precise radiocarbon dating of the giant kofels landslide eastern alps austria abstract the landslide of kofels located in the otz valley eastern alps austria is the largest mass movement in crystalline rock in the alps with a total volume of 3 3 km 3 previous radiocarbon dates have suggested an age of the event of 9800 100 years ago the landslide and its radiocarbon dating were used to estimate a holocene production rate for 10 be for surface exposure dating tree ring analysis and radiocarbon dating of new samples significantly refine the timing of the kofels landslide and even enable to constrain the season during which this event occurred wiggle matching analysis of six radiocarbon samples constrains the event to 9527 9498 cal bp which is slightly younger and significantly more precise than the previously established age the landslide occurred shortly after the onset of the vegetation period i e in may or june the new dating moves the kofels landslide strikingly close to the less well constrained age of the flims landslide the largest of its kind in the alps located 130 km west of kofels 9475 9343 cal bp this near synchronicity of these giant mass movements raises the question of a possible common albeit currently unknown trigger

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

cosmic ray labeling of erosion surfaces in situ nuclide production rates and erosion models a number of in situ cosmogenic radionuclides and stable nuclides have been measured in natural exposed rock surfaces with a view to study their in situ production and rock erosion rates 1 the in situ radionuclides can be used for a high resolution tomography of the erosional history of an exposed surface two stable nuclides 3he 21ne and five radionuclides 10be 26al 36cl 14c 39ar having half lives in the range of 300 1 5 106 yr half life are measurable in many rock types a prerequisite for the application of the in situ nuclides for the study of erosional histories of surfaces is a knowledge of their production rates under different irradiation conditions altitude latitude irradiation geometry and shielding relative nuclide production rates can be determined fairly accurately using the extensive available data on cosmic ray neutrons 2 absolute nuclide production rates cannot generally be predicted with any accuracy because of lack of data on excitation functions of nuclides unless some normalization is possible as was done in the case of several cosmic ray produced isotopes in the atmosphere 3 based on a recent natural calibration experiment in which erosion free surfaces exposed to cosmic radiation for 11 000 yrs were sampled the absolute production rates of 10be and 26al in quartz have been accurately estimated for mountain altitudes in sierra nevada 4 the absolute production rates of 10be and 26al in quartz can therefore be estimated fairly accurately for any given latitude and altitude some measurements of 14c in rocks of low erosion rate 5 similarly allow an estimate of its production rate attempts made to measure the in situ production rates of 3he in rocks have not yet led to a convergent production rate in view of the importance of knowing the production rates of isotopes of he ne and ar i present here theoretical estimates of their production rates based on available cross section data i discuss the information that can be extracted from the study of the in situ nuclides in rocks useful parameters characterizing the exposure history of a rock surface are 1 the effective surface exposure age and 2 the time averaged erosion rate the implications of these parameters for single and multiple nuclide studies are discussed in terms of the erosion models considered

influence of secular variation of the geomagnetic field on production rates of in situ produced cosmogenic nuclides abstract scaling factors are presented that allow a full description of the cosmic ray flux modulation during secular variation of the geomagnetic field these scaling factors are analogous to those determined in a similar work dunai t j earth planet sci lett 2000 176 157 169 that were accurate for field strengths equivalent to present day field strength but cannot accommodate field strength variations strategies to derive the relevant geomagnetic field parameters are discussed and are tested with existing production rate calibrations for 3 he a production rate of 103 4 2 atoms g olivine yr sea level and for zero cutoff rigidity was derived from calibration sites from hawaii western usa and canary islands covering the time range of 2 281 kyr

exposure dating and validation of periglacial weathering limits northwest scotland periglacial weathering limits on two mountains in northwest scotland separate zones of contrasting exposure history exposure dating of bedrock below the weathering limits gives ages consistent with late devensian deglaciation but six out of seven samples from above the weathering limits give minimum exposure ages older than late devensian ice expansion these results suggest that mountain summits stood as nunataks above the last ice sheet surface and rule out formation of weathering limits by periglacial rock breakdown since deglaciation trimming of frost debris during an ice sheet readvance or enhanced weathering prior to climatic warming during ice sheet downwastage the dating results do not preclude the possibility that weathering limits mark a former englacial boundary between passive cold based ice on mountain summits and erosive warm based ice at lower elevations although 26 al 10 be ratios for high level bedrock surfaces provide no evidence of prolonged static ice cover

response of jakobshavn isbrae greenland to holocene climate change rapid fluctuations in the velocity of greenland ice sheet gis outlet glaciers over the past decade have made it difficult to extrapolate ice sheet change into the future this significant short term variability highlights the need for geologic records of preinstrumental gis margin fluctuations in order to better predict future gis response to climate change using 10 be surface exposure ages and radiocarbon dated lake sediments we constructed a detailed chronology of ice margin fluctuations over the past 10 k y for jakobshavn isbrae greenland9s largest outlet glacier in addition we present new estimates of corresponding local temperature changes using a continuous record of insect chironomidae remains preserved in lake sediments we find that following an early holocene advance just prior to 8 ka jakobshavn isbrae retreated rapidly at a rate of 100 m yr 1 likely in response to increasing regional and local temperatures ice remained behind its present margin for 7 k y during a warm period in the middle holocene with sustained temperatures 2 c warmer than today then the land based margin advanced at least 2 4 km between a d 1500 1640 and a d 1850 the ice margin near jakobshavn thus underwent large and rapid adjustments in response to relatively modest centennial scale holocene temperature changes which may foreshadow gis response to future warming

a 10be production rate calibration for the arctic we present a baffin bay 10 be production rate calibration derived from glacial deposits in western greenland and baffin island and test our results against published 10 be calibration datasets to develop an arctic 10 be production rate our calibration comprises i 10 be measurements from moraine boulders linked to a 14 c dated moraine at jakobshavn isfjord in western greenland ii an independent and previously published 10 be production rate at jakobshavn isfjord and iii re measured 10 be concentrations from a baffin island calibration site that is included in the north eastern north america dataset combined we calculate a sea level high latitude 10 be production rate for the baffin bay region of 3 96 0 07 atoms g 1 a 1 lal stone scaling model after testing the baffin bay rate against calibration sites in norway and north eastern north america we calculate a more conservative arctic production rate of 3 96 0 15 atoms g 1 a 1 the baffin bay and arctic 10 be production rates are indistinguishable from the north eastern north america 10 be production rate 3 91 0 19 atoms g 1 a 1 and yield overall uncertainties of 2 3 7 1s these production rates reduce systematic uncertainties in 10 be based chronologies of ice margin change and allow 10 be based chronologies to be more confidently compared with high resolution climate records such as those from greenland ice cores copyright 2013 john wiley sons ltd

late glacial and holocene 10be production rates for western norway we present a new regional calibration of the 10be production rate from two well dated surfaces insouthern norway a rock avalanche with 14c dated wood and a precisely dated younger dryas moraine c

10be dating of former glacial lake naskaupi quebec labrador and timing of its discharges during the last deglaciation abstract the last deglaciation of the laurentide ice sheet in northern quebec and labrador led to the formation of several glacial lakes that drained into ungava bay and the nearby labrador sea assessing the potential impact of their drainage on ocean surface conditions and climate however is limited by the few existing age constraints on ice retreat and associated evolution of these lakes here we report 21 10be ages from shorelines and an outburst flood landform formed by lake naskaupi one of the largest glacial lakes in this region the results indicate that the lake drained from its full extent at 8300 300 a suggesting that it may have contributed to the freshwater forcing initiated by the drainage of lake agassiz ojibway that caused the 8 2 ka cold event additionally the results provide important constraints on the position of the ice margin of the labrador sector during its retreat across this region

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

deglacial sea level record from tahiti corals and the timing of global meltwater discharge the timing of the last deglaciation is important to our understanding of the dynamics of large ice sheets1 and their effects on the earth s surface2 3 moreover the disappearance of the glacial ice sheets was responsible for dramatic increases in freshwater fluxes to the oceans which probably disturbed the ocean s thermohaline circulation and hence global climate4 7 sea level increases bear witness to the melting of continental ice sheets but only two such records from barbados8 9 and new guinea10 11 corals have been accurately dated but these corals overlie active subduction zones where tectonic movements are large and often discontinuous especially in new guinea so the apparent sea level records may be contaminated by a complex tectonic component here we date fossil corals from tahiti which is far from plate boundaries and thus is likely to be tectonically relatively stable and remote from the locations of large former ice sheets the resulting record indicates a large sea level jump shortly before 13 800 calendar years bp which corresponds to meltwater pulse 1a in the barbados coral records8 9 the timing of this event is more accurately constrained in the tahiti record revealing that the meltwater pulse coincides with a short and intense climate cooling event12 15 that followed the initiation of the bolling allerod warm period12 16 but preceded the younger dryas cold event by about 1 000 years

timing of terminal pleistocene deglaciation at high elevations in southern and central british columbia constrained by 10be exposure dating abstract the cordilleran ice sheet cis covered most of british columbia and southern yukon territory at the local last glacial maximum llgm during marine oxygen isotope stage 2 however its subsequent demise is not well understood particularly at high elevations east of its ocean terminating margin we present 10be exposure ages from two high elevation sites in southern and central british columbia that help constrain the time of initial deglaciation at these sites we sampled granodiorite erratics at elevations of 2126 2230 m a s l in the marble range and 1608 1785 m a s l in the telkwa range at the western margin of the interior plateau the erratics at both sites are near ice marginal meltwater channels that delineate the local ice surface slope and thus the configuration of the ice sheet during deglaciation the locations of the erratics and their relations to meltwater channels ensure that the resulting 10be ages date cis deglaciation and not the retreat of local montane glaciers our sample sites emerged above the surface of the cis as its divide migrated westward from the interior plateau to the axis of the coast mountains two of the four samples from the summit area of the marble range yielded apparent exposure ages of 14 0 0 7 and 15 2 0 8 ka these ages are 1 8 3 0 ka younger than the well established llgm age of ca 17 ka for the puget lobe of the cis in washington state they are 1 7 ka younger than the llgm age for the puget lobe if a snow shielding correction to their uncertainty weighted mean age is applied the other two samples yielded much older apparent exposure ages 20 6 1 4 and 33 0 1 5 ka indicating the presence of inherited isotopes four samples collected from the summit area of the telkwa range in the hazelton mountains yielded well clustered apparent exposure ages of 10 1 0 6 10 2 0 7 10 4 0 5 and 11 5 1 1 ka significant present day snow cover introduces a large uncertainty in the apparent exposure ages from this site a snow shielding correction based on present day snow cover data increases the uncertainty weighted mean exposure age of the telkwa range erratics to 12 4 0 7 ka consistent with deglacial 14c ages from areas near sea level to the west our exposure ages show a thinning of the southern portion of the cis shortly after the llgm and persistence of a remnant mountain ice cap in the central coast mountains into the younger dryas chronozone our data also show that the summit area of the marble range was ice covered during the llgm the presence of an ice body of considerable dimension in north central british columbia until or possibly even after the younger dryas highlights the need for geomorphological and geochronological studies of the ice dispersal centre over the skeena mountains in northwest british columbia and the need for better understanding of the response of the cis to lateglacial climate fluctuations

west greenland and global in situ 14c production rate calibrations the in situ cosmogenic nuclide 14 c is unique compared with other nuclides because of its short half life and when combined with longer lived isotopes e g 10 be in situ 14 c can be a powerful tool for deciphering recent and complex surface exposure histories like all in situ cosmogenic nuclides quantifying earth surface processes with in situ 14 c requires a well constrained in situ 14 c production rate we present a production rate calibration from an independently dated moraine in west greenland previously used as an in situ 10 be production rate calibration site the local in situ 14 c production rate is 22 8 1 4 atoms g 1 a 1 69 28un 50 76u w 350m asl and when scaled to sea level high latitude using time dependent lal stone scaling lm we calculate a spallation only in situ 14 c production rate of 12 0 0 9 atoms g 1 a 1 and a 14 c 10 be production rate ratio of 3 1 0 2 the west greenland in situ 14 c production rate is indistinguishable from the new zealand promontory point and scottish highlands in situ 14 c production rates when combined we calculate a global production rate of 12 1 0 5 atoms g 1 a 1 lm copyright 2014 john wiley sons ltd

rapid and early deglaciation in the central brooks range arctic alaska alpine style glaciation was rare in the arctic during the last glaciation because ice sheets occupied most of the glaciated high latitudes due to the tight coupling of alpine glacier fluctuations with climate the geomorphic evidence of such fluctuations in the brooks range alaska usa presents a unique opportunity to study past climate changes in this portion of the arctic we use cosmogenic 10 be exposure dating to directly date last glacial maximum lgm terminal moraines and deglaciation in the central brooks range 10 be ages from moraine boulders indicate that the lgm culminated at ca 21 ka and was followed by substantial retreat upvalley prior to a second moraine building episode culminating at ca 17 ka subsequent rapid deglaciation occurred between ca 16 ka and 15 ka when glaciers receded to within their neoglacial limits initial deglaciation after the lgm was likely caused by ice sheet induced atmospheric circulation changes and increasing insolation brooks range glaciers largely disappeared during heinrich stadial 1 prior to significant warming in the north atlantic region during the bolling allerod but coincident with global co 2 rise glacier fluctuations during the late glacial period if any were restricted to within their neoglacial extents this new chronology suggests that ice sheet modulated atmospheric circulation and global co 2 dominate glacial climate forcings in arctic alaska

holocene environmental variability in southern greenland inferred from lake sediments abstract sediments from qipisarqo lake provide a continuous holocene paleoenvironmental record from southern greenland following deglaciation and glacio isostatic emergence of the basin from the sea 9100 cal yr b p proxies of lake paleoproductivity including biogenic silica and organic matter increased markedly until 6000 cal yr b p and thereafter remained stable over the ensuing warm three millennia subsequent decreases in these proxies most dramatically between 3000 and 2000 cal yr b p show the lake s responses to initial neoglacial cooling intervals of ameliorated limnological conditions occurred between 1300 and 900 and between 500 and 280 cal yr b p briefly interrupting the decreasing trend in productivity that culminated in the little ice age increased lake productivity during the latter half of the 20th century which reflects the limnological response to circum arctic warming still has not reached peak holocene values the neoglacial climate of the last 2000 yr includes the most rapid high amplitude environmental changes of the past nine millennia the norse thus migrated around the north atlantic ocean region in the most environmentally unstable period since deglaciation lacustrine sediment records provide a context with which to consider future environmental changes in the labrador sea region in particular any future warming will be superposed on a regional climate system that is currently exhibiting highly unstable behavior at submillennial timescales

timing of the last glaciation and subsequent deglaciation in the ruby mountains great basin usa abstract the timing of the last pleistocene glaciation in western north america is becoming increasingly well understood largely due to improved methods of obtaining numerical ages of glacial deposits and landforms among these cosmogenic radionuclide surface exposure dating has been widely applied to moraines of mountain glaciers providing the framework for understanding terrestrial climate change during and since the last glaciation in western north america during the late pleistocene the great basin of the western united states hosted numerous mountain glaciers the deposits of which can provide valuable records of past climate changes if their ages can be precisely determined in this study twenty nine cosmogenic radionuclide 10be surface exposure ages from a suite of moraines in seitz canyon western ruby mountains limit the timing of the last glacial episode in the interior great basin known as the angel lake glaciation results indicate that deposition of a terminal moraine and two recessional moraines began just prior to 20 5 ka and continued until 20 0 ka retreat from the next younger recessional moraine began at 17 2 ka and final deglaciation began at 14 8 ka these ages are broadly consistent with cosmogenic surface exposure ages from the eastern sierra nevada and the western wasatch mountains in the western and eastern extremes of the great basin respectively furthermore these ages suggest that the valley glacier in seitz canyon was at or near its maximum extent before and during the hydrologic maxima of pleistocene lakes in the great basin supporting previous suggestions that a cool and wet climate persisted in this region during the early part of the last glacial interglacial transition

early holocene history of the west greenland ice sheet and the gh 8 2 event abstract the margin of the greenland ice sheet retreated rapidly during the first few thousand years of the holocene during this period of relative warmth known as the holocene thermal maximum ice core records identify a significant short lived cooling event at approximately 8 4 8 0 ka cal yr bp the gh 8 2 event associated with a 5 7 c fall in mean annual air temperature over the centre of the ice sheet in this paper we constrain the history of the ice sheet margin in disko bugt west greenland and that of a major ice stream jakobshavns isbrae during the early holocene which incorporates the interval of the gh 8 2 event our work is based on a new relative sea level curve and minimum age estimates for the timing of deglaciation from two field sites combined with a review of previously published research from the study area we identify important differences in the chronology of ice margin recession during the early holocene most noticeably the margin of jakobshavns isbrae retreated well inland of the adjacent ice sheet at this time we conclude that the early holocene fjord stade moraines in disko bugt do not record a uniform ice sheet margin response to the gh 8 2 event rather these moraines are diachronous and formed between c 10 8 ka cal yr bp their age varying as a function of the interplay between topography and ice sheet ice stream dynamics we hypothesise that one cause for the lack of an identifiable response to the gh 8 2 event is because topographic controls dominated ice sheet behaviour at this time in lowland areas any increase in ice sheet mass balance was probably associated with an increase in calving rather than any major advance of a grounded ice sheet margin

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

glacier advances in northeastern turkey before and during the global last glacial maximum abstract our study in the basyayla valley in northeastern anatolia showed evidence of four glacier advances that built terminal and lateral moraines surface exposure dating of boulders on these moraines showed that the maximum ice extent mie was asynchronous with the global last glacial maximum lgm 22 1 4 3 thousand years ka the local mie took place at least 57 0 3 5 ka ago the extent of the basyayla glacier during this advance is not known exactly because the boulders are only preserved on a lateral moraine the next advance was prior to 41 5 2 5 ka and it descended down the valley to approximately 2320 m above sea level m a s l with a glacier length of 5 3 km during the early global lgm the basyayla glacier extended for a distance of 4 9 km down to approx 2430 m a s l the last recorded advance occurred during the global lgm this extension was 0 7 km smaller than the local mie and its terminus reached 2490 m a s l only the exposure ages of boulders in a retreat position at an altitude of approx 3045 m a s l indicate that the valley has remained ice free since the lateglacial period therefore the lateglacial extent was limited to the cirque system in the uppermost part of the catchment furthermore holocene glacier oscillations seem to be either absent or restricted to solifluction in the whole catchment and to rock glacier movements in the southern tributary of the basyayla valley system

10be and 26al production rates deduced from an instantaneous event within the dendro calibration curve the landslide of kofels otz valley austria surface exposure dating requires the knowledge of cosmogenic nuclide production rates when determining time integrated production rates the exposure ages of the calibration samples need to be accurately known the landslide of kofels austria is very well suited for this purpose it is the largest landslide in the crystalline alps of austria dating back to 7800 100 years bc ams 14c dating of buried wood which is well within the 14c dendro calibration curve exposed quartz veins were sampled from the tops of large boulders from the toe of the landslide for analysis of 10be and 26al to calculate sea level high geomagnetic latitude 60 open sky radionuclide production rates corrections were applied for altitude and latitude for shielding by surrounding mountains for sample geometry vegetation and snow cover and for sample thickness the production rates for an exposure age of 10 000 years are 5 75 0 24 10be atoms yr g sio2 and 37 4 1 9 26al atoms yr g sio2 a 26al 10be ratio of 6 52 0 43 can be calculated the influence of the geomagnetic field on these production rates has been estimated using two different geomagnetic field records our production rates should be a good approximation for the use of surface exposure dating between about 5000 and 13 000 years bp

deglaciation of coastal south western spitsbergen dated with in situ cosmogenic 10be and 14c measurements the svalbard barents ice sheet was predominantly a marine based ice sheet and reconstructing the timing and rate of its decay during the last deglaciation can inform predictions of future decay of marine based ice sheets e g west antarctica records of ice sheet change are now routinely built with cosmogenic surface exposure ages but in some regions this method is complicated by the presence of isotopic inheritance yielding artificially old and erroneous exposure ages here we present forty six 1025 be ages from bedrock n 38 and erratic boulders n 8 in southwestern spitsbergen that when paired with in situ 1427 c measurements n 5 constrain the timing of coastal deglaciation following the last glacial maximum 10be and 1428 c measurements from bedrock along a 400 m elevation transect reveal inheritance skewed 10be ages whereas 1429 c measurements constrain 400 m of ice sheet thinning and coastal deglaciation at 17 4 1 5 ka combined with three additional 10be dated coastal sites we show that the southwestern margin of the svalbard barents ice sheet retreated out of norwegian sea between 18 16 ka in situ 1432 c measurements can provide key chronological information on ice sheet response to the last termination in cases where measurements of long lived nuclides are compromised by isotopic inheritance

controls on trace element sr mg compositions of carbonate cave waters implications for speleothem climatic records abstract at two caves clamouse s france and ernesto ne italy cave drip and pool waters were collected and sampled at intervals over a 2 3 year period mg ca and sr ca concentration ratios corrected for marine aerosols are compared with those of bedrocks and in some cases aqueous leachates of soils and weathered bedrocks cave waters do not lie along mixing lines between calcite and dolomite of bedrock carbonate but typically show enhanced and covarying mg ca and sr ca four factors are considered as controlling processes 1 the much faster dissolution rate of calcite than dolomite allows for the possibility of increase of mg ca if water rock contact times are increased during drier conditions a theoretical model is shown to be comparable to experimental leachates 2 prior calcite precipitation along a flow path is a powerful mechanism for generating enhanced and covarying mg ca and sr ca ratios this mechanism requires the solution to lose co 2 into pores or caverns 3 incongruent dolomite dissolution has only limited potential and is best regarded as two separate processes of dolomite dissolution and calcite precipitation 4 selective leaching of mg and sr with respect to ca is shown to be important in leachates from ernesto where it appears to be a phenomenon of calcite dissolution in general selective leaching can occur whenever ca is sequestered into precipitates due to freezing or drying of soils or if there is derivation of excess sr and mg from non carbonate species the ernesto cave has abundant water supply which in the main chamber is derived from a reservoir with year round constant p co 2 of around 10 2 4 and no evidence of calcite precipitation in the karst above the cave two distinct but overlying trends of enhanced and covarying mg ca and sr ca away from the locus of bedrock compositions are due to calcite precipitation within the cave and at a variable drip site due to enhanced selective leaching at slow drip rates mg enhancement in the first chamber is due to a more dolomitic bedrock and longer residence times the clamouse site has a less abundant water supply and presents geochemical evidence of prior calcite precipitation both in the cave and in overlying porous dolomite dedolomitized limestone bedrock initial p co 2 values as high as 10 1 are inferred experimental incubations of clamouse soils which generated enhanced p co 2 and precipitated caco 3 had compositions similar to the karst waters calcite precipitation is inferred to be enhanced in drier conditions hydrological controls on cave water chemistry imply that the trace element chemistry of speleothems may be interpretable in palaeohydrological terms drier conditions tends to promote not only longer mean residence times enhancing dolomite dissolution and hence mg ca but also enhances degassing and calcite precipitation leading to increased mg ca and sr ca

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

the deglaciation of clyde inlet northeastern baffin island arctic canada the behaviour of ice sheets as they retreated from their last glacial maximum lgm positions provides insights into lateglacial and early holocene ice sheet dynamics and climate change thepatternofdeglaciationofthelaurentideicesheet lis inarcticfiordlandscapescannow bewelldatedusingcosmogenicexposuredating weusecosmogenicexposureandradiocarbonages to constrain the deglaciation history of clyde inlet a 120km long fiord on northeastern baffin island the lis reached the continental shelf during the lgm retreated from the coastal lowlands by 12 5 0 7ka n 3 and from the fiord mouth by 11 7 2 2ka n 4 rapid retreat from the outer fiord occurred 10 3 1 3ka n 6 with the terminus reaching the inner fiord shortly after 9 4ka n 2 where several moraine systems were deposited between ca 9 4 and ca 8 4ka these moraines represent fluctuations of the lis during the warmest summers since the last interglaciation and this suggests that the ice sheet was responding to increased snowfall before retreating from the head of clyde inlet the lis margin fluctuated at least twice between ca 7 9 and ca 8 5ka possibly in response to the 8 2ka cold event copyright 2006 john wiley sons ltd

the importance of independent chronology in integrating records of past climate change for the 60 8 ka intimate time interval this paper provides a brief overview of the most common dating techniques applied in palaeoclimate and palaeoenvironmental studies including four radiometric and isotopic dating methods radiocarbon 230th disequilibrium luminescence cosmogenic nuclides and two incremental methods based on layer counting ice layer varves for each method concise background information about the fundamental principles and methodological approaches is provided we concentrate on the time interval of focus for the intimate integrating ice core marine and terrestrial records community 60 8 ka this dating guide addresses palaeoclimatologists who aim at interpretation of their often regional and local proxy time series in a wider spatial context and therefore have to rely on correlation with proxy records obtained from different archives from various regions for this reason we especially emphasise scientific approaches for harmonising chronologies for sophisticated and robust proxy data integration in this respect up to date age modelling techniques are presented as well as tools for linking records by age equivalence including tephrochronology cosmogenic 10be and palaeomagnetic variations finally to avoid inadequate documentation of chronologies and assure reliable correlation of proxy time series this paper provides recommendations for minimum standards of uncertainty and age datum reporting

response of a marine terminating greenland outlet glacier to abrupt cooling 8200 and 9300 years ago greenland s largest outlet glacier using 10 be surface exposure ages and 14 c dated lake sediments our chronology of ice margin change demonstrates that jakobshavn isbrae advanced to deposit moraines in response to abrupt cooling recorded in central greenland ice cores ca 8 200 and 9 300 years ago while the rapid dynamically aided retreat of many greenland outlet glaciers in response to warming is well documented these results indicate that marine terminating outlet glaciers are also able to respond quickly to cooling we suggest that short lag times of high ice flux margins enable a greater magnitude response of marine terminating outlets to abrupt

devising quality assurance procedures for assessment of legacy geochronological data relating to deglaciation of the last british irish ice sheet this contribution documents the process of assessing the quality of data within a compilation of legacy geochronological data relating to the last british irish ice sheet a task undertaken as part of a larger community based project britice chrono that aims to improve understanding of the ice sheet s deglacial evolution as accurate reconstructions depend on the quality of the available data some form of assessment is needed of the reliability and suitability of each given age s in our dataset we outline the background considerations that informed the quality assurance procedures devised given our specific research question we describe criteria that have been used to make an objective assessment of the likelihood that an age is influenced by the technique specific sources of geological uncertainty when these criteria were applied to an existing database of all geochronological data relating to the last british irish ice sheet they resulted in a significant reduction in data considered suitable for synthesis the assessed data set was used to test a bayesian approach to age modelling ice stream retreat and we outline our procedure that allows us to minimise the influence of potentially erroneous data and maximise the accuracy of the resultant age models

a cosmogenic 10be chronology for the local last glacial maximum and termination in the cordillera oriental southern peruvian andes implications for the tropical role in global climate abstract resolving patterns of tropical climate variability during and since the last glacial maximum lgm is fundamental to assessing the role of the tropics in global change both on ice age and sub millennial timescales here we present a10be moraine chronology from the cordillera carabaya 14 3 s a sub range of the cordillera oriental in southern peru covering the lgm and the first half of the last glacial termination additionally we recalculate existing 10be ages using a new tropical high altitude production rate in order to put our record into broader spatial context our results indicate that glaciers deposited a series of moraines during marine isotope stage 2 broadly synchronous with global glacier maxima but that maximum glacier extent may have occurred prior to stage 2 thereafter atmospheric warming drove widespread deglaciation of the cordillera carabaya a subsequent glacier resurgence culminated at 16 100 yrs followed by a second period of glacier recession together the observed deglaciation corresponds to heinrich stadial 1 hs1 18 000 14 600 yrs during which pluvial lakes on the adjacent peruvian bolivian altiplano rose to their highest levels of the late pleistocene as a consequence of southward displacement of the inter tropical convergence zone and intensification of the south american summer monsoon deglaciation in the cordillera carabaya also coincided with the retreat of higher latitude mountain glaciers in the southern hemisphere our findings suggest that hs1 was characterised by atmospheric warming and indicate that deglaciation of the southern peruvian andes was driven by rising temperatures despite increased precipitation recalculated 10be data from other tropical andean sites support this model finally we suggest that the broadly uniform response during the lgm and termination of the glaciers examined here involved equatorial pacific sea surface temperature anomalies and propose a framework for testing the viability of this conceptual model

the deglaciation of coastal areas of southeast greenland large marine terminating glaciers around the margins of the greenland ice sheet have retreated accelerated and thinned over the last two decades relatively little is known about the longer term behaviour of the greenland ice sheet yet this information is valuable for assessing the significance of modern changes we address this by reporting 11 new beryllium 10 10be exposure ages from previously uninvestigated coastal areas across southeast greenland the new ages are combined with existing data from the region to assess the timing of glacier retreat after the last glacial maximum the results show that deglaciation occurred first in the north of the region 68 n and progressed southwards this north south progression is attributed to the influence of the warm irminger current on the ice margin areas in the south of the region were isolated from the warm waters by the shallow bathymetry of the continental shelf this demonstrates that oceanographic forcing paced the deglaciation of southeast greenl

glacier extent during the younger dryas and 8 2 ka event on baffin island arctic canada greenland ice cores reveal that mean annual temperatures during the younger dryas yd cold interval about 12 9 to 11 7 thousand years ago ka and the 150 year long cold reversal that occurred 8 2 thousand years ago were 15 and 3 to 4 c colder than today respectively reconstructing ice sheet response to these climate perturbations can help evaluate ice sheet sensitivity to climate change here we report the widespread advance of laurentide ice sheet outlet glaciers and independent mountain glaciers on baffin island arctic canada in response to the 8 2 ka event and show that mountain glaciers during the 8 2 ka event were larger than their yd predecessors in contrast to the wintertime bias of yd cooling we suggest that cooling during the 8 2 ka event was more evenly distributed across the seasons

rapid early holocene ice retreat in west greenland abstract the possible demise of the greenland ice sheet and its effect on global sea level rank among the most serious climate threats to society to improve our knowledge about the future behaviour of the ice margin we studied the ice sheet s response to early holocene warming in west greenland using 47 cosmogenic 10 be exposure ages 26 optically stimulated luminescence ages as well as 15 new and 28 previously published radiocarbon ages paired bedrock and boulder ages show that the entire area was covered by warm based ice during the last glacial maximum lgm although glacial erosion was insufficient to completely remove the upper rock surface containing 10 be inherited from a previous period of exposure in bedrock samples above an elevation of 800 m our compilation of 10 be and 14 c ages demonstrates that the ice sheet retreated from the outer coast to the present ice margin between c 11 4 and 10 4 cal ka bp in the godthabsfjord system and between 10 7 0 6 and 10 1 0 4 ka ago in buksefjord whereas the coast at sermilik became ice free at c 10 5 cal ka bp we find no significant changes in the retreat rates between the deep godthabsfjord system and the buksefjord sermilik region which is characterized by only a few narrow and shallow fjords however deglaciation was initiated c 700 900 years earlier in the godthabsfjord system indicating that the deep fjords probably triggered land based deglaciation by dynamic ice loss leading to an overall rapid early holocene ice retreat and drawdown of the ice sheet in west greenland these results demonstrate that even if there was a topographic control on the onset of deglaciation fast ice retreat is not restricted to deep fjord systems but may occur independently of the topographic setting

age of the berlin moraine complex new hampshire usa and implications for ice sheet dynamics and climate during termination 1 at its late pleistocene maximum the laurentide ice sheet was the largest ice mass on earth and a key player in the modulation of global climate and sea level at the same time this temperate ice sheet was itself sensitive to climate and high magnitude fluctuations in ice extent reconstructed from relict glacial deposits reflect past changes in atmospheric temperature here we present a cosmogenic 10be surface exposure chronology for the berlin moraines in the white mountains of northern new hampshire usa which supports the model that deglaciation of new england was interrupted by a pronounced advance of ice during the bolling allerod together with recalculated 10be ages from the southern new england coast the expanded white mountains moraine chronology also brackets the timing of ice sheet retreat in this sector of the laurentide in conjunction with existing chronological data the moraine ages presented here suggest that deglaciation was widespread during heinrich stadial 1 event 18 14 7 ka despite apparently cold marine conditions in the adjacent north atlantic as part of the white mountains moraine system the berlin chronology also places a new terrestrial constraint on the former glacial configuration during the marine incursion of the st lawrence river valley north of the white mountains

contributions and unrealized potential contributions of cosmogenic nuclide exposure dating to glacier chronology 1990 2010 abstract this paper reviews the application of cosmogenic nuclide exposure dating to glacier chronology exposure dating of glacial landforms has made an outsize impact on this field because the technique filled an obvious need that had already been recognized by glacial geologists by now hundreds of studies have used cosmogenic nuclide exposure dating to date glacial deposits and in fact it is rare to find a study of glacial geology or glacier chronology or any paleoclimate synthesis that makes use of such studies that does not involve exposure dating these developments have resulted in major contributions to glacier chronology and paleoclimate in particular i reconstructing antarctic ice sheet change ii establishing the chronology of late pleistocene and holocene glacier change in mountain regions where it was previously unknown iii establishing the broad chronological outlines of mountain glaciations prior to the last glacial maximum and iv gaining insight into subglacial erosional processes through the observation that many glaciated surfaces preserve cosmogenic nuclide inventories from long past ice free periods as well as the present one an important potential future contribution will be the application of the large data set of exposure dated glacier chronologies to better understand global and regional climate dynamics during lateglacial and holocene millennial scale climate changes however this contribution cannot be realized without significant progress in two areas i understanding and accounting for geologic processes that cause apparent exposure ages on glacial landforms to differ from the true age of the landform and ii minimizing systematic uncertainties in exposure ages that stem from cosmogenic nuclide production rate estimates and scaling schemes at present there exists an enormous data set of exposure ages on glacial deposits but these data cannot be used to their full potential in paleoclimate syntheses due to an inadequate understanding of geologic scatter and production rate uncertainties the intent of this paper is to highlight this situation and suggest some strategies for realizing this potential

rapid early holocene retreat of a laurentide outlet glacier through an arctic fjord marine terminating outlet glaciers control the stability of ice sheets exposure ages and radiocarbon dates show that an arctic outlet glacier of the laurentide ice sheet rapidly retreated about 9 500 years ago and imply strong feedbacks between bathymetry and ice movement

using proglacial threshold lakes to constrain fluctuations of the jakobshavn isbrae ice margin western greenland during the holocene abstract the future response of the greenland ice sheet gis and its potential contribution to sea level rise are uncertain rapid changes of greenland s outlet glaciers over the past decade have made it difficult to extrapolate ice sheet change into the future this significant short term variability highlights the need for longer term geologic e g holocene records of ice margin fluctuations however a major challenge with reconstructing the gis during the holocene stems from it having been smaller than it is at present thus traditional glacial geologic approaches are not suitable we use radiocarbon dated sediment sequences from seven proglacial threshold lakes spanning 50 km of the western gis margin near jakobshavn isbrae to constrain the timing of early holocene deglaciation the duration that this sector of the western gis was smaller than its present configuration and the timing of its advance during neoglaciation our reconstructions suggest deglaciation 7300 cal yr bp minimum ice extent 6000 5000 cal yr bp and smaller than present ice configuration until at least 2300 cal yr bp for the ice margin south of jakobshavn isbrae and until 400 cal yr bp for the ice margin north of jakobshavn isbrae one relatively large proglacial lake that became briefly ice free during the middle holocene lies in a catchment that likely extends 10s of km inland beneath the gis suggesting significant middle holocene retreat of this portion of the gis the overall pattern of ice sheet change is inconsistent with existing ice sheet model reconstructions for this region but is consistent with numerous paleoclimate proxy and relative sea level data these continuous lacustrine records corroborate but provide closer age control than existing non continuous records of radiocarbon dated reworked bivalves from historical moraines in the region reconstructing ice margin change from proglacial threshold lakes is one of few approaches with the potential to constrain smaller than present ice sheet extent

holocene deglaciation of marie byrd land west antarctica surface exposure ages of glacial deposits in the ford ranges of western marie byrd land indicate continuous thinning of the west antarctic ice sheet by more than 700 meters near the coast throughout the past 10 000 years deglaciation lagged the disappearance of ice sheets in the northern hemisphere by thousands of years and may still be under way these results provide further evidence that parts of the west antarctic ice sheet are on a long term trajectory of decline west antarctic melting contributed water to the oceans in the late holocene and may continue to do so in the future

holocene glacial history of svalbard status perspectives and challenges abstract we synthesize the current understanding of glacier activity on svalbard from the end of the late pleistocene 12 000 yrs before present to the end of the little ice age c 1920 ad our glacier history is derived from the svalhola database the first compilation of holocene geochronology for svalbard and the surrounding waters including over 1 800 radiocarbon terrestrial cosmogenic nuclide and optically stimulated luminescence ages data have been categorized by geological setting uniformly re calibrated quality assessed and ultimately used to constrain glacier fluctuations deglaciation ice free conditions glacier re advances and ice marginal positions we advance existing knowledge by mapping the extent and distribution of ice cover during the holocene glacial maximum and the glacial minimum as well as present retreat rates and percentages within early holocene fjord systems throughout the holocene svalbard glaciers have responded to a varying combination of climatic environmental and dynamic driving factors which influence both the extent and behavior of ice margins we discuss the complexities of glacier systems and their dynamics in response to changes in climate this review provides a holistic state of the art of holocene glaciers on svalbard suitable for orienting future works which address gaps in our current knowledge

age of the fjord stade moraines in the disko bugt region western greenland and the 9 3 and 8 2 ka cooling events abstract retreat of the western greenland ice sheet during the early holocene was interrupted by deposition of the fjord stade moraine system the fjord stade moraine system spans several hundred kilometers of western greenland s ice free fringe and represents an important period in the western greenland ice sheet s deglaciation history but the origin and timing of moraine deposition remain uncertain here we combine new and previously published 10 be and 14 c ages from disko bugt western greenland to constrain the timing of fjord stade moraine deposition at two locations 60 km apart at jakobshavn isfjord the northern of two study sites we show that jakobshavn isbrae advanced to deposit moraines ca 9 2 and 8 2 8 0 ka in southeastern disko bugt the ice sheet deposited moraines ca 9 4 9 0 and 8 5 8 1 ka our ice margin chronology indicates that the greenland ice sheet in two distant regions responded in unison to early holocene abrupt cooling 9 3 and 8 2 ka as recorded in central greenland ice cores although the timing of fjord stade moraine deposition was synchronous in jakobshavn isfjord and southeastern disko bugt within uncertainties we suggest that jakobshavn isbrae advanced while the southeastern disko bugt ice margin experienced stillstands during the 9 3 and 8 2 ka events based on regional geomorphology and the distribution of 10 be ages at each location the contrasting style of ice margin response was likely regulated by site specific ice flow characteristics jakobshavn isbrae s high ice flux results in an amplified ice margin response to a climate perturbation both warming and cooling whereas the comparatively low flux sector of the ice sheet in southeastern disko bugt experiences a more subdued response to climate perturbations our chronology indicates that the western greenland ice sheet advanced and retreated in concert with early holocene temperature variations and the 9 3 and 8 2 ka events although brief were of sufficient duration to elicit a significant response of the western greenland ice sheet

the new north american varve chronology a precise record of southeastern laurentide ice sheet deglaciation and climate 18 2 12 5 kyr bp and correlations with greenland ice core records new glacial varve records from long cores combined with records from key surface exposures and new radiocarbon ages have allowed the correction consolidation expansion and calibration of ernst antevs9 original new england varve chronology nevc in the connecticut valley of new england u s a the varve records have been reformulated with corrections and a new numbering system as the new north american varve chronology navc which is a continuous 5659 yr varve sequence that spans most of the last deglaciation 18 200 12 500 yr bp in the northeastern united states rates of ice recession for separate intervals terminated by abrupt glacial stillstands and readvances have been determined for western new england ice recession history is coupled to varve thickness changes that depict changes in meltwater production in the connecticut valley and show the relationship of changes in ablation rate summer climate variation to glacial readvances and periods of halted and rapid ice recession up to 300 m yr comparison of varve thickness records to greenland ice core climate records show that after 15 000 yr bp climate changes of sub century and longer scales recorded in both records appear identical and synchronous after 15 000 yr bp therefore there was a link between north atlantic climate and marginal processes of the southeastern sector of the laurentide ice sheet lis prior to 15 000 yr bp when the lis was closer to an equilibrium condition retreat rates were generally lower and changes in varve thickness and ablation were more subtle but can still be linked to ice sheet activity only weak relationships between varve thickness changes and greenland climate are evident suggesting that changes in the southeastern lis during this time may have been significantly influenced by climate patterns unique to the north american continent or ice dynamics

precise cosmogenic 10be measurements in western north america support for a global younger dryas cooling event the inner titcomb lakes moraine in the wind river mountains wyoming has been dated with a precision of 5 using accelerator mass spectrometric measurements of cosmogenic 10be in surface samples from nine boulders resting on its crest the age of this moraine is 11 4 0 5 to 13 8 0 6 ka the range in age is due to the uncertainty in the 10be production rate and uncertainties in rock erosion rate and shielding of cosmic rays by snow additional exposure ages on bedrock and boulder surfaces that are stratigraphically younger and older than the inner titcomb lakes moraine conform with this age the exposure ages of the inner titcomb lakes moraine overlap the north atlantic younger dryas event 12 8 0 2 to 11 5 0 3 ka

topographical evolution and glaciation history of south greenland constrained by paired 26al 10be nuclides abstract the pattern of cosmogenic nuclide inheritance within bedrock surfaces in previously glaciated regions can be used to assess the efficiency of glacial erosion and constrain topographic evolution here we present fifty new in situ cosmogenic 10be and 26al pairs in bedrock and boulder erratics from south greenland the data demonstrate rapid retreat of the south greenland ice sheet in the early holocene and a clear gradient in cosmogenic nuclide inheritance in bedrock with elevation sites 800 m above sea level m a s l generally show limited or no nuclide inheritance exposure from before the last glaciation in contrast the nuclide inheritance in samples from sites at higher elevations varies from negligible to 90 kyr of exposure before the last glaciation depending on the topographic setting our results suggest that steering of ice into troughs led to substantial erosion 2 6 m in the troughs over the last glacial cycle even at elevations above 1500 m a s l while bedrock on summit flats at similar elevations experienced much less erosion inverse markov chain monte carlo mcmc modelling of the nuclide inventories further indicates that selective linear erosion developed 1 myr ago at the summit flat closest to the present ice margin and effectively limited the subsequent erosion to 2 6 m erosion of the redekammen ridge some 40 km from the present ice margin was slightly more efficient over the last 1 myr indicating that selective linear erosion is less pronounced or developed later here than at the summit flats long term ice cover histories are generally less well constrained than the erosion histories the results suggest that the summit flats were possibly ice covered during large parts of the last 1 myr and experienced minimal erosion during this interval but it is also possible that they were only covered by ice during the coldest parts of the glacial periods and that a cover of regolith or overlying rock was stripped off during one of the latest major glaciations although inverse modelling cannot distinguish between these scenarios we identify the more likely ice cover scenarios for each site based on the geological setting and surface characteristics

geochronological osl and geomorphological investigations at the presumed frankfurt ice marginal position in northeast germany abstract the weichselian frankfurt ice marginal position in northeast germany has been critically discussed in the past owing to weak morphological evidence and a lack of clear sedimentological records this study aims to contribute to this discussion with new geochronological and geomorphological results apart from very few cosmogenic exposure ages the time frame is to date still based on long distance correlation with radiocarbon chronologies we selected a study site in a key position regarding the classic location of the frankfurt ice marginal position and the recently described arcuate ridge structures on the barnim plateau for the first time we present optically stimulated luminescence osl ages of quartz from glaciofluvial deposits for this weichselian phase our results indicate an advance of the scandinavian ice sheet sis at around 34 1 4 6 ka this is in agreement with osl ages from sandur deposits at the brandenburg ice marginal position located farther south and could also be correlated with the klintholm advance in denmark the subsequent meltdown phase lasted until around 26 3 3 7 ka during the meltdown phase a minor oscillation of the sis caused the formation of the recently described arcuate ridges on the barnim till plain recalculated surface exposure ages of glacigenic boulders with an updated global production rate indicate a landscape stabilization phase at around 22 7 1 6 ka which is in agreement with our ages a phase of strong aeolian activity has been dated with osl to 1 0 1 ka this may have been triggered by human activities that are documented in this region for the medieval period

early holocene palaeoceanography and deglacial chronology of disko bugt west greenland two new cores from disko bugt a large marine embayment in west greenland are used to assess the deglacial chronology and palaeoceanography of the area during the early holocene deglaciation of the main part of disko bugt is directly dated for the first time to a minimum of ca 10 2 ka cal bp by this time the jakobshavn isbrae ice stream had retreated to the eastern margins of disko bugt initial deglaciation took place before the relatively warm west greenland current wgc was initiated a strengthening in the wgc is identified from ca 9 2 ka cal bp accompanied by retreat of the ice stream to a shallow bank immediately west of the present day jakobshavn isfjord while in this position the calving and melting ice stream produced large volumes of sediment and meltwater the large volumes of meltwater prevented the relatively warm waters of the wgc reaching the eastern margins of disko bugt the ice stream remained grounded on this bank for over a thousand years until ca 7 9 ka cal bp when reduced sedimentation rates and an increase in boreal fauna point to its retreat inside the present day fjord system

the age and extent of tropical alpine glaciation in the cordillera blanca peru based on new 10 be data for moraines in the cordillera blanca of central peru we have calculated model ages of three sets of pleistocene glacial moraines in order of decreasing age these are the cojup rurec and laguna baja moraines the oldest moraines occur at the lowest elevations and yield dates of 400 ka pre dating the last interglacial and demonstrating that maximum ice volumes occurred during previous glacial periods and not at the end of the last glacial our new data from the younger moraines indicate that the end of the last glacial cycle comprised two separate advances at ca 29 ka and ca 16 5 ka each reflecting significant 4 c tropical of cooling at 10 s these data combined with published records from the laurentide ice sheet indicate that climate instabilities associated with the close of the last glacial were likely global and synchronous in nature copyright 2005 john wiley sons ltd

constraining holocene 10be production rates in greenland the absence of a production rate calibration experiment on greenland has limited the ability to link 10be exposure dating chronologies of ice margin change to independent records of rapid climate change we use radiocarbon age control on holocene glacial features near jakobshavn isbrae western greenland to investigate 10be production rates the radiocarbon chronology is inconsistent with the 10be age calculations based on the current globally averaged 10be production rate calibration data set but is consistent with the 10be production rate calibration data set from north eastern north america which includes a calibration site nearby on north eastern baffin island based on the best dated feature available from the jakobshavn isbrae forefield we derive a 10be production rate value of 3 98 0 24 atoms g a 1 using the st scaling scheme which overlaps with recently published reference 10be production rates we suggest that these 10be production rate data or the very similar data from north eastern north america are used on greenland copyright 2011 john wiley sons ltd

trough geometry was a greater influence than climate ocean forcing in regulating retreat of the marine based irish sea ice stream marine terminating ice streams are a major component of contemporary ice sheets and are likely to have a fundamental influence on their future evolution and concomitant contribution to sea level rise to accurately predict this evolution requires that modern day observations can be placed into a longer term context and that numerical ice sheet models used for making predictions are validated against known evolution of former ice masses new geochronological data document a stepped retreat of the paleo irish sea ice stream from its last glacial maximum limits constraining changes in the time averaged retreat rates between well defined ice marginal positions the timing and pace of this retreat is compatible with the sediment landform record and suggests that ice marginal retreat was primarily conditioned by trough geometry and that its pacing was independent of ocean climate forcing we present and integrate new luminescence and cosmogenic exposure ages in a spatial bayesian sequence model for a north south 173km transect of the largest marine terminating ice stream draining the last british irish ice sheet from the south and east coasts of ireland initial rates of ice margin retreat were as high as 300 600 m a 1 but retreat slowed to 26 m a 1 as the ice stream became topographically constricted within st george s channel a sea channel between ireland to the west and great britain to the east and then stabilized retreating at only 3 m a 1 at the narrowest point of the trough during the climatic warming of greenland interstadial 2 gi 2 23 3 22 9 ka later retreat across a normal bed slope during the cooler conditions of greenland stadial 2 was unexpectedly rapid 152 m a 1 we demonstrate that trough geometry had a profound influence on ice margin retreat and suggest that the final rapid retreat was conditioned by ice sheet drawdown dynamic thinning during stabilization at the trough constriction which was exacerbated by increased calving due to warmer ocean waters during gi 2

paired bedrock and boulder 10be concentrations resulting from early holocene ice retreat near jakobshavn isfjord western greenland we measured in situ cosmogenic 10 be in 16 bedrock and 14 boulder samples collected along a 40 km transect outside of and normal to the modern ice margin near sikuijuitsoq fjord in central west

10be cosmic ray exposure dating of moraines and rock avalanches in the upper romanche valley french alps evidence of two glacial advances during the late glacial holocene transition abstract cosmic ray exposure cre dating of moraines allow glacier fluctuations and past climate change reconstructions in the french alps there is a lack of moraine dating for the late glacial holocene transition period here we present a chronology of glacier advances in the upper romanche valley french alps massif des ecrins based on 10 be cre dating cre ages of moraines of 13 0 1 1 ka and 12 4 1 5 ka provide evidence for two stages of glacial advance or standstill at the end of the late glacial the cre dating of a rock avalanche deposit at 12 2 1 5 ka is attributed to post glacial debuttressing and reveals rapid deglaciation at the end of the late glacial a cre age of 7 1 0 7 ka of a second mass wasting whose triggering factor is unidentified so far indicates that up to an altitude of 2300 m a s l the valley was ice free as of 7 kyr at the latest the re evaluation of 21 moraine 10 be cre ages from nine glacial valleys across the alps shows multiple glacial advances occurring at the late glacial holocene transition these results lead to a re evaluation of the importance of cooling events during the allerod and the younger dryas in the alps

holocene ice recession at polygon spur reedy glacier antarctica the holocene history of outlet glaciers affords information on the behavior and mechanisms controlling the extent of the east antarctic ice sheet here we present both new radiocarbon and recalcul

10be surface exposure ages on the late pleistocene and holocene history of linnebreen on svalbard abstract arctic glaciers were sensitive to past changes in high latitude winter precipitation and summer temperature here we develop a late pleistocene to holocene history for linnebreen linne glacier in western svalbard using 10 be surface exposure ages on isolated erratic and moraine boulders we show that linnebreen had separated from the larger ice sheet over svalbard and was retreating up valley around the start of the younger dryas cold period we attribute this retreat during a cold period on svalbard to moisture starvation of linnebreen from advanced sea ice and or elevated shortwave boreal summer insolation that overwhelmed any reduction in sensible heat after an ice free period during the early to middle holocene linnebreen reformed sometime after 4 6 0 2 ka and was at a position roughly equivalent to its little ice age lia maximum extent before it began to retreat at 1 6 0 2 ka comparison with calibrated 14 c dates from three other glaciers could suggest that this period of ice retreat at 1 6 ka could be regional in extent linnebreen occupied the pre lia moraine when there was an increased ratio of cold arctic sourced relative to warm atlantic sourced waters around svalbard and advanced sea ice the retreat of linnebreen at 1 6 ka was concurrent with the increased presence of warm atlantic waters around svalbard and attendant sea ice retreat these coincident changes in ocean temperatures sea ice extent and linnebreen moraine age could imply a climatic forcing of the pre lia advance and retreat of linnebreen summer temperatures rather than changes in precipitation would then be dominant in driving ice retreat although the possibility of stochastic glacier margin variability cannot be excluded our data therefore suggest that linnebreen may have responded differently to past changes in sea ice extent that could depend on the background climate state deglacial climate vs late holocene climate which highlights the complexity in climatic controls on arctic glaciers

timing of the younger dryas glacial maximum in western norway this study precisely constrains the timing of the younger dryas yd glacial maximum in south western norway by utilizing sediment records from lake basins two of the basins located on the distal side of the mapped herdla halsnoy moraine received meltwater directly from the ice sheet only when the ice margin reached its maximum extent during the yd in the cores the ice maximum is represented by well defined units with meltwater deposits dominantly laminated silt plant macrofossils in the sediment sequences are common and we obtained 18 radiocarbon ages from one of the cores by applying bayesian age depth modelling we obtained a precise date for this meltwater event and thereby also for the timing of the yd glacial maximum we conclude that the ice sheet advance culminated at the halsnoy moraine at 11 760 120 cal a bp and that the ice margin stayed in this position for 170 120 years the subsequent retreat started at 11 590 100 cal a bp i e close to the yd holocene boundary withdrawal was probably triggered by abrupt climatic warming at this time copyright 2011 john wiley sons ltd

simulation of holocene cooling events in a coupled climate model three potential mechanisms behind centennial scale holocene cooling events are studied in simulations performed with the coupled climate model ecbilt clio 1 internal variability 2 solar forcing and 3 freshwater forcing in experiments with constant preindustrial forcings three centennial scale cooling events occur spontaneously in 15 000 years these rare events represent an unstable internal mode of variability that is characterised by a weaker thermohaline circulation a more southward location of the main site of deep water formation expanded sea ice cover and cooling of 101c over the nordic seas this mode is visited more frequently when the climate is cooled by abruptly reducing the solar constant by 5 or 3 wm 2 prescribing a solar forcing of the same magnitude but following a sinusoidal function with a period of 100 or 1000 years does not result in any centennial scale cooling events the latter forcing does however result in more frequent individual cold years in the north atlantic region that are related to local weakening of the deep convection and sea ice expansion adding realistic freshwater pulses to the labrador sea is also able to trigger centennial scale cooling events with temperature anomalies resembling proxy evidence for the cooling event at 8 2 kyr bp suggesting that freshwater forcing is a valid explanation for early holocene cooling events r 2007 elsevier ltd all rights reserved

cosmic ray production rates of 10be and 26al in quartz from glacially polished rocks we have studied the concentrations of 10be and 26al in quartz crystals extracted from glacially polished granitic surfaces from the sierra nevada range these surfaces were identified with the glacial advance during the tioga period 11 000 years ago our measurements yield the most accurate estimates to date for the absolute production rates of these nuclides in sio2 due to cosmic ray nucleons and muons for geomagnetic latitudes 43 8 44 6 n and altitudes 2 1 3 6 km the estimates are relatively free from uncertainties in snow cover since we studied a suite of rock surfaces inclined 0 75 with respect to the horizontal the principal uncertainty arises due to the lack of a precise date for the glacial retreat event about 10 the 26al 10be ratio at production 6 0 is determined more accurately since the exposure age of the samples is 2 orders of magnitude smaller than the mean lives of the two nuclides production rates of 10be and 26al in quartz at other latitudes and altitudes in the troposphere can be determined from the present measurements by scaling using the known altitude and latitude dependence of cosmic ray fluxes of nucleons and negative muons knowledge of the production rates of these nuclides is a prerequisite for their application in erosion and geomorphological studies

atmospheric scaling of cosmogenic nuclide production climate effect 1 absorption of cosmic rays by atmospheric mass varies temporally due to a redistribution of atmospheric pressure by ice sheets during glaciations the compression and expansion of the atmosphere due to cooling and warming and changes in katabatic winds near large ice masses these atmospheric processes can result in changes in production rates of cosmogenic nuclides which when integrated over long exposure durations may result in 0 to 5 adjustments in site production rates depending on location combining a ccm3 model with imbedded ice sheets for 20 ka we show that production rates changes relative to today are greatest at high elevations 6 7 at 5 km altitude due to atmospheric compression from decreased temperature production rates at specific times for sites near ice sheet margins can be reduced more than 10 due to a combination of katabatic winds draining off the ice sheet margins and atmospheric cooling nunatak settings may be significantly affected by the climate effect due to persistent glacial atmospheric conditions atmospheric variability may explain some of the disparities among cosmogenic nuclide production rate calibrations

scaling time integrated in situ cosmogenic nuclide production rates using a continuous geomagnetic model abstract spatial and temporal variations in earth s magnetic field affect the corresponding time integrated distribution of in situ cosmogenic nuclide cn production rates these effects can be quantified by the effective vertical cutoff rigidity r c a measure of the energy required for primary cosmic rays to penetrate the geomagnetic field and interact with the atmosphere at a given location recent cn production rate scaling models are based on atmospheric cosmic ray measurements parameterized using r c estimates derived from detailed modern geomagnetic field representations which include both dipole and non dipole field contributions however published methods for quantifying time integrated geomagnetic effects on cn production rate scaling rely on various geocentric dipolar approximations to r c driven by separate records of paleomagnetic pole position and paleointensity therefore applying dipolar paleomagnetic records spanning millennial time scales which explicitly ignore past non dipole effects to scaling models derived using modern geomagnetic field representations may lead to systematic errors in any calculated results a recently published continuous geomagnetic model covering the last 7 kyr cals7k 2 m korte and c g constable continuous geomagnetic field models for the past 7 millennia 2 cals7k 2005 geochem geophys geosyst 6 q02h16 doi 10 1029 2004gc000801 may allow reduction of such errors by bridging the gap between detailed modern geomagnetic and simplified paleomagnetic models we have developed a new model framework describing temporal and spatial variation in r c for 0 7 ka and earlier based on cals7k 2 which explicitly accounts for non dipole field effects while attempting to mitigate systematic scaling biases scaling factors derived using the new r c framework predict significant longitudinal variability in time integrated cn production while predictions using dipolar geomagnetic approximations do not one can test these predictions using in situ cosmogenic 14 c in situ 14 c in quartz due to its short half life 5 73 kyr 14 c attains secular equilibrium between production and decay after approximately 25 kyr of exposure at which point its measured concentration is only a function of its integrated average production rate initial in situ 14 c results from samples at secular equilibrium from 38 n and 3 5 km in tibet and eastern california are consistent with the longitudinal variability predicted by the new framework

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

cordilleran ice sheet mass loss preceded climate reversals near the pleistocene termination the cordilleran ice sheet cis once covered an area comparable to that of greenland previous geologic evidence and numerical models indicate that the ice sheet covered much of westernmost canada as late as 12 5 thousand years ago ka new data indicate that substantial areas throughout westernmost canada were ice free prior to 12 5 ka and some as early as 14 0 ka with implications for climate dynamics and the timing of meltwater discharge to the pacific and arctic oceans early bolling allerod warmth halved the mass of the cis in as little as 500 years causing 2 5 to 3 0 meters of sea level rise dozens of cirque and valley glaciers along with the southern margin of the cis advanced into recently deglaciated regions during the bolling allerod and younger dryas

evidence for the asynchronous retreat of large outlet glaciers in southeast greenland at the end of the last glaciation recent rapid changes in the marine terminating sectors of the greenland ice sheet gris have prompted concerns about the future stability of the ice sheet long term records of ice sheet behaviour provide valuable context to assess the magnitude of current change and may help resolve the mechanisms driving deglaciation we report 23 new 10be exposure ages which constrain the deglacial history of two large fjord systems in southeast se greenland we compare our chronologies with existing data from the centre of the sector to examine the timing and style of deglaciation at a regional scale glacial erratic 10be exposure ages demonstrate that kangerdlugssuaq fjord deglaciated at 11 8 ka at the end of the younger dryas yd 12 8 11 6 ka retreat at kangerdlugssuaq fjord coincided with known incursion of the warm irminger current ic onto the continental shelf this is inferred to have initiated retreat comparison with recently published results from sermilik fjord and new 10be ages from bernstorffs fjord indicates deglaciation occurred 1 ka later in the south of the se region sermilik fjord 10 9 ka and bernstorffs fjord 10 4 ka deglaciated later retreat likely occurred in response to dramatic climatic amelioration at the termination of the yd stadial we suggest that the disparate timing of deglaciation across the se region may be primarily explained by the varying influence of the warm ic glaciers in southern se greenland were isolated from warm atlantic waters during the yd by complex shelf bathymetry in all fjord settings ice retreat was rapid and persistent consistent with the absence of geomorphological evidence for stillstand or readvance events ice retreat was accompanied by rapid thinning and likely continued to well within present day ice sheet margins glacial erratic 10be age determinations and geomorphological observations show no evidence for holocene readvance events prior to the little ice age lia