holocene sea level changes in the indo pacific holocene sea level reconstructions exist from many locations in the indo pacific region despite being a large geographical region the nature of holocene sea level change is broadly similar in all locations differences do exist however in the timing and magnitude of the mid holocene high stand mhhs and the nature of late holocene sea level fall across the region when the indo pacific is subdivided into smaller regions these discrepancies do not disappear and in some cases the discrepancies are large within a single coastline it is clear from this analysis that the fundamental criteria to produce accurate local relative sea level curves are hardly ever met there are serious problems associated with the correct interpretation of sea level indicators and their relationship to mean sea level and with the quality of age determinations a consistent methodology throughout the indo pacific for the analysis of sea level data is lacking future sea level analysis from far field locations must involve the application of a consistent methodology in order to allow meaningful comparison between studies this should help to resolve the ongoing debate about the magnitude and timing of the mid holocene high stand and the nature of late holocene sea level fall across the region

ice 5g and ice 6g models of postglacial relative sea level history applied to the holocene coral reef record of northeastern st croix u s v i investigating the influence of rotational feedback on gia processes at tropical latitudes abstract fossil coral reefs along the northeastern coast of st croix in the caribbean sea provide an 8000 year record of dated and interpreted holocene sea level change we herein compare this record with the predictions of models of glacio hydro isostatic adjustment for st croix and for additional sites at similar latitudes in the greater and lesser antilles region rsl predictions are based upon the model ice 5g vm2 and with a modified model ice 6g vm5a both including and excluding the influence of rotational feedback misfits between the modeled sea levels and the local geologic data are most apparent for models without rotational feedback particularly in the prediction of a 2 to 4 m unsupported mid holocene misfit at 4 ka as well as a small amplitude highstand that extends from 2 5 to 1 5 ka incorporation of the influence of rotational feedback provides the best fit to the data largely eliminating the unsupported mid holocene misfit between the data field and the sea level histories predicted by the models without rotational feedback and fitting data older than 5 kyr more closely than a previously published latitudinally averaged sea level curve for the western atlantic the st croix data therefore demonstrate that rotational influence extends at least 27 further south from its 45 n mid latitude extremum along the us east coast and identifies tropical latitudes as influenced by proglacial forebulge collapse implications for reef based sea level reconstruction include the ability to accurately model sea levels at specific tropical sites with partial holocene chronologies using the ice 6g vm5a model with rotational feedback latitudinally averaged sea level curves are therefore of limited use in understanding the relative importance of contributing physical influences on postglacial sea level history

sea level changes in the tectonically stable malay thai peninsula abstract the malay thai peninsula is part of sundaland a geological region of relative crustal stability therefore the positions of old shorelines of the past 20 000 years or so can be considered to indicate positions of actual past sea levels over 200 shoreline indicators at positions below as well as above present sea level have been radiocarbon dated these dated positions indicate that prior to 6 ka the sea rose from at least 90 m below present sea level at rates that initially amounted to 15 mm year and later became 6 mm year at ca 6 ka the rising sea surpassed its current position and at ca 5 ka it reached 5 m during this maximum marine inundation the peninsula was narrower since the low coastal plains did not yet exist in the period following this maximum transgression the available shoreline data indicate that regional sea level subsided through a series of fluctuations that were characterized by amplitudes of 2 m and periods of about 2000 years the peaks and troughs of the fluctuations became progressively lower the latest peak was at about 1 7 m or 0 7 m above present high tide a few hundred years ago the cause of these fluctuations is not yet known but the trend suggests that in the near future regional sea level may subside at annual rates between 1 5 mm and 2 mm this rate of descent is 25 to 30 of the estimated rate of sea level rise that may result from global warming in other words for the malay thai peninsula the effect of sea level rise on account of manmade greenhouse gases will be partly compensated by actual subsidence of regional sea level

identifying the causes of sea level change global mean sea level change has increased from a few centimetres per century over recent millennia to a few tens of centimetres per century in recent decades a review of the latest work shows that global mean sea level rise is unlikely to exceed one metre over the twenty first century but regional departures from this global mean could reach several decimetres

holocene sea level change on the southeast coast of australia a review a revised holocene sea level curve for the southeast coast of new south wales australia is presented based on a review of previously published geochronological results for fossil molluscs organi

coastal quaternary morphologies on the northern coast of the south china sea china and their implications for current tectonic models a review and preliminary study marine terraces tidal notches and sediments along a 1200 km long stretch of the northern coast of the south china sea passive margin were studied and divided into five areas with varying tectonic characters up to three marine terraces occur that have elevations reaching up to 60 m above mean sea level amsl and two marine notches occur up to 11 m amsl chronology of the morphologies and deposits was obtained mainly by comparison with quaternary sea levels derived from the oxygen isotope curve however prior to the last interglacial highstand mis 5e c 125 ka evidence of history of events is less well constrained leading to less precision on sea level positions prior to mis 5e using the morphological features of mis 5e as a marker mean coastal uplift rates in the last c 125 ka range from 0 07 mm yr to 0 18 mm yr the pattern of deformations is slightly higher than those observed on passive margin coasts in other parts of the world the cause of uplift of the south china coastline is not clear but may relate to the himalayan collision zone or any other large scale phenomena

radiocarbon dating and the reconstruction of late quaternary sea level changes in hong kong abstract radiocarbon dating is used widely for the reconstruction of late quaternary sea level changes in the present study eight case studies in hong kong have been chosen to highlight the difficulty in obtaining reliable radiocarbon dates pre holocene radiocarbon dates exceeding about 8100 yr bp have been found to show a young age bias a shell sample dated by two separate radiocarbon laboratories gave last interstadial ages differing by almost 9500 years while an oxygen isotope stage 5e age was obtained using uranium series dating other evidence including stratigraphy have shown that only the last interglacial age is acceptable the young age bias is attributed mainly to the post depositional introduction of young carbon into the sample for the reconstruction of sea level changes it is essential to select samples immediately above of the base of the holocene transgressive unit in offshore boreholes and excavations to satisfy the criteria of rapid burial these samples should preferably include mud plant matter and shells to facilitate interpretation furthermore as many samples as possible from a range of water depth down to about 130 m below the present sea level should be dated to reduce error introduced by counting statistics so the true signal of sea level changes can be reflected

an improved glacial isostatic adjustment model for the british isles the glacial isostatic adjustment gia of the british isles is of interest due to the constraints that can be provided on key model parameters such as the global meltwater signal local ice sheet history and viscoelastic earth structure a number of recent studies have modelled relative sea level rsl data from this region to constrain model parameters as indicated in these studies the sensitivity of these data to both local and global parameters results in a highly non unique problem this study aims to address this inherent non uniqueness by combining a previously published british irish ice model that is based on the most recent geomorphological data with a new global ice sheet model that provides an accurate prediction of eustatic sea level change in addition constraints from global positioning system gps measurements of present day vertical land motion are considered alongside the entirety of rsl data from both great britain and ireland a model solution is found that provides a high quality fit to both the rsl data and the gps data within the range of earth viscosity values considered the optimal data model fits were achieved with a relatively thin lithosphere 71 km upper mantle viscosities in the range 4 6 1020 pa s and lower mantle viscosities 3 1022 pa s copyright 2011 john wiley sons ltd

energetics of internal tides around the kerguelen plateau from modeling and altimetry a barotropic tidal model with a parameterization term to account for the internal wave drag energy dissipation is used to examine areas of possible m2 internal tide generation in the kerguelen plateau region barotropic energy flux and a distribution of wave drag dissipation are computed the results suggest important conversion of barotropic energy into baroclinic tide generation over the northern kerguelen plateau shelf break consistent with a theoretical criterion based on ocean stratification tidal forcing frequency and bathymetric gradients the sea surface height signatures of time coherent internal tides are studied using topex poseidon and jason 1 altimeter data whose ascending tracks cross nearly perpendicular to the eastern and western kerguelen plateau shelf break oscillations of a few centimeters associated with phase locked internal tides propagate away fromthe plateau over distances of several hundred kilometers with a 110 km wavelength when reaching the frontal area of the antarctic circumpolar current the internal tide cannot be identified because of the aliasing of mesoscale variability into the same alias band as m2 finally using altimeter data we estimate the m2 barotropic tidal power converted through the internal tide generation process we find consistent values with the barotropic model parameterization estimation which is also in good agreement with global internal tide model estimates combined with modeling this study has shown that altimetry can be used to estimate internal tide dissipation

4 d evolution of se asia s mantle from geological reconstructions and seismic tomography abstract how the collision between india and asia is related to processes deeper in the mantle is unclear here we compare geological reconstructions of block motions within asia since 50 ma with the tomographically imaged three dimensional 3 d morphology of subducted lithosphere to obtain insight into the spatiotemporal evolution of mantle structure past positions of the convergent margin show remarkable similarities with slab geometry at specific depths the striking change in slab geometry from a linear structure beneath 1100 km to an increasingly distorted shape at depths of less than 700 km results from collision the slab contours match the progressive deformation of asia s margin including india s indentation and sundaland s extrusion ever since the onset of collision the indian plate appears to have overridden its own sinking mantle and it does not seem at present to underthrust tibet significantly north of the zangbo suture if correct this observation would provide further evidence against models of plateau build up involving indian lithosphere the tomographic images beneath india confirm that asian deformation has absorbed at least 1500 km of convergence since collision began from the match between the southeastward motion of sundaland between 40 and 20 ma and the principal change in slab structure between 700 and 1100 km depths we infer that lateral advection in the mantle is small and that the sinking rate beneath sunda was 2 cm yr in the lower mantle and 5 cm yr above the transition zone

new constraints on late holocene eustatic sea level changes from mahe seychelles this study provides new estimates of globally integrated ice sheet melt during the late holocene since 4 ka bp from seychelles in the western indian ocean a tectonically stable far field location where the necessary glacial isostatic adjustment gia correction is small and is relatively insensitive to predictions using different earth viscosity profiles we compare sea level data from seychelles to estimates of eustasy from two gia models ice 5g and eust3 which represent end members in the quantity of global melt during the late holocene we use data from a range of coastal environments including fringing reef present day beaches fossil plateau and mangrove deposits on the largest island of the seychelles archipelago mahe to reconstruct relative sea level changes our data suggest that extensive coastal deposits of carbonate rich sands that fringe the west coast formed in the last 2 ka and the horizontal nature of their surface topography suggests rsl stability during this period mangrove sediments preserved behind these deposits and in river mouths date to c 2 ka and indicate that rsl was between 2 m and present during this interval correcting the reconstructed sea level data using a suite of optimal gia models based on the two ice models mentioned above and a large number c 350 of earth viscosity models gives a result that is consistent with the sedimentological constraints when uncertainties in both model results and data are considered it is possible to rule out eustatic sea levels below c 2 m and more than a few decimetres above present during the past two millennia this uncertainty is dominated by error in the reconstructions rather than the model predictions we note however that our estimates of eustasy are more compatible with the eust3 model compared to the ice 5g model during the late holocene 2 1 ka bp our evidence from seychelles shows that the timing of when eustatic sea level first rose close to present is between the predictions of the two end member gia models presented here 4 ka bp for ice 5g and 1 ka bp for eust3 using all lines of evidence currently available from mahe we suggest that the eustatic contribution during the last 2 ka has been less than 2 m this conclusion is drawn from a tectonically stable far field region that is relatively insensitive to earth and ice model uncertainties and implies that global eustasy has been relatively insensitive to climate fluctuations over the pre industrial part of the last 2 ka

testing models of mid to late holocene sea level change north queensland australia understanding the nature of global ice equivalent eustatic sea level changes during the mid to late holocene is important to our understanding of how ice sheets will respond to future climate change this study re analyses the indicative meaning and age control of existing relative sea level rsl data from cleveland bay north queensland australia and presents new rsl data from a foraminifera based transfer function as a preliminary test of global geophysical models in this region during the mid to late holocene the foraminifera based transfer function produces reliable rsl estimates consistent through the mid to late holocene at different locations in cleveland bay analysis of the combined rsl database reveals that rsl rose above present between 8 and 6 2 ka cal bp with the peak of the sea level highstand c 2 8 m above present at c 5 ka cal bp remaining relatively stable above 1 5 m from 6 2 until at least 2 3 ka cal bp falling to present in the last millennia this long period of sea level above present in the mid to late holocene suggests a gradual rather than abrupt end to global ice melt which must have continued into the late holocene this new analysis also shows no evidence for episodic fluctuations within the highstand although they cannot be entirely ruled out by this study this study demonstrates that more sea level data needs to be collected from locations uncontaminated by glacio isostasy hydro isostasy and tectonic effects in order to better constrain the late holocene melt histories of the large polar ice sheets

quantitative evidence that compaction of holocene sediments drives the present land subsidence of the po delta italy 1 deltas are highly dynamic coastal systems that over the last few decades have generally experienced a substantial area loss caused by trapping of river sediments in upland drainage basins as well as land subsidence due to natural and anthropogenic causes a major example is the po delta in the mediterranean in northeastern italy this area has experienced as much as 3 m of land subsidence from the 1930s to the 1970s primarily because of the extraction of gas bearing waters however present subsidence rates are largely unknown and the ground settlement is supposedly controlled by natural long term deep processes we have combined radar interferometric point target analysis ipta with previous geomorphological investigations on aerial satellite images and seismic surveys and geochronological data from core samples and geomechanical in situ tests to assess the current sinking of the delta and to understand the processes controlling the vertical movement the high density of the measurable point targets more than 15 000 allows characterization of the spatial variation in the vertical land motions vlm ranging from 1 to 15 mm yr we find that subsidence rates are significantly correlated with the age of highly compressible holocene deposits that compose the shallowest 30 40 m of the sedimentary sequence a typical log type consolidation equation applicable at the scale of the entire delta has been obtained we conclude that the consolidation of late holocene sediments is the major cause of the present land subsidence in the po river delta this finding has significant impact on the understanding of many other modern deltas that were formed in the lower holocene epoch

modelling sea level data from china and malay thailand to estimate holocene ice volume equivalent sea level change abstract this study presents a new model of holocene ice volume equivalent sea level esl extending a previously published global ice sheet model bassett et al 2005 which was unconstrained from 10 kyr bp to present this new model was developed by comparing relative sea level rsl predictions from a glacial isostatic adjustment gia model to a suite of holocene sea level index points from china and malay thailand three consistent data model misfits were found using the bassett et al 2005 model an over prediction in the height of maximum sea level the timing of this maximum and the temporal variation of sea level from the time of the highstand to present the data model misfits were examined for a large suite of esl scenarios and a range of earth model parameters to determine an optimum model of holocene esl this model is characterised by a slowdown in melting at 7 kyr bp associated with the final deglaciation of the laurentide ice sheet followed by a continued rise in esl until 1 kyr bp of 5 8 m associated with melting from the antarctic ice sheet it was not possible to identify an earth viscosity model that provided good fits for both regions with the china data preferring viscosity values in the upper mantle of less than 1 5 10 20 pa s and the malay thailand data preferring greater values we suggest that this inference of a very weak upper mantle for the china data originates from the nearby subduction zone and hainan plume the low viscosity values may also account for the lack of a well defined highstand at the china sites

constraints on the ocean oxygen isotopic enrichment between the last glacial maximum and the holocene paleoceanographic implications abstract we review the various methods which have been applied to estimate the change of seawater 18 o w between the last glacial maximum lgm and the holocene the most accurate constraints on these estimates are provided by the measurement of pore waters 18 o and by high resolution records of benthic foraminifer 18 o in the high latitude oceans of both hemispheres they show that the 18 o of seawater in the deep ocean during the lgm was 1 05 0 20 heavier than today with significant regional variations constraints resulting from ice sheet models are less accurate because both the volume and isotopic composition of each ice sheet are still poorly known the amplitude of the benthic 18 o change between the lgm and the holocene together with the 18 o and 13 c values of the benthic foraminifera genus cibicides during the lgm show that the southern ocean deep waters were extremely cold close to the freezing point during this time deep waters of the south atlantic and the pacific oceans were at least 1 3 c warmer than those of the southern ocean overall the glacial deep ocean below 2500 m was characterized by extremely cold temperatures everywhere lower than 0 c 18 o values of benthic foraminifer from the north atlantic are highly variable this variability suggests that deep atlantic waters were not homogeneous probably because they resulted from the sinking of different surface water masses at various locations during winter the deep waters in the north atlantic were at most 2 c warmer than in southern ocean alternatively they could have been nearer the freezing point with a 18 o value lighter than the mean ocean water brine formation during winter would preserve such light 18 o values of the northern north atlantic surface water

post glacial sediment load and subsidence in coastal louisiana 1 sea level rise in the gulf of mexico has occurred at a rate of 1 8 2 2 mm yr during the 20th century or nearly the same as observed globally due to combined steric and water mass changes tide gauges in coastal louisiana however record a substantially larger rate of rise and while a number of causal mechanisms may be responsible their specific contribution is poorly understood using a realistic viscoelastic earth model detailed geologic parameters for south louisiana and new gps data we demonstrate that holocene sedimentary loading in the gulf and mississippi river delta is capable of contributing to 1 8 mm yr of subsidence over areas of 30 0 75 103 km2

understanding subsidence in the mississippi delta region due to sediment ice and ocean loading insights from geophysical modeling the processes responsible for land surface subsidence in the mississippi delta md have been vigorously debated numerous studies have postulated a dominant role for isostatic subsidence associated with sediment loading previous computational modeling of present day vertical land motion has been carried out in order to understand geodetic data while the magnitudes of these measured rates have been reproduced the model parameter values required have often been extreme and in some cases unrealistic in contrast subsidence rates in the md on the 103 year timescale due to delta loading estimated from relative sea level reconstructions are an order of magnitude lower in an attempt to resolve this conflict a sensitivity analysis was carried out using a spherically symmetric viscoelastic solid earth deformation model with sediment ice and ocean load histories the model results were compared with geologic and geodetic observations that provide a record of vertical land motion over three distinctly different timescales past 80 kyr past 7 kyr and past 15 years it was found that glacial isostatic adjustment is likely to be the dominant contributor to vertical motion of the pleistocene and underlying basement present day basement subsidence rates solely due to sediment loading are found to be less than 0 5 mm yr 1 the analysis supports previous suggestions in the literature that earth rheology parameters are time dependent specifically the effective elastic thickness of the lithosphere may be 50 km on a 105 year timescale but closer to 100 km over 103 to 104 year timescales

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

terminal antarctic melting inferred from a far field coastal site abstract the contribution of the antarctic ice sheet ais to deglacial sea level rise is poorly constrained this shortfall gives rise to concerns because incorrect ais estimates impact significantly on our ability to predict sea level change in the course of global warming given the scarcity of geological data and the complexity of the antarctic response to glacio isostatic adjustment processes there is a need for accurate data to constrain the timing of the ice sheet retreat here we provide such data on the holocene antarctic melting through an isolated geographic site on the northern hemisphere which we show is sensitive to the antarctic signal using both our site and other mid latitudinal relative sea level sites our model provides a consensus estimate that the ais released water corresponding to 5 m equivalent sea level at 8 ka and ceased melting at 6 ka this is different to most ais models which release an equal amount of water at 11 ka or after 6 ka our findings change model assumptions about the terminal ais melting and show that future holocene sea level research should focus on broad shelves and large coast embayments in the mid latitudes

glacial isostatic adjustment on a rotating earth summary we extend and complete previous work to compute the influence of perturbations to the rotation vector on a suite of observables associated with glacial isostatic adjustment gia we emphasize observables relevant to present and future geodetic missions for example present day 3 d crustal motions relative sea level change and geoid or absolute sea level variations our calculations adopt spherically symmetric self gravitating maxwell viscoelastic earth models while incorporating realistic mass ice plus ocean load and rotation variations the predicted rotation induced signals are dominated by the influence of true polar wander tpw the spatial geometry of the tpw induced relative sea level geoid and radial velocity fields is primarily that of a degree two order one surface spherical harmonic the spatial variation of the horizontal velocity vectors is given by the gradient of this harmonic the peak radial and horizontal velocities are of the order of 0 5 mm yr 1 however we show that this value is sensitive to the adopted profile of mantle viscosity we also demonstrate that an accurate prediction of tpw induced sea level and 3 d crustal deformation rates requires that a realistic number of glacial cycles be incorporated into the ice load history we conclude that geodetic observations of the gia process should be analysed using a gia theory valid for a rotating planet finally we also consider variations in rotation driven by simple present day polar melting scenarios and predict the influence of these variations on a suite of geophysical observables we find that the rotational feedback associated with greenland melting is capable of significantly perturbing both relative and absolute sea level variations

compaction of holocene strata and the implications for relative sealevel change on the east coast of england the contribution of compaction of holocene strata to sea level rise shoreline erosion and wetland loss is difficult to decipher because of a lack of long term empirical data we analyzed more than 360 radiocarbon dated index points to constrain relative sea levels along the east coast of england during the holocene and to provide estimates of sediment compaction the isostatic effect of glacial rebound explains regional scale differences in relative sea levels northeast england the most northern study area reveals a middle to late holocene highstand 1 m above present ca 3 4 kyr b p whereas the tees estuary humber estuary lincolnshire marshes fenlands and north norfolk each reveal sea level histories of an upward trend during the holocene within each area sediment compaction explains the variation in elevation between sealevel reconstructions derived from index points taken from basal peat and those from peat intercalated within thick sequences of holocene sediments we find average compaction rates of 0 4 0 3 mm yr 1 with higher values for the large estuaries rates of late holocene relative sea level changes calculated from basal peats range from 0 2 0 1 mm yr 1 i e sea level fall in northeast england to 0 8 0 1 mm yr 1 in north norfolk inclusion of intercalated index points overestimates late holocene rates by 0 1 0 4 mm yr 1 because of the effects of sediment compaction

a method to estimate the total magnetization direction from a distortion analysis of magnetic anomalies1 knowledge of the declination and inclination of the total and induced magnetization vectors is normally required for the interpretation and analysis of magnetic anomalies a new method of estimating the direction of the total magnetization vector of magnetized rocks from magnetic anomalies is proposed the unknown declination and inclination d t and i t can be found by applying a reduction to the pole operator to the measured anomalies for different couples of total magnetization direction parameters d t and i t and by observing the variation of the anomaly minimum as a function of both d t and i t and d t are estimated using the maximum of this function comparing our method to previous methods one advantage is that our estimates are not zero level dependent furthermore the method allows inclinations to be well estimated with the same accuracy as declinations finally declinations are not underestimated our method is applied to a real case and meaningful results are obtained it is shown that the feasibility of the method is improved by removing the low frequency components

a data constrained large ensemble analysis of antarctic evolution since the eemian abstract reconstructing the historical behaviour of the antarctic ice sheet is essential for understanding and predicting climatic interactions ice sheet sensitivities and sea level contributions furthermore to interpret such reconstructions with any degree of confidence meaningful uncertainty estimates are required working toward this goal this article presents results from a large ensemble data constrained study of antarctic evolution over the last glacial cycle ice sheet chronologies have been generated using a 3 d glacial systems model that includes sheet stream shelf flow a parametrized basal drag coefficient accounting for sub grid topographic roughness sediment likelihood and systematic model to observation thickness misfits a sub grid grounding line flux parametrization a visco elastic bedrock response component parametrized climate forcing separate shelf and tidewater calving treatments and a physically motivated empirically derived sub shelf melt component there are 31 ensemble parameters to capture uncertainties in the glacial cycle climate mass balance processes and ice dynamics once generated the ensemble of model runs is constrained using a suite of observational data including constraints on relative sea level past ice thickness and grounding line retreat data points as well as present day ice volumes and configuration and an evaluation methodology that produces a misfit to observations score for each run assuming variants of a gaussian error model the scores are used to generate probability distributions for the past evolution of the ice sheet in our ensemble based analysis the last glacial maximum lgm of antarctic ice volume occurs at 25 24 ka the lgm ice volume excess relative to present day is likely between 5 6 and 14 3 m equivalent sea level mesl and with less confidence 10 mesl there is little change in the grounded ice volume from 24 ka until 17 16 ka at which time widespread deglaciation commences the ross and weddell sea sectors are the largest sources of ice mass loss the major period of grounding line retreat in the weddell sea sector resulting in the present day ronne filchner shelf system occurs after 10 ka the grounding line in the ross sea sector start its major retreat phase after 12 ka there is no significant contribution during the eemian the modelled antarctic ice sheet has a minimal ice volume at 114 ka contributing 2 mesl relative to present day the mass loss is principally due to a major retreat of the grounding line in the siple coast sector of the ross sea we present standard deviation plots of the ensemble results for present day and at the lgm these plots highlight geographic areas that would most benefit from additional constraint and therefore offer priorities and guidance for future field campaigns

retreat of the east antarctic ice sheet during the last glacial termination the east antarctic ice sheet retreated at the end of the last glacial period terrestrial and marine data suggest that the retreat began 14 000 years ago indicating that the east antarctic ice sheet probably did not contribute to meltwater pulse 1a 14 700 years ago

separation of magnetic anomalies into induced and remanent magnetization contributions abstract inversion of magnetic data is complicated by the presence of remanent magnetization and it provides limited information about the magnetic source because of the insufficiency of data and constraint information we propose a fourier domain transformation allowing the separation of magnetic anomalies into the components caused by induced and remanent magnetizations the approach is based on the hypothesis that each isolated source is homogeneous with a uniform and specific koenigsberger ratio the distributions of susceptibility and remanent magnetization are subsequently recovered from the separated anomalies anomaly components susceptibility distribution and distribution of the remanent and total magnetization vectors direction and intensity can be achieved through the processing of the anomaly components the proposed method therefore provides a procedure to test the hypotheses about target source and magnetic field by verifying these models based on available information or a priori information from geology we test our methods using synthetic and real data acquired over the zhangfushan iron ore deposit and the yeshan polymetallic deposit in eastern china all the tests yield favourable results and the obtained models are helpful for the geological interpretation

estimating the magnetization direction of sources from southeast bulgaria through correlation between reduced to the pole and total magnitude anomalies we present a new method to estimate the direction of the magnetization vector of geological bodies based upon the correlation between the reduced to the pole field for tentative values of the magnetization direction and the total magnitude anomaly obtained by a transform of the measured magnetic field the reduced to the pole and the total magnitude anomaly are centred over the sources in the case of 2d anomalies or well centred in the case of compact 3d sources and have similar patterns for the same source the method has several important advantages over similar transform correlation methods for estimation of the magnetization direction it calculates only one transform for many tentative values of the magnetization direction the method does not use derivatives of any order and relies on confident isolation of the target anomalies based on one of the compared transforms the total magnitude anomaly we studied the performance of the method on five 2 5d and compact 3d sources we analysed possible inherent to the method errors as well as errors due to interference from neighbouring sources finally we estimated the magnetization vector direction of the main sources causing the magnetic field in the burgas region and the adjoining southeast bulgarian black sea shelf the sources in the black sea shelf show prevalently reverse magnetization while the sources on land have normal or reverse magnetization

post glacial sea level changes around the australian margin a review abstract it has been known since rhodes fairbridge s first attempt to establish a global pattern of holocene sea level change by combining evidence from western australia and from sites in the northern hemisphere that the details of sea level history since the last glacial maximum vary considerably across the globe the australian region is relatively stable tectonically and is situated in the far field of former ice sheets it therefore preserves important records of post glacial sea levels that are less complicated by neotectonics or glacio isostatic adjustments accordingly the relative sea level record of this region is dominantly one of glacio eustatic ice equivalent sea level changes the broader australasian region has provided critical information on the nature of post glacial sea level including the termination of the last glacial maximum when sea level was approximately 125 m lower than present around 21 000 19 000 years bp and insights into meltwater pulse 1a between 14 600 and 14 300 cal yr bp although most parts of the australian continent reveals a high degree of tectonic stability research conducted since the 1970s has shown that the timing and elevation of a holocene highstand varies systematically around its margin this is attributed primarily to variations in the timing of the response of the ocean basins and shallow continental shelves to the increased ocean volumes following ice melt including a process known as ocean siphoning i e glacio hydro isostatic adjustment processes several seminal studies in the early 1980s produced important data sets from the australasian region that have provided a solid foundation for more recent palaeo sea level research this review revisits these key studies emphasising their continuing influence on quaternary research and incorporates relatively recent investigations to interpret the nature of post glacial sea level change around australia these include a synthesis of research from the northern territory queensland new south wales south australia and western australia a focus of these more recent studies has been the re examination of 1 the accuracy and reliability of different proxy sea level indicators 2 the rate and nature of post glacial sea level rise 3 the evidence for timing elevation and duration of mid holocene highstands and 4 the notion of mid to late holocene sea level oscillations and their basis based on this synthesis of previous research it is clear that estimates of past sea surface elevation are a function of eustatic factors as well as morphodynamics of individual sites the wide variety of proxy sea level indicators used their wide geographical range and their indicative meaning some progress has been made in understanding the variability of the accuracy of proxy indicators in relation to their contemporary sea level the inter comparison of the variety of dating techniques used and the nuances of calibration of radiocarbon ages to sidereal years these issues need to be thoroughly understood before proxy sea level indicators can be incorporated into credible reconstructions of relative sea level change at individual locations many of the issues which challenged sea level researchers in the latter part of the twentieth century remain contentious today divergent opinions remain about 1 exactly when sea level attained present levels following the most recent post glacial marine transgression pmt 2 the elevation that sea level reached during the holocene sea level highstand 3 whether sea level fell smoothly from a metre or more above its present level following the pmt 4 whether sea level remained at these highstand levels for a considerable period before falling to its present position or 5 whether it underwent a series of moderate oscillations during the holocene highstand

holocene sea levels and palaeoenvironments malay thai peninsula southeast asia sedimentological and palynological investigations of great songkhla lakes east coast of the malay thai peninsula southeast asia reveal sedimentary sequences rich in palynomorph assemblages dominated by pollen of mangroves and freshwater swamps compared with other regions in southeast asia the assemblages are of relatively low diversity geochronological data indicate that the great songkhla lakes record one of the earliest mangrove environments in southeast asia 8420 8190 cal yr bp which are subsequently replaced by a freshwater swamp at 7880 7680 cal yr bp owing to the decline of marine influence sea level observations from great songkhla lakes and other areas of the malay thai peninsula reveal an upward trend of holocene relative sea level from a minimum of 22 m at 9700 9250 cal yr bp to a mid holocene high stand of 4850 4450 cal yr bp which equates to a rise of c 5 5 mm yr the sea level fall from the high stand is steady at c 1 1 mm yr geophysical modelling shows that hydroisostasy

a deglacial model for antarctica geological constraints and glaciological modelling as a basis for a new model of antarctic glacial isostatic adjustment abstract we present a new reconstruction of the antarctic ice sheets between 20 ka bp and the present day our reconstruction is derived using a numerical model to generate a physically consistent ice surface across the whole of the continent we define the extent of the ice sheet at five time slices 20 15 10 5 and 0 ka bp assuming an equilibrium state for the 20 ka bp time slice and a transient state for the deglacial time slices the evolution of the ice sheet within the numerical model is driven by variations in temperature accumulation rate and relative sea level in order to reconstruct the concave profile of the ice sheet in marine grounded regions such as the ross and weddell seas we force our model to develop channels of faster flow by defining greater basal sliding along the trajectory of former ice streams we find a strong dependence upon the basal sliding parameters and also the position of the grounding line we use an extensive data base of geological and glaciological data to constrain our ice sheet reconstruction grounding line extent is prescribed from marine geological data and we test ice sheet thickness against onshore geological data at 62 sites of the five time slices considered our 20 ka bp reconstruction is the best constrained by data and has an rms misfit of 147 6 m when compared to observations of ice thickness change between 20 ka bp and the present day across all time slices there are large regions of the ice sheet which are poorly constrained especially after 20 ka bp we estimate the spatial distribution of uncertainty in our ice sheet reconstruction and note that the solutions are least reliable in regions of complex topography we predict that the antarctic ice sheets contributed 9 1 5 m of eustatic sea level to the global ocean between 20 ka bp and the present and our reconstruction with minimum misfit contributes 8 m eustatic sea level during this period these values which we argue are an upper bound are lower than many previous estimates the reconstructed pattern of ice unloading can serve as a new input for glacial isostatic models

reconstruction of changes in the weddell sea sector of the antarctic ice sheet since the last glacial maximum the weddell sea sector is one of the main formation sites for antarctic bottom water and an outlet for about one fifth of antarctica s continental ice volume over the last few decades studies on glacial geological records in this sector have provided conflicting reconstructions of changes in ice sheet extent and ice sheet thickness since the last glacial maximum lgm at ca 23 19 calibrated kiloyears before present cal ka bp terrestrial geomorphological records and exposure ages obtained from rocks in the hinterland of the weddell sea ice sheet thickness constraints from ice cores and some radiocarbon dates on offshore sediments were interpreted to indicate no significant ice thickening and locally restricted grounding line advance at the lgm other marine geological and geophysical studies concluded that subglacial bedforms mapped on the weddell sea continental shelf subglacial deposits and sediments over compacted by overriding ice recovered in cores and the few available radiocarbon ages from marine sediments are consistent with major ice sheet advance at the lgm reflecting the geological interpretations different ice sheet models have reconstructed conflicting lgm ice sheet configurations for the weddell sea sector consequently the estimated contributions of ice sheet build up in the weddell sea sector to the lgm sea level low stand of 130 m vary considerably in this paper we summarise and review the geological records of past ice sheet margins and past ice sheet elevations in the weddell sea sector we compile marine and terrestrial chronological data constraining former ice sheet size thereby highlighting different levels of certainty and present two alternative scenarios of the lgm ice sheet configuration including time slice reconstructions for post lgm grounding line retreat moreover we discuss consistencies and possible reasons for inconsistencies between the various reconstructions and propose objectives for future research the aim of our study is to provide two alternative interpretations of glacial geological datasets on antarctic ice sheet history for the weddell sea sector which can be utilised to test and improve numerical ice sheet models

viscosity of the asthenosphere from glacial isostatic adjustment and subduction dynamics at the northern cascadia subduction zone british columbia canada 1 late glacial sea level curves located in the cascadia subduction zone csz fore arc in southwestern british columbia show that glacial isostatic adjustment gia was rapid when the cordilleran ice sheet collapsed in the late pleistocene gia modeling with a linear maxwell rheology indicates that the observations can be equally well fit across a wide range of asthenospheric thicknesses provided that the asthenospheric viscosity is varied from 3 1018 pa s for a thin 140 km asthenosphere to 4 1019 pa s for a thick 380 km asthenosphere present day vertical crustal motion predicted by the gia models shows rates of a few tenths of a millimeter per year consistent with previous analyses the model viscosities largely pertain to the viscosity of the oceanic mantle beneath the subducting juan de fuca slab but include a contribution from the mantle wedge above the slab for comparison effective viscosities for the upper mantle due to the tectonic regime subduction were computed using the strain rates and temperatures of an independent geodynamic model of the csz with a wet olivine power law rheology the effective viscosities agree well with gia model viscosities of 1019 pa s or less corresponding to an asthenosphere of 100 or 200 km thickness the agreement suggests a significant role for power law flow in the gia response regardless of the microphysical mechanisms responsible for the gia response the viscosity values inferred from gia can be applied to studies of the megathrust earthquake cycle because both processes take place on comparable time scales

inversion of magnetic anomaly on rugged observation surface in the presence of strong remanent magnetization abstractwe study the inversion of magnetic data acquired over a rugged observation surface and where the buried source bodies have strong remanent magnetization that leads to unknown total magnetization directions these factors pose significant challenges for processing and inversion of such data to tackle the challenges from both a rugged observation surface and an unknown magnetization direction we propose a strategy through the joint use of the equivalent source technique and 3d amplitude inversion to obtain 3d magnetization strength we use equivalent source processing to calculate the amplitude data in the space domain because the use of the wavenumber domain method is invalid due to large variations in the data elevation we then carried out an amplitude inversion to generate a 3d subsurface distribution of the magnitude of the total magnetization vector the results from a synthetic example and aeromagnetic data in daye mine in china showed that this approach is effective and images the magnetic

modelling holocene relative sea level observations from the caribbean and south america abstract holocene data from the caribbean and the atlantic coast of south america have been critically assessed and a subset of the best quality data are presented these data cover a large north south geographic extent and display a distinct spatial variation we make the first comparisons of this data set to predictions based on a realistic model of glaciation induced sea level change with the main aims of understanding the cause of the observed spatial trend and estimating a eustatic signal for the holocene the spatial variation is dominated by the influence of the ice and ocean mass redistribution on sea level change with the ice induced effect dominating the observed north south trend a best fitting model is applied to estimate a holocene eustatic signal from the observations we find that the model corrected data are consistent with a relatively rapid rise of 7 8 mm yr in the early holocene with a marked reduction in this rate around 7 cal kyr bp from this time until present the model corrected data suggest that the volume of mass transfer between ice sheets and oceans was no more than 1 m eustatic sea level equivalent

upper mantle beneath southeast asia from s velocity tomography 1 we present a three dimensional s velocity model of the se asian western pacific upper mantle with 400 km lateral resolution using the novel automated multimode inversion technique we processed 4038 vertical component seismograms and extracted 22 708 linear equations with uncorrelated uncertainties that constrain upper mantle structure we used time frequency windows to select signal with negligible proportion of scattered energy the windows included the fundamental rayleigh mode and s and multiple s waves the observed range of s velocity variations is the widest 17 18 in the upper 150 km of the mantle high velocity continental roots can reach beyond the present extent of the overlying archean proterozoic crust by 500 km beneath some precambrian units the roots are absent which can be attributed to deformation and gradual destruction of the ancient lithosphere at 120 150 km s velocity beneath some cratons reaches 4 8 km s this can be accounted for by thermal and compositional effects beneath the hainan island area a low velocity anomaly is observed from near the surface to the bottom of our model the hot spot type volcanism here may be caused by the deep mantle hainan plume a low velocity mantle domain underlies the south central sea of japan surrounded on the surface by intraplate volcanoes a deep seismicity gap is present near 40 n in the pacific slab subducting below and may result from a plume slab interaction a high velocity anomaly is present in the transition zone beneath the northern boundary of the yangtze craton we propose that the anomaly corresponds to subducted continental lithosphere stagnant atop the 660 km discontinuity

postglacial sealevels on a spherical self gravitating viscoelastic earth effects of lateral viscosity variations in the upper mantle on the inference of viscosity contrasts in the lower mantle abstract previous studies of lateral viscosity variations on postglacial rebound often neglect the spherical shape of the earth and the self gravity of the solid earth and oceans in this paper the consistent sealevel equation is solved by the coupled laplace finite element method for a spherical self gravitating incompressible maxwell earth it confirms the importance of self gravity in the oceans on sealevel computation near the ice margin where the data are most sensitive to the existence of lateral variations in lithospheric thickness and asthenospheric viscosity the effects of lateral variations in lower mantle viscosity asthenospheric viscosity and lithospheric thickness are investigated this paper confirms the finding of earlier investigations the combined effect of lateral viscosity variations in the lower mantle with reverse viscosity contrasts in the upper mantle is also investigated for sealevel data near the center of rebound the effect of lateral viscosity contrast in the lower mantle can be masked by the existence of a reverse lateral viscosity contrasts in the upper mantle however this is not the case for sealevel data just outside the ice margin

glacier mass balance determination by remote sensing and high resolution modelling an indirect methodology for determining the distribution of mass balance at high spatial resolution using remote sensing and ice flow modelling is presented the method based on the mass continuity equation requires two datasets collected over the desired monitoring interval i the spatial pattern of glacier surface elevation change and ii the mass flux divergence field at haut glacier d arolla valais switzerland the mass balance distribution between september 1992 and september 1993 is calculated at 20 m resolution from the difference between the pattern of surface elevation change derived from analytical photogrammetry and the mass flux divergence field determined from three dimensional numerical flow modelling constrained by surface velocity measurements the resultant pattern of mass balance is almost totally negative showing a strong dependence on elevation but with large localized departures the computed distribution of mass balance compares well r 2 0 91 with mass balance measurements made at stakes installed along the glacier centre line over the same period despite the highly optimized nature of the flow modelling effort employed in this study the good agreement indicates the potential this method has as a strategy for deriving high spatial and temporal resolution estimates of mass balance

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

three dimensional inversion of magnetic data in the simultaneous presence of significant remanent magnetization and self demagnetization example from daye iron ore deposit hubei province china

comprehensive approaches to 3d inversion of magnetic data affected by remanent magnetization three dimensional 3d inversion of magnetic data to recover a distribution of magnetic susceptibility has been successfullyusedformineralexplorationduringthelastdecade however the unknown direction of magnetization has limited the use of this technique when significant remanence is present we have developed a comprehensive methodology for solving this problem by examining two classes of approaches and have formulated a suite of methods of practical utility the first class focuses on estimating total magnetization direction and then incorporating the resultant direction into an inversion algorithm that assumes a known direction thesecondclassfocusesondirectinversionoftheamplitude of the magnetic anomaly vector amplitude data depend weaklyuponmagnetizationdirectionandareamenabletodirect inversion for the magnitude of magnetization vector in 3d subsurface two sets of high resolution aeromagnetic dataacquiredfordiamondexplorationinthecanadianarctic areusedtoillustratethemethods usefulness

mid holocene sea level highstand along the southeast coast of china various sea level curves have been proposed for the coast of china in the past two decades these sea level curves indicate a complex history of holocene sea level and so the debate on whether or not a higher mid holocene sea level highstand exists in the coast of china has continued this paper aims to re examine the holocene sea level history for the low latitude part of the china coast between 18 n and 32 n by re assessing all the sea level data available from the east to south coasts and separating them according to geological settings in order to examine the influences of global and local factors the reconstructed sea level histories from different coastal sectors of the china coast reveal a certain degree of variability in the timing and height of mid holocene sea level highstand within large river deltas the mid holocene sea level highstand occurred earlier by almost 1000 years than that from other coastal sites the highstand from large river deltas appears also lower in altitude a few metres below the present day sea level due probably to the local factors of subsidence and sediment consolidation in geologically stable coastal sites the highstand is recorded at the same altitude as the present day sea level a 1 2 m higher highstand is found from sites where tectonic uplift is observed

observed crustal uplift near the southern patagonian icefield constrains improved viscoelastic earth models thirty one gps geodetic measurements of crustal uplift in southernmost south america determined extraordinarily high trend rates 35 mm yr in the north central part of the southern patagonian icefield these trends have a coherent pattern motivating a refined viscoelastic glacial isostatic adjustment model to explain the observations two end member models provide good fits both require a lithospheric thickness of 36 5 5 3 km however one end member has a mantle viscosity near 1 6 1018 pa s and an ice collapse rate from the little ice age lia maximum comparable to a lowest recent estimate of 1995 2012 ice loss at about 11 gt yr in contrast the other end member has much larger viscosity 8 0 1018 pa s half the post lia collapse rate and a steadily rising loss rate in the twentieth century after ad 1943 reaching 25 9 gt yr during 1995 2012

structure of the upper mantle and transition zone beneath southeast asia from traveltime tomography 1 tomographic images of the mantle beneath east asia were obtained from the inversion of traveltime data from global and regional seismograph networks and from temporary arrays on and around the tibetan plateau our results are consistent with previous studies but the unprecedented resolution of mantle heterogeneity provides new insight into the large scale tectonic framework of the continental india asia collision in the western part of the study region and subduction of the oceanic lithosphere in the east in the realm of continental collision west of 100 e a relatively slow p wave speed characterizes the upper mantle beneath much of the tibetan plateau but the wave speed is high beneath cratonic india the southern and western part of the tibetan plateau hindu kush and the tian shan in the subduction realm east of 110 e the main structures are i pronounced low wave speed anomalies at a depth of between 100 and 400 km beneath asia s southeastern seaboard and the back arc regions of ongoing subduction ii narrow fast anomalies in the upper mantle beneath major subduction zones and iii widespread fast anomalies at a depth of 500 700 km beneath the sea of japan the northern part of the philippine sea plate and southeastern china if the latter anomalies represent stagnant slabs their fragmented nature and large lateral extent suggest that they are produced by different episodes of subduction beneath western pacific island arcs along the old se margin of asia or during the mesozoic collision of cratonic units in southeast asia attribution to ancient subduction systems implies that slab fragments can reside in the transition zone for at least several tens of millions of years shallow slow anomalies beneath the red river fault region connect to deep anomalies beneath the south china fold belt and south china sea suggesting a causal relationship between the evolution of the continental lithosphere of sw china and deeper mantle processes between the collision and the subduction realms tomography reveals high wave speed continental roots beneath the western part of the north china craton ordos block and the south china or yangtze craton sichuan basin to a depth of 300 km

holocene sea level change and antarctic melting history derived from geological observations and geophysical modeling along the shimokita peninsula northern japan 1 a mid to late holocene sea level record based on combined geomorphological geological and micropaleontological observations was obtained from well developed wave cut benches subaerially exposed along the shimokita peninsula northern japan results indicate that the benches were formed during mid to late holocene sea level transgressions reaching a maximum highstand level of 2 m above present at about 4 000 years ago this timing corresponds to an abrupt order of magnitude decrease in sedimentation rate as recorded in a core recovered from proximal mutsu bay in addition glacio hydro isostatic adjustment due to crustal deformation in response to postglacial sea level rise was modeled and results are consistent with the reconstructed local 2 m highstand given that meltwater contributions from the major north american and european ice sheets had largely ceased by 7 000 years ago these independent lines of evidence taken together indicate that melting of the antarctic ice sheet ended by 4 000 years ago