a record of holocene summer climate from a canadian high arctic ice core melt layers in ice cores are formed by melting on the snow pack surface which produces water that percolates down and refreezes in the colder snow layers below melt layers are distinguished by their bubble texture because more ice forms in the snow pack in warm summers than in cool summers the changing concentration with depth of melt layers in snow pits1 2 and ice cores3 5 is an indicator of past summer climate here we report on studies of melt layers in two canadian high arctic surface to bedrock ice cores although changes in elevation of the drill site owing to isostatic depression and uplift may contribute up to 40 of the total climatic signal recorded in the melt layers we interpret their varying concentrations in terms of changing summer temperatures over the past 10 000 years the warmest summers occurred 8 10 kyr ago and the coldest only 150 years ago the summers over the past 100 years have been the warmest for more than 1 000 years but are still not as warm as those of the early holocene the melt layer record is in broad agreement with geological records of glacier retreat during the holocene6 8 indicating that these data also contain information of regional significance

synchronizing ice cores from the renland and agassiz ice caps to the greenland ice core chronology 1 four ice cores from the agassiz ice cap in the canadian high arctic and one ice core from the renland ice cap in eastern greenland have been synchronized to the greenland ice core chronology 2005 gicc05 which is based on annual layer counts in the dye 3 grip and ngrip ice cores volcanic reference horizons seen in electrical conductivity measurements ecm have been used to carry out the synchronization throughout the holocene the agassiz ice cores have been matched to the ngrip ice core ecm signal while the renland core has been matched to the grip ice core ecm signal thus tying the cores to gicc05 furthermore it has been possible to synchronize the renland ice core to ngrip gicc05 in the glacial period back to 60 000 years b2k years before a d 2000 on the basis of a matching of transitions between stadials and interstadials this work brings the total number of ice core records that have been rigorously tied to the gicc05 timescale up to nine renland annual layer thicknesses are increasing with depth during the period from 7 to 8 5 ka b2k a highly unusual observation only matched by a similar thickness increase in the glacial section of the renland core some 60 ka ago annual layer thicknesses in the agassiz ice cores point to a well developed raymond bump in the agassiz ice cap

effect of chemical composition of water on the oxygen 18 and carbon 13 signature preserved in cryogenic carbonates arctic canada implications in paleoclimatic studies abstract this study examines the 18o and 13c composition of cryogenic carbonate deposits in relation to the initial 18o 13cdic and chemical composition of the water from which it precipitated this study focuses on cryogenic calcites precipitated in relation to aufeis aggradation since it offers the possibility of examining the chemical and isotopic partitioning that occurs during freezing the studied aufeis are located in the western canadian arctic yt and nwt a region underlain mostly by limestone bedrock and southern baffin island nu an area of crystalline bedrock the results indicate that the 18o composition of cryogenic calcite from a carbonated environment are slightly depleted over that of the initial 18o of the parent water while those from a non carbonated environment are strongly depleted over the initial 18o of the parent water as a result of the lower calcite saturation state of the parent water this suggest that the 18o of cryogenic carbonates not only depends on the initial 18o composition of the parent water and the temperature at which the carbonate precipitated but also on the calcite saturation state of the parent water and kinetic inhibitions during calcite precipitation given that the aggradation of aufeis occurs under closed system freezing the residual water will become progressively depleted in 18o as a result of the removal of heavier isotopes in the ice in addition freezing imparts a concentration of solutes in the residual water which leads to an increase in calcite saturation index therefore carbonate precipitated in equilibrium from water that has a low calcite saturation index will have a highly depleted 18o composition over that of the initial 18o values of the parent water since the calcite saturation state will only be exceeded in the late stage of freezing by contrast solute and isotopic partitioning during freezing has little effect on the 13c of the cryogenic carbonates as it tends to reflect that of the initial 13cdic value of the parent water these findings have significant implications in the use of cryogenic carbonates in paleoclimate studies care must be taken when interpreting the 18o signature preserved in cryogenic carbonates since their signature might be modified by freezing prior to their precipitation which will lead to a lighter 18o composition of the cryogenic carbonates therefore it would be difficult to use the 18o composition of cryogenic carbonates as a direct proxy in paleoclimatic reconstruction unless details about the chemical composition of parent waters are known nevertheless the 13c composition of the cryogenic carbonates that precipitated under closed system conditions can allow insights into the different water sources contributing to carbonate precipitation

subglacial carbonates constrain basal conditions and oxygen isotopic composition of the laurentide ice sheet over arctic canada subglacially precipitated carbonate crusts spccs formed on bedrock and till boulder surfaces adjacent to the barnes ice cap bic central baffin island arctic canada act as unique archives of laurentide ice sheet basal conditions uranium series dating of these features reveals that carbonate precipitation from subglacial meltwater occurred during the last glacial maximum lgm requiring warm based ice in the region at that time however the preservation of fragile spccs is unlikely beneath erosive warm based ice suggesting that the transition to subsequent cold based conditions took place shortly after the lgm and glacial erosion in the region occurred dominantly prior to the lgm the oxygen isotopic composition of the meltwater from which the spccs precipitated is indistinguishable from that of the debris rich bic basal ice 18 o 24 referenced to vienna standard mean ocean water but distinct from that of the overlying white pleistocene ice 18 o 35 demonstrating that spccs are reliable archives of the isotopic composition of only the basal ice of past ice sheets

a multi proxy lacustrine record of holocene climate change on northeastern baffin island arctic canada reconstructions of past environmental changes are critical for understanding the natural variability of earth s climate system and for providing a context for present and future global change radiocarbon dated lake sediments from lake cf3 northeastern baffin island arctic canada are used to reconstruct past environmental conditions over the last 11 200 years numerous proxies including chironomid inferred july air temperatures diatom inferred lakewater ph and sediment organic matter reveal a pronounced holocene thermal maximum as much as 5 c warmer than historic summer temperatures from 10 000 to 8500 cal yr b p following rapid cooling 8500 cal yr b p lake cf3 proxies indicate cooling through the late holocene at many sites in northeastern canada the holocene thermal maximum occurred later than at lake cf3 this late onset of holocene warmth is generally attributed to the impacts of the decaying laurentide ice sheet on early holocene temperatures in northeastern canada however the lacustrine proxies in lake cf3 apparently responded to insolation driven warmth despite the proximity of lake cf3 to the laurentide ice sheet and its meltwater the magnitude and timing of the holocene thermal maximum at lake cf3 indicate that temperatures and environmental conditions at this site are highly sensitive to changes in radiative forcing

an ice marginal δ18o record from barnes ice cap baffin island canada barnes ice cap baffin island canada is a remnant of the laurentide ice sheet that separated from it about 8500 years ago owing to recession of the ice cap during the holocene pleistocene age i

accumulation storage and release of atmospheric mercury in a glaciated arctic catchment baffin island canada abstract part of the mercury hg entering arctic ecosystems is believed to be delivered from the atmosphere in snow but this source is difficult to quantify due to limited spatial coverage of hg data in snow here we evaluate the atmospheric deposition storage and release of total hg thg and monomethyl mercury mehg on penny ice cap baffin island this is the first such study in the baffin region thg levels in snow and firn mean 0 61 ng l 1 are comparable to those on high arctic glaciers but mehg levels are noticeably higher mean 0 11 ng l 1 we find little evidence of springtime enhancement of hg deposition in snow attributable to atmospheric mercury depletion events estimated accumulation rates of thg and mehg in firn are 0 33 and 0 03 g m 2 a 1 higher than on high arctic glaciers possibly due to higher precipitation on southern baffin island the estimated net annual release of thg by glacial snow and ice melt is small thg 1 86 kg mehg 0 18 kg in the study area geogenic hg contributions from sediment loaded glacial meltwater could be as large or larger than those from melting ice mehg levels are very low in meltwater fed streams and lakes 0 01 ng l 1 suggesting that mehg is released early in the snowmelt season and or quickly removed from meltwater by various processes summer melt and percolation on penny ice cap remobilise hg in firn after deposition and this imposes resolution limits of at least 3 years on depositional trends inferred from ice cores

lomonosovfonna and holtedahlfonna ice cores reveal east west disparities of the spitsbergen environment since ad 1700 an ice core extracted from holtedahlfonna ice cap western spitsbergen record spanning the period 1700 2005 was analyzed for major ions the leading empirical orthogonal function eof component is correlated with an index of summer melt log na mg 2 from 1850 and shows that almost 50 of the variance can be attributed to seasonal melting since the beginning of the industrial revolution the holtedahlfonna d 18 o value is less negative than in the more easterly lomonosovfonna ice core suggesting that moist air masses originate from a closer source most likely the greenland sea during the little ice age the lower methanesulfonic acid msa concentration and msa non sea salt sulfate fraction are consistent with the greenland sea as the main source for biogenic ions in the ice cores both the melt index and the msa fraction suggest that the early decades of the 18th century may have exhibited the coldest summers of the last 300 years in svalbard ammonium concentrations rise from 1880 which may result from the warming of the greenland sea or from zonal differences in atmospheric pollution transport over svalbard during winter neutralized aerosols are trapped within the tropospheric inversion layer which is usually weaker over open seas than over sea ice placing holtedahlfonna within the inversion more frequently than lomonosovfonna

holocene glaciation and climate evolution of baffin island arctic canada abstract lake sediment cores and cosmogenic exposure ce dates constrain the pattern of deglaciation and evolution of climate across baffin island since the last glacial maximum lgm ce dating of erratics demonstrates that the northeastern coastal lowlands became ice free ca 14 ka as the laurentide ice sheet lis receded from its lgm margin on the continental shelf coastal lakes in southeastern baffin island started to accumulate sediment at this time whereas initial lacustrine sedimentation was delayed by two millennia in the north reduced organic matter in lake sediment deposited during the younger dryas chron and the lack of a glacial readvance at that time suggest cold summers and reduced snowfall ice retreated rapidly after 11 ka but was interrupted by a widespread readvance of both the lis and local mountain glaciers 9 6 ka cockburn substage a second readvance occurred just before 8 ka during a period of unusually cold summers corresponding to the 8 2 ka cold event in the greenland ice sheet most local glaciers were behind their present margins before 7 ka and in some instances much earlier although the foxe dome of the lis continued to slowly retract toward the present day barnes ice cap throughout the holocene pollen in lake sediments is rare and dominated by exotic sources prior to 12 ka subsequently grass tundra became established followed by modern tundra vegetation ca 8 ka with subtle changes in pollen assemblages in the late holocene lake primary productivity peaked in the early holocene before terrestrial vegetation or marine surface waters reached their apparent thermal maxima lacustrine marine and glacial proxies all reflect significant late holocene cooling the onset of neoglaciation is well dated in lacustrine records at ca 6 ka with intensification after 2 5 ka the expansion of local glaciers during the little ice age represents the most extensive advance since 7 ka we suggest that the replacement of atlantic surface waters by cold low salinity arctic ocean water coupled with the steady reduction of summer insolation resulted in a significant positive sea ice feedback that produced a larger late holocene summer temperature depression over the baffin region than in the pacific sector of the arctic

mid to late holocene hydroclimatic and geochemical records from the varved sediments of east lake cape bounty canadian high arctic abstract a long sedimentary sequence from east lake cape bounty melville island 74 55 n 109 30 w contains a 4200 year long clastic varved record of paleohydrologic variations at high resolution sedimentary elemental geochemistry from micro x ray fluorescence xrf and sediment fabric variability reflect changes in sediment sources and lacustrine conditions through time the sedimentary environment progressed from marine in the mid holocene to estuarian from 2195 bc to 243 ad to fully lacustrine source after 244 ad correlation with local meteorological data indicates that varve thickness vt is positively correlated with snow depth on may 1st and negatively correlated with mean sept may temperatures our paleoclimatic reconstruction from vt series revealed high snow accumulation and warm sept may months before 1350 bc and a period of low snow accumulation and cold sept may between 1600 1900 ad that may correspond to the little ice age the general trends of vt series from cape bounty are in phase with the 18o series in agassiz ice cap and in anti phase with the vt series from lower murray lake in the northeastern of queen s elizabeth islands qei low mean arctic temperatures coincide with clusters of high sediment yield events at east nicolay and south sawtooth lakes especially during 1600 1750 ad and 1810 1910 ad the east lake record also exhibits the signature of the atlantic multidecadal oscillation amo for periods 600 850 ad 1400 1550 ad and 1750 1850 ad

high resolution multiproxy climatic records from ice cores tree rings corals and documentary sources using eigenvector techniques and maps assessment of recovered signal and errors palaeotemperature sensitive series from tree rings ice cores corals and documentary sources are combined to producepalaeo summer temperaturereconstructions ad 1970 1761 and geographical eigenvector eof maps in both hemispheres they are compared favourably to those of existing summer temperature average series there are 51 palaeoseries in the northern hemisphere mostly north of 40 n and 16 series in the southern hemisphere the statistics and significance of the palaeoreconstructions are examined by 1 finding the correlation coefficient palaeo to measured as a function of the number and geographical distribution of the palaeo series 2 developing and running a multiproxy model that generates pseudo series containing a signal and the same types and amounts of noise found in the various real palaeo series the model reproduces the measured correlation coefficients and the eigenvector s eof explained variances as functions of the number of sites about 77 of the signal variance can be reco

abrupt increase in greenland snow accumulation at the end of the younger dryas event the warming at the end of the last glaciation was characterized by a series of abrupt returns to glacial climate the best known of which is the younger dryas event1 despite much study of the causes of this event and the mechanisms by which it ended many questions remain unresolved1 oxygen isotope data from greenland ice cores2 4 suggest that the younger dryas ended abruptly over a period of about 50 years dust concentrations2 4 in these cores show an even more rapid transition 20 years this extremely short timescale places severe constraints on the mechanisms underlying the transition but dust concentrations can reflect subtle changes in atmospheric circulation which need not be associated with a large change in climate here we present results from a new greenland ice core gisp2 showing that snow accumulation doubled rapidly from the younger dryas event to the subsequent preboreal interval possibly in one to three years we also find that the accumulation rate change from the oldest dryas to the bo11ing allerod warm period was large and abrupt the extreme rapidity of these changes in a variable that directly represents regional climate implies that the events at the end of the last glaciation may have been responses to some kind of threshold or trigger in the north atlantic climate system

die altpleistozanen terrassen der mittelmosel uberlegungen zur horizontalkonstanz der terrassen der rheinischen hochscholle summary revision of the old pleistocene river terraces in the middel moselle area verified the results of kremer 1954 refuting the objections by birkenhauer 1971 corresponding to the findings in the middle rhine area bibus semmel 1977 five sometimes six pleistocene river terraces which show neither tectonic dislocations nor a distinct longitudinal gradient can be traced above the narrow moselle valley differences in the altitude of equivalent terraces of the middle moselle area e g t4 265 m nn and the middle rhine area tr4 220 m nn and the almost rectangular course of the both rivers indicates that the explanation for the missing gradient bibus and semmel 1977 birkenhauer 1979 cannot only be found by a stronger postsedimentary uplift in the northern area of the rhenish shield

holocene climate change in arctic canada and greenland abstract this synthesis paper summarizes published proxy climate evidence showing the spatial and temporal pattern of climate change through the holocene in arctic canada and greenland our synthesis includes 47 records from a recently published database of highly resolved holocene paleoclimate time series from the arctic sundqvist et al 2014 we analyze the temperature histories represented by the database and compare them with paleoclimate and environmental information from 54 additional published records mostly from datasets that did not fit the selection criteria for the arctic holocene database combined we review evidence from a variety of proxy archives including glaciers ice cores and glacial geomorphology lake sediments peat sequences and coastal and deep marine sediments the temperature sensitive records indicate more consistent and earlier holocene warmth in the north and east and a more diffuse and later holocene thermal maximum in the south and west principal components analysis reveals two dominant holocene trends one with early holocene warmth followed by cooling in the middle holocene the other with a broader period of warmth in the middle holocene followed by cooling in the late holocene the temperature decrease from the warmest to the coolest portions of the holocene is 3 0 1 0 c on average n 11 sites the greenland ice sheet retracted to its minimum extent between 5 and 3 ka consistent with many sites from around greenland depicting a switch from warm to cool conditions around that time the spatial pattern of temperature change through the holocene was likely driven by the decrease in northern latitude summer insolation through the holocene the varied influence of waning ice sheets in the early holocene and the variable influx of atlantic water into the study region

detrital zircon u pb insights into the timing and provenance of the south pyrenean jaca basin we investigate how sedimentary systems respond to tectonic uplift during the last stages of infilling of a foreland basin massive conglomeratic deposits characterize the last stage of basin fill in the jaca basin the western portion of the south pyrenean foreland we conduct detrital zircon u pb geochronology in a 3000 m thick cenozoic section containing the transition from deltaic to alluvial environments with the aim of reconstructing changes of provenance in this key stage of evolution of the basin the last conglomeratic deposits of the basin belong to the san juan de la pena alluvial fan which has previously been assigned an early oligocene age our results show the presence of earliest miocene detrital zircons at the base of the fan zircon double dating reveals identical u pb and u th he ages which is indicative of a volcanic origin for these zircons we therefore conclude that this fan was deposited during early miocene times our data establish a new chronological framework for deformation and sedimentation in the south pyrenean foreland with strong implications for the dynamics and palaeogeography governing the last episodes of basin fill our results support synchronous sedimentation in the jaca piggy back basin and in the autochthonous ebro basin during the last stages of pyrenean compression in the miocene this work emphasizes the tectonic controls on the configuration of the drainage basin and gives insights into the evolution of the drainage network in internally drained basins supplementary material s1 extended zircon u pb la icp ms methodology s2 reduced detrital zircon u pb dataset for all analysis s3 all age spectra s4 zhe data s5 sample location for the analyzed samples are available at https doi org 10 6084 m9 figshare c 4507073

out of the woods driftwood insights into holocene pan arctic sea ice dynamics the collation of 913 driftwood samples from across the western arctic with spatiotemporal distribution and available provenance data enabled the production of a high resolution proxy based reconstruction of holocene arctic ocean surface current and sea ice dynamics regionally bounded driftwood based sea ice reconstructions studies suggest spatiotemporally complex past arctic sea ice extent and movement however a large scale compilation of holocene arctic driftwood has not previously been developed sparse driftwood in the early holocene 8 2 cal ka b p deglacial period was followed by increased driftwood deposition in the warmer mid holocene 8 2 4 2 cal ka b p characterized by an enhanced transpolar drift tpd 7 cal ka b p leading to sea ice loss through the fram strait driftwood incursion peaks show spatial e w progression from the eurasian archipelagos to greenland and the canadian arctic archipelago suggesting a progressive shift in the orientation of the tpd on centennial millennial time scales and intermediate phases in the arctic oscillation late holocene cooling 4 2 cal ka b p is indicated by increased influx of probably north american picea via a strengthened beaufort gyre bg which enhanced sea ice recirculation starting in the western arctic and progressing eastward in recent millennia 2 cal ka b p a more variable driftwood record alternates between bg and tpd dominance on centennial time scales to further constrain a spatiotemporal reconstruction of variations in holocene ocean current and sea ice dynamics a more definitive determination of driftwood provenance is recommended to build upon the current framework such as through radiogenic isotope tracing and adna analysis

latest pleistocene and holocene glaciation of baffin island arctic canada key patterns and chronologies abstract melting glaciers and ice caps on baffin island contribute roughly half of the sea level rise from all ice in arctic canada although they comprise only one fourth of the total ice in the region the uncertain future response of arctic glaciers and ice caps to climate change motivates the use of paleodata to evaluate the sensitivity of glaciers to past warm intervals and to constrain mechanisms that drive glacier change we review the key patterns and chronologies of latest pleistocene and holocene glaciation on baffin island the deglaciation by the laurentide ice sheet occurred generally slowly and steadily throughout the holocene to its present margin barnes ice cap except for two periods of rapid retreat an early interval 12 to 10 ka when outlet glaciers retreated rapidly through deep fiords and sounds and a later interval 7 ka when ice over foxe basin collapsed in coastal settings alpine glaciers were smaller during the younger dryas period than during the little ice age at least some alpine glaciers apparently survived the early holocene thermal maximum which was several degrees warmer than today although data on glacier extent during the early holocene is extremely sparse following the early holocene thermal maximum glaciers advanced during neoglaciation beginning in some places as early as 6 ka although most sites do not record near little ice age positions until 3 5 to 2 5 ka alpine glaciers reached their largest holocene extents during the little ice age when temperatures were 1 1 5 c cooler than during the late 20th century synchronous advances across baffin island throughout neoglaciation indicate sub milankovitch controls on glaciation that could involve major volcanic eruptions and solar variability future work should further elucidate the state of glaciers and ice caps during the early holocene thermal maximum and glacier response to climate forcing mechanisms

penny ice cap cores baffin island canada and the wisconsinan foxe dome connection two states of hudson bay ice cover ice cores from penny ice cap baffin island canada provide continuous holocene records of oxygen isotopic composition 18 o proxy for temperature and atmospheric impurities a time scale was established with the use of altered seasonal variations some volcanic horizons and the age for the end of the wisconsin ice age determined from the grip and gisp2 ice cores there is pre holocene ice near the bed the change in 18 o since the last glacial maximum lgm is at least 12 5 per mil compared with an expected value of 7 per mil suggesting that lgm ice originated at the much higher elevations of the then existing foxe dome and foxe ridge of the laurentide ice sheet the lgm 18 o values suggest thick ice frozen to the bed of hudson bay

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

historical variations of mercury stable isotope ratios in arctic glacier firn and ice cores the concentration and isotopic composition of mercury hg were determined in glacier core samples from canadian arctic ice caps dating from pre industrial to recent time early 21st century mean hg levels increased from 0 2 ng l 1 in pre industrial time to 0 8 1 2 ng l 1 in the modern industrial era last 200 years hg accumulated on arctic ice caps has 199hg and 201hg that are higher 1 to 2 9 than previously reported for arctic snow mostly 1 impacted by atmospheric hg depletion events suggesting that these events contribute little to hg accumulation on ice caps the range of 202hg 199hg and 201hg in glacier cores overlaps with that of arctic hg0 g and of seawater in baffin bay but also with that of mid latitude precipitation and industrial hg sources including coal and hg ores a core from agassiz ice cap 80 7 n shows a 1 shift in 202hg over the 19th 20th centuries that could reflect changes in the isotopic composition of the atmospheric hg pool in the high arctic in response to growing industrial emissions at lower latitudes this study is the first ever to report on historical variations of hg stable isotope ratios in arctic ice cores results could help constrain future modeling efforts of the global hg biogeochemical cycle and the atmosphere s response to changing hg emissions past and future

a 2000 yr long multi proxy lacustrine record from eastern baffin island arctic canada reveals first millennium ad cold period abstract we generate a multi proxy sub centennial scale reconstruction of environmental change during the past two millennia from itilliq lake baffin island arctic canada our reconstruction arises from a finely subsectioned 210pb and 14c dated surface sediment core and includes measures of organic matter e g chlorophyll a carbon nitrogen ratio and insect diptera chironomidae assemblages within the past millennium the least productive and by inference coldest conditions occurred ca ad 1700 1850 late in the little ice age the 2000 yr sediment record also reveals an episode of reduced organic matter deposition during the 6th 7th century ad combined with the few other records comparable in resolution that span this time interval from baffin island we suggest that this cold episode was experienced regionally a comparable cold climatic episode occurred in alaska and western canada at this time suggesting that the first millennium ad cold climate anomaly may have occurred throughout the arctic dramatic increases in aquatic biological productivity at multiple trophic levels are indicated by increased chlorophyll a concentrations since ad 1800 and chironomid concentrations since ad 1900 both of which have risen to levels unprecedented over the past 2000 yr

new magnetostratigraphic dating of the palaeogene syntectonic sediments of the west central pyrenees tectonostratigraphic implications financial support to develop this investigation was provided by projects cgl2009 08969 cgl2010 21968 c02 02 cgl2009 14214 cgl2010 17479 and cgl2014 55900 p of the former spanish ministry of science and innovation micinn

holocene alpine glaciation inferred from lacustrine sediments on northeastern baffin island arctic canada with accelerated melting of alpine glaciers understanding the future state of the cryosphere is critical because the observational record of glacier response to climate change is short palaeo records of glacier change are needed using proglacial lake sediments which contain continuousanddatablerecordsofpastglacieractivity weinvestigateholoceneglacierfluctuationson northeastern baffin island basal radiocarbon ages from three lakes constrain laurentide ice sheet retreat by ca 10 5ka high sedimentation rates 0 03cma 1 and continuous minerogenic sedimen tation throughout the holocene in proglacial lakes in contrast to organic rich sediments and low sedimentation rates 0 005cma 1 in neighbouring non glacial lakes suggest that glaciers may have persisted in proglacial lake catchments since regional deglaciation the presence of varves and relatively high magnetic susceptibility from 10 to 6ka and since 2ka in one proglacial lake suggest minimum holocene glacier extent ca 6 2ka moraine evidence and proglacial and threshold lake sediments indicate that the maximum holocene glacier extent occurred during the little ice age the finding that glaciers likely persisted through the holocene is surprising given that regional proxy records reveal summer temperatures several degrees warmer than today and may be due to shorter ablation seasons and greater accumulation season precipitation copyright 2009 john wiley sons ltd

evolution of a turbiditic foreland basin and analogy with an accretionary prism example of the eocene south pyrenean basin the south pyrenean tertiary basin was an east west trending foreland trough which developed from early eocene to miocene times in a north south trending compressive regime a turbiditic series of lower and middle eocene age hecho group enables us to define the typical features of the tectono sedimentary evolution of the basin 1 slope and shelf derived carbonate turbidites and megaturbidites bear witness to the seismic activity of the basin borders 2 the southern basin border evidenced by the onlap of the turbidites onto slope and shelf deposits migrated progressively southwards in time and 3 the deformation pattern is characterized in the meso cenozoic sediments by a complex thrust fold system of thin skinned tectonics style its specific geometry and kinematics were influenced by the pre deformation geometry onlap this thrust fold system is related to south directed basement nappes and its front advanced progressively southwards in time from this data we infer an evolutionary model for this highly mobile basin it was a flexural basin linked to the northward bending of the lithosphere in the foreland of a south directed crustal accretionary prism as the nappes advanced the basin migrated progressively southwards in the foreland direction as for the actual basin evolution many analogies with accretionary prism trench systems of active margins exist

cosmogenic 10be and 26al ages for the last glacial maximum eastern baffin island arctic canada a chronology for the last glacial maximum based on cosmogenic exposure dating in the pangnirtung fjord area eastern baffin island arctic canada is at odds with many decades of land based glacial stratigraphic research most previous chronologies focused primarily on relative weathering criteria and suggested that ice extent was restricted during the late wisconsinan ca 24 8 ka in contrast by directly dating glacial features we conclude that late wisconsinan ice was far more extensive than previously believed there are 36 gneissic boulders and 8 samples of ice molded gneissic bedrock that yield late wisconsinan 10 be and 26 al exposure ages for the last glaciation of pangnirtung fjord the prominent duval moraines which were previously interpreted to represent a significant early wisconsinan 100 60 ka ice advance on southern cumberland peninsula were actually deposited between 24 and 9 ka two boulders from a raised glaciomarine delta stratigraphically related to the duval moraines date to about 10 ka two recessional moraines and striated bedrock along pangnirtung fjord as well as erratics on the floor of the kolik river valley a tributary to pangnirtung fjord indicate that deglaciation began between 12 and 9 ka in situ produced 10 be and 26 al abundances indicate that ice filled pangnirtung fjord for about 15 k y either continuously or intermittently prior to 10 ka which is compatible with 14 c chronologies for adjacent cumberland sound thus our data support other recent studies that suggest the northern and southern margins of the laurentide ice sheet were generally in phase during the latest wisconsinan contrary to earlier interpretations

postglacial environmental succession of nettilling lake baffin island canadian arctic inferred from biogeochemical and microfossil proxies abstract nettilling lake baffin island nunavut is currently the largest lake in the canadian arctic archipelago despite its enormous size this freshwater system remains little studied until the present day existing records from southern baffin island indicate that in the early postglacial period the region was submerged by the postglacial tyrell sea due to isostatic depression previously exerted by the laurentide ice sheet however these records are temporally and spatially discontinuous relying on qualitative extrapolation this paper presents the first quantitative reconstruction of the postglacial environmental succession of the nettilling lake basin based on a 8300 yr long high resolution sedimentary record our multi proxy investigation of the glacio isostatic uplift and subsequent changes in paleosalinity and sediment sources is based on analyses of sediment fabric elemental geochemistry xrf diatom assemblage composition as well as on the first diatom based oxygen isotope record from the eastern canadian arctic results indicate that the nettilling lake basin experienced a relatively rapid and uniform marine invasion in the early holocene followed by progressive freshening until about 6000 yr bp when limnological conditions similar to those of today were established our findings present evidence for deglacial processes in the foxe basin that were initiated at least 400yrs earlier than previously thought

the effects of flowline length evolution on chemistry δ18o profiles from penny ice cap baffin island canada the isotopic and chemical signatures for ice age and holocene ice from summit greenland and penny ice cap baffin island canada are compared the usual pattern of low 180 high ca2 and high cl is presented in the summit records but penny ice cap has lower than present cl in its ice age ice a simple extension of the hansson model hansson 1994 is developed and used to simulate these signatures the low ice age cl from penny ice cap is explained by having the ice age ice originating many thou sands of km inland near the centre of the laurentide ice sheet and much further from the marine sources summit s flowlines all start close to the present site the penny ice cap early holocene 180 s had to be corrected to offset the laurentide meltwater distortion the analysis suggests that presently the summit and penny ice cap marine impurity ori ginates about 500 km away and that presently penny ice cap receives a significant amountoflocal continental impurity

recycling an uplifted early foreland basin fill an example from the jaca basin southern pyrenees spain in the northern jaca basin southern pyrenees the replacement of deep marine by terrestrial environments during the eocene records a main drainage reorganization in the active pyrenean pro wedge which leads to recycling of earlier foreland basin sediments the onset of late eocene oligocene terrestrial sedimentation is represented by four main alluvial fans santa orosia cancias pena oroel and san juan de la pena which appear diachronously from east to west these alluvial fans are the youngest preserved sediments deposited in the basin we provide new data on sediment composition and sources for the late eocene oligocene alluvial fans and precursor deltas of the jaca basin sandstone petrography allows identification of the interplay of axially fed sediments from the east with transversely fed sediments from the north compositional data for the alluvial fans reflects a dominating proportion of recycled rock fragments derived from the erosion of a lower to middle eocene flysch depocentre the hecho group located immediately to the north in addition pebble composition allows identification of a source in the north pyrenean zone that provided lithologies from the cretaceous carbonate flysch jurassic dolostones and triassic dolerites thus we infer this zone as part of the source area located in the headwaters which would have been unroofed from turbidite deposits during the late eocene oligocene these conclusions provide new insights on the response of drainage networks to uplift and topographic growth of the pyrenees where the water divide migrated southwards to its present day location

punctuated thrust deformation in the context of doubly vergent thrust wedges implications for the localization of uplift and exhumation understanding uplift and exhumation in orogenesis requires integrating the effects of both climatic and tectonic forcing punctuated thrust activity is widely documented from field studies in a range of mountain belts the potential for climatic forcing of thrust activity has been a subject of recent debate here we use a modeling approach to analyze the behavior of individual thrust units in the context of asymmetric doubly vergent thrust wedges the model predicts that rates of surface uplift frontal accretion and exhumation should be punctuated on a time scale linked to thrust sheet geometry and convergence rates this time scale ranges from 0 1 to 5 m y for various settings and should be calculated before external forcings such as climate are invoked

wisconsin and holocene δ18o variations barnes ice cap canada new 18o measurements on ice samples from barnes ice cap show a relatively large shift from about 23 in the blue ice that makes up the bulk of the ice cap to 38 in a basal layer of clean white ice this strongly suggests that the latter is of pleistocene age thus confirming an earlier interpretation based on less comprehensive data the shift between the pleistocene and holocene ice is attributed in part to the change in climate at the end of the pleistocene and in part to a decrease in elevation of the accumulation area of 700 m beneath the clean white ice there is a layer of dirty white ice with less negative 18o values this ice is believed to have been deposited during a climatically warm period in early to middle wisconsin time in addition however the less negative 18o values in it are in part attributed to fractionation at a time in the past when the basal ice was at the melting point and some of the water produced by pressure melting was lost through a permeable bed

the qs problem sediment volumetric balance of proximal foreland basin systems although the stratigraphy of sedimentary basins depends on the balance between the magnitude and grain size characteristics of the sediment supply qs and the spatial distribution of tectonic subsidence generating accommodation x qs is problematical to measure in present day sediment routing systems and formidably difficult to predict in their ancient counterparts this challenge was tackled by treating the sediment discharge from the outlet of mountain catchments as the result of incision by a drainage network with a bulk diffusivity based on the length over which the mean annual rainfall is concentrated the size relief and slope of palaeo catchments acting as feeders for sediment routing systems are used to run simulations of sediment discharge and bulk diffusivity for a range of annual precipitation values a wide range of observable geological phenomena can be used to converge on the most likely solutions for qs including depositional volumes in the basin and bedrock thermochronology and detrital cosmogenic nuclide dating to constrain catchment erosion rates modelled sediment discharges can be checked with estimates derived from global regressions the sediment efflux of mountain catchments serves as a boundary condition for down system sediment transport and deposition variations in the volumetric ratio of sediment supply to available accommodation qs x determines patterns of transverse versus longitudinal axial sediment dispersal the volumetric ratio may change as a result of variations in climatic parameters tectonic uplift rate and catchment expansion an abrupt climate change to higher precipitation values promotes higher qs x but transient landscape response causes a return to values close to the baseline generating a distinctive down system extension of a gravel spike catchment expansion has a similar but more prolonged effect on gravel progradation in contrast a change in tectonic forcing such as an increase in slip rate on a border fault causes little change in qs x because increased subsidence compensates for the increased sediment supply studies of mid eocene oligocene sediment routing systems in the south central pyrenees allow the discrimination of different types of proximal wedge top sedimentary systems on the basis of the volumetric ratio of qs to accommodation x i small steep local fan systems in tectonically ponded underfilled basins supplied by low sediment discharges ii tectonically guided long range axial systems fed by large sediment discharges from widely spaced palaeovalleys and iii large shallow sloping transverse megafans burying underlying defunct or active tectonic structures supplied by high to very high sediment discharges understanding the role of variations in qs helps to explain the syntectonic evolution of proximal foreland basin systems the oligocene miocene north alpine foreland basin switzerland is qualitatively identified as a high qs example the miocene recent northern apennines of italy as a low qs example and the eocene oligocene southern pyrenees of spain as intermediate in character

frozen bed fennoscandian and laurentide ice sheets during the last glacial maximum the areal extents of the laurentide and fennoscandian ice sheets during the last glacial maximum about 20 000 years ago are well known1 but thickness estimates range widely from high domed2 to thin3 with large implications for our reconstruction of the climate system regarding for example northern hemisphere atmospheric circulation and global sea levels this uncertainty stems from difficulties in determining the basal temperatures of the ice sheets and the shear strength of subglacial materials4 a knowledge of which would better constrain reconstructions of ice sheet thickness here we show that in the absence of direct data the occurrence of ribbed moraines in modern landscapes can be used to determine the former spatial distribution of frozen and thawed bed conditions we argue that ribbed moraines were formed by brittle fracture of subglacial sediments induced by the excessive stress at the boundary between frozen and thawed bed conditions resulting from the across boundary difference in basal ice velocity maps of glacial landforms from aerial photographs of canada and scandinavia reveal a concentration of ribbed moraines around the ice sheet retreat centres of quebec keewatin newfoundland and west central fennoscandia together with the evidence from relict landscapes that mark glacial areas with frozen bed conditions the distribution of ribbed moraines on both continents suggest that a large area of the laurentide and fennoscandian ice sheets was frozen based and therefore high domed and stable during the last glacial maximum

glacial inception on baffin island the role of insolation meteorology and topography abstractgeologic evidence suggests that the last glacial inception 115 kya occurred within the mountains of baffin island global climate models gcms have difficulty simulating this climate transition likely because of their coarse horizontal resolution that smooths topography and necessitates the use of cumulus parameterizations a regional configuration of the weather research and forecasting wrf model is used to simulate the small scale topographic and cloud processes neglected by gcms and the sensitivity of the region to milankovitch forcing topography and meteorology is tested it is found that ice growth is possible with 115 kya insolation realistic topography and slightly colder than average meteorology represented by specific years within the past three decades the simulation with low gcm like topography shows a negative surface mass balance even with the relevant orbital parameter configuration demonstrating the criticality of realistic topography the downslope growth of the ice

tectono thermal history of an exhumed thrust sheet top basin an example from the south pyrenean thrust belt this paper presents a new balanced structural cross section of the jaca thrust sheet top basin of the southern pyrenees combined with paleo thermometry and apatite fission track aft thermochronology data the cross section based on field data and interpretation of industrial seismic reflection profiles allows refinement of previous interpretations of the south directed thrust system involving the identification of new thrust faults and of the kinematic relationships between basement and cover thrusts from the middle eocene to the early miocene aft analysis shows a southward decrease in the level of fission track resetting from totally reset paleozoic rocks and lower eocene turbidites indicative of heating to tmax 120 c to partially reset middle eocene turbidites and no very weak resetting in the upper eocene lower oligocene molasse tmax 60 c aft results indicate a late oligocene early miocene cooling event throughout the axial zone and jaca basin paleo maximum temperatures determined by vitrinite reflectance measurements and raman spectroscopy of carbonaceous material reach up to 240 c at the base of the turbidite succession inverse modelling of aft and vitrinite reflectance data with the qtqt software for key samples show compatibility between vitrinite derived tmax and the aft reset level for most of the samples however they also suggest that the highest temperatures determined in the lowermost turbidites correspond to a thermal anomaly rather than burial heating possibly due to fluid circulation during thrust activity from these results we propose a new sequential restoration of the south pyrenean thrust system propagation and related basin evolution

record of volcanism since 7000 b c from the gisp2 greenland ice core and implications for the volcano climate system sulfate concentrations from continuous biyearly sampling of the gisp2 greenland ice core provide a record of potential climate forcing volcanism since 7000 b c although 85 percent of the events recorded over the last 2000 years were matched to documented volcanic eruptions only about 30 percent of the events from 1 to 7000 b c were matched to such events several historic eruptions may have been greater sulfur producers than previously thought there are three times as many events from 5000 to 7000 b c as over the last two millennia with sulfate deposition equal to or up to five times that of the largest known historical eruptions this increased volcanism in the early holocene may have contributed to climatic cooling

dating the northern deposits of the ebro foreland basin implications for the kinematics of the sw pyrenean front abstract dating the sedimentary infill of the northern margin of the ebro foreland basin informs about the orogen basin evolution a magnetostratigraphic section of 5 km thick combines new magnetostratigraphic results from the syntectonic alluvial uncastillo fm upper oligocene lower miocene 1 km thick the fuencalderas section with previous 3 3 km thick and new 0 7 km thick magnetostratigraphic data from the underlying fluvial campodarbe fm luesia and san marzal sections eocene oligocene this composite section allows dating the entire basin infill in this sector therefore bracketing the timing of the deformation in the southern margin of the pyrenees after considering previous kinematic studies deformation recorded by the continental deposits spans from syn gavarnie nappe activity broto and fiscal basement thrust sheets from 31 3 to 24 55 ma rupelian chattian oligocene to the syn guarga thrust activity from 24 55 to 21 2 ma chattian aquitanian oligocene miocene the accumulation rates vary from ca 22 to ca 39 cm kyr between the genetic stratigraphic units in the uncastillo fm through the section these rates are close to those of the underlying deposits of the campodarbe fm average of ca 36 cm kyr deformation for the latest pyrenean front syn guarga thrust is younger than previously assigned in 5 4 1 5 and 1 1 myr of the beginning of the punta comun thrust sheet from 29 4 ma to 24 ma lower riglos thrust sheet system from 24 to 22 5 ma and the upper riglos thrust system 22 5 to 21 4 ma respectively other significant changes in accumulation rate and its derivative also indicate variations in the tectonic activity ca 33 and 28 ma

the anso transect of the southern pyrenees basement and cover thrust geometries a balanced geological section through the western central pyrenees allows the alpine geometry of hercynian basement to be determined this shows marked differences with other transects of the southern part of the chain basement involved thrust sheets do not form an antiformal stack but are imbricated and define steps separated by frontal culmination limbs basement thrusts propagate upwards and have formed distinct thrust systems in the cover in this transect the north pyrenean zone is bounded to the south by gently dipping thrusts of large displacement and the axial zone massif at its western termination area is a flat topped culmination caused by a single thrust fault the gavarnie thrust this thrust emerges to the south in the interior of the syntectonic jaca basin the geometry of which is also controlled by underlying basement thrusts various generations of structures can be correlated with distinct episodes of syntectonic sedimentation a sequential restoration of the section illustrates how successive foreland sedimentary wedges were generated and progressively involved in deformation tectonic shortening is 48 km almost half of that estimated further to the east for the southern pyrenees the structure deduced at the ecors pyrenees seismic section cannot be translated to this transect

on the special rheological properties of ancient microparticle laden northern hemisphere ice as derived from bore hole and core measurements on observe des differences dans le fluage des glaces a forte concentration en microparticules wisconsin recent qui sont plus douces que celles de la glace contemporaine ou holocene on analyse les parametres suivants concentration ou microparticules 18 o taille des cristaux axe c ca na conductivite et densite dans des carottes prelevees a agassiz iles ellesmere sur l ile devon et au groenland

temporal aspects of genetic stratigraphic units in continental sedimentary basins examples from the ebro basin spain abstract the utility of genetic stratigraphy lies with the fundamental relationship between genetic stratigraphic units and correlative intervals of geologic time while high resolution studies may reveal varying degrees of diachroneity that are associated with their bounding surfaces genetic stratigraphic units are generally viewed as chronostratigraphic in nature representing specific periods of basin fill despite the vast literature on basin analysis an evaluation of the temporal character of the boundaries between genetic stratigraphic units particularly in cases where they are conformable has not yet been undertaken the cenozoic ebro basin is a foreland basin on the north eastern iberian peninsula that provides a case for assessing the temporal character of the boundaries between genetic stratigraphic units these units are termed tecto sedimentary units following the method of tecto sedimentary analysis that is used in some continental basins in the ebro basin tecto sedimentary analysis is based on direct field observations in this work magnetostratigraphic data from four tecto sedimentary units units t4 to t7 that span rocks of lower and middle miocene age ca 1000 m thick in the central and western areas of the basin are analysed the study area contains alluvial fluvial and lacustrine deposits that were sourced from pyrenean and iberian areas whose catchments were structured during the collision of iberia and eurasia new magnetostratigraphic data from this study and previously published magnetostratigraphic data enable us to determine the ages of these tecto sedimentary unit boundaries throughout a 200 km long east west transect that extends from the basin centre to the southwestern margin the results indicate that the diachrony of the three boundaries between the miocene tecto sedimentary units through the central ebro basin is less than 0 3 ma where they are conformable this low degree of diachroneity may be attributed to the effects of allogenic largely tectonic processes that operate in the catchment areas and methodological inaccuracies these results provide empirical support to the idea that genetic stratigraphic units are bounded by surfaces that exhibit low amounts of diachroneity where they are conformities

monsoon hydrography and productivity changes in the east china sea during the past 100 000 years okinawa trough evidence md012404 1 we analyzed the high resolution foraminifer isotope records total organic carbon toc and opal content from an okinawa trough core md012404 in order to estimate the monsoon hydrography and productivity changes in the east china sea ecs of the tropical western pacific over the past 100 000 years the variability shown in the records on orbital time scales indicates that high toc intervals coincide with the increases of boreal may september insolation driven by precession cycles 21 ka implying a strong connection to the variations in monsoons we also observed possibly nearly synchronous millennial scale changes of the ecs surface hydrography mainly driven by salinity changes but also by temperature effects and productivity coincident with monsoon events in the hulu dongge stalagmite isotope records we found that increased freshening and high productivity correlate with high monsoon intensity in interstadials this study suggests that the millennial scale changes in monsoon hydrography and productivity in the ecs are remarkable and persistent features over the past 100 000 years

palaeoenvironmental history of the last six centuries in the nettilling lake area baffin island canada a multi proxy analysis the baffin island region in the eastern canadian arctic has recently experienced a rapid warming possibly unprecedented in millennia to investigate theresponse of freshwater environments to this warming and place it in a secular perspective we analyzed a 90 cm long sediment core from nettilling lake the largest lake of the canadian arctic archipelago the core was taken from a part of the lake basin that receives meltwater and sediment inputs from thenearby penny ice cap the core time scale established using 137cs and palaeomagnetic techniques spans an estimated 600 years a multi proxy approachwas used to document changes in the physical chemical and biological properties of the sediments we found evidence for a relatively warm period mid late 15th century to mid late 16th century during the early part of the little ice age lia characterized by high sedimentation rates and laminations this was followed by colder drier and windier conditions corresponding to the coldest phase of lia and coinciding with the latest and most extensiveperiod of regional ice cap expansion early 16th to late 19th centuries a rapid warming occurred at the beginning of the 20th century variations intitanium ti content in the core a proxy for detrital sediment inputs showed good agreement with reconstructed secular variations in summer meltrates on penny ice cap between the mid 14th century and the present day providing supporting evidence for a climatic hydrological connection betweenthe ice cap and nettilling lake

using high resolution tritium profiles to quantify the effects of melt on two spitsbergen ice cores ice cores from small ice caps provide valuable climatic information additional to that of greenland and antarctica however their integrity is usually compromised by summer meltwater percolation

origin age and paleoenvironmental significance of carbonate precipitates from a granitic environment akshayuk pass southern baffin island canada this study documents the discovery of calcite crusts on the upper surface of clasts within morainic complexes in akshayuk pass southern cumberland peninsula baffin island a region underlain by granitic and gneissic rocks of the precambrian canadian shield strontium isotope ratios 87 sr 86 sr indicate that the major source of calcium is derived from the local dissolution of fracture filling calcite and a minor source is derived from silicate weathering the calcite crusts have 13 c values between 1 6 and 12 0 and 18 o values in the 13 0 and 7 9 range these values are highly enriched over the predicted isotopic values based on the 13 cdic and 18 o of the local water and temperature at which calcite precipitation occurred the isotopic enrichments are attributed to a combination of both equilibrium and kinetic evaporation and were verified experimentally the series of evaporative experiments indicate that kinetic evapo ration produces a far from equilibrium isotope effect on both the 13 c and 18 o composition of the precipitating calcite 13 ckie caco3 co2 between 20 2 and 40 5 vpdb 18 okie averaging 34 9 3 7 vsmow based on these re sults the formation of the calcite crusts is ascribed to the evaporation of stagnating ephemeral lakes and streams fol lowing the retreat of valley glaciers given the 1500 m difference in heights between the highland and the valley the katabatic winds originating from the penny ice cap can act as a catalyst to increase the rate of evaporation in ad dition radiocarbon dating of ten of these crusts yielded holocene ages 7640 cal calibrated bp to modern these re sults suggest that the maximum expansion of holocene valley glacier in akshayuk pass previously thought to have occurred during the little ice age is probably much older

timing of the most recent neoglacial advance and retreat in the south shetland islands antarctic peninsula insights from raised beaches and holocene uplift rates abstract the timing of the most recent neoglacial advance in the antarctic peninsula is important for establishing global climate teleconnections and providing important post glacial rebound corrections to gravity based satellite measurements of ice loss however obtaining accurate ages from terrestrial geomorphic and sedimentary indicators of the most recent neoglacial advance in antarctica has been hampered by the lack of historical records and the difficulty of dating materials in antarctica here we use a new approach to dating flights of raised beaches in the south shetland islands of the northern antarctic peninsula to bracket the age of a neoglacial advance that occurred between 1500 and 1700 ad broadly synchronous with compilations for the timing of the little ice age in the northern hemisphere our approach is based on optically stimulated luminescence of the underside of buried cobbles to obtain the age of beaches previously shown to have been deposited immediately inside and outside the moraines of the most recent neoglacial advance in addition these beaches mark the timing of an apparent change in the rate of isostatic rebound thought to be in response to the same glacial advance within the south shetland islands we use a maxwell viscoelastic model of glacial isostatic adjustment gia to determine whether the rates of uplift calculated from the raised beaches are realistic given the limited constraints on the ice advance during this most recent neoglacial advance our rebound model suggests that the subsequent melting of an additional 16 22 increase in the volume of ice within the south shetland islands would result in a subsequent uplift rate of 12 5 mm yr that lasted until 1840 ad resulting in a cumulative uplift of 2 5 m this uplift rate and magnitude are in close agreement with observed rates and magnitudes calculated from the raised beaches since the most recent neoglacial advance along the south shetland islands and falls within the range of uplift rates from similar settings such as alaska

holocene thermal maximum in the western arctic 0 180 w the spatio temporal pattern of peak holocene warmth holocene thermal maximum htm is traced over 140 sites across the western hemisphere of the arctic 0 180 w north of 60 n paleoclimate inferences based on a wide variety of proxy indicators provide clear evidence for warmer than present conditions at 120 of these sites at the 16 terrestrial sites where quantitative estimates have been obtained local htm temperatures primarily summer estimates were on average 1 6 0 8 c higher than present approximate average of the 20th century but the warming was time transgressive across the western arctic as the precession driven summer insolation anomaly peaked 12 10 ka thousands of calendar years ago warming was concentrated in northwest north america while cool conditions lingered in the northeast alaska and northwest canada experienced the htm between ca 11 and 9 ka about 4000 yr prior to the htm in northeast canada the delayed warming in quebec and labrador was linked to the residual laurentide ice sheet which chilled the region through its impact on surface energy balance and ocean circulation the lingering ice also attests to the inherent asymmetry of atmospheric and oceanic circulation that predisposes the region to glaciation and modulates the pattern of climatic change the spatial asymmetry of warming during the htm resembles the pattern of warming observed in the arctic over the last several decades although the two warmings are described at different temporal scales and the htm was additionally affected by the residual laurentide ice the similarities suggest there might be a preferred mode of variability in the atmospheric circulation that generates a recurrent pattern of warming under positive radiative forcing unlike the htm however future warming will not be counterbalanced by the cooling effect of a residual north american ice sheet

environmental setting micro morphologies and stable c o isotope composition of cold climate carbonate precipitates a review and evaluation of their potential as paleoclimatic proxies abstract given the growing interest in carbonate deposits from polar regions as paleoclimatic proxies this review paper first provides a classification of the various types of cold climate carbonate precipitates followed by a summary of the 13 c and 18 o composition of the carbonate deposits and parent water from which the carbonates precipitated the cold climate carbonate precipitates were classified into three broad categories powders crusts and speleothem the carbonate powders include those that precipitated in relation to aufeis aggradation cryogenic aufeis calcite and in relation to the growth of various annual perennial ice formations in freezing caves cryptocrystalline calcite and calcite pearls the carbonate crusts can be further subdivided based on their lithic environment those that precipitated on the upper surface of bedrock clasts i e subglacially precipitated calcite and evaporative calcite crusts those that are located on the underside of clasts i e pedogenic carbonates and those that precipitated in rock outcrop fissures i e endostromatolites the cold climate carbonate precipitates have a highly variable isotopic composition with 18 o values ranging between 6 5 and 28 vsmow and 13 c values in the 10 20 vpdb range however each type of carbonate precipitates has a specific 13 c and 18 o range suggesting that their environmental setting and the mechanism by which they formed controls their 13 c and 18 o signature it was found that carbonate deposits that precipitated under equilibrium physico chemical conditions had a 13 c value that is in equilibrium with that of the parent water while its 18 o composition was more variable as it is in part controlled by the temperature of reaction and by the 18 o and calcite saturation state of the parent water by contrast the 18 o composition of biologically precipitated carbonate deposits endostromatolites reflect that of the parent water while its 13 c composition was enriched over that of the parent water due to bacterial methanogenesis in the case of kinetically precipitated carbonate deposits the 18 o and 13 c values are out of equilibrium relative to that of the parent water due to the faster rate of reaction

large arctic temperature change at the wisconsin holocene glacial transition analysis of borehole temperature and greenland ice sheet project ii ice core isotopic composition reveals that the warming from average glacial conditions to the holocene in central greenland was large approximately 15 c this is at least three times the coincident temperature change in the tropics and mid latitudes the coldest periods of the last glacial were probably 21 c colder than at present over the greenland ice sheet

holocene temperature evolution in the northern hemisphere high latitudes model data comparisons abstract heterogeneous holocene climate evolutions in the northern hemisphere high latitudes are primarily determined by orbital scale insolation variations and melting ice sheets previous inter model comparisons have revealed that multi simulation consistencies vary spatially we therefore compared multiple model results with proxy based reconstructions in fennoscandia greenland north canada alaska and siberia our model data comparisons reveal that data and models generally agree in fennoscandia greenland and canada with the early holocene warming and subsequent gradual decrease to 0 ka bp hereinafter referred as ka in fennoscandia simulations and pollen data suggest a 2 c warming by 8 ka but this is less expressed in chironomid data in canada a strong early holocene warming is suggested by both the simulations and pollen results in greenland the magnitude of early holocene warming ranges from 6 c in simulations to 8 c in 18 o based temperatures simulated and reconstructed temperatures are mismatched in alaska pollen data suggest strong early holocene warming while the simulations indicate constant holocene cooling and chironomid data show a stable trend meanwhile a high frequency of alaskan peatland initiation before 9 ka can reflect a either high temperature high soil moisture or large seasonality in high latitude siberia although simulations and proxy data depict high holocene temperatures these signals are noisy owing to a large spread in the simulations and between pollen and chironomid results on the whole the holocene climate evolutions in most regions fennoscandia greenland and canada are well established and understood but important questions regarding the holocene temperature trend and mechanisms remain for alaska and siberia

quaternary sea ice history in the arctic ocean based on a new ostracode sea ice proxy paleo sea ice history in the arctic ocean was reconstructed using the sea ice dwelling ostracode acetabulastoma arcticum from late quaternary sediments from the mendeleyev lomonosov and gakkel ridges the morris jesup rise and the yermak plateau results suggest intermittently high levels of perennial sea ice in the central arctic ocean during marine isotope stage mis 3 25 45 ka minimal sea ice during the last deglacial 16 11 ka and early holocene thermal maximum 11 5 ka and increasing sea ice during the mid to late holocene 5 0 ka sediment core records from the iceland and rockall plateaus show that perennial sea ice existed in these regions only during glacial intervals mis 2 4 and 6 these results show that sea ice exhibits complex temporal and spatial variability during different climatic regimes and that the development of modern perennial sea ice may be a relatively recent phenomenon

quantification of subaerial and episodic subglacial erosion rates on high latitude upland plateaus cumberland peninsula baffin island arctic canada abstract long term rates of subaerial and episodic subglacial erosion by predominately cold based ice cover are determined for tors on weathered plateaus on cumberland peninsula by measuring terrestrial cosmogenic nuclide concentrations in differentially weathered surfaces on a given tor we reconstruct the complex exposure and erosion history involving recurring cold based ice cover the style and rate of subaerial and subglacial erosion at multiple tor sites on cumberland peninsula are assessed with a monte carlo approach that computes plausible exposure histories based on a proxy record of global ice volume constant subaerial erosion rates by weathering are low

the climate signal recorded in the oxygen isotope accumulation and major ion time series from the eclipse ice core yukon territory canada the high accumulation rate nearly complete preservation and detailed chronology of the eclipse ice core yukonterritory canada are well suited for comparison oftheglaciochemicalrecordwith instrumentaltimeseriesoftemperature precipitationand sea level pressure results of cross correlation analysis of instrumental temperature records withthe eclipse d 18 otime seriesreveal a significantpositive relationshipbetween summer time d 18 o at eclipse and summer april september temperatures in northwestern north america the results indicate that the eclipse d 18 o time series provides a better proxy for regionaltemperature than doesthe d 18 otime series fromthe mount logan ice core record for which only negative correlations were found winter accumulation at eclipse is signifi cantly correlated with several sites in alaska but not with any sites intheyukon the d 18 o accumulation and glaciochemical time series also display significant correlations with the northern hemisphere sea level pressure dataset especially between wintertime sulfate and nitrate concentrations at eclipse and the intensity of the wintertime siberian high and aleutianandicelandiclows theseresultssuggestthatyear to yearvariabilityinthedeposi tionof pollutants at eclipsecanbe linkedto changesin atmospheric circulation while long termtrendscanbe explainedbychanges in source strength

ice core net snow accumulation and seasonal snow chemistry at a temperate glacier site mount waddington southwest british columbia canada a 141m ice core was recovered from combatant col 51 385 n 125 258 w 3000ma s l mount waddington coast mountains british columbia canada records of black carbon dust lead and water stable isotopes demonstrate that unambiguous seasonality is preserved throughout the core despite summer surface snowmelt and temperate ice high accumulation rates at the site 4 m ice eq a 1 limit modification of annual stratigraphy by percolation of surface meltwater the ice core record spans the period 1973 2010 an annually averaged time series of lead concentrations from the core correlates well with historical records of lead emission from north america and with ice core records of lead from the greenland ice sheet the depth age scale for the ice core provides sufficient constraint on the vertical strain to allow estimation of the age of the ice at bedrock total ice thickness at combatant col is 250 m an ice core to bedrock would likely contain ice in excess of 200 years in age accumulation at combatant col is significantly correlated with both regional precipitation and large scale geopotential height anomalies

physical properties of the p96 ice core from penny ice cap baffin island canada and derived climatic records 1 ice cores from nonpolar environments are being developed as valuable paleoclimatic resources however the recognition of a climatic signal and the development of timescales in those ice cores are both difficult due to heavy summer melting a 177 91 m long ice core p96 was drilled in such a high melt area from penny ice cap baffin island canada in 1996 the core covers the holocene period and has pre holocene ice near the bed the purpose of this work is to investigate the physical properties of the ice and to show how these properties can be interpreted in terms of climatic signals visual stratigraphic observations and measurements of crystal size and c axis orientation were performed using conventional techniques melt features provided a clear picture of holocene summer climatic changes a warmer period prior to 2 ka the little ice age and the modern warming trend the crystalline structure displayed normal grain growth down to 50 m and recrystallization below this in the 0 50 m depth interval periodical variations in crystal size were observed and are attributed to the difference of time for which the ice was soaked in meltwater every season these variations made it possible to develop an annual record the c axis fabric evolution displayed a change in the ice flow pattern from divergent above 140 m depth to shear dominated flow below that the initial fabric of superimposed ice shows a preferred c axis distribution normal to the surface the fabric is shown to be important for reconstructing mass balance chronologies from ice cores drilled in areas of superimposed ice formation these physical properties provide information on climatic change

neoglacial ice expansion and late holocene cold based ice cap dynamics on cumberland peninsula baffin island arctic canada abstract radiocarbon dating of fossil flora and fauna collected along receding cold based ice caps and cold based sections of polythermal glaciers on cumberland peninsula reveal insights into neoglacial ice expansion and late holocene ice dynamics the taphonomic advantages of subfossilized moss were exploited to precisely document regional expansions of ice caps through the late holocene when compared with climate proxies and records of volcanic eruptions the moss radiocarbon age distributions indicate i onset of neoglaciation shortly after 5 ka concomitant with increased sea ice cover ii intensification of ice expansion between 1 9 and 1 1 ka followed by halt of ice growth or ice recession during the medieval warm period and iii renewed ice expansion after 0 8 ka in response to cooling related to a combination of large volcanic eruptions and low solar activity overall the observations support a model of near instantaneous glacial response to regional climate controls and that these responses were synchronous throughout eastern canadian arctic and possibly eastern greenland

paleo environmental gateways in the eastern canadian arctic recent isotope hydrology and diatom oxygen isotopes from nettilling lake baffin island canada abstract nettilling lake is located on baffin island nunavut canada between the areas of past warming canadian high arctic to the north and climatic stability northern quebec and labrador region to the south despite being the largest lake in the nunavut region with a postglacial marine to lacustrine transition history only a few paleo environmental investigations were completed in this area the oxygen isotope composition of diatoms 18odiatom can provide valuable insights into paleo environmental conditions here the recent isotope hydrology and hydrochemical data from the lake are presented to facilitate the interpretation of a 18odiatom record from an 82 cm sediment core ni 2b the well mixed lake 18owater 17 4 is influenced by a heavier less negative isotope composition 18 80 from amadjuak river draining amadjuak lake to the south and water of lighter more negative isotopic composition 16 4 from the isurtuq river originating from penny ice cap in the north east from the 18owater and 18odiatom of the topmost sample of core ni 2b a 18osilica water of 1000 ln silica water 40 2 for sub recent diatoms of nettilling lake was calculated matching the known water silica fractionation for fossil sediments well and thereby showing the general applicability of this proxy for paleo reconstructions in this region extremely large 18odiatom variations in the core of more than 13 are mainly induced by changes in the isotopic composition of the lake water due to a shift from glaciomarine 18odiatom 34 6 through brackish 23 4 to 27 2 towards lacustrine 21 5 conditions transition zones glaciomarine to brackish at 69 cm 7300 yr cal bp and brackish to lacustrine at 35 cm 6000 yr cal bp associated with a shift in the degree of salinity our study provides the first evidence that paleo salinity can be reconstructed by 18odiatom additionally for the lacustrine section it could be demonstrated that 18odiatom may serve as a proxy for past air temperature within the same core recording a late holocene cooling of about 4 c being consistent with other published values for the greater baffin region

revised estimates of recent mass loss rates for penny ice cap baffin island based on 2005 2014 elevation changes modified for firn densification repeat airborne or satellite measurements of surface elevation over ice caps are often used tocalculate glacier wide surface mass changes over time however these measurements typically do notacco