phylogeographic analysis of the mid holocene mammoth from qagnaxˆ cave st paul island alaska abstract remains of a woolly mammoth mammuthus primigenius were found in qagnax cave a lava tube cave on st paul island in the pribilof islands 500 km west of the alaskan mainland in the bering sea several dates converge on 5725 14c yr bp making these the youngest mammoth remains discovered in north america and among the few holocene mammoths known genetic analysis of the cytochrome b gene and adjacent regions of the mitochondrial genome demonstrates that the qagnax mammoth is highly derived possessing several unique polymorphisms not found in other mammoths however while this is consistent with a recent insular isolation scenario phylogenetic analysis suggests that the specimen represents a population whose isolation from other mammoths occurred at or well before the terminal pleistocene submergence of the bering land bridge it is possible that it represents a member of a land bridge subclade of woolly mammoths that remained distinct from mainland alaskan populations but was not restricted to highland areas until the land bridge was submerged additional eastern beringian and particularly insular mammoth dna sequences are required to explore this possibility

identification of coherent links between interannual sedimentary structures and daily meteorological observations in arctic proglacial lacustrine varves potentials and limitations proglacial lacustrine sediments from high arctic lake r 76 17 9 n 90 59 3 w unofficial name are shown to be annually laminated varved and contain a variety of subannual structures the formation of the subannual structures and overall varve was controlled by a combination of meteorologic temperature and rainfall and geomorphic factors using a training set of the ten thickest varves in the 38 year sedimentary record a heuristic model was developed to link subannual structures with regional meteorological conditions within the training set significant correlations were shown between subannual structure thickness and the magnitude of the corresponding melt event defined as a period of continuously positive temperature however these correlations deteriorated as the varves progressively thinned and several varves exhibited no relationship between their subannual structures and respective meteorological conditions grain size analyses showed that the thin varves were significantly finer than the thick varves and are inferred to reflect changed sediment inflow patterns that altered deposition and reduced the fidelity of the model despite these complexities this study identified the potential to produce long term subannual reconstructions of weather conditions model results revealed the limitations of simple varve meteorology relationships as well as identified necessary environmental and sampling conditions required to produce a more robust model for future applications

holocene delevelling of devon island arctic canada implications for ice sheet geometry and crustal response the raised beaches and deltas of devon island contain an abundance of dateable materials a large set of radiocarbon dates 228 154 of which are new are used to construct relative sea level curves and isobase maps for the island the best materials for this purpose are driftwood logs 61 dates and bowhead whale bones 74 dates from raised beaches and mollusc shells from marine limit deltas 20 dates or from altitudes close to marine limit 14 dates during the last glacial maximum the island is thought to have lain beneath the southeastern flank of the innuitian ice sheet the relative sea level history is congruent with that inferred ice configuration the island spans half the ice sheet width relative sea level curves are of simple exponential form except near the glacial limit where an early holocene emergence proceeded to a middle holocene lowstand below present sea level which was followed by submergence attending the passage of the crustal forebulge the response times of relative sea lev

a heuristic evaluation of long term global sea level acceleration in view of the scientific and social implications the global mean sea level rise gmslr and its possible causes and future trend have been a challenge for so long for the twentieth century reconstructions generally indicate a rate of gmslr in the range of 1 5 to 2 0 mm yr 1 however the existence of nonlinear trends is still debated and current estimates of the secular acceleration are subject to ample uncertainties here we use various gmslr estimates published on scholarly journals since the 1940s for a heuristic assessment of global sea level acceleration the approach alternative to sea level reconstructions is based on simple statistical methods and exploits the principles of meta analysis our results point to a global sea level acceleration of 0 54 0 27 mm yr century 1 between 1898 and 1975 this supports independent estimates and suggests that a sea level acceleration since the early 1900s is more likely than currently believed

last glacial maximum and deglaciation of devon island arctic canada support for an innuitian ice sheet abstract the extent and origin of quarternary glaciers in the queen elizabeth islands of arctic canada especially during the last glacial maximum lgm has been debated for well over a century no consensus has yet emerged and the spectrum of interpretations within the last decade is the broadest ever the glacial geology of devon island strongly supports the late wisconsinan innuitian ice sheet hypothesis during lgm the southeastern part of the queen elizabeth islands was covered by an ice sheet flowing from a centre or a divide centrally located in the archipelago another ice divide extended from the centre across devon island flow from the innuitian centre and convergent flow from devon island and probably also from cornwallis and bathurst islands sustained an ice stream in wellington channel ice was locally advancing to its lgm limit about 23 ka bp recession in the vicinity of the present coastline was underway by 10 ka bp and final ice remnants west of the present devon ice cap vanished about 8 ka bp the island bears the same two part landscape zonation as do other islands and peninsulas in the region these reflect a cold based core and warm based periphery at lgm

regional variations in atmospheric deposition and sources of anthropogenic lead in lake sediments across the canadian arctic stable pb isotope profiles in dated lake sediment cores were used to gauge the relative amounts and possible sources of anthropogenic pb deposited from the atmosphere in different regions of the canadian arctic a distinct north south difference was found in four high arctic lakes i e north of 66 n in this study recent pb isotopic shifts or concentration increases attributable to anthropogenic pb were negligible the maximum possible contribution from anthropogenic pb was 0 to 19 of acid leachable pb in the 1980s or 1990s in contrast two lakes in the hudson bay region displayed significantly lower pb isotope ratios and threefold to fivefold increases of pb concentrations in modern sediments corresponding to anthropogenic pb inputs of at least 72 to 91 of leachable pb eurasian urban and industrial pb is known to dominate the high arctic atmosphere a possible explanation for its negligible influence on northern lake sediments is that atmospheric pb deposition at northern latitudes is reduced compared with southern regions and is small compared to local geological inputs 210pb deposition declines with increasing latitude apparently because of declining precipitation rates stable pb deposition may be similarly affected meteorological considerations and variations in the post 1900 pb isotopic trajectories indicated that the predominant anthropogenic pb source region in nw hudson bay was eurasia while in se hudson bay it was canada and the united states with a minor eurasian component

recent warming in a 500 year palaeotemperature record from varved sediments upper soper lake baffin island canada laminated sediments from upper soper lake on southern baffin island provide a new 500 year record of temperature change in the arctic radiometric dating using 210pb and pu shows that the light and dark coloured laminae couplets are annually deposited varves dark laminae thickness is strongly correlated to average june temperature from kimmirut r 0 82 reflecting the influence of temperature on snowmelt and fluxes of runoff and suspended sediment this relationship allowed the construction of a palaeotemperature record that documents large amplitude interannual to decadal variability superimposed on distinct century scale trends including 2 c average warming and maximum temperatures during the 1900s similar patterns of change are seen in individual and regionally averaged palaeotemperature records from around the circum arctic upper soper lake records temperatures rates of change and variance during the twentieth century that are all anomal ously high within the context of the last 500 years and outside the observed range of natural variability comparisons of upper soper lake and arctic average palaeotemperature to proxy records of hypothesized forcing mechanisms suggest that the recent warming trend is mostly due to anthropogenic emissions of atmos pheric greenhouse gases the magnitude of the warming and decade scale variability throughout the records however indicate that natural forcing mechanisms such as changing solar irradiance and volcanic activity as well as positive feedbacks within the arctic environment also play an important role

a record of climate over the last millennium based on varved lake sediments from the canadian high arctic a varved sediment record that extends back over the last millennium was recovered from lower murray lake northern ellesmere island nunavut canada 81 20 n 69 30 w flatbed scan images and back scattered electron images were analysed to provide varve thickness and other quantitative sedimentary indices on an annual basis in many studies of lakes from the high arctic varve thickness is a good proxy for summer temperature and we interpret the lower murray lake varves in this way on that basis the lower murray lake varve thickness record suggests that summer temperatures in recent decades were among the warmest of the last millennium comparable with conditions that last occurred in the early twelfth and late thirteenth centuries but estimates based on the sediment accumulation rate do not show such a recent increase the coldest conditions of the little ice age were experienced from ad 1700 to the mid nineteenth century when extensive ice cover on the lake led to widespread anoxic conditions in the deepest parts of the lake basin an overall decline in median grain size over the last 1000 years indicates a reduction in the energy available to transport sediment to the lake many of these features of the record are also observed in other palaeoclimatic records from the north american arctic the very recent appearance of the diatom campylodiscus which was not observed through out the record of the last millennium suggests that a new threshold in the ontogenetic development of the lake has now been passed

signal and noise in four ice core records from the agassiz ice cap ellesmere island canada details of the last millennium for stable isotopes melt and solid conductivity four ice cores and two deep pit auger sequences from the top of the agassiz ice cap have been variously analysed for o18 ecm solid conductivity and ice melt layer stratigraphy the high resolution data are presented on time scales covering about the last 1000 years the 8 time series are compared and the noise examined in terms of snow drifting and wind scouring of winter snow from the higher exposed parts of flow lines the highly scoured 8 records reflect a mixture of summer biased conditions and the amount of winter scoured snow sites away from the ridges and domes are not scoured the signal part of the scoured and unscoured sites is obtained by stacking averaging normalized series the stacked unscoured series of 8 and accumulation are compared to similar stacked series from central greenland for the last century of annual averages the comparison is surprisingly good suggesting that at these resolutions low noise 8 series have some coherence over fairly large distances the percentage melt

patterns of faunal extinction and paleoclimatic change from mid holocene mammoth and polar bear remains pribilof islands alaska abstract qagnax cave a lava tube cave on st paul island in the pribilofs has recently produced a mid holocene vertebrate faunal assemblage including woolly mammoth polar bear caribou and arctic fox several dates on the mammoth remains converge on 5700 14c yr bp these dates 2300 yr younger than mammoth dates previously published from the pribilof islands make these the youngest remains of proboscideans and of non extinct quaternary megafauna recovered from north america persistence of mammoths on the pribilofs is most parsimoniously explained by the isolation of the pribilofs and the lack of human presence in pre russian contact times but an additional factor may have been the local existence of high quality forage in the form of grasses enriched by nutrients derived from local holocene tephras this interpretation is reinforced by stable carbon and nitrogen isotope values obtained from the mammoth remains the endpoint of mammoth survival in the pribilofs is unknown but maybe coterminous with the arrival of polar bears whose remains in the cave date to the neoglacial cold period of 4500 to 3500 14c yr bp the polar bear record corroborates a widespread cooling of the bering sea region at that time

hydrological and sediment yield response to summer rainfall in a small high arctic watershed in cold regions the response and related antecedent mechanisms that produce flood flows from rainfall events have received limited study in 2007 a small watershed at cape bounty melville island nunavut was studied in detail during the melt season two rainfall events on june 30 and july 22 totalling 9 2 and 10 8 mm respectively represented significant contributions to seasonal discharge and sediment transport in a year with a low winter snowpack the precipitation events elevated discharge and suspended sediment concentrations to twice the magnitude of the nival melt and generated the only measurable downstream lacustrine turbidity current of the season in two days rainfall runoff transported 35 of the seasonal suspended sediment load in contrast to 29 transported over the nival freshet the magnitude and intensity of the rain events were not unusual in this setting but the rainfall response was substantial in comparison with equivalent past events exceptional temperatures of july 2007 generated early deep permafrost thaw and ground ice melt the resultant increase in soil moisture amplified the subsequent rainfall runoff and sediment transport response these results demonstrate the importance of antecedent moisture conditions and the role of permafrost active layer development as an important factor in the rainfall runoff and sediment transport response to precipitation events copyright 2009 john wiley sons ltd

hydrochemical and sedimentary responses of paired high arctic watersheds to unusual climate and permafrost disturbance cape bounty melville island canada high arctic river responses to changing hydroclimatic and landscape processes are poorly understood in non glacierized basins snowmelt and rainfall generate river discharge which provides first order control over fluxes further factors include the seasonality of precipitation seasonal active layer development and permafrost disturbance these controls were evaluated in terms of sedimentary and biogeochemical fluxes from paired catchments at cape bounty melville island nunavut during 2006 2009 results indicate that the source of runoff can be more important than the amount of runoff for sediment solutes and organic yields although the snowmelt period is typically the most important time for these yields heavy late summer precipitation events can create disproportionately large yields rainfall increases yields because it hydrologically connects areas otherwise isolated inorganic solute yields from late summer rainfall are higher because the thick active layer maximizes hydrologic interactions with mineral soils and generates high solute concentrations results also indicate that while the catchments are broadly similar subtle topographic differences result in important inter catchment differences in runoff and suspended and dissolved loads the east watershed which had less extensive permafrost disturbance consistently had higher concentrations of dissolved solids these higher dissolved fluxes cannot therefore be explained by thermokarst features but rather by deeper active layer development due to a greater proportion of south facing slopes although warm temperatures in 2007 led to extensive active layer disturbance in the west watershed because the disturbances were largely hydrologically disconnected the total disturbed area was small and inter annual variability in discharge was high there was no detectable response in dissolved loads to disturbances sediment availability increased after 2007 but yields have largely returned to pre disturbance levels results indicate that seasonality and frequency magnitude characteristics of projected increases in precipitation must be considered along with active layer changes to predict the fluvial sedimentary and biogeochemical response to regional climate change copyright 2011 john wiley sons ltd

the latest woolly mammoths mammuthus primigenius blumenbach in europe and asia a review of the current evidence abstract during the last cold stage woolly mammoths ranged very widely across northern eurasia into north america but then disappeared as part of the global phenomenon of late quaternary megafaunal extinction the timing and causes of this highly significant event have generated conflicting opinions and much debate however the overriding need is for more data and recent years have seen the accumulation of significant new finds and radiocarbon dating evidence in particular research is currently focussing on the geographical pattern of extirpation leading to final extinction rather than seeking a single last appearance datum this viewpoint article was commissioned by the editor in chief and is published following the paper by lougas et al dating the extinction of european mammoths new evidence from estonia quat sci rev 21 2002 1347 to place their finding in a wider context we give a brief review of the youngest directly dated mammoth remains from different regions of eurasia based both on published sources and on our own current research this includes a very important new record from cherepovets north russian plain which together with the new date from puurmani estonia indicates the persistence of mammoth in this region close to the pleistocene holocene boundary these and other records suggest that the previous picture of mammoths widespread before 12 000 ka bp uncalibrated radiocarbon years ago then restricted to limited areas of northern siberia although correct in outline has important exceptions which modify our understanding of mammoth extinction despite the many available radiocarbon dates for eurasian mammoth relative to other extinct megafauna it is apparent that much more work is needed only then can we adequately tackle the important question of the cause or causes of extinction whether by climatic environmental change or overkill by human hunters

a 750 yr record of autumn snowfall and temperature variability and winter storminess recorded in the varved sediments of bear lake devon island arctic canada abstract the varve record from high arctic proglacial bear lake reveals a regionally coherent hydroclimatic signal as well as complexities due to changing hydroclimatic and limnologic conditions varve formation is strongly dependent on underflows that exhibit variability in strength during the past 750 yr periods with reduced underflow sedimentation and accumulation rates fail to produce varves in the distal part of the lake isolated coarse silt and sand grains occur in 80 of the varves and are interpreted to be niveo aeolian in origin coarse 500 m sand grains deposited on the lake ice by strong winter winds are notably less common since a d 1850 likely due to reduced storminess regression of the varve thickness record with meteorological records indicates high correlations with autumn september and october temperatures and total monthly snowfall these correlations are best at times when underflow activity is sufficiently strong to produce varves throughout the lake the close association with warmer temperatures and snow bearing synoptic systems moving north in baffin bay suggests that the primary climate signal in the varves is varying autumn snow pack that controls nival discharge in the following year the similarity between the other records of melt season temperature and sea ice cover and the bear lake record suggests that summer and autumn conditions were generally similar across the baffin bay region through much of the last millennium

characteristics of sedimentary varve chronologies a review abstract we constructed a varve data base vdb to study the worldwide distribution of varved sediment records and the fidelity of their varve chronologies clusters of lakes with varved sediments exist in central north america in the canadian arctic and in northern and central europe among the 108 sites included in the vdb varved records are typically 200 500 cm long and cover a period of 1000 2000 years their varve chronologies are often based on counting of annual layers from fresh sediment surfaces and photographs or from epoxy embedded sediment blocks and thin sections the vdb indicates that chronological errors associated with counting sedimentary varves fall generally between 1 and 3 but only 57 of published records are providing quantitative error estimations for their chronologies with a careful documentation of varves and by applying radiometric dating methods to surface sediments as well as using historical events as time markers there is the potential of having centennial long varved records with a very precise age depth control however it is unrealistic to expect errors significantly below 1 from several millennia long sections we found no indication that varve chronologies would have been substantially more accurate and precise in some parts of the world than in others or statistically dependent on varve thickness or temporal extension of a varved sequence according to the vdb close to 90 of the published varve chronologies have been cross checked with some independent dating methods

biolaminated sedimentation in a high arctic freshwater lake a laminated sequence of lacustrine sediment from an arctic coastal lake was examined for potential chronological and successional information the laminae are microbially induced sedimentary structures the unlithified precursor of stromatolites and are previously unreported in the arctic the inferred annual sequence was interpreted to contain a basal clastic unit overlain with successive cyanobacterial and extracellular polymeric substance units the complex succession of laminae and inconclusive dating provide a challenge for identifying the chronological nature of the sedimentary structures markov chain and time series analyses suggest that a plausible quasi annual sequence can be identified to provide a context for palaeo environmental reconstruction recognition of sedimentary structure in recent biolaminated sediments offers a first step towards the palaeo environmental evaluation of the geomicrobiological sequence

temporal patterns of suspended sediment yield following moderate to extreme hydrological events recorded in varved lacustrine sediments a 487 year annually laminated varved sediment record from nicolay lake cornwall island in the canadian high arctic was evaluated to determine the impact that years with high sediment yields had on sediment yields in subsequent years all of the 40 largest years showed evidence for increased sediment yield in the subsequent 10 30 years the positive anomalies in lagging years were approximately scaled according to the size of the initiating year although many intermediate years 25 to 100 year recurrence showed weak or variable responses the smallest events considered 10 to 25 year recurrence showed a consistent but low amplitude response additionally the 10 year events revealed frequent negative sediment yield anomalies in the preceding decade this behaviour was interpreted as a frequent sediment activation cycle initiated by the modest year and leading to sediment yield hysteresis lasting 15 25 years the largest years greater than 50 year recurrence showed consistently above average sediment yields in the preceding decade in part due to the frequent occurrence of moderate q10 years it is hypothesized that temporary storage of sediment and previous initiation of erosion sites resulted in extraordinary sediment yields during intense summer rainfall events this study demonstrates the potential use of varved lake sediment records to improve our understanding of long term sediment dynamics these records present an opportunity to further develop and test sediment dynamic and routing models to gain insight into the interaction of time and space in fluvial and sediment delivery processes copyright 2002 john wiley sons ltd

holocene sediments from a coastal lake on northern devon island nunavut canada sediment cores from lake dv09 northern devon island nunavut canada 75 34 34 n 89 18 55 w were studied to reconstruct the lake ontogeny through analysis and interpretation of the sediment stratigraphy the lake was uplifted from marine inundation 7600 cal bp after a millennium of rapid sediment accumulation which coincided with the holocene thermal maximum in the region accumulation rates decreased over the past 6000 years as the arctic became colder this resulted in the deposition of very fine laminae that were interpreted as varves the uppermost laminated sediments provided a 1600 year history of annual sediment transport and deposition into the lake during periods of warmer temperatures such as between 6000 and 7500 cal bp and during the medieval climate anomaly 950 1300 ce ce christian era hydroclimatic and permafrost slope processes increased sedimentation rates into the basin

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

trace metal profiles in the varved sediment of an arctic lake abstract varved annually laminated sediments offer a rare and physically undisturbed archive of past trace metal deposition and limnological conditions here a high resolution 1 300 year record of metal accumulation is presented from a varved lake sediment on devon island in the canadian high arctic down core concentration profiles of cd cu and zn were positively correlated p

multi proxy record of postglacial environmental change south central melville island northwest territories canada abstract a sediment core from lake bc01 75 10 945 n 111 55 181 w 225 m asl on south central melville island nwt canada provides the first continuous postglacial environmental record for the region fossil pollen results indicate that the postglacial landscape was dominated by poaceae and salix typical of a high arctic plant community whereas the arctic herb oxyria underwent a gradual increase during the late holocene pollen based climate reconstructions suggests the presence of a cold and dry period 12 000 cal yr bp possibly representing the younger dryas followed by warmer and wetter conditions from 11 000 to 5000 cal yr bp likely reflective of the holocene thermal maximum the climate then underwent a gradual cooling and drying from 5000 cal yr bp to the present suggesting a late holocene neoglacial cooling diatom preservation was poor prior to 5000 cal yr bp when conditions were warmest suggesting that diatom dissolution may in part be climatically controlled diatom concentrations were highest 4500 cal yr bp but then decreased substantially by 3500 cal yr bp and remained low before recovering slightly in the 20th century an abrupt warming occurred during the past 70 yr at the site although the magnitude of this warming did not exceed that of the early holocene

holocene climatic records from agassiz ice cap ellesmere island nwt canada four ice cores from the top of the agassiz ice cap and down a flow line have been variously analysed for 8 18o ecm solid conductivity and ice melt layer stratigraphy stratigraphic correlation

paleoenvironments of the canadian high arctic derived from pollen and plant macrofossils problems and potentials abstract analyses of peat sections lake sediments and ice cores provide information about late quaternary arctic environments palynomorphs and plant macrofossils from each of these three types of sediments record different aspects of the environment with particular spatial and temporal scales of resolution in the arctic the limits to the interpretation of past environments are particularly significant problems of low pollen concentrations long distance transport stratigraphic inversions and contamination by fossils from older deposits are more serious in this region due to the biogeographic context that characterizes these high latitudes and influences the particular ecological and geomorphological processes however recent work has shown that past environments can be reconstructed from evidence preserved in high arctic sediments and ice cores if these problems are taken into account before their interpretation

modern and holocene pollen assemblages from some small arctic lakes on somerset island nwt canada abstract modern pollen samples from 15 lakes along a north south transect on western somerset island nwt canada show a decrease in pollen concentrations from the high arctic to the mid arctic zone but there are few differences in the pollen percentages between these sites long distance transport accounts for up to 50 of the pollen in these lake sediments cores from two lakes show few changes in the percentages of important pollen types except for an initial period before 6000 yr b p of increased salix the pollen concentration of lake rs36 from the mid arctic is twice that of lake rs29 from the high arctic and at both sites the concentrations decreased during the past 6000 yr b p this suggests a climatic deterioration during the past 6000 yr which has caused a decrease in the abundance of plants on the landscape

autumn snowfall and hydroclimatic variability during the past millennium inferred from the varved sediments of meromictic lake a northern ellesmere island canada abstract we examined the hydroclimatic signal in a record of annual lamina varve thickness from high arctic lake a ellesmere island 83 00 00 n 75 30 00 w in this unglacierized catchment nival melt is the dominant source for meltwater and transport of sediment to the lake and autumn snowfall is highly influential on varve thickness through the amount of snow available for melt in the following year for the period during which climatic data are available varve thickness in lake a was significantly correlated r 0 50 p r 0 39 p

holocene climate and vegetation change on victoria island western canadian arctic abstract a detailed pollen record from victoria island provides the first quantitative holocene climate reconstruction from the western canadian arctic the pollen percentage data indicate that arctic herbs increased over the holocene in response to long term cooling the influx of locally and regionally derived pollen grains varies throughout the core and tracks several major changes observed in the biogenic silica record from arolik lake alaska and the gisp2 ice core suggesting that climate change closely controlled arctic plant productivity using modern analogue and transfer function techniques we generated quantitative reconstructions of mean july temperature and total annual precipitation for the past 10 000 years to place recent climate changes within the context of holocene climate variability the quantitative reconstructions indicate that july temperature cooled by 1 1 5 c during the holocene the pollen based reconstructions record an increase in temperature of 0 5 c over the last 100 years and the pollen percentage and influx data indicate impacts of recent warming on the regional vegetation