a chronology of holocene and little ice age glacier culminations of the steingletscher central alps switzerland based on high sensitivity beryllium 10 moraine dating abstract the amplitude and timing of past glacier culminations are sensitive recorders of key climate events on a regional scale precisely dating young moraines using cosmogenic nuclides to investigate holocene glacier chronologies has proven challenging but progress in the high sensitivity 10 be technique has recently been shown to enable the precise dating of moraines as young as a few hundred years in this study we use 10 be moraine dating to reconstruct culminations of the steingletscher a small mountain glacier in the central swiss alps throughout the holocene the outermost recorded positions of steingletscher most likely occurred in the early holocene and appear nearly synchronous with glacier culminations reported from other regions in the alps a late holocene position corroborates the evidence for a significant glacier advance of similar extent to that of the little ice age lia 3 kyr ago finally fourteen boulders from different moraines yield 10 be ages between 580 and 140 years with analytical precisions mostly 10 dating steingletscher advances during the lia because these lia 10 be ages are in stratigraphic order we tentatively distinguish four lia glacier culminations about 1470 ce 1650 ce 1750 ce and 1820 ce which are in good agreement with existing independent records during the lia in the swiss alps these findings illustrate the high potential of the 10 be moraine dating method to directly link paleo glacier chronologies to historical records and thus present day glacier evolution

recent glacier decline in the kerguelen islands 49 s 69 e derived from modeling field observations and satellite data the retreat of glaciers in the kerguelen islands 49 s 69 e and their associated climatic causes have been analyzed using field data and moderate resolution imaging spectroradiometer modis satellite images to validate a positive degree day pdd model forced by data from local meteorological stations mass balance measurements made during recent field campaigns on the largest glacier of the cook ice cap were compared to data from the early 1970s providing a 40 year view of the differences in the spatial distribution of surface mass balance smb to obtain additional regional data for the validation of our models we analyzed modis images 2000 2012 to determine if our model was capable of reproducing variations in the transient snow line the pdd model correctly simulated the variations in the snow line the spatial variations in the smb and its trend with elevation yet current smb values diverge from their classic linear representation with elevation and stake data at high altitudes now display more negative smb values than expected by analyzing modis albedo we observed that these values are caused by the disappearance of snow and associated feedback on melt rates in addition certain parts of ampere glacier could not be reproduced by the surface energy balance model because of overaccumulation due to wind deposition finally the modis data field data and our models suggest that the acceleration of glacier wastage in kerguelen is due to reduced net accumulation and an associated rise in the snow line since the 1970s

glacier advance in southern middle latitudes during the antarctic cold reversal the geographic extent of cooling associated with the antarctic cold reversal is unclear dating of glacial moraines in new zealand suggests that the cooling extended into the southern mid latitudes possibly as a result of the northward migration of the southern subtropical front

driving mechanism of tectonic activity in the northern apennines quantitative insights from numerical modeling 1 it is shown by numerical modeling that the recent deformation pattern observed in the northern apennines mainly characterized by progressive eastward migration and bowing of the belt thrusting activity along its external front and tensional tectonics in the internal area can be reproduced at a first approximation by applying a belt parallel se nw compression to the chain which is simulated as a structural system characterized by a high mechanical strength and decoupled from the surrounding zones the above compressional regime obtained by imposing kinematic boundary conditions to the model causes the outward escape of crustal wedges from the chain in particular the northeastward displacement of the romagna marche umbria units and the counterclockwise rotation and northwestward displacement of the ligurian units this kinematics produces compressional to transcompressional strain along the external front of the chain and tensional to transtensional strain in the internal area in line with the observed features that concern both strain style and orientation of principal strains evidence and arguments supporting the kinematic boundary conditions and the model parameterization adopted in modeling are discussed numerical experiments have also been carried out to evaluate the influence of major features of the model parameterization and boundary conditions we have adopted in modeling and to provide insights into the possible influence of strong decoupling earthquakes in the central apennines on tectonic and seismic activity in the northern apennines

geochemistry of interstitial gases in quaternary sediments of the gulf of california abstract interstitial gases from the deep sea drilling project dsdp ipod leg 64 sites 474 477 479 and 481 in the gulf of california have been analyzed by gas chromatography and stable isotope mass spectrometry in order to evaluate their compositions in terms of biogenic and thermogenic sources the hydrocarbon gas c 1 c 5 concentrations were comparable to the shipboard data and no olefins could be detected the 13 c data for the ch 4 confirmed the effects of the thermal stress on the sedimentary organic matter in that the values were typically biogenic near the surface and become more depleted in 12 c vs depth at sites 474 478 and 481 the ch 4 at site 477 was the heaviest in 13 c and at site 479 it did not show a predominant high termperature component the co 2 at depth from most sites was of a primarily thermogenic origin from carbonate decomposition

helium and carbon isotope systematics of natural gases from taranaki basin new zealand abstract the chemical and isotopic compositions of gases from hydrocarbon systems of the taranaki basin of new zealand both offshore and onshore show wide variation the most striking difference between the western and south eastern groups of gases is the helium content and its isotopic ratio in the west the maui gas is over an order of magnitude higher in helium concentration up to 190 mol mol 1 and its 3he 4he ratio of 3 8 ra where ra the air 3he 4he ratio of 1 4 10 6 is approximately half that of upper mantle helium issuing from volcanic vents of the taupo volcanic zone in the se the kupe south and most kapuni natural gases have only a minor mantle helium input of 0 03 0 32 ra and low total helium concentrations of 10 19 mol mol 1 the 3he c ratio where c represents the total carbon in the gas phase of the samples measured including those from a recent study of on shore taranaki natural gases are generally high at locations where the surface heat flow is high the 3he co2 ratio of the maui gases of 5 to 18 10 9 is higher than the morb value of 0 2 to 0 5 10 9 a feature found in other continental basins such as the pannonian and vienna basins and in many high helium wells in the usa extrapolation to zero co2 3he and co2 c indicates 13c co2 values between 7 and 5 close to that of morb co2 the remaining co2 would appear to be mostly organically influenced with 13c co2 c 15 there is some evidence of marine carbonate co2 in the gases from the new plymouth field the radiogenic 4he content herad varies across the taranaki basin with the highest herad c ratios occurring in the maui field 13c ch4 becomes more enriched in 13c with increasing herad and hydrocarbon maturity because 3he 4he is related to the ratio of mantle to radiogenic crustal helium and 3he c is virtually constant in the maui field there is a correlation between rc ra where rc air corrected 3he 4he and 13c ch4 in the maui and new plymouth fields with the more negative 13c ch4 values corresponding to high 3he 4he ratios a correlation between 3he 4he and 13c co2 was also observed in the maui field in the fields adjacent to mt taranaki 2518 m andesitic volcano correlations of some parameters particularly co2 ch4 c2h6 ch4 and 13c ch4 are present with increasing depth of the gas reservoir and with distance from the volcanic cone

light hydrocarbon gases in guaymas basin hydrothermal fluids thermogenic versus abiogenic origin light hydrocarbon gases methane through pentane in high temperature hydrothermal fluids of the guaymas basin gulf of california are predominantly derived from thermocatalysis of organic carbon in sediments intruded by mid ocean ridge volcanic rocks the spectrum of c1 c5 gases in guaymas basin hydrothermal fluids is characterized by a preponderance of alkanes with essentially no alkenes present comparison with high temperature fluids from 21 n on the east pacific rise where geochemical evidence indicates a distinct lack of thermogenic gas and where methane is derived abiogenically from the basalts shows that the 21 n hydrocarbon gases are characterized by a prominent ethylene signature stable isotope compositions of guaymas basin m thane differ from 21 n gas guaymas basin has dgr13c values of 43 to 51 pmil vs pdb compared to 21 n where values as high as 15 pmil have been measured these differences reflect the different origins of light hydrocarbon gases in the two systems with guaymas methane being overwhelmingly of an organic thermogenic derivation and showing no evidence of the abiogenic basalt derived gas that characterizes the 21 n environment carbon isotope analyses of dissolved inorganic carbon in guaymas basin hydrothermal fluids indicate that high temperature hydrocarbon oxidation may be an important process acting in conjunction with high temperature thermocatalytic hydrocarbon generation

carbon isotope geochemistry of natural gases from the green tuff basin japan carbon isotopic analyses of c1 c4 hydrocarbons were carried out to investigate the origin and formation mechanism of natural gases commercially produced from volcanic rocks as well as sedimentary rocks in the green tuff basin of northeast japan whose high 3he 4he ratios have suggested a possible magmatic origin 13c pdb values of methane ethane propane and n butane range from 54 4 to 33 3 from 32 5 to 20 9v from 27 7 to 20 6 and from 25 3 to 20 5 respectively all of which fall within the ranges of published data of worldwide gases of biogenie origin most samples show the isotope distribution pattern wherein the 13c values become less negative with increasing molecular weight of the hydrocarbons suggesting that the c2 hydrocarbons were not derived by methane polymerization the 13c values of c2 c4 hydrocarbons are explained by thermogenic breakdown of organic matter whereas the 13c values of methane are more or less lower than those expected from the same origin these results indicate that the gases from the green tuff basin consist of thermogenic hydrocarbons plus variable amounts of isotopically lighter microbial methane significant contributions of abiogenic methane which would be isotopically heavier than the thermogenic methane are not plausible for the gases

helium transport in sediment pore fluids of the congo angola margin during the zairov2 cruise of the zaiango project 1998 2000 on the passive congo angola margin several gravity cores were analyzed for helium isotopic composition of sedimentary pore waters in two cold fluid seepage zones the astrid slide area and the regab giant pockmark gas concentration and isotopic composition are presented along with thermal data in terms of the origin and circulation of fluids helium isotope data lie on a mixing line between bottom seawater and an almost pure radiogenic helium and temperature vertical profiles are well described by the classic diffusionadvection equation on the basis of he profiles we estimate the advection rate on the rim of the pockmark between 1 2 and 2 3 mm a the he flux derived for a pure diffusive regime 2 4 10 8 mol m 2 a can favorably be compared to literature data and contrasts with the flux computed close to the pockmark center 1 9 10 7 mol m 2 a helium depth profiles turned to be more sensitive to advection rate than temperature profiles are

holocene glacier fluctuations a global overview of glacier advances and retreats grouped by regions and by millennia for the holocene is compiled from previous studies the reconstructions of glacier fluctuations are based on 1 mapping and dating moraines defined by 14 c tcn osl lichenometry and tree rings discontinuous records time series and 2 sediments from proglacial lakes and speleothems continuous records time series using 189 continuous and discontinuous time series the long term trends and centennial fluctuations of glaciers were compared to trends in the recession of northern and mountain tree lines and with orbital solar and volcanic studies to examine the likely forcing factors that drove the changes recorded a general trend of increasing glacier size from the earlyemid holocene to the late holocene in the extra tropical areas of the northern hemisphere nh is related to overall summer temperature forced by orbitally controlled insolation the glaciers in new zealand and in the tropical andes also appear to follow the orbital trend i e they were decreasing from the early holocene to the present in contrast glacier fluctuations in some monsoonal areas of asia and southern south america generally did not follow the orbital trends but fluctuated at a higher frequency possibly triggered by distinct teleconnections patterns during the neoglacial advances clustered at 4 4e4 2 ka 3 8e3 4 ka 3 3e2 8 ka 2 6 ka 2 3e2 1 ka 1 5e1 4 ka 1 2e1 0 ka 0 7e0 5 ka corresponding to general cooling periods in the north atlantic some of these episodes coincide with multidecadal periods of low solar activity but it is unclear what mechanism might link small changes in irradiance to widespread glacier fluctuations explosive volcanism may have played a role in some periods of glacier advances such as around 1 7e1 6 ka coinciding with the taupo volcanic eruption at 232 5 ce but the record of explosive volcanism is poorly known through the holocene the compilation of ages suggests that there is no single mechanism driving glacier fluctuations on a global scale multidecadal variations of solar and volcanic activity supported by positive feedbacks in the climate system may have played a critical role in holocene glaciation but further research on such linkages is needed the rate and the global character of glacier retreat in the 20th through early 21st centuries appears unusual in the context of holocene glaciation though the retreating glaciers in most parts of the northern hemisphere are still larger today than they were in the early and or mid holocene the current retreat

helium and carbon geochemistry of hydrothermal fluids from the mid okinawa trough back arc basin southwest of japan abstract hydrothermal systems located in the okinawa trough back arc basin are considered to be related to rifting activities in the continental margin hydrothermal fluids sampled from two sites jade and clam are significantly enriched in gas species compared to those from mid oceanic ridges a high temperature fluid 320 c from the jade site shows a co 2 concentration of 200 mmol kg 1 which is more than one order of magnitude higher than that of sediment starved ridge crest hydrothermal systems both helium r r a 6 1 6 5 and carbon 13 c co2 5 0 to 4 7 pdb isotopic compositions are typical of island arc magmatic gases also the abundance ratio of co 2 3 he 3 10 10 is within the range of values found in island arcs chemical and isotopic composition of the jade fluid are considered to indicate that both co 2 and helium are derived from a magmatic source beneath the hydrothermal system without significant contamination contrary to these species ch 4 is attributed to a thermogenic origin based on its isotopic composition 13 c ch 4 41 to 36 pdb and high concentration 7 1 mmol kg 1 which values are similar to those observed in sediment hosted hydrothermal systems the clam fluids show gas geochemistry much more affected by fluid sediment interaction lower 3 he 4 he ratios r r a 3 7 3 8 and higher co 2 3 he ratios 10 11 may reflect involvement of gas species introduced during secondary fluid circulation within the sedimentary pile magmatic activity is the main contributor of gas species to the hydrothermal fluids in both the jade and clam sites although fluid sediment interaction modifies their composition the relatively high abundance of co 2 in the mid okinawa trough hydrothermal systems reflects the geochemical nature of island arc magma

origin of methane rich natural gas in japan formation of gas fields due to large scale submarine volcanism eighty seven samples of ch4 rich natural gas were collected from commercial gas and oil wells in japan the3he 4he and4he 20ne ratios chemical composition of major minor and trace components ch4 c2h6 c3h8 co2 n2 o2 ar he ne and h2 and the c isotope composition of ch4 are reported most3he 4he ratios of natural gases in the forearc regions are as low as 1 4 10 7 and are comparable to those from large gas reservoirs in other parts of the world suggesting that the ch4 has a biogenic origin in contrast the3he 4he ratios of samples from gas reservoirs in the green tuff region along the japan sea vary considerably high ratios are observed for gases from volcaniclastic reservoirs in the deeper zone and low ratios are found in shallow reservoirs of sedimentary rocks the highest3he 4he ratio 9 37 0 34 10 6 is equivalent to the highest value in the subduction zone the high4he 20ne ratios observed in most samples suggest that there is no significant atmospheric contamination an overall regularity between3he 4he ratios and 13cch4 values is observed for japanese natural gases the 13cch4 value of gas with a high3he 4he ratio reaches about 35 and that of gas with a low ratio is about 75 total c to3he ratios c 3he vary over a wide range 6 108 9 1012 but those of gases in volcaniclastic reservoirs are in a rather narrow range with a value of 2 109 coinciding with that of a mantle reservoir the relation between the observed3he 4he ratios and 13cch4 values of gases together with their c 3he ratios suggests that ch4 rich gases in volcaniclastic reservoirs are a mixture of gases from two sources magmatic and biogenic the formation of gas reservoirs with high3he 4he ratios may be attributed to large scale submarine volcanism that occurred in the middle miocene gas separation from volcaniclastic rocks is expected to have occurred during the process of sea water rock interaction at a high temperature over a long period in a submarine environment the middle miocene volcanic episode which occurred under extensional stress was quite different from the present arc volcanism and is thought to have been closely related to the opening of the japan sea

magmatic helium in subduction zone natural gases abstract he isotope ratios provide important constraints on the input of magmatic gases into crustal systems natural gas associated with active continental margins from taiwan r o c new zealand the philippines indonesia thailand and alaska u s a contain a magmatic he component based on measured 3 he 4 he ratios r ranging from 0 5 to 3 8 times the atmospheric value ra the methane helium results can be interpreted as the result of a mixture between a low 3 he 4 he 0 01r a high ch 4 3 he crustal end member and a high 3 he 4 he 0 6 3 9r a low ch 4 3 he 6 magmatic component the presence of mantle he does not require significant amounts of mantle methane a better fit to the data is obtained using a zero methane magmatic end member the worldwide association of 3he and magmatic activity suggests that volcanism plays a role in methane generation by supplying the heat needed to convert organic matter to methane thermogenically only gases from the accretionary prism of barbados west indies appear totally devoid of magmatic he 3 he 4 he ratio 0 02ra the he is completely of crustal origin there is no evidence that faults within the accretionary prism of this fore arc act as conduits for the migration of mantle he many of the gases studied contain significant quantities of co2 which appear to result from two processes 3 he 4 he high co 2 3 he gases 0 01ra 1011 possibly result from decarbonation reactions in the crust while the high 3 he 4 he low co 2 3 he gases 2 4ra

calibration of cosmogenic 36cl production rates from ca and k spallation in lava flows from mt etna 38 n italy and payun matru 36 s argentina abstract published cosmogenic 36cl production rates from ca and k spallation differ by almost a factor of 2 in this paper we determine production rates of 36cl from ca and k in samples of known age containing little cl ca rich plagioclases and k feldspars were separated from a total of 13 samples collected on the surfaces of four basaltic lava flows at mt etna 38 n italy and from a trachyte lava flow at payun matru volcano 36 s argentina eruption ages determined by independent methods range between 0 4 and 32 ka sample site elevations range between 500 and 2500 m corresponding scaling factors were calculated using five different published scaling models four of which consider paleo geomagnetic field variations integrated over the exposure durations the resulting five data sets were then analyzed using a bayesian statistical model that incorporates the major inherent uncertainties in a consistent way spallation production rates from ca and k considering all major uncertainties are 42 2 4 8 atoms 36cl g ca 1 a 1 and 124 9 8 1 atoms 36cl g k 1 a 1 normalized to sea level and high latitude using the scaling method of stone 2000 scaling models that account for paleo geomagnetic intensity changes yield very similar mean values at most 4 if the uncertainties in the independent ages are neglected in the bayesian model the calculated element specific production rates would be about 12 higher our results are in agreement with previous production rate estimations both for ca and k if only low cl i e 20 ppm samples are considered

dynamics of former ice lobes of the southernmost patagonian ice sheet based on a glacial landsystems approach reconstructions of former ice masses from glacial geomorphology help to constrain the nature and timing of glaciation in relation to climatic forcing this paper presents a new reconstruction of the glacial history of five ice lobes in southernmost south america the bahia inutil san sebastian magellan otway skyring and rio gallegos ice lobes we use previous geomorphological mapping of glacial landforms to reconstruct former glacial limits and proglacial lakes demarcate flow sets from the distribution of glacial lineations and evaluate glacial landsystem signatures and their palaeoglaciological implications evidence suggests that the ice lobes predominantly reflect active temperate glacial landsystems which may have switched to polythermal systems when periods of cold based ice developed ephemerally this complex landsystem signature implies that the ice lobes were sensitive to regional climate variability with active re advances during overall retreat of the ice margins there is also evidence for periods of fast ice flow and possible surge like activity in the region followed by the rapid retreat or even collapse of some of the ice lobes in association with proglacial lakes constraining our new reconstruction with published chronological information suggests that at least some of the ice lobes advanced before the global last glacial maximum glgm ca 26 5 19 ka during the last glacial cycle our new reconstruction demonstrates a more complex picture of ice dynamics than has previously been portrayed and one in which the advance and retreat of the ice lobes was likely to have been primarily driven by changes in climate as such ice advances before the glgm in the southernmost part of the patagonian ice sheet are likely to indicate a wider climatic forcing at this time

halide systematics in interstitial waters of ocean drilling sediment cores abstract the distribution of dissolved halides cl br i in interstitial waters of deep drill holes in the ocean is discussed for a number of environments hemi pelagic sediments hydrate containing sediments sediments affected by halide brines and also in hydrothermal environments the importance of the diagenesis of organic c in the production of i and br is discussed with reference to the observations of dissolved so 4 2 and nh 4 in the pore fluids more importantly in the zone of methano genesis below the so 4 2 reduction zone and usually associated with high organic c accumulation rates increases in i and br are of importance and usually are much higher than the increases observed in the so 4 2 reduction zone in pore fluids affected by dissolution of evaporites the br cl is often a strong indicator of the degree of evaporation of seawater demonstrated from results obtained in the mediterranean sea dissolution of halites on the other hand leads to br cl much lower than those of sea water in hydrothermal sediments there is no doubt that i and br contents of the fluids are influenced by hydrothermal alteration of the sediments and their organic c but signals are not clear the present study provides an overview of previous dsdp and odp studies of halide distributions in sedimentary pore waters in addition to other contributions on halide distributions in sedimentary pore waters in this symposium volume

in situ cosmogenic 10be production rate at lago argentino patagonia implications for late glacial climate chronology abstract when calculated with the commonly accepted average northern hemisphere production rate 10 be dates of surface boulders on moraines in the lago argentino area of patagonia are younger than minimum limiting 14 c ages for the same landforms this disagreement could result from the lack of a regional 10 be production rate calibration site to assess this possibility we here present high precision measurements of 10 be in samples collected from surface boulders on the herminita and puerto bandera moraine complexes deposited alongside lago argentino on the eastern flank of the andes at 50 s in patagonia together with maximum and minimum limiting 14 c ages for the two moraine systems these measurements confine the local 10 be production rate to between 3 60 and 3 82 atoms g yr midpoint 3 71 0 11 atoms g yr when using a time dependent scaling method that incorporates a high resolution geomagnetic model this range includes upper and lower error bounds of acceptable production rates derived from both the herminita and the puerto bandera sites the upper limit of this range is more than 12 below the average northern hemisphere production rate as calculated using the same scaling method given in balco et al quat geochron 3 2008 174 195 other scaling models yield production rates with similarly large offsets from the balco et al 2008 rate on the other hand the range of acceptable production rate values determined from patagonia overlaps at 1 with and encompasses the production rate recently derived in macaulay valley in the southern alps of new zealand a putnam et al quat geochron 5 2010a 392 409 within uncertainties i e overlap at 1 sigma this patagonian production rate range also agrees with a recently determined production rate from low elevation sites in northeastern north america and northern norway when the macaulay production rate is used to calculate patagonian exposure dates 14 c and 10 be chronologies are mutually compatible for late glacial moraine systems both chronologies then indicate that outlet glaciers of the southern patagonian icefield achieved a late glacial maximum in the western reaches of lago argentino at 13 000 cal yr bp at the end of the antarctic cold reversal 14 500 12 900 cal yr bp outlet glaciers subsequently receded to near present day ice margins during the younger dryas stadial 12 900 11 700 cal yr bp this general retreat was interrupted about 12 200 cal yr bp when upsala glacier constructed an interlobate complex of moraine ridges on herminita peninsula mountain glaciers in patagonia and new zealand on both sides of the south pacific ocean exhibited a coherent pattern of late glacial ice margin fluctuations

detailed seismic stratigraphy of lago puyehue implications for the mode and timing of glacier retreat in the chilean lake district lago puyehue is a glacigenic lake in the chilean lake district 40 s with a complex deglaciation history a detailed seismic stratigraphic study of its sedimentary infill indicates a much earlier retreat of the glacier from the lago puyehue basin than the neighbouring glacier from the lago rupanco basin because of their close proximity rupanco meltwater streams played an important part in the depositional processes of lago puyehue a timing discrepancy between the in lake ages of a sediment core and the outer lake ages of moraine deposits re opens the discussion on the timing of deglaciation in the southern hemisphere copyright 2011 john wiley sons ltd

the chronology of the last glacial maximum and deglacial events in central argentine patagonia this paper evaluates the chronology of the last glacial cycle and deglaciation in the lago pueyrredon valley of central patagonia 47 5 s argentina the valley was a major outlet of the former patagonian ice sheet and the moraines that record its fluctuations are an important proxy record of climate change in southern south america such moraines are well preserved in the lago pueyrredon valley owing in part to the semi arid environment east of the mountain front here we provide the first direct chronology for the age of the rio blanco moraine system by utilizing cosmogenic nuclide surface exposure ages boulders on the moraines give 10be exposure ages that indicate the last glacial maximum lgm maximum extent occurred by 27 25 ka subsequent advances occurred at 23 22 ka 20 18 ka and ca 18 17 ka initial deglaciation began after ca 18 17 ka and was interrupted as evidenced by the lago columna moraines up valley subsequently the outlet glaciers occupying both the lago pueyrredon basin chilean name lago cochrane and the lago buenos aires basin chilean name lago general carrera to the north rapidly retreated more than 80 km at around 16 5 15 ka the timing of the lgm maximum extent and the onset of deglaciation occurred broadly synchronously throughout patagonia deglaciation resulted in a series of interconnected glacier dammed lakes in the region that initially drained toward the atlantic ocean and later drained to the pacific ocean as a consequence of disintegrating ice in the andes

evidence in favour of an extensive ice cover on sub antarctic kerguelen island during the last glacial abstract arguments to date have suggested that during the last glacial wurm wisconsin weichselian sub antarctic kerguelen island did not experience an extensive ice cover and that the fjords and glacial valleys are products of earlier events recent observations of striation orientations travel directions of erratics cirque altitudes and evidence for isostatic uplift suggest that there in fact may have been extensive ice cover the equilibrium line altitude e l a reconstructed for the cirque glacier stage agrees well with that for sub antarctic marion island situated to the west a possible explanation for the lack of glacial deposits and landforms over much of the island is suggested

annular modes in the extratropical circulation part i month to month variability the leading modes of variability of the extratropical circulation in both hemispheres are characterized by deep zonally symmetric or annular structures with geopotential height perturbations of opposing signs in the polar cap region and in the surrounding zonal ring centered near 458 latitude the structure and dynamics of the southern hemisphere sh annular mode have been extensively documented whereas the existence of a northern hemisphere nh mode herein referred to as the arctic oscillation ao has only recently been recognized like the sh mode the ao can be defined as the leading empirical orthogonal function of the sea level pressure field or of the zonally symmetric geopotential height or zonal wind fields in this paper the structure and seasonality of the nh and sh modes are compared based on data from the national centers for environmental prediction national center for atmospheric research reanalysis and supplementary datasets the structures of the nh and sh annular modes are shown to be remarkably similar not only in the zonally averaged geopotential height and zonal wind fields but in the mean meridional circulations as well both exist year round in the troposphere but they amplify with height upward into the stratosphere during those seasons in which the strength of the zonal flow is conducive to strong planetary wave mean flow interaction midwinter in the nh and late spring in the sh during these active seasons the annular modes modulate the strength of the lagrangian mean circulation in the lower stratosphere total column ozone and tropopause height over mid and high latitudes and the strength of the trade winds of their respective hemispheres the nh mode also contains an embedded planetary wave signature with expressions in surface air temperature precipitation total column ozone and tropopause height it is argued that the horizontal temperature advection by the perturbed zonal mean zonal wind field in the lower troposphere is instrumental in forcing this pattern a companion paper documents the striking resemblance between the structure of the annular modes and observed climate trends over the past few decades

the victor hensen seahill central ionian sea morphology and structural aspects abstract a seabeam based bathymetric map from the victor hensen seahill is presented 3 5 khz sonar profiles show the structural relations of the near surface sedimentary sequences of the surrounding abyssal plain and between abyssal plain and seahill the structures are interpreted to be caused by tensional tectonics acting up to the present

a thick holocene homogenite from the ionian abyssal plain eastern mediterranean abstract a homogenite layer thicker than 12 m holocene in age occurs in the ionian abyssal plain the graded sandy base is 1 3 m thick most of the layer is structureless and homogeneous in grain size and mineral composition the most remarkable components are siltsized grains composed of aragonite needles they are interpreted as skeleton fragments of the green alga halimeda sp the homogenite covers an area of at least 1100 km 2 and assuming a minimum thickness of 10 m comprises a volume of 11 km 3 the source of the material of the homogenite is a matter of speculation very likely it has been remobilized from different areas around the ionian abyssal plain as triggering event a tsunami generated by the collapse of the santorini caldera about 3500 yrs b p is assumed

high frequency holocene glacier fluctuations in new zealand differ from the northern signature understanding the timings of interhemispheric climate changes during the holocene along with their causes remains a major problem of climate science here we present a high resolution 10be chronology of glacier fluctuations in new zealand s southern alps over the past 7000 years including at least five events during the last millennium the extents of glacier advances decreased from the middle to the late holocene in contrast with the northern hemisphere pattern several glacier advances occurred in new zealand during classic northern warm periods these findings point to the importance of regional driving and or amplifying mechanisms we suggest that atmospheric circulation changes in the southwest pacific were one important factor in forcing high frequency holocene glacier fluctuations in new zealand

southern patagonian glacial chronology for the last glacial period and implications for southern ocean climate the magellan region of southern south america is in a unique setting at 50 s on the equatorial side of the antarctic frontal zone to record in detail terrestrial glacial to interglacial events a 10be chronology shows growth and millennial fluctuations of a patagonian ice sheet between 25 and 17 6 17 0 cal ka in the strait of magellan the maximum ice margin position is dated to 24 6 0 9 ka and other moraine ages are 18 5 1 8 and 17 6 0 2 ka mean 1 standard deviation in bahia inutil dated moraine ages are 20 4 1 2 and 17 3 0 8 ka the chronology of the local last glacial maximum lgm reveals a record of atmospheric cooling that was broadly in phase with changes in southern ocean conditions such as sea ice fluctuations and surface water characteristics published modeling results indicate that a decline in temperature of 6 c and slight drying over southernmost patagonia could simulate the growth and sustained presence of an ice sheet to the mapped lgm limit the terrestrial record in southern patagonia and marine records in adjacent oceans indicate mean northward movement of the antarctic frontal zone which caused the last southern south american ice age the antarctic frontal zone at present lies only 3 5 to the south some significant changes in the magellan region occurred in step with north atlantic region and the northern hemisphere for example the overall time span of the last glaciation and the timing of maximum ice extent were similar between the hemispheres despite maximum local summer insolation intensity in southern south america other characteristics of the southern patagonian glacial history differ from the north atlantic region specifically an out of phase relationship during deglaciation which is more similar to that of southern ocean and antarctic records

glacial geomorphology and chronology of deglaciation south georgia sub antarctic we mapped and dated the glacial geomorphology of north east south georgia in the maritime sub antarctic the aim was to examine the timing of deglaciation of the island in the context of inter hemispheric phasing of climate change former glacier limits are restricted to the inner fjords and our detailed mapping of them has demonstrated a consistent geomorphological pattern that is similar across several different glacier types and sizes the pattern comprises three suites of moraines categories a c not all of which are represented at every site because the outer suite is often overridden by younger suites category a is an outer wide low amplitude moraine ridge category b comprises 2 4 sharp crested bouldery moraines that are often located close to or even over riding a and category c is a series of lower amplitude moraines with overprinted streamlined landforms such as flutings analysis of in situ cosmogenic 10be in boulders on these moraines has allowed us to determine a deglacial chronology for the older two moraine groups the age of the inner youngest group has been estimated from soil development the cosmogenic nuclide ages show that the outermost moraine was deposited ca 12 2 1 5 ka bp but that a subsequent readvance in the mid holocene ca 3 6 1 1 ka bp reached and in places over rode this earlier moraine this latter advance coincides with the mid holocene hypsithermal a final late holocene advance reached closely similar limits to the previous two fluctuations and is estimated from soil data to have an age of ca 1 1 ka bp we suggest that the close concordance of late glacial and interglacial limits in this case associated with warming can be explained by a change in dominant forcing during glacials extensive sea ice limits precipitation availability and so glaciers are restricted to the inner fjords during interglacials precipitation is not limited in the same way by sea ice cover and so during warming precipitation increases and tidewater glaciers on the island have responded by advancing this study emphasises the importance of a clear understanding of geomorphology in order to interpret chronological information

glacial history of sub antarctic south georgia based on the submarine geomorphology of its fjords we present multibeam swath bathymetric surveys of the major fjords surrounding the sub antarctic island of south georgia to characterise the glacial geomorphology and to identify the relative timings and extent of past glacial advance and retreat bathymetry data revealed a range of glacial features including terminal retreat and truncated moraines deep distal outer and shallow proximal inner basins and cross shelf troughs these provide evidence of glacial advance and retreat through several glacial cycles a near consistent pattern of large scale submarine geomorphological features was observed in the different fjords suggesting a similar response of margins of the island ice cap to past climate forcing a relative chronology based on the relationships between the submarine features with their radiocarbon and cosmogenic isotope dated terrestrial counterparts suggests that widely observed inner basin moraines date from the last major glacial advance or last glacial maximum while deep basin moraines may date from an earlier pre lgm more extensive glaciation which we speculate corresponds to mis6 on the sides of the deep basins a series of truncated moraines show ice advance positions from preceding glacial periods the cross shelf troughs and mid trough moraines are interpreted as the product of much more extensive glaciations that predate the fjord geomorphology mapped here thus possibly older than mis6 this hypothesis would suggest that south georgia followed a glacial history similar to that of central patagonia 46 s where a series of pleistocene glaciations of mis 20 and younger extended beyond lgm limits with the most extensive glacial advance occurring at c 1 1 ma

glacier extent in sub antarctic kerguelen archipelago from mis 3 period evidence from 36cl dating documenting sub antarctic glacier variations during the local last glacial maximum is of major interest to better understand their sensitivity to atmospheric and oceanic temperature changes in conjunction with antarctic ice sheet changes however data are sparse because evidence of earlier glacier extents is for most sub antarctic islands located offshore making their observation complex here we present cosmogenic 36cl surface exposure ages obtained from five sites at kerguelen to document the glacial history the 36cl ages from roche moutonnee surfaces erratics and boulders collected on moraines span from 41 9 4 4 ka to 14 3 1 1 ka ice began to retreat on the eastern part of the main island before 41 4 4 4 ka slow deglaciation occurred from 41 to 29 ka there is no evidence of advances between 29 ka and the antarctic cold reversal acr period 14 5 12 9 ka period during the acr however the bontemps and possibly belvedere moraines were formed by the advance of a cook ice cap outlet glacier and a local glacier on the presque ile jeanne d arc respectively this glacier evolution differs partly from that of glaciers in new zealand and in patagonia these asynchronous glacier changes in the sub antarctic region are however in agreement with sea surface temperature changes recorded around antarctica which suggest differences in the climate evolution of the indo pacific and atlantic sectors of antarctica

hydrothermal geochemistry of sediments and pore waters in escanaba trough odp leg 169 geochemical studies of pore fluids and solid phases in two ocean drilling program odp drill sites sites 1037 and 1038 in the escanaba trough off northern california have provided further data on the hydrothermal processes associated with the spreading of the gorda ridge previous work in the area of odp site 1038 includes the discovery of a hydrothermal system and associated sulfide deposits centered around an uplifted sediment hill in this sedimented extensional environment this earlier work provided some insights into the present nature of venting however only deep drilling investigations can provide the means to fully understand the genesis and evolution of this system and associated hydrothermal deposits odp leg 169 is the third deep drilling operation to explore the magnitude genesis and evolution of hydrothermal systems on sedimented ridges previous studies centered on the guaymas basin in the gulf of california and the middle valley in the ne pacific ocean pore water studies in the reference odp site 1037 and in the hydrothermally active area of odp site 1038 have revealed the presence of a complex system of hydrothermally originated fluids whereas the data in the reference site indicate recent hydrothermal activity in the basal part of the drill site the evidence in site 1038 suggests that fluids of hydrothermal origin spread out at shallow depths around the central hill causing substantial sediment alteration as well as deposition of hydrothermal sulfides in the near surface zone of the sediments a second major discovery at site 1038 was the evidence for fluid phase separation at depth at temperatures possibly in excess of 400 c this conclusion is based on the presence of both low cl and high cl fluids the latter appear to be advected rapidly towards the surface presumably along cracks and faults the low cl fluids however appear to be transported laterally along sandy horizons in the sediments thus signifying two very different migration pathways for high cl and low cl hydrothermally phase separated fluids studies of the organic geochemistry of dissolved gases and matured organic matter corroborate these findings of extensive hydrothermal alteration of the sediments

the last termination in the south indian ocean a unique terrestrial record from kerguelen islands 49 s situated within the southern hemisphere westerly belt the awareness of the significance of the southern ocean in the earth s climate system has become increasingly obvious the deglacial atmospheric co2 rise during warming periods in antarctica has been attributed to co2 ventilation from the deep ocean caused by enhanced upwelling around the antarctic divergence it has been hypothesized that more intense southern hemisphere westerly winds aligned with the antarctic circumpolar current due to a southward shift of the wind belt from its last glacial maximum equator ward position are the main drivers reconstructions of past changes in atmospheric circulation in the southern hemisphere are still scarce and the overall picture is patchy with sometimes contradictory results for obvious reasons most terrestrial records originate from southern south america and new zealand here we present a terrestrial record from the indian sector of the southern ocean from kerguelen islands located at 49 s a peat record is investigated using a multi proxy approach pollen and plant macrofossils magnetic susceptibility xrf analyses biogenic silica content rock eval6 analysis and humification degree peat accumulation starts at about 16 000 cal yr bp with relatively warm and dry conditions the most prominent change in our proxy data occurs at 13 600 cal yr bp when peat ponds were established on the peat surface resulting in lacustrine type deposits as a result of very high humidity and with proxies implying very windy conditions within chronological uncertainties this onset coincides with the onset of the so called oceanic cold reversal based on the deuterium excess data in the epica dome c ice core record kerguelen islands are located in the moisture source area of dome c and a change in atmospheric circulation at that time could explain both records around 12 900 cal yr bp at the end of the antarctic cold reversal pond lake sediments give way to more peaty deposits with proxies suggesting slightly drier less windy and probably warmer conditions kerguelen islands became less influenced by the southern hemisphere westerly winds and these conditions were amplified during the early holocene climate optimum as found in antarctic ice core records

the last glacial maximum at 44 s documented by a 10be moraine chronology at lake ohau southern alps of new zealand abstract determining whether glaciers registered the classic last glacial maximum lgm 26 500 19 000 yrs ago coevally between the hemispheres can help to discriminate among hypothesized drivers of ice age climate here we present a record of glacier behavior from the southern alps of new zealand during the local lgm llgm we used 10 be surface exposure dating methods and detailed glacial geomorphologic mapping to produce a robust chronology of well preserved terminal moraines deposited during the llgm near lake ohau on central south island we then used a glaciological model to estimate a llgm glacier snowline and atmospheric temperature from the ohau glacier record seventy three 10 be surface exposure ages place culminations of terminal moraine construction and hence completions of glacier advances to positions outboard of present day lake ohau at 138 600 10 600 yrs 32 520 970 yrs ago 27 400 1300 yrs ago 22 510 660 yrs ago and 18 220 500 yrs ago recessional moraines document glacier recession into the lake ohau trough by 17 690 350 yrs ago exposure of an ice molded bedrock bench located inboard of the innermost llgm moraines by 17 380 510 yrs ago indicates that the ice tongue had receded about 40 of its overall length by that time comparing our chronology with distances of retreat suggests that the ohau glacier terminus receded at a mean net rate of about 77 m yr 1 and its surface lowered by 200 m between 17 690 and 17 380 yrs ago a long term continuation of ice retreat in the ohau glacier catchment is implied by moraine records at the head of irishman stream valley a tributary of the ohau glacier valley the irishman stream cirque glacier advanced to produce a set of lateglacial moraines at 13 000 500 yrs ago implying that the cirque glacier was less extensive prior to that advance we employed a glaciological model fit to these mapped and dated llgm moraines to derive snowline elevations and temperature parameters from the ohau glacier record the modeling experiments indicate that a snowline lowering of 920 50 m and temperature depression of 6 25 0 5 c below modern values allows for the ohau glacier to grow to an equilibrium position within the lgm moraine belt taken together with a glaciological simulation reported from the irishman stream valley snowlines and temperatures increased by at least 520 m and 3 6 c respectively between 18 000 and 13 000 yrs ago climate parameters derived from the ohau glacier reconstruction are similar to those derived from glacier records from patagonia to air temperature indicators from antarctica as well as to sea surface temperature and stratification signatures of the southern ocean we think that the best explanation for the observed southern llgm is that southern winter duration modulated southern ocean sea ice which in turn influenced southern ocean stratification and made the surface ocean cooler orbitally induced cooling of the southern ocean provides an explanation for the llgm in the southern alps having been coincident with the northern lgm we argue further that the global effect of north atlantic stadials led to disturbance of southern ocean stratification southward shifts of the subtropical front and retreat of southern alps glaciers collapse of southern ocean stratification during heinrich stadial 1 along with attendant sea surface warming triggered the onset of the last glacial termination in the southern alps of new zealand

evolution of the calabrian accretionary wedge central mediterranean 1 the neogene tectonics of the central mediterranean are related to the subduction and trench rollback of the ionian basin under eurasia causing the opening of the liguro provencal and tyrrhenian back arc basins and the formation of the calabrian accretionary wedge the calabrian accretionary wedge is a partially submerged accretionary complex located in the ionian offshore and laterally bounded by the apulia and malta escarpments while the history of the back arc extension process is fairly well defined the structure and evolution of the wedge are still poorly known we have analyzed and interpreted the available reflection multichannel and single channel seismic profiles in the ionian offshore and integrated them with other geological and geophysical data acquired in the last 40 years here we present unpublished seismic profiles to provide a new map of the tectonic structure of the ionian offshore and to define the structure of the wedge and its evolution during the last 15 myr our reconstruction points out that the messinian salinity crisis represents an important break in the evolution of the wedge as the basal decollement ramps up onto the messinian salt deposits producing a dramatic and fast forward propagation of the frontal thrust and resulting underplating of the underlying crustal ionian sequence during progressive trench rollback our results provide new insight into the style of accretion in a weakly converging setting which is typical for the mediterranean region

the medina wrench a key to the kinematics of the central and eastern mediterranean over the past 5 ma the medina wrenth in the central mediterranean is a transform fault connecting the plate collision in northwest africa and northern sicily with that occurring at the aegean plate boundary south of greece the more than 800 km long crescent shaped wrench zone is currently seismically quiet but exhibits major deformation since 5 ma within a belt 30 100 km wide it forms the southern boundary of two microplates moving eastward with respect to africa and europe a simple plate rotation model constrained by recent paleomagnetic data indicates that a continental iblean microplate and a hybrid continental oceanic ionian microplate separated along the malta escarpment have rotated anticlockwise by 11 and 12 respectively around poles in southern italy these rotations involved some 100 km of dextral eastward movement relative to africa of the ionian basin north of the medina wrench since 5 ma combining the published 26 clockwise rotation of the peloponnesus and northwest half of the aegean with the 12 anticlockwise rotation of the ionian microplate results in a a 99 agreement between the length of the seismic benioff zone beneath greece and the total convergence of the microplates and b an average rate of convergence across the aegean plate boundary southwest of the peloponnesus of 6 6 1cm a 1 since the miocene relative motion between microplates in a collision zone thus may be as much as 6 times faster than convergence between the major plates which spawned them and they can be considered rigid to the first order over the time span involved

acoustic facies of holocene megaturbidites in the eastern mediterranean abstract the acoustic facies of holocene megaturbidites in the central western abyssal plains of the eastern mediterranean sea is analysed combining core lithology and synthetic seismograms produced on the basis of p wave velocity profiles derived by multi sensor core logging from a core in the western herodotous trough the acoustic facies of the megaturbidite is divided in two layers 1 an upper transparent low velocity layer corresponding to structureless mud 2 a lower highly reflective high velocity layer corresponding to the graded sandy base correlation with sub bottom profiler data allowed us to estimate in about 21 23 m the maximum total thickness of the two layer megaturbidite in the ionian abyssal plain these results demonstrate that thicknesses traditionally computed on the basis of the acoustically transparent layer alone may produce a relevant underestimation of the total volume of the deposit the total volume of the megaturbidite extending over the ionian and sirte abyssal plains including the western herodotous trough is therefore estimated in about 162 10 km 3

deep sea sedimentary record of the late wisconsin cataclysmic floods from the columbia river new results from ocean drilling program site 1037 and u s geological survey high resolution seismic reflection profiles confirm the great thickness fast deposition rate distant source and convolute path of turbidites that fill the escanaba trough the rift valley of the southernmost segment of the gorda ridge accelerator mass spectrometry 14 c measurements provide the first direct dating of the escanaba trough turbidites demonstrating an average deposition rate faster than 10 m k y between 32 and 11 ka and as fast as 15 m k y during the oxygen isotope stage 2 lowstand in the upper 60 m of sediment the petrology of turbidite sand beds which are as much as 12 m thick show that the dominant source for the turbidites is from the columbia river which is more than 800 km to the north rather than from the much closer rivers of northern california new high resolution seismic reflection profiles show that except for areas of very recent volcanism the entire escanaba trough below 3200 m water depth is floored by the turbidite sequence that was cored in the upper 60 m at site 1037b the ages of the upper 120 m of turbidites correspond with the ages of channeled scabland deposits associated with latest quaternary jokulhlaups from glacial lake missoula the age and source characteristics suggest that these megaturbidite beds in escanaba trough are most likely deposits formed by hyperpycnally generated turbidity currents as the largest of the lake missoula floods entered the sea

geochemistry of fluid phases and sediments relevance to hydrothermal circulation in middle valley odp legs 139 and 169 geochemical and isotopic studies of pore fluids and solid phases recovered from the dead dog and bent hill hydrothermal sites in middle valley ocean drilling program leg 169 have been compared with similar data obtained previously from these sites during ocean drilling program leg 139 although generally the hydrothermal systems reflect non steady state conditions the data allow an assessment of the history of the hydrothermal processes sediment k al ratios as well as the distribution of anhydrite in the sediments suggest that the dead dog hydrothermal field has been and still is active in contrast similar data in the bent hill hydrothermal field indicate a waning of hydrothermal activity pore fluid and hydrothermal vent data in the dead dog hydrothermal field are similar in nature to the data collected during odp leg 139 in the area of the bent hill sulfide deposit however the pore water data indicate that recent wholesale flushing of the sediment column with relatively unaltered seawater has obliterated a previous record of hydrothermal activity in the pore fluids data from the deepest part of hole 1035a in the bent hill locality show the presence of hydrothermal fluids at greater depths in this area this suggests the origin of the hydrothermal fluids found to be emanating from hole 1035f which constitutes one of the first man made hydrothermal vents in the middle valley hydrothermal system similarly corked hole 858g because of seal failures has acted as a hydrothermal vent with sulfide deposits forming inside the cork

the medieval climate anomaly in antarctica abstract the medieval climate anomaly mca is a well recognized climate perturbation in many parts of the world with a core period of 1000 1200 ce here we are mapping the mca across the antarctic region based on the analysis of published palaeotemperature proxy data from 60 sites in addition to the conventionally used ice core data we are integrating temperature proxy records from marine and terrestrial sediment cores as well as radiocarbon ages of glacier moraines and elephant seal colonies a generally warm mca compared to the subsequent little ice age lia was found for the subantarctic islands south of the antarctic convergence the antarctic peninsula victoria land and central west antarctica a somewhat less clear mca warm signal was detected for the majority of east antarctica mca cooling occurred in the ross ice shelf region and probably in the weddell sea and on filchner ronne ice shelf spatial distribution of mca cooling and warming follows modern dipole patterns as reflected by areas of opposing temperature trends main drivers of the multi centennial scale climate variability appear to be the southern annular mode sam and el nino southern oscillation enso which are linked to solar activity changes by nonlinear dynamics

terrestrial and submarine evidence for the extent and timing of the last glacial maximum and the onset of deglaciation on the maritime antarctic and sub antarctic islands this paper is the maritime and sub antarctic contribution to the scientific committee for antarctic research scar past antarctic ice sheet dynamics pais community antarctic ice sheet reconstruction the overarching aim for all sectors of antarctica was to reconstruct the last glacial maximum lgm ice sheet extent and thickness and map the subsequent deglaciation in a series of 5000 year time slices however our review of the literature found surprisingly few high quality chronological constraints on changing glacier extents on these timescales in the maritime and sub antarctic sector therefore in this paper we focus on an assessment of the terrestrial and offshore evidence for the lgm ice extent establishing minimum ages for the onset of deglaciation and separating evidence of deglaciation from lgm limits from those associated with later holocene glacier fluctuations evidence included geomorphological descriptions of glacial landscapes radiocarbon dated basal peat and lake sediment deposits cosmogenic isotope ages of glacial features and molecular biological data we propose a classification of the glacial history of the maritime and sub antarctic islands based on this assembled evidence these include type i islands which accumulated little or no lgm ice type ii islands with a limited lgm ice extent but evidence of extensive earlier continental shelf glaciations type iii seamounts and volcanoes unlikely to have accumulated significant lgm ice cover type iv islands on shallow shelves with both terrestrial and submarine evidence of lgm and or earlier ice expansion type v islands north of the antarctic polar front with terrestrial evidence of lgm ice expansion and type vi islands with no data finally we review the climatological and geomorphological settings that separate the glaciological history of the islands within this classification scheme

holocene glacier history of the lago argentino basin southern patagonian icefield abstract we present new geomorphic stratigraphic and chronologic data for holocene glacier fluctuations in the lago argentino basin on the eastern side of the southern patagonian andes chronologic control is based on 14c and surface exposure 10be dating after the lateglacial maximum at 13 000 cal yrs bp the large ice lobes that filled the eastern reaches of lago argentino retreated and separated into individual outlet glaciers this recession was interrupted only by a stillstand or minor readvance at 12 200 cal yrs bp the eight largest of these individual outlet glaciers are from north to south upsala agassiz onelli spegazzini mayo ameghino perito moreno and grande formerly frias holocene recession of upsala glacier exposed brazo cristina more than 10 115 100 cal yrs bp and reached inboard of the holocene moraines in agassiz este valley by 9205 85 cal yrs bp ice remained in an inboard position until 7730 50 cal yrs bp several subsequent glacier readvances are well documented for the upsala and frias glaciers the upsala glacier readvanced at least seven times the first being a relatively minor expansion documented only in stratigraphic sections between 7730 50 and 7210 45 cal yrs bp the most extensive holocene advances of upsala glacier resulted in the deposition of the pearson 1 moraines and related landforms which are divided into three systems the pearson 1a advance occurred about 6000 5000 cal yrs bp and was followed by the slightly less extensive pearson 1b and 1c advances dated to 2500 2000 and 1500 1100 cal yrs bp respectively subsequent advances of upsala glacier resulted in deposition of the pearson 2 moraines and corresponding landforms also separated into three systems pearson 2a 2b and 2c constructed respectively at 700 400 and

high resolution seismic stratigraphy of glacial to interglacial fill of a deep glacigenic lake lake le bourget northwestern alps france abstract lake le bourget is a deep peri alpine glacial lake originating from the last glacial the wurm the lake has amassed over 250 m of sediment since the last glacial maximum two seismic sparker surveys on the lake revealed the glacial and post glacial sedimentary infill the depth and the morphology of the wurm erosion surface and penetrated the riss wurm interglacial deposits as deep as the underlying riss erosion surface the density of the seismic grid and the high resolution of the data even at greater depths allowed a detailed study of the sedimentary processes and of their evolution throughout the deglaciation five main seismic facies characterise the basin fill they are interpreted as glacial deposits glacio lacustrine sediments proglacial lacustrine fans alluvial fan deltas and authigenic lacustrine drape these occur as a suite of deposits associated with the major lake tributaries and are the result of major changes in sediment supply and style of discharge into the lake the three dimensional facies associations within the basin fill document the history of the basin and its catchment area since the onset of the deglaciation

mantle derived noble gases in natural gases from songliao basin china abstract abundances and isotopic compositions of noble gases have been measured in six natural gas samples co 2 and ch 4 rich from the songliao basin jilin province in northeastern china the samples contain noble gases of mantle origin the 3 he 4 he ratio reaches 5 0 times the atmospheric ratio in a three isotope plot of neon the 20 ne 22 ne up to 10 9 and 21 ne 22 ne up to 0 051 ratios make a positive correlation array together with natural gases from other continental areas compared with a correlation band for morb the natural gases have a lower slope with more nucleogenic 21 ne the natural gas samples contain radiogenic argon with 40 ar 36 ar ratios up to 7700 a positive correlation between 40 ar 36 ar and 20 ne 22 ne ratios indicates occurrence of mantle derived ar slight excess of 38 ar can be attributed to a nuclear reaction like 35 c1 p 38 ar apparent excesses of 129 2 xe 132 136 xe are recognized in four samples the excess of 129 xe up to 3 can be attributed to a decay of extinct 129 i excess 132 136 xe is not large enough to determine if the origin of the excess is 238 u or 244 pu anomaly in 129 xe 130 xe ratio is correlated with that of 136 xe 130 xe the isotopic features of the natural gases with radiogenic 4 he and nucleogenic 21 ne can be produced within the crust alternatively they may reflect the geochemical features of the subcontinental mantle which has been enriched in u th we can not distinguish the two possibilities however a natural gas from another basin in eastern china with a different reservoir age contains mantle derived neon which falls on the neon correlation line formed by the samples from the songliao basin this consistency suggests that the isotopic features of the natural gases aren t necessarily ascribable to surface contamination of radiogenic and nucleogenic isotopes

onset of deglacial warming in west antarctica driven by local orbital forcing an annually resolved ice core record from west antarctica indicates that warming driven by local insolation resulting from sea ice decline began in that region about 2 000 years before warming in east antarctica reconciling two alternative explanations for deglacial warming in the southern hemisphere

the escanaba trough gorda ridge hydrothermal system temporal stability and subseafloor complexity abstract the composition and temperature of vent fluids sampled from the active hydrothermal system in escanaba trough gorda ridge in 2000 and 2002 remain unchanged from the only time this field was previously sampled in 1988 odp leg 169 drilled nine bore holes at this site in 1996 some within meters of the vents yet this disturbance has not impacted the measured compositions or temperatures of the fluids exiting at the seafloor the fluids have maximum measured temperatures of 218 c and contain 20 more chloride than local ambient seawater our interpretation is that the fluid compositions are generated by supercritical phase separation of seawater with much of the water rock reaction occurring within the 400m thick sedimentary section that overlies the basalt at this site the odp drilling results provide information on the mineralogy and composition of materials below the seafloor as well as direct constraints not typically available on the physical conditions occurring below the seafloor hydrothermal system calculations utilizing geochemical modeling software suggest the fluids are close to saturation with a suite of minerals found subsurface suggesting equilibrium between the fluids and substrate these results provide an explanation for why the fluids have remained chemically stable for 14 yrs the pore water data from drilling suggest that the hydrology and chemistry of the hydrothermal system are much more complex within the sediment cover than would be expected from the surface manifestations of the hydrothermal system while the pore waters have chloride contents both greater and less than the local seawater only fluids with higher chloride contents vent at the seafloor our calculations suggest that at the current conditions the brines fluids with chlorinity greater than seawater are actually less dense than the vapors fluids with chlorinity less than seawater these density relationships may provide an explanation for why the brines are now venting preferentially to the vapors a situation opposite to what is usually observed or inferred

late quaternary pelagic sedimentation on the southern calabrian ridge and western mediterranean ridge eastern mediterranean abstract cores from plateaus lying some 150 200 m above the basin floors in areas of strong vertical relief visited during the cobblestone project consist entirely of pelagic marls with sapropels and tephras as minor lithologies all the plateau cores were correlated by means of isochronous lithologies and biostratigraphically calibrated a core from area 3 no 29 and two cores from area 4 no 45 and 6 were selected as reference sections and studied quantitatively in terms of grain sizes carbonate content and microfossil content faunal curves based on selected species of planktonic foraminifers correlate between the three cores which extend back in time to approximately 185 000 yr for area 4 and to 430 000 yr for area 3 winnowing resulted in a reduced sedimentation rate in area 3 in unusually high percentages of the coarser sediment fraction and in extended hiatuses at the top of the cores the highest temperature in surficial waters as indicated by the foraminiferal faunas is recorded in all three references sections at the base of an interval correlative with isotopic stage 5e 125 000 yr b p within sapropel s 5 clay mineralogy indicates basically uniform conditions in the two areas with the exception that smectite is more abundant in the calabrian ridge which is closer to its source area sicily sicily channel carbonates include calcite magnesian calcite and some dolomite sapropels sedimentary expression of stagnation represent up to 25 of the sedimentary column in an interval encompassing isotopic stage 5 through 7 the average organic carbon content in analysed sapropels is 3 1 versus 0 29 in normal pelagic sediments sapropels s 6 and s 8 are consistently accompanied by a foraminiferal fauna that is indicative of low salinity cool surficial waters whereas sapropels s 1 s 5 and s 7 occur in coincidence with the warmest peaks of the climatic faunal curve average sedimentation rate is 3 2 cm 1000 yr for core 29 5 5 cm 1000 yr for core 45 sedimentation rates calculated for basin cores are five to ten times higher sedimentation rates of sapropels and tephras are independent from regional sedimentation rates hiatuses in plateau cores correlate with debris flows in base of slope cores both occurring during times of enhanced bottom circulation and submarine erosion related to low stands of sea level in cold periods

warming and glacier recession in the rakaia valley southern alps of new zealand during heinrich stadial 1 abstract the termination of the last ice age featured a major reconfiguration of earth s climate and cryosphere yet the underlying causes of these massive changes continue to be debated documenting the spatial and temporal variations of atmospheric temperature during deglaciation can help discriminate among potential drivers here we present a 10be surface exposure chronology and glaciological reconstruction of ice recession following the last glacial maximum lgm in the rakaia valley southern alps of new zealand innermost lgm moraines at big ben have an age of 17 840 240 yrs whereas ice marginal moraines or ice molded bedrock surfaces at distances up valley from big ben of 12 5 km lake coleridge 25 km castle hill 28 km double hill 43 km prospect hill and 58 km reischek knob have ages of 17 020 70 yrs 17 100 110 yrs 16 960 370 yrs 16 250 340 yrs and 15 660 160 yrs respectively these results indicate extensive recession of the rakaia glacier which we attribute primarily to the effects of climatic warming in conjunction with geomorphological maps and a glaciological reconstruction for the rakaia valley we use our chronology to infer timing and magnitude of past atmospheric temperature changes compared to an overall temperature rise of 4 65 c between the end of the lgm and the start of the holocene the glacier recession between 17 840 and 15 660 yrs ago is attributable to a net temperature increase of 4 0 c from 6 25 to 2 25 c accounting for 86 of the overall warming approximately 3 75 c 70 of the warming occurred between 17 840 and 16 250 yrs ago with a further 0 75 c 16 increase between 16 250 and 15 660 yrs ago a sustained southward shift of the subtropical front stf south of australia between 17 800 and 16 000 yrs ago coincides with the warming over the rakaia valley and suggests a close link between southern ocean frontal boundary positions and southern mid latitude climate most of the deglacial warming in the southern alps occurred during the early part of heinrich stadial 1 hs1 of the north atlantic region because the stf is associated with the position of the westerly wind belt our findings support the concept that a southward shift of earth s wind belts accompanied the early part of hs1 cooling in the north atlantic leading to warming and deglaciation in southern middle latitudes

fluid composition of the sediment influenced loki s castle vent field at the ultra slow spreading arctic mid ocean ridge the hydrothermal vent field loki s castle is located in the mohns knipovich bend 73 n of the ultraslow spreading arctic mid ocean ridge amor close to the bear island sediment fan the hydrothermal field is venting up to 320 c hot black smoker fluids near the summit of an axial volcanic ridge even though the active chimneys have grown on a basaltic ridge geochemical fluid data show a strong sedimentary influence into the hydrothermal circulation at loki s castle compelling evidence for a sediment input is given by high alkalinity high concentrations of nh4 h2 ch4 c2 hydrocarbons as well as low mn and fe contents the low 13c values of co2 and ch4 and the thermogenic isotopic pattern of the c2 hydrocarbons in the high temperature vent fluids clearly point to thermal degradation of sedimentary organic matter and illustrate diminution of the natural carbon sequestration in sediments by hydrothermal circulation thus carbon release to the hydrosphere in arctic regions is especially relevant in areas where the active arctic mid ocean ridge system is in contact with the organic matter rich detrital sediment fans

methane anomalies in seawater above the loihi submarine summit area hawaii hydrothermal activity above loihi submarine volcano was characterized by water column distributions of methane ph and helium 3 it was found that the southern loihi summit is almost covered with hydrothermal plumes which have anomalously high concentrations of methane maximum 569 10 6cm3kg 1 accompanied by high concentrations of helium 3 and low ph values minimum 7 18 the plumes consist of two layers a shallow plume about 200 m above the summit and a deep plume about 100 m above the summit probably derived from different hydrothermal vents the shallow and deep plumes showed different ch43he and ch4ph ratios with the same 3heph ratio which implies that methane concentrations differ between the hydrothermal end members for the two plumes the variation of methane between the end members is suggested to result from inter vent inhomogeneity of bacterial activities that consume or produce methane within the vents comparison of the ch43he ratios of the two plumes with the previous data for loihi and other submarine hydrothermal areas confirms that the loihi hotspot has one to two orders of magnitude smaller ch43he value than those of the east pacific rise and the galapagos spreading centers

carbon isotopes of hydrocarbons and carbon dioxide in natural gases in china abstract 130 natural gases in the continent of china were determined for the abundance and carbon isotopes of hydrocarbons and carbon dioxide the 13c pdb values of methane range from 68 to 24 4 and the largest isotopic variability for hydrocarbons is of 13c1 there is no direct evidence for the presence of abiogenic hydrocarbon in natural gases in china one sample from songliao basin shows a heavier 13c1 24 and reverse isotopic distribution pattern 13c1 13c2 13c3 concerning the occurrence of mantle derived he ne ar and xe in the south songliao basin we propose that the methane mantle derived and heavy hydrocarbons ethane propane butane etc formed from polymerization of the mantle derived methane the 13c values for carbon dioxide range from 13 9 to 13 5 suggesting the multiple origins gases with co2 concentrations greater than 10 have a narrow range of 13c values from 8 to 2 and show higher 1he 4he ratios 0 1 times the atmospheric value suggesting that a mantle derived component is diluted by co2 derived from carbonate and or organic matter positive 13c values 4 14 indicate co2 reduction to ch2 co2 with trace concentration in ch4 rich gases can be attributed to microbial decomposition of organic matter in sedimentary rocks

sub antartic glacier extensions in the kerguelen region 49 s indian ocean over the past 24 000 years constrained by 36cl moraine dating similar to many other regions in the world glaciers in the southern sub polar regions are currently retreating in the kerguelen islands 49 s 69 e the mass balance of the cook ice cap cic the largest ice cap in this region experienced dramatic shrinking between 1960 and 2013 with retreat rates among the highest in the world this observation needs to be evaluated in a long term context however data on the past glacier extents are sparse in the sub antartic regions to investigate the deglaciation pattern since the last glacial maximum lgm period we present the first 13 cosmogenic 36cl surface exposure ages from four sites in the kerguelen islands the 36cl ages from erratic and moraine boulders span form 24 4 2 7 ka to 0 3 0 1 ka we combined these ages with existing glacio marine radiocarbon ages and bathymetric data to document the temporal and spatial changes of the island s glacial history ice began to retreat on the main island before 24 4 2 7 ka until around the time of the antartic cold reversal acr period 14 5 12 9ka during which the bontemps moraine was formed by the advance of a cic outlet glacier deglaciation continued during the holocene probably until 3ka with evidence of minor advances during the last millennium the chronology is in pace with major changes in 18o in a recent west antarctica ice core record showing thet kerguelen islands glciers are particularly sensitive and relevant to document climate change in the southern polar regions

origin of nitrogen rich natural gases in the california great valley evidence from helium carbon and nitrogen isotope ratios abstract dry natural gases produced from the sacramento and northern san joaquin basins contain up to 87 nitrogen 15n measurements for gases with n2 8 vary from 0 9 to 3 5 methane 13c values vary from 61 to 15 3 he 4 he ratios indicate the presence of mantle derived helium in addition to radiogenic crustal helium and suggest that the gases may originate from mixing between three principal components a hydrocarbon rich gas with 3 he 4 he 0 1r a derived from the microbial and thermogenic alteration of sedimentary organic matter a hydrocarbonrich gas with 3 he 4 he 2 75r a derived from the localized pyrolysis of sediments by magmatic volatiles and a nitrogenrich gas with 3 he 4 he 1r a the nitrogen rich component is characterized by methane 13c less negative than 25 and n 2 ar ratios as high as 22 000 nitrogen concentrations tend to increase towards the basement along the shallow eastern margin of the valley suggesting that the nitrogen rich component is derived from metasedimentary rocks deep within the crust the coast ranges fraciscan complex which was thrust well beneath the great valley during late mesozoic and early cenozoic subduction appears to be the most likely source

influence of the southern annular mode on the sea ice ocean system 1 the global sea ice ocean model orca2 lim driven by the ncep ncar national centers for environmental prediction national center for atmospheric research reanalysis daily 2 m air temperatures and 10 m winds and by monthly climatologies for precipitation cloud cover and relative humidity is used to investigate the impact of the southern annular mode sam on the antarctic sea ice ocean system our results suggest that the response of the circumpolar southern ocean consists of an annular and a nonannular component for the sea ice cover the non annular component seems to be the most important the annular component strongly affects the overall patterns of the upper ocean circulation when the sam is in its positive phase a northward surface ekman drift a downwelling at about 45 degreess and an upwelling in the vicinity of the antarctic continent are simulated the non annular component has a significant impact at the regional scale especially in the weddell ross amundsen and bellingshausen seas in those regions the pressure pattern associated with the sam induces meridional winds which advect warmer air in the weddell sea and around the antarctic peninsula and colder air in the amundsen and ross seas this implies a dipole response of sea ice to the sam with on average a decrease in ice area in the weddell sea and around the antarctic peninsula and an increase in the ross and amundsen seas during years with a high sam index the long term trend in the observed sea ice area does not appear to be related to the trend in the sam index

response of the antarctic circumpolar current to atmospheric variability abstract historical hydrographic profiles combined with recent argo profiles are used to obtain an estimate of the mean geostrophic circulation in the southern ocean thirteen years of altimetric sea level anomaly data are then added to reconstruct the time variable sea level and this new dataset is analyzed to identify and monitor the position of the two main fronts of the antarctic circumpolar current acc during the period 1993 2005 the authors relate their movements to the two main atmospheric climate modes of the southern hemisphere the southern annular mode sam and the el nino southern oscillation enso the study finds that although the fronts are steered by the bathymetry which sets their mean pathway on first order in flat bottom areas the fronts are subject to large meandering because of mesoscale activity and atmospheric forcing while the dominant mode of atmospheric variability in the southern hemisphere sam is relatively symmetric the oceanic response of the fronts is not show

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

the challenging application of cosmogenic dating methods in residual glacial landforms the case of sierra nevada spain abstract an accurate review of the literature on surface exposure dating methods shows evidence of the difficulty in applying cosmogenic dating methods to old moraines because of the intensity of late quaternary erosion processes moreover as in some previous cases we also found special difficulties in applying these methods to lia moraines caused by the intensity of current paraglacial processes the objective of this study is to apply cosmogenic dating methods to very old and very young moraines which in both cases have been or are being affected intensively by erosion with this purpose we collected samples of boulders from moraines corresponding to i the penultimate glaciation and ii the little ice age lia both from sierra nevada in the south of the iberian peninsula the sampling strategy was based on a preliminary accurate analysis of the geomorphological settings of two valley sites that resulted in the collection of only four boulder samples from an old moraine and three more from a very recent moraine using in situ produced cosmogenic 10be to date these boulders the old samples yielded an age of ca 130 135 ka for moraine stabilization the younger samples indicate that the lia moraine accretion probably occurred between the fourteenth and seventeenth centuries with a subsequent stage of accumulation during the nineteenth century as suggested by historical documents dating a glaciation that occurred prior to the last pleistocene glacial cycle and dating lia glacial stages are novel in the context of iberian glaciations and agree with other palaeoenvironmental studies in iberian and in other european mountains the limited number of boulders adequate for cosmic ray exposure dating prevents statistical methods to be applied and therefore highlights the need to improve geomorphological criteria in sample selection

glacier retreat in new zealand during the younger dryas stadial the younger dryas a period of sudden cooling in the northern hemisphere about 12 900 years ago is perhaps the best known example of abrupt climate change but the global extent of the younger dryas is a topic of intense debate particularly in the record of glacial behaviour in new zealand a new reconstruction of the growth and retreat patterns of glaciers in the southern alps in new zealand at the time of the younger dryas supports the suggestion that temperature reductions in the north caused warming and glacial retreat in the southern hemisphere through a series of climate feedbacks the younger dryas during which northern hemisphere temperatures cooled drastically in just a few years is perhaps the best known example of abrupt climate change but its global extent is under debate particularly in the record of glacial behaviour in new zealand these authors present evidence for glacial retreat in new zealand during the younger dryas supporting the hypothesis that northern hemisphere climate changes caused southern hemisphere warming through a series of climate feedbacks millennial scale cold reversals in the high latitudes of both hemispheres interrupted the last transition from full glacial to interglacial climate conditions the presence of the younger dryas stadial 12 9 to 11 7 kyr ago is established throughout much of the northern hemisphere but the global timing nature and extent of the event are not well established evidence in mid to low latitudes of the southern hemisphere in particular has remained perplexing1 2 3 4 5 6 the debate has in part focused on the behaviour of mountain glaciers in new zealand where previous research has found equivocal evidence for the precise timing of increased or reduced ice extent1 2 3 the interhemispheric behaviour of the climate system during the younger dryas thus remains an open question fundamentally limiting our ability to formulate realistic models of global climate dynamics for this time period here we show that new zealand s glaciers retreated after 13 kyr bp at the onset of the younger dryas and in general over the subsequent 1 5 kyr period our evidence is based on detailed landform mapping a high precision 10be chronology7 and reconstruction of former ice extents and snow lines from well preserved cirque moraines our late glacial glacier chronology matches climatic trends in antarctica southern ocean behaviour and variations in atmospheric co2 the evidence points to a distinct warming of the southern mid latitude atmosphere during the younger dryas and a close coupling between new zealand s cryosphere and southern high latitude climate these findings support the hypothesis that extensive winter sea ice and curtailed meridional ocean overturning in the north atlantic led to a strong interhemispheric thermal gradient8 during late glacial times in turn leading to increased upwelling and co2 release from the southern ocean9 thereby triggering southern hemisphere warming during the northern younger dryas

a major advance of tropical andean glaciers during the antarctic cold reversal a moraine chronology determined by surface exposure dating shows that glaciers in the northern tropical andes expanded to a larger extent during the antarctic cold reversal 14 500 to 12 900 years ago than during the younger dryas stadial 12 800 to 11 500 years ago contrary to previous studies as a result previous chronologies and climate interpretations from tropical glaciers may need to be revisited the younger dryas was a cold period immediately prior to the present warm interglacial period there is clear evidence that it occurred throughout much of the northern hemisphere but its global extent remains debatable prior work in the tropical andes suggested extensive glacial advances during the younger dryas vincent favier and colleagues present new cosmogenic dating of glacial deposits and a reassessment of existing datasets from other glaciated andean landscapes to show that instead maximal glacial advances took place in the preceding antarctic cold reversal rather than a major advance the younger dryas now appears to have been associated with modest glacial retreat the younger dryas stadial a cold event spanning 12 800 to 11 500 years ago during the last deglaciation is thought to coincide with the last major glacial re advance in the tropical andes1 this interpretation relies mainly on cosmic ray exposure dating of glacial deposits recent studies however have established new production rates2 3 4 for cosmogenic 10be and 3he which make it necessary to update all chronologies in this region1 5 6 7 8 9 10 11 12 13 14 15 and revise our understanding of cryospheric responses to climate variability here we present a new 10be moraine chronology in colombia showing that glaciers in the northern tropical andes expanded to a larger extent during the antarctic cold reversal 14 500 to 12 900 years ago than during the younger dryas on the basis of a homogenized chronology of all 10be and 3he moraine ages across the tropical andes we show that this behaviour was common to the northern and southern tropical andes transient simulations with a coupled global climate model suggest that the common glacier behaviour was the result of atlantic meridional overturning circulation variability superimposed on a deglacial increase in the atmospheric carbon dioxide concentration during the antarctic cold reversal glaciers advanced primarily in response to cold sea surface temperatures over much of the southern hemisphere during the younger dryas however northern tropical andes glaciers retreated owing to abrupt regional warming in response to reduced precipitation and land surface feedbacks triggered by a weakened atlantic meridional overturning circulation conversely glacier retreat during the younger dryas in the southern tropical andes occurred as a result of progressive warming probably influenced by an increase in atmospheric carbon dioxide considered with evidence from mid latitude andean glaciers16 our results argue for a common glacier response to cold conditions in the antarctic cold reversal exceeding that of the younger dryas

radiocarbon chronology of the last glacial maximum and its termination in northwestern patagonia abstract we examine the timing and magnitude of the last glacial maximum lgm and the last glacial termination lgt in northwestern patagonia situated in the middle latitudes of south america our data indicate that the main phase of the lgt began with abrupt warm pulses at 17 800 and 17 100 cal yrs bp accompanied by rapid establishment of evergreen temperate rainforests and extensive deglaciation of the andes within 1000 years this response shows that south american middle latitude temperatures had approached average interglacial values by 16 800 cal yrs bp the temperature rise in northwestern patagonia coincides with the beginning of major warming and glacier recession in the southern alps of new zealand at southern mid latitudes on the opposite side of the pacific ocean from this correspondence the warming that began at 17 800 cal yrs bp appears to have been widespread in middle latitudes of the southern hemisphere accounting for at least 75 of the total temperature recovery from the lgm to the holocene moreover this warming pulse is coeval with the first half of the heinrich stadial 1 hs1 in the north atlantic region hs1 featured a decline of north atlantic meridional overturning circulation a southward shift of the westerly wind belt in both hemispheres and of the intertropical convergence zone as well as a weakening of the asian monsoon along with the initiating trigger identifying the mechanisms whereby these opposing climate signals in the two polar hemispheres interacted whether through an oceanic or an atmospheric bipolar seesaw or both lies at the heart of understanding the lgt

helium and carbon gas geochemistry of pore fluids from the sediment rich hydrothermal system in escanaba trough abstract ocean drilling program odp leg 169 which was conducted in 1996 provided an opportunity to study the gas geochemistry in the deeper part of the sediment rich hydrothermal system in escanaba trough gas void samples obtained from the core liner were analyzed and their results were compared with analytical data of vent fluid samples collected by a submersible dive program in 1988 the gas geochemistry of the pore fluids consisted mostly of a hydrothermal component and was basically the same as that of the vent fluids the he isotope ratios r ra 5 6 6 6 indicated a significant mantle he contribution and the c isotopic compositions of the hydrocarbons 13c ch4 43 13c c2h6 20 were characterized as a thermogenic origin caused by hydrothermal activity on the other hand the pore fluids in sedimentary layers away from the hydrothermal fields showed profiles which reflected lateral migration of the hydrothermal hydrocarbons and abundant biogenic ch4 helium and c isotope systematics were shown to represent a hydrothermal component and useful as indicators for their distribution beneath the seafloor similarities in he and hydrocarbon signatures to that of the escanaba trough hydrothermal system were found in some terrestrial natural gases which suggested that seafloor hydrothermal activity in sediment rich environments would be one of the possible petroleum hydrocarbon generation scenarios in unconventional geological settings

transparent layers in seismic reflection records from the central ionian sea mediterranean evidence for repeated catastrophic turbidite sedimentation during the quaternary abstract echosounding and scs records from the ionian and sirte abyssal plains show below the holocene augias megaturbidite two additional thick transparent layers which by analogy are interpreted as turbidites estimated thicknesses are 10 and 35 m upper and lower as a minimum no consideration of presumable variations of acoustic velocities the resulting sediment volumes are about 26 and about 200 km 3 respectively both layers occupy the entire abyssal plain basins similar to the holocene augias megaturbidite a provenance of mobilized sediments from the gulf of sirte into the basins is assumed the ages of the two turbidites have been estimated at 235 000 and 650 000 years respectively it is speculated that mobilization was triggered by tsunamis related to volcanic events or earthquakes in the southern aegean region

a miocene tectonic inversion in the ionian sea central mediterranean evidence from multichannel seismic data it is widely accepted that the central and eastern mediterranean are remnants of the neo tethys however the orientation and timing of spreading of this domain remain controversial here we present time migrated and pre stack depth migrated nw se oriented archimede 1997 lines together with the prismed01 1993 profile to constrain the evolution of the ionian basin our interpretation allows us to identify a large scale set of sw ne striking reverse faults beneath the ionian abyssal plain these primarily nw vergent faults are characterized by a spacing comprised between 10 to 20 km and a dip ranging from 60 to 65 degree sign following very recent paleogeographic reconstructions we propose that the set of n degree sign 55 features initially formed as normal faults during the nw se trending seafloor spreading of the ionian basin after its late triassic early jurassic rifting based on geometric comparisons with the intraplate deformation observed beneath the central indian ocean we show that the inherited oceanic normal faults were reactivated under compression as reverse faults well developed tortonian syntectonic basins developed nw of the major faults and the base of the messinian evaporites mobile unit is slightly folded by the activity of the faults we show that 3 4 km of total shortening occurs over a 80 km wide area beneath the ionian abyssal plain resulting in a bulk shortening of 3 5 5 we propose a link between the tortonian early messinian inversion of the fault pattern and a plate tectonic reorganization prior to the main phase of back arc opening of the tyrrhenian domain

regional modeling of surface mass balance on the cook ice cap kerguelen islands 49 circ mathrm s 49 s 69 circ mathrm e 69 e we assess the ability of the regional circulation model mar to represent the recent negative surface mass balance smb observed over the kerguelen islands 49 circ hbox s 69 circ hbox e and evaluate the uncertainties in smb projections until the end of the century the mar model forced by era interim reanalysis shows a good agreement with meteorological observations at kerguelen particularly after slight adjustment of the forcing fields 10 humidity 0 8 circ hbox c all year round to improve precipitation occurrence and intensity the modeled smb and surface energy balance seb are also successfully evaluated with observations and spatial distributions are explained as being largely driven by the elevation gradient and by the strong west to east foehn effect occurring on the ice cap we select five general circulation models gcms from the coupled model intercomparison project phase 5 cmip5 by evaluating their ability to represent temperature and humidity in the southern mid latitudes over 1980 1999 with respect to era interim and use them to force the mar model these simulations fail to replicate smb observations even when outputs from the best cmip5 model access1 3 are used as forcing because all gcms fail in accurately reproducing the circulation changes observed at kerguelen since the mid 1970s global models chosen to represent extreme values of smb drivers also fail in producing extreme values of smb suggesting that more rigorous modeling of present and future circulation changes with gcms is still needed to accurately assess future changes of the cryosphere in this area