample watznaueria barnesae andmicrantholithus obtusus characteristically dominated in the lower and upper part of the laminae while the middle part was occupied by other species for exampleaxopodorhabdus dietzmannii andrhagodiscus asper a nannofossil lamina represents the annual nannoplankton production succession within a lamina is therefore the result of seasonal variation in the species composition the same succession could be repeated in several consecutive years but often a certain pattern was suddenly interrupted giving way to a complete different one

marsis remote sounding of localized density structures in the dayside martian ionosphere a study of controlling parameters enhanced topside electron densities in the dayside martian ionosphere have been repetitively observed in areas of near radial crustal magnetic fields for periods of tens of days indicating their long term spatial and temporal stability despite changing solar wind conditions we perform a statistical study of these density structures using the ionospheric mode of the mars advanced radar for subsurface and ionosphere sounding marsis onboard mars express we estimate the apparent extents of these structures relative to the altitude of the surrounding ionosphere the apex of the density structures often lies higher than the surrounding ionosphere median vertical extent of 18 km which indicates upwellings these structures are much wider than they are high with latitudinal scales of several degrees the radar reflector regions are observed above both moderate and strong magnetic anomalies and their precise locations and latitudinal extents match quite well with the locations and latitudinal extents of magnetic structures of given magnetic polarity oblique to vertical fields which happen to be regions where the field lines are open part of the time the majority of the density structures occur in regions where ionospheric plasma is dominant indicating closed field regions shielded from shocked solar wind plasma

nannofacies analysis as a tool to reconstruct paleoenvironmental changes during the early toarcian anoxic event the black shales of lower toarcian schistes carton in france jet rock in england posidonia shale in germany are sediments formed by fine alternations of millimetric to sub millimetric clear and dark laminae a study of polished core surfaces dotternhausen core sw germany was carried out in sem in order to characterize the micro fabrics of different laminae and their content in nannofossils two main intervals were recognized where fabrics and nannofossil content are significantly different in the clay rich interval characterized by high wt toc and a large negative carbon isotope excursion both in carbonates and organic matter the dominant micro fabrics are well foliated or lumpy giving evidence of the absence or reduction of benthic life nannofossils are scarce and only concentrated in discrete laminae separated by large abiotic intervals assemblages are indicative of a deep nutricline but sporadic nutrient inputs occurred as demonstrated by fluctuation in abundance of specimens of the biscutaceae nutrients were probably delivered to the german basin via riverine influx different sized framboids of pyrite were recognized in this interval the smallest ones 2 m being probably precipitated in an anoxic and sulphidic water column the clay rich interval was likely deposited during low sea level in a restricted basin these conditions were followed by a sea level rise and better water mass circulation within the german basin sedimentation records an increase in carbonate deposition organic matter content decreased and carbon isotopes came back to pre excursion values micro fabrics became less markedly laminated pyrite framboids nearly disappeared and rich and diversified nannofossil assemblages are recorded sea water conditions were probably highly fluctuating as indicated by alternation of intervals dominated in turn by schizosphaerella spp flourishing under generally oligotrophic conditions where nutrients were temporarily available in surface waters due to storms and by crepidolithus spp a deep dweller the results of this work fit well with a silled basin model

size variations and abundance patterns of calcareous nannofossils in mid barremian black shales of the boreal realm lower saxony basin abstract we present new quantitative calcareous nannofossil data from a barremian early cretaceous black shale interval of the boreal realm thirty samples from two sections in northern germany have been investigated the current study aims to understand the genesis of the barremian black shales so far only described from the boreal realm in a supraregional to global context by assessing the diversity patterns relative abundances and biometry of calcareous nannofossils from a distinctive late early barremian black shale horizon for morphometric size measurements three common taxa biscutum constans rhagodiscus asper and watznaueria barnesiae have been investigated the results show a decrease in size and abundance of the high fertility indicator b constans for the main black shale horizon hauptblatterton while abundances of the warm water species r asper and watznaueria spp increase deep dwelling nannoconids only flourished during black shale deposition this indicates warm oligotrophic surface waters and an expanded photic zone during the formation of the hauptblatterton black shales similar observations have been made for the oceanic anoxic event 1d oae 1d albian in the vocontian basin southern france and for the oae 2 cenomanian in the western interior seaway and southern england for w barnesiae our data confirm a high ecological tolerance and we assume a response in size if a certain limit is exceeded towards more extreme conditions nutrients therefore likely play a larger role than water temperature from our results it seems likely that nutrient availability controls both size and abundance patterns of b constans

size patterns of the coccolith watznaueria barnesiae in the lower cretaceous biotic versus abiotic forcing abstract body size is a major trait allowing the assessment of the respective control of evolution vs palaeo environment on unicellular micro organisms size patterns can be retraced for fossilisable micro organisms especially for coccolithophores over geological time spans here we present coccolith size patterns of watznaueria barnesiae which was a dominant and ubiquitous taxon in the mesozoic measurements were conducted at two sites spanning the upper berriasian to lower hauterivian namely the vergol la charce section in the epicontinental vocontian basin and the odp leg 185 hole 1149b located in the nadezhda basin in the pacific ocean the obtained results were treated using multivariate analysis in order to detect significant trends of the measured parameters size values of coccoliths from both sites are remarkably similar and display comparable patterns namely a statistically significant increase in the lower valanginian until maximum sizes recorded in the aftermath of the weissert event upper valanginian although w barnesiae coccolith size fluctuations in the short term might be related to environmental changes the observed long term size patterns are interpreted as the result of directional selection in which a single phenotype is favored through time comparison with data available in the literature shows a return to a smaller size after the turonian

middle cretaceous calcareous nannofossil biogeography and preservation in the atlantic and indian oceans implications for paleoceanography abstract the quantitative study of calcareous nannofossil preservation and biogeographic distribution puts constraints on paleoceanographic models for the atlantic and indian oceans during the middle cretaceous we establish a dissolution ranking of middle cretaceous calcareous nannofossils based on susceptibility to dissolution a positive correlation of organic carbon content of the sediments and the relative abundance of watznaueria indicates that much of the carbonate dissolution was caused by the release of carbon dioxide during oxidation of organic matter the depth distribution of the most dissolution resistant species watznaueria barnesae shows relative abundance maxima at the deepest sites and a maximum where intermediate waters impinge on slopes this reflects stagnant oxygen poor bottom waters and possibly a mid water oxygen minimum zone with increased deposition and catabolic breakdown of organic matter factor analyses are performed on various data sets for three different time slices ranging in age from late aptian to early albian middle albian and late albian to cenomanian the resulting factors can be related to paleoceanographic conditions such as colder water at high latitudes high fertility upwelling conditions and neritic conditions for all three time intervals a wide tropical to subtropical zone was flanked by boreal and austral zones upwelling conditions probably existed along the north african margin and over the falkland plateau zonal upwelling is tentatively postulated for the northwestern and northeastern margin of the north atlantic in the middle albian and for the eastern margin of the north atlantic off western europe for the late albian to cenomanian we speculate on surface water current patterns location of upwelling regions and haline driven deep circulation for the middle cretaceous

using airborne lidar and usgs dem data for assessing rock glaciers and glaciers abstract varying topographic and geologic conditions affect the location of rock glaciers despite being found worldwide rock glaciers are often confused with glacier counterparts or other periglacial landforms light detection and ranging lidar data because of its accuracy and resolution may help the assessment of topographic variables needed to form rock glaciers or help reveal unique characteristics to enhance regional automatic mapping the objectives of this paper are to compare the elevation slope aspect hillshade and curvature for 1 m lidar and 10 m us geological survey usgs digital elevation models dems from the andrews and taylor glaciers with the taylor rock glacier in colorado the utility of these data sources will be assessed for landform discrimination and to evaluate the uncertainty between the dems according to the lidar data the taylor rock glacier exists at a lower elevation and has a gentler slope compared to the glaciers each landform has steep areas from which snow and debris are delivered the andrews glacier has the most northern aspect which helps maintain it through snow accumulation and reduced insolation glaciers exhibit a concave mean curvature whereas the taylor rock glacier has a convex mean curvature the fine resolution of the lidar data clearly identifies some distinct characteristics on the taylor rock glacier ridges furrows and a pronounced front slope were easily identifiable on the lidar dem whereas crevasses the boundary between snow and debris covered surfaces and a lateral moraine were detectable near the andrews glacier the accuracy assessment revealed that at a common 10 m resolution the usgs dem estimated a maximum elevation about 150 m greater compared to the lidar data in areas of rugged topography surrounding the landforms a comparison of root mean squared errors rmse between the lidar and usgs dems showed that the taylor rock glacier has the lowest rmse for the elevation and the curvature variables as a result readily available usgs dems may better for analysis to characterize the topographic setting of landforms at the regional scale at the fine scale however the micro topography of rock glaciers is illuminated much more clearly on the lidar data making it an ideal yet costly source for feature extraction

on improving the accuracy of electron density profiles obtained at high altitudes by the ionospheric sounder on the mars express spacecraft we attempt to improve the standard inversion routine used to obtain electron density profiles from the data measured by the mars advanced radar for subsurface and ionospheric sounding marsis topside radar sounder on board the mars express spacecraft artificial ionospheric traces corresponding to how the marsis instrument would see model electron density profiles are constructed and they are inverted using the standard routine ideally this should result in the original electron density profiles however it is found that discrepancies between the original and resulting electron density profiles may be significant in particular at larger solar zenith angles and for higher spacecraft altitudes this is due to a gap of marsis time delay measurements at low sounding frequencies and a necessity to interpolate electron density profiles in this plasma frequency range although the ionospheric scale height likely increases with the altitude the standard inversion routine uses an exponential interpolation with a constant scale height we suggest a new inversion method which takes into account expected shapes of ionospheric profiles in the interpolation region we verify the performance of this method both on the model electron density profiles and on real marsis data we demonstrate that it seems to perform considerably better than the standard routine in particular for higher spacecraft altitudes finally we use the new inversion method to obtain a revised dependence of the peak altitude on the solar zenith angle

oblique reflections in the mars express marsis data set stable density structures in the martian ionosphere the mars advanced radar for subsurface and ionospheric sounding marsis onboard the european space agency s mars express mex spacecraft routinely detects evidence of localized plasma density structures in the martian dayside ionosphere such structures likely taking the form of spatially extended elevations in the plasma density at a given altitude give rise to oblique reflections in the active ionospheric sounder data these structures are likely related to the highly varied martian crustal magnetic field in this study we use the polar orbit of mex to investigate the repeatability of the ionospheric structures producing these anomalous reflections examining data taken in sequences of multiple orbits which pass over the same regions of the martian surface under similar solar illuminations within intervals lasting tens of days presenting three such examples or case studies we show for the first time that these oblique reflections are often incredibly stable indicating that the underlying ionospheric structures are reliably reformed in the same locations and with qualitatively similar parameters the visibility or lack thereof of a given oblique reflection on a single orbit can generally be attributed to variations in the crustal field within the ionosphere along the spacecraft trajectory we show that within these examples oblique reflections are generally detected whenever the spacecraft passes over regions of intense near radial crustal magnetic fields i e with a cusp like configuration the apparent stability of these structures is an important feature that must be accounted for in models of their origin

triassic paleomagnetic results from the yangtze block s e china in an effort to contribute to the refinement of the apwp for the yangtze block samples for paleomagnetic analyses were recovered from early triassic sediments in hunan province in southeast china the samples were taken from opposite limbs of a large syncline in order to apply the fold test and rock magnetic experiments were performed to determine the carriers of remanence however instead of refining the apwp the results present some problems while the sites pass the fold test the declinations deviate clockwise with respect to the reference apwp for the block but agree well with other reported results due to the paucity of reliable triassic results from the yangtze block and to the small number of sites from this study it is difficult to determine whether these sites have been rotated or the apwp is incorrect both possibilities are explored

shapes of magnetically controlled electron density structures in the dayside martian ionosphere nonhorizontal localized electron density structures associated with regions of near radial crustal magnetic fields are routinely detected via radar oblique echoes on the dayside of mars with the ionospheric sounding mode of the mars advanced radar for subsurface and ionospheric sounding marsis radar onboard mars express previous studies mostly investigated these structures at a fixed plasma frequency and assumed that the larger apparent altitude of the structures compared to the normal surrounding ionosphere implied that they are bulges however the signal is subjected to dispersion when it propagates through the plasma so interpretations based on the apparent altitude should be treated with caution we go further by investigating the frequency dependence i e the altitude dependence of the shape of 48 density structure events using time series of marsis electron density profiles corrected for signal dispersion four possible simplest shapes are detected in these time series which can give oblique echoes bulges dips downhill slopes and uphill slopes the altitude differences between the density structures and their edges are in absolute value larger at low frequency high altitude than at high frequency low altitude going from a few tens of kilometers to a few kilometers as frequency increases bulges dominate in numbers in most of the frequency range finally the geographical extension of the density structures covers a wide range of crustal magnetic fields orientations with near vertical fields toward their center and near horizontal fields toward their edges as expected transport processes are suggested to be a key driver for these density structures

investigations on intra annual elevation changes using multi temporal airborne laser scanning data case study engabreen norway key issues of glacier monitoring are changes in glacier geometry and glacier mass as accurate direct measurements are costly and time consuming the use of various remote sensing data for glacier monitoring is explored one technology used and described here is airborne laser scanning the method enables the derivation of high quality digital elevation models dems with a vertical and horizontal accuracy in the sub metre range between september 2001 and august 2002 three laser scanner data acquisition flights were carried out covering the whole area of engabreen norway and corresponding well to the measurement dates for the mass balance year 2001 02 the data quality of the dems is assessed e g by comparing the values with a control area which has been surveyed independently or gps ground profiles measured during the flights for the whole glacier surface elevation change and consequently volume change is calculated quantified and compared with traditional mass balance data for the same time interval for the winter term emergence submergence velocity is determined from laser scanner data and snow depth data and is compared with velocity measurements at stakes the investigations reveal the high potential of airborne laser scanning for measuring the extent and the topography of glaciers as well as changes in geometry area volume

marine biodiversity through the late cenomanian early turonian palaeoceanographic controls and sequence stratigraphic biases changes in the marine macro and microfauna sedimentary geochemistry and surface water palaeoproductivity through the last 500 000 years of the cenomanian and first 300 000 years of the turonian are documented these are based on the succession at eastbourne the thickest and most complete section through the late cenomanian and early turonian in the anglo paris basin two levels of rapid faunal and geochemical change are identified one coincident with a significant increase in siliciclastic input at the base of the plenus marls member and the other with a marked drop in surface water productivity near the top of the same unit faunal change is demonstrated to be largely a pattern of immigration emigration rather than true extinction and our sequence stratigraphical analysis shows that it was coincident with major sea level changes no evidence is found to support the hypothesis that reduced bottom water oxygenation developed and was responsible for extinctions amongst the benthos in mid shelf environments the onset of pure chalk facies is interpreted to mark the breakdown of shelf break fronts and the spread of oligotrophic oceanic waters over much of the continental shelf initiated by rising sea level the cenomanian turonian event far from recording a mass extinction of shelf fauna is most probably an artifact caused by a significant switch in the nature of the surviving sedimentary record as a result of a major but perfectly ordinary oceanographic change

elevation and volume changes on the harding icefield alaska airborne surface elevation profiles of the harding icefield south central alaska were made in 1994 and 1996 thirteen glaciers were profiled along with the upper region of the icefield the profiles were compared to u s geological survey topographic maps made in the 1950s to obtain elevation and volume changes comparison of the changes for the different glaciers shows no significant correlation between volume change and the type of glacier or characteristics such as location aspect size slope or terminus changes estimated total volume change for this 43 year period is about 34 km 3 which corresponds to an area average elevation change of 21 m the estimated error in this elevation change of 5 m is mainly due to errors in the maps at higher elevations our measurements provide an accurate baseline against which future determinations of volume change can be made

a glacier inventory for south tyrol italy based on airborne laser scanner data a new approach to glacier inventory based on airborne laser scanner data has been applied to south tyrol italy it yields highly accurate results with a minimum of human supervision earlier inventories from 1983 and 1997 are used to compare changes in area volume and equilibrium line altitude a reduction of 32 was observed in glacier area from 1983 to 2006 volume change derived from the 1997 and 2006 digital elevation models was 1 037 km 3 and an ela rise of 54 m to almost 3000 m a s l was calculated for this period losses vary widely for individual glaciers but have accelerated for all south tyrolean glaciers since the first inventory in 1983

day to night transport in the martian ionosphere implications from total electron content measurements the nightside martian ionosphere is thought to be contributed by day to night transport and electron precipitation of which the former has not been well studied in this work we evaluate the role of day to night transport based on the total electron content tec measurements made by the mars advanced radar for subsurface and ionospheric sounding on board mars express this is accomplished by an examination of the variation of nightside tec in the time domain rather than the traditional solar zenith angle domain our analyses here being constrained to the northern hemisphere where the effects of crustal magnetic fields can be neglected reveal that day to night transport serves as the dominant source for the nightside martian ionosphere from terminator crossing up to time in darkness of 5 3 103 s beyond which it is surpassed by electron precipitation the observations are compared with predictions from a simplified time dependent ionosphere model we conclude that the solid body rotation of mars is insufficient to account for the observed depletion of nightside tec but the data could be reasonably reproduced by a zonal electron flow velocity of 1 9 km s 1

late pleistocene glaciers in the western rodna mountains romania abstract glacial landforms are commonly found throughout the highest belt above 1700 m a s l of the romanian carpathians this paper presents glacial geomorphological evidence from the z noaga mare z noaga iezerului and the western part of buh escu valley complex situated on the northern slope of the rodna mountains in the eastern carpathians romania gis based geomorphological mapping reveals five sets of moraines in glacial phases assigned to the late pleistocene the most extensive glacier was in western buh escu valley and had a surface area of 5 km2 and a length of 4 2 km and reached down to an altitude of 1086 m several methods were tested to determine the former elas of the glaciers using size specific aar the average ela for the oldest phase was 1765 m and rose to 1865 1960 2001 and 2025 m the last and youngest phase was characterised only by cirque glaciers comparison with previous studies shows that extents were over estimated

a paleoceanographic model for the late campanian early maastrichtian sedimentation in the polish carpathian flysch basin based on nannofossils abstract the study is a qualitative and semi quantitative analysis of calcareous nannofossils in marlstone and calcareous mudstone beds in a 4 6 m thick section of the kropivnik fucoid marls late campanian early maastrichtian in the skole nappe of the polish outer carpathians this turbiditic succession is conspicuous by its short term alternation of marlstone rich and siliciclastic rich packages ca 1 m thick a model for paleoceanographic control on sedimentation is proposed on the basis of nannofossil assemblages in the studied section the nannofossils form assemblages of mixed synsedimentary taxa derived from diverse marine environments differing in trophy water temperature and distance from land the mixing occurred due to submarine resedimentation processes the nannofossils indicate that the siliciclastic rich packages were deposited during periods of lowered water temperature decreased calcareous nannoplankton production and oligotrophic to mesotrophic water conditions which corresponded to the sea level fall and lowstand anti estuarine circulation and downwelling due to arising shelf break front are inferred as the factors responsible for oligotrophy in contrast in the marlstone rich packages the calcareous nannofossils indicate sedimentation during periods of significantly increased calcareous nannoplankton production which corresponded to the sea level rise and highstand the increased nannoplankton production is attributed to estuarine circulation and upwelling the changes in sea level and water circulation conform to the climate changes postulated independently for the late campanian early maastrichtian

atmospheric circulation upwelling and organic rich rocks in the mesozoic and cenozoic eras abstract by using the basic principles of atmospheric circulation and analogies from present circulation patterns it is possible to construct qualitative atmospheric circulation models on paleogeographic maps the wind patterns predicted by these models then serve as the basis for predicting the locations of ancient upwelling zones atmospheric circulation and upwelling models for seven geologic stages in the mesozoic and cenozoic were constructed and the distribution of the upwelling zones compared with the distribution of organic rich rocks for all time periods together the correlation was statistically significant when the individual time periods were analyzed separately the following pattern emerged significant correspondence between upwelling zones and organic rich rocks in the triassic middle early cretaceous to late cretaceous and middle paleogene to neogene no significant correspondence was found for the intervening times upwelling does not account for all organic rich rocks so called anoxic oceanic events and transgressions play an important role in their deposition it is suggested that upwelling contributes significantly to the pattern of organic rich rock distribution and is important in determining organic facies

comparison of greenland ice sheet topography measured by topsar and airborne laser altimetry a digital elevation model dem produced from airborne interferometric synthetic aperture radar topsar data of a 5 km spl times 65 km region of the greenland ice sheet is compared with multiple airborne laser altimeter profiles of the same surface topsar derived elevation values were calculated on a 10 m spl times 10 m grid surface topography at wavelengths greater than one kilometer is accurately reproduced a planar adjustment of 8 m with along track and cross track tilts of 0 17 and 2 4 m km respectively is required to match the two elevation data sets residual noise of the topsar data at subkilometer wavelengths is less than two meters this study underscores the need for independent elevation data for controlling topsar elevation surveys

topside of the martian ionosphere near the terminator variations with season and solar zenith angle and implications for the origin of the transient layers abstract in this paper the morphological variations of the m2 layer of the martian ionosphere with the martian seasons and solar zenith angle sza at the terminator are investigated the data used are the marsis mars advanced radar for subsurface and ionosphere sounding measurements approximately 5000 ionograms that were acquired from 2005 to 2012 which have a sza 85 and detect the topside transient layers a simple effective data inversion method is developed for the situation in which the upper portion of the height profile is non monotonic and the observed data are insufficient for adequate reduction the inverted parameters are subsequently explored using a statistical approach the results reveal that the main body of the m2 layer approximately 10 km below the first topside layer can be well characterized as a chapman layer near the terminator sza 85 98 notwithstanding the high sza and the presence of the topside layers the height of the first topside layer tends to be concentrated approximately 60 km with a standard deviation of 20 km above the main density peak the peak density and height of the first topside layer are positively correlated to the density and height of the main peak respectively the density and height of the first topside layer appear to be independent of the sza but possess seasonal variations that are similar to those of the main layer the height of the topside layer is greater by 10 km on average in the southern spring and summer than in the southern autumn and winter coinciding with the observation that in the southern spring and summer the underlying atmosphere is warmer due to dust heating e g smith m d 2004 icarus 167 148 165 the statistical regularities of the parameters suggest a possibility that the formation of the topside layers are closely related to the processes of photoionization and diffusion that occur on the topside of the m2 layer we propose that development of beam plasma instabilities in the transitional region between the lower chapman region and the upper transport dominating region is possibly a mechanism that is responsible for the occurrences of the topside layers

nighttime ionosphere caused by meteoroid ablation and solar wind electron proton hydrogen impact on mars mex observation and modeling 1 we report that radio science rs experiment onboard mars express mex has observed three plasma layers in the nighttime ionosphere of mars at altitudes 80 100 km 120 km and 160 km which are reproduced by model calculation due to impact of meteoroid solar wind proton and electron respectively the densities of 21 ions mg fe si mgo mgco2 mgo2 mgn2 feo feo2 fen2 feco2 sio sico2 sin2 sio2 co2 n2 o o2 co and no have been computed between altitude 50 km and 200 km the model shows that all atmospheric ions co2 n2 o co o2 and no are produced above 100 km due to solar wind electron and proton impact ionizations the metallic ions are formed between 50 km and 100 km due to ablation of micrometeoroids it is found that mass 3 0 10 4 g of incoming meteoroid is sufficient for meteor ablation and its characteristic flux 4 0 10 15 cm 2s 1 could produce the nighttime metallic layer observed by mex the calculated electron densities are also compared with the occultation measurements made by mars 4 5 in the nighttime ionosphere of mars

the new remote sensing derived swiss glacier inventory ii first results complete swiss glacier inventories are available for 1850 reconstructed and 1973 from aerial photography connected to the global land ice measurements from space project a new swiss glacier inventory for approximately the year 2000 sgi 2000 is compiled mainly based on satellite imagery the developed and applied remotesensing and geographical information system gis methods are described in part i of the contribution in part ii the inventory design first result analyses and comparisons with former glacial conditions are presented as basic entries sgi 2000 contains the individual glacier identification planimetric glacier boundaries as derived from image analysis digitized central flowlines and polygonal glacier basin maps all other parameters are automatically deduced from the above entries and a digital elevation model within a gis here we analyze a set of small bernese and valais glaciers of area 2 these glaciers lost about 21 of area from 1973 to 1998 in addition to about 80 during 1850 1973 both with respect to the 1973 area in order to track the latest trend in more detail anintermediate glacier condition has been compiled from satellite imagery of 1985 this analysis gave an increasing speed of area loss 19 for 1985 98

combining airborne and terrestrial laser scanning for quantifying erosion and deposition by a debris flow event abstract we quantified the sediment volume transported by a major debris flow event in the halltal austrian alps using a combination of terrestrial tls and airborne laser scanning als which has rarely been carried out before a digital terrain model dtm derived from als data pre event surface was combined with a dtm derived from tls data post event surface both datasets were aligned and compared in a cut and fill analysis estimating differential volumes the main focus lay on the evaluation and accuracy assessment of the applied method tie point based registration of both datasets proved to be insufficient additional alignment by multi station adjustment was necessary to minimise the averaged height error between both datasets amounting for a volumetric error of less than 10 which is comparable to pure als campaigns larger errors were estimated for complex terrain with low scanning resolutions a particular problem in data processing was the low and dense shrub vegetation in the study area which required a specifically adapted filter algorithm an insufficient ground representation was observed for the als data overestimating ground heights for averaged 70 cm despite these limitations the approach proved to be suitable for accurate extreme event quantification the starting zones of the debris flows lie at the bedrock debris interface where runoff is concentrated volumes of 5000 to 12 000 m3 were assessed volume estimation worked better for the erosional than for the depositional features this is because the erosional gullies are relatively deep and the calculation is not affected by pre event vegetation while erosion and sedimentation are balanced for one of the three catchments investigated the deposited volumes are higher than the detected eroded volumes for the other two the reasons are not fully understood the magnitude of the flows was determined by catchment size topographical characteristics and deforestation by a major wildfire in 1946

cretaceous climate a comparison of atmospheric simulations with the geologic record abstract atmospheric simulations using realistic cretaceous geography 100 million years ago suggest that paleography is an important factor governing the nature of the circulation the simulated cretaceous atmospheric circulations are markedly different both from the present day atmospheric circulation and from the classical hypotheses of a weaker circulation and poleward displacement of circulation features e g the subtropical high therefore they pose specific questions which can be tested against the geologic record aspects of the cretaceous simulations are verified in comparisons with the geologic record the simulations serve to guide areas of future paleoclimatic research and to formulate better the nature of the problem of warm equable climates

methods for assessing and forecasting the survival of north cascade washington glaciers abstract north cascade glacier annual balance measured on 10 glaciers from 1984 to 2009 yielded mean annual balance ba of 0 51 m y and 13 26 m cumulatively this is a significant loss for glaciers that average 30 60 m in thickness 20 40 of their entire volume this rapid volume loss has led to the complete loss of two glaciers spider and lewis glacier this indicates the need for a method of forecasting glacier survival in the region temperate alpine glacier survival is dependent on the consistent presence of an accumulation zone if a glacier does not have a persistent accumulation zone all areas of the glacier will experience thinning including the former accumulation zone examination of the accumulation zone can identify thinning from substantial marginal recession emergence of new rock outcrops and surface elevation declines in the accumulation zone nine of the 12 north cascade glaciers examined exhibit these characteristics each glacier that exhibited accumulation zone thinning features also had frequent low annual accumulation area ratio values below 0 30 this indicates the lack of a persistent accumulation zone

rainfall patterns and the distribution of coals and evaporites in the mesozoic and cenozoic abstract paleoclimatologists have adequately demonstrated over the last twenty years that the distribution of climatically sensitive sediments can be related to present day climatic zones that are roughly parallel to latitude for example coals were deposited at paleolatitudes that correspond to the present day rainy zones at the equator and at about 55 n and 55 s indicating that those zones were present in the past from this it can be concluded that atmospheric circulation has not been radically different from its present configuration despite some apparently great differences in some climatic parameters such as the equator to pole temperature gradient nevertheless the zonal model for predicting the distribution of climatically sensitive sediments is not wholly adequate although general atmospheric circulation may not have been radically altered from its present pattern it would have differed in some respects because the paleogeography was different from the present geography therefore we have constructed what we believe are more realistic maps of the distribution of rainfall through time these maps are based on maps of atmospheric circulation that have been successfully used to predict the distribution of some petroleum source beds and phosphorites we have compared the predicted distribution of rainfall to the distribution of coals and evaporites for each of seven geologic stages the circulation rainfall maps were more successful than the zonal model for predicting the distribution of evaporites and coals for times when the paleogeography would have maximized the development of a monsoonal circulation which most effectively disrupts the general zonal pattern for times when a monsoonal circulation would not have been important the zonal model adequately predicted the distribution of these rocks

marsis observations of the martian nightside ionosphere dependence on solar wind conditions despite the absence of solar radiation on the martian nightside a weak irregular and variable ionosphere is produced there the nightside ionosphere is thought to be maintained by two main sources dayside nightside plasma transport and electron precipitation observations by mars express mex and mars global surveyor mgs have shown that these plasma sources are either hindered or favored by the presence of strong crustal magnetic fields and that these effects are modulated by external parameters such as the solar wind dynamic pressure and the orientation of the interplanetary magnetic field imf these external drivers are expected to influence the supply of plasma to the nightside and thus the formation of the irregular nightside ionosphere we here present a statistical study of the martian ionosphere at solar zenith angle greater than 107 from november 2005 to may 2006 using remote measurements of ionospheric echoes with the mars advanced radar for subsurface and ionospheric sounding marsis radar sounder onboard mex and using mgs based proxies for the solar wind dynamic pressure and the imf clock angle we find that the peak densities increase with the dynamic pressure and also that cases of very high peak density are almost always associated with westward imf orientation we find that using mex aspera 3 electron data these cases often seem to be linked to accelerated electrons plasma transport is known to be important in the near nightside on the other hand electron precipitation prevails when the dynamic pressure is high enough to compress the ionosphere and in vertical field regions where the imf orientation matters

radar soundings of the ionosphere of mars we report the first radar soundings of the ionosphere of mars with the marsis mars advanced radar for subsurface and ionosphere sounding instrument on board the orbiting mars express spacecraft several types of ionospheric echoes are observed ranging from vertical echoes caused by specular reflection from the horizontally stratified ionosphere to a wide variety of oblique and diffuse echoes the oblique echoes are believed to arise mainly from ionospheric structures associated with the complex crustal magnetic fields of mars echoes at the electron plasma frequency and the cyclotron period also provide measurements of the local electron density and magnetic field strength

characterizing average electron densities in the martian dayside upper ionosphere we use more than 10years of the martian topside ionospheric data measured by the mars advanced radar for subsurface and ionosphere sounding radar sounder on board the mars express spacecraft to der

nightside ionosphere of mars radar soundings by the mars express spacecraft 1 we present results of a survey of the nightside ionosphere of mars as observed by mars advanced radar for subsurface and ionospheric sounding marsis on board the mars express spacecraft the occurrence rate of the nightside ionosphere is studied as a function of solar zenith angle sza magnetic field magnitude and magnetic field inclination it is shown that at locations with weak crustal magnetic fields the occurrence rate of the nightside ionosphere decreases with increasing sza up to about 125 suggesting that plasma transport from the dayside plays a crucial role in its formation however at locations with strong crustal magnetic fields the dependence on sza is no longer apparent and the inclination of magnetic field becomes a crucial parameter the occurrence rate of the nightside ionosphere is more than 4 times larger at locations with nearly vertical magnetic fields as compared to the locations with nearly horizontal magnetic fields this indicates that impact ionization by precipitating electrons is the main ionization source at these locations observed peak electron densities are less than 2 104 cm 3 in the vast majority of cases lower estimates of altitudes of peak electron densities are mostly between 100 and 150 km

paleoceanographic changes across the jurassic cretaceous boundary the calcareous phytoplankton response abstract calcareous nannoplankton experienced rapid diversification at the jurassic cretaceous boundary including the appearance of several highly successful and long ranging cretaceous genera this study examines at high resolution calcareous nannofossil assemblages and bulk rock oxygen and carbon isotopes of lower tithonian to lower berriasian 151 to 142 ma sediments recovered in deep sea drilling project hole 534a central atlantic ocean the results show major changes in assemblage composition and abundance of three genera conusphaera nannoconus and polycostella conusphaera dominates the nannolith assemblage in the late middle tithonian conusphaera world while the nannoconid dominance nannoconus world began in the berriasian the acme peak of the genus polycostella in the late tithonian partially superimposes that of conusphaera although these genera are indicators of warm oligotrophic surface waters stable isotope data suggest that the individual taxa may flourish in slightly different ecological regimes nannoconus flourished under warmer and possibly more nutrient depleted surface waters than polycostella a genus that thrived in relatively cooler waters these findings imply paleoceanographic changes across the j k boundary interval with a cooling in the late tithonian followed by a temperature increase in the berriasian because the transfer of these heavily calcified nannolith taxa to the seafloor is more efficient than that of average coccolithophorids the j k evolutionary event changed carbonate cycling and burial in the oceans

origin of limestone marlstone cycles astronomic forcing of organic rich sedimentary rocks from the cenomanian to early coniacian of the cretaceous western interior seaway usa abstract we present an integrated multidisciplinary study of limestone marlstone couplets from a continuously cored section including parts of the upper buda limestone the entire eagle ford group boquillas formation and lower austin chalk from the shell iona 1 research borehole texas usa which provides a 8 million year myr distal clastic sediment starved intrashelf basin record of the early cenomanian to the earliest coniacian stages results show that despite variable yet minimal diagenetic overprints several unambiguous primary environmental signals are preserved and support greater water mass ventilation and current activity promoting increased silica carbonate productivity during the deposition of limestone beds compared to deposition of marlstone beds which reflect greater organic matter productivity and preservation furthermore our astronomical analyses demonstrate that the limestone marlstone couplets in the iona 1 core reflect climatic forcing driven by solar insolation resulting from integrated milankovitch periodicities in particular we propose that obliquity and precession forcing on the latitudinal distribution of solar insolation may have been responsible for the observed lithological and environmental variations through the cenomanian turonian and coniacian in this mid latitude epicontinental sea setting our data also suggests that rhythmic lithological alternations deposited in greenhouse periods in general may simply reflect climate driven cycles related to earth sun dynamics without the need to invoke significant sea level variations

rapid disintegration of alpine glaciers observed with satellite data analyses of multispectral satellite data indicate accelerated glacier decline around the globe since the 1980s by using digitized glacier outlines inferred from the 1973 inventory and landsat thematic mapper tm satellite data from 1985 to 1999 we obtained area changes of about 930 alpine glaciers the 18 area reduction as observed for the period 1985 to 1999 1 3 a corresponds to a seven times higher loss rate compared to the 1850 1973 decadal mean extrapolation of area change rates and cumulative mass balances to all alpine glaciers yields a corresponding volume loss of about 25 km since 1973 highly individual and non uniform changes in glacier geometry disintegration indicate a massive down wasting rather than a dynamic response to a changed climate our results imply stronger ongoing glacier retreat than assumed so far and a probable further enhancement of glacier disintegration by positive feedbacks

extracting a climate signal from 169 glacier records i constructed a temperature history for different parts of the world from 169 glacier length records using a first order theory of glacier dynamics i related changes in glacier length to changes in temperature the derived temperature histories are fully independent of proxy and instrumental data used in earlier reconstructions moderate global warming started in the middle of the 19th century the reconstructed warming in the first half of the 20th century is 0 5 kelvin this warming was notably coherent over the globe the warming signals from glaciers at low and high elevations appear to be very similar

uncertainty assessment of multi temporal airborne laser scanning data a case study on an alpine glacier in glaciology volumetric changes from multi temporal digital elevation models dems serve to validate and calibrate glacier mass balances from traditional in situ measurements in this study we provide a thorough uncertainty assessment of multi temporal airborne laser scanning dems based on a applying a statistical error model b comparing laser echoes to reference points and surfaces and c developing a physical error propagation model the latter model takes into account the measurement platform characteristics components of the measurement process and the surface properties such a model allows the estimation of systematic and stochastic uncertainties for single laser echoes as well as for distributed surfaces in every part of the study site independent of the reference surfaces the full error propagation framework is applied to multi temporal dems covering the highly undulating terrain in the findelengletscher catchment in canton valais switzerland this physical error propagation model is able to reproduce stochastic uncertainties in accordance with measurements from reference surfaces the high laser point density in the study site reduces the stochastic uncertainties over the whole glacier area to negligibly small values however systematic uncertainties greatly influence the calculation of mass changes and lead to corrections of the thickness change of up to 35

ice volume changes of selected glaciers in the swiss alps since the end of the 19th century the evolution of surface topography of glaciers in the swiss alps is well documented with high resolution aerial photographs repeatedly recorded since the 1960s and further back in time with topographic maps including elevation contour lines first surveyed in the mid 19th century in order to quantify and interpret glacier changes in the swiss alps time series of volume changes over the last 100 150 years have been collected the available datasets provide a detailed spatial resolution for the retreat period since the end of the little ice age the spatial distribution as well as temporal variations of the thickness change were analyzed a significant ice loss since the end of the 19th century was observed in the ablation area while the changes in the accumulation area were small we found moderate negative secular rates until the 1960s followed by steady to positive rates for about two decades and strong ice loss starting in the 1980s which has lasted until the present an evaluation of 19 glaciers revealed a total ice volume loss of about 13 km 3 since the 1870s of which 8 7 km 3 occurred since the 1920s and 3 5 km 3 since 1980 decadal mean net balance rates for the periods 1920 60 1960 80 and 1980 present are 0 29 0 03 and 0 53 m a 1 w e respectively

airborne surface profiling of glaciers a case study in alaska a relatively lightweight and simple airborne system for surface elevation profiling of glaciers in narrow mountain valleys has been developed and tested the aircraft position is determined by kinematic global positioning system gps methods the distance to the glacier surface is determined with a laser ranger the accuracy is about 0 3 m sufficient to permit future changes to be observed over short time intervals long term changes can be estimated by comparison of profiles with existing maps elevation profiles obtained in 1993 94 from three glaciers in central and south central alaska are compared with maps made about 1950 the resulting area averaged seasonally corrected thickness changes during the interval are gulkana glacier central alaska range 11 m worthington glacier central chugach mountains 7 m and bear lake glacier kenai mountains 12 m all three glaciers retreated during the interval of comparison the estimated uncertainty in the average thickness change is 5 m which is mainly due to errors in the existing maps constraints on the accuracy of the maps are obtained by profiling in proglacial areas

areas of enhanced ionization in the deep nightside ionosphere of mars 1 we present observations of areas of enhanced ionization located in the deep nightside ionosphere of mars as observed by mars advanced radar for subsurface and ionospheric sounding marsis on board the mars express spacecraft oblique ionospheric echoes coming from the same region observed during several consecutive marsis measurements enable us to constrain the geographic location of the reflection area that is the source of the echoes we have identified 90 such events in all available data none of the reflection areas are located in regions typically having a closed magnetic field line configuration the locations of the reflection areas of enhanced plasma density are consistent with the ionization due to precipitating electrons on field lines connected to the collisional atmosphere reflection areas observed in regions of stronger magnetic field are found to have larger plasma number density we use a model of martian crustal magnetic field lines to demonstrate that the magnetic field has a focusing effect on incident particles electron impact ionization is thus expected to take place only in well defined areas in agreement with our observations our observations show that the deep nightside ionosphere of mars is very irregular controlled primarily by the configuration of crustal magnetic fields

geodetic airborne laser altimetry of breidamerkurjokull and skeidararjokull iceland and jakobshavns isbrae west greenland

nightside electron precipitation at mars geographic variability and dependence on solar wind conditions 1 electron precipitation is usually the dominant source of energy input to the nightside martian atmosphere with consequences for ionospheric densities chemistry electrodynamics communications and navigation we examine downward traveling superthermal electron flux on the martian nightside from may 1999 to november 2006 at 400 km altitude and 2 a m local time electron precipitation is geographically organized by crustal magnetic field strength and elevation angle with higher fluxes occurring in regions of weak and or primarily vertical crustal fields while stronger and more horizontal fields retard electron access to the atmosphere we investigate how these crustal field organized precipitation patterns vary with proxies for solar wind sw pressure and interplanetary magnetic field imf direction generally higher precipitating fluxes accompany higher sw pressures specifically we identify four characteristic spectral behaviors 1 stable regions where fluxes increase mildly with sw pressure 2 high flux regions where accelerated peaked spectra are more common and where fluxes below 500 ev are largely independent of sw pressure 3 permanent plasma voids and 4 intermittent plasma voids where fluxes depend strongly on sw pressure the locations sizes shapes and absence existence of these plasma voids vary significantly with solar wind pressure proxy and moderately with imf proxy direction average precipitating fluxes are 40 lower in strong crustal field regions and 15 lower globally for approximately southwest proxy directions compared with approximately northeast directions this variation of the strength and geographic pattern of the shielding effect of mars crustal fields exemplifies the complex interaction between those fields and the solar wind

airborne measurement of glacier surface elevation by scanning laser altimeter airborne scanning laser altimetry is a relatively new technique for remote sensing ofground elevation a laser ranger is scanned across a swath beneath the aircraft producing a two dimensional distribution of elevations when combined with d ata on aircraft position and orientation smooth snow covered glaciers are ideal surfaces for las er scanning since they are highly refl ective a new prototype laser sys tem is des cribed together with results from hardangerjokulen norway an a nalys is o f the data shows that noise levels are very low at around 2 cm and th at repeatability between over lapping swaths is approximately 10 cm this is consistent with an absolute accuracy of 15 cm or better from manufacturer s and other measurements swath widths of over i km are attainable allowing complete coverage of sma ll to medium siz ed glaciers using para l lel oight tracks the hi g h accuracy and dense even coverage about 20000 points per km 2 gives good quality derived products such as de m s and enables reliable measure ment of glacier volume change scanning laser a ltimetr y has many advantages over photogrammetry whi ch was previously the only remote se nsing method o f measuring elevations over large a reas but which performs poorly over snow covered glaciers

climate at the equilibrium line of glaciers the relationships between temperature precipitation and radiation on glacier equilibrium lines are investigated using 70 glaciers for which the mass balance and meteorological observations have been carried out for sufficiently long periods it is found that the characteristic climate at glacier equilibrium lines can be described using the summer 3 months temperature in a free atmosphere annual total precipitation and the sum of global and long wave net radiation all of these are measured at or very near the equilibrium line altitudes then it is shown how the shift of the equilibriumline will occur as a result of a climatic change finally the effect of the shift of the equilibrium line on the annualmean specific mass balance is analytically derived and compared with observations the present results make it possible to identify the altitudes in climate models where glacierization should begin and to evaluate the mass balance changes as a result of possible future changes in the climate

enhanced ionization of the martian nightside ionosphere during solar energetic particle events electron densities in the martian nightside ionosphere are more than 90 of time too low to be detected by the mars advanced radar for subsurface and ionosphere sounding radar sounder on board the mars express spacecraft however the relative number of ionograms with peak electron density high enough to be detected represents a good statistical proxy of the ionospheric density we focus on solar energetic particle sep events and we analyze their effects on ionospheric formation sep time intervals were identified in situ using the background counts recorded by the ion sensor of the aspera 3 instrument on board mars express we show that peak electron densities during the sep events are large enough to be detected in more than 30 of measurements and moreover the reflections of the sounding signal from the ground almost entirely disappear nightside electron densities during sep events are thus substantially increased as compared to normal nightside conditions

oblique reflections of mars express marsis radar signals from ionospheric density structures raytracing analysis mars advanced radar for subsurface and ionosphere sounding marsis radar sounder on board the mars express spacecraft revealed oblique reflections coming systematically from apparently stable dens

the new remote sensing derived swiss glacier inventory i methods a new swiss glacier inventory is to be compiled from satellite data for the year 2000 the study presented here describes two major tasks 1 an accuracy assessment of different methods for glacier classification with landsat thematic mapper tm data and a digital elevation model dem 2 the geographical information system gis based methods for automatic extraction of individual glaciers from classified satellite data and the computation of three dimensional glacier parameters such as minimum maximum and median elevation or slope and orientation by fusion with a dem first results obtained by these methods are presented in part ii of this paper kaab and others 2002 thresholding of a ratio image from tm4 and tm5 reveals the best suited glacier map the computation of glacier parameters in a gis environment is efficient and suitable for worldwide application the methods developed contribute to the u s geological survey led global land ice measurements from space glims project which is currently compiling a global inventory of land ice masses within the framework of global glacier monitoring haeberli and others 2000

dayside ionosphere of mars empirical model based on data from the marsis instrument 1 we present results of a systematic study of electron densities in the dayside martian ionosphere measured by the mars advanced radar for subsurface and ionosphere sounding marsis instrument on board the mars express spacecraft there are two distinct regions controlled by different physical mechanisms the first region is located at altitudes up to about 5 neutral scale heights above the altitude of peak electron density electron densities in this region are well described by the basic chapman theory the observed small deviations can be most probably explained by the neutral scale height and electron temperature increasing with altitude rather than being constant the second region is located at altitudes higher than about 10 neutral scale heights above the altitude of peak electron density it is controlled primarily by diffusion and the observed electron densities decrease exponentially with increasing altitude the corresponding diffusion scale height increases with increasing solar zenith angle which can be probably explained by nearly horizontal magnetic fields in the ionosphere induced by interaction with the solar wind the obtained dependencies can be used as a simple empirical model of the dayside martian ionosphere

a theoretical approach to glacier equilibrium line altitudes using meteorological data and glacier mass balance records from southern norway based on a close exponential relationship between mean ablation season temperature and winter precipitation at the equilibrium line altitude ela of 10 norwegian glaciers three equations are derived the e rst equation enables calculation of the minimum altitude of areas climatically suited for glacier formation and is termed the altitude of instantaneous glacierization aig equation 2 is derived based on the principle of terrain adaptation enabling quantie cation of the glacial buildup sensitivity gbs in presently non glaciated areas the theoretical climatic temperature precipitation ela c tp ela in presently non glaciated areas is calculated in equation three by combining gbs with terrain altitude mass balance records from four modern glaciers a lfotbreen nigardsbreen storbreen and gra subreen situated in maritime to continental climate regimes in southern norway are used to test these equations correlation between aig and net balance measure ments bn yielded correlation coefe cients of r 0 80 to r 0 84 calculated aigs correspond well with observed elas on a lfotbreen nigardsbreen and gra subreen while it deviates from the observed ela on storbreen the latter is probably due to leeward accumulation of wind blown snow on this cirque glacier based on this approach regional representative climatic elas can be calculated for non glaciated areas with instrumental records of ablation season temperature and winter precipitation

nannofossil assemblages fine fraction stable isotopes and the paleoceanography of the valanginian barremian early cretaceous north sea basin calcareous nannofossil assemblages have been investigated in three sections from around the margins of the early cretaceous north sea basin both absolute number of nannofossils per gram and relative percent of the assemblage of different taxa abundance data have been collected absolute abundances up to 10 billion nannofossils per gram are somewhat higher than those reported previously from other stratigraphic intervals stratigraphic correlation of trends in assemblage data in different sections points toward the existence of large uniform water masses stable over long 0 5 to 1 m y time periods these water masses contained a characteristic nannoplankton which appears to have been driven largely by variations in fertility possibly tied to changes in sources of surface waters which in turn may have been controlled by relative sea level fine fraction isotopic data show fluctuations on shorter time periods 0 1 to 0 5 m y we postulate that some of these isotopic fluctuations were controlled by relative changes in sea level which affected the balance of surface waters derived from runoff and those imported from the boreal sea these oceanographic changes appear to have affected nannofossil assemblages only in discrete intervals data are available with entire article on microfiche order from american geophysical union 2000 florida avenue n w washington dc 20009 document p95 001 2 50 payment must accompany order

current transition from glacial to periglacial processes in the dolomites south eastern alps abstract a close relationship between glacial and periglacial landforms is frequently observed in alpine environments where a transition from glacial to periglacial processes often took place after the end of the little ice age lia understanding the origin of these landforms is challenging and assessing the current spatial domain of glacial and periglacial processes may be a difficult task in high relief areas where thick and widespread debris cover often characterize rapidly decaying glaciers here we present a comprehensive study of a composite landform located in the dolomites south eastern alps combining geomorphological geophysical and topographic surveys with ground surface temperature measurements results indicate that a debris covered glacier persists in the upper part rather large compared to the lia extent but currently inactive and rapidly losing mass an active rock glacier exists in the lower part surrounded by discontinuous permafrost a frozen body about 10 m thick was detected in the rock glacier and geomorphological evidence suggests that this ice mass is completely detached from the debris covered glacier our findings suggest that the lower part of the composite landform is probably a remnant of the ancient glacier tongue and is currently evolving under periglacial conditions periglacial processes are therefore replacing glacial processes which dominated in this site during the lia

mapping crustal magnetic fields at mars using electron reflectometry 1 we present a kinetic model for the interaction of electrons precipitating along magnetic field lines into mars atmosphere and develop a technique for detecting crustal magnetic fields which act as magnetic mirrors reflecting some of the incident electrons back to spacecraft altitudes we present an initial map covering 20 of the planet which shows the topology of magnetic sources along the dichotomy boundary and reveals new magnetic sources in the northern lowlands implying the existence of preserved noachian crust beneath at least some regions of the apparently young plains

elevation volume and terminus changes of nine glaciers in north america nine glaciers in alaska and washington u s a originally mapped as part of the international geophysical year igy in 1957 58 were re mapped between 1993 and 1996 eight using airborne surface elevation profiling and the ninth using ground based kinematic global positioning system methods elevation volume and terminus changes were determined for the approximately 38 year period between the igy mapping and the profiling all nine glaciers showed substantial thinning at lower elevations seven of the nine thickened at higher elevations none of the glaciers had a significant net volume increase two had close to zero change and the others had a decrease for the eight glaciers for which we could obtain quantitative information the mean thickness change was 10 m with a large scatter 8 m standard deviation the volume and terminus changes had no clear geographic pattern and no simple relationship between volume change and terminus advance or retreat was identified the largest error in the estimated volume changes is due to map errors

intensity of nightside marsis ais surface reflections and implications for low altitude ionospheric densities spacecraft radar sounding signals at frequencies higher than the ionospheric peak plasma frequency are not reflected by the ionosphere instead they make it to the ground where they are reflected by the planetary surface we analyze the intensity of the surface reflections measured by the mars advanced radar for subsurface and ionosphere sounding marsis ionospheric radar sounder on board the mars express spacecraft apart from the surface reflectivity and the spacecraft altitude the detected intensity of surface reflections is controlled primarily by the signal attenuation during the ionospheric propagation we focus on the nightside region where the ionospheric densities in the main layer are too low to cause a significant attenuation and allow sampling of the surface reflections at frequencies down to 3 mhz the attenuation occurs mainly at altitudes below 100 km where the electron neutral collision frequency is a maximum the intensity of surface reflections can thus serve as a proxy for electron densities at low altitudes not accessible by the direct ionospheric radar sounding we analyze the intensity of surface reflections as a function of relevant controlling parameters the intensity of surface reflections is lower at higher solar zenith angles on the nightside and during the periods of larger solar activity moreover it exhibits a seasonal variation that is related to the dust storm occurrence the intensity of surface reflections is lower in areas of closed magnetic field lines suggesting that nightside electron densities behave rather differently at low altitudes than at higher altitudes this is confirmed by comparison with simultaneous observations of the main ionospheric layer

warm saline bottom water in the ancient ocean considerable isotopic evidence indicates that oceanic bottom water was much warmer in the geological past a simple convection model driven by multiple turbulent buoyant plumes and observations of present deep water formation have led to the development of a theory for the formation of warm saline bottom water it is suggested that changes in the size and configuration of marginal seas in net evaporation zones due to lithospheric plate motions and eustatic sea level change caused these seas to become sources of warm saline bottom water evidence from the palaeotemperature record and palaeogeography during the late cretaceous is used to reinforce the hypothesis climatic and chemical consequences of the formation of warm saline bottom water are discussed

a warm equable cretaceous the nature of the problem abstract the nature of the problem of warm equable paleoclimates is defined by investigating the mid cretaceous period the problem consists of three components 1 defining precisely the climatic state during any specified interval of geologic time 2 specifying the external climatic forcing factors which may have been important and 3 understanding the climatic response to any specific modifying influence these components are characterized by limitations of critical importance in understanding paleoclimates the nature of the problem of a warm cretaceous is defined both qualitatively and quantitatively within these limits

ionospheric electron densities at mars comparison of mars express ionospheric sounding and maven local measurements we present the first direct comparison of martian ionospheric electron densities measured by the mars advanced radar for subsurface and ionospheric sounding marsis topside radar sounder on board the mars express spacecraft and by the langmuir probe and waves lpw instrument on board the mars atmosphere and volatile evolution mission maven spacecraft as low electron densities are not measured by marsis due to the low power radiated at low sounding frequencies marsis electron density profiles between the local electron density and the first data point from the ionospheric sounding 104 cm 3 rely on an empirical electron density profile shape we use the lpw electron density measurements to improve this empirical description and thereby the marsis derived electron density profiles we further analyze four coincident events where the two instruments were measuring within a five degree solar zenith angle sza interval within one hour the differences between the electron densities measured by the marsis and lpw instruments are found to be within a factor of two in 90 of measurements taking into account the measurement precision and different locations and times of the measurements these differences are within the estimated uncertainties

estimation of the total electron content of the martian ionosphere using radar sounder surface echoes 1 the martian ionosphere s local total electron content tec and the neutral atmosphere scale height can be derived from radar echoes reflected from the surface of the planet we report the global distribution of the tec by analyzing more than 750 000 echoes of the mars advanced radar for subsurface and ionospheric sounding marsis this is the first direct measurement of the tec of the martian ionosphere the technique used in this paper is a novel transmission mode sounding of the ionosphere of mars in contrast to the active ionospheric sounding experiment ais on marsis which generally operates in the reflection mode this technique yields a global map of the tec for the martian ionosphere the radar transmits a wideband chirp signal that travels through the ionosphere before and after being reflected from the surface the received waves are attenuated delayed and dispersed depending on the electron density in the column directly below the spacecraft in the process of correcting the radar signal we are able to estimate the tec and its global distribution with an unprecedented resolution of about 0 1 deg in latitude 5 km footprint the mapping of the relative geographical variations in the estimated nightside tec data reveals an intricate web of high electron density regions that correspond to regions where crustal magnetic field lines are connected to the solar wind our data demonstrates that these regions are generally but not exclusively associated with areas that have magnetic field lines perpendicular to the surface of mars as a result the global tec map provides a high resolution view of where the martian crustal magnetic field is connected to the solar wind we also provide an estimate of the neutral atmospheric scale height near the ionospheric peak and observe temporal fluctuations in peak electron density related to solar activity

early turonian pelagic sedimentation at moria umbria marche italy primary and diagenetic controls on lithological oscillations abstract the upper cretaceous of the umbria marche basin italy consists of an alternation of calcareous and siliceous fine grained sedimentary rocks in which the calcareous lithologies are predominant the cenomanian succession is dominated by white micritic limestones and contains a black shale horizon bonarelli level in its uppermost part which is the regional expression of oceanic anoxic event 2 in the turonian the rocks gradually become red upwards and are referred to as cretaceous oceanic red beds the lithological variability in the succession reflects the local response of sedimentary systems to varying local and global environmental conditions in this study local processes behind the transition from black shale to red bed deposition and in particular behind lithological oscillations within the lowermost turonian are studied and placed in their global context sediment colour composition geochemistry and nannofossil content were studied using samples of the scaglia formation at moria umbria marche basin the results show that following the cenomanian turonian boundary terrigenous input decreased and its composition was different in calcareous and siliceous oozes organic productivity was high during the deposition of siliceous ooze due to upwelling and varied on orbital timescales the alternation between the siliceous and calcareous ooze was further controlled by carbonate dissolution small fluctuations in the calcite compensation depth ccd had a significant impact on sediment composition because depositional depth was between the lysocline and the ccd diagenesis resulted in the segregation of carbonate and silica in the concentration of terrigenous material in smarl interbeds and in the enhancement of bedding after the earliest turonian ocean circulation patterns changed seawater temperatures declined slowly and seawater became better oxygenated productivity and terrigenous input also declined and the resulting combination of oxygen demand in the sediments and sedimentation rates favoured the formation of authigenic haematite in the sediments which led to their reddening

morphological changes in alpine rivers following the end of the little ice age abstract this work investigates the channel changes of alpine rivers from the end of the little ice age 1850s to the 1950s with the aim to determine the possible role of climatic variations occurred in this period before the onset of anthropic pressures i e dams check dams bank protections and gravel mining the research was conducted on 17 river catchments of south tyrol northern italy glaciated and unglaciated a multitemporal gis analysis approach was adopted to assess the morphological changes in terms of channel width and pattern from three different sources i austrian cadastral map 1858 ii maps from the italian institute of military geography 1917 1925 and iii two aerial photo sets taken in 1945 and 1954 the analysed river network a total of 480 km was subdivided into 162 morphologically homogeneous reaches 76 confined 81 partly confined and 5 unconfined with lengths ranging from 630 to 5500 m slope from 0 3 to 24 and drained area from 20 to 4000 km 2 the statistical relationships among morphological changes and reach and basin scale factors were analysed by univariate and multivariate methods and the relationships between width changes and 36 controlling factors were explored using principal component analysis the variability in width and morphological pattern changes were very pronounced between and within single rivers highlighting the value of such a large data set overall the analysed rivers varied their morphological pattern mostly exhibiting a shift from multithread transitional to single thread patterns but unchanged planform types were also common variations in channel width varied substantially among the analysed rivers which featured narrowing slightly prevailing and widening the least common as well as many cases of very limited changes channel width variations appear statistically although weakly related to some morphometric variables and significant differences emerge comparing glaciated vs unglaciated basins climate related variations glacier dynamics and channel disturbance frequency are argued to be the dominant factors that affected channel variations

floral and solution patterns of coccoliths in surface sediments of the north pacific coccolith assemblages from core top samples of the north pacific seafloor follow the distribution of surface water masses gephyrocapsa caribbeanica umbellosphaera tenuis and coccolithus pelagicus are the most important identifiers of surface water mass different multivariate statistical techniques group shallow samples in somewhat different spatial patterns factor analysis condenses the information contained in sixteen ies percentages to four new variables that can be interpreted as species assemblages by canonical correlation analysis these assemblages can in turn be related to the environment the first canonical correlation indicates that factor 2 the g caribbeanica assemblage is represented in samples underlying cooler surface water a second possible correlation describes a direct relationship between factor 3 the umbilicosphaera sibogae assemblage and the remaining environmental variable surface water salinity factor 1 the g oceanica assemblage and factor 4 the emiliania huxleyi assemblage are not as closely related to the selected environmental measures of temperature salinity dissolved oxygen and inorganic phosphate phosphorus as are factor 2 and factor 3 because samples were coded according to their overlying water mass group separations produced by discriminant analysis are easily interpreted in terms of the environment overlap of group assignments occurs for samples from the south china sea and extreme western pacific even partially dissolved samples retain the signature of surface water mass group assignment for those samples is generally reliable with the exception of samples from the central water mass where almost half of the shallow and half of the deep samples show strongest affinities with one of the other three water masses selective solution therefore only partially obscures the record of floral provinciality partial dissolution of coccolith assemblages does not proceed according to one systematic rank order the sequence of species removal is variable from region to region the more abundant species tend to consistently appear at an extreme of the ranking for example umbilicosphaera sibogae is among the least resistant and c leptoporus and g oceanica are among the most resistant species maximum depths of coccolith lysocline and compensation depth occur generally in the central part of the basin and shoal towards its margins as previously observed for planktonic foraminifera

glacier changes in the austrian alps during the last three decades derived from the new austrian glacier inventory beginning in 1996 aerial photographs were taken for a new austrian glacier inventory resulting in digital elevation models dems and digital orthoimages an earlier inventory of the austrian glaciers containing the original aerial photographs and glacier maps and a manual evaluation of various glacier parameters as of 1969 has been re evaluated at the present state of the art the two inventories provide the basis for the comparison of glacier reactions over a period of 29 years in general a reduction of glacier area is observed for almost all austrian glaciers between 1969 and 1998 the overall reduction in ice covered area is 17 the glacier volume change calculated from the dems amounts to about 5 km 3 this is almost 22 of the ice volume in austria in 1969 estimated from a volume area relation changes of individual glaciers however show a wide variability depending on their size and physiographic setting

nannoplankton productivity and diagenesis in the rhythmically bedded toarcian aalenian fiuminata section umbria marche apennine central italy abstract pelagic rhythmic lithotypes crop out in the fiuminata section central italy middle toarcian aalenian in age and provide a good example of cyclic sedimentation within the calcari e marne a posidonia unit the whole succession is made up of a nutty yellowish rhythmic sequence of marlstone and marly limestone beds with similar thicknesses calcareous nannofossil quantitative analyses give a good biostratigraphic resolution of the studied interval and also reveal a different assemblage composition of the carbonate rich lithotypes with respect to the carbonate poor ones schizosphaerella spp which is the dominant taxon in the assemblage shows higher abundances in the limestones conversely coccoliths are more abundant and diverse in the marls such data emphasize a relationship between palaeoenvironmental conditions in the water column nannoplankton productivity and the depositional pattern of the sedimentary basin diagenetic overprint can also account for the different assemblage composition in marlstones and limestones the effects of diagenesis on the original thanatocoenosis have been detected through a detailed analysis of nannofossil preservation this study points out that diagenesis has enhanced without obliterating a primary palaeoenvironmental signal nannoplankton productivity varied in response to differing conditions in the water column schizosphaerella spp seems to be more productive concomitant with the deposition of carbonate rich sediments with bioturbation and abundant radiolarians probably while these sediments were deposited a more vigorous vertical mixing of the water column occurred and trophic resources were good a stable and diversified community of coccolithophorids was established in times of clay deposition when the surface waters were stratified due to their density and nutrients were available both at the sea bottom and in the water column due to the runoff the differing nannoplankton assemblage is tentatively interpreted in terms of a response to milankovitch orbital climatic cycles

the middle cenomanian event in the equatorial atlantic the calcareous nannofossil and benthic foraminiferal response abstract in addition to oceanic anoxic event 2 oae2 other perturbations of the carbon cycle occurred during the cenomanian and turonian of which the middle cenomanian event mce is the most prominent one in palaeoecological publications however this event is strongly underrepresented in contrast to the well studied oae2 in order to fill this gap we have studied early cenomanian to late turonian calcareous nannofossil and benthic foraminiferal assemblages of ocean drilling program site 1260 at demerara rise western equatorial north atlantic in order to decipher biotic changes throughout this interval and especially across the mce our data show distinctive changes in the relative abundance of certain calcareous nannofossil taxa and a drastic decrease in benthic foraminiferal diversities and abundances associated with the mce in the lower part of the studied section and prior to the mce a mixed water column with high nutrient availability in the upper photic zone is suggested based on very high relative abundances of the mesotrophic eutrophic nannofossil species biscutum constans around the mce interval certain nannofossil taxa e g rhagodiscus asper show a distinctive decrease in relative abundance while others become more dominant taxa which increase in relative abundance after the mce e g eprolithus floralis are interpreted as either having favoured less eutrophic surface waters or having inhabited deeper parts of the photic zone in a well stratified water column this interpretation is supported by published oxygen isotope and tex86 data which suggest increased water column stratification starting with the mce and lasting to the end of the cenomanian stage as a result of the implementation of a saline intermediate to deep water mass during this interval our study shows that the mce was a significant biotic event in the cenomanian turonian equatorial atlantic characterised by a lasting change of surface and bottom water ecosystems

phytoplankton response and geochemical evidence of the lower toarcian relative sea level rise in the umbria marche basin central italy abstract quantitative and qualitative analyses have been carried out on the lower toarcian organic rich lithologies of the umbria marche domain marne di monte serrone formation with the aim to emphasize the potential of organic and geochemical parameters as palaeoenvironmental indices the organic matter and phytoplankton data suggest that the palaeoenvironmental evolution of this area was controlled by a third order cyclicity induced by climatic eustatic fluctuations during the early toarcian sea level rise two different phases have been recognized the phase of facies retrogradation referable to the transgressive system tract lying in the early and middle part of the d tenuicostatum zone this phase was characterized by a relative increase of basinal caco 3 a better fertility within the photic zone and a decrease of sea bottom oxygenation and of the micronutrients in surface waters the maximum flooding event at the top of the retrogradation phase corresponds with the maximum of palaeoenvironmental distality sedimentary starvation and total organic carbon toc values the phase of facies progradation corresponding to the high stand system tract occurred in the uppermost portion of the d tenuicostatum zone this phase induced a more efficient water circulation producing a re oxygenation at the sea bottom a better nutrient recycling and a reflourishing of nannoplakton the caco 3 in the basin was mainly extrabasinal because the carbonate platforms started producing and exporting the carbonate mud basinwards again this approach confirms that eustatic fluctuations strongly influenced the variations of phytoplankton total abundance and species diversity and the distribution of organic matter in the sediments it also regards a significant tool for the investigation of lithologies where the lack of significant sedimentary structures does not give detailed palaeoenvironmental information

an inventory and morphometric analysis of british columbia glaciers canada we describe an automated method to generate an inventory of glaciers and glacier morphometry from a digital topographic database containing glacier boundaries and a digital elevation model for british columbia canada the inventory contains over 12 000 glaciers with a total cumulative area that exceeds 25 000 km 2 based on mapping from aerial photographs circa the mid 1980s we use the inventory to examine dimensional characteristics among glaciers namely the scaling relations between glacier length width and area glacier length is a good predictor of glacier area and its predictive ability improves when glaciers are stratified by the number of up valley accumulation basins the spatial pattern of glacier mid range altitude parallels glaciation limits previously mapped for british columbia and similarly reflects large scale controls of orographic precipitation and continentality the inventory is also used to refine models that relate glacier mid range and terminus altitudes to regional position aspect and in the case of terminus altitudes an index of glacier shape relations between glacier altitude limits and controlling spatial and topographic factors are used to make further climatic and mass balance inferences from the glacier inventory