late weichselian relative sea level changes and ice sheet history in southeast greenland relative sea level rsl observations from the margins of the greenland ice sheet gis provide information regarding the timing and rate of deglaciation and constraints on geophysical models of ice sheet evolution in this paper we present the first rsl record for the southeast sector of the gis based on field observations completed close to ammassalik the local marine limit is c 69 m above sea level asl and is dated to c 11 k cal yrs bp thousand calibrated years before present and is a minimum date for ice free conditions at the study site rsl fell to c 24 m asl by 9 5 k cal yrs bp and continued to fall at a decreasing rate to reach close to present by 6 5 k cal yrs bp our chronology agrees with radiocarbon dates from offshore cores that indicate ice free conditions on the adjacent mid shelf by 15 k cal yrs bp we compare the new rsl data with predictions generated using two recently published glaciological models of the gis that differ in the amount and timing of ice loading and unloading over our study area these two gis models are coupled to the same earth viscosity model and background global ice model to aid in the data model comparison neither model provides a close fit to the rsl observations based on a preliminary sensitivity study using a suite of earth viscosity models we conclude that the poor data model fit is most likely due to an underestimate of the local ice unloading an improved fit could be achieved by delaying the retreat of a thicker ice sheet across the continental shelf a thick ice sheet extending well onto the continental shelf is in agreement with other recent observations elsewhere in east and south greenland

detection of anomalous seismic phases by the wavelet transform summary strong motion data at la union one of three near fault stations of the michoacan mexico earthquake in 1985 are analysed by a wavelet transform in order to identify a clear later energy arrival whose frequency content and particle motion are quite different from the main part of the seismograms we used an orthonormal set of analysing wavelets a discrete wavelet transform proposed by meyer and yamada with which an efficient computational procedure can be achieved utilizing the fast fourier transform results of an application of the above wavelet transform to three component velocity data of la union are summarized as follows a vertical seismogram does not contain any distinguishable later energy arrivals for the entire frequency range recorded the major energy arrives in the time interval between 10 and 30 s in contrast an east west component seismogram shows a peculiar later arrival more than 10 s later than the main energy arrival and our wavelet analysis shows that this later phase is characterized by an arrival time of 38 s and a frequency range from 0 1 to 1 hz where the amplitude of the later phase is even larger than the main part this example clearly demonstrates the potential of wavelet transforms to identify objectively any phase in seismograms localized in both time and frequency from the information on its particle motion the above phase corresponds to a heterogeneous and delayed break of one stronger portion on a fault on which the rupture was very smooth or crack like elsewhere

first indication of storegga tsunami deposits from east greenland a 2 73 m long sediment sequence from loon lake located at 18m a s l on outer geographical society o east greenland was investigated for its chronology and changes in physical and biogeochemical properties macrofossils and grain size distribution the predominance of marine fossils throughout the sequence dated by 14c ams to between 8630 and 7535 cal yr bp shows that the loon lake at that time was a marine basin which according to existing sea level curves was about 15 35 m deep the sequence mainly consists of fine grained homogeneous sediments which are interrupted by a 0 72 m thick sandy horizon with erosive basis and distinct fluctuations in the grain size distribution and in the physical and biogeochemical properties according to the radiocarbon dates this sandy horizon was deposited after 8500 8300 cal yr bp and is interpreted as originating from the storegga tsunami the record from loon lake provides the first indication of storegga tsunami deposits from east greenland copyright 2006 john wiley sons ltd

multiple stage deglacial retreat of the southern greenland ice sheet linked with irminger current warm water transport 1 there is limited knowledge pertaining to the history of the greenland ice sheet gis during the last glacial interglacial transition as it retreated from the continental margins to an inland position here we use multiproxy data including ice rafted debris ird planktonic isotopes alkenone temperatures and tephra geochemistry from the northern labrador sea off southwest greenland to investigate the deglacial response of the gis and evaluate its implications for the north atlantic deglacial development the results imply that the southern gis retreated in three successive stages 1 early deglaciation of the east greenland margins by tephra rich ird that embrace heinrich event 1 2 progressive retreat during allerod culminating in major meltwater releases 18o depletion of 1 2 at the allerod younger dryas transition 12 8 13 0 kyr b p and 3 a final stage of glacial recession during the early holocene 9 11 kyr b p rather than indicating local temperatures of ambient surface water the alkenones likely were transported to the core site by the irminger current we attribute the timing of gis retreat to the incursion of warm intermediate waters along the base of grounded glaciers and below floating ice shelves on the continental margin the results lend support to the view that gis meltwater presented a forcing factor for the younger dryas cooling

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

authigenic 10be 9be ratios and 10be fluxes 230thxs normalized in central baffin bay sediments during the last glacial cycle paleoenvironmental implications abstract authigenic 10 be 9 be ratios and 10 be fluxes reconstructed using the 230 th xs normalization proxies of the cosmogenic radionuclide 10 be production rate in the atmosphere have been measured in a sedimentary core from baffin bay north atlantic spanning the last 136 ka bp the normalization applied on the exchangeable authigenic 10 be concentrations using the authigenic 9 be isotope and 230 th xs methods yield equivalent results strongly correlated with sedimentological parameters grain size and mineralogy lower authigenic beryllium be concentrations and 10 be 9 be ratios are associated with coarse grained carbonate rich layers while higher authigenic be values are related to fine grained felspar rich sediments this variability is due to i sediment composition control over beryllium scavenging efficiency and ii glacial history that contributed to modify the 10 be concentration in baffin bay by input and boundary scavenging condition changes most paleo denudation rates inferred from the 10 be 9 be ratio vary weakly around 220 76 tons km 2 yr 1 0 09 0 03 mm yr 1 corresponding to relatively steady weathering fluxes over the last glacial cycle except for six brief intervals characterized by sharp increases of the denudation rate these intervals are related to ice surging episodes coeval with heinrich events and the last deglaciation period an average freshwater flux of 180 6 km 3 yr 1 0 006 sv consistent with recent models has been calculated in order to sustain glacially derived 10 be inputs into baffin bay it is concluded that in such environments the authigenic 10 be measured mainly depends on climatic effects related to the glacial dynamics which masks the 10 be production variation modulated by geomagnetic field changes altogether these results challenge the simple interpretation of 10 be concentration variation as a proxy of interglacial glacial interstadial stadial cycles in arctic and sub arctic regions they rather suggest the effect of higher frequency paleoclimatic changes and local glacial dynamics on 10 be signature

late quaternary sedimentary processes and ocean circulation changes at the southeast greenland margin a study has been made of late quaternary depositional processes and bottom current activity on the southeast greenland margin using seismic sub bottom profiling and deep tow side scan sonar data as well as sediment core information the seabed data demonstrate the occurrence of strong southerly bottom currents prevailing on the slope and rise well defined longitudinal bedforms indicate maximum mean near bottom current velocities of up to at least 1 0 m s at the depth stratum of labrador sea water 800 1500 m similarly strong currents occur in denmark strait overflow water dsow at the base of the slope whereas more basinward the maximum dsow flow speed is lower iceberg plow marks were found down to about 700 m water depth both at the shelf edge and on the lower slope and rise the seafloor morphology is indicative of downslope sediment transport and mass flow deposition which is concluded to be a typically glacial feature after generally more sluggish deep water circulation during the last glacial maximum dsow basin ventilation was re established shortly before 13 3 ka on the shelf in front of the retreating greenland ice margin permanent or semi permanent sea ice conditions prevailed until about 12 5 ka at that time increased irminger current activity had resulted in warming and east greenland current egc controlled iceberg drift increased no evidence was found for a return to extreme glacial conditions or a ceasing of dsow flow during the younger dryas abundant coarse ird collected at greater water depth from shallow sub seabed strata has a provenance mainly in the northern part of east greenland 68 73 n which demonstrates the existence of a pre holocene egc system initially extending to beyond the shelf edge

greenland glacial history and local geodynamic consequences summary space time reconstructions of the continental ice sheets that existed at last glacial maximum lgm have previously been produced using two entirely independent methodologies one based upon the use of theoretical models of ice sheet accumulation and flow and one based upon the geophysical inversion of relative sea level rsl histories from previously ice covered regions the analyses described in this paper demonstrate the significant advantages that derive from the simultaneous application of both methods to the particular case of greenland we thereby show that the ice 4g reconstruction of the glaciation history of this region from lgm to present which was based upon the geophysical inversion of rsl data alone was reasonably accurate in the peripheral regions where rsl data were available but inaccurate in the interior of the ice sheet which was unconstrained by such information we test the new model of greenland glacial history determined by the simultaneous application of the constraints that derive from ice sheet modelling and the geophysical inversion of rsl data by employing recently published geodetic inferences of mass balance over the entire interior region of the ice sheet and of gps measurements of vertical crustal motion these observations which were not employed to constrain the ice sheet reconstruction provide significant support for the new glacial history for greenland that our analyses have led us to infer

reconstructing recent relative sea level changes in west greenland local diatom based transfer functions are superior to regional models we present the results of an investigation into the potential of salt marshes in the aasiaat area west greenland for recent relative sea level rsl reconstruction we use 64 modern diatom samples to develop a transfer function that has a rmsep of 0 16 m and an r2 of 0 84 we combine these with a similar data set from sisimiut 250 km south of aasiaat standardising the data to account for tidal range differences an aasiaat sisimiut and a combined model is used to reconstruct rsl change from two recently deposited sediment sections all three models predict similar rsl change for sediment deposited in low marsh settings but for sediment deposited in high marsh environments the models differ our preferred aasiaat model reconstructs rsl rise from c 0 6 m at c 570 cal yr bp to stabilise within 0 20 m of present after 400 cal yr bp model differences are related to variations in the high marsh upland vegetation zones diatom assemblages and organic content between sites that are likely related to differences in tidal range we conclude that a local transfer function model is superior to a combined site model for rsl reconstruction in west greenland

the deglacial history of southeast sector of the greenland ice sheet during the last glacial maximum the southeast sector of the greenland ice sheet is currently experiencing rapid changes in mass balance and ice sheet dynamics at low elevations however to what extent these changes are typical of the behaviour of this sector of the ice sheet is uncertain as our understanding of the longer term controls on ice sheet dynamics in this region is limited two models exist for last glacial maximum lgm ice sheet configuration in east greenland the first minimum model envisages a restricted ice sheet with exposed nunataks in coastal areas and limited ice extent onto the continental shelf fed by ice flowing through bedrock troughs a second maximum model entails a thicker ice sheet with limited coastal nunataks and ice filling the coastal valleys and extending across the entire continental shelf radiocarbon dates on foraminifera collected from seabed cores on the southeast greenland continental shelf suggest that the ice sheet reached a maximum extent at ca 22 kcal yr before retreating perhaps as early as ca 17 kcal yr bp and reaching the present coast at ca 10 kcal yr bp this paper presents the results of a study designed to test these different ice sheet models based on geomorphological mapping and cosmogenic isotope analyses in the torqulertivit imiat valley an area to the east of the coastal town of ammassalik 26al and 10be measurements on abraded bedrock surfaces in terrain above local trimlines yield surface exposure ages of ca 11 8 9 9 ka this demonstrates warm based glacial erosion of high level surfaces ca 740 m asl followed by trimline formation during deglaciation and intense postglacial weathering our work constrains minimum ice thickness during the lgm to at least 740 m and supports a maximum ice sheet model in this sector of the gis ice sheet retreat from the continental shelf to the southern edge of sermilik fjord is dated to ca 11 1 9 7 ka and helps to constrain the timing of the early holocene retreat of the helheim glacier ice stream within the torqulertivit imiat valley age determinations from glacially abraded terrain above the local marine limit on the coast 11 1 9 7 ka and those from 10 km up valley 12 8 9 9 ka suggest rapid surface ablation during these intervals coincident with rapid atmospheric warming observed in the greenland ice core records

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

high resolution study of icelandic tephras in the kangerlussuaq trough southeast greenland during the last deglaciation tephra abundance data and geochemistry in late glacial and holocene sediments on the east greenland shelf are presented two well known tephras were identified from electron microprobe analysis of tephra shards picked from ash peaks in the cores these are the vedde ash and saksunarvatn ash which probably were deposited on the shelf after transport on drifting ice the radiocarbon dates marine reservoir corrected by 550 yr that constrain the timing of deposition of the tephra layers compare well with the terrestrial and ice core ages of the tephras without requiring additional reservoir correction to align them with the known tephra ages several prominent tephra layers with a composition of ash zone 2 tephra punctuate the deglacial sediments these tephra peaks coincide with significant light stable isotope events signifying glacial meltwater and fine grained sediments poor in ice rafted detritus we interpret the ash zone 2 tephra peaks as sediment released from the greenland ice sheet during strong melting pulses of the deglaciation copyright 2002 john wiley sons ltd

astronomical theory of the pleistocene ice ages a brief historical review abstract this paper traces the evolution of the astronomical theory of the pleistocene ice ages from its origin in the work of adhemar and croll through its quantitative transformation in the hands of milankovitch to its current renaissance emphasis is given to the interplay between climatic theory and geologic observation from 1941 when milankovitch published his final version of the theory until the early 1970s most attempts to test the theory empirically were carried out in the time domain by comparing the geologic record of climate with predicted climate curves these attempts ran into serious difficulties particularly the inaccuracy of the geologic time scale and the ambiguity of climate predictions early attempts to evaluate the theory with simple radiation balance models appeared to indicate that the climatic response to secular changes in the orbit would be too small to be observed geologically but by the mid 1970s the advent of an improved time scale for pleistocene marine deposits and the availability of long closely sampled records made it possible to arrange generalized but unambiguous tests of the theory in the frequency domain by comparing orbital and climatic spectra these results decisively confirmed the idea that orbital variations significantly influenced the earth s climate during the pleistocene but they did not tell us how this influence was exercised the emphasis of current work has therefore shifted to the identification and quantitative modeling of physical mechanisms by which the climate system responds so dramatically to the predicted rather subtle changes in radiative boundary conditions

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

the influence of decadal to millennial scale ice mass changes on present day vertical land motion in greenland implications for the interpretation of gps observations 1 we show predictions of present day vertical land motion in greenland using a recently developed glacial isostatic adjustment gia model calibrated using both relative sea level rsl observations and geomorphological constraints on ice extent predictions from our gia model are in agreement with the relatively small number of gps measurements of absolute vertical motion from south and southwest greenland this suggests that our model of ice sheet evolution over the holocene period is reasonably accurate the uplift predictions are highly sensitive to variations of upper mantle viscosity thus depending on the earth model adopted different periods of ice loading change dominate the present day response in particular regions of greenland we also consider the possible influence of more recent changes in the ice sheet by applying a second ice model specifically a surface mass balance smb model which covers the period 1866 to 2005 predictions from this model suggest that decadal scale smb changes over the past 140 years play only a small role in determining the present day viscous response at the sub mm yr level in most locations for a range of earth model parameters high rates of peripheral thinning from 1995 to 2005 predicted using the smb model produce large elastic uplift rates 6 mm yr in west and southwest greenland this suggests that in some areas close to the ice margin modern surface mass balance changes have a dominant control on present day vertical land motion

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

late holocene relative sea level rise and the neoglacial history of the greenland ice sheet in west greenland early and mid holocene relative sea level rsl fall was replaced by late holocene rsl rise during the neoglacial after 4 3 cal ka bp thousand calibrated years before present here we present the results of an isolation basin rsl study completed near to the coastal town of sisimiut in central west greenland rsl fell from 14 m above sea level at 5 7 cal ka bp to reach a lowstand of 4 0 m at 2 3 1 2 cal ka bp before rising by an equivalent amount to present differences in the timing and magnitude of the rsl lowstand between this and other sites in west and south greenland record the varied interplay of local and non greenland rsl processes notably the reloading of the earth s crust caused by a neoglacial expansion of the greenland ice sheet gis and the subsidence associated with the collapse of the laurentide ice sheet forebulge this means that the timing of the sea level lowstand cannot be used to infer directly when the gis advanced during the neoglacial the rise in late holocene rsl is contrary to recently reported bedrock uplift in the sisimiut area based on repeat gps surveys this indicates that a belt of peripheral subsidence around the current ice sheet margin was more extensive in the late holocene and that there has been a switch from subsidence to uplift at some point in the last thousand years or so

the east greenland continental margin 65 n since the last deglaciation changes in seafloor properties and ocean circulation nine gravity cores collected on the east greenland continental margin off kangerdlugssuaq fjord reveal a drastic decrease in average sedimentation rates from the cross shelf through the continental slope from 43 2 cm kyrs to 2 2 cm kyrs respectively since the last deglaciation beginning at 2g cm2kyrs at 4000 yrs b p both caco3 and non caco3 accumulation rates became high g cm2kyrs since 3000 yrs b p these rates distinctly decreased melting of glaciers and current activity which drastically changed in space and time controlled the terrigenous sediment input and thus the grain size distribution and the physical properties of sediments across the shelf these observations suggest that current winnowing on sediments is one of the dominant processes at present this is seen in the acoustic reflectivity and in the acoustically hard seafloor particularly at the upper continental slope in addition icebergs transported southward along the continental margin have scoured the sediment surface in water depths 350m

palaeoecology of two lake basins from disko west greenland the macrofossils lithology and chronology of two lake basins on disko in central west greenland have been investigated both lakes were isolated from the sea in the mid holocene as a result of relative land uplift a marine brackish limnic sequence was recovered from the qivittut lake the marine fauna is unusually diverse whereas the brackish water fauna consists only of few species immediately after isolation the lake passed through a short lived eutrophic phase after which stable mesotrophic conditions were established from the second lake basin the fortunebay lake only limnic sediments were recovered this lake record demonstrates that rather stable conditions have persisted since mid holocene times both lakes show anomalously high accumulation rates

a younger dryas re advance of local glaciers in north greenland abstract the younger dryas yd is a well constrained cold event from 12 900 to 11 700 years ago but it remains unclear how the cooling and subsequent abrupt warming recorded in ice cores was translated into ice margin fluctuations in greenland here we present 10be surface exposure ages from three moraines in front of local glaciers on a 50 km stretch along the north coast of greenland facing the arctic ocean ten ages range from 11 6 0 5 to 27 2 0 9 ka with a mean age of 12 5 0 7 ka after exclusion of two outliers we consider this to be a minimum age for the abandonment of the moraines the ages of the moraines are furthermore constrained using optically stimulated luminescence osl dating of epishelf sediments which were deposited prior to the ice advance that formed the moraines yielding a maximum age of 12 4 0 6 ka and bracketing the formation and subsequent abandonment of the moraines to within the interval 11 8 13 0 ka ago this is the first time a synchronous yd glacier advance and subsequent retreat has been recorded for several independent glaciers in greenland in most other areas there is no evidence for re advance and glaciers were retreating during yd we explain the different behaviour of the glaciers in northernmost greenland as a function of their remoteness from the atlantic meridional overturning circulation amoc which in other areas has been held responsible for modifying the yd drop in temperatures

salt marshes as archives of recent relative sea level change in west greenland abstract temperate latitude salt marshes are a proven environment from which high precision 0 10 0 20 m relative sea level rsl records can be developed over recent decades and centuries such records provide an important link between millennial histories of rsl change and instrumental records the high latitude salt marshes in greenland have not previously been explored as potential archives of recent rsl change here we develop four diatom based transfer functions using contemporary diatom data collected from three salt marshes located 40 km south of the coastal town of sisimiut west greenland our preferred model has a good fit between observed and predicted elevations r 2 0 94 and a root mean square error prediction of 0 19 m we apply the four models to a short sediment profile collected from one of the marshes that formed between c 600 cal year bp and the present three of the four models predict the same trend in which rsl rose from 0 55 0 19 m mean tide level mtl to 0 05 0 19 m mtl between c 600 and 400 cal year bp at a rate of c 2 7 mm year 1 after 400 cal year bp rsl slowed and remained stable until the present day the results of this study demonstrate that greenland salt marshes are potentially valuable archives of data for developing quantitative estimates of rsl change during the last few centuries thereby bridging the gap between existing millennial scale approaches and more recent direct observations of ice sheet behaviour and associated vertical land motions

the deglaciation of coastal areas of southeast greenland large marine terminating glaciers around the margins of the greenland ice sheet have retreated accelerated and thinned over the last two decades relatively little is known about the longer term behaviour of the greenland ice sheet yet this information is valuable for assessing the significance of modern changes we address this by reporting 11 new beryllium 10 10be exposure ages from previously uninvestigated coastal areas across southeast greenland the new ages are combined with existing data from the region to assess the timing of glacier retreat after the last glacial maximum the results show that deglaciation occurred first in the north of the region 68 n and progressed southwards this north south progression is attributed to the influence of the warm irminger current on the ice margin areas in the south of the region were isolated from the warm waters by the shallow bathymetry of the continental shelf this demonstrates that oceanographic forcing paced the deglaciation of southeast greenl

constraints on the greenland ice sheet since the last glacial maximum from sea level observations and glacial rebound models abstract geomorphological descriptions of changes in the extent of the greenland ice sheet gis have been combined with glacial isostatic adjustment models to reproduce the sea level history of greenland since the last glacial maximum lgm the contribution to past sea level change around greenland due to ice load changes outside of that region has been considerable 10 s of meters while still contributing a rise of several mm yr 1 today the isostatic contribution to relative sea level around greenland from changes in the gis is found by iteratively perturbing preliminary ice models with different lgm extents and deglaciation starting times the resulting first order model that provides the best agreement between observed and predicted sea level contributes 3 1 and 1 9 m water equivalent of additional ice relative to present day ice volumes at the lgm and younger dryas respectively the gis in most areas does not appear to have extended far onto the continental shelf the exceptions being southern most southwest greenland and northern east greenland as well as at the coalescence of the northwest greenland and innuitian ice sheets changes in ice thickness since the lgm were 500 m along the present day outer coast and 1500 m along some parts of the present day ice margin the observed mid to late holocene fall in sea level to below the present day level and the subsequent transgression seen in some areas implies that the gis retreated behind the present day margin by distances of the order of 40 km before readvancing

fluctuations of local glaciers in greenland during latest pleistocene and holocene time abstract this paper is the first to summarize research on fluctuations of local glaciers in greenland e g ice caps and mountain glaciers independent of the greenland ice sheet during latest pleistocene and holocene time in contrast to the extensive data available for fluctuations of the greenland ice sheet surprisingly little data exist to constrain local glacier extents much of the available research was conducted prior to wide spread use of ams radiocarbon dating and the advent of surface exposure and luminescence dating although there is a paucity of data generally similar patterns of local glacier fluctuations are observed in all regions of greenland and likely reflect changes in paleoclimate which must have influenced at least the margins of the inland ice absolute age data for late glacial and early holocene advances of local glaciers are reported from only two locations disko island and the scoresby sund region subsequent to late glacial or early holocene time most local glaciers were smaller than at present or may have disappeared completely during the holocene thermal maximum in general local glacier advances that occurred during historical time 1200 1940 ad are the most extensive since late glacial or early holocene time historical documents and more recent aerial photographs provide useful information about local glacier fluctuations during the last 100 yrs in all but one area north greenland local glaciers are currently receding from historical extents

relative sea level changes since 15 000 cal yr bp in the nanortalik area southern greenland we present new results for relative sea level change for southern greenland for the interval from 9000 cal yr bp to the present together with earlier work from the same region this yields a nearly complete record from the time of deglaciation to the present isolation and or transgression sequences in one lake and five tidal basins have been identified using lithostratigraphic analyses sedimentary characteristics magnetic susceptibility saturated induced remanent magnetisation sirm organic and carbonate content and macrofossil analyses ams radiocarbon dating of macrofossils and bulk sediment samples provides the timescale relative sea level fell rapidly and reached present day level at similar to 9300 cal yr bp and continued falling until at least 9000 cal yr bp between 8000and6000cal yrbpsea level reached its lowest level of around similar to 10m below highest astronomical tide at around 5000 cal yr bp sea level had reached above 7 8 m below highest astronomical tide and slowly continued to rise not reaching present day sea level until today the isostatic rebound caused rapid isolation of the basins that are seen as distinct isolation contacts in the sediments in contrast the late holocene transgressions are less well defined and occurred over longer time intervals the late holocene sea level rise may be a consequence of isostatic reloading by advancing glaciers and or an effect of the delayed response to isostatic rebound of the laurentide ice sheet one consequence of this transgression is that settlements of palaeo eskimo cultures may be missing in southern greenland copyright c 2006 john wiley sons ltd

chronology of the last recession of the greenland ice sheet a new deglaciation chronology for the ice free parts of greenland the continental shelf and eastern ellesmere island canada is proposed the chronology is based on a new compilation of all published radiocarbon dates from greenland and includes crucial new material from southern northeastern and northwestern greenland although each date provides only a minimum age for the local deglaciation some of the dates come from species that indicate ice proximal glaciomarine conditions and thus may be connected with the actual ice recession in addition to shell dates dates from marine algae lake sediments peat terrestrial plants and driftwood also are included only offshore and in the far south have secure late glacial sediments been found other previous reports of late glacial sediments older than 11 5 cal kyr bp from onshore parts of greenland need to be confirmed most of the present ice free parts of greenland and nares strait between greenland and ellesmere island were not deglaciated until the early holocene copyright c 2002 john wiley sons ltd less

late cenozoic seismic stratigraphy and glacial geological development of the east greenland and svalbard barents sea continental margins abstract the european program on the late cenozoic evolution of the polar north atlantic margins ponam running from 1990 to 1994 resulted in a wealth of seismic data and sediment cores particularly from the svalbard and barents sea continental margin but also from areas of the east greenland margin deep sediment coring was undertaken on both margins during odp legs 152 and 162 this paper uses the ponam generated information as well as previous and subsequent seismic and core data to review our present understanding of the glacial geological development of these regions four main depositional facies have been identified these are represented by hemipelagic glaciomarine sediments sandy silty debris flows diamictic debris flows and tills deposited directly beneath grounded ice the temporal and spatial distribution of these four facies determines the architecture and seismic character of the two continental margins the two regions show significant differences with regard to both the timing of initial glaciation and the response of the ice sheets to climatic variability glacial deposition has taken place on the east greenland margin at least since 7 ma but apparently only since 2 5 ma on the svalbard barents sea margin significant glacial expansion across the continental shelf probably occurred in the early and late pliocene in east greenland whereas the glaciers on svalbard and the barents sea did not reach the shelf edge until the early pleistocene despite a shorter glacial period average glacial sedimentation rates are 2 3 times higher on the svalbard barents sea margin than on the studied parts of the east greenland margin the svalbard barents sea ice sheet has advanced and retreated much more frequently during the plio pleistocene than the greenland ice sheet glacial regime polar on greenland and polythermal to temperate in svalbard and the barents sea and the more easily erodible preglacial bedrock of svalbard and the barents sea are thought to be main factors responsible for the differences in ice sheet behavior and consequently glacial sediment production

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

a first detailed look at the greenland lithosphere and upper mantle using rayleigh wave tomography we present the results of a surface wave study carried out across greenland as part of the glatis greenland lithosphere analysed teleseismically on the ice sheet project rayleigh wave phase velocity dispersion curves were estimated for 45 two station paths across greenland using data from large teleseismic earthquakes the individual dispersion curves show characteristics broadly consistent with those of continental shields worldwide but with significant differences across the greenland landmass reliable phase velocity measurements were made over a period range of 25 160 s providing constraint on mantle structure to a depth of 300 km an isotropic tomographic inversion was used to combine the phase velocity information from the dispersion curves in order to calculate phase velocity maps for greenland at several different periods the greatest lateral variation in phase velocity is observed at intermediate periods 50 80 s where a high velocity anomaly is resolved beneath central southwestern greenland and a low velocity anomaly is resolved beneath southeastern greenland the results of the phase velocity inversion were used to construct localized dispersion curves for node points along two parallel north south profiles in southern greenland these curves were inverted to obtain models of shear wave velocity structure as a function of depth again with the assumption of isotropic structure a similar inversion was carried out for two two station dispersion curves in northern greenland where the resolution of the phase velocity maps is relatively low the models show a high velocity lid structure overlying a zone of lower velocity beneath which the velocity gradually increases with depth the lid structure is interpreted as the continental lithosphere within the lithosphere the shear wave velocity is 4 12 per cent above global reference models with the highest velocities beneath central southwestern greenland however the assumption of isotropic structure means that the maximum velocity perturbation may be overestimated by a few per cent the lithospheric thickness varies from 100 km close to the southeast coast of greenland to 180 km beneath central southern greenland

freshwater forcing from the greenland ice sheet during the younger dryas evidence from southeastern greenland shelf cores abstract we present evidence for freshwater forcing from the greenland ice sheet during the last deglaciation explore its potential involvement in the younger dryas cooling and investigate the role of atlantic intermediate water in the retreat of the greenland ice sheet paleoceanographic conditions and ice sheet retreat history are interpreted from ird stable isotopes and foraminiferal assemblages in sediment cores retrieved along the length of the kangerlussuaq trough a cross shelf trough on the southeast greenland shelf the vedde ash 11 980 cal yr bp which is a marker bed within the younger dryas and the saksunarvatn tephra 10 180 cal yr bp an early holocene marker horizon have been located in these cores the tephra markers and calibrated 14c dates on foraminifers and molluscs provide the basis for the age models in the cores the stable isotope records indicate a 0 5 depletion of the 18o between 13 4 and 12 8 cal ka bp a pronounced light isotope event exceeding 1 5 on the inner shelf and 0 8 on the outer shelf occurs at the beginning of the younger dryas cold period 12 8 cal ka bp and ends by 12 cal ka bp immediately before deposition of the vedde ash the light isotope spikes are interpreted as glacial meltwater spikes associated with retreat of the adjacent greenland ice sheet associated with the light isotope events are episodic high percentages of the atlantic intermediate water benthic foraminiferal species cassidulina neoteretis which continue from the bolling allerod into the younger dryas high percentages of this species suggest that atlantic intermediate water entered the kangerlussuaq trough during the allerod and the younger dryas via the irminger current as it does today we conclude that advection of atlantic intermediate water into the kangerlussuaq trough south of the denmark strait promoted melting and retreat of the marine portions of the greenland ice sheet explaining the observed glacial meltwater spikes

timing and significance of glacially influenced mass wasting in the submarine channels of the greenland basin the most extensive systems of submarine channels on the continental margins of the norwegian greenland sea occur in the greenland basin 72 75jn geophysical records show that these channels are up to 100 m deep 4 km wide and extend for about 300 km from the middle continental slope off northeast greenland to the abyssal depths of the basin mass wasting deposits in the form of debris flows and turbidity currents as well as hemipelagic sediments dominate sediment cores recovered from the channels radiocarbon dates indicate that debris flow and turbidity current activity in the channels had ceased by 13 000 years bp and sedimentation rates show a corresponding order of magnitude decrease after this time masswasting in the submarine channels of the greenland basin therefore relates to full glacial and deglacial conditions this implies a more extensive late weichselian ice sheet in northeast greenland than traditionally thought the ice sheet extended onto the outer continental shelf and may have reached the shelf edge delivering debris and sediment laden meltwater onto the upper slope channel formation is most likely the product of turbidity current activity during successive glaciations of the northeast greenland continental shelf holocene sediments from the channel systems are predominantly of hemipelagic origin and formed in a low energy ice distal environment the low gradient 1j channels of the greenland basin are therefore a glacially influenced sedimentary system contrasts in slope morphology and sediment architecture between the greenland basin and trough mouth fans elsewhere in the norwegian greenland sea are not the result of variations in slope gradient rather these contrasts reflect the interplay between bedrock lithology of the continental shelf rates of sediment delivery sediment texture meltwater volume and relative size of ice sheet drainage basins

sea level changes at the lgm from ice dynamic reconstructions of the greenland and antarctic ice sheets during the glacial cycles abstract new experiments were performed with three dimensional thermomechanical models of the greenland and antarctic ice sheets to simulate their behaviour during the glacial cycles to reconstruct their thickness and extent at the last glacial maximum lgm and to estimate their glacio eustatic contribution to the global sea level stand the calculations used improved ice dynamic and isostatic treatments updated datasets on higher grid resolutions and refined climatic treatments based on newly calibrated transfer functions between ice core records and climatic perturbations results are discussed from a reference run with standard parameters that is compared with available glacial geological observations and from a series of sensitivity experiments focusing on isostatic adjustment thermomechanical coupling climatic forcing mass balance changes and basal melting rates and viscosity changes of antarctic ice shelves for the antarctic ice sheet we find that volume changes are closely linked with grounding line changes of the west antarctic ice sheet at the lgm the grounding line extended close to the continental shelf break almost everywhere ice over central east antarctica was generally thinner than today and varied mainly in accordance with accumulation fluctuations for the greenland ice sheet melting is important only during interglacial periods and the most sensitive period concerns the size of the ice sheet during the eemian at the lgm the greenland ice sheet extended beyond the present coastline to cover at least the inner continental shelf and thinned by up to several hundred meters in central areas for a plausible range of parameters the experiments indicate that at the time of maximum sea level depression 21 kyr bp the antarctic ice sheet contributed 14 18 m to the sea level lowering and the greenland ice sheet 2 3 m significantly less than the older climap reconstructions whereas both ice sheets were at 21 kyr bp close to their maximum extent the experiments also indicate that their maximum volumes were reached only by 16 5 kyr bp greenland and 10 kyr bp antarctica equal to an additional sea level lowering of respectively 0 4 and 3 7 m holocene retreat was essentially complete by 5 kyr bp in greenland but is found to still continue today in west antarctica before reversing to growth during the next millenium the models were found to reproduce gross features of the ice sheet s history since the lgm in reasonably good agreement with available glacial geological data although observational control on ice thickness changes remains very limited

new insights on arctic quaternary climate variability from palaeo records and numerical modelling terrestrial and marine geological archives in the arctic contain information on environmental change through quaternary interglacial glacial cycles the arctic palaeoclimate and its extremes apex scientific network aims to better understand the magnitude and frequency of past arctic climate variability with focus on the extreme versus the normal conditions of the climate system one important motivation for studying the amplitude of past natural environmental changes in the arctic is to better understand the role of this region in a global perspective and provide base line conditions against which to explore potential future changes in arctic climate under scenarios of global warming in this review we identify several areas that are distinct to the present programme and highlight some recent advances presented in this special issue concerning arctic palaeo records and natural variability including spatial and temporal variability of the greenland ice sheet arctic ocean sediment stratigraphy past ice shelves and marginal marine ice sheets and the cenozoic history of arctic ocean sea ice in general and holocene oscillations in sea ice concentrations in particular the combined sea ice data suggest that the seasonal arctic sea ice cover was strongly reduced during most of the early holocene and there appear to have been periods of ice free summers in the central arctic ocean this has important consequences for our understanding of the recent trend of declining sea ice and calls for further research on causal links between arctic climate and sea ice

ice sheet extent and early deglacial history of the southwestern sector of the greenland ice sheet the offshore and coastal geomorphology of southwest greenland records evidence for the advance and decay of the greenland ice sheet during the last glacial maximum regional ice flow patterns in the vicinity of sisimiut show an enlarged ice sheet that extended southwestwards on to the shelf with an ice stream centred over holsteinsborg dyb high level periglacial terrain composed of blockfield and tors is dated to between 101 and 142 ka using 26al and 10be cosmogenic exposure ages these limit the maximum surface elevation of the last glacial maximum ice sheet in this part of southwest greenland to ca 750 810 m asl and demonstrate that terrain above this level has been ice free since mis 6 last glacial maximum ice thickness on the coast of ca 700 m implies that the ice sheet reached the mid to outer continental shelf edge to form the outer hellefisk moraines exposure dates record ice surface thinning from 21 0 to 9 8 ka with downwasting rates varying from 0 06 to 0 12 m yr 1 this reflects strong surface ablation associated with increased air temperatures running up to the bolling interstadial gis1e at ca 14 ka and later marine calving under high sea levels the relatively late retreat of the itilleq ice stream inland of the present coastline is similar to the pattern observed at jakobshavn isbrae located 250 km north in disko bugt which also retreated from the continental shelf after ca 10 ka we hypothesise that the ice streams of west greenland persisted on the inner shelf until the early holocene because of their considerable ice thickness and greater ice discharge compared with the adjacent ice sheet

restricted impact of holocene climate variations on the southern greenland ice sheet abstract we use an ice marginal threshold lake lower nordboso in southern greenland to record episodes when the southern greenland ice sheet sgis was close to the present extent represented by beds of clastic sediments whereas gyttja deposition reflects periods when the glacier was behind the threshold and no glacial meltwater input the results show that the sedimentation was initiated at c 10 6 cal ka bp when the ice margin had reached the present extent following the deglaciation after this the ice margin remained close to the present extent until c 6 9 cal ka bp when it retreated behind the threshold and first reappeared with a clear glacial signal at c 3 0 2 8 cal ka bp and from c 0 5 cal ka bp until the present an overall good correlation between clastic input into lower nordboso and ird events from narsaq sound suggests that they represent a general glacial proximity signal of the sgis our data demonstrates that the sgis behaved less vigorously to holocene climate changes compared to previous reconstructions the ice sheet only retreated behind the present ice extent from c 6 9 to 3 0 cal ka bp and c 2 8 to 0 5 cal ka bp in the mountainous southern greenland whereas the more sensitive low lying qassimiut lobe was behind its present margin from c 9 ka until the little ice age accordingly the ice marginal behavior in southern greenland is not only governed by climate changes but also strongly influenced by the local topographic setting

relative sea level change in greenland during the last 700 yrs and ice sheet response to the little ice age this paper presents new evidence regarding relative sea level rsl changes and vertical land motions at three sites in greenland since 1300 a d a time interval that spans the later part of the medieval climate anomaly mca and the little ice age lia we observe rsl rise at two sites in central west greenland from c 0 80 0 20 m at c 1300 a d to c 0 20 m 0 25 m at c 1600 a d after which rsl slowed and then stabilised at a third site in south greenland we observe rsl rise from c 1 40 0 20 m at c 1400 a d until c 1750 a d after which rsl slowed and was stable during at least the latter part of the 20th century the c 1600 a d rsl slow down seen at the two former sites is surprising because it occurs during the lia when one might expect the ice sheet to be gaining mass and causing rsl to rise we interpret this rsl slowdown to indicate a period of enhanced regional mass loss from central west greenland since c 1600 a d and propose two hypotheses for this loss first a reduction in precipitation during cold and dry conditions and second higher air temperatures and increased peripheral surface melt of the ice sheet from this date onwards the latter hypothesis is compatible with a well established temperature seesaw between western greenland and northern europe and potentially a previously identified shift from a positive to generally more negative nao conditions around 1400 to 1600 a d our study shows how rsl data from greenland can provide constraints on the timing of ice sheet fluctuations in the last millennium and challenges the notion that during cold periods in northern europe the ice sheet in west greenland gained mass

biogeochemical evidence for hydrologic changes during the holocene in a lake sediment record from southeast greenland holocene paleoclimate records from greenland help us understand the response of the greenland ice sheet and regional oceanic and atmospheric circulation systems to natural climate variability in or

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

a model of greenland ice sheet deglaciation constrained by observations of relative sea level and ice extent an ice sheet model was constrained to reconstruct the evolution of the greenland ice sheet gris from the last glacial maximum lgm to present to improve our understanding of its response to climate change the study involved applying a glaciological model in series with a glacial isostatic adjustment and relative sea level rsl model the model reconstruction builds upon the work of simpson et al 2009 through four main extensions 1 a larger constraint database consisting of rsl and ice extent data model improvements to the 2 climate and 3 sea level forcing components 4 accounting for uncertainties in non greenland ice the research was conducted primarily to address data model misfits and to quantify inherent model uncertainties with the earth structure and non greenland ice our new model termed huy3 fits the majority of observations and is characterised by a number of defining features during the lgm the ice sheet had an excess of 4 7 m ice equivalent sea level iesl which reached a maximum volume of 5 1 m iesl at 16 5 cal ka bp modelled retreat of ice from the continental shelf progressed at different rates and timings in different sectors southwest and southeast greenland began to retreat from the continental shelf by 16 to 14 cal ka bp thus responding in part to the bolling allerod warm event c 14 5 cal ka bp subsequently ice at the southern tip of greenland readvanced during the younger dryas cold event in northern greenland the ice retreated rapidly from the continental shelf upon the climatic recovery out of the younger dryas to present day conditions upon entering the holocene 11 7 cal ka bp the ice sheet soon became land based during the holocene thermal maximum htm 9 5 cal ka bp air temperatures across greenland were marginally higher than those at present and the gris margin retreated inland of its present day southwest position by 40 60 km at 4 cal ka bp which produced a deficit volume of 0 16 m iesl relative to present in response to the htm warmth our optimal model reconstruction lost mass at a maximum centennial rate of c 103 4 gt yr our results suggest that remaining data model discrepancies are affiliated with missing physics and sub grid processes of the glaciological model uncertainties in the climate forcing lateral earth structure and non greenland ice particularly the north american component finally applying the huy3 greenland reconstruction with our optimal earth model we generate present day uplift rates across greenland due to past changes in the ocean and ice loads with explicit error bars due to uncertainties in the earth structure present day uplift rates due to past changes are spatially variable and range from 3 5 to 7 mm a including earth model uncertainty

calibrating a glaciological model of the greenland ice sheet from the last glacial maximum to present day using field observations of relative sea level and ice extent we constrain a three dimensional thermomechanical model of greenland ice sheet gris evolution from the last glacial maximum lgm 21 ka bp to the present day using primarily observations of relative sea level rsl as well as field data on past ice extent our new model huy2 fits a majority of the observations and is characterised by a number of key features i the ice sheet had an excess volume relative to present of 4 1 m ice equivalent sea level at the lgm which increased to reach a maximum value of 4 6 m at 16 5 ka bp ii retreat from the continental shelf was not continuous around the entire margin as there was a younger dryas readvance in some areas the final episode of marine retreat was rapid and relatively late c 12 ka bp leaving the ice sheet land based by 10 ka bp iii in response to the holocene thermal maximum htm the ice margin retreated behind its present day position by up to 80 km in the southwest 20 km in the south and 80 km in a small area of the northeast as a result of this retreat the modelled ice sheet reaches a minimum extent between 5 and 4 ka bp which corresponds to a deficit volume relative to present of 0 17 m ice equivalent sea level our results suggest that remaining discrepancies between the model and the observations are likely associated with non greenland ice load differences between modelled and observed present day ice elevation around the margin lateral variations in earth structure and or the pattern of ice margin retreat

holocene relative sea level changes in the inner bredefjord area southern greenland in this paper we present new relative sea level data from southern greenland a key area for understanding the greenland ice sheet gis response to climate change within fourteen lakes and marine lagoons from the inner part of bredefjord nordre sermilik in southern greenland isolations revealed by stratigraphic and palaeoecological analyses are dated and relative sea levels reconstructed due to coastal emergence caused by the gis retreat within the area the relative sea level fell rapidly in the early holocene between at least c 9600 and c 7300 cal yrs bp attaining a rate of 2 cm per year between 9600 and 8000 cal yrs bp spatial variability in relative sea level changes is show for southern greenland from a comparison with the nanortalik and the qagortoq areas the regression occurred about 2000 years later in the inner bredefjord area compared to the nanortalik area and about 1000 years later compared to the qaqortoq area this is a consequence of earlier deglaciation in areas located at the outer coast between c 8000 cal yrs bp and the present day relative sea level was lower than today the lowest relative sea level in the inner bredefjord area of between 5 4 and 15 m a h a t above highest astronomical tide was reached between 7000 and 1000 cal yrs bp the neoglacial readvance together with the collapse of the laurentide peripheral bulge is probably responsible for the transgression in the inner bredefjord area as has been indicated from the nearby sites qagortoq and nanortalik our relative sea level reconstructions showing spatial variability within southern greenland have implications for glacial isostatic adjustment gia modelling and the understanding of the gis ice sheet dynamics the early holocene regression is consistent with the recession of the southern sector of the gis from the shelf edge at c 22 000 cal yrs bp reaching inland of the present day outer coast by c 12 000 cal yrs bp and its present margin by c 10 500 cal yrs bp c 2013 elsevier ltd all rights reserved

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

global glacial isostasy and the surface of the ice age earth the ice 5g vm2 model and grace abstract the 100 kyr quasiperiodic variation of continental ice cover which has been a persistent feature of climate system evolution throughout the most recent 900 kyr of earth history has occurred as a consequence of changes in the seasonal insolation regime forced by the influence of gravitational n body effects in the solar system on the geometry of earth s orbit around the sun the impacts of the changing surface ice load upon both earth s shape and gravitational field as well as upon sea level history have come to be measurable using a variety of geological and geophysical techniques these observations are invertible to obtain useful information on both the internal viscoelastic structure of the solid earth and on the detailed spatiotemporal characteristics of glaciation history this review focuses upon the most recent advances that have been achieved in each of these areas advances that have proven to be central to the construction of the refined model of the global process of glacial isos

estimates of south greenland late glacial ice limits from a new relative sea level curve abstract marine lacustrine isolation contacts from seven basins in the nanortalik area south greenland have been analysed and dated the basins were isolated from the sea as a consequence of isostatic rebound following deglaciation the isolation contacts were identified with litho and biostratigraphical analyses especially sedimentary changes grey scale analyses and analyses of macroscopical remains of plants and animals dating was performed by analytical mass spectroscopy radiocarbon dating of macrofossils and bulk sediment samples a slow initial relative sea level fall that begins at 13 8 cal ka bp changes to a rapid relative sea level fall before the sea level fell below the present day sea level just prior to 10 cal ka bp the emergence curve goes further back in time than any previous emergence curve constructed from greenland which reflects the early deglaciation of the studied region the glacio isostatic crustal rebound following deglaciation was around 110 m the sea level history indicates that the margin of the greenland ice sheet probably extended out to the shelf margin during the last glacial maximum and that the ice thickness must have been at least 1500 m over the outer coast thus the highest coastal mountains would have been ice covered which is surprising given their alpine character in addition the major part of the recession of the ice must have occurred relatively late and quickly maybe from 14 to 12 cal ka bp the late holocene transgression may at least in part be due to increased isostatic loading as a consequence of advancing glaciers during the neoglaciation

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

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