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

late pleistocene glacial evolutionary stages in the gredos mountains iberian central system during the last glacial period late pleistocene the summits of the gredos mountains iberian central system were covered by plateau glaciers and later evolved into valley and slope glaciers the evolutionary sequence of these paleoglaciers has been obtained using geomorphological indicators and taking the principal moraine as reference these moraines show the limit between the glaciation and deglaciation periods in the glaciation period g four chronologically sequenced stages have been identified the local glacial maximum or maximum ice extent gm limited retreat lr re advance ra and finally major stabilization the steady state stage of greatest glacial stability ms in the deglaciation period d six chronologically sequenced stages have been identified an absolute retreat which involved regression and stabilization d1 two major retreat periods d2 and d4 and two stabilization periods d3 and d5 finally the last stage represents the complete disappearance of the glaciers d6 this evolutionary sequence allows more precise studies of the ages assigned through numerical dating procedures and of the correlation of the paleoglaciers in the gredos mountains with those of other regions

cosmogenic chlorine 36 from calcium spallation calcium is a major target element for cosmogenic 36cl production consequently 36cl rapidly reaches detectable levels in minerals such as calcite and calcium feldspar exposed at the earth s surface spallation of calcium isotopes typically accounts for 80 90 of 36cl production in these minerals with subsidiary contributions from negative muon capture by 40ca and thermal neutron capture by 35cl to provide a basis for surface exposure dating we have calibrated cosmogenic 36cl production in calcium feldspar from the 17 300 year old tabernacle hill basalt at an altitude of 1445 m and an effective geomagnetic latitude of 40 9 the calcium spallation rate is 152 11 atoms g ca 1 a 1 the corresponding rate at sea level and high latitude is estimated at 48 8 3 4 atoms g ca 1 a 1 the muon capture rate used to derive these values is 8 8 2 2 atoms g ca 1 a 1 at the tabernacle hill site scaled from a value of 4 8 1 2 atoms g ca 1 a 1 at sea level and high latitude the calcium spallation rate determined in this study is in excellent agreement with previous whole rock calibration measurements at tabernacle hill when these are recalculated with respect to the absolute timescale the calibration of 36c1 production from calcium underpins development of an exposure dating technique for calcite due to its high calcium content the 36cl production rate in calcite is higher than in any other common rock forming mineral measurement of 36cl in calcite with an accelerator mass spectrometric detection limit of 5 103 atoms per gram allows dating of limestone surfaces exposed for periods ranging from 102 106 years alternatively erosion rates from less than 1 to greater than 1000 m per year can be determined in the case of eroding karst surfaces though the 36cl production rate is lower in calcium feldspar than in calcite measurements on this mineral will provide a useful means of dating young basalt lavas

the deglaciation of the sierra nevada southern spain abstract cosmogenic 36 cl surface exposure dating was carried out on 19 samples from glacially polished bedrock rock glaciers and moraines of four glaciated valleys with different orientations in the sierra nevada spain around pico del veleta 37 3 n 3 21 w 3398 m asl remains of moraines older than the global last glacial maximum exist but their poor preservation makes them an unreliable subject for surface exposure dating results show that the last local glacial maximum advance took place earlier than the global last glacial maximum but within the mis 2 although additional dating is needed to confirm this exposure ages from bedrock steps show a general glacier retreat in progress by 15 14 ka shortly afterwards an extensive system of rock glaciers formed at the base of the valley headwalls with the most recent rock glacier lasting until 7 ka ago from their location morphology and analysis of other proxies we interpret their origin as related to the deglaciation process and marked instability of cirque headwalls rather than to extreme periglacial conditions a recent similar occurrence was the transformation of the little ice age glacier on the north face of the pico del veleta into a rock glacier under temperate high mountain climatic conditions

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

topographic lithologic and glaciation style influences on paraglacial processes in the upper sil and luna catchments cantabrian mountains nw spain abstract deglaciated mountainous areas are usually affected by a great range of paraglacial processes that involve progressively denudation of glacial imprints this study focuses on paraglacial processes and glacial landform preservation in six zones located in two catchments of the cantabrian mountains nw spain these zones are adjacent but display important topographic lithologic and glaciation style differences an analysis of how these variables conditioned the intensity and diversity of paraglacial processes in these zones was investigated through a detailed study of their relief lithology and paleo glacier surface using gis a comprehensive cartography of paraglacial landforms was also accomplished considering landslides alluvial fans and rock glaciers that show signs of having been conditioned by glaciation moraines and debris mantled slopes were also included in the analysis to examine their grade of preservation depending on the studied variables data comparison show that differences in glaciation style influenced paraglacial processes in the ancient icefield area relief modification by glacial action was limited and scarce paraglacial processes occur by contrast in the upper areas located in the southern ranges where an alpine style of glaciation was installed paraglacial processes were very active generating many rock glaciers lithology explains some paraglacial landforms distribution 1 landslides are associated with incohesive sandy and shale rocks 2 rock glaciers mainly occur in quartzite areas 3 in limestone areas subterranean drainage contributes to glacial landscape preservation but suffosion dolines affect some glacial deposits topography is also a key factor in paraglacial processes 1 moraines are well preserved in gently sloping valleys but rare in the steeper where they are usually transformed into moraine or debris mantled slopes 2 alluvial fans are more frequent in the steeper valleys but more dissected by postglacial river action 3 elevation and orientation show little influence on paraglacial landforms except in the generation of some periglacial features such as rock glaciers

cirques have growth spurts during deglacial and interglacial periods evidence from 10be and 26al nuclide inventories in the central and eastern pyrenees cirques are emblematic landforms of alpine landscapes the statistical distribution of cirque floor elevations is used to infer glacial equilibrium line altitude and the age of their frontal moraines for reconstructing glacial chronologies very few studies however have sought to measure cirque floor and supraglacial ridgetop bedrock downwearing rates in order to confront these denudation estimates with theoretical models of quaternary mountain landscape evolution here we use 10 be nuclide samples n 36 from moraines bedrock steps and supraglacial ridgetops among a population of cirques in the east central pyrenees in order to quantify denudation in the landscape and detect whether the mountain topography bears any relevance to the glacial buzzsaw hypothesis minimum exposure ages meas obtained for a succession of moraines spanning the oldest dryas to the holocene produced a deglaciation chronology for three different pyrenean ranges maladeta bassies and carlit based on a series of corrections calibrations and chronostratigraphic tuning procedures meas on ice polished bedrock exposures were further used to model denudation depths at nested timescales during the wurm the younger dryas and the holocene results show that subglacial cirque floor denudation was lower during glacial periods wurm 10 mm ka than during deglacial and interglacial periods tens to hundreds of mm ka the relative inefficiency of glacial denudation in the cirque zone during the wurm would have resulted from i cold based and or ii low gradient glaciers situated in the upper reaches of the icefield and or from iii glacier load starvation because of arrested clast supply from supraglacial rockslopes situated in the permafrost zone denudation peaked during the younger dryas and holocene glacial advances a time when cirque glaciers became steeper warmer based and when frost cracking weakened supraglacial ridgetops thus enhancing sub glacial erosion by providing debris to the sliding glacier base cirques therefore grow faster during more temperate periods of cirque glaciation than under full glacial conditions another key finding was the very low rates of ridgetop lowering averaged over the wurm and holocene 10 25 mm ka a comparison of the denudation rates obtained from the cirque zone with regional estimates of crustal uplift indicates that the alpine topography is not in a steady state the low intensity of glacial denudation failed to bring the topography to a buzzsaw equilibrium state

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

the deglaciation over laurentian fan history of diatoms ird ice and fresh water abstract a high resolution diatom census coupled with other proxy data from laurentian fan lf provides a detailed description of the last deglaciation bringing new insight to that period by revealing directly the timing of sea ice formation and melting cold events heinrich event 1 h1 and the younger dryas yd were multiphase events h1 16 8 15 7 cal kyr bp was defined by a two pulse release of icebergs promoting sea ice formation melting of sea ice after h1 corresponds to a cold and fresh anomaly that may have kept the bolling colder than the allerod at 13 6 cal kyr bp a cooling trend culminated with sea ice formation marking the yd onset 12 8 cal kyr bp the decrease in sea ice 12 2 cal kyr bp led to a yd second phase characterized by very cold winters however the contribution of warm water diatoms tends to increase at the same time and the yd gradual end 11 6 cal kyr bp contrasts with its abrupt end in greenland ice cores the yd cannot be regarded as an event triggered by a fresh water input through the laurentian channel since only one weak brief input nearly 1000 yrs after its onset is recorded very cold and cool conditions without ice mark the following preboreal a northward heat flux between 10 8 and 10 2 cal kyr bp was interrupted by the increased influence of coastal waters likely fed by inland melting there was no further development of sea ice or ice drift then

timing of glaciation during the last glacial cycle evaluating the concept of a global last glacial maximum lgm abstract it has long been known that mountain glaciers and continental ice sheets around the globe reached their respective maximum extent at different times during the last glacial cycle often well before the global last glacial maximum lgm c 23 19 ka which is formally defined by peaks in global sea level and marine oxygen isotope records however there is increasing evidence from around the world that it was not only mountain glaciers which were asynchronous with the global lgm but also some regions of the large continental glaciers the barents kara ice sheet in northern eurasia together with a majority of ice masses throughout asia and australasia reached their maximum early in the last glacial cycle a few thousand years before the global lgm period the east antarctic ice sheet also reached its maximum extent several millennia before the global lgm in numerous mountainous regions at high mid and low latitudes across the world glaciers reached their maximum extent before marine isotope stage mis 2 in mis 5 4 and 3 this is in contrast to most sectors of the laurentide ice sheet the cordilleran ice sheet the se sector of the fennoscandinavian ice sheet and the alpine ice sheet in central europe which appear to have reached their maximum close to the global lgm in mis 2 the diachronous maximum extents of both mountain glaciers and continental ice sheets during the last glacial cycle means that the term and acronym last glacial maximum lgm has limited chronostratigraphical meaning when correlating glacial deposits and landforms

a multiple dating method approach applied to the sanabria lake moraine complex nw iberian peninsula sw europe new evidence in the nw region of the iberian peninsula w42 n6 w of a glacial advance coeval with the global last glacial maximum lgm of the marine isotope stage 2 has been identified through a dataset of exposure ages based on 23 10 be concentration measurements carried out on boulder samples taken from a set of latero frontal moraines results span the interval 19 2e15 4 10 be ka matching the last deglaciation period when iberia experienced the coldest and driest conditions of the last 25 ka and are consistent with lateglacial chronologies established in other mountain regions from sw europe the extent of the lgm stade identified in this work is similar to the local maximum ice extent stade recorded and dated as prior to 33 ka using radiocarbon and optically stimulated luminescence this work showcases how multiple dating approaches and detailed geomorphological mapping are required to reconstruct realistic palaeoglacier evolution models

glacial stages in the pena negra valley iberian range northern iberian peninsula assessing the importance of the glacial record in small cirques in a marginal mountain area abstract the objective of this study was to assess whether it is possible to obtain a comprehensive record of the last deglaciation from the small pena negra glacial cirque in a marginal mountain range in the iberian range northern iberian peninsula the cirque is located in sierra cebollera at an elevation slightly over 2000 m a s l in the divide and has relatively low elevational difference between its uppermost and lowest parts the pena negra glacial cirque was selected because of the presence of several lateral moraines indicating the occurrence of a glacial tongue of 1 8 km length and a small rock glacier enabling identification of the main glacial stages that affected the paleo evolution of the glacier using cosmogenic exposure dating techniques and geomorphological mapping it was possible to reconstruct the historical pena negra glacier and to distinguish i the maximum ice extent mie at approximately 18 20 ka coinciding with the global last glacial maximum glgm although the occurrence of a previous stage was not ruled out ii a stage of glacial re advance at 16 17 ka coinciding with the oldest dryas followed by rapid ice melting iii the development of a rock glacier in a minor structural cirque near the headwall at 14 15 ka when paraglacial processes were probably dominant and iv evidence of ice melting in the uppermost cirque at 13 5 ka study of the pena negra glacier revealed the history of a minor valley glacier affected by distinct stages including the formation of a small rock glacier in the final phases of deglaciation no evidence of a younger dryas re advance was found

early holocene humidity patterns in the iberian peninsula reconstructed from lake pollen and speleothem records abstract comparison of selected well dated lacustrine speleothem and terrestrial pollen records spanning the holocene onset and the early holocene ca 11 7 8 cal kyrs bp in the iberian peninsula shows large hydrological fluctuations and landscape changes with a complex regional pattern in timing and intensity marine pollen records from alboran the mediterranean and off shore atlantic sites show a step wise increase in moisture and forest during this transition however available continental records point to two main patterns of spatial and temporal hydrological variability i atlantic influenced sites located at the northwestern areas enol sanabria lucenza prd 4 characterized by a gradual increase in humidity from the end of the younger dryas to the mid holocene similarly to most north atlantic records and ii continental and mediterranean influenced sites laguna grande villarquemado fuentillejo padul estanya banyoles salines with prolonged arid conditions of variable temporal extension after the younger dryas followed by an abrupt increase in moisture at 10 9 cal kyrs bp different local climate conditions influenced by topography or the variable sensitivity gradual versus threshold values of the proxies analyzed in each case are evaluated vegetation composition conifers versus mesothermophilous taxa and resilience would explain a subdued response of vegetation in central continental areas while in mediterranean sites insufficient summer moisture availability could not maintain high lake levels and promote mesophyte forest in contrast to atlantic influenced areas comparison with available climate models greenland ice cores north atlantic marine sequences and continental records from central and northern europe and the whole mediterranean region underlines the distinctive character of the hydrological changes occurred in inner iberia throughout the early holocene the persistent arid conditions might be explained by the intensification of the summer drought due to the high seasonality contrast at these latitudes caused by the orbital induced summer insolation maximum new records particularly from western and southernmost iberia and palaeoclimate models with higher spatial resolution would help to constrain these hypotheses

deep water provenance and dynamics of the de glacial atlantic meridional overturning circulation abstract reconstructing past modes of ocean circulation is an essential task in paleoclimatology and paleoceanography to this end we combine two sedimentary proxies nd isotopes e nd and the 231pa 230th ratio both of which are not directly involved in the global carbon cycle but allow the reconstruction of water mass provenance and provide information about the past strength of overturning circulation respectively in this study combined 231pa 230th and e nd down core profiles from six atlantic ocean sediment cores are presented the data set is complemented by the two available combined data sets from the literature from this we derive a comprehensive picture of spatial and temporal patterns and the dynamic changes of the atlantic meridional overturning circulation over the past 25 ka our results provide evidence for a consistent pattern of glacial stadial advances of southern sourced water along with a northward circulation mode for all cores in the deeper 3000 m atlantic results from shallower core sites support an active overturning cell of shoaled northern sourced water during the lgm and the subsequent deglaciation furthermore we report evidence for a short lived period of intensified amoc in the early holocene

origin and 10be surface exposure dating of a coarse debris accumulation in the hrubý jesenik mountains central europe abstract coarse debris accumulations cover large areas in high latitude and mountain environments but their age and origin remain mostly unknown here we reassess the morphology of a prominent coarse debris accumulation in the sudetes mountain range in central europe and constrain its timing with 10be surface exposure data our observations indicate that the landform in the south eastern slope of the su ridge appears consistent with the morphology of a block slope the oldest minimum age of 150 1 4 8 ka obtained for the tor at the upper limit of the block slope indicates the disintegration of the ridge and surface lowering under periglacial conditions prior to the last glacial interglacial cycle four exposure ages retrieved for block samples range from 84 3 3 8 to 26 8 2 6 ka providing evidence for block emplacement during the last cold period the exposure ages extend existing chronological dataset for peri glacial landforms in the sudetes and constrain the timing of cold environments in the area prior the last glacial maximum the ages are also consistent with surface exposure data reported for block fields and block slopes in western europe and confirm the formation of similar landforms over the last glacial period in the sudetes

deglaciation in the central pyrenees during the pleistocene holocene transition timing and geomorphological significance abstract in this study we document deglaciation in a sector of the southern central pyrenees the panticosa massif and the upper gallego and ossau valleys using cosmic ray exposure cre dating methods which were applied to samples from high altitude polished rock steps and rock glacier boulders the obtained cre dates show a coherent spatial distribution and confirm results previously obtained in this study area thus demonstrating the reliability and robustness of the method the results of analyses based on two distinct isotopes 10 be and 36 cl are consistent although the error is higher for results based on the 36 cl isotope the study provides evidence for ice extent in the high gallego valley during the oldest dryas with glacial advance until the bottom of the valleys although the main glacier tongues remained disconnected from each other during this period the extent of glacier advance was directly related to the elevation of the associated summits the younger dryas glaciers were constrained to cirques or very short ice tongues and dating of the polished rock steps indicates that the ice masses were present until the first millennium of the holocene the brazato rock glacier developed at the beginning of the holocene and remained active until the holocene thermal optimum because of the protective effect of large masses of blocks and boulders

late holocene environmental dynamics and climate variability in a mediterranean high mountain environment sierra nevada spain inferred from lake sediments and historical sources landscape dynamics in the periglacial belt of a high mountain mediterranean environment is a process of rapid evolution but complex reconstruction following this purpose in this paper we discuss data from two sources concerning the past evolution of the present day periglacial environment in the sierra nevada southern iberian peninsula mountain lake sediments and documentary sources la mosca lake sedimentary record provides information about the palaeocological evolution in the mulhacen cirque over the last three millennia while documentary sources enable us to reconstruct the landscape evolution in the high lands of this massif over the last eight centuries during the late holocene cold and wet phases have favoured the activity of geomorphic processes with ephemeral development of glaciers in the highest northern cirques abundance of late lying snow patches and a decrease of the vegetation cover in the highest catchments by contrast warm periods have been more conducive to geomorphic stabilit

the deglaciation history of the simplon region southern swiss alps constrained by 10be exposure dating of ice molded bedrock surfaces the deglaciation history of the swiss alps after the last glacial maximum involved the decay of several ice domes and the subsequent disintegration of valley glaciers at high altitude here we use bedrock exposure dating to reconstruct the temporal and spatial pattern of ice retreat at the simplon pass altitude 2000 m located 40 km southwest of the rhone ice dome eleven 10be exposure ages from glacially polished quartz veins and ice molded bedrock surfaces cluster tightly between 13 5 0 6 ka and 15 4 0 6 ka internal errors indicating that the simplon pass depression became ice free at 14 1 0 4 ka external error of mean age this age constraint is interpreted to record the melting of the high valley glaciers in the simplon pass region during the warm bolling allerod interstadial shortly after the oldest dryas stadial two bedrock samples collected a few hundred meters above the pass depression yield older 10be ages of 17 8 0 6 ka and 18 0 0 6 ka these ages likely reflect the initial downwasting of the rhone ice dome and the termination of the ice transfluence from the ice dome across the simplon pass toward the southern foreland there the retreat of the piedmont glacier in val d ossola was roughly synchronous with the decay of the rhone ice dome in the interior of the mountain belt as shown by 10be ages of 17 7 0 9 ka and 16 1 0 6 ka for a whaleback at 500 m elevation near montecrestese in northern italy in combination with well dated paleoclimate records derived from lake sediments our new age data suggest that during the deglaciation of the european alps the decay of ice domes was approximately synchronous with the retreat of piedmont glaciers in the foreland and was followed by the melting of high altitude valley glaciers after the transition from the oldest dryas to the bolling allerod when mean annual temperatures rose rapidly by 3 c

the deglaciation of the americas during the last glacial termination this paper reviews current understanding of deglaciation in north central and south america from the last glacial maximum to the beginning of the holocene together with paleoclimatic and paleoceanographic data we compare and contrast the pace of deglaciation and the response of glaciers to major climate events during the global last glacial maximum glgm 26 5 19 ka average temperatures decreased 4 to 8 c in the americas but precipitation varied strongly throughout this large region many glaciers in north and central america achieved their maximum extent during the glgm whereas others advanced even farther during the subsequent heinrich stadial 1 hs 1 glaciers in the andes also expanded during the glgm but that advance was not the largest except on tierra del fuego hs 1 17 5 14 6 ka was a time of general glacier thickening and advance throughout most of north and central america and in the tropical andes however glaciers in the temperate and subpolar andes thinned and retreated during this period during the bolling allerod interstadial b a 14 6 12 9 ka glaciers retreated throughout north and central america and in some cases completely disappeared many glaciers advanced during the antarctic cold reversal acr 14 6 12 9 ka in the tropical andes and patagonia there were small advances of glaciers in north america central america and in northern

exposure age chronology of the last glaciation in the eastern pyrenees abstract we present a chronology of ice recession in the eastern pyrenees based on in situ produced 10be data obtained from the tet paleoglacier complex the sampling strategy is based on the relative chronology provided by a detailed geomorphological map of glacial landforms results indicate that the last maximum ice advance occurred late i e during marine isotope stage 2 compared to the chronology currently established for the rest of the pyrenees despite debatable evidence for a glacial readvance during the oldest dryas stade ice cap melt out was rapid residual cirque glaciers having disappeared by the allerod interstade this is consistent both with north atlantic excursions established by the greenland ice cores and paleoenvironmental data for the region the rapid response of the east pyrenean ice cap to temperature variations is primarily linked to its small size compared to larger pyrenean ice fields to the dry mediterranean climate and to topography related nonlinearities in which a small vertical rise in equilibrium line altitude generates a large change in ice mass possible sources of age uncertainty are discussed in the context of sampling design for single nuclide 10be dating of landform sequences in formerly glaciated landscapes

late pleistocene deglaciation in the upper gallego valley central pyrenees abstract deglaciation processes in the upper gallego valley central southern pyrenees were studied using geomorphological mapping and 36 cl cosmogenic dating of moraine and rock glacier boulders as well as polished bedrock although the precise position of the gallego glacier during the global last glacial maximum is not known there is evidence that ice tongues retreated to the headwaters which caused subdivision of the main glacier into a number of individual glaciers prior to 17 ka a range of ages 16 to 11 ka was found among three tributary valleys within the general trend of deglaciation the retreat rate to cirque was estimated to be relatively rapid approximately 5 km per ka the mapped glacial sedimentology and geomorphology appears to support the occurrence of multiple minor advances and retreats or periods of stasis during the late deglaciation geomorphological and geological differences among the tributary valleys and error estimates associated with the results obtained prevented unambiguous correlations of the advances with the late pleistocene cold periods during the latter advances small glaciers and rock glaciers developed close to the cirque headwalls and co occurred under the same climatic conditions no evidence for holocene re advance was found for any of the three tributary valleys

sequence and chronology of the cuerpo de hombre paleoglacier iberian central system during the last glacial cycle abstract the cuerpo de hombre paleoglacier occupies the upper sector of the cuerpo de hombre river basin located on the northwest slope of the sierra de bejar mountains iberian central system at the stage of the maximum ice extent during the last glacial cycle this paleoglacier was one of the longest tongues emerging from the sierra de bejar plateau glacier the study of the morphostratigraphic succession and the geometric and genetic relations between the geomorphological indicators of this paleoglacier has revealed its evolutionary sequence during the last glacial cycle the comparison between this sequence and the one previously established by a regional evolutionary pattern shows that although they both coincide in general terms some stages substages of this pattern must be corrected or more clearly defined the absolute chronology of the different stages was obtained using terrestrial cosmogenic nuclides 10 be the maximum ice extent of cuerpo de hombre paleoglacier has been dated to 25 0 ka mis2 and concurrent with the lgm this chronology coincides with date obtained for other paleoglaciers in the iberian central system but is slightly more modern than the regional chronology estimated as most likely for the maximum ice extent in these areas subsequent to reaching the maximum extent the glacier had a retreat minimum age 20 6 ka followed by another stage of expansion or readvance after which it stabilised until the start of the deglaciation stage 17 8 ka in all previous work the deglaciation stages in the iberian central system have been described as one continuous recession process however in the cuerpo de hombre paleoglacier all the data point to stabilisations of considerable magnitude and particularly to another stage of readvance of the glacier based on its chronology minimum age 11 1 ka and its evolutionary significance this new readvance has been correlated with the older dryas stadial finally the evolutionary context marked by the indicators and its chronology confirm that the whole of the late glacial sequence identified in cuerpo de hombre can be correlated with the traditionally established in northern europe climatic periods or stadials and interstadials oldest dryas bolling older dryas allerod younger dryas the minimum ages obtained for the cold periods stadials in this sequence in the cuerpo de hombre paleoglacier are respectively 17 5 ka 13 9 ka and 11 1 ka this complete sequence of the late glacial period including the stadials older and younger dryas had not been previously identified in any of the paleoglaciers in the iberian central system

chronology of glaciations in the cantabrian mountains nw iberia during the last glacial cycle based on in situ produced 10be abstract the mountain ranges of the iberian peninsula preserve a valuable record of past glaciations that may help reconstruct past atmospheric circulation patterns in response to cooling events in the north atlantic ocean available chronologies for the glacial record of the cantabrian mountains which are mainly based on radiocarbon and luminescence dating of glacial related sediments suggest that glaciers recorded their glacial maximum gm during mis 3 and experienced a later last glacial maximum lgm advance this lgm extent is not established yet preventing a fair correlation with available cosmic ray exposure cre based chronologies for the glacial record of the pyrenees and the sistema central we present a glacial reconstruction and a 10 be cre chronology for the porma valley in the southern slope of the central cantabrian mountains glacial evidence at the lowest altitudes correspond to erratic boulders and composite moraines whose minimum 10 be cre age of 113 9 7 1 ka suggests that glaciers were at their maximum extent during mis 5d most likely in response to the minima in summertime insolation of the last glacial cycle recessional moraines preserved within the glacial maximum limits allow the assessment of subsequent glacier advances or stagnations the most remarkable advance took place prior to 55 7 4 0 ka probably at the end of mis 4 consistently with minimum radiocarbon ages previously reported for lacustrine glacial related deposits in the cantabrian mountains a limited number of 10 be cre ages from a composite moraine suggest a possible advance of the porma glacier coeval with the global lgm the glacier front attributed to the lgm would be placed within the margins of the previous gm like in the western pyrenees erratic boulders perched on an ice moulded bedrock surface provided a mean 10 be cre age of 17 7 1 0 ka suggesting that part of the recessional moraine sequence corresponds to minor advances or stagnations of the glacier fronts during the lateglacial period this recessional response is consistent with deglacial chronologies previously established in the pyrenees and the sistema central and correlates with the coldest and driest conditions of mis 2 according to lacustrine records finally a relict rock glacier provided a mean 10 be cre age of 15 7 0 8 ka for movement cessation of its toe indicating that periglacial conditions prevailed at least until the end of heinrich stadial 1 mystery interval

monitoring drake passage with elephant seals frontal structures and snapshots of transport conductivity temperature pressure satellite relay data loggers ctd srdls were attached to southern elephant seals mirounga leonina on the island of south georgia during the animals migration the ctdsrdls recorded and transmitted hydrographic profiles at a rate of approximately two profiles per day to an average depth of about 547 m representing transect type sections with a spatial resolution of 16 47 km along the migratory routes of the seals two sections are used to clearly identify the locations of the antarctic circumpolar current fronts across drake passage providing in situ data complementary to satellite and other techniques an empirical relationship between upper ocean temperature and baroclinic mass transport is used to determine the transport through drake passage at the times of the sections and these transports are compared with estimates derived by other techniques an absolute geostrophic velocity section across drake passage is calculated using ctd srdl data and data of absolute geostrophic surface velocities from altimetry the mean total baroclinic transports in june 2004 and april 2005 are estimated to be 124 3 106 6 14 3 106 m3 s21 and 112 3 106 6 14 3 106 m3 s21 respectively

cosmocalc an excel add in for cosmogenic nuclide calculations as dating methods using terrestrial cosmogenic nuclides tcn become more popular the need arises for a general purpose and easy to use data reduction software the cosmocalc excel add in calculates tcn production rate scaling factors using lal stone dunai and desilets methods topographic snow and self shielding factors and exposure ages erosion rates and burial ages and visualizes the results on banana style plots it uses an internally consistent tcn production equation that is based on the quadruple exponential approach of granger and smith 2000 cosmocalc was designed to be as user friendly as possible although the user interface is extremely simple the program is also very flexible and nearly all default parameter values can be changed to facilitate the comparison of different scaling factors a set of converter tools is provided allowing the user to easily convert cut off rigidities to magnetic inclinations elevations to atmospheric depths and so forth because it is important to use a consistent set of scaling factors for the sample measurements and the production rate calibration sites cosmocalc defines the production rates implicitly as a function of the original tcn concentrations of the calibration site the program is best suited for be 10 al 26 he 3 and ne 21 calculations although basic functionality for cl 36 and c 14 is also provided cosmocalc can be downloaded along with a set of test data from http cosmocalc googlepages com

maximum extent of late pleistocene glaciers and last deglaciation of la cerdanya mountains southeastern pyrenees abstract this paper examines glacial evolution in the la pera and malniu cirques and aranser la llosa and duran valleys in the cerdanya massifs on the south facing slopes of the eastern pyrenees a geomorphologic analysis and dating of moraine boulders glacially polished bedrock and rock glacier blocks were carried out by means of cosmogenic 36cl surface exposure dating the maximum ice advance was contemporary with the last glacial maximum at 23 ka ago and it was of greater or only slightly lesser magnitude than for previous quaternary advances the termini of glaciers remained close to maximum positions with minor advances and retreats until 18 17 ka when the glacial tongues disappeared from the valleys depending on the previous topography these glaciers left behind a single polygenic moraine in the case of confined valleys or multiple moraines next to each other in the case of flat more open areas a final glacial advance is detected during the oldest dryas close to the cirque headwalls and the glaciers finally disappeared during the bolling interstadial the glaciers were then replaced by rock glaciers whose front immediately became inactive although their activity continued near their source area until the early holocene

deglaciation of fennoscandia abstract to provide a new reconstruction of the deglaciation of the fennoscandian ice sheet in the form of calendar year time slices which are particularly useful for ice sheet modelling we have compiled and synthesized published geomorphological data for eskers ice marginal formations lineations marginal meltwater channels striae ice dammed lakes and geochronological data from radiocarbon varve optically stimulated luminescence and cosmogenic nuclide dating this is summarized as a deglaciation map of the fennoscandian ice sheet with isochrons marking every 1000 years between 22 and 13 cal kyr bp and every hundred years between 11 6 and final ice decay after 9 7 cal kyr bp deglaciation patterns vary across the fennoscandian ice sheet domain reflecting differences in climatic and geomorphic settings as well as ice sheet basal thermal conditions and terrestrial versus marine margins for example the ice sheet margin in the high precipitation coastal setting of the western sector responded sensitively to climatic variations leaving a detailed record of prominent moraines and other ice marginal deposits in many fjords and coastal valleys retreat rates across the southern sector differed between slow retreat of the terrestrial margin in western and southern sweden and rapid retreat of the calving ice margin in the baltic basin our reconstruction is consistent with much of the published research however the synthesis of a large amount of existing and new data support refined reconstructions in some areas for example the lgm extent of the ice sheet in northwestern russia was located far east and it occurred at a later time than the rest of the ice sheet at around 17 15 cal kyr bp we also propose a slightly different chronology of moraine formation over southern sweden based on improved correlations of moraine segments using new lidar data and tying the timing of moraine formation to greenland ice core cold stages retreat rates vary by as much as an order of magnitude in different sectors of the ice sheet with the lowest rates on the high elevation and maritime norwegian margin retreat rates compared to the climatic information provided by the greenland ice core record show a general correspondence between retreat rate and climatic forcing although a close match between retreat rate and climate is unlikely because of other controls such as topography and marine versus terrestrial margins overall the time slice reconstructions of fennoscandian ice sheet deglaciation from 22 to 9 7 cal kyr bp provide an important dataset for understanding the contexts that underpin spatial and temporal patterns in retreat of the fennoscandian ice sheet and are an important resource for testing and refining ice sheet models

structure and origin of holocene cold events abstract the present interglacial the holocene spans the period of the last 11 700 years it has sustained the growth and development of modern society the millennial scale decreasing solar insolation in the northern hemisphere summer lead to northern hemisphere cooling a southern shift of the intertropical convergence zone itcz and a weakening of the northern hemisphere summer monsoon systems on the multidecadal to multicentury scale periods of more stable and warmer climate were interrupted by several cold relapses at least in the northern hemisphere extra tropical area based on carefully selected 10 000 year long time series of temperature and humidity precipitation as well as reconstructions of glacier advances the spatiotemporal pattern of six cold relapses during the last 10 000 years was analysed and presented in form of a holocene climate atlas hoclat see http www oeschger unibe ch research projects holocene atlas a clear cyclicity was not found and the spatiotemporal variability of temperature and humidity precipitation during the six specific cold events 8200 6300 4700 2700 1550 and 550 years bp was very high different dynamical processes such as meltwater flux into the north atlantic low solar activity explosive volcanic eruptions and fluctuations of the thermohaline circulation likely played a major role in addition internal dynamics in the north atlantic and pacific area including their complex interaction were likely involved

environmental evolution in sierra nevada south spain since the last glaciation based on multi proxy records abstract our knowledge of the quaternary landscape evolution in the high mountain areas of the iberian peninsula has substantially improved over the last decades the sierra nevada is one of the most studied mountain ranges in southern europe regarding its environmental evolution the purpose of the present paper is to integrate and summarize all the studies focused on the reconstruction of the palaeoenvironmental history in this massif since the last glaciation research has focused both on different sedimentary records and historical sources a wide range of geomorphological sedimentological and geochronological techniques have been used to characterize the glacial periglacial wetland and lacustrine records for palaeoenvironmental purposes for the last nine centuries tens of descriptions maps and sketches describe the landscape of the summit area of the sierra nevada providing evidences of the historical environmental events based on a multi proxy approach five periods have been identified last glaciation deglaciation holocene little ice age and recent evolution recent studies have detected the maximum expansion of glaciers in the sierra nevada around 30 32 ka bp predating the global temperature minimum no data about the environmental evolution is available between 20 30 ka bp around 19 20 ka bp glaciers advanced significantly the process of deglaciation was rapid and around 14 15 ka bp the massif was almost free of ice the late glacial promoted the formation of small glaciers in the highest northern cirques and widespread active periglacial processes i e rock glaciers during the holocene there has been an alternation of colder warmer periods and changing moisture conditions periglacial processes have been generally widespread in the summit area with an increasing or decreasing activity depending on climate conditions ephemeral reappearance of small glacial cirques occurred in the highest northern cirques during the coldest and wettest phases this is the case of the little ice age as revealed by historical documents and sedimentary records since the last decades of the xix century the temperature has increased 0 93 c leading to a decrease of the intensity of periglacial processes in the high lands of the sierra nevada

collapse of marine based outlet glaciers from the scandinavian ice sheet abstract we present a reconstruction of the timing and retreat rates of more than 2000 m thick younger dryas yd fjord glaciers in western norway using a detailed chronology of 10 be exposure ages from lateral moraines and 14 c dated end moraines a primary conclusion is that ice margins retreated up the 120 170 km long fjords at mean rates of 240 340 m yr 1 during the early holocene we further show that part of the south western sector of the scandinavian ice sheet collapsed in two distinct steps the first step occurred between 19 5 and 18 5 ka bp as break up of the norwegian channel ice stream which drained the ice sheet during the last glacial maximum lgm the second step was the rapid retreat up the fjords mentioned above dated to 11 6 11 1 ka bp during the intervening 7000 years no net retreat occurred despite oscillations of the ice margin this stepwise ice margin retreat strongly contrasts with the more monotonic decay of the ice sheet as a whole indicating that water depths set the pace for climate triggered ice margin retreat in this part of the ice sheet calving and melting of marine margins has dominated mass loss from modern ice sheets in recent decades however the mechanisms and long term 100 1000 yr rate of ice front retreat is less certain and empirical examples such as those given here may help in developing better numerical models

climate sensitivity and geomorphological response of cirque glaciers from the late glacial to the holocene sierra nevada spain abstract through a detailed geomorphological study including thourough mapping of the geomorphic features as well as 10be cosmic ray exposure cre dating the geomorphological evolution of the mulhacen cirque since the maximum ice extent of the last glacial cycle until nowadays was determined this glacial cirque is shaped on the northern face of the mulhacen peak 3479 m a s l 37 03 12 n 3 18 41 w sierra nevada southern spain it includes several depositional and erosional glacial landforms that allowed reconstructing its environmental evolution since the last glacial cycle furthermore the sequence of glacial oscillations from this site was compared to that of other cirques of the massif evidencing that i new glaciers formed in these cirques during the younger dryas yd and ii disappeared at 11 7 1 0 ka depending on the altitude orientation and height of the cirque walls the final deglaciation of the cirques generated a diversity of landscapes including a wide range of glacial and periglacial landforms such as polished surfaces sequences of moraines proto rock glaciers or large rock glacier systems no glaciers existed in the sierra nevada during the middle holocene only the cirques whose summits exceed 3300 m are north exposed and whose walls exceed 300 m high i e mulhacen and veleta hosted glaciers during neoglacial phases including the little ice age lia approx 1300 1850 ce during these periods climate oscillations favoured the formation of small glaciers in these cirques which generated large moraine systems with either one polygenic ridge or a sequence of spaced frontal arcs the existence of glaciers impeded the formation of permafrost related landforms such as rock glaciers and protalus lobes until the end of the lia when they started to form these results are compared with the deglacial evolution in 55 cirques from iberian mountains as well as from glacial cirques from other mid latitude mountains and subpolar regions the chronology of their deglaciation as well as the landforms generated during glacial retreat followed similar patterns with no significant differences at regional scale for each mountain range the geomorphological diversity existing in each cirque depends on the local topographic characteristics although they formed during the same climatic phases

permafrost conditions in the mediterranean region since the last glaciation the relatively warm climate conditions prevailing today in the mediterranean region limit cold geomorphological processes only to the highest mountain environments however climate variability during the late pleistocene and holocene has led to significant spatio temporal variations of the glacial and periglacial domain in these mountains including permafrost conditions here we examine the distribution and evolution of permafrost in the mediterranean region considering five time periods last glaciation deglaciation holocene little ice age lia and present day the distribution of inactive permafrost derived features as well as sedimentary records indicates that the elevation limit of permafrost during the last glaciation was between 1000 m and even 2000 m lower than present permafrost was also widespread in non glaciated slopes above the snowline forming rock glaciers and block streams as well as meter sized stone circles in relatively flat summit areas as in most of the northern hemisphere the onset of deglaciation in the mediterranean region started around 19 20 ka the ice free terrain left by retreating glaciers was subject to paraglacial activity and intense periglacial processes under permafrost conditions many rock glaciers protalus lobes and block streams formed in these recently deglaciated environments though most of them became gradually inactive as temperatures kept rising especially those at lower altitudes following the younger dryas glacial advance the early holocene saw the last massive deglaciation in mediterranean mountains accompanied by a progressive shift of permafrost conditions to higher elevations it is unlikely that air temperatures recorded in mediterranean mountains during the holocene favoured the existence of widespread permafrost regimes with the only exception of the highest massifs exceeding 2500 3000 m lia colder climate promoted a minor glacial advance and the spatial expansion of permafrost with the development of new protalus lobes and rock glaciers in the highest massifs finally post lia warming has led to glacial retreat disappearance enhanced paraglacial activity shift of periglacial processes to higher elevations degradation of alpine permafrost along with geoecological changes

unblocking of the nares strait by greenland and ellesmere ice sheet retreat 10 000 years ago the extent of glaciation at the northern margin of the canadian greenland high latitude arctic region over the past 30 000 years is uncertain geological arguments have been made for greenland and ellesmere island ice sheets that coalesced to block the nares strait1 and for restricted ice sheets on the two islands2 leaving the strait open as it is today3 distinguishing between these two possibilities would provide significant constraints on present understanding of the past circulation between the arctic and atlantic oceans4 5 on estimates of past ice volume6 and on the response of the greenland ice sheet to climate change7 radiocarbon analyses provide dates for the deglaciation of the islands coasts but do not yield information on whether ice filled the strait here we present measurements of cosmogenic 36cl that has accumulated in situ in erratics and glacially polished bedrock on islands within the nares strait these data allow us to determine the time for which the rocks have been recently exposed to the atmosphere and thus the age of the final deglaciation of the strait we show that greenland and ellesmere ice sheets retreated from the nares strait about 10 000 years ago the strait was filled with ice during the last glaciation blocking this connection between the arctic and atlantic oceans and supporting the model of extensive and long lasting ice on land and sea in this region8 9 10 11

holocene and little ice age glacial activity in the marbore cirque monte perdido massif central spanish pyrenees the marbore cirque which is located in the southern central pyrenees on the north face of the monte perdido peak 42 40 0 n 0 5 0 w 3355 m contains a wide variety of holocene glacial and perig

topographic control of asynchronous glacial advances a case study from annapurna nepal 1 differences in the timing of glacial advances which are commonly attributed to climatic changes can be due to variations in valley topography cosmogenic 10be dates from 24 glacial moraine boulders in 5 valleys define two age populations late glacial and early holocene moraine ages correlate with paleoglacier valley hypsometries moraines in valleys with lower maximum altitudes date to the late glacial whereas those in valleys with higher maximum altitudes are early holocene two valleys with similar equilibrium line altitudes elas but contrasting ages are 5 km apart and share the same aspect such that spatial differences in climate can be excluded a glacial mass balance cellular automata model of these two neighboring valleys predicts that change from a cooler drier to warmer wetter climate as at the holocene onset would lead to the glacier in the higher altitude catchment advancing while the lower one retreats or disappears even though the ela only shifted by 120 m

little ice age glaciation and current glaciers in the iberian peninsula little ice age lia glacier advance has been registered in three of the main iberian high mountain areas pyrenees picos de europa and sierra nevada during the lia three different glacial env

timing of glacial retreat in the wicklow mountains ireland conditioned by glacier size and topography this paper presents 170 schmidt hammer exposure ages from moraine boulders and glacially sculpted bedrock to reveal the post last glacial maximum lgm history of the wicklow mountains ireland these data suggest that large ice masses survived for 4 7 ka after retreat of the irish sea ice stream and were sustained by summit ice fields until 16 6 ka post lgm retreat was dynamic with re advance moraines deposited in response to heinrich stadial 1 however these events reflect short term ice front oscillations 1 ka during the long term retreat phase retreat from re advance positions was synchronous across the range and paced by climate with time progressive deglaciation from low to high elevation in contrast marked asynchroneity in the timing of younger dryas deglaciation is closely linked to snow redistribution and indicates that for small cirque glaciers 1 km2 topography can exert the primary control on glacier survival this result has important implications for palaeoclimate econstructions as cirque glacier dynamics may be unrelated to climate this is further complicated by post depositional processes which can result in moraine ages e g 10be which post date retreat future palaeoclimate studies should prioritise cirque glaciers where snow contributing areas are small and where postdepositional disturbance is limited matrix poor boulder rich moraines

asynchroneity of maximum glacier advances in the central spanish pyrenees the deglaciation history of the escarra and lana mayor glaciers upper gallego valley central spanish pyrenees had been reconstructed on the basis of detailed geomorphological studies of glacier deposits sedimentological and palynological analyses of glacial lake sediments and an accelerator mass spectrometry ams 14c chronology based on minimum ages from glacial lake deposits the maximum extent of the pyrenean glaciers during the last glaciation was before 30 000 yr bp and pre dated the maximum advances of the scandinavian ice sheet and some alpine glaciers a later advance occurred during the coldest period around 20 000 yr bp synchronous with the maximum global ice extent but in the pyrenees it was less extensive than the previous one later there were minor advances followed by a stage of debris covered glaciers and a phase of moraine formation near cirque backwalls the deglaciation chronology of the upper gallego valley provides more examples of the general asynchroneity between mountain and continental glaciers the asynchroneity of maximum advances may be explained by different regional responses to climatic forcing and by the southern latitude of the pyrenees copyright 2002 john wiley sons ltd

latest pleistocene and holocene glacier variations in the european alps in the alps climatic conditions reflected in glacier and rock glacier activity in the earliest holocene show a strong affinity to conditions in the latest pleistocene younger dryas glacier advances in the alps related to younger dryas cooling led to the deposition of egesen stadial moraines egesen stadial moraines can be divided into three or in some cases even more phases sub stadials moraines of the earliest and most extended advance the egesen maximum stabilized at 12 2 1 0 ka based on 10be exposure dating at the schonferwall tyrol austria and the julier pass outer moraine switzerland final stabilization of moraines at the end of the egesen stadial was at 11 3 0 9 ka as shown by 10be data from four sites across the alps from west to east the sites are piano del praiet northwestern italy grosser aletschgletscher central switzerland julier pass inner moraine eastern switzerland and val viola northeastern italy there is excellent agreement of the 10be ages from the four sites in the earliest holocene glaciers in the northernmost mountain ranges advanced at around 10 8 1 1 ka as shown by 10be data from the kartell site northern tyrol austria in more sheltered drier regions rock glacier activity dominated as shown for example at julier pass and larstig valley tyrol austria new 10be dates presented here for two rock glaciers in larstig valley indicate final stabilization no later than 10 5 0 8 ka based on this data we conclude the earliest holocene between 11 6 and about 10 5 ka was still strongly affected by the cold climatic conditions of the younger dryas and the preboreal oscillation with the intervening warming phase having had the effect of rapid downwasting of egesen glaciers at or slightly before 10 5 ka rapid shrinkage of glaciers to a size smaller than their late 20th century size reflects markedly warmer and possibly also drier climate between about 10 5 ka and 3 3 ka conditions in the alps were not conducive to significant glacier expansion except possibly during rare brief intervals past tree line data from kaunertal tyrol austria in concert with radiocarbon and dendrochronologically dated wood fragments found recently in the glacier forefields in both the swiss and austrian alps points to long periods during the holocene when glaciers were smaller than they were during the late 20th century equilibrium line altitudes ela were about 200 m higher than they are today and about 300 m higher in comparison to little ice age lia elas the larstig rock glacier site we dated with 10be is the type area for a postulated mid holocene cold period called the larstig oscillation presumed age about 7 0 ka our data point to final stabilization of those rock glaciers in the earliest holocene and not in the middle holocene the combined data indicate there was no time window in the middle holocene long enough for rock glaciers of the size and at the elevation of the larstig site to have formed during the short infrequent cold oscillations between 10 5 and 3 3 ka small glaciers less than several km2 may have advanced to close to their lia dimensions overall the cold periods were just too short for large glaciers to advance after 3 3 ka climate conditions became generally colder and warm periods were brief and less frequent large glaciers for example grosser aletschgletscher advanced markedly at 3 0 2 6 ka around 600 ad and during the lia glaciers in the alps attained their lia maximum extents in the 14th 17th and 19th centuries with most reaching their greatest lia extent in the final 1850 1860 ad advance

late quaternary glacial phases in the iberian peninsula abstract the only glaciers existing today in the iberian peninsula are small features located in the pyrenees though their number and extension has undergone significant changes over the late quaternary the wide range of glacial landforms and deposits distributed across different iberian ranges suggests the occurrence of several past periods with larger glacial systems the objective of this research is to summarize the current knowledge on the spatial and temporal patterns of glacial activity in the iberian mountains during the late quaternary to this purpose the chronological framework was divided in six periods glaciations prior to the last glacial cycle middle pleistocene last glacial cycle late pleistocene termination 1 holocene little ice age lia and present day the data were geographically divided considering the mountain systems where glacial evidence exists pyrenees cantabrian range nw ranges central range iberian range and sierra nevada during quaternary cold stages ice accumulated in the head valleys of these mountain ranges and glaciers flowed down valleys in all cases glaciers remained confined within the mountain systems and did not reach the surrounding lowlands depending on the combination of temperatures and moisture conditions more or less ice was stored in some ranges there is evidence of middle pleistocene glaciations one potentially correlating with marine isotope stage mis 12 and another correlating with mis 6 with glaciation dated to ca 130 170 ka however most of the glacial records correspond to the last glacial cycle and subsequent termination the maximum glacial expansion of this last pleistocene glaciation stage occurred well before the global last glacial maximum lgm between 30 and 60 ka in the cantabrian mountains and pyrenees at ca 30 ka in sierra nevada and nw ranges and almost synchronously to the lgm in the central range and iberian range a massive glacial retreat occurred in all ranges at 19 20 ka but the long term deglaciation process was interrupted by cold intervals such as the oldest and younger dryas which favoured glacial expansion in the highest mountains temperature increase recorded during the holocene conditioned the melting of glaciers which only reappeared in the highest massifs during the coldest periods such as the lia however post lia warming led to glacier disappearance in the cantabrian mountains sierra nevada and most massifs of the pyrenees together with an accelerated shrinkage of the small glaciers still existing in this range at elevations near 3000 m

constraints on the timing of debris covered and rock glaciers an exploratory case study in the holar area northern iceland abstract eighteen samples for 36cl cosmic ray exposure cre dating were taken from glacially polished bedrocks moraine boulders fossil active rock glaciers and debris covered glaciers in fremri grjotardalur and holadalur cirques in the vi inesdalur hofsdalur and he insdalur valleys close to holar village in the trollaskagi peninsula northern iceland boulder sampling was preceded by a study of the boulder stability with the twofold aim of ensuring that the surfaces to be sampled were stable enough for the reliable application of cre dating and to better understand the relation between the glacier dynamics and exposition history the results show that the glaciers which occupy the valleys in trollaskagi began their retreat around 16 ka later the glaciers advanced again around 11 ka within the cirques and small moraines were formed thereafter these small glaciers retreated and evolved into rock glaciers as debris from paraglacial processes accumulated on the glacier surface the fronts of these rock glaciers stabilized definitively shortly after their formation and became eventually fossil after the melting of their internal ice new rock glaciers and debris covered glaciers formed afterwards which still have internal ice at present although their current dynamics are mostly related to subsidence the stabilization of these rock glaciers and debris covered glaciers is dated to the period between 7 and 3 ka although they may have been reactivated during cold neoglacial periods this research demonstrates the potential interest in applying cre dating methods to debris covered glaciers and rock glaciers to determine their origin evolution and phase of cessation of internal movement until they finally lost their internal ice and became fossil

centennial scale vegetation and north atlantic oscillation changes during the late holocene in the southern iberia high reso ce to lution pollen analysis charcoal non pollen palynomorphs and magnetic susceptibility have been analyzed in the sediment record of a peat bog in sierra nevada in southern iberia the study of these proxies provided the reconstruction of vegetation climate fire and human activity of the last 4500 cal yr bp a progressive trend towards aridification during the late holocene is observed in this record this trend is interrupted by millennial and centennial scale variability of relatively more humid and arid periods arid conditions are recorded between 4000 and 3100 cal yr bp being characterized by a decline in arboreal pollen and with a spike in magnetic susceptibility this is followed by a relatively humid period from 3100 to 1600 cal yr bp coinciding partially with the iberian roman humid period and is indicated by the increase of pinus and the decrease in xerophytic taxa the last 1500 cal yr bp are characterized by several centennial scale climatic oscillations generally arid conditions from 450 to 1300 ce depicted by a decrease in pinus and an increase in artemisia comprise the dark ages and the medieval climate anomaly since 1300 to 1850 ce pronounced oscillations occur between relatively humid and arid conditions four periods depicted by relatively higher pinus coinciding with the beginning and end of the little ice age are interrupted by three arid events characterized by an increase in artemisia these alternating arid and humid shifts could be explained by centennial scale changes in the north atlantic oscillation and solar activity

timing and new geomorphologic evidence of the last deglaciation stages in sierra nevada southern spain abstract the main objective of this research is to improve knowledge of the deglaciation stages in sierra nevada southern spain by applying 36cl cosmogenic exposure dating to 28 samples from moraine and fossil rock glacier boulders and glacial polished surfaces in 5 glaciated valleys around veleta peak 3396 m asl 37 03 02 n 3 20 54 w the results show that shortly before the last glacial maximum lgm and during the lgm the heads of the glacial valleys were occupied by ice tongues with possible glacial transfluence between the valleys after 19 ka a major glacial regression started but glaciers during the oldest dryas od expanded again and refilled the valley bottoms the glacial advances of the pre lgm lgm and od formed polygenic moraine systems during the bolling allerod the glaciers receded and probably disappeared thereafter the valley bottoms remained ice free during the younger dryas yd small glaciers developed again but only in cirques shaped on east facing slopes subsequently these glaciers started retreating towards their valley heads and finally disappeared completely with the onset of the holocene rock glaciers developed inside the deglaciated cirques on the eastern slopes of some valleys but only under the most active and protected headwalls did large complex rock glaciers develop and remained active until the mid holocene

global characterization of the holocene thermal maximum we analyze the global variations in the timing and magnitude of the holocene thermal maximum htm and their dependence on various forcings in transient simulations covering the last 9000 years 9 ka performed with a global atmosphere ocean vegetation model in these experiments we consider the influence of variations in orbital parameters and atmospheric greenhouse gases and the early holocene deglaciation of the laurentide ice sheet lis considering the lis deglaciation we quantify separately the impacts of the background melt water fluxes and the changes in topography and surface albedo in the analysis we focus on the intensity of the maximum temperature deviation relative to the preindustrial level its timing in the holocene and the seasonal expression in the model the warmest htm conditions are found at high latitudes in both hemispheres reaching 5 c above the preindustrial level while the smallest htm signal is seen over tropical oceans less than 0 5 c this latitudinal contrast is mostly related to the nature of the orbitally forced insolation forcing which is also largest at high latitudes and further enhanced by the polar amplification the holocene timing of the htm is earliest before 8 ka bp in regions not affected by the remnant lis particularly nw north america e asia n africa n south america the middle east ne siberia and australia compared to the early holocene insolation maximum the htm was delayed by 2 3 ka over ne north america and regions directly downwind from the lis a similar delay is simulated over the southern ocean while an intermediate lag of about 1 ka is found over most other continents and oceans the seasonal timing of the htm over continents generally occurs in the same month as the maximum insolation anomaly whereas over oceans the htm is delayed by 2 3 months exceptions are the oceans covered by sea ice and north africa were additional feedbacks results in a different seasonal timing the simulated timing and magnitude of the htm are generally consistent with global proxy evidence with some notable exceptions in the mediterranean region sw north america and eastern eurasia 2012 elsevier ltd

36cl production rate from k spallation in the european alps chironico landslide switzerland the abundant production of in situ cosmogenic 36cl from potassium renders 36cl measurements in k rich rocks or minerals such as k feldspars potentially useful for precisely dating rock surfaces either in single nuclide or in multi nuclide studies for example combined with 10be measurements in quartz however significant discrepancies in experimentally calibrated 36cl production rates from spallation of potassium 36pk sp referenced to sea level high latitude slhl limit the accuracy of 36cl dating from k rich lithologies we present a new 36cl calibration using k feldspars in which k spallation is the most dominant 36cl production pathway 92 of total 36cl thus minimizing uncertainties from the complex multi pathway 36cl production systematics the samples are derived from boulders of an 13 4 ka old landslide in the swiss alps 820 m 46 43 n 8 85 e we obtain a local 36pk sp of 306 16 atoms 36cl g k 1 a 1 and an slhl 36pk sp of 145 5 7 7 atoms 36cl g k 1 a 1 when scaled with a standard scaling protocol lm applying this slhl 36pk sp to determine 36cl exposure ages of k feldspars from 10be dated moraine boulders yields excellent agreement confirming the validity of the new slhl 36pk sp for surface exposure studies involving 36cl in k feldspars in the alps

cosmogenic 36cl ages of quaternary basalt flows in the mojave desert california usa abstract basalt flows provide excellent opportunities for calibration and intercomparison of quaternary dating methods remote sensing methods and rates of geomorphic processes the immediate motivation for this study was to provide chronology for a blind test of the utility of rock varnish microstratigraphy as an indicator of the age of flow emplacement five basaltic eruptive centers in the mojave desert of california were sampled for cosmogenic 36cl analysis multiple samples were taken from most centers and with one exception produced good agreement assuming a surficial erosion rate of 1 mm kyr 1 the flows yielded the following ages amboy crater 79 5 ka pisgah crater 22 5 1 3 ka cima field i cone 27 1 3 ka cima field a cone 21 1 6 ka and 11 5 1 5 ka cima field flow of unidentified origin 46 2 ka the ages from the cima i and a cones are in good agreement with previous cosmogenic 3he dating ages from the three previously undated flows are significantly older than previous estimates based on flow appearance tanzhou liu performed varnish microstratigraphic analysis on samples collected from the same sites his results were submitted for publication without knowledge of the 36cl ages his age estimates agree well with the 36cl ages for the three previously undated flows strongly supporting the validity of varnish microstratigraphy as a chronological correlation tool

spatial distribution and morphometry of permafrost related landforms in the central pyrenees and associated paleoclimatic implications abstract present and past permafrost distribution in the pyrenees is still under discussion as in other mid latitude mountain regions rock glaciers and protalus lobes are the main indicators of permafrost conditions in this paper we examine the distribution of these landforms in aran and boi valleys formerly glaciated u shaped valleys ranging from 600 to 3000 m in the southern and northern sides of the central pyrenees respectively the spatial distribution of these landforms and their chronostratigraphic position within the valley allow a better understanding of the climatic and environmental conditions necessary for their development up to 151 permafrost related landforms were identified in the boi valley including 56 rock glaciers and 95 protalus lobes in the case of the northern aran valley 76 rock glaciers and 89 protalus lobes were cataloged corresponding to 165 landforms most of the landforms 93 for rock glaciers and 95 for protalus lobes are located inside the glacial cirques with a few distributed in the slopes of the formerly glaciated valleys the lowest elevation of rock glaciers is situated at 1744 m aran and 2007 m boi whereas the lowest protalus lobes are located at 1740 m and 2033 m respectively therefore this altitude may be indicative of the lowest level recording permafrost conditions during the period in which these landforms formed with paleotemperatures ca 7 8 c lower than present day between 60 and 70 of the protalus lobes and rock glaciers are located between 2300 and 2600 m in boi valley and 2100 and 2400 m in aran valley the aspect shows a prevailing orientation of nw n and ne for both cases of rock glaciers and protalus lobes being almost absent in the s se and sw aspects the average slope of both landforms lies between 11 and 27 with a maximum of 35 for rock glaciers and 29 for protalus lobes the amplitude length ratio reveals that rock glaciers placed at lower altitudes are more elongated the chronostratigraphic position of these landforms within the valley and with respect to the moraine complexes suggests the existence of three generations of permafrost related landforms which are associated to the massive deglaciation process between the maximum glacial advance of the last glaciation and the holocene

redating the moraines in the kromer valley silvretta mountains new evidence for an early holocene glacier advance among the many well preserved moraine systems that are found throughout the austrian silvretta mountains a set of prominent moraines in the upper kromer valley located in front of the little ice

the greenland ice sheet during the last glacial cycle current ice loss and contribution to sea level rise from a palaeoclimatic perspective abstract during the last interglacial lig period between 130 and 116 thousand years before present ka bp the greenland ice sheet gris was considerably reduced in size contributing to a global mean sea level msl rise of 0 5 4 2 m relative to the present this is not sufficient to explain the 6 9 m msl rise estimated for the lig which implies that a significant contribution to the lig highstand came from antarctica following the lig the gris grew and attained its maximum volume of about 12 m global sea level equivalents sles between 18 and 16 ka bp since then the gris margins have retreated on an order of several hundred km following a general pattern of lagged response to changes in high latitude summer insolation and global greenhouse gas concentrations on shorter timescales and over smaller spatial scales the combination of internal ice sheet dynamics and external climate dynamics has often resulted in a more complex and asynchronous behaviour of the ice sheet margin the gris probably reached its minimum holocene extent around 4 ka bp and modelling studies suggest that it contributed to a rise in global msl of less than 0 2 m relative to the present at this time a period of steady growth followed the holocene minimum and in many areas the ice sheet advanced beyond its present limits during the little ice age i e the last few centuries currently the gris occupies an area of 1 7 10 6 km 2 and features a volume of 2 96 10 6 km 3 which amounts to 7 4 m sle observations show that the rate of mass loss from the gris has been accelerating over the past few decades and ice sheet modelling indicates that we have to go back to the last deglaciation around 10 ka bp in order to find sustained melt rates that were higher than those experienced over the last decade the future development of the gris will have a profound influence on sea level both globally and regionally but there are large uncertainties related to how the gris will respond to future global warming based on a range of modelling studies employing different emission scenarios the gris is expected to contribute about 0 1 0 3 m to global msl rise by the end of the 21st century in a longer time perspective modelling suggests that melting of the gris may replace ocean thermal expansion as the most important factor in future sea level rise potentially contributing with 0 7 2 6 m sle within the next 500 years multi millennial simulations show that the entire ice sheet 7 4 m sle might disappear completely within less than three thousand years under high emission scenarios i e with atmospheric co 2 reaching four times preindustrial levels

research history on glacial geomorphology and geochronology of the cantabrian mountains north iberia 43 42 n 7 2 w abstract the study of glacial geomorphology in the cantabrian mountains a mountain range that extends 460 km along the northern coast of the iberian peninsula sw europe started late in the 19th century and continues nowadays with a growing number of research papers however the number and timing of glaciations remains poorly understood partially due to the still limited number of numerical ages its southerly location and proximity to the atlantic ocean make this mountain range potentially sensitive to past climate fluctuations this work updates the glacial knowledge evolution for the whole range from the queixa invernadoiro massif to the basque mountains reviewing i the history of glacial research since the late 19th century ii the methodological approaches applied to reconstruct both the spatial extent and timing of past glacial stages and iii the main geomorphological and geochronological evidence reported until date including glacial features attributed to the last glacial cycle last 120 ka and previous glaciations according to current knowledge glaciers extended over the cantabrian mountains covering a total area of 3150 km2 showing asymmetric development conditioned by variations of the topographic configuration and moisture supply along the range available geochronology based on radiocarbon optically stimulated luminescence and terrestrial cosmogenic nuclides suggests the occurrence of at least 2 glacial advances during the last glacial cycle i a glacial maximum stage that took place at a minimum age of 36 45 ka marine isotope stage 3 and ii a second glacial advance at 19 23 ka mis 2 in some areas the extent of the glacier tongues during the second glacial advance was comparable to previous glacial maximum and was followed by glacial retreat conditions with formation of recessional moraines asynchronous glacial maximum conditions have been reported only for the castro valnera mis 4 3 numerical ages and queixa invernadoiro mis 6 1 numerical age massifs until now finally geomorphological evidence reported in picos de europa has been attributed to prior glaciations and correlated to cold conditions recorded during mis 12 and mis 22 based on a very limited number of numerical ages

small isolated glacial catchments as priority targets for cosmogenic surface exposure dating of pleistocene climate fluctuations southeastern pyrenees a new 10 be data set from a small glacial catchment in the pyrenees confirms almost full glacier extent during marine isotope stage mis 2 extends the oldest cosmogenic exposure ages of moraines in this mountain range to mis 5 and constrains paleoclimate reconstructions in the mediterranean region it also illustrates the advantageous conditions for the long term preservation of terminal moraines provided by small low gradient glacier catchments that did not merge with compound ice masses even during glacial maxima these small gently sloping and isolated glacier catchments are proposed as priority targets for terrestrial cosmogenic nuclide dating of peak pleistocene glacier advances providing scope for greater accuracy in interregional paleoclimatic correlations

environmental evolution in the picos de europa cantabrian mountains sw europe since the last glaciation abstract the western massif of the picos de europa latitude 43 n longitude 4 5 w includes some of the highest peaks in the cantabrian mountains this massif was heavily glaciated during the last glaciation though the post glacial environmental evolution is still poorly understood using a complementary geomorphological and sedimentological approach we have reconstructed the environmental events occurred in this massif since the last pleistocene glaciation the geomorphological distribution of glacial landforms suggests the occurrence of four main glacial stages maximum glacial advance glacial expansion after the maximum advance late glacial and little ice age moreover a 5 4 m long sedimentary sequence was retrieved from the karstic depression of belbin providing a continuous record of the paleoenvironmental conditions in this area since the last glaciation until nowadays this section suggests that the maximum glacial expansion occurred at a minimum age of 37 2 ka cal bp significantly prior to the global last glacial maximum subsequently periglacial processes prevailed in the mid lands of the massif until glaciers expanded between 22 5 and 18 7 ka cal bp following the melting of the glaciers a shallow lake appeared in the belbin depression lake sediments do not show evidence of a cold stage during the late glacial when moraine systems formed at higher locations the terrestrification of this lake started at 8 ka cal bp and the area turned into grassland at 4 9 ka cal bp the existence of charcoal particles in the sediments of belbin sequence reveals the onset of human occupation in the massif through the use of fire activity for grazing purposes finally the presence of moraines inside the highest northern cirques shows evidence of the last glacial phase that occurred during the little ice age cold event since then the warming climate has led to the melting of these glaciers and periglacial processes prevail in the high lands of the massif

atmospheric methane southern european vegetation and low mid latitude links on orbital and millennial timescales abstract pollen records from marine and terrestrial sequences in southern europe reveal a strong coherence between changes in tree populations and atmospheric methane concentrations over the last 800 thousand years variations in the continental hydrological balance provide a link for the observed patterns leading to concomitant changes in southern european vegetation and low latitude wetland extent and methane volatile organic compound emissions although additional contributions to the methane budget from extratropical sources are not excluded here we propose that the close coupling between low and mid latitude hydrological changes reflects shifts in the mean latitudinal position of the intertropical convergence zone which determines the extent to which southern europe is dominated by subtropical or mid high latitude influences this provides a conceptual framework within which to view vegetation variability in southern europe on orbital and millennial timescales

late pleistocene and holocene glaciation in the pyrenees a critical review and new evidence from 10be exposure ages south central pyrenees a compilation and a critical assessment of the 14c data set available show that the chronology of glacial events in the pyrenees is not well constrained after reviewing the literature on glacial reconstruction we suggest a simplified subdivision of the pyrenean last glacial cycle record into last pleniglacial deglaciation and neoglacial to improve the numerical glacial chronology we provide 10be surface exposure ages for 5 glacial erosion surfaces 9 moraines and 2 erratics in the upper noguera ribagorcana valley south central pyrenees published corrected 14c data and new 10be exposure ages indicate that the major phase of moraine building recorded in this valley during the last pleniglacial probably occurred after 25 ka bp this age calls in question the generally accepted hypothesis of a very early deglaciation of the pyrenees ca 70 40 ka bp and strongly suggests that the pyrenees could have been in pleniglacial conditions during the last glacial maximum lgm however we do not exclude the possibility that the maximum glacier extent during the last glacial cycle had taken place much earlier than the lgm as indicated by some published u th ams 14c and osl data we suggest that pleniglacial conditions could have taken place during a longer 30 20 ka period than generally assumed and that the last pleniglacial could include several glacier fluctuations recorded irregularly in different valleys with a last major glacier readvance taking place around the lgm in addition the deglaciation is represented by a series of moraines deposited between ca 13 7 0 9 and 10 1 0 6 ka this moraine series indicates a highly variable climatic pattern that is partly correlated with greenland stadial 1 the younger dryas and suggests that the deglaciation could have continued into the early holocene

quantifying the modern recharge of the fossil sahara aquifers 1 the north western sahara aquifer system nwsas one of the world s largest groundwater systems shows an overall piezometric decline associated with increasing withdrawals estimating the recharge rate in such a semiarid system is challenging but crucial for sustainable water development in this paper the recharge of the nwsas is estimated using a regional water budget based on grace terrestrial water storage monthly records soil moisture from the gldas a land data system that assimilates hydrological information and groundwater pumping rates a cumulated natural recharge rate of 1 40 0 90 km3 yr 1is estimated for the two main aquifers our results suggest a renewal rate of about 40 which partly contradicts the premise that recharge in this area should be very low or even null aquifer depletion inferred from our analysis is consistent with observed piezometric head decline in the two main aquifers in the region annual recharge variations were also estimated and vary between 0 and 4 40 km3 yr 1for the period 2003 2010 these values correspond to a recharge between 0 and 6 75 mm yr 1 on the 650 000 km2of outcropping areas of the aquifers which is consistent with the expected weak and sporadic recharge in this semiarid environment these variations are also in line with annual rainfall variation with a lag time of about 1 year

high resolution evidence for linkages between nw european ice sheet instability and atlantic meridional overturning circulation published studies show that ice rafted debris ird deposition preceding heinrich h events h1 and h2 in the ne atlantic was derived from the nw european ice sheets nweis possibly offering clues about ice sheet sensitivity and stability and the mechanisms that caused periodic collapse of the laurentide ice sheet lis we present detailed lithological and geochemical records including radiogenic isotope fingerprinting of ird deposits from core md01 2461 proximal to the last glacial british ice sheet bis demonstrating persistent instability of the bis with significant destabilisation occurring 1 5 1 9 kyr prior to both h1 and h2 dated at 16 9 and 24 1 kyr bp respectively in the ne atlantic paired mg ca and 18o data from the surface dwelling globigerina bulloides and subsurface dwelling neogloboquadrina pachyderma sinistral are used to determine late glacial variability of temperature salinity and stratification of the upper water column a picture emerges that the bis was in a continuing state of readjustment and never fully reached steady state increased sea surface temperatures appear to have triggered the episode of nweis instability preceding h1 it seems most probable that the so called precursor events were not linked to the h events however if response to a common thermal forcing is considered an increased response time of the lis up to 2 kyr longer than the nweis may be inferred negative salinity excursions of up to 2 6 indicate significant incursions of melt water associated with peaks in nweis instability decreased surface density led to a more stable stratification of the upper water column and is associated with reduced ventilation of intermediate waters recorded in depleted epibenthic 13c cibicidoides wuellerstorfi we suggest that instability and meltwater forcing of the nweis temporarily weakened atlantic meridional overturning circulation allowing transient advance of southern sourced waters to this site prior to h events 1 and 2

pattern and timing of retreat of the last british irish ice sheet during the last glacial the ice sheet that subsumed most of britain ireland and the north sea attained its maximum extent by 27 ka bp and with an ice volume sufficient to raise global sea level by ca 2 5 m when it melted we reconstruct the demise of this british irish ice sheet biis and present palaeo glaciological maps of retreat stages between 27 and 15 ka bp the whole land area was investigated using remote sensing data and we present maps of moraines meltwater channels eskers and drumlins and a methodology of how to interpret and bring them together for the continental shelf numerous large moraines were discovered recording an extensive pattern of retreat stretching from sw ireland to the shetland isles from an integration of this new mapping of glacial geomorphology 26 000 landforms with previously published evidence compiled in the britice database we derive a pattern of retreat for the whole biis we review and compile relevant dates 881 examples that constrain the timing of retreat all data are held within a geographic information system gis and are deciphered to produce a best estimate of the combined pattern and timing of retreat pattern information reveals an ice sheet mainly comprised of a shelf parallel configuration from sw ireland to ne scotland but it spread far enough to the south to incorporate outlying ice domes over wales the lake district and kerry final disintegration was into a number of separate ice caps rather than reduction as a single mass and paradoxically retreat was not always back to high ground by 23 ka bp ice withdrew along its northern boundaries at the same time as the southern margins were expanding including transient ice streaming down the irish sea and advances of lobes in the cheshire basin vale of york and east coast of england ice divides migrated south by 19 ka the ice sheet was in crisis with widespread marine based ice losses particularly in the northern north sea and the irish sea considerable dynamic thinning occurred during this phase final collapse of all marine sectors occurred by 17 ka bp and with most margins beginning to back step onshore disintegration of the north sea ice bridge between britain and norway remains loosely constrained in time but the possibility of catastrophic collapse of this sector is highlighted the north channel and irish sea ice streams had finally cleaved the ice sheet into separate irish and scottish ice sheets by 16 ka bp rates of ice loss were found to vary widely over space and time e g 65 260 km3 per year the role of ice streams and calving losses of marine based sectors are examined retreat rates of up to ca 150 ma 1 were found for some ice stream margins that large parts 2 3 of the biis were marine based drained by ice streams and possibly with fringing ice shelves in places makes it a useful analogue for the west antarctic ice sheet wais this is especially so because the biis deglaciated in response to rising temperatures and a rising sea level driven by melting of other ice masses which are the current forcings that might cause collapse of the wais our reconstruction when viewed from the opposite perspective documents when fresh land became exposed for exploitation by plants animals and man and records for how long such land has been available for soil and geochemical development and ecological succession

revised quaternary glacial succession and post lgm recession southern wind river range wyoming usa abstract we present here a more complete cosmogenic chronology of pleistocene glacial deposits for the wind river range wyoming usa fifty one new and thirty nine re calculated 10be and 26al exposure ages from sinks and north fork canyons stough basin cirque of the towers and the temple lake valley allow us to more tightly constrain the timing and sequence of glacial alloformations in the southern portion of the range moraines diamicts and bedrock exposures here have previously been correlated with as many as five pleistocene and four holocene glacial events exposure ages from pleistocene alloformations associated with trunk glaciers in sinks canyon and north fork canyon generally confirm earlier age estimates cosmogenic radionuclide crn 10be and 26al ages from moraines and striated bedrock surfaces previously mapped as pinedale correspond to mis2 while boulder exposure ages from moraines mapped as bull lake correspond generally to mis5 mis6 geomorphic data from a moraine previously mapped as younger pre sacagawea ridge appears to correspond most closely to the sacagawea ridge glacial episode mis 16 but the uncertainty of a single 10be exposure age suggests the unit could be as young as mis 10 or as old as mis 18 boulders from a diamict on table mountain previously reported as older pre sacagawea ridge yield two 10be exposure ages that suggest the presence of early pleistocene glacial activity here possibly older than 1 2 ma mis 30 bedrock exposure ages within sinks canyon suggest the pinedale valley glacier had retreated from the floor of sinks canyon to above popoagie falls by ca 15 3 ka cirque glaciers in stough basin appear to have retreated behind their riegels by ca 16 ka which suggests the cirque glaciers were decoupling across their riegels from the valley glaciers below at this time prior to their readvance to form lateglacial moraines new 10be boulder exposure ages from moraines previously correlated to the temple lake and alice lake allostratigraphic units in the cirques of stough basin and cirque of the towers show general equivalence to the stadial event just prior to the onset of the bolling interstadial 17 5 14 7 ka and to the intra allerod cold period younger dryas stadial phase 13 9 11 7 ka respectively from this evidence the temple lake alloformation of the wind river mountains now should correspond to the intimate gs 2 1a oldest dryas stadial event while the alice lake alloformation should correspond to the intimate gs 2 stadial iacp younger dryas thus we consider that evidence no longer exists for early to mid holocene glacial events in the southern wind river range

paraglacial slope failures in the aran valley central pyrenees abstract slope failures are widespread phenomena in mid latitude mountain environments that were glaciated during the last glacial cycle this is the case of the aran valley in the upper garonne catchment central pyrenees that included glaciers several hundred meters thick following postglacial warming and ice thinning the recently deglaciated slopes were subject to intense stress readjustments the so called paraglacial dynamics we have identified up to 135 major slope failures in the aran valley with only 10 units occurring outside the glaciated domain of the maximum ice extent of the last glacial the presence of polished bedrock surfaces till and moraine ridges next to some of these features evidence a close connection between glacial and slope processes we have detected different types of slope failures affecting both bedrock 12 large catastrophic rock slope failures 16 rock slope deformation 34 rockfalls and 49 rockslides and unconsolidated glacial sediments 14 slope readjustments on drift mantled slopes the average altitude of rock slope failures oscillates between 1551 and 1991 m with a mean length ranging from 147 to 905 m and a width between 247 and 513 m the affected surface is also highly variable oscillating between 0 02 and 126 2 ha slope failures occur in different lithological settings but they are most frequent in slate lutite and limestone bedrocks we conclude that most of the failures show a paraglacial origin though other factors i e lithology and topography promoted slope instability

spatial and temporal variability of periglaciation of the iberian peninsula abstract active periglacial processes are currently marginal in the iberian peninsula spatially limited to the highest mountain ranges however a wide variety of periglacial deposits and landforms are distributed in low and mid altitude environments which shows evidence of past periods of enhanced periglacial activity the purpose of this paper is to summarize the present knowledge of past periglacial activity in the iberian peninsula the chronological framework takes four main stages into account the last glaciation deglaciation holocene and present day processes this study focuses on the highest massifs pyrenees cantabrian range nw ranges central range iberian range sierra nevada as well as other lower elevation environments namely the central iberian meseta during the last glaciation the periglacial belt extended to much lower altitudes than today reaching current sea level in the nw corner of the iberian peninsula a wide range of geomorphological landforms and sedimentary records is indicative of very active periglacial processes during that phase in some cases related to permafrost conditions i e block streams rock glaciers most of the inactive landforms and deposits in low and mid elevations in iberia are also related to this phase the massive deglaciation of the iberian massifs was caused by a gradual increase in temperatures the deglaciation phase was only interrupted by a short period with colder conditions the younger dryas that reactivated periglacial processes in the formerly glaciated cirques of the highest lands specifically with the widespread development of rock glaciers during the holocene periglacial processes have been only active in the highest ranges shifting in altitude according to temperature regimes and moisture conditions the little ice age saw the reactivation of periglacial activity in lower elevations than today currently periglacial processes are only active in elevations exceeding 2500 m in the southern ranges and above 2000 2200 m in the northern massifs higher in sierra nevada in the south of iberian peninsula

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

last glacial maximum and lateglacial in the polish high tatra mountains revised deglaciation chronology based on the 10 be exposure age dating abstract deglaciation chronology of the polish high tatra mountains has been reconstructed based on 10 be exposure age dating fifty seven rock samples were collected from boulders located on the terminal and lateral moraines that limit the horizontal extent of the lgm and the lateglacial glaciers in the biala woda and sucha woda catchments the uncertainty weighted mean age of 21 5 2 5 ka obtained for the maximum terminal moraine in the sucha woda valley indicates that the oldest preserved moraines were formed during the global lgm the age population ranges between 15 1 1 0 and 28 3 2 0 ka and suggests that glaciers reached their maximum position lgm i as early as 28 25 ka and the final stabilization of the form occurred much later possibly after melting of buried dead ice the younger glacial oscillation lgm ii occurred no later than 20 5 ka and is represented by well preserved termino lateral moraine systems in the panszczyca valley the first lateglacial stage lg1 in the study area is documented in the rybi potok valley at the rp1 moraine 1300 m a s l which was stable at around 16 6 0 3 ka the younger lg2 stage has no defined absolute age however it is constrained between 16 5 and 15 5 ka by the timing of the lg3 stage this cold event is represented by well formed moraines in the roztoka piec stawow polskich rybi potok and panszczyca valleys of which exposure age indicates their deposition between 15 0 0 5 and 15 6 0 1 ka the lg1 lg2 and lg3 stages likely occurred during the oldest dryas cold stage greenland stadial 2 1a related to the north atlantic cooling heinrich event 1 the youngest glacial oscillation is evidenced by moraines in the pusta and panszczyca valleys these moraines are composed of very large granitic blocks of which exposure ages often exhibit isotope inheritance this is reflected by the youngest p3 moraine in the panszczyca valley with a mean age of deposition close to the lgm the r4 moraine system in the pusta valley however indicates two oscillations phases that occurred at around 13 ka and correlates well with the timing of rp5 moraine formation in the za mnichem valley the lg4 stage is related to the climate cooling during the younger dryas greenland stadial 1 lgm elas reconstructed for the biala woda and sucha woda panszczyca glaciers were located at 1460 1480 m a s l during the oldest dryas stages the ela in the high tatras rose from 1600 to 1650 m a s l in the rybi potok valley and from 1700 to 1800 m a s l in the roztoka piec stawow polskich valley the younger dryas ela depending on glacier s exposition was located between 1950 and 2000 m a s l climate modelling results show that the lgm glaciers maximum advance could have advanced in the high tatras when the mean annual temperature was lower than today by 11 12 c and precipitation was reduced by 40 60 during the lateglacial stages the temperature decrease in the study area changed from 10 c during the oldest dryas to 6 c during the younger dryas and precipitation lowering decreased from 50 to 30 or even 10 respectively compare to modern conditions

the little ice age in iberian mountains abstract the little ice age lia is known as one of the coldest stages of the holocene most records from the northern hemisphere show evidence of significantly colder conditions during the lia which in some cases had substantial socio economic consequences in this study we investigated the magnitude and timing of climate variability during the lia in the mountains of the iberian peninsula based on a wide range of natural records including from glacial periglacial and lacustrine peatland areas fluvial alluvial deposits speleothems and tree rings historical documents and early instrument data the onset of the lia commenced in approximately ce 1300 and cold conditions with alternating moisture regimes persisted until approximately ce 1850 the environmental responses ranged from rapid e g tree rings to delayed e g glaciers the colder climate of the lia was accompanied by severe droughts floods and cold heat waves that showed significant spatio temporal variation across the iberian mountains several phases within the lia have been detected including a 1300 1480 increasing cooling with moderate climate oscillations b 1480 1570 relatively warmer conditions c 1570 1620 gradual cooling d 1620 1715 coldest climate period of the lia particularly during the maunder minimum with temperatures approximately 2 c below those at present e 1715 1760 warmer temperatures and a low frequency of extreme events f 1760 1800 climate deterioration and more climate extremes i e cold and heat waves floods and droughts g 1800 1850 highly variable climate conditions alternating with stability 1800 1815 extreme events 1815 1835 and a slight trend of warming associated with intense hydrometeorological events 1835 1850 h since 1850 a gradual staggered increase in temperature of approximately 1 c post lia warming has led to substantial changes in geo ecological dynamics mainly through shrinking of the spatial domain affected by cold climate processes

did pyrenean glaciers dance to the beat of global climatic events evidence from the wurmian sequence stratigraphy of an ice dammed palaeolake depocentre in andorra the ice marginal depositional sequence of la massana provides a chronostratigraphic benchmark for reconstructing the wurmian glacial evolution of the valira catchment in andorra se pyrenees the sedimentary record of andorra confirms the asynchronous chronology of glacier fluctuations in different parts of the pyrenean mountain range a major ice recession occurred at the end of marine isotope stage mis 4 high magnitude valley glacier fluctuations during mis 3 constitute another important finding major readvances occurred toward the end of mis 3 whereas mis 2 in particular the global last glacial maximum or lgm featured sharp contrasts in ice recession rates between pyrenean valleys substantial distances separated mis 4 glacier fronts the wurmian maximum ice extent or mie from those reached during the global lgm in contrast to situations in the eastern pyrenees where wurmian mie and global lgm ice fronts nearly coincided overall the valira glaciers reveal patterns that are more similar to those recorded elsewhere in the western and central pyrenees than in the eastern pyrenees the rapid fluctuations recorded by andorran glaciers during the second half of the wurm also suggest a response to global forcing events such as heinrich events in the north atlantic

rapid age assessment of glacial landforms in the pyrenees using schmidt hammer exposure dating shed schmidt hammer sh sampling of 54 10 be dated granite surfaces from the pyrenees reveals a clear relationship between exposure and weathering through time n 52 r 2 0 96 p 0 01 and permits the use of the sh as a numerical dating tool to test this10 be sh calibration curve 100 surfaces were sampled from five ice front positions in the tet catchment eastern pyrenees with results verified against independent 10 be and 14 c ages gaussian modelling differentiates holocene 9 4 0 6ka younger dryas 12 6 0 9ka oldest dryas 16 1 0 5ka last glacial maximum lgm 24 8 0 9ka and wurmian maximum ice extent stages mie 40 9 1 1ka these data confirm comparable glacier lengths during the lgm and mie 300m difference in contrast to evidence from the western pyrenees 15km reflecting the relative influence of atlantic and mediterranean climates moreover pyrenean glaciers advanced significantly during the lgm with a local maximum at 25ka driven by growth of the laurentide ice sheet southward advection of the polar front and a solar radiation minimum in the northern hemisphere this calibration curve is available online http shed earth to enable wider application of this method throughout the pyrenees

late quaternary ice sheet extents in northeastern germany inferred from surface exposure dating abstract we determined in situ cosmogenic 10 be ages for 11 boulders on the hoher flaming ice marginal belt and five boulders on the gerswalder moraine a recessional moraine of the pomeranian stage previous time estimations for the deposition of these moraines along the southern margin of the scandinavian ice sheet sis in northeastern germany are mostly based on geomorphology and stratigraphy and on few radiocarbon dates and recently published surface exposure ages in the case of the pomeranian moraine our new exposure ages range from 21 7 1 2 10 be ka to 172 6 6 0 10 be ka for the hoher flaming ice marginal belt the wide range of exposure ages may reflect episodic ice marginal belt modification due to intensified erosion by meltwater channeled in the baruther urstromtal ice marginal valley accompanied by long lasting erosional processes like solifluction and aeolian deflation for the gerswalder moraine our new exposure ages range from 12 3 0 6 10 be ka to 16 6 1 0 10 be ka excluding the youngest sample ber 97 03 we calculated error weighted mean ages ranging from 15 2 0 5 10 be ka to 16 0 0 5 10 be ka n 4 depending on choice of scaling methods surface erosion and snow cover these results firmly establish the position of the southern margin of the sis in northeastern germany during the gerswalder substage a recessional phase of the pomeranian stage

rock glacier development in the northern calcareous alps at the pleistocene holocene boundary abstract relict rock glaciers provide information on past discontinuous permafrost and former mean annual air temperatures a lack of records showing former permafrost distribution along the northern alpine fringe prompted the investigation and numerical dating of a belt of relict rock glaciers in the karwendel mountains of the northern calcareous austrian alps in two neighbouring cirques that were still glaciated during the early younger dryas eleven 36cl exposure ages from boulder surfaces were obtained the ages imply the onset of rock glacier activity around 12 3 ka with subsequent stabilization and permafrost melt out no later than 10 1 ka hence rock glacier formation coincided with glacier retreat in the cirques around the mid younger dryas and continued into the early holocene as permafrost induced features the rock glacier termini indicate the local past lower limit of discontinuous permafrost in open cirque floors at 2000 m asl which is around 400 m lower than during the mid twentieth century at comparable locations in the karwendel mountains thus a mean annual air temperature reduction of 2 6 to 3 8 c relative to the mid twentieth century is inferred based on a minimum glacier equilibrium line altitude in the cirques a summer temperature reduction of less than 2 6 to 1 8 c is shown suggesting an increased seasonality at the time of rock glacier activity

mountain glacier evolution in the iberian peninsula during the younger dryas abstract we review the evolution of glaciers in the iberian mountains during the younger dryas 12 9 11 7 ka following the chronology of greenland stadial 1 gs1 and compare with available environmental and climate data to investigate glacier dynamics during cold stadial episodes the best examples of younger dryas moraines are found in the central pyrenees involving short ice tongues up to 4 km in length in the highest massifs above 3000 m a s l of the southern versant small cirque glaciers and rock glaciers formed during the yd occurred in other pyrenean massifs in the cantabrian range and in the gredos and guadarrama sierras central range as indicated by several rocky polished thresholds that were ice free at the beginning of the holocene although some former rock glaciers were re activated during the younger dryas glacial activity was limited in the southernmost part of the iberian peninsula sierra nevada most iberian records show vegetation changes during the yd characterized by a forest decline and an expansion of shrubs mainly juniperus and steppe herbs although the vegetation response was not homogeneous because of variable resilience among ecosystems available records also document a variable lake response in terms of hydrology and productivity with a decrease in sedimentation rates and organic productivity in most high altitude lakes and increases in salinity and relatively lower lake levels at lower altitudes the impact of the younger dryas on the coastal environment was almost negligible but it was responsible for a brief cessation in sea level rise high resolution analyses of new speleothem records have documented a double structure for the yd with an earlier drier phase followed by a relatively more humid period the review of geomorphological evidence demonstrates a strong latitudinal control of glacial activity during the yd with more intense development in the northern than in the southern regions the increase in humidity during the second phase of the yd in southern latitudes could have been a decisive factor for glacier advance in the northern iberian mountains

mid holocene glacial activity in the pyrenees radiocarbon dating of sediments from a bog at c 2100 m in the cirque de troumouse provides the first reliable dating of holocene glacier fluctuations in the pyrenees the oldest organic material in the bog provides a maximum date 5190 90 bp for moraines immediately downvalley which are either lateglacial or more probably holocene in age bracketing dates on laminated glacioacustrine sediments in the bog indicate a neoglacial event between 4955 90 and 4654 60 bp which was probably contemporaneous with moraine ridges immediately upvalley more recent neoglacial events as yet undated are indicated by younger silt rich sediments in the bog and two younger moraine sets on the cirque floor at altitudes of c 2250 2350 m little ice age events were more restricted in extent and are recorded by younger moraines at c 2360 and at c 2650 m resting on and immediately below the cirque wall