testing the sensitivity of the east antarctic ice sheet to southern ocean dynamics past changes and future implications the stability of antarctic ice sheets and their potential contribution to sea level under projected future warming remains highly uncertain the last interglacial 135 000 116 000 years ago provides a potential analogue with global temperatures 2uc higher and rates of sea level rise 5 6m ka 1 leading to sea levels 6 6 9 4m higher than present the source s of this sea level rise remain fiercely debated here we report a series of independent model simulations exploring the effects of migrating southern hemisphere westerlies shws on southern ocean circulation and antarctic ice sheet dynamics we suggest that southerly shifts in winds may have significantly impacted the sub polar gyres inducing pervasive warming 0 2 0 8uc in the upper 1200m adjacent to sectors of the east antarctic ice sheet eais which due to their geometries and connectivity to the southern ocean are highly sensitive to ocean forcing we conclude that the eais potentially made a substantial hitherto unsuspected contribution to interglacial sea levels and given 21st century projections in the southern annular mode and associated shw migration we highlight how pervasive circum antarctic warming may threaten eais stability copyright 2013 john wiley sons ltd

impact processes permafrost dynamics and climate and environmental variability in the terrestrial arctic as inferred from the unique 3 6 myr record of lake el gygytgyn far east russia a review lake el gygytgyn in far east russia is a 3 6 myr old impact crater lake located in an area that has never been affected by cenozoic glaciations nor desiccation the unique sediment record of the l

structural framework and tectono stratigraphic evolution of the eastern persian gulf offshore iran abstract seismic and well data are utilised to describe the tectono stratigraphic evolution of the eastern persian gulf during the late mesozoic and cenozoic the structural framework of the study area is the result of the late cretaceous to early miocene oman orogeny overprinted by the southwestward advance of the zagros orogeny through the late miocene and pliocene two structural domains can be identified the ne sw trending musandam fold thrust belt mftb and the nw se trending persian gulf foredeep basin the mftb formed as a result of multiple compressional events late cretaceous late paleocene to early eocene and late oligocene to early miocene the first compressional event cenomanian turonian to the maastrichtian is characterized by emplacement obduction of the allochthonous rocks onto the passive continental margin of the arabian plate in the oman mountains this event led to regional deformation and uplift which caused deep erosion of the albian to santonian units during the santonian to maastrichtian in addition to regional deformation a ne sw trending foredeep basin developed in front of the late cretaceous thrust sheets creating accommodation space for turbiditic deposits of the gurpi formation during the late paleocene early eocene initiation of a new compressional deformation led to establishment of the pabdeh foredeep basin in this stage the basin depocenter migrated 30 km to the west the third compressional event began in the late oligocene reaching a climax in the early miocene this event resulted in regional deformation and uplift which caused deep erosion of the pre middle miocene strata the persian gulf foredeep basin has developed in front of the rising zagros mountains since late miocene pliocene folding related to advancement of the zagros orogeny into the persian gulf is mainly restricted to northeastern flank near the coast of iran the effect of folding decreases to the south of the zagros deformational front

the role of ocean thermal expansion in last interglacial sea level rise 1 a compilation of paleoceanographic data and a coupled atmosphere ocean climate model were used to examine global ocean surface temperatures of the last interglacial lig period and to produce the first quantitative estimate of the role that ocean thermal expansion likely played in driving sea level rise above present day during the lig our analysis of the paleoclimatic data suggests a peak lig global sea surface temperature sst warming of 0 7 0 6 c compared to the late holocene our lig climate model simulation suggests a slight cooling of global average sst relative to preindustrial conditions sst 0 4 c with a reduction in atmospheric water vapor in the southern hemisphere driven by a northward shift of the intertropical convergence zone and substantially reduced seasonality in the southern hemisphere taken together the model and paleoceanographic data imply a minimal contribution of ocean thermal expansion to lig sea level rise above present day uncertainty remains but it seems unlikely that thermosteric sea level rise exceeded 0 4 0 3 m during the lig this constraint along with estimates of the sea level contributions from the greenland ice sheet glaciers and ice caps implies that 4 1 to 5 8 m of sea level rise during the last interglacial period was derived from the antarctic ice sheet these results reemphasize the concern that both the antarctic and greenland ice sheets may be more sensitive to temperature than widely thought

the ellsworth subglacial highlands inception and retreat of the west antarctic ice sheet antarctic subglacial highlands are where the antarctic ice sheets first developed and the pinning points where retreat phases of the marine based sectors of the ice sheet are impeded due to low ice velocities and limited present day change in the ice sheet interior west antarctic subglacial highlands have been overlooked for detailed study these regions have considerable potential however for establishing the locations from which the west antarctic ice sheet originated and grew and its likely response to warming climates here we characterize the subglacial morphology of the ellsworth subglacial highlands west antarctica from ground based and aerogeophysical radio echo sounding res surveys and the moderate resolution imaging spectroradiometer modis mosaic of antarctica we document well preserved classic landforms associated with restricted dynamic marine proximal alpine glaciation with hanging tributary valleys feeding a significant overdeepened trough the ellsworth trough cut by valley tidewater glaciers fjord mouth threshold bars down ice of two overdeepenings define both the northwest and southeast termini of paleo outlet glaciers which cut and occupied the ellsworth trough satellite imagery reveals numerous other glaciated valleys terminating at the edge of deep former marine basins e g bentley subglacial trench throughout the ellsworth subglacial highlands these geomorphic data can be used to reconstruct the glaciology of the ice masses that formed the proto west antarctic ice sheet the landscape predates the present ice sheet and was formed by a small dynamic ice field s similar to those of the present day antarctic peninsula at times when the marine sections of the west antarctic ice sheet were absent the ellsworth subglacial highlands represent a major seeding center of the paleo west antarctic ice sheet and its margins represent the pinning point at which future retreat of the marine based west antarctic ice sheet would be arrested

foraminifera in elevated bermudian caves provide further evidence for 21 m eustatic sea level during marine isotope stage 11 abstract two hypotheses have been proposed to explain the origin of marine isotope stage mis 11 deposits in small bermudian caves at 21 m above modern sea level 1 a 21 m mis 11 eustatic sea level highstand and 2 a mis 11 mega tsunami event importantly the foraminifera reported in these caves have yet to be critically evaluated within a framework of coastal cave environments after statistically comparing foraminifera in modern bermudian littoral caves and the mis 11 calonectris pocket a 21 m cave to the largest available database of bermudian coastal foraminifera the assemblages found in modern littoral caves and calonectris pocket a cannot be statistically differentiated from lagoons this observation is expected considering littoral caves are simply sheltered extensions of a lagoon environment in the littoral zone where typical coastal processes waves storms homogenize and rework lagoonal reefal and occasional planktic taxa fossil protoconchs of the bermudian cave stygobite caecum caverna were also associated with the foraminifera these results indicate that the mis 11 bermudian caves are fossil littoral caves breached flank margin caves where the total mis 11 microfossil assemblage is preserving a signature of coeval sea level at 21 m brackish foraminifera polysaccammina pseudothurammina and anchialine gastropods 95 300 individuals indicate a brackish anchialine habitat developed in the elevated caves after the prolonged littoral environmental phase the onset of sea level regression following the 21 m highstand would first lower the ancient brackish ghyben herzberg lens

unraveling the forcings controlling the vegetation and climate of the best orbital analogues for the present interglacial in sw europe the suitability of mis 11c and mis 19c as analogues of our present interglacial and its natural evolution is still debated here we examine the regional expression of the holocene and its orbital analogues over sw iberia using a model data comparison approach regional tree fraction and climate based on snapshot and transient experiments using the loveclim model are evaluated against the terrestrial marine profiles from site u1385 documenting the regional vegetation and climatic changes the pollen based reconstructions show a larger forest optimum during the holocene compared to mis 11c and mis 19c putting into question their analogy in sw europe pollen based and model results indicate reduced mis 11c forest cover compared to the holocene primarily driven by lower winter precipitation which is critical for mediterranean forest development decreased precipitation was possibly induced by the amplified mis 11c latitudinal insolation and temperature gradient that shifted the westerlies northwards in contrast the reconstructed lower forest optimum at mis 19c is not reproduced by the simulations probably due to the lack of eurasian ice sheets and its related feedbacks in the model transient experiments with time varying insolation and co2 reveal that the sw iberian forest dynamics over the interglacials are mostly coupled to changes in winter precipitation mainly controlled by precession co2 playing a negligible role model simulations reproduce the observed persistent vegetation changes at millennial time scales in sw iberia and the strong forest reductions marking the end of the interglacial optimum

collapse of polar ice sheets during the stage 11 interglacial the magnitude of sea level rise during marine isotope stage 11 about 400 000 years ago is shown to have been probably only 6 to 13 metres in contrast to some earlier estimates of up to 20 metres the ice sheets in greenland and west antarctica are known to be susceptible to climate warming and both are losing mass how the east antarctic ice sheet will respond to warming is less clear recent evidence from shoreline features in bermuda and the bahamas suggested that during marine isotope stage 11 a period of warming that occurred about 400 000 years ago the sea level was 20 metres higher than it is today which pointed to significant melting of the east antarctic ice sheet now an estimate that takes into account post glacial crustal subsidence of the shoreline sites during an anomalously long interglacial period puts the sea level during stage 11 at 6 13 metres higher than today that can be explained by the collapse of the greenland and west antarctic ice sheets with only a small contribution from the east antarctic ice sheet contentious observations of pleistocene shoreline features on the tectonically stable islands of bermuda and the bahamas have suggested that sea level about 400 000 years ago was more than 20 metres higher than it is today1 2 3 4 geochronologic and geomorphic evidence indicates that these features formed during interglacial marine isotope stage mis 11 an unusually long interval of warmth during the ice age1 2 3 4 previous work has advanced two divergent hypotheses for these shoreline features first significant melting of the east antarctic ice sheet in addition to the collapse of the west antarctic ice sheet and the greenland ice sheet1 2 3 or second emplacement by a mega tsunami during mis 11 ref 4 5 here we show that the elevations of these features are corrected downwards by 10 metres when we account for post glacial crustal subsidence of these sites over the course of the anomalously long interglacial on the basis of this correction we estimate that eustatic sea level rose to 6 13 m above the present day value in the second half of mis 11 this suggests that both the greenland ice sheet and the west antarctic ice sheet collapsed during the protracted warm period while changes in the volume of the east antarctic ice sheet were relatively minor thereby resolving the long standing controversy over the stability of the east antarctic ice sheet during mis 11

recent sea level contributions of the antarctic and greenland ice sheets after a century of polar exploration the past decade of satellite measurements has painted an altogether new picture of how earth s ice sheets are changing as global temperatures have risen so have rates of snowfall ice melting and glacier flow although the balance between these opposing processes has varied considerably on a regional scale data show that antarctica and greenland are each losing mass overall our best estimate of their combined imbalance is about 125 gigatons per year of ice enough to raise sea level by 0 35 millimeters per year this is only a modest contribution to the present rate of sea level rise of 3 0 millimeters per year however much of the loss from antarctica and greenland is the result of the flow of ice to the ocean from ice streams and glaciers which has accelerated over the past decade in both continents there are suspected triggers for the accelerated ice discharge surface and ocean warming respectively and over the course of the 21st century these processes could rapidly counteract the snowfall gains predicted by present coupled climate models

strain rate effect on frictional strength and the slip nucleation process abstract kato n yamamoto k yamamoto h and hirasawa t 1992 strain rate effect on frictional strength and the slip nucleation process in t mikumo k aki m ohnaka l j ruff and p k p spudich editors earthquake source physics and earthquake precursors tectonophysics 211 269 282 the strain rate dependence of frictional strength is investigated in relation to sliding behaviour by biaxial compression tests of large scale granite samples frictional sliding is generated by increasing shear strain at a constant rate under a constant normal stress on the fault the ram displacement is held constant for a prescribed time interval between two successive sliding events so as to have the same time effect of stationary contact between sliding surfaces we obtained the following results as the strain rate increases 1 sliding becomes more unstable 2 the nucleation zone size of stick slip decreases and 3 frictional strength logarithmically increases result 3 is consistent with the previous study by dieterich 1979a and 1 and 3 are similar to the strain rate effects on failure characteristics of intact rocks reported in the literature result 3 can be explained by a rate and state dependent friction law our results suggest that the strain rate dependence of the fault strength plays an important role in controlling the nucleation process of faulting

recent antarctic ice mass loss from radar interferometry and regional climate modelling observed estimates of ice losses in antarctica combined with regional modelling of ice accumulation in the interior suggest that east antarctica is close to a balanced mass budget but large losses of ice occur in the narrow outlet channels of west antarctic glaciers and at the northern tip of the antarctic peninsula

simulating arctic climate warmth and icefield retreat in the last interglaciation in the future arctic warming and the melting of polar glaciers will be considerable but the magnitude of both is uncertain we used a global climate model a dynamic ice sheet model and paleoclimatic data to evaluate northern hemisphere high latitude warming and its impact on arctic icefields during the last interglaciation our simulated climate matches paleoclimatic observations of past warming and the combination of physically based climate and ice sheet modeling with ice core constraints indicate that the greenland ice sheet and other circum arctic ice fields likely contributed 2 2 to 3 4 meters of sea level rise during the last interglaciation

a 20 m middle pleistocene sea level highstand bermuda and the bahamas due to partial collapse of antarctic ice marine deposits at 20 3 m on the tectonically stable coastlines of bermuda and the bahamas support the hypothesis of a partial collapse of the antarctic ice sheet during the middle pleistocene beach sediments fill a sea cave at 22 m in bermuda and horizontal fenestrae filled beds crop out on platforms at two sites as high as 21 m in eleuthera bahamas carbonate beach sands are bound by an early generation of isopachous fibrous cement that is characteristic of a phreatic marine environment amino acid racemization and tims thermal ionization mass spectrometry dates constrain the age of the deposits to between 390 and 550 ka while proxy evidence supports a correlation with oxygen isotope stage 11 this direct geologic evidence of a 20 decrease in polar ice during the middle pleistocene has important implications for the stability of ice sheets during warm interglaciations

setting a chronology for the basal ice at dye 3 and grip implications for the long term stability of the greenland ice sheet abstract the long term stability of the greenland ice sheet gis is an important issue in our understanding of the climate system limited data suggest that the northern and southern sections extend well back into the pleistocene but most age constraints do not definitively date the ice here we re examine the grip and dye 3 ice cores to provide direct ice core observations as to whether the gis survived previous interglacials known to be warmer 130 ka or longer 430 ka than the present interglacial we present geochemical analyses of the basal ice from dye 3 1991 2035 m and grip 3020 3026 m that characterize and date the ice we analyzed the elemental and isotopic composition of o2 n2 and ar of trapped air in these two cores to assess the origin of trapped gases in silty ice dating of the trapped air was then achieved by measuring the paleoatmospheric 40ar 38ar and the 17o anomaly 17 of o2 the resulting age is a lower limit because the trapped air may be contaminated with crustal radiogenic 40ar the oldest average age of replicates measured at various depths is 970 140 ka for the grip ice core and 400 ka 170 ka for dye 3 17 data from dye 3 also argue strongly that basal ice in this core predates the eemian this confirms that the greenland ice sheet did not completely melt at southern greenland during the last interglacial nor did it completely melt at summit greenland during the unusually long interglacial 430 kyr before present

quaternary fluvial history of the delaware river new jersey and pennsylvania usa the effects of glaciation glacioisostasy and eustasy on a proglacial river system abstract fluvial glacial and estuarine deposits in the delaware valley record the response of the delaware river to glaciation sea level change and glacioisostasy during the quaternary incision following an early pleistocene glaciation created the present valley which is inset into a pliocene strath and fluvial plain middle and upper pleistocene and holocene deposits were laid down in this inset valley estuarine terraces in the lower valley and bayshore at 20 m probably marine isotope stage mis 11 8 m mis 5e and 3 m mis 5a or c and a fluvial deposit that correlates to offshore mis 3 marine deposits at 20 m are at elevations consistent with glacioisostatic models successive incisions during lowstands in the middle and late pleistocene lengthened deepened and narrowed the channel in the lower valley and shifted the channel westward in delaware bay during mis 2 glaciation from 25 to 18 ka the delaware was diverted to the hudson shelf valley by glacioisostatic tilting most glacial sediment was trapped in fluvial lacustrine valley fills north of the terminal moraine incision of the valley fill was accomplished during the early stage of rebound between 17 and 12 ka drainage to the delaware shelf was restored between 15 and 13 ka as the forebulge collapsed during incision multiple postglacial terraces formed where the valley was perpendicular to rebound contours and so was steepened and elevated northward and a single terrace formed where the valley paralleled the contours and there was no differential elevation or steepening about 65 of the original volume of mis 2 glacial sediment remains in the main valley and most of the eroded volume is in the channel in the lower valley beneath holocene estuarine fill little glacial sediment reached the delaware or hudson shelf overbank deposition on the lower postglacial terrace and modern floodplain spans the holocene the volume of holocene sediment in the estuary and bay yields a basinwide denudation rate of about 20 m my

interglacials of the last 800 000 years interglacials including the present holocene period are warm low land ice extent high sea level end members of glacial cycles based on a sea level definition we identify eleven interglacials in the last 800 000 years a result that is robust to alternative definitions data compilations suggest that despite spatial heterogeneity marine isotope stages mis 5e last interglacial and 11c 400 ka ago were globally strong warm while mis 13a 500 ka ago was cool at many locations a step change in strength of interglacials at 450 ka is apparent only in atmospheric co2 and in antarctic and deep ocean temperature the onset of an interglacial glacial termination seems to require a reducing precession parameter increasing northern hemisphere summer insolation but this condition alone is insufficient terminations involve rapid nonlinear reactions of ice volume co2 and temperature to external astronomical forcing the precise timing of events may be modulated by millennial scale climate change that can lead to a contrasting timing of maximum interglacial intensity in each hemisphere a variety of temporal trends is observed such that maxima in the main records are observed either early or late in different interglacials the end of an interglacial glacial inception is a slower process involving a global sequence of changes interglacials have been typically 10 30 ka long the combination of minimal reduction in northern summer insolation over the next few orbital cycles owing to low eccentricity and high atmospheric greenhouse gas concentrations implies that the next glacial inception is many tens of millennia in the future

on the origin of late holocene sea level highstands within equatorial ocean basins abstract late holocene sea level highstands of amplitude 3 m are endemic to equatorial ocean basins these highstands imply an ongoing and moderate sub mm yr sea level fall in the far field of the late pleistocene ice cover that has long been linked to the process of glacial isostatic adjustment gia clark et al 1978 mitrovica and peltier 1991 coined the term equatorial ocean syphoning to describe the gia induced sea level fall and they provided the first physical explanation for the process they argued that water migrated away from far field equatorial ocean basins in order to fill space vacated by collapsing forebulges at the periphery of previously glaciated regions we provide a complete physical explanation for the origin of equatorial ocean syphoning and the associated development of sea level highstands using numerical solutions of the equation that governs meltwater redistribution on spherical viscoelastic earth models in particular we separate the total predicted sea level change into contributions associated with ice and meltwater loading effects and by doing so isolate a second mechanism that contributes significantly to the ocean syphoning process ocean loading at continental margins induces a levering of continents and a subsidence of offshore regions that has also long been recognized within the gia literature walcott 1972 we show that the influx of water into the volume created by this subsidence produces a sea level fall at locations distant from these margins indeed over the major ocean basins that is comparable in amplitude to the syphoning mechanism isolated by mitrovica and peltier 1991

increasing rates of ice mass loss from the greenland and antarctic ice sheets revealed by grace 1 we use monthly measurements of time variable gravity from the grace gravity recovery and climate experiment satellite gravity mission to determine the ice mass loss for the greenland and antarctic ice sheets during the period between april 2002 and february 2009 we find that during this time period the mass loss of the ice sheets is not a constant but accelerating with time i e that the grace observations are better represented by a quadratic trend than by a linear one implying that the ice sheets contribution to sea level becomes larger with time in greenland the mass loss increased from 137 gt yr in 2002 2003 to 286 gt yr in 2007 2009 i e an acceleration of 30 11 gt yr2 in 2002 2009 in antarctica the mass loss increased from 104 gt yr in 2002 2006 to 246 gt yr in 2006 2009 i e an acceleration of 26 14 gt yr2 in 2002 2009 the observed acceleration in ice sheet mass loss helps reconcile grace ice mass estimates obtained for different time periods

a 550 ka record of aeolian activity near north west cape australia inferences from grain size distributions and bulk chemistry of se indian ocean deep sea sediments abstract the terrigenous fraction of sediments from a deep sea sediment core recovered from the northwestern western australian continental slope offshore north west cape se indian ocean reveals a history of western australian climate throughout the last 550 ka end member modelling of a data set of grain size distributions n 438 of the terrigenous sediment fraction allows to interpret the record in terms of aeolian and fluvial sediment deposition both related to palaeo environmental conditions in the north west cape area the data set can be best described by two aeolian end members and one fluvial one changes in the ratio of the two aeolian end members over the fluvial one are interpreted as aridity variations in northwestern western australia these grain size data are compared with bulk geochemical data obtained by xrf scans of the core log ratios of the elements zr fe and ti ca which indicate a terrigenous origin corroborate the grain size data we postulate that the mid to late quaternary near north west cape climate was relatively arid during the glacial and relatively humid during the interglacial stages owing to meridional shifts in the atmospheric circulation system opposite to published palaeo environmental records from the same latitude 20 s offshore chile and offshore namibia the australian aridity record does not show the typical southern hemisphere climate variability of humid glacials and dry interglacials which we interpret to be the result of the relatively large land mass of the australian continent which emphasises a strong monsoonal climatic system

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

elevated marine deposits in bermuda record a late quaternary megatsunami deposits of coral bearing marine shell conglomerate exposed at elevations higher than 20 m above present day mean sea level msl in bermuda and the bahamas have previously been interpreted as relict intertidal deposits formed during marine isotope stage mis 11 ca 360 420 ka before present on the strength of this evidence a sea level highstand more than 20 m higher than present day msl was inferred for the mis 11 interglacial despite a lack of clear supporting evidence in the oxygen isotope records of deep sea sediment cores we have critically re examined the elevated marine deposits in bermuda and find their geological setting sedimentary relations and microfaunal assemblages to be inconsistent with intertidal deposition over an extended period rather these deposits which comprise a poorly sorted mixture of reef lagoon and shoreline sediments appear to have been carried tens of meters inside karst caves presumably by large waves at some time earlier than ca 310 360 ka before present mis 9 11 we hypothesize that these deposits are the result of a large tsunami during the mid pleistocene in which bermuda was impacted by a wave set that carried sediments from the surrounding reef platform and nearshore waters over the eolianite atoll likely causes for such a megatsunami are the flank collapse of an atlantic island volcano such as the roughly synchronous julan or orotava submarine landslides in the canary islands or a giant submarine landslide on the atlantic continental margin

a new inference of mantle viscosity based upon joint inversion of convection and glacial isostatic adjustment data we present new profiles of mantle viscosity derived on the basis of non linear occam style joint inversions of an extensive set of data associated with mantle convection and glacial isostatic adjustment gia the convection related observables include satellite derived free air gravity harmonics the geodetically inferred excess ellipticity of the cmb and tectonic plate motions the gia constraints involve two classes of observables previously shown to be relatively insensitive to errors in the late pleistocene ice history the so called fennoscandian relaxation spectrum frs and a set of site specific decay times determined from the postglacial sea level history in hudson bay and sweden the inverted viscosity profiles show a significant three orders of magnitude increase from the upper mantle mean value of f4 10 20 pa s to a high viscosity 10 23 pa s peak at

anomalous mis 7 sea level recorded on bermuda three new u series ages from coral fragments found in the belmont formation of bermuda fall in a range of 198 ka to 196 ka these late mis 7 ages are consistent with those of 201 ka and 199 ka measured in a previous study the disputed interpretation of the belmont formation as a unit that is allostratigraphically distinct from subsequent mis 5e deposits of the rocky bay formation is vindicated by a minimum age of 196 3 ka for the total of 6 coral fragments it has yielded emergent marine deposits of the belmont formation include sedimentary lithofacies that are considered to be reliable relative sea level indicators prominent among these is a facies representing the beach step a feature that develops sub tidally directly at the base of the swash zone from this facies and others preserved along 6 km of belmont formation coastal exposure it is concluded that mis 7 relative mean sea level reached 4 5 m and likely peaked at or above 6 0 m relative to present sea level at bermuda lower mis 7 sea level positions that are evidenced and that have been quoted in the past are considered transitory positions not maxima the mis 7 sea level elevations on bermuda reconstructed in this study are above the majority of those reported from elsewhere in the world this challenges the long standing notion of bermuda as a vertically stable tide gauge but is consistent with glacio hydroisostatic models which predict land mass subsidence at intermediate field sites such as bermuda at the end of long interglacials however because of evidence of instability at bermuda in the form of seismic activity and faulting which require further investigation judgement is reserved on the global implications of this palaeo sea level anomaly

estimating the sea level highstand during the last interglacial a probabilistic massive ensemble approach essential to understanding sea level change and its causes during the last interglacial is the quantification of uncertainties in order to estimate the uncertainties we develop a statistical framework for the comparison of paleao climatic sea level index points and gia model predictions for the investigation of uncertainties as well as to generate better model predictions we implement a massive ensemble approach by applying a data assimilation scheme based on particle filter methods the different runs are distinguished through varying ice sheet reconstructions based on oxygen isotope curves and different parameter selections within the gia model this framework has several advantages over earlier work such as the ability to examine either the contribution of individual observations to the results or the probability of specific input parameters this exploration of input parameters and data leads to a larger range of estimates than previously published work we illustrate how the assumptions that enter into the statistical analysis such as the existence of outliers in the observational database or the initial ice volume history can introduce large variations to the estimate of the maximum highstand thus caution is required to avoid over interpreting results we conclude that there are reasonable doubts whether the datasets previously used in statistical analyses are able to tightly constrain the value of maximum highstand during the last interglacial lig

paleoanthropologically significant south african sea caves dated to 1 1 1 0 million years using a combination of u pb tt osl and palaeomagnetism abstract deposits in sea caves found along the southern coastline of south africa have produced a rich and detailed archaeological record of early modern humans there is however little evidence for coastal cave deposits and human occupation older than mis5e 120 ka based on the correlation of four different chronological methods we present evidence for remnant cave deposits of 1 1 1 0 ma from the quartzite sea cliff of pinnacle point near mossel bay initial uranium thorium ages at isotopic equilibrium indicated an age of 500 ka for two flowstone layers confirmed by uranium lead dating of these flowstones from 1 099 0 012 to 1 047 0 011 ma tt osl thermally transferred optically stimulated luminescence provides an age of 1 02 0 088 ma for the sand grains imbedded in the tufa underlying the flowstone and 0 720 0 066 to 0 665 0 056 for the overlying beach sediments producing an internally consistent age sequence centring on 1 0 1 1 ma the normal palaeomagnetic signal of the younger section of the flowstone is interpreted to represent the jaramillo between 1 07 and 0 99 ma there is a clear hiatus in the middle of this flowstone leading us to interpret the lower normal signal as the punaruu event at 1 115 1 1051 ma together these four techniques point to an age of 1 1 1 0 ma for these cave deposits at pinnacle point far older than anticipated the persistent presence of these 1 1 1 0 ma deposits means that the enigmatic lack of earlier stone age acheulean artefacts in the sea caves along this coastal region can no longer be explained entirely by the age of the caves or through removal of sediments by previous sea level highstands we believe that these and other coastal caves from this region if located high enough above sea level may contain deposits of great antiquity which could provide outstanding records of climate environment sea level change and human occupation back into the early to middle pleistocene

measurements of time variable gravity show mass loss in antarctica using measurements of time variable gravity from the gravity recovery and climate experiment satellites we determined mass variations of the antarctic ice sheet during 2002 2005 we found that the mass of the ice sheet decreased significantly at a rate of 152 80 cubic kilometers of ice per year which is equivalent to 0 4 0 2 millimeters of global sea level rise per year most of this mass loss came from the west antarctic ice sheet

dynamics of the last glacial maximum antarctic ice sheet and its response to ocean forcing retreat of the last glacial maximum lgm antarctic ice sheet is thought to have been initiated by changes in ocean heat and eustatic sea level propagated from the northern hemisphere nh as northern ice sheets melted under rising atmospheric temperatures the extent to which spatial variability in ice dynamics may have modulated the resultant pattern and timing of decay of the antarctic ice sheet has so far received little attention however despite the growing recognition that dynamic effects account for a sizeable proportion of mass balance changes observed in modern ice sheets here we use a 5 km resolution whole continent numerical ice sheet model to assess whether differences in the mechanisms governing ice sheet flow could account for discrepancies between geochronological studies in different parts of the continent we first simulate the geometry and flow characteristics of an equilibrium lgm ice sheet using pan antarctic terrestrial and marine geological data for constraint then perturb the system with sea level and ocean heat flux increases to investigate ice sheet vulnerability our results identify that fast flowing glaciers in the eastern weddell sea the amundsen sea central ross sea and in the amery trough respond most rapidly to ocean forcings in agreement with empirical data most significantly we find that although ocean warming and sea level rise bring about mainly localized glacier acceleration concomitant drawdown of ice from neighboring areas leads to widespread thinning of entire glacier catchments a discovery that has important ramifications for the dynamic changes presently being observed in modern ice sheets

sea level history of the past two interglacial periods new evidence from u series dating of reef corals from south florida abstract as a future warm climate analog much attention has been directed to studies of the last interglacial period or marine isotope substage mis 5 5 which occurred 120 000 years ago nevertheless there are still uncertainties with respect to its duration warmth and magnitude of sea level rise here we present new data from tectonically stable peninsular florida and the florida keys that provide estimates of the timing and magnitude of sea level rise during the last interglacial period the last interglacial high sea stand in south florida is recorded by the key largo limestone a fossil reef complex and the miami limestone an oolitic marine sediment thirty five new high precision uranium series ages of fossil corals from the key largo limestone indicate that sea level was significantly above present for at least 9000 years during the last interglacial period and possibly longer ooids from the miami limestone show open system histories with respect to u series dating but show a clear linear trend toward an age of 120 ka correlating this unit with the last interglacial corals of the key largo limestone older fossil reefs at three localities in the florida keys have ages of 200 ka and probably correlate to mis 7 these reefs imply sea level near or slightly above present during the penultimate interglacial period elevation measurements of both the key largo limestone and the miami limestone indicate that local relative sea level was at least 6 6 m and possibly as much as 8 3 m higher than present during the last interglacial period

reassessment of the potential sea level rise from a collapse of the west antarctic ice sheet theory has suggested that the west antarctic ice sheet may be inherently unstable recent observations lend weight to this hypothesis we reassess the potential contribution to eustatic and regional sea level from a rapid collapse of the ice sheet and find that previous assessments have substantially overestimated its likely primary contribution we obtain a value for the global eustatic sea level rise contribution of about 3 3 meters with important regional variations the maximum increase is concentrated along the pacific and atlantic seaboard of the united states where the value is about 25 greater than the global mean even for the case of a partial collapse

disentangling interglacial sea level and global dynamic topography analysis of madagascar abstract global inventories of stable sea level markers for the peak of the last interglacial period marine isotopic stage mis 5e play a pivotal role in determining sea level changes and in testing models of glacial isostatic adjustment here we present surveying and radiometric dating results for emergent terraces from northern madagascar which is generally regarded as a stable equatorial site fossil coral specimens were dated using conventional and open system corrected uranium series methods elevation of the upper undated terrace decreases from 33 8 m to 29 5 m over a distance of 35 km an intermediate terrace has an average radiometric age of 130 7 13 2 ka i e mis 5e its elevation decreases from 9 3 m to 2 8 m over a distance of 80 km the record of the lowest terrace is fragmentary and consists of beach rock containing rare corals with ages of 1 6 3 8 ka the spatial gradient of the mis 5e marker is inconsistent with glacio isostatic adjustment calculations instead we propose that variable elevations of this marker around madagascar and possibly throughout the indian ocean at least partly reflect spatial patterns of dynamic topography generated by sub plate mantle convection

accelerated sea level rise from west antarctica recent aircraft and satellite laser altimeter surveys of the amundsen sea sector of west antarctica show that local glaciers are discharging about 250 cubic kilometers of ice per year to the ocean almost 60 more than is accumulated within their catchment basins this discharge is sufficient to raise sea level by more than 0 2 millimeters per year glacier thinning rates near the coast during 2002 2003 are much larger than those observed during the 1990s most of these glaciers flow into floating ice shelves over bedrock up to hundreds of meters deeper than previous estimates providing exit routes for ice from further inland if ice sheet collapse is under way

late pleistocene and holocene sea level change in the australian region and mantle rheology summary spatial and temporal variations in sea level are produced by the melting of the late pleistocene ice and by the earth s response to the redistribution in surface loads by examining different parts of the sea level curves of the past 20 000 yr from geographically widely distributed regions it becomes possible to constrain models of the melting history of the ice sheets and of the earth s rheology observations from sites away from the former arctic ice sheets such as the australian and south pacific region are particularly important for constraining the total meltwater volumes added into the oceans in the past 20 000 yr and the rates at which this occurred these observations indicate that 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 9000 6000 yr ago when it may have lagged behind minor melting of the antarctic ice sheet appears to have continued throughout the late holocene differential observations of the late holocene sea level change recorded at sites in the same region are particularly useful for estimating parameters describing the earth s non elastic response to surface loading the effective parameters used here are a lithospheric thickness an upper mantle viscosity and a lower mantle viscosity describing the response below 670 km depth with the observations used here it is not possible to separate the lithospheric thickness h from the upper mantle viscosity and the viscosity results are based on the assumption that 50 h 100 km neither do these observations provide a resolution of the depth dependence of viscosity in the upper mantle and the resulting estimates are effective parameters only differential sea levels along continental margins and along the shores of large gulfs and bays constrain the effective upper mantle viscosity to be about 1 2 1020 pa s 1 while differential values from islands of different sizes are suggestive of a somewhat lower value the lower mantle taken to be below 670 km depth viscosity is about two orders of magnitude greater than this the estimated ice and rheological models explain many of the holocene sea level observations throughout the australian and southern pacific region the tilting of continental margins as exemplified by observations of variable amplitudes of the holocene high stands and the variable times at which sea levels first reached their present level along the north queensland coast and great barrier reef is well represented by these models differential holocene sea levels observed along the narrow spencers gulf of south australia are also well explained by the models and in neither case is it necessary to invoke tectonic motions predicted late holocene sea levels at small to medium sized islands are characterized by small amplitude high stands that reached their maximum values about 4000 2000 yr ago consistent with observations from the society cook and tuamotu islands

a sustained 21 m sea level highstand during mis 11 400 ka direct fossil and sedimentary evidence from bermuda abstract a small protected karstic feature exposed in a limestone quarry in bermuda preserved abundant sedimentary and biogenic materials documenting a transgressive phase still stand and regressive phase of a sea level in excess of 21 3 m above present during marine isotope stage mis 11 400 ka as determined by u th dating and amino acid racemization cobbles and marine sediments deposited during the high energy transgressive phase exhibit rim cements indicating a subsequent phreatic environment this was succeeded stratigraphically by a still stand deposition of fine calcareous lagoonal sediments containing bioclasts of red algae and benthic and planktonic foraminifera that was intensely burrowed by marine invertebrates probably upogebiid shrimp that could not be produced under any condition other than sustained marine submergence overlying this were pure carbonate beach sands of a low energy regressive phase containing abundant remains of terrestrial and marine vertebrates and invertebrates the considerable diversity of this fauna along with taphonomic evidence from seabird remains indicates deposition by high run up waves over a minimum duration of months if not years the maximum duration has yet to be determined but probably did not exceed one or two thousand years the most abundant snails in this fauna are two species indicative of brackish water and high tide line showing that a ghyben herzberg lens must have existed at 20 m the nature of these sediments and fossil accumulation is incompatible with tsunami deposition and given the absence of evidence for tectonic uplift of the bermuda pedestal or platform provide proof that sea level during mis 11 exceeded 20 m a fact that has widespread ramifications for geologists biogeographers and human demographics along the world s coastlines

accelerated west antarctic ice mass loss continues to outpace east antarctic gains a b s t r a c t article history while multiple data sources have confirmed that antarctica is losing ice at an accelerating rate different measurement techniques estimate the details of its geographically highly variable mass balance with different levels of accuracy spatio temporal resolution and coverage some scope remains for methodological improvements using a single data type in this study we report our progress in increasing the accuracy and spatial resolution of time variable gravimetry from the gravity recovery and climate experiment grace we determine the geographic pattern of ice mass change in antarctica between january 2003 and june 2014 accounting for glacio isostatic adjustment gia using the ij05 r2 model expressing the unknown signal in a sparse slepian basis constructed by optimization to prevent leakage out of the regions of interest we use robust signal processing and statistical estimation methods applying those to the latest time series of monthly grace solutions we map antarctica s mass loss in space and time as well as can be recovered from satellite gravity alone ignoring gia model uncertainty over the period 2003 2014 west antarctica has been losing ice mass at a rate of 121 8g t yr and has experienced large acceleration of ice mass losses along the amundsen sea coast of 18 5g t yr 2 doubling the mass loss rate in the past six years the antarctic peninsula shows slightly accelerating ice mass loss with larger accelerated losses in the southern half of the peninsula ice mass gains due to snowfall in dronning maud land have continued to add about half the amount of west antarctica s loss back onto the continent over the last decade we estimate the overall mass losses from antarctica since january 2003 at 92 10 gt yr

sea level history of past interglacial periods from uranium series dating of corals curacao leeward antilles islands curacao has reef terraces with the potential to provide sea level histories of interglacial periods ages of the hato upper unit of the lower terrace indicate that this reef dates to the last interglacial period marine isotope stage mis 5 5 on curacao this high sea stand lasted at least 8000 yr 126 to 118 ka elevations and age of this reef show that late quaternary uplift rates on curacao are low 0 026 0 054 m ka consistent with its tectonic setting ages of 200 ka for corals from the older cortalein unit of the lower terrace correlate this reef to mis 7 with paleo sea level estimates ranging from 3 3 m to 2 3 m the estimates are in agreement with those for mis 7 made from other localities and indicate that the penultimate interglacial period was a time of significant warmth on a par with the present interglacial period the 400 ka mis 11 middle terrace i on curacao dated by others may have formed from a paleo sea level of 8 3 to 10 0 m or less likely 17 m to 20 m the lower estimates are conservative compared to previous studies but still require major ice sheet loss from greenland and antarctica

comparison between holocene and marine isotope stage 11 sea level histories the exceptionally long interglacial warm period known as marine isotope stage 11 mis 11 428 397 ky ago vs ky vs kyr is often considered as a potential analogue for future climate development in the absence of human influence we use a new high resolution sea level record a globally integrated ice volume signal to compare mis 11 and the current interglacial holocene it is found that sea level rise into both interglacials started over similar timescales relative to the respective insolation increases and progressed up to 50 m at similar rates of 1 0 1 2 m per century subsequent weak insolation changes anomalously prolonged the mis11 deglaciation over more than 20 ky the main sea level highstand was achieved at the second mis 11 insolation maximum with a timing closely equivalent to that of the holocene highstand compared to its single insolation maximum consequently while mis 11 was an exceptionally long period of interglacial warmth its ice volume minimum sea level highstand lasted less than 10 ky which is similar to the duration of other major interglacials comparison of the ends of mis 11 and the holocene based on timings relative to their respective maxima in mean 21 june insolation at 65 n suggests that the end of holocene conditions might have been expected 2 0 2 5 ky ago instead interglacial conditions have continued with co2 temperature and sea level remaining high or increasing this apparent discrepancy highlights the need to consider that a comparisons may need to focus on other orbital control indices in which case the discrepancy can vanish and or b the feedback mechanisms that dominate the planetary energy balance may have become decoupled from insolation during the past 2millennia

ice retreat in wilkes basin of east antarctica during a warm interglacial efforts to improve sea level forecasting on a warming planet have focused on determining the temperature sea level and extent of polar ice sheets during earth s past interglacial warm periods1 3 about 400 000 years ago during the interglacial period known as marine isotopic stage 11 mis11 the global temperature was 1 to 2 degrees celsius greater2 and sea level was 6 to 13 metres higher1 3 sea level estimates in excess of about 10 metres however have been discounted because these require a contribution from the east antarctic ice sheet3 which has been argued to have remained stable for millions of years before and includes mis114 5 here we show how the evolution of 234u enrichment within the subglacial waters of east antarctica recorded the ice sheet s response to mis11 warming within the wilkes basin subglacial chemical precipitates of opal and calcite record accumulation of 234u the product of rock water contact within an isolated subglacial reservoir up to 20 times higher than that found in marine waters the timescales of 234u enrichment place the inception of this reservoir at mis11 informed by the 234u cycling observed in the laurentide ice sheet where 234u accumulated during periods of ice stability6 and was flushed to global oceans in response to deglaciation7 we interpret our east antarctic dataset to represent ice loss within the wilkes basin at mis11 the 234u accumulation within the wilkes basin is also observed in the mcmurdo dry valleys brines8 10 indicating11 that the brine originated beneath the adjacent east antarctic ice sheet the marine origin of brine salts10 and bacteria12 implies that mis11 ice loss was coupled with marine flooding collectively these data indicate that during one of the warmest pleistocene interglacials the ice sheet margin at the wilkes basin retreated to near the precipitate location about 700 kilometres inland from the current position of the ice margin which assuming current ice volumes would have contributed about 3 to 4 metres13 to global sea levels

coccolithophore variability across marine isotope stage 11 in the pacific sector of the southern ocean and its potential impact on the carbon cycle proxy based reconstructions of past changes in the marine biological carbon pumps are limited especially in the southern ocean this work provides new insights into the productivity variations in the pacific sector of the southern ocean we present new data derived from three sediment cores that show glacial interglacial coccolithophore variability across marine isotope stage 11 mis 11 the cores were retrieved during r v polarstern cruise ps75 from the subantarctic zone and polar front zone at the western flank of the east pacific rise and in the vicinity of the antarctic pacific ridge coccolithophore assemblages were overwhelmingly dominated by the species gephyrocapsa caribbeanica and small gephyrocapsa total numbers of coccoliths coccolith accumulation rates coccolith fraction cf 20 m fraction sr ca data and temperature corrected cf sr ca records consistently showed an increase in coccolithophore productivity during termination v mis 12 11 boundary highest productivity throughout mis 11 424 374 kyr and a decrease during late mis 11 in all the cores we end with a discussion of back calculated coccolith calcification rate in the surface ocean and its potential contribution to changes in the concentration of atmospheric co2

towards assessing the influence of sediment loading on last interglacial sea level locally the elevation of last interglacial lig 122 ka sea level markers is modulated by processes of vertical displacement such as tectonic uplift or glacial isostatic adjustment and these processes must be accounted for in deriving estimates of global ice volumes from geological sea level records the impact of sediment loading on lig sea level markers is generally not accounted for in these corrections as it is assumed that the impact is negligible except in extremely high depositional settings such as the world s largest river deltas here we perform a generalized test to assess the extent to which sediment loading may impact global variability in the present day elevation of lig sea level markers we numerically simulate river sediment deposition using a diffusive model that incorporates a migrating shoreline to construct a global history of sedimentation over the last glacial cycle we then calculate sea level changes due to this sediment loading using a gravitationally self consistent model of glacial isostatic adjustment and compare these predictions to a global compilation of lig sea level data we perform a statistical analysis which accounts for spatial autocorrelation across a global compilation of 1287 lig sea level markers though limited by uncertainties in the lig sea level database and the precise history of river deposition this analysis suggests there is not a statistically significant global signal of sediment loading in lig sea level markers nevertheless at sites where lig sea level markers have been measured local sea level predicted using our simulated sediment loading history is perturbed up to 16 m more generally these predictions establish the relative sensitivity of different regions to sediment loading finally we consider the implications of our results for estimates of tectonic uplift rates derived from lig marine terraces we predict that sediment loading causes 5 10 m of subsidence over the last glacial cycle at specific locations along active margin regions such as california and barbados where deriving long term tectonic uplift rates from lig shorelines is a common practice

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

accelerated antarctic ice loss from satellite gravity measurements accurate quantification of antarctic ice sheet mass balance and its contribution to global sea level rise remains challenging gravity recovery and climate experiment data spanning the period april 2002 to january 2009 confirm earlier estimates of ice loss for antarctica and indicate that east antarctica started losing mass in about 2006

relative sea level variability during the late middle pleistocene new evidence from eastern england unravelling patterns of relative sea level change during previous interglacials enhances our understanding of ice sheet response to changing climate temperate latitude estuarine environments have the potential to preserve continuous records of relative sea level from previous interglacial warm periods this is important because currently we typically only have snapshots of sea level highstands from low latitude corals and raised palaeoshoreline indicators while the continuous deep sea oxygen isotope record only provides indirect evidence of sea level changes here we focus on the nar valley in eastern england in which is preserved evidence of a late middle pleistocene marine transgression more than 20 vertical metres in extent by applying a model of coastal succession and sea level tendencies as used in holocene sea level studies we assess the mode abrupt versus gradual of sea level change recorded by the interglacial nar valley sequences compiled palaeo stratigraphic evidence comprising foraminifera pollen and amino acid racemization dating suggests that the mode of sea level change in the nar valley interglacial sequence was gradual with potentially two phases of regional transgression and relative sea level rise occurring at two separate times the first phase occurred during the latter part of marine oxygen isotope stage mis 11 from 8 to 18 m od and the second phase potentially occurred during early mis 9 from 3 to 3 m od with long term tectonic uplift included in these estimates we cannot conclusively preclude an alternative mis 11 age for these lower sediments the lack of indicators for rapid sea level oscillations in the nar valley adds weight to an argument for steady melt of the ice sheets during both mis 11 and 9