mineralogy and geochemistry of alluvium contaminated by metal mining in the rio tinto area southwest spain the rio tinto in sw spain drains cu and pyrite mines which have been in operation since at least the bronze age extensive metal mining especially from 1873 to 1954 has resulted in contamination of the rio tinto alluvium with as cu pb ag and zn x ray diffraction xrd wavelength dispersive x ray mapping scanning electron microscope petrography and x ray energy dispersive edx analysis has revealed that 4 major groups of contaminant metal and as bearing minerals including sulphides fe as oxides fe oxides hydroxides oxyhydroxides and fe oxyhydroxysulphates occur in the alluvium sulphide minerals including pyrite chalcopyrite arsenopyrite and sphalerite occur in alluvium near the mining areas iron hydroxides and oxyhydroxides such as goethite and possibly ferrihydrite occur in cements in both the mining areas and alluvium downstream and carry minor amounts of as cu and zn iron oxyhydroxysulphates including jarosite plumbojarosite and possibly schwertmannite are the most common minerals in alluvium downstream of the mining areas and are major hosts of cu pb zn and of as next to the fe as minerals this work and other field observations suggest that 1 the extreme acidity and elevated metal concentrations of the river water will probably be maintained for some time due to oxidation of pyrite and other sulphides in the alluvium and mine waste tips and from formation of secondary oxide and oxyhydroxysulphates 2 soluble fe oxyhydroxysulphates such as copiapite which form on the alluvium are a temporary store of contaminant metals but are dissolved during periods of high rainfall or flooding releasing contaminants to the aqueous system 3 relatively insoluble fe oxyhydroxysulphates and hydroxides such as jarosite and goethite may be the major long term store of alluvial contaminant metals and 4 raising river ph will probably cause precipitation of fe oxyhydroxides and oxides hydroxides oxyhydroxides and thus have a positive effect on water quality but this action may destabilise some of these contaminant metal bearing minerals releasing metals back to the aqueous system

maximum late holocene extent of the western greenland ice sheet during the late 20th century 10 be exposure dating abstract the pattern of greenland ice sheet margin change during the 20th century is variable large scale retreat of marine outlet glaciers contrasts with the often negligible retreat observed along land terminating margins of the ice sheet we reconstruct a chronology of ice margin change for two land terminating ice margins in western greenland using radiocarbon and 10 be exposure dating our results indicate that two land terminating lobes attained their maximum late holocene position in the late 20th century this contrasts with the nearby marine terminating jakobshavn isbrae which achieved a maximum late holocene position during the little ice age and has since retreated ca 40 km in addition we survey ice margin change across western greenland utilizing satellite imagery we find that many land terminating sectors of the ice sheet in addition to our study area may have attained their maximum late holocene extent during the 20th century this suggests a lagged ice margin response to prior cooling such as the little ice age which would imply significant retreat of land terminating sections of the greenland ice sheet in response to 20th and 21st century warming may be yet to come

controls upon the last glacial maximum deglaciation of the northern uummannaq ice stream system west greenland the uummannaq ice stream system uiss was a convergent cross shelf ice stream system that operated in west greenland during the last glacial maximum lgm this paper presents new evidence constraining the geometry and evolution of the northern sector of the uiss and considers the factors controlling its dynamic behaviour geomorphological mapping 21 new terrestrial cosmogenic nuclide tcn exposure ages and radiocarbon dating constrain lgm warm based ice stream activity in the north of the system up to 1400 m a s l intervening plateaux areas either remained ice free or were covered by cold based icefields beyond the inner fjords topography and bathymetry forced ice flow southwards into the uummannaq trough where it coalesced with ice from the south and formed the trunk zone of the uiss deglaciation of the uiss began at 14 9 cal ka bp rapid retreat from the lgm limit was forced by an increase in air temperatures and rising sea level enhanced by the bathymetric over deepening of the uummannaq and igdlorssuit sund troughs ice reached the inner fjord confines in the northern uummannaq area by 11 6 ka and experienced an ice marginal stabilisation in rink karrat fjord for up to 5 ka this was a function of topographic constriction and bathymetric shallowing and occurred despite continued climatic forcing in the neighbouring ingia fjord this did not occur following this period of stability ice within rink karrat fjord retreated reaching the present ice margin or beyond after 5 ka the presence of a major ice stream within a mid fjord setting during the mid holocene and the holocene thermal maximum 11 5 ka is in direct contrast to records of other ice streams throughout west greenland which suggest ice had retreated beyond its present margin by 9 7 ka this demonstrates the potential importance of topographic control on calving margin stability and its ability to override climatic forcing

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

mineralogical and geochemical characterisation of open air tailing and waste rock dumps from the libiola fe cu sulphide mine eastern liguria italy active acid mine drainage amd processes at the libiola fe cu sulphides mine are mainly triggered by water rock interaction occurring within open air tailing and waste rock dumps these processes are mainly controlled by exposure to weathering agents the grain size of the dumped materials and by the quantity of sulphides the sulphide types and their mode of occurrence due to these factors several paragenetic stages of evolution have been recognised at different depths at different sites and within the same site the dump samples were investigated with mineralogical reflected and transmitted light optical microscopy xrpd and sem eds and geochemical icp aes leco techniques the amd evaluation of the tailing and waste rock samples was performed by calculating the maximum potential acidity the acid neutralising capacity and the net acid producing potential the results allowed us to demonstrate that the open air tailings had already superseded their amd apex and are now practically inert material composed mainly of stable goethite lepidocrocite hematite assemblages on the contrary the sulphide rich waste rocks still have a strong potential to produce long term amd causing the acidification of circulating waters and the release of several hazardous elements

isolation basins sea level changes and the holocene history of the greenland ice sheet abstract isolation basins are natural topographic depressions that at various times in their history may be connected to or isolated from the sea by changes in relative sea level rsl they provide a valuable source of data for tracking large scale tens of meters changes in rsl over millennia as well as quiet water depositional environments where abrupt changes caused by tsunami iceberg roll or storms may be recorded in this paper we review isolation basins as sources of rsl data with a particular focus on their use in greenland to constrain the holocene history of the ice sheet a new rsl curve from disko fjord west greenland is presented which shows that local ice free conditions were established at c 11 k cal yr bp after which rsl fell rapidly from a marine limit at c 80 m to reach close to present sea level by c 4 k cal yr bp we compare this record with other isolation basin rsl data from six other sites in disko bugt and note a strong northwest southeast differential rebound across the area during the early and mid holocene that reflects variations in ice load history we compare the disko bugt data with other previously published isolation basin rsl records from sisimiut central west greenland nanortalik south greenland and ammassalik southeast greenland rsl fell below present during the early holocene at nanortalik c 10 k cal yr bp and during the mid to late holocene elsewhere before rising to present these differences reflect variations in the timing and amount of greenland ice load change since the last glacial maximum as well as non greenland processes notably the collapse of the laurentide forebulge and also changes in ice equivalent sea level isolation basin data have relatively small age and height uncertainties compared with other rsl indicators enabling them to resolve between different earth and ice sheet models especially during periods of large ice load and rsl change

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

rapid submarine melting of the calving faces of west greenland glaciers widespread glacier acceleration has been observed in greenland in the past few years oceanographic observations taken in summer 2008 show that ocean waters melted a substantial fraction of ice along the calving fronts of three west greenland glaciers indicating that submarine melting has a profound influence on grounding line stability widespread glacier acceleration has been observed in greenland in the past few years1 2 3 4 associated with the thinning of the lower reaches of the glaciers as they terminate in the ocean5 6 7 these glaciers thin both at the surface from warm air temperatures and along their submerged faces in contact with warm ocean waters8 little is known about the rates of submarine melting9 10 11 and how they may affect glacier dynamics here we present measurements of ocean currents temperature and salinity near the calving fronts of the eqip sermia kangilerngata sermia sermeq kujatdleq and sermeq avangnardleq glaciers in central west greenland as well as ice front bathymetry and geographical positions we calculate water mass and heat budgets that reveal summer submarine melt rates ranging from 0 7 0 2 to 3 9 0 8 m d 1 these rates of submarine melting are two orders of magnitude larger than surface melt rates but comparable to rates of iceberg discharge we conclude that ocean waters melt a considerable but highly variable fraction of the calving fronts of glaciers before they disintegrate into icebergs and suggest that submarine melting must have a profound influence on grounding line stability and ice flow dynamics

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

asynchronous instability of the north american arctic and greenland ice sheets during the last deglaciation abstract the chronology of deglacial meltwater pulses from the laurentide ice sheet is well documented however the deglacial history of the north american arctic north eastern laurentide and innuitian and western greenland ice sheets draining into the labrador sea via baffin bay is less well constrained here we present new high resolution radiocarbon dated records from the central baffin bay spanning 17 to 10 kyr bp and documenting the full deglacial history of baffin bay sedimentological and geochemical data confirm the presence of two periods of enhanced detrital carbonate delivery termed baffin bay detrital carbonate events bbdcs these events are dated to 14 2 13 7 kyr bp and 12 7 11 kyr bp they are synchronous across baffin bay and their mineralogical signature indicates a common source of detrital carbonate from northern baffin bay the first event bbdc 1 postdates heinrich event 1 and the second event bbdc 0 predates the recently revised timing of heinrich event 0 the onset of the bbdc events appears not to be systematically linked to greenland temperature change as they occur during both interstadial and stadial periods this indicates that deglaciation of north american arctic and western greenland ice sheets with the associated iceberg and meltwater discharge were decoupled from the dominant north atlantic climate mode where iceberg discharge events from the laurentide ice sheet occurred during stadial periods

rapid response of helheim glacier southeast greenland to early holocene climate warming recent changes in speed thinning and retreat rates of marine terminating outlet glaciers have raised concerns about the future stability of the greenland ice sheet establishing a longer term record of outlet glacier retreat rates is essential to provide a context for present day observations and to improve and constrain numerical models of outlet glacier behavior new exposure dating 10be of streamlined bedrock surfaces and glacial erratic boulders of sermilik fjord southeast greenland the present day drainage route of helheim glacier documents rapid retreat 80 m a 1 of this major marine terminating outlet glacier at the close of the last glaciation the glacier front retreated 80 km to within 20 km of the present day 2010 position of helheim glacier in 1 ka ca 10 8 0 3 ka ago retreat followed rapidly rising air temperatures at the start of the holocene and at this temporal resolution there is no evidence that fjord geometry influenced glacier behavior the significant response to climatic amelioration at the end of the last glacial suggests a high sensitivity to abrupt temperature increases which has major implications for the future stability of present day greenlandic outlet glaciers in a warming climate

a revised chronology for the fjord stade moraine in disko bugt west greenland this paper re evaluates the age of the fjord stade moraine in disko bugt a large marine embayment in west greenland previous work suggests that this moraine is part of a widespread moraine complex present throughout west greenland which formed ca 9300 cal yr bp in response to either a regional climate change or the effects of topographic controls on ice sheet recession we present the results of a relative sea level study using data from eight isolation basins that straddle the fjord stade moraine in southeast disko bugt our results suggest that the moraine here formed between ca 8400 and 7700 cal yr bp this is later than previously thought and similar in timing to a widespread cooling event recorded in the greenland ice core records this chronological similarity raises the possibility that the fjord stade moraine in the study area records an ice marginal response to a major short lived climatic cooling during the early holocene the so called 8200 event

sensitivity of 21st century sea level to ocean induced thinning of pine island glacier antarctica 1 pine island glacier pig antarctica is rapidly losing mass supporting arguments that it may play a major role in 21st century sea level rise yet this glacier s quantitative contribution to sea level based on theoretical and computational models is poorly known we have developed a basin scale glaciological model to examine the sensitivity of pig to a range of environmental forcings while oceanic melt likely played the leading role in recent thinning and retreat we find that the particular grounding line geometry with an extended ice plain in the 1990s made it susceptible to such forcing our model further indicates that while the rate of grounding line retreat should diminish soon the glacier s mass loss may continue at rates similar to or moderately elevated from the present while substantial our model derived maximum rate of 2 7 cm century is considerably smaller than previous heuristically derived bounds on the sea level contribution

unstable ice stream in greenland during the younger dryas cold event past present and future ice sheet stability is closely linked to the dynamic behavior of major draining ice streams and surrounding ice shelves while short observational records document the recent variability and acceleration of ice streams the long term dynamics of ice streams remain poorly documented here we date the pjetursson s moraine on disko island greenland to 12 2 0 6 ka and demonstrate that the jakobshavn isbrae ji ice stream collapsed during the middle of the younger dryas yd cold interval we suggest that this collapse was due to the incursion of warm subsurface water under the ice shelf fronting the ji ice stream as well as increased surface air temperature and sea surface temperature seasonality starting at the beginning of the yd cold interval the triggered acceleration of the land based ji and the delivery of icebergs into disko bugt potentially contributed to heinrich event 0 at the end of the yd the collapse of the ji ice stream 12 2 0 6 ka ago demonstrates that calving marine based ice margins can respond rapidly to environmental changes it provides a new benchmark for marine terminating ice stream models

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

new constraints on greenland ice sheet dynamics during the last glacial cycle evidence from the uummannaq ice stream system this paper presents the first assessment of the uummannaq ice stream system uiss in west greenland the uiss drained 6 of the greenland ice sheet gris at the last glacial maximum lgm the onset of the uiss is a function of a convergent network of fjords which feed a geologically controlled trough system running offshore to the shelf break mapping cosmogenic radiogenic nuclide crn dating and model output reveal that glacially scoured surfaces up to 1266 m above sea level asl in fjord head areas were produced by warm based ice moving offshore during the lgm with the elevation of warm based ice dropping westwards to 700 m asl as the ice stream trunk zone developed marginal plateaux with allochthonous blockfields suggest that warm based ice produced till and erratics up to 1200 m asl but crn ages and weathering pits suggest this was pre lgm with only cold based ice operating during the lgm deglaciation began on the outer shelf at 14 8 cal kyrs b p with ubekendt ejland becoming ice free at 12 4 ka the uiss then collapsed with over 100 km of retreat by 11 4 ka 10 8 cal kyrs b p a rapid and complex response to bathymetric deepening trough widening and sea level rise coinciding with rapidly increasing air temperatures and solar radiation but which occurred prior to ocean warming at 8 4 cal kyrs b p local fjord constriction temporarily stabilized the unzipped uiss margins at the start of the holocene before ice retreat inland of the current margin at 8 7 ka

imprints of hydrocarbon bearing basinal fluids on a karst system mineralogical and fluid inclusion studies from the buda hills hungary calcite veins and related sulphate sulphide mineralisation are common in the buda hills also abundant hypogenic caves are found along fractures filled with these minerals pointing to the fact that young cave forming fluids migrated along the same fractures as the older mineralising fluids did the studied vein filling paragenesis consists of calcite barite fluorite and sulphides the strike of fractures is consistent nnw sse concluding a latest early miocene maximum age for the formation of fracture filling minerals calcite crystals contain coeval primary hydrocarbon bearing and aqueous inclusions indicating that also hydrocarbons have migrated together with the mineralising fluids hydrocarbon inclusions are described here for the first time from the buda hills mixed inclusions i e petroleum with water tail were also detected indicating that transcrystalline water migration took place the coexistence of aqueous and petroleum inclusions permitted to establish the entrapment temperature 80 c and pressure 85 bar of the fluid and thus also the thickness of sediments having been eroded since latest early miocene times was calculated 800 m low salinity of the fluids 1 7 nacl eq wt implies that hydrocarbon bearing fluids were diluted by regional karst water ft ir investigations revealed that co2 and ch4 are associated with hydrocarbons groundwater also contains small amounts of hc and related gases on the basin side even today based on the location of the paleo and recent hydrocarbon indications identical migration pathways were reconstructed for both systems hydrocarbon bearing fluids are supposed to have migrated north westward from the basin east to the buda hills from the miocene on

mineralogical and geochemical investigations of pyrite rich mine waste from a kyanite mine in central virginia with comments on recycling a pyrite rich waste stream is one of three types generated from a kyanite mine in central virginia near the town of dillwyn buckingham county currently ore consists of approximately 3 pyrite waste and an estimated 382 000 tons of this waste stream has been generated over the past 60 years the mineralogy of the waste stream consists of variable amounts of pyrite 70 99 talc 1 20 quartz 1 10 kyanite 0 5 5 with minor or trace amounts of magnetite hematite galena anorthite and rare earth phosphate energy dispersive spectroscopy analysis indicates that talc has minor amounts of al up to 1 57 wt and fe up to 4 29 wt and pyrite grains have no impurities above detection limit of approximately 0 1 wt bulk chemical analysis of selected elements using inductively coupled plasma mass spectrometry analysis indicate that zn 28 82 367 71 ppm as 8 94 18 26 ppm se 44 62 64 50 ppm cd 0 19 1 03 ppm hg 0 87 35 91 ppm and pb 65 10 189 66 ppm occur at levels of some environmental concern au and ag concentrations are negligible currently the waste stream is well managed and sold but for a low price talc is of sufficient quality to be of interest for recycling but the estimated 540 tons generated per year is not a suitable quantity to be economically viable currently the waste stream is not viable for recycling for higher monetary value however the characteristics of the pyrite may enable such recycling in the future for solar energy technologies this and other associated waste streams show long term promise for integrated recycling and may play important economic roles in an economically disadvantaged region

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

holocene thinning of the greenland ice sheet the nature of the response of the greenland ice sheet gis to climate change is a fundamental question in climate science but the details remain unclear during the holocene climate optimum 6 000 to 9 000 years ago for example many locations in the northern hemisphere showed unusual warmth yet changes in greenland appeared inconsistent vinther et al now standardize the previously disparate seeming ice core records of climate history on the gis during the holocene and find consistent evidence for a stronger climate optimum than was previously recognized together with elevation reduction and marginal ice sheet thinning the response of the greenland ice sheet gis to changes in climate remains uncertain during the holocene climatic optimum an unusually warm period from about 9 000 to 6 000 years ago changes in greenland appear inconsistent with the rest of the northern hemisphere here the greenland holocene temperature history and the evolution of gis surface elevation are extracted from four gis locations the results may resolve this disparity on entering an era of global warming the stability of the greenland ice sheet gis is an important concern1 especially in the light of new evidence of rapidly changing flow and melt conditions at the gis margins2 studying the response of the gis to past climatic change may help to advance our understanding of gis dynamics the previous interpretation of evidence from stable isotopes 18o in water from gis ice cores was that holocene climate variability on the gis differed spatially3 and that a consistent holocene climate optimum the unusually warm period from about 9 000 to 6 000 years ago found in many northern latitude palaeoclimate records4 did not exist here we extract both the greenland holocene temperature history and the evolution of gis surface elevation at four gis locations we achieve this by comparing 18o from gis ice cores3 5 with 18o from ice cores from small marginal icecaps contrary to the earlier interpretation of 18o evidence from ice cores3 6 our new temperature history reveals a pronounced holocene climatic optimum in greenland coinciding with maximum thinning near the gis margins our 18o based results are corroborated by the air content of ice cores a proxy for surface elevation7 state of the art ice sheet models are generally found to be underestimating the extent and changes in gis elevation and area our findings may help to improve the ability of models to reproduce the gis response to holocene climate

rapid ice retreat in disko bugt supported by 10be dating of the last recession of the western greenland ice sheet 10 be dating abstract due to rising sea levels and warming ocean currents marine based sectors of the greenland and ant arctic ice sheets are particularly vulnerable to warming climate reconstructions of the timing of marine based ice margin fluctuations in greenland during the early holocene can provide context for historical and modern observations of ice sheet change here we generate a 10 be chronology of ice sheet retreat through disko bugt western greenland our new chronology consisting of twelve 10 be ages from sites surrounding and within disko bugt fills a gap in the history of the western margin of the greenland ice sheet and allows for a continuous composite record of ice margin recession between the continental shelf break and the current margin we constrain the onset of ice margin retreat from outer disko bugt to 10 8 0 5 ka when combined with previous chronologies these results place the final greenland ice sheet retreat out of disko bugt onto land at jakobshavn isfjord and qasigiaanguit at 10 1 0 3 ka and later at 9 2 0 1 ka in southeastern disko bugt the rate of retreat during this time period is between w50e450 m a 1 for central disko bugt and w50e70 m a 1 along the southern coast of disko bugt

contrasting evidence of holocene ice margin retreat south western greenland constraining the greenland ice sheet s gris response to holocene climate change provides calibrations for ice sheet models that hindcast past ice margin fluctuations ice sheet models predict enhanced ice retreat in south western greenland during the middle holocene however few geological observations corroborating the extensive retreat are available we present new data from lake sediment cores from the isua region south western greenland which provide constraints on holocene fluctuations of the gris margins our data indicate that the main gris margin was 30 km west of its present day extent by 5 7k cal a bp and had retreated to within 3 km of its present day margin by 4 6k cal a bp with subsequent re advances by 1 8 and at 1 7 1 3 and 0 5k cal a bp times of ice retreat are coeval with increasing temperatures in western greenland suggesting that temperature was a dominant factor in ice retreat the late retreat at isua is in contrast to the early retreat observed in the godthabsfjord area and is probably related to the lack of fjords extending to the present isua ice margin our data are not consistent with current ice sheet models that overestimate the middle holocene ice retreat in the isua region of south western greenland

asynchronous response of marine terminating outlet glaciers during deglaciation of the fennoscandian ice sheet this is the accepted manuscript version published version is available at http dx doi org 10 1130 g35299 1

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

early to middle holocene valley glaciations on northernmost greenland abstract this paper presents the glacial stratigraphy and palaeoenvironmental evolution around constable bugt johannes v jensen land located on the north coast of greenland this is a land of extreme climate polar desert conditions and a coast bound by a permanent sea ice cover our data covers the period from the last glacial maximum lgm 18 22 cal ka bp into the holocene it records the history of a shelf based glaciation with ice flowing eastward along the coast as well as two local valley glacier advances from the south during the holocene with ice on the coastal plain during the lgm glaciolacustrine basins formed in marginal positions and in ice dammed valleys to the south into the mountainous area of peary land with the break up of shelf based ice there was a gradual marine inundation at which the marine limit formed at 45 m a s l this initial early holocene ice advance from the south formed prominent valley mouth moraines especially in sifs valley here both glaciolacustrine and marine sediments were remoulded and or dislocated as thrust blocks into a moraine ridge spanning more than 1 km in width and 60 m in height radiocarbon ages of sediments incorporated in this moraine as well as from on lapping sediments suggest that the moraine formed between 9 6 and 6 3 cal ka bp based on 14 c dating results the youngest ice advance phase can be narrowed down to 14 c ages between 5 5 5 0 cal ka bp the recorded ice advances took place during the holocene thermal maximum htm for north greenland the last one close to the beginning of the neoglacial cooling during the htm we have recorded a period of 2500 years during which the north coast of greenland as opposed to today experienced an absence to very restricted occurrence of land fast or multi year sea ice this observation can be explained by the altitudinal and temporal distribution of beach ridge complexes that must have formed by wave action and thus requiring at least partial open water conditions with a moisture source at hand we propose that this lead to enhanced precipitation in the near coastal areas which coupled to documented htm cold reversals caused a lowered glaciation limit and led to a positive mass balance and subsequent ice advance

the influence of ice marginal setting on early holocene retreat rates in central west greenland ice sheet reconstructions from diverse ice margin settings spanning multiple millennia are needed to assess the reaction of the greenland ice sheet gris to millennial scale climatic forcing and to place historical records in a longer term context here we present 18 new cosmogenic 10 be exposure ages and five new radiocarbon ages that constrain the early holocene retreat of the gris in the disko bugt region in both a marine and a land based setting results indicate similar rates of early holocene retreat of 40 50m a 1 from transects in torsukattak fjord marine setting and the naternaq area land based setting we compile seven previously published chronologies of deglaciation from west greenland which yield early holocene retreat rates ranging from 10 to 65m a 1 similar to those determined for our two study areas this work demonstrates that when averaged on millennial timescales retreat rates were remarkably similar along the western gris margin furthermore the retreat rates calculated here demonstrate that terrestrial sectors of ice sheets can retreat at net rates comparable to their marine counterparts copyright 2015 john wiley sons ltd

glacier acceleration and thinning after ice shelf collapse in the larsen b embayment antarctica 1 ice velocities derived from five landsat 7 images acquired between january 2000 and february 2003 show a two to six fold increase in centerline speed of four glaciers flowing into the now collapsed section of the larsen b ice shelf satellite laser altimetry from icesat indicates the surface of hektoria glacier lowered by up to 38 6 m in a six month period beginning one year after the break up in march 2002 smaller elevation losses are observed for crane and jorum glaciers over a later 5 month period two glaciers south of the collapse area flask and leppard show little change in speed or elevation seasonal variations in speed preceding the large post collapse velocity increases suggest that both summer melt percolation and changes in the stress field due to shelf removal play a major role in glacier dynamics

a 100 yr record of ocean temperature control on the stability of jakobshavn isbrae west greenland an understanding of the interaction between ice sheet dynamics and forcing mechanisms such as oceanic and atmospheric circulation is important because of the potential contribution of these processes to constraining models that seek to predict future rates of sea level change here we report new benthic foraminiferal data from disko bugt west greenland showing a close correlation between subsurface ocean temperature changes and the ice margin position of the glacier jakobshavn isbrae over the past 100 yr in particular our faunal data show that warm ocean currents entered a bay disko bugt during the retreat phases of jakobshavn isbrae from a d 1920 to 1950 and since 1998 we also show a link between west greenland ocean temperature and the atlantic multidecadal oscillation a key climate indicator in the north atlantic ocean the close coupling between the oceans and the cryosphere identified here should be assessed in future projections of sea level change

ice flow in greenland for the international polar year 2008 2009 a digital representation of ice surface velocity is essential for a variety of glaciological geologic and geophysical analyses and modeling here we present a new reference comprehensive high resolution digital mosaic of ice motion in greenland assembled from satellite radar interferometry data acquired during the international polar year 2008 to 2009 by the envisat advanced synthetic aperture radar asar the advanced land observation system alos s phase array l band sar palsar and the radarsat 1 sar that covers 99 of the ice sheet in area the best mapping performance is obtained using alos palsar data due to higher levels of temporal coherence at the l band frequency but c band frequency sar data are less affected by the ionosphere the ice motion map reveals various flow regimes ranging from patterned enhanced flow into a few large glaciers in the cold low precipitation areas of north greenland to diffuse enhanced flow into numerous narrow fast moving glaciers in the warmer high precipitation sectors of northwest and southeast greenland we find that the 100 fastest glaciers v 800m yr drain 66 of the ice sheet in area marine terminating glaciers drain 88 of greenland and basal sliding motion dominates internal deformation over more than 50 of the ice sheet this view of ice sheet motion provides significant new constraints on ice flow modeling copyright 2012 by the american geophysical union

greenland ice sheet response to external forcing kinematic wave modeling is used to evaluate possible responses of the greenland ice sheet to changes in its surface mass balance in the approach followed here the reference state is defined based on measured velocity and discharge flux along the central flow line of petermann glacier in the northwest and perturbations on this state are considered the results indicate that significant rates of thickness change can occur immediately after the prescribed change in surface mass balance but adjustments in flow rapidly diminish these rates to a few centimeters per year at most full adjustment of the ice sheet requires times of the order of 1000 years the instability mechanism known as the jakobshavn effect is discussed and based on observational evidence as well as results from prior modeling studies it is concluded that this is an unlikely mechanism for destabilizing major drainage basins of the greenland ice sheet

an investigation of aspects of mine waste from a kyanite mine central virginia usa kyanite mining corporation located in dillwyn virginia has been in operation for over 50 years and their local operation is the largest kyanite mine in the world as part of the processing at this location a magnetic separate is generated and a minimum estimation of 3 57 million tons of waste has accumulated currently no use for the magnetic separate has been identified we investigated eight representative samples of the magnetic mine waste which varied in color from a dark tan to black to determine if the waste could be recycled as an ore or could be used as an environmental media mineralogical investigations indicate the composition of the magnetic mine waste is dominated by magnetite kyanite lesser amounts of hematite and charcoal magnetite occurs as fine grained crystals and as inclusions in kyanite hematite occurs largely as botryoidal textures as discrete grains and as coatings on kyanite grains fe oxide spheres ranging in diameter from approximately 5 100 m are common and may compose up to 10 in some samples titanium dioxide was rarely observed as coatings on silicate mineral grains energy dispersive spectroscopy analysis on magnetite crystals indicates they have end member compositions bulk property investigations indicate that grain size distributions of samples are primarily unimodal with 20 40 of material being between 0 600 and 0 250 mm hydraulic conductivity values of samples investigated vary between 0 0036 and 0 0077 cm s and are broadly consistent with those expected of sands with similar grain size distributions in addition to the magnetic waste stream a light blue water soluble amorphous cu sulfate occurs as a coating on surfaces of boulders the coating is composed of rounded interlocking particles 5 60 m in diameter this material is of some environmental concern for freshwater invertebrates but can be managed using sorption media hyperspectral data were gathered of the magnetic separate kyanite ore samples and the light blue cu sulfate the signatures of the kyanite ore the blue mineral coating and a mixture of the two provide spectral fingerprints that an imaging spectrometer could exploit for rapid detection and subsequent environmental monitoring

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

new observations on the relative sea level and deglacial history of greenland from innaarsuit disko bugt relative sea level rsl data derived from isolation basins at innaarsuit a site on the south shores of the large marine embayment of disko bugt west greenland record rapid rsl fall from the marine limit ca 108 m at 10 300 9900 cal yr b p to reach the present sea level at 3500 cal yr b p since 2000 cal yr b p rsl rose ca 3 m to the present when compared with data from elsewhere in disko bugt our results suggest that the embayment was deglaciated later and more quickly than previously thought at or slightly before 10 300 cal yr b p the northern part of disko bugt experienced less rebound ca 10 m at 6000 cal yr b p compared with areas to the south submergence during the late holocene supports a model of crustal down warping as a result of renewed ice sheet growth during the neoglacial there is little evidence for west to east differences in crustal rebound across the southern shores of disko bugt

surface melt induced acceleration of greenland ice sheet flow ice flow at a location in the equilibrium zone of the west central greenland ice sheet accelerates above the midwinter average rate during periods of summer melting the near coincidence of the ice acceleration with the duration of surface melting followed by deceleration after the melting ceases indicates that glacial sliding is enhanced by rapid migration of surface meltwater to the ice bedrock interface interannual variations in the ice acceleration are correlated with variations in the intensity of the surface melting with larger increases accompanying higher amounts of summer melting the indicated coupling between surface melting and ice sheet flow provides a mechanism for rapid large scale dynamic responses of ice sheets to climate warming

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

paleoenvironments during younger dryas early holocene retreat of the greenland ice sheet from outer disko trough central west greenland paleoenvironments during the late younger dryas through early holocene retreat of the greenland ice sheet from the outer shelf in the disko trough system of central west greenland were investigated via lithofacies foraminifera dinocysts and sediment provenance analyses in radiocarbon dated sediment cores from the upper slope jr175 vc35 and outer shelf jr175 vc20 and hu2008029 070cc core data show that the ice margin retreated rapidly from the outer shelf by calving beginning by 12 2k cal a bp under cold paleoceano graphic conditions with up to 11 months of sea ice ice retreat into disko bugt was well underway by 10 9k cal a bp enhanced ice sheet ablation in disko bugt and elsewhere along the west greenland coast is inferred from cold glacial marine conditions associated with high sedimentation rates between 10 9 and 9 5k cal a bp on the outer shelf glacial marine conditions are recorded on the outer shelf until 7 8k cal a bp detrital carbonate bearing sediments rich in 2 mm clasts deposited between 11 6 and 10 6k cal a bp indicate that icebergs calved from northern baffin bay ice margins were melting and releasing sediments along west greenland while the greenland ice sheet margin was retreating into disko bugt copyright 2013 john wiley sons ltd

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

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

an extensive and dynamic ice sheet on the west greenland shelf during the last glacial cycle considerable uncertainty surrounds the extent and timing of the advance and retreat of the greenland ice sheet gis on the continental shelf bordering baffin bay during the last glacial cycle here we use marine geophysical and geological data to show that fast flowing ice sheet outlets including the ancestral jakobshavn isbrae expanded several hundred kilometers to the shelf edge during the last glaciation ca 20 ka retreat of these outlets was asynchronous initial retreat from the shelf edge was underway by 14 880 calibrated cal yr b p in uummannaq trough radiocarbon dates from the adjacent disko trough and adjoining trough mouth fan imply later deglaciation of jakobshavn isbrae and significantly an extensive readvance and rapid retreat of this outlet during the younger dryas stadial yd this is notable because it is the first evidence of a major advance of the gis during the yd on the west greenland shelf although the short duration suggests that it may have been out of phase with yd temperatures

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

aerial photographs reveal late 20th century dynamic ice loss in northwestern greenland global warming is predicted to have a profound impact on the greenland ice sheet and its contribution to global sea level rise recent mass loss in the northwest of greenland has been substantial using aerial photographs we produced digital elevation models and extended the time record of recent observed marginal dynamic thinning back to the mid 1980s we reveal two independent dynamic ice loss events on the northwestern greenland ice sheet margin from 1985 to 1993 and 2005 to 2010 which were separated by limited mass changes our results suggest that the ice mass changes in this sector were primarily caused by short lived dynamic ice loss events rather than changes in the surface mass balance this finding challenges predictions about the future response of the greenland ice sheet to increasing global temperatures

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

age of the orkendalen moraines kangerlussuaq greenland constraints on the extent of the southwestern margin of the greenland ice sheet during the holocene abstract although greenland ice core records register relatively stable holocene climate conditions the lower elevation margins of the greenland ice sheet gris experienced significant holocene fluctuations these fluctuations include ice sheet recession during the holocene thermal maximum 9 5 ka and advance during the little ice age lia a d 1350 1880 determining the extent and timing of these fluctuations is important for understanding the response of the gris to interglacial climate conditions both warmer and colder than at present and for developing accurate ice sheet models sets of moraines marking past extents of the southwestern gris margin occur in the kangerlussuaq region we focus on the orkendalen moraines a prominent moraine set located within 2 km of the modern ice margin and just outboard of the lia moraines we present the first 10be ages of the orkendalen moraines indicating they were deposited at 6 8 0 3 ka the geomorphic relationship between the orkendalen and lia moraines indicates that the ice sheet margin was inboard of its orkendalen extent between 6 8 ka and the culmination of the lia the age of the orkendalen moraines provides an important constraint on the extent of the southwestern gris during the middle holocene

acceleration of jakobshavn isbrae triggered by warm subsurface ocean waters observations over past decades show a sudden switch of jakobshavn isbrae a large outlet glacier feeding a deep ocean fjord on greenland s west coast from slow thickening to rapid thinning in 1997 this switch is associated with a doubling in glacier velocity hydrographic data show a concurrent sudden increase in subsurface ocean temperatures along the entire west coast of greenland suggesting that the changes in jakobshavn isbrae were triggered by the arrival of relatively warm water originating from the irminger sea observations over the past decades show a rapid acceleration of several outlet glaciers in greenland and antarctica1 one of the largest changes is a sudden switch of jakobshavn isbrae a large outlet glacier feeding a deep ocean fjord on greenland s west coast from slow thickening to rapid thinning2 in 1997 associated with a doubling in glacier velocity3 suggested explanations for the speed up of jakobshavn isbrae include increased lubrication of the ice bedrock interface as more meltwater has drained to the glacier bed during recent warmer summers4 and weakening and break up of the floating ice tongue that buttressed the glacier5 here we present hydrographic data that show a sudden increase in subsurface ocean temperature in 1997 along the entire west coast of greenland suggesting that the changes in jakobshavn isbrae were instead triggered by the arrival of relatively warm water originating from the irminger sea near iceland we trace these oceanic changes back to changes in the atmospheric circulation in the north atlantic region we conclude that the prediction of future rapid dynamic responses of other outlet glaciers to climate change will require an improved understanding of the effect of changes in regional ocean and atmosphere circulation on the delivery of warm subsurface waters to the periphery of the ice sheets

amino acid ratios in reworked marine bivalve shells constrain greenland ice sheet history during the holocene reconstructions of ice sheet fluctuations during the holocene which encompassed cooler and warmer conditions than those that are captured in the historic record help to elucidate ice margin sensitivity to climate change we used amino acid geochronology to constrain the history of the western greenland ice sheet margin during intervals of relative warmth in the middle holocene we measured the extent of amino acid racemization in 251 ice sheet reworked marine bivalve shells from three locations spanning western greenland a significant relationship between shell age and the ratio of aspartic acid asp isomers asp d l was revealed using bayesian model fitting on 20 radiocarbon dated shell fragments the range of asp inferred bivalve ages at each site corresponds well with independent records of early holocene ice retreat and late holocene ice advance furthermore the frequency of asp inferred bivalve ages from the three widely separated locations is nearly identical with most ages between 5 and 3 ka coinciding with optimum oceanic conditions because ice margin changes in western greenland are tightly linked with oceanographic conditions the distribution of reworked bivalve ages provides important information about relative ice margin position during smaller than present ice sheet configurations this approach adds a new chronometer to our toolkit for constraining smaller than present ice sheet configurations and may have wide applicability around greenland

glacimarine sedimentary processes and depositional environments in an embayment fed by west greenland ice streams abstract the extent and behaviour of the central west greenland sector of the greenland ice sheet gis during the last glacial maximum lgm and the following deglaciation remains poorly constrained to investigate deglacial marine environments and sedimentary processes in an area fed by several lgm ice streams we now report findings from a 3 5 khz sub bottom profiler survey acquired in and around disko bay in 2009 sediment thicknesses and volumes in three glaciated areas disko bay southern vaigat and egedesminde dyb are fully constrained for the first time acoustic facies types and distributions were also mapped the largest sediment thicknesses 256 m and widest variation in acoustic character was observed in disko bay adjacent to the mouth of jakobshavns isfjord significant sediment thicknesses were also observed in isolated basins in the egedesminde dyb trough and in a trough in southern vaigat strait up to 110 m given low modern sedimentation rates these thick sediment packages are inferred to record the retreat of glaciers from the middle shelf through disko bay and into both the jakobshavns and torssukatak fjord systems in central west greenland our results highlight similarities in deglacial sedimentary processes across the study area when the margins of retreating glaciers supplied large volumes of sediment to the marine environment from sediment laden meltwater plumes and melting icebergs we estimate the sediment flux for the palaeo jakobshavn ice stream while the ice margin was stable at a fjord entrance sill to be 1 6 3 6 10 7 m 3 a 1 assuming a flux at the upper end of our range for the torssukatak fjord system requires the grounded ice margin to be stable for about 450 years during retreat the sediment fluxes we estimate are within the range of previously calculated fluxes for other arctic and antarctic ice streams and suggest that large volumes of meltwater and sediment were available at the base of the outlet glaciers during deglaciation even during periods of quasi stability retreat of the ice margins into the fjord systems is characterised by a rapid transition to ice distal sedimentation by rainout of iceberg rafted detritus ird and hemipelagic material accumulation rates drop to 2 mm a 1 this study demonstrates the variability in glacimarine processes and environments on high latitude continental margins and highlights the importance of local factors such as bedrock morphology as well as glacio dynamic factors on sedimentation

deglaciation of a major palaeo ice stream in disko trough west greenland recent work has confirmed that grounded ice reached the shelf break in central west greenland during the last glacial maximum lgm here we use a combination of marine sediment core data including glacimarine lithofacies and ird proxy records and geomorphological and acoustic facies evidence to examine the nature of and controls on the retreat of a major outlet of the western sector of the greenland ice sheet gris across the shelf retreat of this outlet which contained the ancestral jakobshavns isbrae ice stream from the outer shelf in disko trough was rapid and progressed predominantly through iceberg calving however minor pauses in retreat tens of years occurred on the middle shelf at a trough narrowing forming subtle grounding zone wedges by 12 1 cal kyr bp ice had retreated to a basalt escarpment and shallow banks on the inner continental shelf where it was pinned and stabilised for at least 100 years during this time the ice margin appears to have formed a calving bay over the trough and melting became an important mechanism of ice mass loss fine grained sediments muds were deposited alternately with ird rich sediments diamictons forming a characteristic deglacial lithofacies that may be related to seasonal climatic cycles high influxes of subglacial meltwater emanating from the nearby ice margins deposited muddy sediments during the warmer summer months whereas winters were dominated by iceberg calving leading to the deposition of the diamictons this is the first example of this glacimarine lithofacies from a continental shelf setting and we suggest that the calving bay configuration of the ice margin plus the switching between calving and melting as ablation mechanisms facilitated its deposition by channelling meltwater and icebergs through the inner trough the occurrence of a major stillstand on the inner shelf in disko trough demonstrates that the ice dynamical response to local topography was a crucial control on the behaviour of a major outlet in this sector of the gris during retreat

variable north atlantic climate seesaw patterns documented by a late holocene marine record from disko bugt west greenland abstract the reconstruction of past sea surface conditions in the labrador sea is essential for understanding climate fluctuations in the north atlantic region we here study late holocene sea surface conditions off west greenland in order to elucidate the possible relationship between a north atlantic seesaw and centennial to millennial scale climate fluctuations in the labrador sea region for that purpose we have studied the particulate organic matter especially dinoflagellate cysts and acritarchs from two marine sediment cores from disko bugt central west greenland our data show significant variations in sea surface temperature and sea ice cover during the last ca 3200 years after a cooling at ca 2 9 ka cal bp presumably related to the neoglacial cooling seen in large parts of the northern hemisphere the area was subjected to significant variability both in the entrainment of atlantic water west greenland current water and in atmospheric temperatures from 2 0 1 5 ka cal bp corresponding to the later part of the roman warm period the area experienced a return to a stronger influx of atlantic water and an increased fresh water influx from land probably related to increased precipitation or to melt water outflow from the nearby inland ice the dark ages 1 5 1 3 ka cal bp were characterised by an only minor cooling of the surface waters however as seen in other records from the labrador sea region the beginning of the medieval warm period 1 3 0 9 ka cal bp signified a severe cooling presumably due to a significant reduction in atlantic water entrainment the cold conditions continued through the little ice age after 0 9 ka cal bp although the area seems to have experienced a minor decrease in sea ice cover until 0 5 ka cal b p after which sea ice cover may again have increased the period of modern warming is not represented in our data our study shows that a north atlantic oscillation type pattern played a significant role in the late holocene centennial to millennial scale climate fluctuations in the labrador sea region however this cannot explain the full complexity of the climate signal the fact that a simple pattern of cold versus warm climate scenario does not exist demonstrates that it will hardly be feasible to select the correct baseline data set when modelling future climate development

changes in ice front position on greenland s outlet glaciers from 1992 to 2007 1 previous studies in greenland show that retreat of tidewater glaciers may be linked to recent increases in ice loss raising greenland s contribution to sea level rise we examined ice front changes of 203 tidewater glaciers land terminating glaciers and glaciers terminating with ice shelves to understand greenland glacier behavior over three periods 1992 2000 2000 2006 and 2006 2007 we observed synchronous ice sheet wide increases in tidewater retreat during 2000 2006 relative to 1992 2000 coinciding with a 1 1 c increase in mean summer temperature at coastal weather stations rates of retreat for the southeast and east slowed during 2006 2007 when temperatures were slightly cooler than the 2000 2006 average our work suggests that regional greenland tidewater retreat responds strongly to climate change with higher temperatures corresponding to increasing retreat and helps confirm a link between ice thickness velocity and ice front position

superheavy s isotopes from glacier associated sediments of the neoproterozoic of south china oceanic anoxia or sulfate limitation black shales and mn carbonates interbedded with glacial deposits from the neo proterozoic of southern china exhibit extremely heavy values of pyrite s isotopes that may reflect the peculiar environment of earth at this time 34 s averages 30 at tanganshan and 44 at xiangtan compared with typical values of 0 to 5 found in younger deposits furthermore there is no distinction between the shales and the mn carbonate ores in the neoproterozoic unlike the younger deposits which show much lighter 34 s in the shales than in the mn ores the spread is 25 most other chemical parameters are very similar to both the younger mn deposits and those from the paleoproterozoic the exception is the rare earth elements ree all neoproterozoic fe ores and most neoproterozoic mn ores lack the positive eu anomaly that characterizes archean and paleoproterozoic fe mn accumulations on the other hand neoproterozoic mn deposits have positive ce anomalies on north american shale composite nasc normalized plots in contrast to other mnco 3 ores the ree is also higher than in other mn deposits but lower than in modern deep sea crusts sulfide s values in all neoproterozoic shales tend to be exceptionally variable and to often show much heavier values than can be found in marine strata from the phanerozoic therefore the anomalous 34 s values we observed reflect peculiar conditions in the world oceans at this time rather than purely local effects times of enrichment of seawater sulfate in 34 s do not correspond to periods of glaciation so the likely cause of the s isotope patterns is not worldwide glaciation but a generally low level of dissolved sulfate s in the neoproterozoic oceans that allowed modest increases in the amounts of s removed as pyrite to drive down the oceanic s reservoir enough to produce strong rayleigh reservoir effects the abundance worldwide of sturtian age mn and fe deposits indicates an increase in fe flux to the oceans that would have been sufficient to depress so 4 2 levels severely and to result in residu al dissolved s extremely enriched in 34 s ree evidence indicates that most of this enhanced fe and mn flux came from diagenetic remobilization of detrital oxides

isolation basin stratigraphy and holocene relative sea level change on arveprinsen ejland disko bugt west greenland this paper presents the results of an investigation into holocene relative sea level rsl change isostatic rebound and ice sheet dynamics in disko bugt west greenland data collected from nine isolation basins on arveprinsen ejland east disko bugt show that mean sea level fell continuously from ca 70 m at 9 9 ka cal yr bp 8 9 ka 14c yr bp to reach a minimum of ca 5 m at 2 8 ka cal yr bp 2 5 ka 14c yr bp before rising to the present day a west east gradient in isostatic uplift across disko bugt is confirmed with reduced rebound observed in east disko bugt however rsl differences up to 20 m at 7 8 ka to 6 8 ka cal yr bp 7 ka to 6 ka 14c yr bp also exist within east disko bugt suggesting a significant north south component to the area s isostatic history the observed magnitude and timing of late holocene rsl rise is not compatible with regional forebulge collapse instead rsl rise began first in the eastern part of the bay as might be expected under a scenario of crustal subsidence caused by neoglacial ice sheet readvance the results of this study demonstrate the potential of isolation basin data for local and regional rsl studies in greenland and the importance of avoiding data compilations from areas where the isobase orientation is uncertain copyright 1999 john wiley sons ltd

mineralogical and geochemical investigation of clay rich mine tailings from a closed phosphate mine bartow florida usa clay rich mine tailings from phosphate mine operations in florida are a major environmental and economic problem options for reclamation and restoration for these tailings are very limited and are fundamentally restricted by poor physical properties such as low mechanical strength low hydraulic conductivity and heavy metal content the major control on these bulk physical properties is the mineralogy of the materials eight continuous push borings were obtained to investigate stratigraphy mineralogy aspects of geochemistry and bulk properties of a deposit of clay rich mine tailings from a phosphate mine near bartow florida that ceased operations in the early 1970s stratigraphy is dominated by laminated clay rich sediment with minor units of silt and sand an intact kaolinite liner occurs near the impoundment walls and the impoundment floor has approximately 4 m of relief moisture content varies from 4 35 to 57 40 wt and organic content varies from 0 41 to 9 53 wt bulk xrf investigation indicates that the p2o5 concentrations vary from approximately 4 to 21 wt a very strong correlation r2 0 92 between cao and p2o5 indicates that apatite is a major control on the phosphate the strong correlation r2 0 77 of al2o3 and tio2 suggests that the source materials for this deposit are comparatively uniform a number of heavy metal elements and trace elements occur cr v ni cu are interpreted to be in phosphate minerals largely apatite sr and pb are interpreted to be in both phyllosilicates and phosphate minerals two populations of apatite were observed in the clay sized fraction one that was fe and si bearing and another that was only si bearing fe bearing apatite had fe2o3 contents that varied from 0 38 to 5 32 wt and sio2 contents that varied from 0 90 to 3 32 wt the other apatite population had a wider range of sio2 contents that varied from 0 77 to 8 80 wt tem imaging shows that apatite grains are dominantly single crystals with lesser amounts of aggregates wavellite commonly occurs as individual or clusters of lath like crystals and the chemical composition differs from the pure aluminium phosphate end member with average concentrations of components being that of cao 1 57 wt fe2o3 1 98 wt sio2 5 94 wt in the clay sized phosphate minerals investigated no fluorine was found above detection limit approximately 0 15 wt nor was any uranium radium heavy metal or ree element detected the phyllosilicate mineralogy of the deposit is dominated by smectite montmorillonite with lesser amounts of nontronite palygorskite illite and kaolinite no systematic variation in the relative proportions of phyllosilicates was observed in the clay deposit energy dispersive spectroscopy eds analysis indicates that chemical compositions of phyllosilicates are somewhat typical but overall are enriched with respect to fe compared to theoretical end members the relative enrichment of fe is interpreted to be a primary sedimentary feature ca content in smectite minerals is high and may inhibit stabilization using lime or similar methods the high percentages of montmorillonite and palygorskite explain the high bulk water contents observed this investigation provides fundamentally new details regarding clay tailing deposits from closed phosphate mines in central florida which can be used in restoration and reclamation efforts

mineralogical and geochemical investigations of silicate rich mine waste from a kyanite mine in central virginia implications for mine waste recycling a kyanite mine in central virginia produces a silicate rich waste stream which accumulates at a rate of 450 000 600 000 tons per year an estimated 27 million tons of this waste stream has accumulated over the past 60 years grain size distribution varies between 1 000 and 0 053 mm and is commonly bimodal with modes typically being 0 425 and 0 250 mm and uniformity coefficients vary from 2 000 to 2 333 hydraulic conductivity values vary from 0 017 to 0 047 cm s mineralogy of the waste stream consists of quartz muscovite kyanite and hematite muscovite grains have distinct chemical compositions with significant na2o content 1 12 2 66 wt tio2 content 0 63 1 68 wt tio2 and fe content expressed as fe2o3 up to 1 37 wt major element compositions of samples were dominated by sio2 87 894 90 997 wt al2o3 6 759 7 741 wt fe2o3 1 136 1 283 wt and k2o 0 369 0 606 wt with other components being 1 000 wt elements of environmental concern v cr ni cu zn as ag sn sb ba hg tl and pb were detected however the concentrations of all elements except ni were below that of the kyanite quartzites in the region from which the waste is derived both major and trace element compositions indicate minimal variation in composition the waste stream has potential for recycling muscovite is suitable for recycling as a paint pigment or other industrial applications muscovite and hematite are commonly intergrown and are interpreted to be material where much of the elements of environmental concern are concentrated reprocessing of the waste stream to separate muscovite from other components may enable the waste stream to be used as constructed wetland media for virginia and nearby states recycling of this mine waste may have a positive impact on the local economy of buckingham county and aid in mitigation of wetland loss

an aerial view of 80 years of climate related glacier fluctuations in southeast greenland both marine and land terminating glaciers in southeast greenland have experienced dramatic recent retreat an 80 year record of historical aerial photographs and satellite imagery shows that many land terminating glaciers in this region retreated more rapidly in the 1930s than today whereas marine terminating glaciers have retreated faster in the 2000s

relative sea level changes during the holocene in the sisimiut area south western greenland holocene relative sea level rsl changes have been investigated by analysing and dating isolation sequences from five lakes near sisimiut in south western greenland the transitions between marine and lacustrine sediments were determined from elemental analyses and analyses of macroscopic plant and animal remains radiocarbon dating was used to provide minimum ages for the transitions and to construct a rsl curve dating of a shell of the marine bivalve macoma balthica indicates that deglaciation of the lowlands occurred in the early holocene at around 10 900 cal a bp the rsl curve shows initial rapid regression from the marine limit at around 140 m implying strong glacio isostatic rebound we suggest that the margin of the greenland ice sheet was located at the shelf break during the last glacial maximum frequent remains of the ostracode sarcypridopsis aculeata which is a thermophilous brackish water species that is unknown from the extant fauna of greenland in one of the basins around 8500 cal a bp may mark the beginning of the holocene thermal maximum in the region copyright 2011 john wiley sons ltd