the late devensian 22 000 bp irish sea basin the sedimentary record of a collapsed ice sheet margin the late devensian 20 ka bp glacial geology of the irish sea basin 4000 km2 is an event stratigraphy recording the entry of marine waters into a glacio isostatically depressed basin and the rapid retreat of the irish sea glacier as a tidewater ice margin marine limits occur up to 140 m o d across much of the central basin the ice margin was uncoupled from its bed exposing a subglacially scoured topography to glaciomarine processes the irish sea glacier was a major drainage conduit of the last british ice sheet calving of the marine ice margin resulted in fast flow surging of ice streams recorded by drumlin fields around the northern basin margin and tunnel valleys rapid evacuation of the basin may have stranded large areas of dead ice in peripheral zones e g cheshire shropshire lowlands and initiated the collapse of the ice sheet thick wedges of ice contact glaciomarine sediments were deposited during ice retreat as morainal bank complexes by successive tidewater ice margins stabilized at pinning points around the irish sea coast where morainal banks occur on the seaward side of drumlin swarms there is a clear sequential relationship between rapid ice loss from calving ice margins the development of fast flowing ice streams drumlinization and the pumping of subglacial sediment to tidewater raised delta complexes are locally associated with marine limits along the high relief coastal margins of wales east central ireland and the lake district associated valley infill complexes record downslope resedimentation of heterogenous sediments into the marine environment during ice retreat co eval offshore deposits are represented by well stratified glaciomarine complexes that infill a subglacially scoured topography that shows networks of tunnel valleys glaciomarine mud drapes occur well to the south of the maximum limit of grounded ice in the basin e g north devon scilly islands southern ireland the age of these distal sediments previously mapped as pre devensian tills is constrained by amino acid ratios basin rebound following deglaciation was rapid with over 100 m recovery in 3 ka and was followed by a low marine still stand peat accumulating in offshore areas now as much as 55 m below sea level has been drowned by the postglacial eustatic rise in sea level the glacio sedimentary model identified in this paper involving rapid ice retreat and related sedimentation triggered by rising relative sea level suggests that isotatic downwarping is an important mechanism for deglaciating continental shelves

the last british ice sheet a review of the evidence utilised in the compilation of the glacial map of britain this paper reviews the evidence presently available as at december 2003 for the compilation of the glacial map of britain see clark c d evans d j a khatwa a bradwell t jordan c j marsh s h mitchell w a bateman m d 2004 map and gis database of glacial landforms and features related to the last british ice sheet boreas 33 359 375 and http www shef ac uk geography staff clark chris britice html in an effort to stimulate further research on the last british ice sheet and promote a reconstruction of ice sheet behaviour based on glacial geology and geomorphology the wide range of evidence that has been scrutinized for inclusion on the glacial map is assessed with respect to the variability of its quality and quantity and the existing controversies in ice sheet reconstructions landforms interpreted as being of unequivocal ice marginal origin moraines ice contact glacifluvial landforms and lateral meltwater channels and till sheet margins are used in conjunction with available chronological control to locate former glacier and ice sheet margins throughout the last glacial cycle subglacial landforms drumlins flutings and eskers have been used to demarcate former flow patterns within the ice sheet the compilation of evidence in a regional map is crucial to any future reconstructions of palaeo ice sheet dynamics and will provide a clearer understanding of ice sheet configuration ice divide migration and ice thickness and coverage for the british ice sheet as it evolved through the last glacial cycle

rapid flooding of the sunda shelf a late glacial sea level record the increase in sea level from the last glacial maximum has been derived from a siliciclastic system on the tectonically stable sunda shelf in southeast asia the time from 21 to 14 thousand calendar years before the present has been poorly covered in other records the record generally confirms sea level reconstructions from coral reefs the rise of sea level during meltwater pulse 1a was as much as 16 meters within 300 years 14 6 to 14 3 thousand years ago

post glacial sea level rise from a coral record at huon peninsula papua new guinea dating of coral reef terraces can provide a record of changes in sea level which should be pronounced during the transition between glacial and interglacial periods cores drilled from coral reefs at barbados in the equatorial west atlantic1have revealed the sea level changes that occurred during the younger dry as event at the end of the last glacial maximum 11 000 yr bp it has not been known however whether pacific coral reefs can grow at a rate sufficient to keep up with the rise in sea level during such a transition here we report results obtained from a 52 m drill core from the post glacial reef at huon peninsula papua new guinea spanning the interval from 7 000 to 11 000 14c yr bp which show that coral growth kept pace while the relative sea level rose by 50m although the tectonic environment is very different from that at barbados the two records compare well when corrections are made for local tectonic uplift showing that sea level rise was similar at both locations the rate of rise was greatest between 9 000 and 10 00014c yr bp corresponding to the time of the younger dryas

a geotechnical correction for post depositional sediment compression examples from the forth valley scotland fine grained sediments usually suffer post depositional compression compaction which reduces bed thickness and lowers the elevations of sample positions and marker horizons this reduction has been calculated for two general cases using geotechnical theory and a correction decompaction factor is presented that can be applied to many field situations its use is illustrated by two examples from the clay sediments of the claret formation of the forth valley in the first the correction is calculated for 14c samples from the bothkennar research site near grangemouth and the effect on the reconstruction of water depths is discussed in the second example corrections are obtained for published sea level index points from former shorelines in the forth valley using a method for a postiori estimation of geotechnical data general conclusions are drawn between the size of the correction and the sample position relative to the local depocentre some applications to palaeotidal modelling are also suggested 1998 john wiley sons ltd

the present rate of uplift of fennoscandia implies a low viscosity asthenosphere the rate of displacement in fennoscandia has been intensively discussed for many years it is now widely accepted to be an isostatic response of the glacial history of the area the earth s present response to deglaciation in fennoscandia is simulated using a three dimensional 3d viscoelastic model in which the asthenosphere and mantle viscosity are allowed to vary so that the maximum rate of present uplift matches its observed value the deglaciation history is considered to be known and the c14 datings are converted to sidereal years the pattern of the present uplift gives a firm match with the observed data when a low viscosity asthenosphere is introduced assuming a 15 000 years load cycle i e the glacier was applied to the surface for 15 000 years before the melting started the best fitting earth viscosity model is a 1024 nm lithosphere overlying a 75 km thick 2 0 1019 pas asthenosphere and a 1 2 1021 pas mantle the simulations suggest a remaining maximum uplift of 40 m

the last glacial maximum in the north sea basin micromorphological evidence of extensive glaciation despite a long history of investigation critical issues regarding the last glacial cycle in northwest europe remain unresolved one of these refers to the extent timing and dynamics of late devensian weichselian glaciation of the north sea basin and whether the british and scandinavian ice sheets were confluent at any time during this period this has been the result of the lack of the detailed sedimentological data required to reconstruct processes and environment of sediments recovered through coring this study presents the results of seismic sedimentological and micromorphological evidence used to reconstruct the depositional processes of regionally extensive seismic units across the north sea basin thin section micromorphology is used here to provide an effective means of discriminating between subglacial and glacimarine sediments from cored samples and deriving process based interpretations from sediment cores on the basis of micromorphology critical formations from the basin have been reinterpreted with consequent stratigraphic implications within the current stratigraphic understanding of the north sea basin a complex reconstruction is suggested with a minimum of three major glacial episodes inferred on at least two occasions during the weichselian devensian the british and scandinavian ice sheets were confluent in the central north sea whilst micromorphology can provide much greater confidence in the interpretation of late quaternary offshore stratigraphic sequences it is noted that a much better geochronology is required to resolve key stratigraphic issues between the onshore and offshore stratigraphic records copyright 2006 john wiley sons ltd

icesat derived inland water surface spot heights accurate measurement of water surface height is key to many fields in hydrology and limnology satellite radar and laser altimetry have been shown to be useful means of obtaining such data where no ground gauging stations exist and the accuracy of different satellite instruments is now reasonably well understood past validation studies have shown water surface height data from the icesat instrument to have the highest vertical accuracy mean absolute errors of 10 cm for icesat compared for example with 28 cm from envisat yet no freely available source of processed icesat data currently exists for inland water bodies here we present a database of processed and quality checked icesat derived inland water surface heights iwsh for water bodies greater than 3 arc sec 92 m at the equator in width four automated methods for removing spurious observations or outliers were investigated along with the impact of using different water masks we find that the best performing method ensures that observations used are completely surrounded by water in the srtm water body data using this method for removing spurious observations we estimate transect averaged water surface heights at 587 292 unique locations from 2003 to 2009 with the number of locations proportional to the size of the river

the evolution of respiratory systems in theropoda and paracrocodylomorpha the end triassic extinction and the role of late triassic atmospheric o2 and co2 abstract during the late triassic period 235 201 3 ma paracrocodylomorpha and theropoda switched predatory roles with the former filling the subsidiary predator niche and the latter filling the top predator niche at the end triassic extinction reasons for the transition in predator guilds remain unknown but atmospheric conditions during this time which involved high co2 and low o2 concentration levels may be associated with the event evidence of bird like pneumatic post crania present in both groups as foramina and fossae correlates with an avian like respiratory system this may have allowed organisms to cope with declining atmospheric o2 environments of the late triassic this study estimated po2 throughout the late triassic using organic carbon isotope measurements from newark hartford basin paleosols and examined the morphological change in skeletal remains of theropoda focusing on pneumatic bones compared with paracrocodylomorpha during the late triassic and across the triassic jurassic boundary with data compiled from the paleobiology database and published anatomical literature the change of pneumaticity in taxa is quantified by a pneumatic index pi in which the number of pneumatized units is divided by the total number of bones examined patterns of pneumaticity are individually scored for the presence or absence of pneumatic bones morphological data are compared to corresponding femur length estimated atmospheric o2 and co2 level reconstructions and an ancestral state reconstruction depicting how pi values change throughout various clades our results suggest that pi values in theropoda and paracrocodylomorpha correspond with the vacillating po2 and pco2 throughout the late triassic and into the jurassic high pi values are prevalent in advanced theropod taxa while paracrocodylomorpha pi values vary by clade with a generally negative trend throughout the triassic ancestral state reconstruction analysis highlights the increasing pi values within theropoda and clade dependent trends in paracrocodylomorpha this study is instrumental in reconstructing how theropoda became evolutionarily successful and perhaps how and why the avian like respiratory system originated

rapid rise of sea level 19 000 years ago and its global implications evidence from the irish sea basin supports the existence of an abrupt rise in sea level meltwater pulse at 19 000 years before the present b p climate records indicate a large reduction in the strength of north atlantic deep water formation and attendant cooling of the north atlantic at this time indicating a source of the meltwater pulse from one or more northern hemisphere ice sheets warming of the tropical atlantic and pacific oceans and the southern hemisphere also began at 19 000 years b p these responses identify mechanisms responsible for the propagation of deglacial climate signals to the southern hemisphere and tropics while maintaining a cold climate in the northern hemisphere

late quaternary sea level changes crustal movements and coastal evolution in northumberland uk northumberland lies in the transition between holocene emergence and submerg ence and is thus a critical zone for testing models of isostatic rebound we have collected data from this area to reconstruct relative sea level changes and lateral coastline movements for the last 14000 y these are deposits from tidal marsh back barrier wetland and terrestrial environ ments producing 47 sea level index points from 12 sites there is no unequivocal evidence for late devensian sea levels above present and the reliable sea level index points are restricted between 26 m and 12 5 m relative to present and 9 0 2 5 kyr cal bp analysis of these quantifies differential responses to glacio and hydroisostatic rebound with the northern sites recording a mid holocene sea level maximum ca 2 5 m above present whereas the southern sites show a maximum ca 0 5 m above present these observations show a reasonable fit with the predictions from quantitative models of glacio and hydroisostatic rebound but there is currently no unique solution of earth and ice model parameters that will explain all the sea level observations copyright 2000 john wiley sons ltd

the melting history of the late pleistocene antarctic ice sheet spatial and temporal variations in the sea levels of the past 20 000 years around the globe place constraints on the melting history of the major late pleistocene ice sheets the antarctic ice sheets provided a significant contribution to the sea level rise at a rate that was approximately synchronous with the melting of the laurentide ice sheet except for the interval 9 000 6 000 years ago when it may have lagged behind minor melting of the antarctic ice sheet continued throughout the holocene

patterns of isostatic land uplift during the holocene evidence from mainland scotland preliminary results of a lengthy and detailed investigation into middle and late holocene raised shorelines in mainland scotland indicate that three shorelines are sufficiently widely distributed to permit an examination of their extent and of the patterns of uplift which they indicate the shorelines are the storegga tsunami shoreline reached at c 7100 14c years bp at the culmination of the main postglacial transgression and the blairdrummond shoreline reached after the main postglacial shoreline at c 2000 4200 14c years bp at the time of a tsunami believed to have been caused by the second storegga submarine slide the main postglacial shoreline reached at c 5800 6850 14c years bp the main postglacial shoreline previously believed to be the highest holocene raised shoreline in scotland is now believed to be overlapped around the periphery of the uplifted area by the later blairdrummond shoreline isobase models based upon quadratic trend surface analysis of available comparable height dat

estimating past continental ice volume from sea level data we predict sea level change since the last glacial maximum lgm at four far field sites barbados bonaparte gulf huon peninsula and tahiti using a revised theoretical formalism this formalism includes a time varying shoreline geometry an accurate treatment of sea level variations near regions of ice retreat and the influence of glacial cycle perturbations in earth rotation we elucidate the physics of far field sea level change by de constructing the predicted signal into spatially uniform versus spatially varying components as well as isolating contributions due to the ice load the ocean load and the rotational potential we demonstrate that the sum of these three contributions plus the spatially uniform sea level fall associated the with retreat of grounded marine ice sheets can produce a significant difference between predictions of sea level change at far field sites and the eustatic or meltwater curve associated with the adopted ice model this difference is site and time dependent for example the total sea level rise since the lgm predicted using our ice earth model can be either smaller e g barbados or larger e g tahiti than the eustatic sea level change finally we review procedures that have been applied to estimate continental ice volume from far field sea level observations and apply these procedures to data from barbados and bonaparte gulf applying an ice earth model that is tuned to fit the barbados data we estimate a change in grounded ice volume from the lgm to the present of 43 5 51 106 km3 based on barbados data and an lgm ice volume estimate of 51 106 km3 based on bonaparte gulf data our results for the bonaparte gulf data are consistent with the recent study by yokoyama et al nature 406 2000 713 these lgm ice volume estimates map into a eustatic or meltwater sea level rise of 115 135 m taking into account plausible variations in the adopted radial earth model introduces uncertainties in the range of 1 5 106 km3 for ice volume estimates based on the barbados data

quaternary glaciations in southern fennoscandia evidence from southwestern norway and the northern north sea region abstract based on records from the northern north sea and southern norway quaternary fennoscandian glaciations are described and discussed maximum glaciation defined as the presence of shelf edge glaciation an ice stream flowing out of the norwegian channel and most likely an ice divide over the central part of fennoscandia sweden gulf of bothnia occurred for the first time in the late cenozoic at ca 1 1 myr the fedje glaciation this glaciation was followed by a ca 600 kyr period with at least two glaciations with ice extension somewhat larger than the younger dryas event in the region the first maximum glaciation of the bruhnes chron was during isotope stage 12 and was followed by repeated maximum glaciations within each of the light isotopic stages until stage 2 during the weichselian the southwestern part of the fennoscandian ice sheet reached maximum position three times sometime between 22 and 28 37 and 50 and 60 and 80 ka limited glaciations probably occurred during stadials between the early and middle weichselian interstadials between 500 ka and 1 1 myr and most likely also prior to 1 1 myr deep norwegian sea ice rafted detritus ird records reflecting contributions from several different ice sheets fennoscandian barents sea iceland and greenland each with large variations in history of ice extent to their respective margins yet to some degree they reflect the glaciation of the northern north sea region with an increasing ird input around 1 1 myr and a relatively low input of north sea components during some cycles around the b m boundary maximum glaciations occurred during insolation minima in the earlier part of the middle pleistocene however not all such minima are reflected by maximum glaciation in southern parts of fennoscandia the relatively poor chronological control and non continuous character of the data on weichselian interstadials stadials precludes a clear relationship to atmospheric changes recorded in greenland ice cores as well as to precession and or obliquity cycles in insolation

on post glacial sea level i general theory summary modern analyses of sea level changes due to glacial isostatic adjustment gia are based on the classic sea level equation derived by farrell clark 1976 geophys j r astr soc 46 647 667 the connection between global sea level variations and changes to ocean height that is assumed within this equation breaks down in the presence of a time varying shoreline geometry we present a generalized sea level equation that overcomes this difficulty we also derive analytic expressions for and present schematic illustrations of the error in the ocean height change over finite time intervals introduced in published efforts to incorporate shoreline evolution into the theory of gia induced sea level change this comparison includes studies of shoreline migration due to either local sea level changes or the growth and ablation of marine based ice we conclude that the theories applied by johnston 1993 geophys j int 114 615 634 milne 1998 phd thesis university of toronto toronto and co workers are more accurate than the procedure advocated by peltier 1994 science 265 195 201 1998a geophys res lett 25 3955 3958 1998b rev geophys 114 615 634 although an improvement in the latter has recently been reported peltier drummond 2002 geophys res lett 29 10 1029 2001gl014273 our generalized theory is valid for any earth model in a companion paper we derive the equations necessary to treat the special case of a spherically symmetric linear viscoelastic and rotating earth and we quantify errors associated with previous work

the last ice sheet in north west scotland reconstruction and implications recent models of the last scottish ice sheet suggest that nunataks remained above the ice surface in areas peripheral to the main centres of accumulation this proposition has been investigated on 140 mountains over an area of 10 000 km2 in nw scotland outside the limits of the later loch lomond readvance in this area there is evidence for a single high level weathering limit that separates glacially eroded terrain from higher areas of in situ frost debris this limit occurs at altitudes ranging from 425 to 450 m in the outer hebrides to 950 m on the mainland and is best developed on lithologies that resisted breakdown after ice sheet downwastage interpretation of this weathering limit as a periglacial trimline cut by the last ice sheet at its maximum thickness is supported by 1 joint depth and schmidt hammer measurements that indicate significantly more advanced rock breakdown above the weathering limit 2 a much greater representation of gibbsite a pre late devensian weathering product in the clay fraction of soils above the limit 3 cosmogenic isotope dating of the exposure ages of rock outcrops above and below the limit 4 the sharpness of the limit at some sites and its regular decline along former ice flowlines and 5 shear stress calculations based on the inferred altitude and gradient of the former ice surface reconstruction of the ice surface based on trimline evidence indicates that the mainland ice shed lay near or slightly east of the present watershed and descended northwards from 900 m to ca 550 m at the north coast independent dispersion centres fed broad ice streams that occupied major troughs on skye an ice dome 800 m deflected the northwestwards movement of mainland ice but the mountains of rum were over ridden by mainland ice up to an altitude of ca 700 m the outer hebrides supported an independent ice cap that was confluent with mainland ice in the minches extrapolation of the trimline evidence indicates that most reconstructions of ice extent are too conservative and suggests that low gradient ice streams extended across the hebridean shelf offshore wider implications of this research are 1 that blockfields and other periglacial weathering covers are not all of the same age or significance depending on the resistance of different lithologies to frost weathering 2 that the contrasting degree of glacial modification in the western and eastern highlands of scotland may reflect a former cover of predominantly warm based ice in the former and predominantly cold based ice in the latter and 3 that the approach and techniques developed in this study have potential application for constraining ice sheet models not only in areas peripheral to the main centres of ice accumulation in britain and ireland but also in other mountain areas where nunataks protruded through warm based late pleistocene ice masses

sea level change glacial rebound and mantle viscosity fornorthern europe northwestern europe remains a key region for testing models of glacial isostasy because of the good geological record of crustal response to the glacial unloading since the time of the last glacial maximum models for this rebound and associated sea level change require a detailed knowledge of the ice sheet geometry including the ice thickness through time existing ice sheet reconstructions are strongly model dependent and inversions of sea level data for the mantle response may be a function of the model assumptions thus inverse solutions for the sea level data are sought that include both ice and earth model parameters as unknowns sea level data from fennoscandia the north sea the british isles and the atlantic and english channel coasts have been evaluated and incorporated into the solutions the starting ice sheet for fennoscandia is based on a reconstruction of a model by denton hughes 1981 that is characterized by quasi parabolic cross sections and symmetry about the load centre both global northwestern europe as a whole and regional subsets of the data solutions have been made for earth model parameters and ice height scaling parameters the key results are as follows 1 the response of the upper mantle to the changing ice and water loads is spatially relatively homogenous across scandinavia the north sea and the british isles 2 this response can be adequately modelled by an effective elastic lithosphere of thickness 65 85 km and by an effective upper mantle viscosity from the base of the lithosphere to the 670 km depth seismic discontinuity of about 3 4 1020 pa s the effective lower mantle viscosity is at least an order of magnitude greater 3 the ice thickness over scandinavia at the time of maximum glaciation was only about 2000 m much less than the 3400 m assumed in the denton hughes model 4 the ice profiles are asymmetric about the centre of the ice sheet with those over the western part being consistent with quasi parabolic functions whereas the ice heights over the eastern and southern regions increase much more slowly with distance inwards from the ice margin

electron spin resonance dating of the pleistocene coral reef tracts of barbados abstract the reef tracts of barbados have been investigated by electron spin resonance dating all parameters necessary for esr dating including effective efficiency and thermal stability were determined without cross checking with another independent dating method in addition some u series analyses were carried out in order to test the reliability of esr in most cases the results show a satisfactory agreement between esr and both these and previously published u series dates m l bender r g fairbanks f w taylor r k matthews j g goddard and w s broecker 1979 geological society of america bulletin 90 577 594 for the oldest samples esr dates tend to exceed he u dates suggesting that there might have been he loss from aragonite raised reef tracts are assigned to high sea stands from successive interglacial stages 5 7 9 11 13 and 15 esr and u series 230th 234u dates for corals and molluses in north barbados do not support the suggestion of n p james 1971 unpublished thesis mcgill university montreal that this region has subsided during part of the past 125 000 yr whereas the experimentally determined mean life of trapped electrons is only 500 000 yr for the ambient temperature in barbados there is no evidence from the comparison between esr and other dates for thermal fading this emphasizes the difficulty of experimental measurement of

relative sea level observations in western scotland since the last glacial maximum for testing models of glacial isostatic land movements and ice sheet reconstructions observations of relative sea level change and local deglaciation in western scotland provide critical constraints for modelling glacio isostatic rebound in northern britain over the last 18 000 years the longest records come from skye arisaig and knapdale with a shorter holocene record from kintail biostratigraphic diatom pollen dinoflagellate foraminifera and thecamoebian lithological and radiocarbon analyses provide age and elevation parameters for each sea level index point all four sites reveal relative sea level change that is highly non monotonic in time as the local vertical component of glacio isostatic rebound and eustasy or global meltwater influx dominate at different periods copyright 2006 john wiley sons ltd

on postglacial geoid subsidence over the equatorial oceans we develop two new spectral formalisms for the gravitationally self consistent solution of the sea level equation which governs the redistribution of glacial meltwater on a visco elastic earth the first is a purely spectral technique based on an extension of theory outlined by dahlen 1976 for determining the equilibrium oceanic tide on an elastic planet using this technique with a feasible spherical harmonic truncation level l 30 we can obtain convergence in the computed sea level variations within the degree range l 10 we also develop a second pseudospectral technique however which permits the construction of gravitationally self consistent solutions to much higher degree and order l 100 the pseudospectral formalism is employed here to develop a comprehensive physical explanation for the global pattern of present day sea level variations due to ongoing glacial isostatic adjustment in particular we focus upon a mechanism which we term equatorial ocean syphoning that acts to draw water toward the oceanic portion of the collapsing peripheral bulge that encircles previously glaciated regions the collapse of the forebulge induces a flow of water which is required to maintain hydrostatic equilibrium the syphoning mechanism dominates the relative sea level rsl variation in oceans in the far field of the ice sheets that is beyond the peripheral bulge during periods such as the interglacial of the past 4000 years during which the volume of the ice sheets has not apparently changed appreciably while at the same time isostatic adjustment persists the rsl change in the near field is in contrast dominated by the local vertical displacement of the solid surface finally comparison of gravitationally self consistent predictions of rsl change in the far field with the observational data at small pacific island sites has provided an upper bound of 1 to 2 m for the eustatic sea level rise produced by any recent last 3000 years melting of the antarctic ice sheet

glaciation and sea level change for ireland and the irish sea since late devensian midlandian time the sea level change around the coast of ireland and the irish sea for the past 20 000 years is primarily the combined result of the glacio isostatic adjustment of the crust to the removal of ice over the british isles and the total eustatic change from the global ice sheets however the isostatic effects due to the removal of ice from northern europe and north america and the addition of meltwater into the oceans also make a significant contribution predictions of sea level change based on glacio hydro isostatic models are compared with observations to constrain the ice volume over ireland at the time of the last glacial maximum and the maximum ice height appears to have been of the order of 600 m the models predict well the spatial variability in sea level change observed across the region for holocene and lateglacial time with levels above present being predicted only for northeastern ireland and north of about morecambe bay the models do not support suggestions that lateglacial levels along the east coast of ireland or the coast of wales were 50 150 m above their present levels consistent models that would produce such large lateglacial highstands are incompatible with all other sea level and glacial evidence for the british isles palaeobathymetry and palaeoshoreline reconstructions for the irish sea indicates that a tenuous landbridge between britain and ireland developed only across the celtic sea between about 18000 and 14000 years bp

holocene tides of the wash u k the influence of water depth and coastline shape changes on the record of sea level change abstract tidal simulations are conducted using a numerical model to investigate the relative influence of water depth and coastline shape changes on the holocene tides of the wash tidal input to this model is obtained by running a nested series of models commencing with a model of the northeast atlantic results of both types of simulations are compared with those of other simulations incorporating all the palaeogeographic information available on both past water depths and coastline shapes around the wash the model employs six harmonic tidal constituents to obtain mean high water of spring tides mhwst altitudes the wash was a depositional embayment during the holocene and results of model simulations are compared with sea level indicators in the stratigraphy which record past mhwst altitudes tidal simulations for water depths reduced by 2 5 and 10 m compared with present sea levels generally give lower tidal amplitudes around the wash than found at present mhwst altitudes simulating the coastline shape for 3000 4000 and 5000 yrs b p utilising present water depths show similar patterns of tidal changes to those obtained from the palaeogeographic simulations however reduced water depth tidal simulations accord more closely with the palaeogeographic simulation results in terms of the magnitude of changes to mhwst altitudes than the palaeocoastline simulations this is due to the fact that the rise in mean sea level during the holocene is far greater than any change in the amplitude of tides in the wash palaeogeographic simulation model results for mhwst agree within experimental errors with sea level curve altitudes reasons for discrepancies include inaccuracies in model parameters or measurement errors in obtaining mhwst altitudes from the stratigraphy overall tidal heights increase with sea level rise towards the present day alterations to coastline shape and non uniform water depth changes for example due to sediment movements or coastal defence schemes must be taken into consideration when assessing changes to the tidal regime for different sea levels in coastal embayments in order to determine both the pattern and magnitude of tidal changes this applies to both past and possible future tidal simulations

on eustatic sea level history last glacial maximum to holocene abstract this paper addresses the question of the magnitude and time dependence of the globally averaged eustatic rise of sea level that occurred subsequent to the time of last glacial maximum lgm at approximately 21 000 calendar years before present through the analysis of relative sea level rsl histories predicted by a realistic mass conserving and gravitationally self consistent theory of postglacial sea level change it is demonstrated that there are preferred oceanic locations at which this eustatic function is well approximated by local sea level history one such location is the island of barbados in the caribbean sea a site from which a coral based record exists that extends from mid holocene to lgm because of the sea level ambiguity that is inherent to coral based records however it is important that the global ice equivalent eustatic sea level curve inferred on the basis of the barbados data be tested against observations at other locations from which similarly extensive records are also available but which are derived on the basis of sea level indicators which are not subject to the ambiguities inherent to corals it is shown that when the eustatic function employed in the global theoretical model is tuned so as to enable the model to fit the barbados observations where the maximum relative sea level rsl depression is assumed to be near 120 m then the theory misfits the record from the sunda shelf in the indonesian archipelago as well as the record from j bonaparte gulf in northern australia both of these recently published records appear to constrain the lgm low stand of rsl to a value above 120 m the implications of these results for interpretation of the long coral derived records from the huon peninsula of papua new guinea and the island of tahiti are also discussed

glacial rebound and sea level change in the british isles observations of sea levels around the coastline of the british isles for the past 10 000 15 000 years exhibit a major regional variation and provide an important data base for testing models of glacial rebound as well as models of the late devensian ice sheet a high resolution rebound model has been developed which is consistent with both the spatial and temporal patterns of sea level change and which demonstrates that the observations are the result of i the glacio isostatic crustal rebound in response to the unloading of the ice sheet over britain and to a lesser degree of the ice sheet over fennoscandia and ii the rise in sea level from the melting late pleistocene ice sheets including the response of the crust to the water loading the hydro isostatic effect the agreement between model and observations is such that there is no need to invoke vertical crustal movements for great britain and ireland of other than glacio hydro isostatic origin the rebound contributions are important throughout the region and nowhere is it sufficiently small for the sea level change to approximate the eustatic sea level rise the observational data distribution around the periphery as well as from sites near the centre of the former ice sheet is sufficient to permit constraints to be established on both earth model parameters specifying the mantle viscosity and lithospheric thickness and the extent and volume of the ice sheet at the time of the last glaciation preliminary solutions are presented which indicate an upper mantle viscosity of 3 5 1020 pas a lithospheric thickness of about 100 km or less and an ice model that was not confluent with the scandinavian ice sheet during the last glaciation and whose maximum thickness over scotland is unlikely to have exceeded about 1500 m

a critical review of the glaciomarine model for irish sea deglaciation evidence from southern britain the celtic shelf and adjacent continental slope in support of their glaciomarine model for the deglaciation of the irish sea basin eyles and mccabe cited the occurrence of distal glaciomarine mud drapes onshore in the isles of scilly and north devon and of arctic beach face gravels and sands around the shores of the celtic sea glacial and sea level data from the southern part of the irish sea in the terminal zone of the ice stream and the adjacent continental slope are reviewed here to test this aspect of the model the suggestion that the glacial sequences of both the isles of scilly and fremington in north devon are glaciomarine mud drapes is rejected an actively calving tidewater margin only occurred early in the deglacial sequence close to the terminal zone in the south central celtic sea relative sea levels were lower and therefore glacio isostatic depression less than envisaged in the glaciomarine model geochronological sedimentological and biostratigraphical data indicate that the raised beach sequences around the shores of the celtic sea and english channel were deposited at or during regression soon after interglacial eustatic highstands evidence for ice rafting at a time of high relative sea levels is restricted to a phase s earlier than the late devensian these data indicate that the raised beach sequences have no bearing on the style of irish sea deglaciation copyright 2001 john wiley sons ltd

global to local scale parameters determining relative sea level changes and the post glacial isostatic adjustment of great britain abstract observations of relative sea level rsl change in great britain since 16 kyr bp and models of post glacial isostatic adjustment provide constraints on reconstructions of the british and antarctic ice sheets from the last glacial maximum to the present we use the global model from an earlier investigation modified ice 4g vm2 with lithospheric thickness 90 km which gives good rsl fits globally as well as for much of the british data a revised ice model for great britain that fits with recently published observations on ice limits and heights fails to explain all the misfits between rsl observations and predictions much more significant improvements result from models that incorporate a different chronology for the partial deglaciation of antarctica while keeping the total ice melt 17 m the same as in ice 4g vm2 the results suggest antarctic melting of 3 m ice equivalent sea level by 15 kyr bp only 1 m contribution to the 24 m rise of mwp1a with the major melting 12 5 kyr bp and a small amount of melting 1 0 0 3 m between then and 3 or 2 kyr bp these modifications produce rsl predictions for barbados that show the major changes in rate of sea level rise but with an offset up to 1 kyr compared to the observations possible explanations that remain to be investigated further are a delay in the melting of ice from some other region a reduction in the total melt derived from antarctica and a refinement of the 1 kyr temporal resolution assumed in the construction of the theoretical solution

modeling the contribution of m2 tidal amplification to the holocene rise of mean high water in the gulf of maine and the bay of fundy abstract increase in the m2 principal lunar semi diurnal component of the tidal range is an important contributor to the postglacial rise of the high tide level in the gulf of maine and the bay of fundy in addition to relative sea level rise the increase occurred as the shape of this semi enclosed embayment changed with sea level rise and its natural period approached resonance with the m2 tide a three dimensional tide model 3dens predicts the following m2 tidal ranges averaged for the gulf of maine bay of fundy as a percentage of the present range 54 59 at 7000 yrs b p 73 at 5000 yrs b p 78 at 4000 yrs b p 85 at 3000 yrs b p 94 at 2000 yrs b p and 98 at 1000 yrs b p with a predicted sea level rise of 0 15 0 90 m by the year 2100 m2 tidal range may increase 0 3 1 9

calibration of the c 14 timescale over the past 30 000 years using mass spectrometric u th ages from barbados corals uranium thorium ages obtained by mass spectrometry from corals raised off the island of barbados confirm the high precision of this technique over at least the past 30 000 years comparison of the u th ages with 14c ages obtained on the holocene samples shows that the u th ages are accurate because they accord with the dendrochronological calibration before 9 000 yr bp the 14c ages are systematically younger than the u th ages with a maximum difference of 3 500 yr at 20 000 yrbp the u th technique thus provides a way of calibrating the radiocarbon timescale beyond the range of dendrochronological calibration

ice sheet and solid earth influences on far field sea level histories previous predictions of sea level change subsequent to the last glacial maximum show significant systematic discrepancies between observations at tahiti huon peninsula and sunda shelf during lateglacial time 14 000 to 9000 calibrated years before the present we demonstrate that a model of glacial isostatic adjustment characterized by both a high viscosity lower mantle 4 1022 pa s and a large contribution from the antarctic ice sheet to meltwater pulse ia 15 meters eustatic equivalent resolves these discrepancies this result supports arguments that an early and rapid antarctic deglaciation contributed to a sequence of climatic events that ended the most recent glacial period of the current ice age

periglacial trimlines in the scottish highlands abstract two periglacial weathering limits have been identified on mountains in the highlands of scotland the lower has been interpreted as a periglacial trimline marking the upper limits of loch lomond younger dryas stade glaciers and has been employed to reconstruct the dimensions of parts of the main west highland icefield and certain smaller glaciers and icefields interpretation of the upper weathering limit has been more contentious but recent research has demonstrated 1 significant contrasts in the degree of bedrock weathering above and below this limit 2 that gibbsite a pre devensian weathering product is abundant above the limit but rare in soils farther downslope 3 that the isotopic 26al age of bedrock exposures above the limit greatly exceeds that at lower altitudes and 4 that the altitude of the weathering limit descends regularly along former ice sheet flowlines collectively these attributes suggest that the upper weathering limit is a periglacial trimline defining the maximum altitude of the last ice sheet calculated basal shear stress values are consistent with this interpretation which implies that the mainland ice shed lay at ca 900 m in wester ross and descended gently northwards whilst harris and lewis in the outer hebrides supported an independent ice cap that achieved a maximum altitude of ca 700 m wider implications of this interpretation and the future potential for ice sheet reconstruction are explored

sea level fingerprinting as a direct test for the source of global meltwater pulse ia the ice reservoir that served as the source for the meltwater pulse ia remains enigmatic and controversial we show that each of the melting scenarios that have been proposed for the event produces a distinct variation or fingerprint in the global distribution of meltwater we compare sea level fingerprints associated with various melting scenarios to existing sea level records from barbados and the sunda shelf and conclude that the southern laurentide ice sheet could not have been the sole source of the meltwater pulse whereas a substantial contribution from the antarctic ice sheet is consistent with these records

ams c 14 dating of deglacial events in the irish sea basin and other sectors of the british irish ice sheet sedimentary sequences deposited by the decaying marine margin of the british irish ice sheet biis record isostatic depression and successive ice sheet retreat towards centres of ice dispersion radiocarbon dating by accelerator mass spectrometry ams of in situ marine microfaunas that are commonly associated with these sequences constrain the timing of glacial and sea level fluctuations during the last deglaciation enabling us to evaluate the dynamics of the bus and its response to north atlantic climate change here we use our radiocarbon dated stratigraphy to define six major glacial and sea level events since the last glacial maximum 1 initial deglaciation may have occurred 18 3 kyr c 14 bp along the northwestern irish coast in agreement with a deglacial age of similar to 22 cl 36 kyr bp for southwestern ireland ice retreated to inland centres and areas of transverse moraine began to form across the north irish lowlands 2 channels cut into glaciomarine deglacial sediments along the western irish sea coast are graded to below present sea level identifying a fall of relative sea level rsl in response to isostatic emergence of the coast 3 marine mud that rapidly infilled these channels records an abrupt rise in global sea level of 10 15 m similar to 16 7 c 14 kyr bp that flooded the irish sea coast and may have triggered deglaciation of a marine based margin in donegal bay 4 intertidal boulder pavements in dundalk bay indicate that rsl similar to 15 0 c 14 kyr bp was similar to present 5 a major readvance of all sectors of the biis occurred between 14 and 15 kyr 14 c bp which overprinted subglacial transverse moraines and delivered a substantial sediment flux to tidewater ice sheet margins this event the killard point stadial indicates that the bus participated in heinrich event 1 6 subsequent deposition of marine muds on drumlins 12 7 c 14 kyr bp indicates isostatic depression and attendant high rsl resulting from the killard point readvance these events identify a dynamic biis during the last deglaciation as well as significant changes in rsl that reflect a combination of isostatic loading and eustatic changes in global sea level c 2005 elsevier ltd all rights reserved

analysis and interpretation of holocene sea level data the geography of the geoid1 and the lack of an acceptable methodology and definition of terms for sea level studies have impeded the realization of the objectives of the international geological correlation programme project 61 on holocene sea level changes2 these were to establish a graph of the trend of mean sea level over the globe and the relationship between sea level climate change and the global ice budget2 a solution to the problems of correlation is proposed here the use of terms transgression and regression has been a major cause of misinterpretation2 and the terms transgressive overlap and regressive overlap have been proposed as descriptive lithostratigraphic terms in which no process is implied3 5 the processes involved in the development of coastal stratigraphical sequences are dependent on the position and rate of change of sea level and these sequences contain evidence of tendencies of sea level6 8 the application of the concept of sea level tendency permits meaningful correlations between rising and subsiding areas and introduces an objectivity to correlation schemes showing transgression sequences 9 10

the vertical dimensions of late devensian glaciation on the mountains of harris and southeast lewis outer hebrides scotland on north harris and southeast lewis a weathering limit separates glacially moulded bedrock on low ground from frost shattered bedrock and blockfields on high plateaux analysis of the depths of horizontal stress release joints demonstrates significant contrasts in bedrock weathering above and below this boundary and the survival of gibbsite only in soils above the weathering limit indicates that it represents the upper limit of late devensian glacial erosion the weathering limit declines regularly in altitude on either side of the former ice shed and is therefore interpreted as a periglacial trimline defining the upper limit of a locally nourished ice mass at its maximum extent rather than a former thermal boundary between protective cold based and erosive warm based ice calculated basal shear stress values are consistent with this interpretation the configuration of the trimline indicates that at the last glacial maximum the area supported an ice cap that achieved a maximum altitude of ca 700 m above present sea level and declined in altitude to the west northwest and east southeast at an average gradient of ca 20 m km 1 extrapolation of the dimensions of this ice cap suggests that it terminated ca 7 10 km west of the present coast of harris and was confluent with mainland ice a short distance east of the present coastline

a 16 000 year record of near field relative sea level changes northwest scotland united kingdom abstract isolation basins raised tidal marshes coastal wetlands and dune systems around arisaig in northwest scotland produce a 16 000 year record of relative sea level rsl change from the time of local deglaciation following the last glacial maximum lgm to the present new sea level index points from mointeach mhor north define the culmination of the mid holocene rsl highstand to 7600 7400 cal yr bp and 6 74 0 2 m above present numerous sea level index points indicate that the rsl highstand persisted more than 1000 years before the onset of any significant rsl fall this points to a gradual cessation of melting of the laurentide and antarctic ice sheets rather than an abrupt termination isolation basin evidence from a marine limit 34 to 38 m above present down to sites close to current sea level constrain the acceleration of eustatic sea level rise during meltwater pulse 1a to 30 mm yr 1 or 11 km 3 yr 1 meltwater discharge comparison of rsl observations with glacial isostatic adjustment gia model predictions show differences in the pattern of residuals dependent upon the gia model used changes to the far field ice model components can partly explain the patterns of residuals

the stratigraphy of flandrian relative sea level changes at a site in tayside scotland peat deposits in a gully at the inland margin of the firth of tay carselands contain a transgressive wedge of estuarine sediments laid down at the culmination of the main postglacial transgression in previous work the sequence of deposits in the gully and their age have been examined at one location the present study both extends and evaluates that previous work employing further field work and laboratory analyses the detailed stratigraphy of the deposits is identified whilst from a borehole close to the limit of the transgressive deposit diatom analysis and geochemical analyses involving the determination of al mg c and 13cpdb are outlined eight 14c assays from peat at the transgressive and regressive contacts in four boreholes along the wedge of estuarine sediments are described whilst the results of diatom analysis are inconclusive the geochemical analyses indicate that the sediment accumulated broadly continuously without major changes in the depositional environment it is concluded that the main postglacial transgression in the gully was at first rapid then slowed and culminated between 6240 80 and 6030 80 or 6170 90 radiocarbon years b p it is subsequently maintained that the geochemical analyses described here may be of value in determining the continuity of transgressive deposits whilst the practice of obtaining multiple radiocarbon assays at such locations should enable assessment of age to be refined this may in turn assist in testing the hypothesis of shoreline diachroneity in glacioisostatically affected areas

timing of the last glacial maximum from observed sea level minima during the last glacial maximum ice sheets covered large areas in northern latitudes and global temperatures were significantly lower than today but few direct estimates exist of the volume of the ice sheets or the timing and rates of change during their advance and retreat here we analyze four distinct sediment facies in the shallow tectonically stable bonaparte gulf australia each of which is characteristic of a distinct range in sea level to estimate the maximum volume of land based ice during the last glaciation and the timing of the initial melting phase we use faunal assemblages and preservation status of the sediments to distinguish open marine shallow marine marginal marine and brackish conditions and estimate the timing and the mass of the ice sheets using radiocarbon dating and glacio hydroisostatic modelling our results indicate that from at least 22 000 to 19 000 calendar years before present land based ice volume was at its maximum exceeding today s grounded ice sheets by 52 5 x 10 exp 6 cu km a rapid decrease in ice volume by about 10 percent within a few hundred years terminated the last glacial maximum at 19 000 250 years

holocene land and sea level changes in great britain analysis of more than 1200 radiocarbon dated samples that constrain relative sea levels in great britain over the past 16 000 yr provides estimates of current land level changes negative of relative sea level change maximum relative land uplift occurs in central and western scotland ca 1 6 mm yr 1 and maximum subsidence is in southwest england ca 1 2 mm yr 1 sediment consolidation arising from autocompaction as the sediment accumulates and from land drainage increases the subsidence in areas with thick sequences of holocene sediments with an average effect equivalent to at least an extra ca 0 2 mm yr 1 land subsidence but more in parts of southeast england 0 5 1 1 mm yr 1 modelled changes in tidal range during the mid to late holocene in eastern england suggest that the calculated rate of land subsidence is overestimated unless such changes are quantified the effect is most significant for large coastal lowlands the fenland and humber ca 0 5 and 0 6 mm yr 1 that were tidal embayments during the mid to late holocene

relative sea level changes glacial isostatic modelling and ice sheet reconstructions from the british isles since the last glacial maximum while contributing 1 m equivalent eustatic sea level rise the british isles ice sheet produced glacio isostatic rebound in northern britain of similar magnitude to eustatic sea level change or global meltwater influx over the last 18 000 years the resulting spatially variable relative sea level changes combine with observations from far field locations to produce a rigorous test for quantitative models of glacial isostatic adjustment local ice sheet history and global meltwater influx after a review of the attributes of relative sea level observations significant for constraining large scale models of the isostatic adjustment process we summarise long records of relative sea level change from the british isles and far field locations we give an overview of different global theoretical models of the isostatic adjustment process before presenting intercomparisons of observed and predicted relative sea levels at sites in the british isles and far field for a range of earth and ice model parameters in order to demonstrate model sensitivity and the resolving power available from using evidence from the british isles for the first time we show a good degree of fit between relative sea level observations and predictions that are based upon global earth and ice model parameters independently derived from analysis of far field data with a terrain corrected model of the british isles ice sheet that includes extensive glaciation of the north sea and western continental shelf that does not assume isostatic equilibrium at the last glacial maximum and keeps to trimline constraints of ice surface elevation we do not attempt to identify a unique solution for the model lithosphere thickness parameter or the local scale detail of the ice model in order to provide a fit for all sites but argue that the next stage should be to incorporate an ice sheet model that is based on quantitative glaciological model simulations we hope that this paper will stimulate this debate and help to integrate research in glacial geomorphology glaciology sea level change earth rheology and quantitative modelling copyright 2006 john wiley sons ltd

sea level change in the irish sea since the last glacial maximum constraints from isostatic modelling models of glacio hydroisostatic sea level change have been published for the british isles that are broadly consistent with the observational evidence as well as with glaciological constraints it has been argued however that the models fail to represent sea level change along the irish sea margins and in southern ireland for the post deglaciation period the argument rests on the interpretation of the depositional environment of the elevated irish sea drift on both sides of the irish sea whether this is terrestrial or glaciomarine the isostatic models for the british isles are consistent with the former interpretation in that sea levels on either side of the irish sea south of about the isle of man are not predicted to have risen above present sea level at any time since the deglaciation of the irish sea this implies that ice over both the irish sea and ireland was relatively thin ca 600 700 m over ireland if the glaciomarine interpretation of the elevated irish sea drift is correct then the maximum ice thickness over central and southern ireland would have to reach 2000 m exceeding that over scotland furthermore for the resulting sea level change to be consistent with the holocene evidence this thick ice sheet could not have extended to the eastern side of the irish sea nor could it have been very thick at its northern and western limits if such an ice model is extreme and incompatible with glaciological observations then the alternative is to accept the interpretation of the irish sea drift as terrestrial in origin copyright 2001 john wiley sons ltd

flandrian sea level changes in the fenland ii tendencies of sea level movement altitudinal changes and local and regional factors stratigraphic micropalaeontologic and radiocarbon data show that since c 6500 bp the fenland has been influenced by 7 periods of positive sea level tendencies and by 6 periods of negative sea level tendencies despite the numerous problems associated with the reconstruction of past altitudes of sea level the periods of positive sea level tendencies were clearly characterised by a rise in sea level the development of transgressive overlaps and a landward movement of the coastline the periods of negative sea level tendencies were characterised by the development of regressive overlaps a seaward movement of the coastline and a reduced or negative rate of sea level rise the various altitudinal errors do not permit the incontrovertible distinction of periods of falling sea levels all changes within the fenland were not synchronous and local factors influenced the exact nature of each sea level indicator dominant regional and local factors have been identified for different areas and different time periods the chronological and spatial characteristics of the sequences within the fenland are best explained by a palaeocoastline without supratidal barriers controlling sedimentation the data indicate an average crustal subsidence in the fenland of 0 9m 1000 years since c 6500 bp and the pattern of positive and negative tendencies of sea level movement is also seen in the chronologies for north west england and north east scotland