a low order model of the heinrich event cycle if heinrich events result from free oscillations in the size and basal melting conditions of the laurentide ice sheet a rigorous quantitative analysis of ice sheet physics should describe their dynamics to explore this possibility i exploit two characteristic timescales which arise from ice sheet physics to construct a relaxation oscillator model of the north atlantic s heinrich events the numerical implementation of this model confirms the notion that the periodicity of heinrich events approximately 7 000 years is determined by the gross properties of a steady glacial climate e g an annual average sea level temperature of 10 c and an adiabatic lapse rate

the mutual interaction between continental scale ice sheets and atmospheric stationary waves the great continental ice sheets of the pleistocene represented significant obstacles to the northern hemisphere midlatitude westerlies they must therefore have forced large changes in the atmospheric circulation and consequently also in the patterns of accumulation and melting over the ice sheets themselves a simplified threedimensional coupled ice sheet stationary wave model is developed in order to understand the ice sheet s response to the circulation changes that it induces consistent with ice age climate simulations the ice sheet topography induces an anticyclonic circulation over the ice sheet causing a slight warming over the western slopes and a stronger cooling over the remainder the modeled feedbacks significantly affect the ice sheet configuration with the most important influences being the patterns of summer temperature and the topographically induced precipitation field the time evolution of the ice sheet is also changed by the atmospheric feedbacks and the results suggest the possibility of multiple equilibrium solutions

modeling precipitation over ice sheets an assessment using greenland the interaction between ice sheets and the rest of the climate system at long time scales is not well understood and studies of the ice ages typically employ simplified parameterizations of the climate forcing on an ice sheet it is important therefore to understand how an ice sheet responds to climate forcing and whether the reduced approaches used in modeling studies are capable of providing robust and realistic answers this work focuses on the accumulation distribution and in particular considers what features of the accumulation pattern are necessary to model the steady state response of an ice sheet we examine the response of a model of the greenland ice sheet to a variety of accumulation distributions both observational datasets and simplified parameterizations the predicted shape of the ice sheet is found to be quite insensitive to changes in the accumulation the model only differs significantly from the observed ice sheet for a spatially uniform accumulation rate and the most important factor for the successful simulation of the ice sheet s shape is that the accumulation decreases with height according to the ability of the atmosphere to hold moisture however the internal ice dynamics strongly reflects the influence of the atmospheric circulation on the accumulation distribution

the thermomechanical response of the greenland ice sheet to various climate scenarios using a three dimensional numerical model for land based ice sheets in the shallow ice approximation simulations are performed to determine the velocity and temperature distributions within the greenland ice sheet through time for various climate scenarios the ice is treated as a rheologically nonlinear heat conducting viscous fluid and the substrate is a heat conducting rigid solid this system is fed from above by prescribing as the climatic inputs the atmospheric temperature and the accumulation ablation rate functions at the free surface and from below by the geothermal heat we present the governing equations in the shallow ice approximation discuss the parameterizations used in the descriptions of the ice surface temperature and accumulation ablation functions briefly state how the complicated initial boundary value problem is numerically solved and how the input data that are available from measurements are implemented results of preliminary calculations disclose how the model performs and delimit its validity we study the role played by basal sliding and make clear that sliding should be accounted for where ever the basal ice is temperate and that the frictional heat generated in this sliding is thermomechanically significant we also study the reaction of the greenland ice sheet to various climate scenarios and make clear that today s thermal regime depends significantly upon the prior climate history moreover the thermomechanical properties of the ice are equally significant as is the thermal interaction of the ice sheet with the rockbed beneath

re evaluation of paleo accumulation parameterization over northern hemisphere ice sheets during the ice age examined with a high resolution agcm and a 3 d ice sheet model

application of a polythermal three dimensional ice sheet model to the greenland ice sheet response to steady state and transient climate scenarios abstract steady state and transient climate change computations are performed with the author s three dimensional polythermal ice sheet model simulation code for polythermal ice sheets for the greenland ice sheet the distinctive feature of this model is the detailed consideration of the basal temperate ice layer in which the water content and its impact on the ice viscosity are computed its transition surface to the cold ice region is accounted for by continuum mechanical jump conditions on this interface the simulations presented include steady states subject to a range of physical parameters and two different climates present and glacial conditions as well as three types of transient scenarios namely i sinusoidal milankovic period forcing ii paleoclimatic forcing from the greenland ice core project core reconstruction and iii future greenhouse warming forcing

liquid release tests in unsaturated fractured welded tuffs i field investigations wetting front movement flow field evolution and drainage of fracture flow paths were evaluated within the topopah spring welded tuff at yucca mountain nevada equipment and techniques were developed for in situ quantification of formation intake rates flow velocities seepage rates and volumes of fracture flow paths localized injections of liquid into a low permeability zone lpz and a high permeability zone hpz along a borehole were detected in two boreholes below the point of injection for the lpz tests water did not seep into an excavated slot that defined the lower boundary of the test bed and the liquid intake rate under constant head conditions was observed to steadily decrease by two orders of magnitude in the hpz liquid intake rates under constant head conditions were significantly higher and did not exhibit a strong systematic decline hpz tests were also conducted under a range of constant flow conditions slot seepage rates showed intermittent responses and the percentage of injected water recovered in the slot increased as each test progressed a maximum of 80 of the injected water was recovered during high rate injection tests the flow path volumes were found to increase during the course of each hpz test the data collected during these field tests has provided useful information for developing an understanding of liquid flow in unsaturated fractured welded tuff it has also provided a basis for quantitative comparisons with numerical simulations of liquid release experiments as demonstrated in a companion paper j hydrol 256 2002

precipitation over greenland retrieved by a dynamic method and its relation to cyclonic activity abstract in order to calculate the vertical motion over some high mountain regions such as greenland an equation without the quasigeostrophic approximation in coordinates has been developed a dynamic method for retrieving precipitation over greenland is based on this equation the retrieved annual mean precipitation distribution for 1987 and 1988 is in very good agreement with the observed annual accumulation pattern over the greenland ice sheet the major weather system producing precipitation over greenland is the frontal cyclone based on the precipitation characteristics greenland can be divided into five subregions precipitation over the north coastal and central interior regions primarily occurs in summer for the three other subregions if the composite monthly mean sea level pressure charts for high and low monthly precipitation amounts are constructed a clear relationship between precipitation and cyclonic activity emerges if a mean cyclone exists in the labrador sea heavy precipita

orographic precipitation and the relief of mountain ranges 1 the influence of climate on the relief of mountain ranges has long been supposed but has received little quantitative investigation the simplified system of a longitudinal river profile in a bedrock channel coupled to a physically based model of orographic precipitation is used to explore how orographically influenced patterns of precipitation affect the relief of fluvially sculpted mountain ranges it is shown that the impact on the orography depends on the nature of the precipitation regime significant changes in relief also occur for imposed temperature changes of realistic magnitude although the ability of the relief to respond to any given change depends sensitively on its response time and the timescale of the forcing

vapor phase transport in the near drift environment at yucca mountain 1 a key issue regarding the performance of the potential high level radioactive waste repository at yucca mountain nevada is the likelihood of precipitation percolating a vertical distance of 300 m through fractured unsaturated rock into drifts containing waste packages water enhances waste package corrosion and is required for transport of released radionuclides to evaluate the propensity for seepage into tunnels at yucca mountain a 5 m diameter 2 7 km long tunnel commonly referred to as the cross drift cd was excavated in 1998 branching off from the main exploratory studies facility tunnel sections of this tunnel have been isolated from ventilation for extended periods over the last 4 years we present continuous measurements of relative humidity and temperature and periodic observations of liquid water in the cd over two periods during this observation duration the terminal section of the drift was partitioned into four sections by bulkheads and ventilation to these sections was minimized to a few days we compare these observations to results from analytical and numerical models to investigate processes associated with the movement of water vapor between the tunnel bore and the surrounding fractured rock formation observations from this effort indicate that fractures can be primary paths for unsaturated zone vapor flow in the immediate vicinity of emplacement drifts observations measurements and analysis indicate the need for a model that includes fracture dominated vapor transport as a significant contributor to total water flow into the drifts

small scale convection in the subduction zone mantle wedge abstract small scale convection in the upper mantle can appreciably influence large scale mantle dynamics and has important implications for geophysical observables such as seismic anisotropy and surface heat flow we develop numerical models to evaluate the likelihood of small scale convection in the mantle wedge above subducting slabs the characteristics of small scale convection are analyzed using the 3 d single mode approximation in which one characteristic wavenumber represents small scale convective motions with rotational axes parallel to the convergence direction numerical simulations are run for a range of characteristic wavenumbers rayleigh numbers and subduction parameters e g slab dip angle convergence velocity and downgoing plate age for each simulation we quantify the excitation due to small scale convection and determine under what conditions and characteristic wavenumbers this excitation is maximized we find that of the parameters examined mantle wedge viscosity plays the most significant role in dictating the occurrence and strength of small scale convective motions in the mantle wedge numerical models run with subduction parameters similar to that of northeast japan where it has been proposed that small scale convection may be occurring in the mantle wedge require a mantle wedge viscosity of 10 18 pa s for significant small scale convection to occur

sensitivity of a greenland ice sheet model to ice flow and ablation parameters consequences for the evolution through the last climatic cycle sensitivity experiments are conducted to test the influence of poorly known model parameters on the simulation of the greenland ice sheet by means of a three dimensional numerical model including the mechanical and thermal processes within the ice two types of experiments are performed steady state climatic conditions and simulations over the last climatic cycle with a climatic forcing derived from the grip record the experiments show that the maximum altitude of the ice sheet depends on the ice flow parameters deformation and sliding law coefficients geothermal flux and that it is low when the ice flow is fast on the other hand the maximum altitude is not sensitive to the ablation strength and consequently during the climatic cycle it is driven by changes in accumulation rate the ice sheet extension shows the opposite sensitivity it is barely affected by ice flow velocity and the ice covered area is smaller for large ablation coefficients for colder climates when there is no ablation the ice sheet extension depends on the sea level an interesting result is that the variations with time of the altitude at the ice divide summit do not depend on the parameters we tested the present modelled ice sheets resulting from the climatic cycle experiments are compared with the present measured ice sheet in order to find the set of parameters that gives the best fit between modelled and measured geometry it seems that compared to the parameter set most commonly used higher ablation rate coefficents must be used

steady state characteristics of the greenland ice sheet under different climates the greenland ice sheet is modelled to simulate its extent and volume in warmer climates and also to find out whether the ice sheet would re form on theice free bedrock under present climatic conditions the ice sheet model is a three dimensional thermo mechanical model with a fine resolution grid thebedrock surface beneath the ice sheet was mapped using radio echo sounding measurements by the electromagnetic institute copenhagen the modelexperiments show that increased temperature will result in ice margin retreat but the ice sheet is relatively stable it takes a rather high temperature rise of atleast 6ic for the ice sheet to disappear completely which indicates that the ice sheet probably survived the last interglacial also it appears that the greenlandice sheet is not a mere relict ice mass from a previously colder climate but that the ice sheet will still re form on the bare bedrock under the present or evenslightly warmer climatic conditions

evolution of the conceptual model of unsaturated zone hydrology at yucca mountain nevada abstract yucca mountain is an arid site proposed for consideration as the united states first underground high level radioactive waste repository low rainfall approximately 170 mm yr and a thick unsaturated zone 500 1000 m are important physical attributes of the site because the quantity of water likely to reach the waste and the paths and rates of movement of the water to the saturated zone under future climates would be major factors in controlling the concentrations and times of arrival of radionuclides at the surrounding accessible environment the framework for understanding the hydrologic processes that occur at this site and that control how quickly water will penetrate through the unsaturated zone to the water table has evolved during the past 15 yr early conceptual models assumed that very small volumes of water infiltrated into the bedrock 0 5 4 5 mm yr or 2 3 percent of rainfall that much of the infiltrated water flowed laterally within the upper nonwelded units because of capillary barrier effects and that the remaining water flowed down faults with a small amount flowing through the matrix of the lower welded fractured rocks it was believed that the matrix had to be saturated for fractures to flow however accumulating evidence indicated that infiltration rates were higher than initially estimated such as infiltration modeling based on neutron borehole data bomb pulse isotopes deep in the mountain perched water analyses and thermal analyses mechanisms supporting lateral diversion did not apply at these higher fluxes and the flux calculated in the lower welded unit exceeded the conductivity of the matrix implying vertical flow of water in the high permeability fractures of the potential repository host rock and disequilibrium between matrix and fracture water potentials the development of numerical modeling methods and parameter values evolved concurrently with the conceptual model in order to account for the observed field data particularly fracture flow deep in the unsaturated zone this paper presents the history of the evolution of conceptual models of hydrology and numerical models of unsaturated zone flow at yucca mountain nevada flint a l flint l e kwicklis e m bodvarsson g s fabryka martin j m 2001 hydrology of yucca mountain reviews of geophysics in press this retrospective is the basis for recommendations for optimizing the efficiency with which a viable and robust conceptual model can be developed for a complex site

seepage into an underground opening constructed in unsaturated fractured rock under evaporative conditions 1 liquid release tests performed in boreholes above an underground opening constructed in unsaturated fractured rock are used in this study to evaluate seepage into a waste emplacement drift evidence for the existence of a capillary barrier at the ceiling of the drift is presented based on field observations including spreading of the wetting front across the ceiling and water movement up fractures exposed in the ceiling before seepage begins the capillary barrier mechanism has the potential to divert water around the opening resulting in no seepage when the percolation flux is at or below the seepage threshold flux liquid release tests are used to demonstrate that a seepage threshold exists and to measure the magnitude of the seepage threshold flux for three test zones that seeped the seepage data are interpreted using analytical techniques to estimate the test specific strength of the rock capillary forces 1 that prevent water from seeping into the drift evaporation increases the seepage threshold flux making it more difficult for water to seep into the drift and producing artificially inflated 1 values with adjustments for evaporation the minimum test specific threshold is 1600 mm yr with a corresponding 1 value of 0 027 m

terminating the 100 kyr ice age cycle we report a simulation of the most recent 100 000 year glaciationdeglaciation cycle of the late pleistocene ice age a simulation that delivers an ice sheet chronology that is in close accord with that inferred from the geological record our analyses are performed with a reduced model of the climate system that incorporates significant improvements to the representation of both climate forcing and mass balance response in a previously described theory based upon a coupled one level energy balance model ebm and vertically integrated ice sheet model ism the theory fully incorporates the influences of orbital insolation forcing glacial isostatic adjustment and variations in the atmospheric concentrations of greenhouse gases it correctly predicts the main geographical regions of the northern hemisphere that were glaciated at last glacial maximum 21 000 years ago as well as the abrupt termination of the glacial epoch that occurred subsequently the latter feature of the ice age cycle is obtained without the need to incorporate unconstrained and therefore controversial physical processes into the model a limitation of all previous attempts to understand this global scale climate cycle our analyses suggest that the radiative impact on surface glaciation due to the changing atmospheric concentration of co2 is critical to the ability of the model to deliver a synthetic history of glaciation and deglaciation that is in accord with inferences based upon surface geological and geomorphological evidence with the incorporation of this influence model predicted ice thickness distributions at last glacial maximum lgm are very similar to those of the recently described ice 4g reconstruction that was based upon the inversion of postglacial relative sea level histories

unsaturated flow and transport through a fault embedded in fractured welded tuff 1 to evaluate the importance of matrix diffusion as a mechanism for retarding radionuclide transport in the vicinity of a fault located in unsaturated fractured rock we carried out an in situ field experiment in the exploratory studies facility at yucca mountain nevada this experiment involved the release of 82 000 l of water over a period of 17 months directly into a near vertical fault under both constant positive head at 0 04 m and decreasing fluxes a mix of conservative tracers pentafluorobenzoic acid pfba and bromide applied in the form of lithium bromide was released along the fault over a period of 9 days 7 months after the start of water release along the fault as water was released into the fault seepage rates were monitored in a large cavity excavated below the test bed after the release of tracers seepage water was continuously collected from three locations and analyzed for the injected tracers observations of bromide concentrations in seepage water during the early stages of the experiment and bromide and pfba concentrations in the seepage water indicate the significant effects of matrix diffusion on transport through a fault embedded in fractured welded rock

unsaturated seepage and subterranean holes conspectus and exclusion problem for circular cylindrical cavities this paper introduces the general theory of water exclusion from or entry into subterranean holes from steady uniform downward unsaturated seepage buried holes serve as obstacles to the flow and so increase water pressure at parts of the hole surface when downward seepage is fast enough and or the hole is large enough water pressure increases to the point where a seepage surface forms and water enters the hole contrary to the conventional picture drawn from capillary statics hydrodynamics shows that the larger the hole the more vulnerable it is to water entry cavity shape is important also applications include optimal design of configurations of tunnels and underground repositories e g for nuclear wastes against entry of seepage water the theory also embraces the disturbance of seepage flows by buried impermeable obstacles such as stones and structures the quasi linear exclusion problem for circular cylindrical cavities is solved both exact solutions and simple asymptotic results are found and graphs and tables presented the moisture field about the cavity exhibits upstream and downstream stagnation points and retarded regions roof drip lobes in which the moisture content and downward flow velocity are augmented by water essentially deflected from the cavity roof and the dry shadow region of reduced moisture content and flow velocity essentially sheltered by the cavity a practical consequence is that we can establish for any given combination of downward seepage velocity cavity radius saturated hydraulic conductivity k1 and sorptive number whether or not seepage water will enter a cylindrical cavity

critical form and feedbacks in mountain belt dynamics role of rheology as a tectonic governor 1 the rheology that governs deformation within a convergent orogen also controls its topographic form or in other words the covaration of its height or thickness and its width under conditions pertaining to small orogens and for rheologies ranging from linear viscous to coulomb plastic we show that this topographic form is insensitive to the distributions of fluxes into and out of the wedge and is thus a fundamental property of the system it can therefore be thought of as a critical topographic form directly analogous to the well studied case of a coulomb plastic rheology which predicts a constant critical taper angle independent of its size the tendency of the system to evolve toward a critical topographic form can be regarded as a tectonic governor that strongly damps the response of the orogen to changes in climate or tectonic forcing scaling relationships can be derived for the variation of orogen width height and exhumation rate as a function of accretionary flux and precipitation rate this study explores how sensitive these scaling relationships are to the assumed rheology it is found that the scaling relationships vary by less than a factor of 2 across the range of typical geological rheologies from coulomb friction to power law viscous to linear viscous these scaling relationships provide a first order representation of the behavior of convergent wedges and are relatively insensitive to the underlying assumptions

hydrologic mechanisms governing fluid flow in a partially saturated fractured porous medium in contrast to the saturated zone within which fluid moves rapidly along fractures the fractures with apertures large relative to the size of matrix pores will desaturate first during the drainage process and the bulk of fluid flow would be through interconnected pores in the matrix within a partially drained fracture the presence of a relatively continuous air phase will produce practically an infinite resistance to liquid flow in the direction parallel to the fracture the residual liquid will be held by capillary force in regions around fracture contact areas where the apertures are small normal to the fracture surfaces the drained portion of the fractures will reduce the effective area for liquid flow from one matrix block to another matrix block a general statistical theory is constructed for flow along the fracture and for flow between the matrix blocks to the fractures under partially saturated conditions results are obtained from an aperture distribution model for fracture saturation hydraulic conductivity and effective matrix fracture flow areas as functions of pressure the effects of distortion of flow paths by the air pockets are taken into account by a phase separation constriction factor in a generalized cubic law for fracture flow under a partially saturated condition the reduction of matrix fracture flow area is taken into account by summing the aperture distribution function to a saturation cutoff aperture which is inversely proportional to the suction head drainage from a column of fractured tuff is simulated using available parameters for the densely welded tuff of the topopah spring member at yucca mountain southern nevada the column is bounded by discrete vertical fractures and dissected by horizontal fractures with the fracture spacings determined by the frequencies and orientations of fractured cores the fraction of fracture surfaces with coatings is assumed to correspond to the fraction of in situ fracture contact area the characteristic curves for the matrix are based on laboratory measurements of tuff samples from the cases simulated for the fractured porous columns with discrete vertical and horizontal fractures and porous matrix blocks explicitly taken into account it is observed that the highly transient changes from fully saturated conditions to partially saturated conditions are extremely sensitive to the fracture properties however the quasi steady changes of the fluid flow of a partially saturated fractured porous system could be approximately simulated without taking the fractures into account

northern hemisphere storm tracks in present day and last glacial maximum climate simulations a comparison of the european pmip models abstract extratropical weather systems are an essential feature of the midlatitude climate and global circulation at the last glacial maximum lgm the formation of regions of high transient activity referred to as storm tracks is strongly affected by the presence of large ice sheets over northern america and scandinavia and by differences in sea surface temperature sst distributions in the framework of the palaeoclimate modelling intercomparison project simulations of the lgm climate have been run with a wide range of atmospheric general circulation models agcms using the same set of boundary conditions allowing a valuable comparison between simulations of a climate very different from the present one in this study the authors focus on the storm track representation in the models and its relationship with the surface temperatures the mean flow and the precipitation storm tracks are described using transient eddy diagnostics such as mean sea level pressure variance and three dimensional

evaluation of recent precipitation studies for greenland ice sheet the retrieval of an accurate spatial and temporal record of contemporary greenland precipitation is a uniquely challenging task because of the extreme variability in both atmospheric processes and the resulting precipitation distribution over relatively small spatial scales a comparison of precipitation data sets composed of monthly mean values from recent studies shows a convergence on the general features of the long term spatial patterns but substantial disagreement on the temporal variability both regionally and for all of greenland there is general agreement on a long term greenland average of about 35 cm yr 1 and on long term values for regional scales although differences for outlying data sets exceed 50 of the observed glaciological estimate for particular regions a fundamental problem is the inadequate topographic representation of greenland in the numerical analyses nearly all of the data sets are overly dry for high elevation areas as seen from comparisons with glaciological observations from summit the east central region of greenland is found to be particularly susceptible to the temporal discontinuities in data sets which employ operational analyses in contrast there is strong agreement among all methods on the temporal variability for the west central region over a 15 year period from the comparison it is concluded that none of the data sets is able to capture all of the regional scale features in general however the deficiencies of each data set are readily identifiable from comparison and evaluation in the context of circulation features agreement among the methods on particular regions and timescales gives increased confidence in drawing conclusions related to aspects of greenland s precipitation climatology in particular an enhanced precipitation retrieval method is found to be less susceptible to data artifacts than other methods using operational analyses in the north anomalously high precipitation is associated with cyclonic development near the fram strait for west central greenland the close agreement among methods is related to the dominant contribution of the mean circulation

evidence for general instability of past climate from a 250 kyr ice core record recent results1 2 from two ice cores drilled in central greenland have revealed large abrupt climate changes of at least regional extent during the late stages of the last glaciation suggesting that climate in the north atlantic region is able to reorganize itself rapidly perhaps even within a few decades here we present a detailed stable isotope record for the full length of the greenland ice core project summit ice core extending over the past 250 kyr according to a calculated timescale we find that climate instability was not confined to the last glaciation but appears also to have been marked during the last interglacial as explored more fully in a companion paper3 and during the previous saale holstein glacial cycle this is in contrast with the extreme stability of the holocene suggesting that recent climate stability may be the exception rather than the rule the last interglacial seems to have lasted longer than is implied by the deep sea specmap record4 in agreement with other land based observations5 6 we suggest that climate instability in the early part of the last interglacial may have delayed the melting of the saalean ice sheets in america and eurasia perhaps accounting for this discrepancy

new precipitation and accumulation maps for greenland annual total precipitation and the annual accumulation on the greenland ice sheet are evaluated and presented in two maps the maps are based on accumulation measurements of 25 1 pits and cores obtained from the upper accumulation zone and precipitation measurements made at 35 meteorological stations in the coastal region to construct the accumulation map the annual precipitation was split into solid and liquid precipitation components annual total precipitation exceeding 2500 mm w e occurs on the southeastern tip of greenland while the minimum precipitation is estimated to occur on the northeastern slope of the ice sheet the mean annual precipitation for all of greenland is 340 mm w e the largest annual accumulation of about 1500 mm w e is found on the glaciers in the southeastern corner of greenland while the smallest accumulation is found on the northeastern slope of the ice sheet west of danmarkshavn the mean accumulation on the greenland ice sheet is estimated at 310 mm w e the regional difference in accumulation is examined with respect to the 850 hpa m bar level circulation the present surface topography is found to play an important role in determining regional accumulation on the ice sheet

substantial contribution to sea level rise during the last interglacial from the greenland ice sheet during the last interglacial period the eemian global sea level was at least three metres and probably more than five metres higher than at present1 2 complete melting of either the west antarctic ice sheet or the greenland ice sheet would today raise sea levels by 6 7 metres but the high sea levels during the last interglacial period have been proposed to result mainly from disintegration of the west antarctic ice sheet3 with model studies attributing only 1 2 m of sea level rise to meltwater from greenland4 5 this result was considered consistent with ice core evidence4 although earlier work had suggested a much reduced greenland ice sheet during the last interglacial period6 here we reconsider the eemian evolution of the greenland ice sheet by combining numerical modelling with insights obtained from recent central greenland ice core analyses our results suggest that the greenland ice sheet was considerably smaller and steeper during the eemian and plausibly contributed 4 5 5 m to the sea level highstand during that period we conclude that the high sea level during the last interglacial period most probably included a large contribution from greenland meltwater and therefore should not be interpreted as evidence for a significant reduction of the west antarctic ice sheet