holocene glacial activity and climatic variations in the swiss alps reconstructing a continuous record from proglacial lake sediments cores recovered from proglacial lake silvaplana swiss alps were investigated to examine the influence of holocene glaciers on lacustrine sedimentation during times of glacial activity in the catchment the sedimentation in the lake is dominated by the input of silt and clay sized material delivered by glacial meltwaters the deposition of fine grained material and the formation of varves reflect the existence of glaciers in the catchment and can therefore be used for the reconstruction of glacial history sedimentation rates are up to nine times higher in the varved than in the non varved sediments indicating significantly higher erosion rates under glaciated catchment conditions glacial varves were deposited in lake silvaplana during glacial retreat in the latest pleistocene and early holocene until 9400bp non varved deposits having a higher organic content and coarser grain sizes accumulated at lower rates when glacial activity was absent or negligible within the catchment between 9400 and 3300 bp

holocene coastal glaciation of alaska holocene uctuations of the three cirque glaciers on the seward peninsula and ve groups of tidewater and land terminating glaciers along the northernmost gulf of alaska provide a proxy record of late holocene climatic change furthermore the movements of the coastal glaciers were relevant to late holocene native american migration the earliest expansion was recorded about 6850 yr bp by hubbard glacier at the head of yakutat bay in the gulf of alaska however its down fjord advance to the bay mouth was delayed until 2700 bp similarly expansions of the icy bay bering and mccarty glaciers occurred near their present termini by 3600 3000 bp compatible with marked cooling and precipitation increases suggested by the alaskan pollen record decrease in glacier activity 2000 bp was succeeded by advances of gulf coastal glaciers between 1500 and 1300 bp correlative with early medieval expansions across the northern hemisphere a medieval optimum encompassing at least a few centuries prior to ad 1200 is recognized by general retreat of land terminating glaciers but not of all tidewater glaciers little ice age advances of land based glaciers many dated with the precision of tree ring cross dating were centered on the middle 13th or early 15th centuries the middle 17th and the last half of the 19th century a d strong synchrony of these events across coastal alaska is evident 2000 elsevier science ltd all rights reserved

a three dimensional surface velocity field for the mississippi delta implications for coastal restoration and flood potential accurate estimates of the current rate of subsidence in the mississippi delta southern united states provide a context for planning of wetland restoration and predictions of storm surge flooding we present a comprehensive three dimensional surface velocity field for the mississippi delta based on a network of 36 high precision continuous gps stations we show that while the majority of the delta is relatively stable the southern portion continues to experience high rates of subsidence 5 6 mm yr 1 our data are consistent with long term tide gauge records at grand isle louisiana and several stations in florida the current rate of relative sea level rise combined effect of land subsidence and sea level rise along parts of the coastal delta is 8 9 mm yr 1 most tide gauge stations have recorded sea level rise acceleration after a d 1970 these data have implications for land reclamation and wetland restoration in the region parts of the delta may not be viable in the long term

the north american late wisconsin ice sheet and mantle viscosity from glacial rebound analyses abstract observations of sea level and crustal response to glacial loading cycles provide constraints on the mantle rheology function e and as well as on the ice load i with the latter being largely free from a priori glaciological or climate assumptions and appropriate therefore for testing any such hypotheses this paper presents new results for both continental mantle e and i for the late wisconsin ice sheet using geological evidence for relative sea level change rsl and tilting of palaeo lake shorelines complemented with loose constraints from observations of present day radial crustal displacement across north america the focus is on evidence from near or within the former maximum ice margins and the resulting earth response is representative of sub continental mantle conditions the inversion of the sea level information has limited resolution for earth rheology and simple three layer models characterized by depth averaged effective lithospheric thickness h and upper and lower mantle viscosities um and um respectively adequately describe the response function yielding parameters earth model e 6 of h 102 85 120 km um 5 1 1020 3 5 7 5 x1020 lm 1 3 1022 0 8 2 8 x1022 where the numbers in parenthesis are 95 confidence limits the details of the ice sheet with one exception are not strongly dependent on the rheological assumptions within this range the exception is the lower mantle viscosity that remains correlated with the magnitude scaling of the ice sheet a link that is largely broken by introducing constraints from glacial loading effects on the earth s rotation and dynamic flattening the difference between the continental um and the comparable estimate of 1 2 5 x1020 for ocean mantle is statistically significant shoreline gradient information from glacial lakes mcconnell agassiz algonquin and ojibway provide strong constraints on the response within the interior of the ice sheet and the resulting ice sheet model lw 6 is characterized by multiple ice domes from at least 17 18 ka onwards the resolution for earlier periods is largely constrained by global ice volume considerations the two principal domes are over southern nunavut the keewatin dome and over quebec labrador both of 3500 m thickness separated by an ice ridge some 1500 m lower than the domes the latter a requirement imposed by the gradient information over western canada ice thickness gradients east of the cordilleras are partly constrained by the shoreline data for former lake mcconnell as is the lateglacial ice thickness of the keewatin dome and indicate that any ice free corridor between the laurentian and cordilleran components is unlikely to have existed before 13ka reconstructions of the glacial lakes are consistent with the locations and timing of the observational evidence for the four major lake systems with the likely drainage routes identified the evolution of the lw 6 ice volume function expressed as equivalent sea level is characterized by a rapid decrease in ice volume from 15 to 14 5 ka corresponding to the bolling allerod period in the main from rapid ice retreat along the southern margin with further contributions from drainage through the st lawrence river valley and from ice retreat from the major northern straits and gulfs but not hudson strait where the rsl data point to late removal of ice after 10 ka the contribution of the drainage of the lakes to global sea level rise is small

the rhone glacier was smaller than today for most of the holocene we present the development and application of the novel in situ cosmogenic 14 c 10 be chronometer to recently exposed proglacial bedrock of the rhone glacier switzerland results show that during the holocene the glacier was smaller than today for 6500 2000 yr and larger than today for 4500 2000 yr this pattern is consistent with limited data from other techniques for glaciers in the alps and scandinavia but in contrast to glaciers from the southern alps of new zealand emphasizing the high sensitivity of large mountain glaciers to small climate changes the 14 c 10 be chronometer also shows that abrasion rates beneath the rhone glacier increased with ice speed

discovery of early holocene wood and peat on the forefield of the pasterze glacier eastern alps austria during recent years a number of fragments of pinus cembra and larix decidua as well as peat were found in front of the tongue of the pasterze glacier in the eastern alps these were washed out by the stream from under the present ice the wood originates from trees which reached ages of upto 400 years or more radiocarbon dating shows them to come from the early holocene they indicate that between cal bc 8100 and cal bc 6900 the pasterze glacier was smaller than at present the pasterze glacier advanced around cal bc 6900 a lump of peat shows that around cal bc 6300 at the latest the pasterze glacier was again smaller than today the radiocarbon age of the fulvic acid fraction of thepeat suggests that growth could have continued until cal bc 5430 5080 further wood samples dated to around cal bc 4800 and cal bc 3800 show that at these times the pasterze glacier was smaller than at present the pasterze glacier had a relatively limited extent over long periods inthe early holocene thus mostly favou

late pleistocene holocene surface processes and landscape evolution in the central swiss alps abstract the european alps are a geomorphologically active region and experience a number of gravity driven hillslope processes soil and landscape formation in the alps has consequently undergone several minor and major traceable changes of developmental trajectories during the holocene soil development is hypothesised to be often non linear with time and characterised by stages of progressive and regressive evolution caused by upbuilding formation profile deepening and erosion profile shallowing several cold and warm climate phases are identified during the holocene but it is largely unknown which effects these might have had on slope processes by using datable moraines 10 be and mires 14 c we have constructed a temporal framework for these processes using the geochemical imprint of mires in the alpine setting of the goschener valley of the central swiss alps we reconstructed general mostly erosional landscape processes for the last ca 10 ka as this is the type locality for the goschener cold phase we assumed that this phase goschener cold phase i and ii 1 5 and 2 5 ka bp should have left easily recognizable traits after deglaciation 11 12 ka bp soil evolution was progressive beginning around 8 ka bp we detect a distinct increase in erosion here together with a vegetation change towards tundra vegetation and the highest measured rates of carbon sequestration other phases of high geomorphic activity were recognised ca 5 6 ka bp 4 ka bp and to a lesser extent 1 3 ka ago the cold phase at 5 6 ka bp corresponds to a less distinct change in vegetation and lessened erosion human impact is increasingly obvious since about 2 4 ka bp which overlaps with the goschener cold phase nonetheless erosion processes were not extraordinarily high during this period and a climate effect cannot be distinguished we detect evidence of increasing human disturbance regressive soil evolution for about the last 1 ka we also detect an increase in dust flux during the last ca 4 5 ka presumably due to the landscape change s in the sahara during this time

stratigraphic evidence for multiple holocene advances of lillooet glacier southern coast mountains british columbia holocene lateral moraines in the coast mountains of british columbia are commonly composed of multiple drift units related to several glacier advances in this paper we document lateral moraine stratigraphy at lillooet glacier in the southern coast mountains five tills separated by laterally extensive paleosols and layers of large woody debris were found in three cross sectional exposures through the northeast lateral moraine and two shallow gullies incised into its steep proximal face eighteen new radiocarbon ages constrain the timing of five separate advances of lillooet glacier 1 prior to 3000 14 c years bp 2 3000 14 c years bp 3 2500 14 c years bp 4 1700 to 1400 14 c years bp and 5 during the little ice age lia after 470 14 c years bp the lillooet glacier chronology is broadly synchronous with other glacier records from the coast mountains these records collectively demonstrate climate variability at higher frequencies during the late holocene than is apparent from many paleoecological reconstructions reconstructions of glacier fluctuations are often hampered by poor preservation of landforms that predate the extensive lia advances of the latest holocene our results highlight the potential of lateral moraine stratigraphy for reconstructing these earlier events

quantifying holocene lithospheric subsidence rates underneath the mississippi delta abstract the pattern of holocene relative sea level rsl change on the us gulf coast has been a long standing subject of debate featuring opposing scenarios of continuous submergence versus one or more holocene rsl highstands the significance of this debate is that the relative role of eustasy glacial isostatic adjustment gia and lithospheric flexural subsidence associated with mississippi delta sediment loading remains unresolved here we present a new rsl record from the louisiana chenier plain 100 km west of the mississippi delta margin based on ams 14 c dated marsh basal peat this enables us to provide for the first time constraints on holocene lithospheric subsidence rates underneath one of the world s major deltas our new record conclusively shows that no middle holocene rsl highstands occurred on the central us gulf coast rather it exhibits a pattern of progressive rsl rise comparable to that from the mississippi delta suggesting that long wavelength gia is a dominant deformational process driving lithospheric subsidence in the entire region by means of forebulge collapse nevertheless a 0 15 0 07 mm yr differential rate of subsidence between the chenier plain and key portions of the mississippi delta including the new orleans metropolitan area exists this shows that while the sediment loading effect is real it is about an order of magnitude smaller than recent studies have postulated

anthropogenic and geologic influences on subsidence in the vicinity of new orleans louisiana new measurements of ongoing subsidence of land proximal to the city of new orleans louisiana and including areas around the communities of norco and lutcher upriver along the mississippi are reported the rates of vertical motion are derived from interferometric synthetic aperture radar insar applied to uninhabited aerial vehicle synthetic aperture radar uavsar data acquired on 16 june 2009 and 2 july 2012 the subsidence trends are similar to those reported for 2002 2004 in parts of new orleans where observations overlap in particular in michoud the 9th ward and chalmette but are measured at much higher spatial resolution 6 m the spatial associations of cumulative surface movements suggest that the most likely drivers of subsidence are groundwater withdrawal and surficial drainage dewatering activities high subsidence rates are observed localized around some major industrial facilities and can affect nearby flood control infrastructure substantial subsidence is observed to occur rapidly from shallow compaction in highly localized areas which is why it could be missed in subsidence surveys relying on point measurements at limited locations

a mid european decadal isotope climate record from 15 500 to 5000 years b p oxygen isotope ratios of precipitation delta18op inferred from deep lake ostracods from the ammersee southern germany provide a climate record with decadal resolution the record in detail shows many of the rapid climate shifts seen in central greenland ice cores between 15 000 and 5000 years before the present b p negative excursions in the estimated delta18op from both of these records likely reflect short weakenings of the thermohaline circulation caused by episodic discharges of continental freshwater into the north atlantic deviating millennial scale trends however indicate that climate gradients between europe and greenland changed systematically reflecting a gradual rearrangement of north atlantic circulation during deglaciation

surface exposure dating of moraines in the kromer valley silvretta mountains austria evidence for glacial response to the 8 2 ka event in the eastern alps 10 be dating of a pronounced glacier advance kromer stadial in the western part of the silvretta mountains western austria yielded ages ranging from 8010 360 to 8690 410 years with a mean age for moraine stabilization of 8410 690 years hence the kromer stadial which was previously considered as early preboreal may represent the glacier response to the early phase of the 8 2 ka event as it is recorded in the greenland ice cores the glacier advanced to a position beyond its little ice age lia limit the end moraines are situated 750 1000 m downvalley from the glacier ends in 1850 the corresponding drop of the equilibrium line altitude relative to the lia datum was 75 m the glacier advance was followed by a period of glacier recession and rock glacier development in total the climatic fluctuation may have lasted for about 500 200 years the age and duration of the climatic fluctuation is in good accordance with the misox cold phase and ce 3 climatic fluctuation as recorded in switzerland climate during the kromer stadial was characterized by more humid conditions than today along the northern fringe of the alps and slightly negative to moderately positive changes in precipitation in the central part of the austrian alps summer temperatures changes were most likely in the order of i to 0k mean annual temperature was 1 5k to 2k lower than today at least during the second phase of the climatic fluctuation

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

reconciliation of sea level observations in the western north atlantic during the last glacial cycle abstract a south to north gradient of increasing marine isotope substage mis 5a 80 ka bp sea level has been recorded across the caribbean and surrounding region relative to present mis 5a sea levels range from 19 m to more than 3 m between barbados haiti the bahamas florida bermuda and the us atlantic coast in contrast no gradient in sea level is observed for the last interglacial period mis 5e 128 118 ka bp at tectonically stable localities in the same region with deposits generally lying several metres above present we demonstrate here that these controversial observations are reconciled by taking into account the isostatic response of the earth to glacial loading and unloading a fundamental effect that is commonly overlooked in the interpretation of sea level observations from different locations to define a global sea level curve furthermore the observed gradient can be used to place constraints on earth rheology and is an important indicator of the behaviour of the north american ice sheets during the last glacial cycle

holocene glaciation and climate evolution of baffin island arctic canada abstract lake sediment cores and cosmogenic exposure ce dates constrain the pattern of deglaciation and evolution of climate across baffin island since the last glacial maximum lgm ce dating of erratics demonstrates that the northeastern coastal lowlands became ice free ca 14 ka as the laurentide ice sheet lis receded from its lgm margin on the continental shelf coastal lakes in southeastern baffin island started to accumulate sediment at this time whereas initial lacustrine sedimentation was delayed by two millennia in the north reduced organic matter in lake sediment deposited during the younger dryas chron and the lack of a glacial readvance at that time suggest cold summers and reduced snowfall ice retreated rapidly after 11 ka but was interrupted by a widespread readvance of both the lis and local mountain glaciers 9 6 ka cockburn substage a second readvance occurred just before 8 ka during a period of unusually cold summers corresponding to the 8 2 ka cold event in the greenland ice sheet most local glaciers were behind their present margins before 7 ka and in some instances much earlier although the foxe dome of the lis continued to slowly retract toward the present day barnes ice cap throughout the holocene pollen in lake sediments is rare and dominated by exotic sources prior to 12 ka subsequently grass tundra became established followed by modern tundra vegetation ca 8 ka with subtle changes in pollen assemblages in the late holocene lake primary productivity peaked in the early holocene before terrestrial vegetation or marine surface waters reached their apparent thermal maxima lacustrine marine and glacial proxies all reflect significant late holocene cooling the onset of neoglaciation is well dated in lacustrine records at ca 6 ka with intensification after 2 5 ka the expansion of local glaciers during the little ice age represents the most extensive advance since 7 ka we suggest that the replacement of atlantic surface waters by cold low salinity arctic ocean water coupled with the steady reduction of summer insolation resulted in a significant positive sea ice feedback that produced a larger late holocene summer temperature depression over the baffin region than in the pacific sector of the arctic

holocene fire regime changes from multiple site sedimentary charcoal analyses in the lourdes basin pyrenees france one lake and three peat bogs from the lourdes glacial basin france were used for macrocharcoal analyses and fire frequency reconstruction over the entire holocene 11700 years the chronology was based upon thirty three 14c ams dates comparison of the distribution of both charcoal accumulation rate char and fire return intervals showed that charcoal accumulation significantly differs between the lake and the peat bogs but that frequency calculation overcomes the disparity between these site types a composite frequency was built from the four individual records to assess regional versus local variability and fire regime controls by comparisons with regional fire activity holocene climatic oscillations and vegetation history the millennial variability can be depicted as follows relatively high frequency between 8000 and 5000 cal a bp up to 5 fires 500 yrs relatively low frequency between 5000 and 3000 cal a bp down to 0 fires 500 yrs and an increase between 3000 and 500 cal a bp up to 4 fires 500 yrs from 8000 to 5000 cal a bp fire frequency displays strong synchrony between sites and appears to be mostly driven by increased summer temperature characterizing the holocene thermal maximum htm on the contrary during the last 3000 years fire frequency was heterogeneous between sites and most probably human driven however higher frequency at the millennial scale during the mid holocene strongly suggests that the perception of human driven fire regime depends on the strength of natural controls

holocene optimum events inferred from subglacial sediments at tschierva glacier eastern swiss alps abstract this study investigates the subglacial sedimentary archive at tschierva glacier eastern swiss alps subfossil wood remains found at the retreating glacier tongue indicate that their emergence results from recent transport from an upvalley basin a confluence basin like structure was found to exist by georadar measurements underneath the present glacier in combination with high resolution age determinations based on dendrochronology and radiocarbon dating it is implied that a retreated tschierva glacier allowed vegetation growth and sediment accumulation in that basin three periods of glacier recession were detected which occurred around 9200 cal yr bp from 7450 to 6650 cal yr bp and from 6200 to 5650 cal yr bp these periods are called holocene optimum events hoe accordingly an equilibrium line rise 220 m compared to the reference period from 1960 to 1985 was inferred from digital elevation models of former glacier extents since glacier mass balance depends on summer june july august temperature and precipitation an equilibrium line altitude ela rise of 220 m implies a summer temperature increase of about 1 8 c assuming unchanged precipitation during the dated hoe alternative calculations point to probable temperature increase in a broad interval between 1 0 c taking into account a precipitation change of 250 mm a to 2 5 c with 250 mm a precipitation change supporting earlier paleotemperature estimates it is proposed that higher mean summer insolation caused a stronger seasonality during the mid holocene as compared to late holocene conditions

an improved glacial isostatic adjustment model for the british isles the glacial isostatic adjustment gia of the british isles is of interest due to the constraints that can be provided on key model parameters such as the global meltwater signal local ice sheet history and viscoelastic earth structure a number of recent studies have modelled relative sea level rsl data from this region to constrain model parameters as indicated in these studies the sensitivity of these data to both local and global parameters results in a highly non unique problem this study aims to address this inherent non uniqueness by combining a previously published british irish ice model that is based on the most recent geomorphological data with a new global ice sheet model that provides an accurate prediction of eustatic sea level change in addition constraints from global positioning system gps measurements of present day vertical land motion are considered alongside the entirety of rsl data from both great britain and ireland a model solution is found that provides a high quality fit to both the rsl data and the gps data within the range of earth viscosity values considered the optimal data model fits were achieved with a relatively thin lithosphere 71 km upper mantle viscosities in the range 4 6 1020 pa s and lower mantle viscosities 3 1022 pa s copyright 2011 john wiley sons ltd

combined use of relative and absolute dating techniques for detecting signals of alpine landscape evolution during the late pleistocene and early holocene article i nfo a combination of three relative and two absolute numerical dating techniques applied on nine soil profiles in an alpine environment located in val di rabbi trentino northern italy was used to improve the investigation methodology of alpine sites in response to climate change and to reconstruct the chronology of late pleistocene and early holocene landscape evolution the degree of podzolisation clay mineral evolution and the element mass balances of each site were investigated furthermore the stable fraction of the soil organic matter som was extracted with 10 h2o2 and 14 c dated the age of the organic residues was compared with the age of charcoal fragments found in one of the studied soils and with the age of rock boulders obtained by surface exposure dating sed with cosmogenic 10 be numerical dating and weathering characteristics of the soils showed a fairly good agreement and enabled a relative and absolute differentiation of landscape elements the combination of 14 c dating of som and sed indicated that deglaciation processes in val di rabbi were already far advanced by around 14000 cal bp and that glacier oscillations affected the highest part of the region until about 9000 cal bp the development of clay minerals is time dependent and reflects weathering intensity we found a close link between secondary clay minerals like smectite or vermiculite and soil age as obtained by the dating of the organic residues after the h2o2 treatment calculated element mass balances strongly correlated with the ages derived from 14 c measurements old soils have lost a major part of base cations up to 75 compared to the parent material fe and al which indicates a continuous high weathering intensity results of the chemical and mineralogical analyses were in good agreement with numerical dating techniques showing the dynamics of an alpine landscape within a relatively small area the combination of relative and absolute dating techniques is a promising tool for the reconstruction of landscape history in high elevation alpine areas on siliceous substrates

neoglaciation in the southern coast mountains of british columbia chronology prior to the late neoglacial maximum moraine stratigraphy and morphology radiocarbon dates from klinaklini franklin tiedemann gilbert and bridge glaciers and related information from elsewhere in the coast mountains are used to construct a chronology for glacier fluctuations the garibaldi phase of glacier expansion 6000 5000 14c years bp at the end of the early holocene xerothermic interval is indicated by overridden tree stumps the mid neoglacial tiedemann advance 3300 1900 14c years bp is represented by moraines till and meltwater sediments at three glaciers but only tiedemann glacier attained its greatest holocene extent at this time late neoglacial expansion commenced before 900 14c years bp and continued without notable interruption until glaciers achieved their maximum post pleistocene expansion during the eighteenth and nineteenth centuries evidence for the garibaldi and tiedemann events is scarce within the coast mountains because of the more extensive late neoglacial advance however correlative advances have been

evaluation of a numerical model of the british irish ice sheet using relative sea level data implications for the interpretation of trimline observations the glacial isostatic adjustment gia of the british isles is complex due to the interplay between local and non local signals a number of recent studies have modelled the gia response of the british isles using relative sea level data this study extends these previous analyses by using output from a numerical glaciological model as input to a gia model this is a necessary step towards more realistic gia models and although there have been similar studies for the major late pleistocene ice sheets this is the first study to do so for the british isles we test three reconstructions classed as minimal median and maximal in terms of their volume at maximum extent and find it is possible to obtain good data model fits the minimal reconstruction is clearly preferred by the sea level data the ice reconstructions tested were not constrained by geomorphological information of past ice extent lateral and vertical as a consequence the reconstructions extend further than much of this information suggests particularly in terms of ice thickness it is notable however that the reconstructions produce good fits to many sea level data from central mountainous regions e g scottish highlands which lends support to the suggestion that trimlines often used as an constraint on the palaeo ice surface location are in fact features formed at the transition from warm to cold based ice and so mark a minimum constraint on the ice surface altitude based on data model misfits suggestions are made for improving the ice model reconstructions however in many locations the cause of the misfit could be due to non local predominantly fennoscandian ice and so interpretation is not straightforward as a result we suggest that future analyses of this type consider models and observations for both fennoscandia and the british isles copyright 2012 john wiley sons ltd

modern uparching of the gulf coastal plain a broad doming of the gulf coastal plain between jackson mississippi and new orleans louisiana is indicated by leveling surveys carried out in 1934 1959 1964 and 1969 the progressive arching over a distance of 275 km attains a maximum average rate of 3 4 0 5 mm yr relative to jackson additional leveling in the area indicates that the observed pattern of movement could be elongate with its major axis parallel to the coast the observed uplift is consistent at least in sign with longer term trends indicated by deformed terraces in mississippi and louisiana oil gas and water withdrawal mechanisms as well as systematic leveling errors appear inadequate to explain the wavelength and magnitude of the observed elevation changes the pattern of uplift resembles that which might be expected from flexure due to sedimentary loading at the mouth of the mississippi delta simple models of flexure of a thin elastic plate overlying a viscous half space caused by sediment loading during the holocene do predict rates similar to those evidenced by leveling if relatively low mantle viscosities 3 l019 pa s 1 pa s 10 poise are used these observations may represent direct measurements of ongoing dynamic flexure at a passive continental margin

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

10 be exposure dating of the timing of neoglacial glacier advances in the ecrins pelvoux massif southern french alps alpine glacier variations are known to be reliable proxies of holocene climate here we present a terrestrial cosmogenic nuclide tcn based glacier chronology relying on 24 new be 10 exposure ages which constrain maximum neoglacial positions of four small to mid sized glaciers rateau lautaret bonnepierre and etages in the ecrins pelvoux massif southern french alps glacier advances marked by mainly lateral moraine ridges that are located slightly outboard of the little ice age lia c 1250 1860 ad maximum positions were dated to 4 25 0 44 ka 3 66 0 09 ka 2 09 0 10 ka c 1 31 0 17 ka and to 0 92 0 02 ka the 4 2 ka advance albeit constrained by rather scattered dates is to our knowledge exposure dated here for the first time in the alps it is considered as one of the first major neoglacial advance in the western alps in agreement with other regional paleoclimatological proxies we further review alpine and northern hemisphere mid to high latitude evidence for climate change and glacier activity concomitant with the 4 2 ka event the 2 1 ka advance was not extensively dated in the alps and is thought to represent a prominent advance in early roman times other neoglacial advances dated here match the timing of previously described alpine neoglacial events our results also suggest that a neoglacial maximum occurred at etages glacier 0 9 ka ago i e during the medieval climate anomaly mca c 850 1250 ad at rateau glacier discordant results are thought to reflect exhumation and snow cover of the shortest moraine boulders overall this study highlights the need to combine several sites to develop robust neoglacial glacier chronologies in order to take into account the variability in moraine deposition pattern and landform obliteration and conservation

uncertainty in the velocity between the mass center and surface of earth 1 using spectral analysis and data decimation we estimate the uncertainty in the velocity between the cumulative mass center of earth cm and geodetic sites on earth s surface knowing this velocity is crucial for evaluating space geodetic observations of continental uplift and subsidence in terms of postglacial rebound and sea level rise we find slr observations of satellite lageos to constrain the x and y components of the velocity of cm to 0 4 mm yr and the z component to 0 9 mm yr 95 confidence limits x is in the direction of 0 n0 e y of 0 n9 0 e and z of 90 n the uncertainty in z is high so that the estimate includes the independent inference made jointly using site velocities the rigid plate hypothesis and models of postglacial rebound that the true velocity of cm has a z component of 0 5 1 0 mm yr relative to that in itrf2008 uncertainty in scale rate an intermediate parameter in the determination of an itrf is 0 36 mm yr for vlbi 0 52 mm yr for slr and 0 20 mm yr for gps the scale of gps depends on that of vlbi and slr but the low gps uncertainty indicates that gps results are for the first time unbiased by changing satellite block types evidently due to newly incorporated satellite phase center variations gps constrains the velocity of cm nearly as well as slr representing a technical advance given that a gps satellite is not a sphere and responds strongly to solar radiation pressure citation argus d f 2012 uncertainty in the velocity between the mass center and surface of earth j geophys res 117 b10405 doi 10 1029 2012jb009196

post glacial sediment load and subsidence in coastal louisiana 1 sea level rise in the gulf of mexico has occurred at a rate of 1 8 2 2 mm yr during the 20th century or nearly the same as observed globally due to combined steric and water mass changes tide gauges in coastal louisiana however record a substantially larger rate of rise and while a number of causal mechanisms may be responsible their specific contribution is poorly understood using a realistic viscoelastic earth model detailed geologic parameters for south louisiana and new gps data we demonstrate that holocene sedimentary loading in the gulf and mississippi river delta is capable of contributing to 1 8 mm yr of subsidence over areas of 30 0 75 103 km2

how to evaluate model derived deglaciation chronologies a case study using antarctica abstract we address the evaluation of model derived deglaciation chronologies using observational data the study has been undertaken using the antarctic ice sheet as the focus however the issues addressed and the methods described are applicable to the evaluation of other ice sheet reconstructions within this context we present an initial database of observational data for constraining antarctic ice sheet deglaciation chronologies anticedat the database constrains present day ice sheet configuration relative sea level past ice thickness and grounding line retreat and is made available as a spreadsheet we consider the non trivial translation of an observation to model applicable constraint data through observational error models and data weighting we address the main issues that arise from evaluating modelled reconstructions generated with a glacial systems model that has like all such models inherent structural deficiencies using heterogeneous observational data the evaluation method uses observational error models to quantify model to observational misfits that also incorporate the measurement uncertainties for each data point the data point misfits are adjusted by data weighting and combined to generate a score for the model output as such different chronologies can be evaluated and compared we examine the sensitivity of the score to the different data types and associated weighting using model derived reconstructions in addition suggested reporting requirements are proposed to ensure that maximum value can be extracted from observational data

multicentury glacier fluctuations in the swiss alps during the holocene subfossil remains of wood and peat from six swiss glaciers found in proglacial fluvial sediments indicate that glaciers were smaller than the 1985 reference level and climatic conditions allowed vegetation growth in now glaciated basins an extended data set of swiss glacier recessions consisting of 143 radiocarbon dates is presented to improve the chronology of glacier fluctuations a comparison with other archives and dated glacier advances suggests 12 major recession periods occurring at 9850 9600 93008650 85508050 77007550 74506550 61505950 57005500 52004400 43003400 28002700 21501850 14001200 cal yr bp it is proposed that major glacier fluctuations occurred on a multicentennial scale with a changing pattern during the course of the holocene after the younger dryas glaciers receded to a smaller extent and prolonged recessions occurred repeatedly culminating around 7 cal kyr bp after a transition around 6 cal kyr bp weak fluctuations around the present level dominated after 3 6 cal kyr bp less frequent recessions interrupted the trend to advanced glaciers peaking with the prominent little ice age this trend is in line with a continuous decrease of summer insolation during the holocene

understanding subsidence in the mississippi delta region due to sediment ice and ocean loading insights from geophysical modeling the processes responsible for land surface subsidence in the mississippi delta md have been vigorously debated numerous studies have postulated a dominant role for isostatic subsidence associated with sediment loading previous computational modeling of present day vertical land motion has been carried out in order to understand geodetic data while the magnitudes of these measured rates have been reproduced the model parameter values required have often been extreme and in some cases unrealistic in contrast subsidence rates in the md on the 103 year timescale due to delta loading estimated from relative sea level reconstructions are an order of magnitude lower in an attempt to resolve this conflict a sensitivity analysis was carried out using a spherically symmetric viscoelastic solid earth deformation model with sediment ice and ocean load histories the model results were compared with geologic and geodetic observations that provide a record of vertical land motion over three distinctly different timescales past 80 kyr past 7 kyr and past 15 years it was found that glacial isostatic adjustment is likely to be the dominant contributor to vertical motion of the pleistocene and underlying basement present day basement subsidence rates solely due to sediment loading are found to be less than 0 5 mm yr 1 the analysis supports previous suggestions in the literature that earth rheology parameters are time dependent specifically the effective elastic thickness of the lithosphere may be 50 km on a 105 year timescale but closer to 100 km over 103 to 104 year timescales

on post glacial sea level i general theory summary modern analyses of sea level changes due to glacial isostatic adjustment gia are based on the classic sea level equation derived by farrell clark 1976 geophys j r astr soc 46 647 667 the connection between global sea level variations and changes to ocean height that is assumed within this equation breaks down in the presence of a time varying shoreline geometry we present a generalized sea level equation that overcomes this difficulty we also derive analytic expressions for and present schematic illustrations of the error in the ocean height change over finite time intervals introduced in published efforts to incorporate shoreline evolution into the theory of gia induced sea level change this comparison includes studies of shoreline migration due to either local sea level changes or the growth and ablation of marine based ice we conclude that the theories applied by johnston 1993 geophys j int 114 615 634 milne 1998 phd thesis university of toronto toronto and co workers are more accurate than the procedure advocated by peltier 1994 science 265 195 201 1998a geophys res lett 25 3955 3958 1998b rev geophys 114 615 634 although an improvement in the latter has recently been reported peltier drummond 2002 geophys res lett 29 10 1029 2001gl014273 our generalized theory is valid for any earth model in a companion paper we derive the equations necessary to treat the special case of a spherically symmetric linear viscoelastic and rotating earth and we quantify errors associated with previous work

silver and lead in high altitude lake sediments proxies for climate changes and human activities abstract high altitude lake sediments are often used as archives for environmental changes and their chemical and isotopic compositions provide significant constraints on natural and anthropogenic long term changes that have occurred in their catchment area here trace element concentrations and pb isotopes are presented for two sedimentary cores from lake blanc huez in the french alps to trace the impact of climate changes and human activities over the holocene lead and ag contents are very high and clearly dominated by input from a pb ag vein located a few meters from the lakeshore a vein that also buffers the pb isotopes mining of this vein in medieval times is recorded in the corresponding lake sediments with high ag content coupled with high pb u ratio these chemical characteristics can be used to constrain the major holocene climate changes significant advances of glaciers next to the lake produced sediments with ag and pb concentration peaks and high pb u ratios due to accelerated erosion of the pb ag vein similar to the effects of the medieval mining in contrast reduced glacier activity led to the formation of organic rich sediments with high u and as contents and low pb u ratios more generally the observed combination of chemical changes could be used elsewhere to decipher environmental changes over long periods of time

the provenance of sediments in the gulf of lions western mediterranean sea in this study we undertook a reconnaissance study of sediments provenance in the gulf of lions focusing over the last 16 ka we used geochemical and isotopic tracers to determine the source of sediments and give insight into the weathering conditions prevailing sediments samples were selected both onshore and offshore from the western eastern and central part of the gulf of lions we analyzed bulk sediments coarse and fine silt and clay fractions elemental and nd isotope compositions appeared to differ from one grain size fraction to another one these are interpreted in terms of zircon addition in the coarse silt fraction for the elemental concentrations and variable sources influences for the nd isotope compositions our results indicate that sediments in the gulf of lions mainly originated from the rhone river watershed although a contribution of saharan dust is seen in one sample influence of pyrenean small rivers is minor in these samples some sr isotope compositions shifts are interpreted as reflecting variable amounts of chemical weathering that are consistent with published paleoclimatic reconstructions

tracking rockglacier evolution in the eastern alps from the lateglacial to the early holocene abstract relict rockglaciers are distinctive indicators of past permafrost occurrence their lower limit is attributed to a former mean annual air temperature maat of below 2 c this study provides a comprehensive dataset of 34 10be exposure ages from boulders along two complex series of relict rockglaciers called tandl rockglaciers and norbert rockglaciers carinthia austria the lowest tandl rockglacier complex stabilised around 14 ka at an elevation of 1350 m a s l the lowest norbert rockglaciers 1580 and 1730 m a s l stabilised around 15 7 ka additionally in both study sites the low elevation relict rockglaciers interacted with glacial deposits of the local pre bolling glaciers gschnitz stadial glacier temperature lowering based on our data of the gschnitz rockglaciers ranges between 6 3 and 4 5 c compared to modern maat the cross cutting relationships of the rockglaciers and the glacial deposits together with the exposure ages of the rockglaciers indicate that these rockglaciers and therewith also permafrost developed shortly after or even simultaneously with retreat of the gschnitz stadial glaciers this is the first permafrost formation in the alpine areas after the retreat of the warm based last glacial maximum glaciers the tandl and norbert rockglacier lobes located at higher elevations up to about 2300 m a s l finally stabilised in the early holocene ages of several dated lobes lie between 12 10 ka at this time which corresponds to the egesen stadial younger dryas cold phase rockglaciers and glaciers co existed from the lowest position of the egesen rockglacier lobe at the tandl site 1700 m a s l a temperature lowering for the egesen stadial of 4 6 c was calculated this study highlights the potential of relict rockglacier deposits as an independent paleoclimate archive and their usefulness for reconstruction of past permafrost development and distribution in high mountain areas when they can be placed in a temporal framework

a new inference of mantle viscosity based upon joint inversion of convection and glacial isostatic adjustment data we present new profiles of mantle viscosity derived on the basis of non linear occam style joint inversions of an extensive set of data associated with mantle convection and glacial isostatic adjustment gia the convection related observables include satellite derived free air gravity harmonics the geodetically inferred excess ellipticity of the cmb and tectonic plate motions the gia constraints involve two classes of observables previously shown to be relatively insensitive to errors in the late pleistocene ice history the so called fennoscandian relaxation spectrum frs and a set of site specific decay times determined from the postglacial sea level history in hudson bay and sweden the inverted viscosity profiles show a significant three orders of magnitude increase from the upper mantle mean value of f4 10 20 pa s to a high viscosity 10 23 pa s peak at

mesolithic settlement and mobility patterns at high altitudes the site of staller sattel sts 4a south tyrol italy abstract this paper presents the results of an ongoing research aimed at reconstructing early mesolithic settlement strategies and mobility patterns at high altitudes of alpine area focusing on the interactions and possible mutual influence between human behavior and the geomorphological and environmental context due to the high altitude environment research had to face the effects of post depositional processes on anthropogenic remains investigations have been carried out on a terrace in the ackstall locality south of the staller sattel passo stalle italian austrian border central eastern alps covered by coniferous vegetation since the preboreal the terrace central with respect to the available resources and in a strategic position within a reconstructed route system conjoining different sites and adjacent hunting territories yielded several lithic findspots one of these the excavated open air site sts 4a lying at 2125 m a s l revealed human site frequentation dating at least between 7370 and 6590 cal bc human occupation was established on a forested soil subsequently buried indicated as paleo podzol stratigraphy micromorphology and artifact distribution this latter showing a ring shaped pattern suggest the preparation of the living space by manipulating the existing soil cover anthropogenic remains indicate on site activities as wood carving exploitation of rock crystal and chert for tool manufacture and the probable consumption of plants originating from lower altitudes several features some of which connected with fire use have been identified fuel was collected in the form of dead wood in the open larch and stone pine forests surrounding the site the comparison of multiscale data allowed to get insights on the living space of a mesolithic hunter gatherer camp integrating detailed data from the excavation of a single site with the wider territorial context investigated by surveys allowed to draw a multi facetted picture of early mesolithic lifeways and highlighted the potential of research on the ephemeral high altitude sites

sea level responses to rapid sediment erosion and deposition in taiwan abstract numerous studies have shown that sediment deposition can perturb sea level by several meters over millennial timescales by modifying the gravity field crustal elevation and sediment thickness relatively few studies have focused on the complementary role of erosion on sea level change despite its effects on the same quantities partly because many rapidly eroding mountains are too far from shorelines to strongly perturb sea level at the coast taiwan a mountainous island eroding rapidly within tens of km of the coast offers an opportunity to investigate the joint influences of rapid onshore erosion and rapid offshore deposition on sea level change here we develop a sediment loading history for taiwan since the previous interglacial 120 ka by compiling published erosion and deposition rate measurements and by applying a geometric marine sediment deposition and compaction model for sites without deposition rate measurements we use the resulting sediment redistribution history to drive sea level responses in a gravitationally self consistent sea level model our simulations show that the effects of rapid onshore erosion outweigh the effects of rapid offshore deposition along taiwan s east coast along the east coast of taiwan sediment redistribution induces rapid sea level fall a response that differs in sign from the coastal sea level rise induced by rapid sediment redistribution in many other river systems around the world the spatial extent of the modeled sea level fall is sensitive to the earth model particularly the effective elastic thickness of the lithosphere a sensitivity that we describe in further detail in the discussion these results suggest that sediment redistribution could have generated sea level changes of 10 m on the east coast of taiwan since 10 ka and 100 m since 120 ka this can account for some of the discrepancy between observed and modeled paleo sea level marker elevations which reduces estimates of tectonically driven rock uplift rates inferred from the elevation differences between paleo sea level markers and modeled sea level this highlights the importance of accounting for erosional unloading in interpretations of paleo sea level reconstructions and associated estimates of tectonically driven uplift rates

on postglacial sea level iii incorporating sediment redistribution we derive a generalized theory for gravitationally self consistent static sea level variations on earth models of arbitrary complexity that takes into account the redistribution of sediments the theory is an extension of previous work that incorporated into the governing equations shoreline migration due to local sea level variations and changes in the geometry of grounded marine based ice in addition we use viscoelastic love number theory to present a version of the new theory valid for spherically symmetric earth models the love number theory accounts for the gravitational deformational and rotational effects of the sediment redistribution as a first illustrative application of the new theory we compute the perturbation in sea level driven by an idealized pulse of sediment transport into the gulf of mexico we demonstrate that incorporating a gravitationally self consistent water load in this case significantly improves the accuracy of sea level predictions relative to previous simplified treatments of the sediment redistribution

a data calibrated distribution of deglacial chronologies for the north american ice complex from glaciological modeling article i nfo past deglacial ice sheet reconstructions have generally relied upon discipline specific constraints with no at tention given to the determination of objective confidence intervals reconstructions based on geophysical inversion of relative sea level rsl data have the advantage of large sets of proxy data but lack ice mechanical constraints conversely reconstructions based on dynamical ice sheet models are glaciologically self consistent but depend on poorly constrained climate forcings and sub glacial processes as an example of a much better constrained methodology that computes explicit error bars we present a dis tribution of high resolution glaciologically self consistent deglacial histories for the north american ice com plex calibrated against a large set of rsl marine limit and geodetic data the history is derived from ensemble based analyses using the 3d mun glacial systems model and a high resolution ice margin chronol ogy derived from geological and geomorphological observations isostatic response is computed with the vm5a viscosity structure bayesian calibration of the model is carried out using markov chain monte carlo methods in combination with artificial neural networks trained to the model results the calibration provides a posterior distribution for model parameters and thereby modeled glacial histories given the observational data sets that takes data uncertainty into account final ensemble results also account for fits between com puted and observed strandlines and marine limits given the model including choice of calibration parameters input and constraint data sets and vm5a earth rhe ology we find the north american contribution to mwp1a was likely between 9 4 and 13 2 m eustatic over a 500 year interval this is more than half of the total 16 to 26 m meltwater pulse over 500 to 700 years with lower values being more probable indicated by the barbados coral record fairbanks 1989 peltier and fairbanks 2006 if one assumes a 5 meter living range for the acropora palmata coral 20 ka ice volume for north america was likely 70 1 2 0 m eustatic or about 60 of the total contribution to eustatic sea level change we suspect that the potentially most critical unquantified uncertainties in our analyses are those related to model structure especially climate forcing deglacial ice margin chronology and earth rheology

radiocarbon dating of palaeosol components in moraines in lapland northern sweden abstract accurate geochronologies are the key for comparison of palaeoclimate records in order to clarify problems concerning the geochronology of glacier fluctuations we dated palaeosols in moraines in the kebnekaise mountain region of swedish lapland these palaeosols already have been dated several years ago using bulk samples of the palaeosols and yielded ages of 6180 5790 and 2750 2100 cal yr bp in an attempt to evaluate the sources of contamination associated with bulk samples these soils were re dated by using coleoptera fragments cenococcum geophilum spores humic acids and woody plant tissues the new dates reveal that the two palaeosols found within the moraines represent much longer periods of time than was previously assumed soil formation periods can be distinguished for periods 7800 7580 6300 4080 2450 2000 and 1170 740 cal yr bp these age groups point to differentiated soil formation processes resedimentation bioturbation and or cryoturbation the results show that dated terrestrial macrofossils from glacial moraines indicate climate changes that are in accordance with other proxy records in northern and central scandinavia and in certain times off phase with glacier fluctuations in southern maritime norway this throws light on possible changing interaction of forcing factors during the holocene

correlation of late quaternary moraines impact of climate variability glacier response and chronological resolution abstract the last decade has seen a global surge in the number and resolution of well dated geomorphological reconstructions of mountain glacier fluctuations and former ice sheet extents this has been facilitated by the widespread deployment of large samples of terrestrial cosmogenic nuclide dating tcnd allowing more sophisticated probability analyses for reducing the statistical uncertainty of moraine ages and testing of correlations at local regional and hemispheric scales geochronological advances in the field laboratory and on model calibration have taken place in parallel with modelling of palaeoclimate based on glacier reconstructions and of glacier sensitivity to temperature and precipitation forcing in spite of these advances basic conceptual issues remain this review questions whether the technical leap forward in dating has encouraged us to over reach our interpretive limits particularly in terms of the concept and practice of correlation we propose that to enable reliable correlation glacier chronologies should first be examined for their climatic integrity spatial coherence and chronological robustness even with excellent dating interpretive complexity remains due to complex climate signals and glacier response characteristics and to erosion censoring of the landform record all are issues which must be addressed to avoid either spurious lumping correlation or splitting differentiation of glacier chronologies and thus misinterpretation of the climatic significance of reconstructed glacier advances we suggest that the reliability of correlation is no better than the weakest link in the chain of reasoning which connects climatic fluctuations with dated landforms and sediments improved dating means that poor chronological resolution is less likely to be the limiting factor for correlation but shifts the focus onto other less quantifiable sources of uncertainty these conceptual statements are exemplified with reference to holocene glacial chronologies of contrasting mid latitude environments in southern norway iceland and new zealand

circum mediterranean fire activity and climate changes during the mid holocene environmental transition 8500 2500 cal bp a mid to late holocene synthesis of fire activity from the mediterranean basin explores the linkages among fire climate variability and seasonality through several climatic and ecological transitions regional fire histories were created from 36 radiocarbon dated sedimentary charcoal records available from the global charcoal database during the mid holocene thermal maximum around 7500 4500 cal bp charcoal records from the northern mediterranean suggest an increase in fire while records from the southern mediterranean indicate a decrease associated with wetter than present summers a north south partition between 40 and 43 n latitude is apparent in the central and western mediterranean relatively abrupt changes in fire activity are observed c 5500 5000 cal bp records of holocene fire activity appear sensitive to both orbitally forced climate changes and shorter lived excursions which may be related to north atlantic cold events possibly modulated by an nao like climate mechanism in cases wh

evidence of regional subsidence and associated interior wetland loss induced by hydrocarbon production gulf coast region usa analysis of remote images elevation surveys stratigraphic cross sections and hydrocarbon production data demonstrates that extensive areas of wetland loss in the northern gulf coast region of the united states were associated with large volume fluid production from mature petroleum fields interior wetland losses at many sites in coastal louisiana and texas are attributed largely to accelerated land subsidence and fault reactivation induced by decreased reservoir pressures as a result of rapid or prolonged extraction of gas oil and associated brines evidence that moderately deep hydrocarbon production has induced land surface subsidence and reactivated faults that intersect the surface include 1 close temporal and spatial correlation of fluid production with surficial changes including rapid subsidence of wetland sediments near producing fields 2 measurable offsets of shallow strata across the zones of wetland loss 3 large reductions in subsurface pressures where subsidence rates are high 4 coincidence of orientation and direction of displacement between surface fault traces and faults that bound the reservoirs and 5 accelerated subsidence rates near producing fields compared to subsidence rates in surrounding areas or compared to geological rates of subsidence based on historical trends subsidence rates in the gulf coast region near producing fields most likely will decrease in the future because most petroleum fields are nearly depleted alternatively continued extraction of conventional energy resources as well as potential production of alternative energy resources geopressured geothermal fluids in the gulf coast region could increase subsidence and land losses and also contribute to inundation of areas of higher elevation

tectonic control of subsidence and southward displacement of southeast louisiana with respect to stable north america 1 gps data collected between 1995 and 2006 suggest that southeast louisiana including new orleans and the larger mississippi delta are both subsiding vertically and moving southward with respect to stable north america both motions are likely related due to their common tectonic setting subsidence in the new orleans area occurs in part because it is located in the hanging wall of a large listric normal fault system that forms the northern boundary of a 7 10 km thick allochthon that is detached from stable north america southward motion of this allochthon relative to stable north america occurs at 2 2 0 6 mm yr the average subsidence rate for gps sites located on the allochthon is 5 2 0 9 mm yr relative to earth s center of mass or 7 mm yr relative to mean sea level motion of the allochthon is likely due to the gravity instability created by rapid holocene sediment deposition in the delta following continental glacial retreat and is facilitated at depth by weak salt horizons because new orleans and other communities of southeastern louisiana lie atop this active allochthon future motion of this body should be considered during rebuilding of the region following hurricanes katrina and rita

the δ18o record along the greenland ice core project deep ice core and the problem of possible eemian climatic instability over 70 000 samples from the 3029 m long greenland ice core project grip ice core drilled on the top of the greenland ice sheet summit have been analyzed for 8o a highly detailed and continuous 8o profile has thus been obtained and is discussed in terms of past temperatures in greenland we also discuss a three core stacked annual 8o profile for the past 917 years the short term 50 years variability of the annual 8o signal is found to be 1 in the holocene and estimates for the coldest parts of the last glacial are 3 or higher these data also provide insights into possible disturbances of the stratigraphic layering in the core which seems to be sound down to the onset of the eemian spectral analysis of highly detailed sequences of the profile helps determine the smoothing of the 8o signal which for the holocene ice is found to be considerably stronger than expected we suggest this is due to a process involving diffusion of water molecules along crystal boundaries in the recrystallizing ice matrix deconvolution techniques were employed for restoring with great confidence the highly attenuated annual 8o signal in the holocene we confirm earlier findings of dramatic temperature changes in greenland during the last glacial cycle abrupt and strong climatic shifts are also found within the eem sangamon interglaciation which is normally recorded as a period of warm and stable climate in lower latitudes the stratigraphic continuity of the eemian layers is consequently discussed in section 3 of this paper in terms of all pertinent data which we are not able to reconcile

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

late glacial and holocene paleoenvironmental records in the tatra mountains east central europe based on lake peat bog and colluvial sedimentary data a summary review abstract the tatra mountains are the highest massif in the carpathian mountain arc 2655 m and represent a typical alpine landscape developed in the course of pleistocene glaciations but are not glacierized today the glacial relief of the massif offers an abundance of topographic depressions cirque overdeepenings morainic closed depressions where sedimentary sequences may potentially reveal paleoenvironmental changes that may have occurred since the glaciers retreat from the last glacial maximum position 26 18 ka we present a review of late glacial and holocene sedimentary archives from the tatra mountains collected in the polish and non polish literature the data sets 40 sites included 21 lake 13 peat bog and 6 colluvial sediment sites the entire listed sediment sequence features radiometric datings or at the very least a chronological framework is inferred from the biostratigraphy the oldest sampled sedimentary sequences were dated back to the oldest dryas and were obtained from the deepest glacial lakes located in the subalpine zone up to 1700 m shallow lakes

early summer thermohaline characteristics and mixing in the western weddell sea abstract the ice station polarstern ispol cruise revisited the western weddell sea in late 2004 and obtained a comprehensive set of conductivity temperature depth ctd data this study describes the thermohaline structure and diapycnal mixing environment observed in 2004 and compares them with conditions observed more than a decade earlier hydrographic conditions on the central western weddell sea continental slope off larsen c ice shelf in late winter early spring of 2004 2005 can be described as a well stratified environment with upper layers evidencing relict structures from intense winter near surface vertical fluxes an intermediate depth temperature maximum and a cold near bottom layer marked by patchy property distributions a well developed surface mixed layer isolated from the underlying warm deep water wdw by a pronounced pycnocline and characterized by lack of warming and by minimal sea ice basal melting supports the assumption that upper ocean winter conditions persisted during most of the ispol experiment much of the western weddell sea water column has remained essentially unchanged since 1992 however significant differences were observed in two of the regional water masses the first modified weddell deep water mwdw comprises the permanent pycnocline and was less saline than a decade earlier whereas weddell sea bottom water wsbw was horizontally patchier and colder near bottom temperatures observed in 2004 were the coldest on record for the western weddell sea over the continental slope minimum temperatures were 0 4 and 0 3 c colder than during 1992 1993 respectively the 2004 near bottom temperature salinity characteristics revealed the presence of two different wsbw types whereby a warm fresh layer overlays a colder saltier layer both formed in the western weddell sea the deeper layer may have formed locally as high salinity shelf water hssw that flowed intermittently down the continental slope which is consistent with the observed horizontal patchiness the latter can be associated with the near bottom variability found in powell basin with consequences for the deep water outflow from the weddell sea

mississippi delta subsidence primarily caused by compaction of holocene strata coastal subsidence causes sea level rise shoreline erosion and wetland loss which poses a threat to coastal populations this is especially evident in the mississippi delta in the southern united states which was devastated by hurricane katrina in 2005 the loss of protective wetlands is considered a critical factor in the extensive flood damage the causes of subsidence in coastal louisiana attributed to factors as diverse as shallow compaction and deep crustal processes remain controversial current estimates of subsidence rates vary by several orders of magnitude here we use a series of radiocarbon dated sediment cores from the mississippi delta to analyse late holocene deposits and assess compaction rates we find that millennial scale compaction rates primarily associated with peat can reach 5mm per year values that exceed recent model predictions locally and on timescales of decades to centuries rates are likely to be 10 mm or more per year we conclude that compaction of holocene strata contributes significantly to the exceptionally high rates of relative sea level rise and coastal wetland loss in the mississippi delta and is likely to cause subsidence in other organic rich and often densely populated coastal plains

the importance of lateral earth structure for north american glacial isostatic adjustment abstract the isostatic response of the earth to past mass exchange between ice sheets and oceans so called glacial isostatic adjustment gia is an important geodynamic process in north america modelling gia observables provides one of the few direct methods for estimating earth viscosity structure we investigate here the requirement for anomalously high mantle viscosities to fit the relative sea level rsl data along the atlantic and gulf coasts of north america found in recent gia studies we demonstrate that this requirement is primarily related to the modelled geometry and evolution of the peripheral bulge of the laurentide ice sheet we show that a 3d earth model with a global average viscosity in the upper mantle of 0 3 10 21 pa s and 3 10 22 pa s in the lower mantle which is consistent with both the richmond gulf hudson bay relaxation time and several recent global analyses is able to produce a much improved fit to the gulf and atlantic coast rsl data relative to the 1d earth model results when no lateral structure is applied therefore we conclude that realistic implementations of lateral structure can explain the markedly different viscosity inferences obtained using 1d gia models and rsl data from different regions of north america a necessary caveat is that there are significant differences among the computed rsl curves corresponding to the three different realisations of lateral structure considered here demonstrating significant uncertainty associated with this model input

the influence of sediment isostatic adjustment on sea level change and land motion along the u s gulf coast sea level rise presents a hazard for coastal populations and the mississippi delta md is a region particularly at risk due to the high rates of land subsidence we apply a gravitationally self consistent model of glacial and sediment isostatic adjustment sia along with a realistic sediment load reconstruction in this region for the first time to determine isostatic contributions to relative sea level rsl and land motion we determine optimal model parameters earth rheology and ice history using a new high quality compaction free sea level indicator database using the optimal model parameters we show that sia can lower predicted rsl in the md area by several meters over the holocene and so should be taken into account when modeling these data we compare modeled contemporary rates of vertical land motion with those inferred using gps this comparison indicates that isostatic processes can explain the majority of the observed vertical land motion north of latitude 30 7 n where subsidence rates average about 1 mm yr however subsidence south of this latitude shows large data model discrepancies of greater than 3 mm yr indicating the importance of nonisostatic processes this discrepancy extends to contemporary rsl change where we find that the sia contribution in the delta is on the order of 10 1 mm yr we provide estimates of the isostatic contributions to 20th and 21st century sea level rates at gulf coast permanent service for mean sea level tide gauge locations as well as vertical and horizontal land motion at gps station locations near the md

a chironomid based holocene summer air temperature reconstruction from the swiss alps we developed a quantitative chironomid july air temperature inference model based on surface sediments from 81 swiss lakes and applied it to the holocene subfossil chironomid record of hinterburgsee a small subalpine lake in the northern swiss alps present day mean july air temperature of 11 3 c after smoothing to reduce the high between sample variability of inferred temperatures the reconstruction indicates july air temperatures of 10 4 10 9 c at the end of the younger dryas of 11 9 12 8 c during the early and mid holocene 11500 4000 cal bp and slightly lower temperatures of 11 5 12 0 c during the late holocene 3500 1000 cal bp a warming trend inferred for the past millennium is most likely an artifact of human impact on hinterburgsee s chironomid fauna rather than a genuine temperature signal the most prominent climatological events during the holocene were two periods of lower temperatures at c 10700 10500 cal bp and 8200 7700 cal bp and an abrupt shift to a cooler late holocene cl

holocene sea level database for the rhine meuse delta the netherlands implications for the pre 8 2 ka sea level jump abstract this paper provides the most accurate sea level index points slips for the rhine meuse delta rmd the netherlands identified amidst a wealth of data accumulated in sixty years of research following documented protocols 106 selected radiocarbon dates from peat beds from transgressed valley floor upper estuarine and back barrier lagoonal settings were first listed individually then screened in ensemble on quantified age depth position and inshore palaeotidal setting the database contains 50 slips and 56 upper limiting data points spanning a depth range of 34 to 1 5 m the dates in the database originate from dedicated sea level research which kept surface elevation and sampling depth uncertainty small and sampling of basal peat beds was favoured keeping compaction uncertainties small too the slips cover an age range of 8 8 3 0 ka bp and are available from greater rotterdam and its near offshore for upper limiting data points the coverage extends offshore tracing the rhine palaeovalley and reaches back to 11 5 ka bp the age depth data density and spatial concentration of subsets of dates allow to perform bayesian radiocarbon calibration and to reduce temporal uncertainty by 25 for the average sample 1 age uncertainty 75 cal yr when depth position and rates of relative sea level rise rslr are used to assign sequence order between 8 0 4 5 ka bp rates of rslr gradually decreased from 9 to 1 mm yr in the millennium before rates of rslr were much higher on average 10 mm yr and marked by a sea level jump between 8 45 8 2 ka bp a two phased nature of this jump starts to be resolved with local magnitudes of 1 7 0 6 m 1 first phase and 0 2 0 2 m second phase corresponding to globally averaged jumps of 2 5 m 0 9 m for the first and 0 3 0 3 m for the second phase for the pre 9 ka bp period only offshore upper limiting data points are currently available until new offshore data are gathered trends of rslr before 9 ka bp can only be estimated fed with global insights in post glacial eustasy regional estimates regarding rates of glacio isostatic adjustments and tectonic subsidence and sedimentary geological interpretations of scattered basal peat presence

holocene glacier history from alpine speleothems milchbach cave switzerland abstract mountain glaciers and their sediments are prominent witnesses of climate change responding sensitively to even small modifications in meteorological parameters even in such a classical and thoroughly studied area as the european alps the record of holocene glacier mass balance is only incompletely known here we explore a novel and continuous archive of glacier fluctuations in a cave system adjacent to the upper grindelwald glacier in the swiss alps milchbach cave became partly ice free only recently and hosts holocene speleothems four coeval stalagmites show consistent petrographic and stable isotopic changes between 9 2 and 2 0 ka which can be tied to abrupt modifications in the cave environment as a result of the closing and opening of multiple cave entrances by the waxing and waning of the nearby glacier during periods of holocene glacier advances columnar calcite fabric is characterized by 18 o values of about 8 0 indicative of speleothem growth under quasi equilibrium conditions i e little affected by kinetic effect related to forced degassing or biological processes in contrast fabrics formed during periods of glacier minima are typical of bacterially mediated calcite precipitation within caves overlain by an alpine soil cover moreover 18 o values of the bacterially mediated calcite fabrics are consistent with a ventilated cave system fostering kinetic fractionation these data suggest that glacier retreats occurred repeatedly before 5 8 ka and that the amplitudes of glacier retreats became substantially smaller afterwards our reconstruction of the upper grindelwald glacier fluctuations agrees well with paleoglaciological studies from other sites in the alps and provides a higher temporal resolution compared to traditional analyses of peat and wood remains found in glacier forefields

postglacial sea level change on a rotating earth summary we present a complete derivation of the equation governing long term sea level variations on a spherically symmetric self gravitating maxwell viscoelastic planet this new sea level equation extends earlier work by incorporating in a gravitationally self consistent manner both a time dependent ocean continent geometry and the in uence of contemporaneous perturbations to the rotation vector of the planet we also outline an e cient pseudo spectral numerical methodology for the solution of this equation and present a variety of predictions based on a suite of earth models of relative sea level rsl variations due to glacial isostatic adjustment gia these results show that the contribution to the predicted rsl signal from gia induced perturbations to the rotation vector can reach 7 8 m over the postglacial period in geographic regions where the rotationally induced signal is a maximum this result is sensitive to variations in the adopted lower mantle viscosity and is relatively insensitive to variations in the adopted lithospheric thickness we also show that the rotationally induced component of rsl change is su cient to in uence previous estimates of late holocene melting events and ongoing sea level change due to giawhich were based on a rsl theory for a non rotating earth in particular estimates of antarctic melting over the last 5 kyr based on the amplitude of sea level highstands from the australian region may require an adjustment downwards of the order of 0 5 m of equivalent sea level rise furthermore present day rates of sea level change are perturbed by as much as 0 2 mm yr 1 by the rotational component of sea level change and this has implications for gia corrections of the global tide gauge record over the period from the last glacial maximum to the present we predict a distinctly non monotonic variation in the rotation induced component of rsl this is in agreement with our previous preliminary study milne mitrovica 1996 but contrasts signi cantly with predictions presented by han wahr 1989 and bills james 1996 we demonstrate that the disagreement arises as a consequence of approximations adopted in the latter studies we furthermore refute an assertion by bills james 1996 that previously published constraints on mantle viscosity and ice sheet histories which did not incorporate a rotation induced rsl component are largely invalidated by this omission

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

space geodesy subsidence and flooding in new orleans a subsidence map of the city offers insight into the failure of the levees during hurricane katrina

holocene climate variability although the dramatic climate disruptions of the last glacial period have received considerable attention relatively little has been directed toward climate variability in the holocene 11 500 cal yr b p to the present examination of similar to50 globally distributed paleoclimate records reveals as many as six periods of significant rapid climate change during the time periods 9000 8000 6000 5000 4200 3800 3500 2500 1200 1000 and 600 150 cal yr b p most of the climate change events in these globally distributed records are characterized by polar cooling tropical aridity and major atmospheric circulation changes although in the most recent interval 600 150 cal yr b p polar cooling was accompanied by increased moisture in some parts of the tropics several intervals coincide with major disruptions of civilization illustrating the human significance of holocene climate variability c 2004 university of washington all rights reserved

reconstruction of former glacier equilibrium line altitudes based on proglacial sites an evaluation of approaches and selection of sites abstract various approaches are used to record variations in glacier activity and equilibrium line altitudes elas based on proglacial sites lacustrine and terrestrial these approaches are based on a conceptual model of glacier meltwater induced sedimentation in which the minerogenic nonorganic component of the sediments is related to the occurrence of a glacier in the catchment the principal coupling to former glacier activity and elas is common for these approaches however different methods and techniques may complement each other and both possibilities and limitations are demonstrated site selection for reconstructing variations in glacier activity elas is evaluated and critical factors are discussed rerouting of glacier meltwater streams across local watersheds in combination with proglacial sites gives a distinct on off signal for former glacier activity elas together with representative lateral moraines of known age local watersheds are important for calibrating reconstructed glacier activity elas based on a chain of proglacial lakes based on the modern analogue principle various proxies can record whenever glaciers existed in a catchment in a chain of proglacial lakes with different sensitivity to record variations in glacier activity elas these proxies can be calibrated against independent records for one site approaches however variations in glacier activity elas depend on the interpretation and sensitivity of the proxies used

holocene glacier history of bjornbreen and climatic reconstruction in central jotunheimen norway based on proximal glaciofluvial stream bank mires abstract holocene variations of bjornbreen smorstabbtinden massif west central jotunheimen are reconstructed from the lithostratigraphy of two alpine stream bank mires flooded episodically by meltwater the approach uses multiple sedimentological indicators weight loss on ignition mean grain size grain size fractions bulk density moisture content and magnetic susceptibility an a priori model of overbank deposition of suspended glaciofluvial sediments a detailed chronology based on 56 radiocarbon dates and a little ice age sedimentological analogue rapid late preboreal deglaciation was indicated by immigration of betula pubescens by 9700 cal bp an interval of at least 3000 years in the early holocene when glaciers were absent was interrupted by two abrupt episodes of glacier expansion around the time of the finse event the first at ca 8270 7900 cal bp bjornbreen i event and the second at ca 7770 7540 cal bp bjornbreen ii event neoglaciation began shortly before ca 5730 cal bp with gradual build up to the maximum of the bjornbreen iii event at ca 4420 cal bp later maxima occurred at ca 2750 cal bp bjornbreen iv event and at 1300 1260 1060 and 790 cal bp all within the bjornbreen v event glaciers were smaller than today and possibly melted away on several occasions in the late holocene ca 3950 1410 and 750 cal bp minor maxima also occurred at ca 660 and 540 cal bp within the late mediaeval warm period and the early little ice age respectively the little ice age maximum was dated to 213 25 bp ca 205 cal bp the relative magnitudes of the main glacier maxima were determined erdalen event little ice age event bjornbreen vi bjornbreen i finse event bjornbreen ii bjornbreen v bjornbreen iv bjornbreen iii these episodic events of varying magnitude and abruptness were used in conjunction with an independent summer temperature proxy to reconstruct variations in equilibrium line altitude ela and a holocene record of winter precipitation since the preboreal ela varied within a range of about 390 m and winter precipitation ranged between 40 and 160 of modern values winter precipitation variations appear to have been the main cause of these century to millennial scale holocene glacier variations

synchronous holocene climatic oscillations recorded on the swiss plateau and at timberline in the alps eight synchronous pre roman cold phases were found at 9600 9200 8600 8150 7550 6900 6600 6200 5350 4900 4600 4400 3500 3200 and 2600 2350 radiocarbon years bp by reconstructing past climate at two sites on the swiss plateau and at timberline in the alps the cooling events during the early and mid holocene represent temperature values similar to today and apparently the onset of cooling events represents a deviation from today s mean annual temperature of about 1 c and is triggered at a 1000 year periodicity at wallisellen langachermoos 440 m a former oligotrophic lake near zurich the correlation between sum mertime lake levels and the seed production of the amphi atlantic aquatic plantnajas flexilis was used to reconstruct lake levels over a 3000 year period during the first part of the holocene at lake seedorf on the western swiss plateau 609 m the sedimentological palynological and macrofossil record revealed fluctuations of lake levels for the complete holocene from lago basso in the

ups and downs of the mississippi delta during the last glacial period when sea level was low meltwater discharge drove incision of the lower mississippi valley with valley filling and delta construction during holocene sea level rise isostatic modeling shows that sediment volumes removed and replaced were sufficient to induce uplift of 9 m along valley margins followed by subsidence of the same magnitude with effects dissipating only over distances of 100 150 km along the gulf of mexico coast recognition of cyclical uplift and subsidence refutes recent interpretations of delta stability and suggests that late holocene relative sea level curves from the delta region are instead a record of subsidence of the pre holocene depocenter more broadly incised valley cutting and filling is a common fluvial response to glacioeustasy and cyclical uplift and subsidence should be common to large alluvial deltaic systems elsewhere

book reviewmoraines and varves origin genesis classification ch schluchter editor a a balkema rotterdam 1979 441 pp dfl 85 00 u s 45 00

sea level responses to erosion and deposition of sediment in the indus river basin and the arabian sea abstract changes in sea level are of wide interest because they shape the sedimentary geologic record modulate flood related hazards and reflect earth s climate one driver of sea level change is the erosion and deposition of sediment which induces changes in sea level by perturbing earth s crust gravity field and rotation axis here we use a gravitationally self consistent global model to explore how sediment erosion and deposition affected sea level during the most recent glacial interglacial cycle in the northeastern arabian sea and the indus river basin where fluvial sediment fluxes are among the highest on earth we drive the model with a widely used reconstruction of ice mass variations over the last glacial cycle and a sediment loading history that we constructed from published erosion and deposition rate measurements our modeling suggests that sediment fluxes from the indus river are large enough to produce meter scale changes in sea level near the indus delta in as little as a few thousand years these sea level perturbations are largest closest to the center of the indus delta and they grow larger over time as sediment deposition increases this implies that the elevation of sea level markers near the indus delta will be significantly altered by sediment transfer over millennial timescales and that such deformation should be accounted for in studies that use paleo sea level markers to infer past ice sheet volume or explore local processes such as sediment compaction our analysis highlights the role that massive fluvial sediment fluxes play in driving sea level changes over 1000 yr timescales from the indus river and by implication from other rivers with large sediment fluxes

on postglacial sea level summary an exact method is presented for calculating the changes in sea level that occur when ice and water masses are rearranged on the surface of elastic and viscoelastic non rotating earth models the method is used to calculate the instantaneous elastic and delayed vi scoelastic sea level changes following the partial melting of late quaternary ice sheets we find that there can be large errors in the usual assumption that changes in sea level are uniform over the ocean basins if a quantity of ice equivalent to a uniform 100 m rise in sea level melts from the laurentide and fennoscandian ice sheets then in the south pacific the instantaneous rise in sea level can be as large as 120m in the north atlantic the instantaneous rise is always less than 100 m there is a zone in the north atlantic with almost no sea level change and near greenland and norway the sea level falls rather than rises by over 100 m one thousand years after the melting a forebulge migrating towards the ice loads causes water to flow from the south pacific into the north pacific suggesting that raised beaches should occur in the south pacific the gravitational attraction of an ice mass upon a nearby ocean tends to hold sea level high in the vicinity of the ice this extra load near the ice may have a significant influence on postglacial isostatic adjustment

holocene glacier variations in central jotunheimen southern norway based on distal glaciolacustrine sediment cores abstract sediment cores from two glacier fed lakes are used to reconstruct a continuous record of glacier variations since about 10 000 cal bp in the smorstabbtinden massif of central jotunheimen southern norway particular attention is paid to the century to millennial scale pre little ice age glacial signal based on an estimated temporal resolution of 55 and 25 yr cm 1 for bovertunsvatnet and dalsvatnet respectively visible lithostratigraphic variations organic content loss on ignition calcium carbonate content magnetic susceptibility and grain size fractions especially the fine silt are used as proxy indicators of glacier presence and extent in the lake catchments following deglaciation the early holocene was characterized by generally small glaciers until a major advance the finse event peaking at approximately 8200 cal bp from 7900 to at least 5300 cal bp glaciers appear to have been absent from central jotunheimen there is evidence of glacier expansion between about 2400 and 1600 cal bp the bovertun i event and between about 1400 and 800 cal bp the bovertun ii event before reduced glacier extent during the mediaeval warm period finally the most extensive neoglacial maximum occurred during the little ice age after 500 cal bp in addition to providing a record of the broad pattern of climatically forced holocene glacier variations periodicities at 110 140 200 285 and about 500 yr have been identified uncertainties remain concerning the precise timing of events glacierization and deglacierization detection thresholds a possible mid to late holocene 5300 2500 cal bp neoglacial build up of small glaciers and shorter term decadal to century scale variations in glacier size for which more proximal sites are required

the use of hypsometry to indicate long term stability and response of valley glaciers to changes in mass transfer a simple equation is derived relating the net mass balance and hypsometric curves of a steady state valley glacier it is used to examine how valley shape is linked to disparate extents and responses of glaciers subjected to similar climatic conditions examples are given which show that area based indices e g aar for estimating the equilibrium line altitude ela may be subject to a substantial built in variance because they implicitly rely upon similarity of glacier shape and regimen over a region if accurate topographic maps are available the equation may be used to infer the regimen of modern glaciers in the form of a dimensionless ratio of net mass balance gradients alternatively if similar information is available concerning regional glacier regimen disparate extents and responses may be collectively utilized to estimate values of ela or to infer climatic influence taking glacier hypsometry into account

thermomechanical stress strain numerical modelling of deglaciation since the last glacial maximum in the adamello group rhaetian alps italy abstract deglaciated areas in the valleys of the italian alps have recently exhibited a high potential for geomorphologic hazards from diffuse deep seated gravitational deformations dsgsds caused by rock mass creep processes that can evolve into rock falls and rock avalanches a multidisciplinary approach that integrated geomorphologic surveys and stress strain numerical simulations was used to investigate the effects of the stress release that was induced by the last glacial maximum lgm in the adame valley italian alps no evidence of dsgsds has been found in this area however data are available to develop a well constrained evolutionary model of the valley deglaciation the extent and thickness of the southern extension of the adamello glacier the widest glacier in italy during its primary growth phases including those of the lgm three late glacial stages and the little ice age lia were reconstructed using glacial geological surveys and were reproduced using a finite difference stress strain sequential model spanning from the lgm to the present a thermomechanical numerical configuration was developed based on geomechanical field measurements that were collected from rock outcrops and data from laboratory tests specifically performed on intact rock samples the numerical simulations demonstrate that thermomechanical viscous behaviour cannot be neglected because the resulting strains on the slopes are significantly higher than those resulting from conventional elastoplastic behaviour the last major thermal effect in the rock masses reproduced using the model occurred from 11 5 ka until the lia the resulting displacement rates are as much as several tens of mm ka which are consistent with the absence of dsgsds in the adame valley as these rates are significantly lower than those previously obtained from dsgsds and other large landslides in the alps based on thermomechanical numerical solutions these rates should persist for the next 1000 years assuming that no variations in current climatic conditions occur

erosion under climate and human pressures an alpine lake sediment perspective we review the scientific efforts over the last decades to reconstruct erosion from continuous alpine lake sediment records we focused both on methodological issues showing the growing importance of non destructive high resolution approaches xrf core scanner as well as progresses in the understanding of processes leading to the creation of an erosion signal in lakes we distinguish continuous records from event records both provide complementary information but need to be studied with different approaches continuous regionally relevant records proved to be particularly pertinent to document regional erosion patterns throughout the holocene in particular applying the source to sink approach event based approaches demonstrated and took advantage of the strong non linearity of sediment transport in high altitude catchment areas this led to flood frequency and intensity reconstructions highlighting the influence of climate change upon flood dynamics in the mountain the combination of different record types both in terms of location high vs low elevation sedimentology high vs low terrigenous contribution and significance local vs regional is one of the main outputs of this paper it allows the establishment of comprehensive histories of nw french alps erosion but also and consequently soil dynamics and hydrological patterns throughout the holocene we also discuss the influence of glacier dynamics one of the major agents of erosion in the alps a major feature is the growing human influence upon erosion at a local scale since at least the middle of the bronze age 3500 cal bp however and according to the regional record from lake bourget only few periods of rising erosion at local scales generated a regional record that can be discriminated from wetter climatic periods among them the period between 200 bce and 400 ad appeared to be marked by a generalised rise in human triggered erosion at local scales in the northern french alps this review highlights the importance of modern high resolution and interdisciplinary studies of lake sediments in order to better understand the complex relationships between humans climate and the earth system in general we strongly argue that regional integration of data is now required to move a step further such an integration is easier with cost and time effective methods as well as after a better definition of approaches and their limits this should lead to a stronger collaboration between paleo data producers and modellers in the near future

early holocene glacier advance southern coast mountains british columbia canada abstract terrestrial and lake sediment records from several sites in the southern coast mountains british columbia provide evidence for an advance of alpine glaciers during the early holocene silty intervals within organic sediments recovered from two proglacial lakes are bracketed by ams 14 c dated terrestrial macrofossils and mazama tephra to 8780 6730 and 7940 6730 14 c yr bp 10 150 7510 and 8990 7510 cal yr bp radiocarbon ages ranging from 7720 to 7380 14 c yr bp 8630 8020 cal yr bp were obtained from detrital wood in recently deglaciated forefields of sphinx and sentinel glaciers these data together with previously published data from proglacial lakes in the canadian rockies imply that glaciers in western canada advanced during the early holocene the advance coincides with the well documented 8200 yr cold event identified in climate proxy data sets in the north atlantic region and elsewhere

global glacial isostasy and the surface of the ice age earth the ice 5g vm2 model and grace abstract the 100 kyr quasiperiodic variation of continental ice cover which has been a persistent feature of climate system evolution throughout the most recent 900 kyr of earth history has occurred as a consequence of changes in the seasonal insolation regime forced by the influence of gravitational n body effects in the solar system on the geometry of earth s orbit around the sun the impacts of the changing surface ice load upon both earth s shape and gravitational field as well as upon sea level history have come to be measurable using a variety of geological and geophysical techniques these observations are invertible to obtain useful information on both the internal viscoelastic structure of the solid earth and on the detailed spatiotemporal characteristics of glaciation history this review focuses upon the most recent advances that have been achieved in each of these areas advances that have proven to be central to the construction of the refined model of the global process of glacial isos

the alps with little ice evidence for eight holocene phases of reduced glacier extent in the central swiss alps glacially deformed pieces of wood organic lake sediments and clasts of reworked peat have been collected in front of alpine glaciers since ad 1990 the palaeoglaciological interpretation of these organic materials is related to earlier phases of glacier recession surpassing that of today s shrunken glaciers and to tree growth and peat accumulation in the valleys now occupied by the glaciers glacial transport of the material is indicated by wood anatomy incorporated silt sand and gravel particles missing bark and deformed treerings a total of 65 samples have been radiocarbon dated so far and clusters of dates provide evidence of eight phases of glacier recession 9910 9550 9010 7980 7250 6500 6170 5950 5290 3870 3640 3360 2740 2620 and 1530 1170 calibrated years bp allowing for the timelag between climatic fluctuations glacier response and vegetation colonization these recession phases may lag behind climatic changes by 100 200 years