variations in alaska tidewater glacier frontal ablation 1985 2013 our incomplete knowledge of the proportion of mass loss due to frontal ablation the sum of ice loss through calving and submarine melt from tidewater glaciers outside of the greenland and antarctic ice sheets has been cited as a major hindrance to accurate predictions of global sea level rise we present a 28 year record 1985 2013 of frontal ablation for 27 alaska tidewater glaciers representing 96 of the total tidewater glacier area in the region calculated from satellite derived ice velocities and modeled estimates of glacier ice thickness we account for cross sectional ice thickness variation long term thickness changes mass lost between an upstream fluxgate and the terminus and mass change due to changes in terminus position the total mean rate of frontal ablation for these 27 glaciers over the period 1985 2013 is 15 11 3 63gta 1 two glaciers hubbard and columbia account for approximately 50 of these losses the regional total ablation has decreased at a rate of 0 14gta 1 over this time period likely due to the slowing and thinning of many of the glaciers in the study area frontal ablation constitutes only 4 of the total annual regional ablation but roughly 20 of net mass loss comparing several commonly used approximations in the calculation of frontal ablation we find that neglecting cross sectional thickness variations severely underestimates frontal ablation

accelerator mass spectrometer ages for the younger dryas event in atlantic canada abstract in atlantic canada bulk sediment dates for the onset of a late glacial cooling widely regarded as the younger dryas event are highly variable ranging from 14 300 270 to 10 800 100 yr b p we present the first accelerator mass spectrometer ams 14c dates from atlantic canada at or close to the boundaries of this event from six sites in new brunswick and nova scotia the mean of five dates places the onset of this cooling at ca 10 770 yr b p the inclusion of a sixth perhaps anomalously old date changes the mean to 10 880 yr b p the termination averages three dates ca 10 000 yr b p these dates place the timing of the younger dryas event in atlantic canada closer in line with the traditional chronozone boundaries of 11 000 and 10 000 yr b p in northwest europe

chronology and directions of late glacial paleoenvironmental changes a multi proxy study on sediments of lake slone se poland the article presents the results of a multi proxy study on sediments of lake slone chelm hills located in the northern peripheral area of the lublin upland se poland the area remained in the periglacial zone with permafrost present in the geological substrate during the last glaciation this paper represents an attempt to determine the directions and intensity of changes in environmental conditions during the late glacial it also attempts to reconstruct lake development conditions within the area unaffected by the extent of the ice sheet the aim of the study was to investigate bottom sections of two sediment profiles representing the period of late glacial lake mire sedimentation occurring in varying thermal and humidity conditions conditions were indicated by lithological variations in the sediments and the content of micro and macrofossils the latter were identified based on palynological and malacological analyses as well as by subfossil ostracoda and cladocera analysis the chronology of the identified paleoenvironmental changes was determined based on the results of paleobotanical analysis in correlation with radiocarbon dating conventional and ams of the selected sediment layers the results were compared to other sites from north central europe and to the well dated laminated sediments sequences from the nearest late glacial site at perespilno it was estimated that the development of lake slone probably had its origin in the older dryas the development of the lake basin in turn is associated with specific processes of disappearance of permafrost in the upper cretaceous bedrock

iceberg calving flux and mass balance of the austfonna ice cap on nordaustlandet svalbard 1 satellite radar interferometry 60 mhz airborne ice penetrating radar data and visible band satellite imagery were used to calculate the velocity structure ice thickness and the changing ice marginal extent of austfonna 8000 km2 and 2500 km3 the largest ice cap in the eurasian arctic ice cap motion is generally less than about 10 m a 1 except where faster flowing curvilinear features with velocities of several tens to over 200 m a 1 are present most drainage basins of austfonna have undergone ice marginal retreat over the past few decades at an average of a few tens of meters per year integrating margin change around the whole ice cap gives a total area loss of about 10 km2 a 1 iceberg flux from the marine margins of austfonna is about 2 5 0 5 km3 a 1 water equivalent about 45 of the total calving flux from the whole svalbard archipelago when mass loss by iceberg production is taken into account the total mass balance of austfonna is negative by between about 2 5 and 4 5 km3 a 1 this iceberg flux represents about 33 5 of total annual mass loss from austfonna with the remainder lost through surface ablation iceberg flux should be included in calculations of the total mass balance of the many large arctic ice caps including those located in the russian and canadian arctic that end in tidewater the neglect of this term has led to underestimates of mass loss from these ice caps and thus to underestimates of the contribution of arctic ice caps to global sea level rise

glacier velocities and dynamic ice discharge from the queen elizabeth islands nunavut canada recent studies indicate an increase in glacier mass loss from the canadian arctic archipelago as a result of warmer summer air temperatures however no complete assessment of dynamic ice discharge from this region exists we present the first complete surface velocity mapping of all ice masses in the queen elizabeth islands and show that these ice masses discharged 2 6 0 8 gt a 1 of ice to the oceans in winter 2012 approximately 50 of the dynamic discharge was channeled through non surge type trinity and wykeham glaciers alone dynamic discharge of the surge type mittie glacier varied from 0 90 0 09 gt a 1 during its 2003 surge to 0 02 0 02 gt a 1 during quiescence in 2012 highlighting the importance of surge type glaciers for interannual variability in regional mass loss queen elizabeth islands glaciers currently account for 7 5 of reported dynamic discharge from arctic ice masses outside greenland

age distribution and stratigraphy of glacier peak tephra in eastern washington and western montana united states tephra layers from williams lake fen wildcat lake and east wenatchee washington and kearns basin lost trail pass sheep mountain bog and marys frog pond montana were analyzed by electron mi

fluctuations of the weichselian ice sheet in sw iceland a glaciomarine sequence from sudurnes seltjarnarnes abstract sedimentological and palaeontological studies in reykjavik sw iceland show that the glaciation history during the late pleistocene was characterized by a fluctuating glacier flowing wnw from reykjanes peninsula new 14c dates show that marine deposition took place in coastal regions during at least three interstadials corresponding to the alesund the bolling and the allerod in scandinavia the oldest of these interstadials is dated to ca 28 000 14c years bp and represents the oldest weichselian interstadial registered in iceland up to now recent studies in gardabaer sw iceland show marine transgression during the bolling earlier work in fossvogur reykjavik indicates that the allerod younger dryas boundary did not coincide with a marked change in the water masses in sw iceland sedimentological studies reveal a relatively high energy environment with near shore and glaciomarine deposition and a period of glacial expansion during the younger dryas the macrofauna foraminifera and ostracod faunas from sediments dated to the late younger dryas on sudumes have been analysed and indicate low arctic to high boreal conditions the sudumes data show that the younger dryas glaciation in the reykjav area took place in a glaciomarine environment the youngest dated sediments of the sudurnes sequence probably postdate this glacier expansion

14c ams measurements from the late weichselian part of the swedish time scale abstract accelerator mass spectrometry measurements on plant macrofossils from the older part of the swedish time scale a chronology spanning over the past 13 000 calendar years indicate a good agreement between varve years and calibrated ages tree rings u th between ca 10 500 and ca 12 000 calendar years bp around 12 000 varve years the varve radiocarbon discrepancies seem to reach a maximum while the u th radiocarbon differences increase steadily

improved age modelling approaches as exemplified by the revised chronology for the central european varved lake soppensee abstract one of the key factors in understanding past climate change is the development of robust age models that have sufficient chronological precision for comparing different palaeoclimate archives while retaining accuracy recent developments in bayesian age modelling are applied here to the swiss varve lake soppensee we develop revised age models for this sequence using the available stratigraphic information to constrain the calibrated radiocarbon ages we begin by using stratigraphical order as the only constraint and then sequentially increase the information incorporated into the model using relative varve age sample depth and varying depositional models within this bayesian framework we develop internally robust models that significantly improve the dating precision and are applicable to both varved and non varved sequences we then compare the model output to wider chronological information such as the age of the laacher see tephra in order to test the model accuracy the results of this exercise suggest that these methods can be used to build very reliable improved age models in a variety of records

bio and chronostratigraphy of the lateglacial in the eifel region germany abstract in recent years enormous success has been achieved in varve counting of the eifel maar lakes but a detailed correlation with the biostratigraphy has been missing in this paper we present new palynological results of the lateglacial sequences from holzmaar lake and meerfelder maar lake based on annually laminated sediments in particular the meerfelder maar has great potential because in contrast to the holzmaar the sequence between the ulmener maar tephra 11 000 varve years bp and the laacher see tephra 12 880 varve years bp including the younger dryas is undisturbed and complete therefore we currently use the meerfelder maar chronology brauer et al 1999b as an independent varve calendar for the biostratigraphy of the lateglacial the palynological signals of both maar lakes are in good agreement and can easily be correlated with one another and with type sections type regions in northwestern germany and jutland the sequences of the eifel maar lakes have the quality of hypostratotypes with regional biozones based on an absolute time scale

geochemistry of the peat bog at etang de la gruere jura mountains switzerland and its record of atmospheric pb and lithogenic trace metals sc ti y zr and ree since 12 370 14 c yr bp a 650 cm core from a swiss bog represents 12 370 14c years of peat accumulation and provides the first complete record of atmospheric pb deposition for the entire holocene excess non atmospheric sr in the peat was calculated by normalizing sr sc to crustal abundance this was used to differentiate between the ombrogenic section of the bog in which inorganic solids are supplied exclusively by atmospheric deposition and the minerogenic zone where mineral water interactions contribute metals to the peat while sediment dissolution contributes significantly to the sr inventory of the minerogenic section of the peat profile there is no measurable effect of this process on the pb burden isotopic analyses 204pb 206pb 207pb 208pb show that effectively all of the pb in the peat profile was supplied exclusively from the atmosphere to separate natural and anthropogenic pb sc was selected over ti y zr hf and ree as a conservative reference element which is supplied by soil dust aerosols derived from rock weathering enrichment factors ef were calculated using the pb sc ratio in the peat samples normalized to the natural background pb sc which is found in peats dating from 8030 to 5320 14c yr bp the results show that anthropogenic source have dominated the supply of atmospheric pb to the peat core continuously since 3000 14c yr bp the aerosols supplied to the bog can be divided into 3 classes a pre anthropogenic older than 3000 14c yr bp with pb ef 1 194 b pre industrial dating from 3000 240 14c yr bp with pb ef 2 but 20 and 206pb 207pb 1 179 elevated soil dust fluxes are observed at 5320 8230 and 10 590 14c yr bp the latter corresponds to the younger dryas aluminum zr hf and ree sc ratios also are elevated at the same depths suggesting differences in particle size wind strength or source regions pre anthropogenic aerosols deposited since 8230 14c yr bp reveal pb sc which is significantly higher and 206pb 207pb which is less radiogenic than during the early holocene while the trend toward increasing pb sc could be due to chemical weathering and soil development this could not explain the shift in pb isotopic composition the changes which took place at 8230 14c bp therefore may be related to a large scale climatic reorganization which at present is poorly understood

characterizing interannual variability of glacier dynamics and dynamic discharge 1999 2015 for the ice masses of ellesmere and axel heiberg islands nunavut canada landsat 7 and radarsat 1 radarsat 2 satellite images are used to produce the most comprehensive record of glacier motion in the canadian high arctic to date and to characterize spatial and temporal variability in ice flow over the past 15 years this allows us to assess whether dynamically driven glacier change can be attributed to surging or pulsing or whether other mechanisms are involved radar velocity mapping allows annual regional dynamic discharge iceberg calving to be calculated for 2000 and the period 2011 2015 yielding a mean regional discharge of 2 21 0 68 gt a 1 and velocities derived from feature tracking of optical imagery allow for annual dynamic discharge to be calculated for select glaciers from 1999 to 2010 since 2011 several of the major tidewater terminating glaciers within the region have decelerated and their dynamic discharge has decreased trinity and wykeham glaciers prince of wales icefield represent a notable departure from this pattern as they have generally accelerated over the study period the resulting increase in dynamic discharge from these glaciers entirely compensates within error limits for the decrease in discharge from the other tidewater glaciers across the study region these two glaciers accounted for 62 of total regional dynamic discharge in winter 2015 compared to 22 in 2000 demonstrating that total ice discharge from the canadian high arctic can be sensitive to variations in flow of just a few tidewater glaciers

ams radiocarbon dating and varve chronology of lake soppensee 6000 to 12000 14c years bp for the extension of the radiocarbon calibration curve beyond 10000 14c y bp laminated sediment from lake soppensee central switzerland was dated the radiocarbon time scale was obtained using accelerator mass spectrometry ams dating of terrestrial macrofossils selected from the soppensee sediment because of an unlaminated sediment section during the younger dryas 10000 11000 14c y bp the absolute time scale based on counting annual layers varves had to be corrected for missing varves the soppensee radiocarbon verve chronology covers the time period from 6000 to 12000 14c y bp on the radiocarbon time scale and 7000 to 13000 calendar y bp on the absolute time scale the good agreement with the tree ring curve in the interval from 7000 to 11450 cal y bp cal y indicates calendar year proves the annual character of the laminations the ash layer of the vasset killian tephra massif central france is dated at 8230 140 14c y bp and 9407 44 cal y bp the boundaries of the younger dryas biozone are placed at 10986 69 cal y bp younger dryas preboreal and 1212 86 cal y bp allerod younger dryas on the absolute time scale the absolute age of the laacher see tephra layer dated with the radiocarbon method at 10 800 to 11200 14c y bp is estimated at 12350 135 cal y bp the oldest radiocarbon age of 14190 120 14c y bp was obtained on macrofossils of pioneer vegetation which were found in the lowermost part of the sediment profile for the late glacial the offset between the radiocarbon 10000 12000 14c y bp and the absolute time scale 11400 13000 cal y bp in the soppensee chronology is not greater than 1000 years which differs from the trend of the u th radiocarbon curve derived from corals

impact of earthquakes on agriculture during the roman byzantine period from pollen records of the dead sea laminated sediment the dead sea region holds the archives of a complex relationship between an ever changing nature and ancient civilisations regional pollen diagrams show a roman byzantine period standing out in the recent millennia by its wetter climate that allowed intensive arboriculture during that period the dead sea formed laminites that display mostly a seasonal character a multidisciplinary study focused on two earthquakes 31 bc and ad 363 recorded as seismites in the ze elim gully a unit iii which has been well dated by radiocarbon in a previous study the sampling of the sediment was done at an annual resolution starting from a few years before and finishing a decade after each earthquake a clear drop in agricultural indicators especially olea and cereals is shown these pollen indicators mostly reflect human activities in the judean hills and coastal oases agriculture was disturbed in large part of the rift valley where earthquake damage affected irrigation and access to the fields it took 4 to 5 yr to resume agriculture to previous conditions earthquakes must be seen as contributors to factors damaging societies if combined with other factors such as climatic aridification disease epidemics and political upheaval they may lead to civilisation collapse

responses to rapid warming at termination 1a at gerzensee central europe primary succession albedo soils lake development and ecological interactions the transition from the oldest dryas to the bolling around 14 685 cal yr bp was a period of extremely rapid climatic warming from a single core of lake marl taken at gerzensee switzerland we studied the transition in stable isotopes of oxygen and carbon on bulk sediment and charophyte remains as well as on monospecific samples of ostracods after pisidium a in addition pollen chironomids and cladocera were analyzed the 18o record serves as an estimate of mean air temperature and by correlation to the one from ngrip in greenland it provides a timescale the timing of responses the statistically significant zone boundaries of the biostratigraphies are telescoped at the rapid increase of about 3 in 18o at the onset of bolling biotic responses may have occurred within sampling resolution 8 to 16 years although younger zone boundaries are less synchronous gradual and longer lasting responses include complex processes such as primary or secular succession during the late glacial interstadial of bolling and allerod two stronger and two weaker cool phases were found biological processes involved in the responses occurred on levels of individuals e g pollen productivity of populations increases or decreases immigration or extinction and on the ecosystem level species interactions such as facilitation or competition abiotic and biotic interactions include pedogenesis nitrogen fixation nutrient cycling catchment hydrology water chemistry of the lake and albedo controlled by the transition from tundra to forest for the swiss plateau this major change in vegetation induced a change in the mammal fauna which in turn led to changes in the tool making by paleolithic people

mass balance of the greenland ice sheet at high elevations comparison of ice discharge from higher elevation areas of the entire greenland ice sheet with total snow accumulation gives estimates of ice thickening rates over the past few decades on average the region has been in balance but with thickening of 21 centimeters per year in the southwest and thinning of 30 centimeters per year in the southeast the north of the ice sheet shows less variability with average thickening of 2 centimeters per year in the northeast and thinning of about 5 centimeters per year in the northwest these results agree well with those from repeated altimeter surveys except in the extreme south where we find substantially higher rates of both thickening and thinning

basin scale partitioning of greenland ice sheet mass balance components 2007 2011 a r t i c l e i n f o a b s t r a c t the current deficit in greenland ice sheet mass balance is due to both a decrease in surface mass balance smb input and an increase in ice discharge d output while smb processes are beginning to be well captured by observationally constrained climate modeling insight into d is relatively limited we use insar derived velocities in combination with ice thickness observations to quantify the mass flux f across a flux perimeter around the ice sheet at 1700 m elevation to quantify d we correct f for smb as well as changes in volume due to ice dynamics in the area downstream of the gate using a 1961 1990 reference climatology smb field from the mar regional climate model we quantify ice sheet mass balance within eighteen basins we find a 2007 2011 mean d of 515 57 gt yr 1 we find a 2007 2011 mean total mass balance of 262 21 gt yr 1

numerical modeling of the development of u shaped valleys by glacial erosion the steep sided valleys and overdeepened basins of alpine landscapes are well known products of glaciation yet relatively little is known about how the dynamics of ice flow and glacial erosion interact to give rise to such landforms by linking a finite element model for ice flow through a glacier cross section with an erosion model it is possible to investigate the development of one of the most striking glacial landforms the u shaped valley in addition to providing a detailed understanding of landform development such modeling provides a way to test current understanding of the controls on glacial sliding and erosion to simulate valley development i first model flow through an initial glacier cross section and calculate the glaciological parameters that govern erosion i then numerically simulate erosion to produce a modified transverse profile for which a new flow field and erosion pattern are computed a number of iterations permits examination of the progressive transformation of cross section form which can be compared with field data model predictions of the cross section flow field are in close accord with data from the athabasca glacier and include marked lateral variations in sliding velocity with an erosion law dependent on basal velocity the model predicts the rapid transformation of a v shaped cross section into a recognizably glacial form over a time period on the order of 10 4 yr and the eventual development of a steady state quasi parabolic glacier cross section better agreement with empirical data from glaciated valleys is obtained by including temporal variations in ice discharge in order to mimic the characteristics of 100 000 yr glacial cycles the high discharge phase dominates form development and at low discharges cross section form is essentially inherited from the central part of the form that developed during the preceding high discharge phase

a magnetostratigraphic comparison between 14c years and varve years during the late weichselian indicating significant differences between the time scales a 14c dated magnetostratigraphy of absolute declination and inclination between 12500 and 10000 14c yr bp was recently developed for southern sweden recently also the swedish geochronological time scale based on c 11 500 annually deposited clay varves was connected with the present it should therefore be possible to compare the two chronologies with a reliable magnetostratigraphic record in an appropriate clay varve section we have found such a site within the middle swedish end moraine zone statistical correlations between the two independently dated time scales suggest that at 10500 10200 14cy r bp the varve chronology exceeds the 14c chronology by the order of 500 600 varve yr other correlations indicate that the difference between the two chronologies was less at 11000 14c yr bp and further correlations between the time scales at 12000 14c yr bp suggest that the difference between the chronologies increased steadily from 12000 to 10000 14c yr bp if these correlations are correct they imply that the 14c production rate increased steadily during the late weichselian

absolute dating of the late glacial period in switzerland using annually laminated sediments abstract results of a high resolution late glacial ams 14 c chronology from rotsee central switzerland have given evidence that the atmospheric radiocarbon concentration was not constant between 13 000 and 9500 yr b p this resulted in three marked phases of constant radiocarbon age at 12 700 at 10 000 and at 9500 yr b p new results of a late glacial varve chronology from soppensee central switzerland suggest that the younger two phases of constant 14 c age each had a duration of ca 400 calendar years the length of the late glacial chronozones has been calculated on the basis of these replicate varve counts and a comparison with their estimated duration in radiocarbon years shows that the estimated duration of the chronozones bolling ca 800 calendar yr vs 1000 14 c yr and younger dryas ca 900 calendar yr vs 1000 14 c yr agree with the expected time span whereas the estimated duration of the allerod chronozone ca 400 calendar yr vs 1000 14 c yr is substantially shorter than expected furthermore a tentative comparison of varve ages and 14 c ages suggests that the varve chronology is more than 1000 yr offset toward older ages from the radiocarbon chronology during the late glacial period

a calendar age estimate of the younger dryas holocene boundary at krakenes western norway the younger dryas holocene transition yd h in the sediments of krakenes lake western norway is well marked both lithologically and palaeobiologically at 756 5 cm in the investigated core a ser

the distribution and flow characteristics of surge type glaciers in the canadian high arctic a systematic review of 1959 60 aerial photography and 1999 2000 landsat 7 imagery has identified 51 surge type polythermal glaciers in the canadian high arctic these were identified from the presence of features such as looped medial moraines intense folding visible at the surface rapid terminus advance heavy surface crevassing and high surface velocities these observations suggest that surging glaciers are much more common than previously believed in the canadian high arctic where only six surge type glaciers have previously been described of the 51 surge type glaciers identified in this study 15 were observed in the active phase in the 1959 60 and or 1999 2000 imagery the most dramatic advances have occurred on western axel heiberg island where iceberg good friday bay and airdrop glaciers have all advanced by 4 7 km between1959 and 1999 for glaciers with repeat landsat 7 coverage from 1999 and 2000 image correlation software was used to determine the magnitude and spatial distribution of surge velocities for example mittie glacier on manson icefield was moving at a rate of up to 1 kma over a distance of at least 25 km back from its terminus the terminus of this glacier has advanced by at least 4 km since 1959 and the glacier was observed to be heavily crevassed during overflights in april 2000 with clear signs of surface lowering of 10 25 m indicated by a strandline

the mineral magnetic properties of an annually laminated holocene lake sediment sequence in northern sweden detailed mineral magnetic measurements were conducted on a 9000 year varved lake sediment sequence in northern sweden lake sarsjon the results demonstrate that the paramagnetic susceptibility reflects the concentration of detrital minerogenic material in the lake sediments which is controlled to a large extent by the intensity of the spring snow melt in contrast the concentration of ferrimagnetic magnetite reflected by initial magnetic susceptibility and magnetic hysteresis parameters is positively correlated to the concentration of organic carbon which is most likely of an autochthonous origin this magnetite has magnetic properties that are characteristic of stable single domain magnetite grains produced by magnetotactic bacteria the paramagnetic susceptibility record clearly points to a climatic excursion in the early holocene between 6100 174 bc and 5700 167 bc which can be correlated to an d18o excursion a cold event in the greenland ice cores and lake sediments in southern germany an

environmental response to climatic and volcanic events in central europe during the weichselian lateglacial this paper reviews major results of the recent german research priority program changes of the geo biosphere during the last 15 000 years a contribution to pages focussing on changes of the geo biosphere during the weichselian lateglacial different continental archives such as annually laminated lacustrine sediments floodplain sediments and speleothems were used to reconstruct environmental response to climatic changes and the laacher see eruption event at ca 12 900 cal bp special emphasis is paid to establish a reliable time control using varve counting high precision radiocarbon dating of tree ring series and ams radiocarbon dating of terrestrial plant macrofossils recovered from lacustrine sediments to correlate and synchronize large scale environmental changes and events in central europe

form and flow of the devon island ice cap canadian arctic 1 in this study 3370 km of 100 mhz ice penetrating radar data were acquired from devon ice cap arctic canada bed returns were obtained from 90 of flight tracks mean crossing point errors in ice surface elevation and ice thickness were 7 8 m digital elevation models of ice cap surface and bed elevation and ice thickness were produced and can be used as boundary conditions in numerical modeling devon ice cap including 1960 km2 of contiguous stagnant ice to its west is 14 010 km2 the ice cap proper is 12 050 km2 its largest drainage basin is 2630 km2 the ice cap crest has a maximum measured elevation of 1921 m maximum recorded ice thickness is 880 m ice cap volume is 3980 km3 about 10 mm sea level equivalent the bed 8 of which lies below sea level is an upland plateau dissected by steep sided valleys that control the locations of the major outlet glaciers which dominate ice cap drainage about 73 km 4 of the ice cap margin ends in tidewater the margin is not floating icebergs of 100 m were observed offshore only a single outlet glacier showed signs of past surge activity all major outlet glaciers along the eastern ice cap margin have retreated 1 3 km since 1960 synthetic aperture radar interferometic velocity structure shows slow undifferentiated flow predominating in the west and center with fast flowing outlet glaciers and intervening slow flowing ridges typical elsewhere outlet glacier velocities are 7 10 times higher than in areas of undifferentiated flow this velocity structure of fast flowing units within slower flowing ice appears typical of many large 103 km2 arctic ice caps

rapid changes in ocean circulation and atmospheric radiocarbon a latitude depth coupled global ocean ice atmosphere model is extended to include a simple biosphere component a physically reasonable adjustment of runoff into the north atlantic is invoked to achieve a transient response to glacial meltwater perturbations which closely resembles the younger dryas climate event we then investigate the evolution of the isotopic ratio of atmospheric radiocarbon 14c due to the rapid changes of deep ocean circulation when the north atlantic branch of the conveyor belt circulation is interrupted the oceanic uptake of radiocarbon is reduced resulting in an increase of atmospheric 14c by about 35 the reduction of ventilation in the north atlantic is partly compensated by an increase of the 14c ratios of the biosphere the southern ocean and the upper ocean above 1000 m depth a plateau of the 14c year calendar year relation can be generated at the time of the rapid reinitiation of deep ocean ventilation which begins coincident with the major temperature increase and lasts for about 60 years it is hence significantly shorter than that found by analyzing tree rings during the termination of younger dryas longer than 400 years a sensitivity study reveals that the duration of the plateau depends strongly on the transient evolution of the gas exchange rate and can increase to 150 300 years if changes of pco2 or sea ice coverage are taken into account

intra and inter annual variability in dynamic discharge from the academy of sciences ice cap severnaya zemlya russian arctic and its role in modulating mass balance

late glacial climatic oscillations as recorded in swiss lake sediments regional pollen assemblage zones for the late glacial period of the swiss plateau are introduced and defined they include four major zones artemisia juniperus hippophae betula pinus paz with several subzones pollen and oxygen isotope analyses on lacustrine sediments from several lakes in the area reveal four distinct phases of climatic oscillation in the time period of 13 000 9500 yr bp the first oscillation termed the aegelsee fluctuation occurs shortly before 12 000 yr bp and varve counts suggest its duration was ca 100 yr it is characterised by a short decrease in the oxygen isotopes as well as a short increase in nap associated with a depression in birch pollen values the second oscillation which occurs in the 18o record shortly before the deposition of the laacher see tephra ca 11 000 yr bp is termed the gerzensee fluctuation it occurs during a pine dominated phase and its vegetational effects cannot be determined palynologically the most prominent regressive phase is the younger dryas biozone ca 10 700 10 000 yr bp characterised by an increase in heliophilous nap and low 18o values the younger dryas biozone can often be subdivided palynologically into two parts a first part rich in grasses and juniper and a second part with higher filipendula and birch values during the preboreal biozone another distinct oscillation is evidenced only in the oxygen isotope ratios comparison of the swiss oxygen isotope profiles with the greenland dye 3 record suggests that not only the three major shifts in the 18o curves but also the minor ones are closely comparable suggesting some common climatic control

regional and global volumes of glaciers derived from statistical upscaling of glacier inventory data 1 very few global scale ice volume estimates are available for mountain glaciers and ice caps although such estimates are crucial for any attempts to project their contribution to sea level rise in the future we present a statistical method for deriving regional and global ice volumes from regional glacier area distributions and volume area scaling using glacier area data from 123 000 glaciers from a recently extended world glacier inventory we compute glacier volumes and their sea level equivalent sle for 19 glacierized regions containing all mountain glaciers and ice caps on earth on the basis of total glacierized area of 741 103 68 103 km2 we estimate a total ice volume of 241 103 29 103 km3 corresponding to 0 60 0 07 m sle of which 32 is due to glaciers in greenland and antarctica apart from the ice sheets however our estimate is sensitive to assumptions on volume area scaling coefficients and glacier area distributions in the regions that are poorly inventoried i e antarctica north america greenland and patagonia this emphasizes the need for more volume observations especially of large glaciers and a more complete world glacier inventory in order to reduce uncertainties and to arrive at firmer volume estimates for all mountain glaciers and ice caps

land ice teleconnections of cold climatic periods during the last glacial interglacial transition independent calendar year chronologies are a basic requirement for the establishment of high resolution land ice teleconnections the annually laminated meerfelder maar record provides both an independent chronology established by varve counting and high resolution lithological proxy data for the period of the last glacial interglacial transition these data reveal a series of four periods of climatic deterioration coinciding with negative isotopic deviations in the grip record signal thus demonstrating the synchronicity of environment changes in western germany and temperature shifts in greenland the terrestrial data supports a further sub division of the event stratigraphy based on the grip core by introducing the cold event gi 1c2 between 13 500 and 13 400 calendar years bp multiproxy analyses reveal that the environmental response at meerfelder maar was not linear throughout the lateglacial but was modified by local processes a change in the response of the lake environment to climate deterioration was observed during sub stage gi 1b gerzensee oscillation the only event with gradual rather than abrupt transitions the two fold character of the younger dryas as seen in the grip record is more pronounced in the meerfelder maar record this lithological signal occurred with a delay of 60 years to the grip signal and has been linked to a shift in the catchment it is proposed that the trigger for this shift was a trend towards a more humid second half of the younger dryas

high resolution climate signals in the bolling allerod interstadial greenland interstadial 1 as reflected in european tree ring chronologies compared to marine varves and ice core records abstract lateglacial and holocene tree ring chronologies are unique archives which provide various information on past environments on a true annual time scale changes in ring width can be related to past climate anomalies and dendrodated wood provides an ideal source for radiocarbon calibration we present a 1051 year tree ring chronology from the late glacial built from subfossil scots pines pinus sylvestris that grew in different regions of central and southern europe through a series of high precision radiocarbon measurements we obtained a floating radiocarbon chronology which allowed accurate wiggle matching to the intcal98 calibration curve the trees show a coherent pattern in ring width variations throughout central europe and extending into the mediterranean which indicates a strong external climatic factor most probably temperature during the growing season we identified major growth events which appear synchronous with events seen in isotopic and tracer signals in the greenland ice cores and with changes in the strength of upwelling in the cariaco basin

a new lateglacial chronostratigraphic tephra marker for the south eastern alps the neapolitan yellow tuff nyt in langsee austria in the context of a regional biostratigraphy and palaeoclimate langsee is a small meromictic lake in carinthia se alps with partially varved lateglacial sediments the langsee tephra correlates to the neapolitan yellow tuff nyt an eruption from the campanian volcanic province italy this tephra provides a lateglacial chronostratigraphic time marker from central italy across the adriatic sea to the southeastern alps the langsee tephra is discussed in the context of pollen geochemical and microstratigraphical data from a profundal sediment core from langsee the age of 14 120 cal yr bp for the nyt has been accepted from the monticchio chronology the timescale for the lateglacial in the langsee record is based on laminae counts and has been linked to calendar year ages using the nyt tephrachronological marker consequently the mass expansion of betula has been dated at 14 270 cal yr bp the expansion of p sylvestris started concurrent with the nyt and about 180 yr later at 13 940 cal yr bp p sylvestris forests were established the younger dryas biozone at langsee is characterized only by a slight increase in non arboreal pollen and dominated by pine with visible variations only in pine pollen types differentiation of pine pollen types allowed the recognition of three minor fluctuations during the lateglacial interstadial two of these oscillations tentatively have been correlated with the aegelsee and gerzensee oscillations in switzerland as well as with vegetation changes in nw germany

reconstruction of late glacial and early holocene near surface temperature anomalies in europe and their statistical interpretation abstract this paper presents the results of a variational analysis study based on the recently developed method by gebhardt et al to reconstruct paleo temperature fields on the typical scale of climate model output providing the necessary basis for quantitative comparison of reconstructions and model results additionally an extension of the approach takes into account the full statistics of the analysis error of the variational analysis to study the inherent uncertainties of the proxy data representing the imperfect paleo climate information and their impact on the field reconstruction the method is applied to reconstruct realizations of monthly mean temperature anomaly fields in europe for january and july in europe as averages for several time slices in the late glacial and holocene single realizations can differ substantially from the field of expectation values in terms of spatial patterns due to the inherent correlation of the spatial uncertainties of the paleo proxy data additionally the fields of expectation values generally are much smoother than the realizations this indicates that it is misleading to only consider expectation values further the ensembles of realization are used to calculate robust error measures for area mean values which is valuable for the quantitative comparison of the results of different time slices

correlation and synchronisation of lateglacial continental sequences in northern central europe based on annually laminated lacustrine sediments abstract the present study focusses on correlation and synchronisation of weichselian lateglacial varved lake sediments from western germany meerfelder maar eifel region northern germany hamelsee lower saxony central poland lake go ci a z and eastern poland lake perespilno by using varve chronology tephrochronology palynostratigraphy and stable isotopes comparison of the several independent time scales shows that biotic and abiotic parameters respond abruptly and quasi synchronously within the errors of the different chronologies during the younger dryas preboreal transition moreover there is a consensus about the length of the younger dryas cold stage of 1100 1150 varve years in the allerod the prominent laacher see tephra 12 880 varve years bp can be used to fix floating varve chronologies the relative duration of this biozone has been determined in meerfelder maar and hamelsee at between 625 and 670 varve years in the meerfelder maar a combination of continuous varve counting and biostratigraphy has been possible for the almost entire lateglacial the comparison between continental limnic sequences and greenland ice core records should be made on the basis of independent chronologies in both archives it is more practicable to develop regional stratotypes on the continental regions instead of simply using ice cores as stratotypes for the lateglacial for terrestrial european records in this respect annually laminated lacustrine sequences have a great potential

glacier velocities and dynamic discharge from the ice masses of baffin island and bylot island nunavut canada speckle tracking of alos palsar fine beam data from 2007 2011 are used to determine the surface motion of major ice masses on baffin island and bylot island in the southern canadian arctic archipelago glacier velocities are low overall with peaks of 100 m a 1 and means of 20 60 m a 1 common along the main trunk of many outlet glaciers peak velocities on penny and bylot island ice caps tend to occur near the mid sections of their primary outlet glaciers while the fastest velocities on all other glaciers usually occur near their termini due to relatively large accumulation areas draining through narrow outlets estimates of ice thickness at the fronts of tidewater terminating glaciers are combined with the velocity measurements to determine a regional dynamic discharge rate of between 17 mt a 1 and 108 mt a 1 with a mid point estimate of 55 mt a 1 revising downward previous approximations these velocities can be used as inputs for glacier flow models and provide a baseline dataset against which

holocene sea level change on the central west coast of vancouver island british columbia a new holocene relative sea level rsl curve is proposed for the central west coast of vancouver island based on topographic surveys of coastal landforms and the stratigraphy of coastal deposits six study sites are described on vargas island and esowista and ucluth peninsulas and 23 previously unpublished radiocarbon ages that constrain mean sea level msl position are presented a long term rise in rsl from an early holocene 7000 bp lowstand below 3 m asl is documented from dates on tree stumps in the intertidal zone and salt marsh peats and forest floor deposits buried by marine sands and gravels submergence culminated in a stillstand from 6000 to 4800 bp marked by the development of a strandline at 6 m asl msl 3 2 m asl a fall in rsl is documented by a strandline at 4 0 4 5 m asl which dates from 2700 to 2000 bp msl 2 0 m asl little is known of the dynamics of emergence between 4800 and 2700 bp or from 2000 bp to the present although the absence of strandlines below 4 m asl sugges

calendar year age estimates of allerod younger dryas sea level oscillations at os western norway a detailed shoreline displacement curve documents the younger dryas transgression in western norway the relative sea level rise was more than 9 m in an area which subsequently experienced an emergence of almost 60 m the sea level curve is based on the stratigraphy of six isolation basins with bedrock thresholds effort has been made to establish an accurate chronology using a calendar year time scale by 14c wiggle matching and the use of time synchronic markers the vedde ash bed and the post glacial rise in betula birch pollen the sea level curve demonstrates that the younger dryas transgression started close to the allerod younger dryas transition and that the high stand was reached only 200 yr before the younger dryas holocene boundary the sea level remained at the high stand for about 300 yr and 100 yr into holocene it started to fall rapidly the peak of the younger dryas transgression occurred simultaneously with the maximum extent of the ice sheet readvance in the area our results support earlier geophysical modelling concluding a causal relationship between the younger dryas glacier advance and younger dryas transgression in western norway we argue that the sea level curve indicates that the younger dryas glacial advance started in the late allerod or close to the allerod younger dryas transition copyright 2004 john wiley sons ltd

late quaternary records of vegetation and fire in southeastern north carolina from jones lake and singletary lake abstract we conducted fossil pollen charcoal and geochemical analyses of sediment cores from jones lake and singletary lake spanning the last 50 000 cal yr b p to examine the linkages between climate vegetation and fire activity on the atlantic coastal plain and particularly emphasize changes since the last glacial maximum application of the modern analog technique mat to fossil pollen data allowed for quantitative estimates of holocene climate but pleistocene assemblages had no modern analogues preempting their use for quantitative reconstructions the mat data indicate markedly lower mean annual precipitation and temperatures during the late pleistocene relative to the holocene increased charcoal accumulation during interstadials indicates increased fire activity during these warm intervals geochemical data 13c 15n c n and pollen concentrations indicate a sparsely vegetated pleistocene landscape that produced few fires followed by an increase in biomass and fire activity around the lakes during the holocene transition a quercus spp maximum in the early holocene is associated with low charcoal abundances while increased dominance of pinus spp during the middle holocene is associated with dramatic increases in charcoal it is unclear if the quercus pinus transition was the result of changing fire regimes or if the fire regime changed in response to vegetation the regional asynchronicity of the quercus pinus transition may indicate another forcing mechanism besides climate change such as prehistoric human activity is responsible for the ecological change macroscopic charcoal and c n ratios reach unprecedented values during the late holocene possibly as a result of deforestation by both prehistoric native americans and later immigrant populations

intensity gradients and reversals in late glacial environmental change in east central north america abstract radiocarbon dated pollen sites from the allegheny plateau east and the till plains west document significant vegetational and climatic change between 15 000 and 9000 14 c bp south of the great lakes although limited by the problems of no analog vegetation pollen transfer functions tf and response surfaces rs quantify the climatic changes including a cold oscillation chronologically equivalent to the european younger dryas phase i before ca 13 000 14 c bp conditions across the region were similar january 20 to 16 c july 12 c rs or 19 c tf mean annual precipitation 80 to 90 cm year 1 phase iia between ca 13 000 and 11 000 14 c bp n s and e w climate gradients were initiated till plains temperatures increased by ca 8 c in january and by 8 c rs or 2 3 c tf in july plateau increases for january were 3 6 c and for july were 8 c rs or 1 2 c tf precipitation generally increased somewhat phase iib ca 11 000 to 10 000 14 c bp gradients became less pronounced the western sites show a climate reversal january drop of ca 5 to 2 c july drop to ca 1 2 c becoming more like the plateau sites which show a brief small fluctuation this is followed by an abrupt 10 to 20 cm year 1 reduction in precipitation january warming of ca 3 c and continued cooler julys phase iii after 10 000 14 c bp gradients similar to those of today developed the changes in phases iib and iii are probably linked to the drainage history of the great lakes and via that history to the changes on the european continent

rates of change and chronological problems during the late glacial period results of high resolution ams 14c dating of terrestrial plant macrofossils from late glacial and early holocene lake deposits in switzerland show three periods with constant radiocarbon ages these plateaux of constant age occur at 12700 10000 and 9500 y bp a comparison of this radiocarbon chronology with a varve chronology documents discrepancies between the sidereal and the radiocarbon time scale for the late glacial period the age plateaux and the time scale discrepancies have a significant impact on the estimation of rates of change during this period estimates of rates of change can be very misleading if calculated on the basis of radiocarbon ages this is illustrated by an example of estimated rates of late glacial and early holocene palynological change in switzerland

the vegetation and monsoon variations at the desert boess transition belt at midiwan in northern china for the last 13 ka fine resolution palaeovegetation and palaeomonsoon proxies for the last 13 ka have been established at the desert loess transition belt in northern china these are based on pollen organic carbon and 13c analysis of samples from a peat section at midiwan results show that the palaeovegetation underwent nine major changes desert grassland grassland semi desert humid grassland desert sparse wood grassland steppe humid grassland and desert grassland an interval with semi desert humid grassland and desert is associated with rapid oscillation events of cold dry conditions 11200 10600 14c yr bp to cool humid conditions 10600 10200 14c yr bp followed by a change to a cold dry climate 10200 10000 14c yr bp the holocene optimum 10000 7500 14c yr bp and another humid interval 4500 3500 14c yr bp have also been detected in the area during the last 3000 years dry conditions have prevailed and human impact may have affected the location of desert loess transition zone the record there

flow dynamics and iceberg calving rates of devon ice cap nunavut canada the surface velocity field of devon ice cap nunavut canada was mapped using interferometric synthetic aperture radar insar ascending european remote sensing satellite 1 and 2 ers 1 2 tandem mode data were used for the western and southeast sectors and 3 day repeat pass ers 1 imagery for the northeast sector speckle tracking procedures were used with radarsat 1 imagery to obtain surface velocities over the terminus of belcher glacier a major calving front where decorrelation between ers data occurred the insar data highlight a significant contrast in ice flow dynamics between the east and west sides of the ice cap ice movement west of the main north south divide is dominated by relatively uniform sheet flow but three fast flowing outlet glaciers that extend 14 23 km beyond the ice cap margin also drain this region several outlet glaciers that extend up to 60km inland from the eastern margin drain the eastern side of the ice cap the dominant ice flow regimes were classified based on the relationship between the driving stress averaged over a length scale often ice thicknesses and the ratio of surface velocity to ice thickness the mapped distribution of flow regimes appears to depict the spatial extent of basal sliding across the ice cap this is supported by a close relationship between the occurrence of flow stripes on the ice surface and flow regimes where basal sliding was found to be an important component of the glacier motion iceberg calving rates were computed using measured surface velocities and ice thicknesses derived from airborne radio echo sounding the volume of ice calved between 1960 and 1999 was estimated to be 20 5 4 7 km 3 or 0 57km 3 a 1 approximately 89 of this loss occurred along the eastern margin the largest single source is belcher glacier which accounts for 50 of the total amount of ice calved

glacier motion estimation using sar offset tracking procedures two image to image patch offset techniques for estimating feature motion between satellite synthetic aperture radar sar images are discussed intensity tracking based on patch intensity cross correlation optimization and coherence tracking based on patch coherence optimization are used to estimate the movement of glacier surfaces between two sar images in both slant range and azimuth direction the accuracy and application range of the two methods are examined in the case of the surge of monacobreen in northern svalbard between 1992 and 1996 offset tracking procedures of sar images are an alternative to differential sar interferometry for the estimation of glacier motion when differential sar interferometry is limited by loss of coherence i e in the case of rapid and incoherent flow and of large acquisition time intervals between the two sar images in addition an offset tracking procedure in the azimuth direction may be combined with differential sar interferometry in the slant range direction in order to retrieve a two dimensional displacement map when sar data of only one orbit configuration are available

initial stages of laminar calcrete formation by roots examples from the neogene of central spain thin carbonate laminae formed by root activity are common within miocene detrital deposits of the duero and madrid basins the laminae are about 3 cm thick extending several metres laterally and displace the original detrital sediment which ranges in grain size from fine gravel to sandy clay the thickness morphology microstructure and stable isotope compositions of the laminae indicate that they formed by the activities of roots and associated microorganisms within the soil the laminae are similar to those commonly recognised in thick laminar calcrete profiles three types of laminae are recognised differences in the micromorphology of the laminae are explained as reflecting the different organisms involved and whether calcification occurred when the root was alive or decaying the first type occurs in a profile at paracuellos the jarama where the laminae consist of a mosaic of 20 mm calcite crystals whose arrangement indicates that calcification took place in the medulla of the root and probably occurred while the plant was alive in a second type in the villacadima profile laminae comprise calcified root mats whose formation indicates the interplay of roots and fungi calcification of the cell walls and intracellular spaces took place in the cortices of the roots and not in the medullas as revealed by the presence of central pores in every calcified root a third type of lamina is recognised in profiles at vin egra de moran a and consists of mucilaginous sheets coated by needle fibre calcite crystals the occurrence of associated small root casts indicates that formation of the laminae occurred while the root was decaying and was also influenced by fungal activity these laminae occur within poorly developed soils and their formation was controlled by the relationship between sedimentation erosion and soil formation processes thus the occurrence of these laminae interbedded with detrital sediments reflects environments where sedimentation was relatively low and episodic so after the detrital sediment input surfaces were stable and root mats were able to develop renewed sedimentation accounted for the death of the root mats and the development of new ones on the new surfaces where the sedimentation rate is lower the laminae tend to amalgamate and thicker laminar calcrete profiles form with little or no interbedded detrital sediment

ice discharge error estimates using different cross sectional area approaches a case study for the canadian high arctic 2016 17 we analyse the various error sources in the estimation of ice discharge through flux gates distinguishing the cases with ice thickness data available for glacier cross sections or only along the centreline for the latter we analyse the performance of three u shaped cross sectional approaches we apply this methodology to glaciers of the canadian high arctic the velocity field is the main error source for small and medium size glaciers discharge 100 mt a 1 with high velocities 100 m a 1 the error in crosssectional area dominates thinning thickening between ice thickness and velocity measurements should be considered as it implies systematic errors up to 8 in our study the u shaped parabolic approach which allows for an adjusted estimation when the ice thickness measurement point is displaced from the glacier centreline performs best with small bias and admissible standard error we observe an increase of ice discharge from the main glaciers trinity and wykeham of the prince of wales icefield from 2015 to 2016 by 5 and 20 respectively followed by a decrease in 2017 by 10 and 15 respectively belcher glacier of the devon ice cap maintains similar discharges during 2015 17

rock magnetic techniques complemented by ferromagnetic resonance spectroscopy to analyse a sediment record summary environmental magnetism uses the spatial and temporal occurrence of magnetic carriers as diagnostic tools to detect environmental changes concentration composition grain size and configuration of the carriers inferred from magnetic properties are key parameters because they are indicative of the formation conditions of magnetic phases and or of processes such as diagenesis and weathering we present a detailed ferromagnetic resonance fmr spectroscopy analysis in concert with routinely used rock magnetic measurements to determine these parameters in a sediment record that documents the development of lake soppensee central switzerland since latest pleistocene fmr spectroscopy monitors varying concentration of the predominant magnetite maghemite by the spectral signal intensity whereas the stable single domain and superparamagnetic states are determined by the signal shape at room and low temperature fitting and simulation of fmr spectra are successfully applied to samples with well defined magnetite components in the sediment matrix clear evidence for the colonization of magnetotactic bacteria mtb in lake soppensee was possible by applying empirical spectral separation to measured fmr signals that yield two magnetite populations differing in their configuration that is dispersed and aligned in chains low temperature measurements showed that these mtb can be preserved as pure or oxidized magnetite the fmr data set confirms and completes rock magnetic information obtained from the lacustrine sedimentary record the advanced application of fmr spectroscopy in the presented study critically highlights the benefit of this rapid and non destructive method for future analysis of magnetic properties in environmental studies

laacher see tephra a widespread isochronous late quaternary tephra layer in central and northern europe a late quaternary tephra layer widespread in central and northern europe resulted from explosive plinian and phreatomagmatic eruptions of the laacher see volcano 11 000 yr b p the tephra is distinguished from other late quaternary andesitic rhyolitic airfall tuff layers in northern europe and from basaltic or trachytic tuff deposits in southern europe by its phonolitic composition and abundance of sanidine plagioclase clinopyroxene amphibole and sphene the proximal tephia sequence at laacher see is divided into three main deposits the predominantly plinian deposits of lower and middle laacher see tephra llst and mlst and phreatomagmatic deposits of the upper laacher see tephra ulst the mlst member is further subdivided into beds a b and c1 c2 and c3 the chemical composition of the magma is highly differentiated phonolite in the llst to mlst b sections but mafic phonolite in the mlst c1 to ulst sections all deposits are considered to be isochronous the frequency maximum of 16 radiocarbon datings indicating an eruption about 11 000 50 yr b p distal ash was deposited in three main fans directed to the northeast lst traced up to 1 100 km distance south lst traced up to 600 km and southwest lst traced up to 100 km tephrostratigraphic correlation of the distal ash deposits is based on a the major element composition of glass shards b lithology and c heavy mineral analyses the northeastern fan consists of deposits from llst mlst b and mlst c1 eruptive phases the southern fan comprises mlst a mlst c2 and ulst deposits and the southwestern fan consists exclusively of ash from the ulst eruptive phase northeastern transport of ash during eruptive phases with high plinian eruption columns but southern and southwestern transport of ash along phases of relatively low eruption columns are interpreted in terms of prevailing southwesterly paleowinds at high altitudes tropopause level but northerly winds dominating in the lower atmosphere the laacher see eruption columns were emplaced into an atmosphere vertically zoned with respect to paleowind directions which also explains the near vent shifting of llst mlst b and mlst c1 iso pach axes from east southeast to northeast within the first 20 km of transport

direct comparison of uk temperatures and greenland snow accumulation rates 15000 12000 yr ago a palaeotemperature record based on fossil coleopteran evidence and dated by accelerator mass spectroscopy ams 14c determinations on plant macrofossils has been obtained for the last glacial interglacial transition from the site of gransmoor in eastern england calibration of the radiocarbon measurements enabled a direct comparison to be made between this palaeotemperature curve and the snow accumulation record from the gisp 2 greenland ice core the similarity between the two data sets suggests a degree of correspondence in the pattern and timing of climatic change in greenland and the british isles at the end of the last cold stage

oxygen isotope wiggle matching as a tool for synchronising ice core and terrestrial records over termination 1 abstract in nw europe the large number of terrestrial records that are now available from termination 1 15 10 kcal yr bp form the basis for a highly detailed picture of lateglacial environmental change nevertheless the greenland oxygen isotope records grip gisp2 are still regarded as the best high resolution climate proxy for the north atlantic region in order to evaluate spatial contrasts and leads and lags in the climate system integration of ice core marine and terrestrial records is becoming increasingly important intimate objectives however comparisons between different environments require a common time scale for the proxy climate records stable isotope analyses performed on lateglacial lacustrine calcareous deposits in the netherlands provide a terrestrial oxygen isotope record comparable to that from the greenland ice core these atmospherically controlled lacustrine oxygen isotope signals not only constitute an independent palaeoclimatic proxy but provide the basis for synchronising records from these environments as well more over this synchronisation reveals some remarkable aspects concerning the timing of the oxygen isotope and palynological events as recorded in the netherlands above all oxygen isotope wiggle matching offers a means of correlating terrestrial and ice core records

sharply increased mass loss from glaciers and ice caps in the canadian arctic archipelago the canadian arctic archipelago contains one third of the global volume of land ice outside the ice sheets but its contribution to sea level change is largely unknown gardner et al use three independent techniques to reveal that mass loss from the archipelago was 92 12 gigatonnes per year in 2007 09 about three times greater than in 2004 06 and coincident with warmer summer temperatures the record is too short to allow a firm conclusion on longer term trends but it is clear that the canadian arctic archipelago is a significant contributor to sea level rise mountain glaciers and ice caps are contributing significantly to present rates of sea level rise and will continue to do so over the next century and beyond1 2 3 4 5 the canadian arctic archipelago located off the northwestern shore of greenland contains one third of the global volume of land ice outside the ice sheets6 but its contribution to sea level change remains largely unknown here we show that the canadian arctic archipelago has recently lost 61 7 gigatonnes per year gt yr 1 of ice contributing 0 17 0 02 mm yr 1 to sea level rise our estimates are of regional mass changes for the ice caps and glaciers of the canadian arctic archipelago referring to the years 2004 to 2009 and are based on three independent approaches surface mass budget modelling plus an estimate of ice discharge smb d repeat satellite laser altimetry icesat and repeat satellite gravimetry grace all three approaches show consistent and large mass loss estimates between the periods 2004 2006 and 2007 2009 the rate of mass loss sharply increased from 31 8 gt yr 1 to 92 12 gt yr 1 in direct response to warmer summer temperatures to which rates of ice loss are highly sensitive 64 14 gt yr 1 per 1 k increase the duration of the study is too short to establish a long term trend but for 2007 2009 the increase in the rate of mass loss makes the canadian arctic archipelago the single largest contributor to eustatic sea level rise outside greenland and antarctica

a method to estimate the ice volume and ice thickness distribution of alpine glaciers sound knowledge of the ice volume and ice thickness distribution of a glacier is essential for many glaciological applications however direct measurements of ice thickness are laborious not feasible everywhere and necessarily restricted to a small number of glaciers in this paper we present a method to estimate the ice thickness distribution and the total ice volume of alpine glaciers this method is based on glacier mass turnover and principles of ice flow mechanics the required input data are the glacier surface topography the glacier outline and a set of borders delineating different ice flow catchments three parameters describe the distribution of the apparent mass balance which is defined as the difference between the glacier surface mass balance and the rate of ice thickness change and two parameters define the ice flow dynamics the method was developed and validated on four alpine glaciers located in switzerland for which the bedrock topography is partially known from radio echo soundings the ice thickness along 82 cross profiles can be reproduced with an average deviation of about 25 between the calculated and the measured ice thickness the cross sectional areas differ by less than 20 on average this shows the potential of the method for estimating the ice thickness distribution of alpine glaciers without the use of direct measurements

form and flow of the academy of sciences ice cap severnaya zemlya russian high arctic 1 the 5 575 km2 academy of sciences ice cap is the largest in the russian arctic a 100 mhz airborne radar digital landsat imagery and satellite synthetic aperture radar sar interferometry are used to investigate its form and flow including the proportion of mass lost through iceberg calving the ice cap was covered by a 10 km spaced grid of radar flight paths and the central portion was covered by a grid at 5 km intervals a total of 1 657 km of radar data digital elevation models dems of ice surface elevation ice thickness and bed elevation data sets were produced cell size 500 m the dems were used in the selection of a deep ice core drill site total ice cap volume is 2 184 km3 5 5 mm sea level equivalent the ice cap has a single dome reaching 749 m maximum ice thickness is 819 m about 200 km or 42 of the ice margin is marine about 50 of the ice cap bed is below sea level the central divide of the ice cap and several major drainage basins in the south and east of the ice cap and of up to 975 km2 are delimited from satellite imagery there is no evidence of past surge activity on the ice cap sar interferometric fringes and phase unwrapped velocities for the whole ice cap indicate slow flow in the interior and much of the margin punctuated by four fast flowing features with lateral shear zones and maximum velocity of 140 m yr 1 these ice streams extend back into the slower moving ice to within 5 10 km of the ice cap crest they have lengths of 17 37 km and widths of 4 8 km mass flux from these ice streams is 0 54 km3 yr 1 tabular icebergs up to 1 7 km long are produced total iceberg flux from the ice cap is 0 65 km3 yr 1 and probably represents 40 of the overall mass loss with the remainder coming from surface melting driving stresses are generally lowest 40 kpa close to the ice cap divides and in several of the ice streams ice stream motion is likely to include a significant basal component and may involve deformable marine sediments

the randolph glacier inventory a globally complete inventory of glaciers the randolph glacier inventory rgi is a globally complete collection of digital outlines of glaciers excluding the ice sheets developed to meet the needs of the fifth assessment of the intergovernmental panel on climate change for estimates of past and future mass balance the rgi was created with limited resources in a short period priority was given to completeness of coverage but a limited uniform set of attributes is attached to each of the 198 000 glaciers in its latest version 3 2 satellite imagery from 1999 2010 provided most of the outlines their total extent is estimated as 726 800 34 000 km 2 the uncertainty about 5 is derived from careful single glacier and basin scale uncertainty estimates and comparisons with inventories that were not sources for the rgi the main contributors to uncertainty are probably misinterpretation of seasonal snow cover and debris cover these errors appear not to be normally distributed and quantifying them reliably is an unsolved problem combined with digital elevation models the rgi glacier outlines yield hypsometries that can be com bined with atmospheric data or model outputs for analysis of the impacts of climatic change on glaciers the rgi has already proved its value in the generation of significantly improved aggregate estimates of glacier mass changes and total volume and thus actual and potential contributions to sea level rise

testing the fidelity of sediment chronology comparison of varve and paleomagnetic results from holocene lake sediments from central finland abstract a careful construction of independent varve and paleomagnetic chronologies from three varved lake sediment records from central finland resulted in detailed and continuous age depth profiles cumulative varve calculation errors were estimated to be 3 for lake alimmainen savijarvi 10 295 340 varve years and 1 for lakes nautajarvi 9898 97 varve years and korttajarvi 9590 103 varve years paleomagnetic secular variation psv curves demonstrate good consistency between these sites and within a margin of varve chronology error they show similar declination and inclination features commonly described in the uk and sweden the timing of psv patterns from finnish varved sites agree well with uk curves between the present and 2000 bc and in pre 6000 bc deposits and with swedish data between the present and 5000 bc combined inclination records from three independently dated finnish varved sites possess an opportunity for accurate paleomagnetic comparisons within the margin of varve chronology errors and throughout the last 10 000 years

antiphasing between rainfall in africa s rift valley and north america s great basin the beginning of the bolling allerod warm period was marked in greenland ice by an abrupt rise in 18o an abrupt drop in dust rain and an abrupt increase in atmospheric methane content the surface waters in the norwegian sea underwent a simultaneous abrupt warming at about this time a major change in the pattern of global rainfall occurred lake victoria latitude 0 which prior to this time was dry was rejuvenated the red sea which prior to this time was hypersaline freshened lake lahontan which prior to this time had achieved its largest size desiccated whereas the chronologic support for the abruptness of the hydrologic changes is firm only for the red sea in keeping with evidence obtained well away from the northern atlantic in the santa barbara basin and the cariaco trench the onset and end of the millennial duration climate events were globally abrupt if so the proposed linkage between the size of african closed basin lakes and insolation cycles must be reexamined

mass balance of the greenland ice sheet from 1958 to 2007 we combine estimates of the surface mass balance smb of the greenland ice sheet for years 1958 to 2007 with measurements of the temporal variability in ice discharge d to deduce the total ice sheet mass balance during that time period we find a robust correlation r2 0 83 between anomalies in smb and in d which we use to reconstruct a continuous series of total ice sheet mass balance we find that the ice sheet was losing 110 70 gt yr in the 1960s 30 50 gt yr or near balance in the 1970s 1980s and 97 47 gt yr in 1996 increasing rapidly to 267 38 gt yr in 2007 multi year variations in ice discharge themselves related to variations in smb cause 60 20 more variation in total mass balance smb and therefore dominate the ice sheet mass budget copyright 2008 by the american geophysical union

data model comparison of the younger dryas event the younger dryas cooling event is well established in the north atlantic region through numerous climate proxy records although the climatological controls vary from site to site it is considered to have taken place between about 10 000 and 11 000 bp radiocarbon years 11 500 13 000 calendar years ago outside the north atlantic region climate proxy records and chronology commonly become problematic because of weaker signals and less dating control in addition to this evidence oceanic records reveal conflicting evidence for younger dryas forcing mechanisms and the timing of events we compare proxy evidence with the results from an ocean general circulation model coupled to the energy moisture balance atmospheric model the model results reveal a global pattern and regional magnitude which generally agree with temperature changes interpreted from paleoclimate reconstructions the model also supports the general duration of global cooling of the younger dryas although proxy data can be controversial outside of the north atlantic region the authors believe that there is enough evidence to support the younger dryas event on a global scale they also recognize however that more concrete evidence is needed before the question can be unequivocally answered

glacial interglacial variability of particle accumulation in the canary basin a time slice approach abstract particle supply and sediment accumulation in the canary basin are strongly modified by seasonal coastal upwelling and dust input from the sahara along an e w depth profile and fertility gradient north of the canary islands we demonstrate an increase in total mass accumulation rates from a low of 1 2 g cm 2 ka 1 in the outer oceanic domain to 6 12 g cm 2 ka 1 closer to the moroccan shelf in holocene sediments during the last glacial maximum lgm oxygen isotopic event 2 2 a steeper gradient was found with two to four times higher mass accumulation rates at the near shore sites total mass accumulation rates during the last interglacial climax lic isotopic event 5 5 and end of the penultimate glaciation epg isotopic event 6 2 resemble holocene values with lowered near shore maxima of 3 and 4 g cm 2 ka 1 respectively analyses of separate sediment components show that total organic carbon total carbonate lithogenic and diatom accumulation rates were generally enhanced during glacial times especially during the lgm in contrast glacial accumulation rates of biogenic carbonate particles coccoliths and planktic foraminifera shells remained constant or were lowered with respect to interglacial time periods at the site closest to the moroccan shelf despite a doubling of bulk carbonate accumulation this could indicate lowered supply from the productive euphotic zone or a latitudinal offshore shift of the main sedimentary depocentre however enhanced carbonate dissolution could by itself account for this decrease in biogenic carbonate accumulation increased glacial input of detrital carbonate derived from the exposed moroccan shelf appears to be responsible for the overall enhanced carbonate accumulation at the same sites east of lanzarote

surface velocity and ice discharge of the ice cap on king george island antarctica glaciers on king george island antarctica have shown retreat and surface lowering in recent decades concurrent with increasing air temperatures a large portion of the glacier perimeter is ocean terminating suggesting possible large mass losses due to calving and submarine melting here we estimate the ice discharge into the ocean for the king george island ice cap l band synthetic aperture radar images covering the time span january 2008 to january 2011 over king george island are processed using an intensity tracking algorithm to obtain surface velocity measurements pixel offsets from 40 pairs of radar images are analysed and inverted to estimate a weighted average surface velocity field ice thicknesses are derived from simple principles of ice flow mechanics using the computed surface velocity fields and in situ thickness data the maximum ice surface speeds reach 225 m a 1 and the total ice discharge for the analysed flux gates of king george island is estimated to be 0 720 0 428 gt a 1 corresponding to a specific mass loss of 0 64 0 38 m w e a 1 over the area of the entire ice cap 1127 km 2

iceberg calving rates from northern ellesmere island ice caps canadian arctic 1999 2003 optical satellite imagery was used to estimate glacier surface velocities and iceberg calving rates from agassiz and western grant ice caps nunavut canada between 1999 and 2003 the largest mean annual surface velocities ranged from 400 to 700 m a 1 but velocities in the 100 200 m a 1 range were common summer velocities were up to an order of magnitude larger than annually averaged velocities the highest velocity 1530 m a 1 was measured on the floating tongue of lake tuborg glacier between 19 july and 19 august 2001 calving rates from individual glaciers varied by up to a factor of two between successive years summer calving rates were 2 8 times larger than annual average rates the average ratio of the calving flux due to terminus volume change to that due to ice flow through the glacier terminus was 0 81 for the annual rates and 1 71 for summer rates the estimated mean annual calving rate from agassiz ice cap in the period 1999 2002 was 0 67 0 15 km 3 a 1 o f which 54 emanated from eugenie glacier alone this total rate is similar to a previously estimated calving rate from devon ice cap

continental biogenic species in the greenland ice core project ice core tracing back the biomass history of the north american continent ammonium nitrate and organic acid records from the greenland ice core project deep ice core are discussed all species have a continental biogenic source that is situated predominantly on the north american continent for species deposited in summit central greenland the record therefore can be used to trace back the biomass history of the north american continent difficulty in the interpretation of these records arises from their unknown transfer behavior in a more alkaline atmosphere which characterizes glacial time periods compared to interglacial stadials this may have implications not only for weak acids such as formate and acetate but also possibly for the transport and incorporation of hno3 into aerosols whereas ammonium is probably not affected by the alkalinity change of the atmosphere our approach is to compare samples with similar h concentrations throughout the record from the records we infer several significant fluctuations in the extent of the laurentide ice sheet during the last glaciation we find evidence against the occurrence of an extensive younger dryas event in north america