global ice sheet system interlocked by sea level abstract denton and hughes 1983 quaternary research 20 125 144 postulated that sea level linked a global ice sheet system with both terrestrial and grounded marine components during late quaternary ice ages summer temperature changes near northern hemisphere melting margins initiated sea level fluctuations that controlled marine components in both polar hemispheres it was further proposed that variations of this ice sheet system amplified and transmitted milankovitch summer half year insolation changes between 45 and 75 n into global climatic changes new tests of this hypothesis implicate sea level as a major control of the areal extent of grounded portions of the antarctic ice sheet thus fitting the concept of a globally interlocked ice sheet system but recent atmospheric modeling results manabe and broccoli 1985 journal of geophysical research 90 2167 2190 suggest that factors other than areal changes of the grounded antarctic ice sheet strongly influenced southern hemisphere climate and terminated the last ice age simultaneously in both polar hemispheres atmospheric carbon dioxide linked to high latitude oceans is the most likely candidate shackleton and pisias 1985 atmospheric carbon dioxide orbital forcing and climate in the carbon cycle and atmospheric co2 natural variations archean to present e t sundquest and w s broecker eds pp 303 318 geophysical monograph 32 american geophysical union washington d c but another potential influence was high frequency climatic oscillations 2500 yr it is postulated that variations in atmospheric carbon dioxide acted through an antarctic ice shelf linked to the grounded ice sheet to produce and terminate southern hemisphere ice age climate it is further postulated that milankovitch summer insolation combined with a warm high frequency oscillation caused marked recession of northern hemisphere ice sheet melting margins and the north atlantic polar front about 14 000 14c yr b p this permitted renewed formation of north atlantic deep water which could well have controlled atmospheric carbon dioxide w s broecker d m peteet and d rind 1985 nature london 315 21 26 combined melting and consequent sea level rise from the three warming factors initiated irreversible collapse of the interlocked global ice sheet system which was at its largest but most vulnerable configuration

wind effects on estimates of sea level rise 1 variability in sea level at the longest periods observable in modern records has recently been found to be well correlated with local atmospheric pressure at shorter periods however longshore winds are known to be one of the primary mechanisms for forcing sea level variability on the eastern margins of the ocean there is a remarkable 80 mm drop in mean sea level on both the eastern north pacific and north atlantic coasts between the late 1800s and early 1900s it is found here to be in agreement with longshore wind forcing from the equator up to the latitude of the observed tide stations better resolved data beginning in 1960 show that the delay near the annual period between wind forcing and sea level is approximately 1 month the relative high in sea level in the late 1800s on the west coast of europe appears to have propagated westward across the atlantic as a long rossby wave and then to have been seen on the east coast of the united states because many features in long term sea level variability are correlated with wind forcing on time scales from annual to decades it will be prudent to base conclusions about long term sea level rise on the longest records available the results here are based on forcing by longshore winds the related issue of the extent to which open ocean wind curl may also be responsible is not addressed here nor the extent to which coastal sea level observations are representative of the open ocean

a new late holocene sea level record from the mississippi delta evidence for a climate sea level connection abstract a detailed relative sea level rsl record was constructed for the time interval 600 1600 ad using basal peat to track sea level and containing 16 sea level index points that capture 60 cm of rsl rise the study area is in the mississippi delta where the spring tidal range is 0 47 m the impact of ocean currents on sea surface topography is limited and crustal motions are well constrained age control was obtained by ams 14 c dating and most ages represent weighted means of two subsamples sample elevations were determined by combining differential gps measurements with optical surveying all index points were plotted as error boxes using 2 confidence intervals for the ages plus all vertical errors involved in sampling and surveying as well as the indicative range of the samples a striking clustering of sea level index points between 1000 and 1200 ad suggests a possible acceleration in the rate of rsl rise removal of the long term trend 0 60 mm yr 1 allows for the possibility of a sea level oscillation with a maximum amplitude of 55 cm however given the size of the error boxes the possibility that oscillations did not occur cannot be entirely ruled out comparison of the new rsl record with various proxy climate records suggests that sea level in this area may have responded to hemispheric temperature changes including the medieval warm period and the little ice age however given the error margins associated with this reconstruction it is stressed that this causal mechanism is tentative and requires corroboration by high resolution sea level reconstructions elsewhere

regional patterns of sea level change related to interannual variability and multidecadal trends in the atlantic meridional overturning circulation some studies of ocean climate model experiments suggest that regional changes in dynamic sea level could provide a valuable indicator of trends in the strength of the atlantic meridional overturning circulation moc this paper describes the use of a sequence of global ocean ice model experiments to show that the diagnosed patterns of sea surface height ssh anomalies associated with changes in the moc in the north atlantic na depend critically on the time scales of interest model hindcast simulations for 1958 2004 reproduce the observed pattern of ssh variability with extrema occurring along the gulf stream gs and in the subpolar gyre spg but they also show that the pattern is primarily related to the wind driven variability of moc and gyre circulation on interannual time scales it is reflected also in the leading eof of ssh variability over the na ocean as described in previous studies the pattern however is not useful as a fingerprint of longer term changes in the moc as shown with a companion experiment a multidecadal gradual decline in the moc of 5 sv 1 sv 106 m3 s 1 over 5 decades induces a much broader basin scale ssh rise over the mid to high latitude na with amplitudes of 20 cm the detectability of such a trend is low along the gs since low frequency ssh changes are effectively masked here by strong variability on shorter time scales more favorable signal to noise ratios are found in the spg and the eastern na where a moc trend of 0 1 sv yr 1 would leave a significant imprint in ssh already after about 20 years

onset of recent rapid sea level rise in the western atlantic ocean a high resolution record of sea level change spanning the past 1000 years is derived from foraminiferal and chronological analyses of a 2 m thick salt marsh peat sequence at chezzetcook nova scotia canada former mean tide level positions are reconstructed with a precision of 0 055 m using a transfer function derived from distributions of modern salt marsh foraminifera our age model for the core section older than 300 years is based on 19 ams 14c ages and takes into account the individual probability distributions of calibrated radiocarbon ages the past 300 years is dated by pollen and the isotopes 206pb 207pb 210pb 137cs and 241am between ad 1000 and ad 1800 relative sea level rose at a mean rate of 17 cm per century apparent pre industrial rises of sea level dated at ad 1500 1550 and ad 1700 1800 cannot be clearly distinguished when radiocarbon age errors are taken into account furthermore they may be an artefact of fluctuations in atmospheric 14c production in the 19th century sea level rose at a mean rate of 1 6 mm yr between ad 1900 and ad 1920 sea level rise accelerated to the modern mean rate of 3 2 mm yr this acceleration corresponds in time with global temperature rise and may therefore be associated with recent global warming 2005 elsevier ltd all rights reserved

searching for eustasy in deglacial sea level histories abstract perturbations to the earth s gravity field and solid surface associated with glacial isostatic adjustment gia cause the total observable sea level change to depart from the eustatic curve which is defined as a spatially uniform height shift of the ocean surface to accommodate any mass gained lost from grounded ice in this study we apply a state of the art model of gia induced sea level change to quantify the magnitude and spatial form of this departure at the global scale for a range of model parameters with an aim to identify regions that are well suited to obtain accurate and precise estimates of eustatic sea level and therefore past grounded ice volume in general our results indicate that eustatic sea level is not a directly measurable quantity and so must be estimated by subtracting a model derived estimate of non eustatic contributions from observations in this regard we use our results to isolate regions where this procedure can be applied with optimal accuracy and precision that is where 1 the gia predictions are relatively insensitive to plausible ranges in input parameters and 2 where the non eustatic contribution is small i e the predicted sea level closely approximates the eustatic value we present maps that can be employed by the field community to identify areas where sea level reconstructions would be well suited to arrive at robust estimates of eustatic sea level note that sea level changes associated with tectonic motion and changes in ocean water temperature salinity which also lead to departures from eustasy are not considered in this analysis

recent controversies in predicting post glacial sea level change abstract we compare recent developments in the numerical prediction of post glacial sea level changes and comment on the controversies associated with these developments we conclude that 1 the broad shelf effect discussed by peltier and drummond 2002 in the context of water load modelling at migrating shorelines is incorporated into the sea level algorithms of johnston 1993 and milne et al 1999 and 2 the procedure used by yokoyama et al 2000 to infer an ice equivalent post lgm sea level rise of 130 135 m is technically sound

millennial scale variability in antarctic ice sheet discharge during the last deglaciation two well dated high resolution records of iceberg rafted debris are presented that document variability in antarctic ice sheet discharge during the last deglaciation global sea levels have risen by more than 100 metres since the last glacial maximum around 20 000 years ago with several meltwater pulses of several metres or more in the most dramatic of these meltwater pulse 1a sea level rose by about 16 metres at 14 600 years ago this magnitude of sea level rise strongly suggests major antarctica contributions but to date there has been no firm physical evidence now michael weber and colleagues present a record of iceberg rafted debris from the scotia sea and show clear signals of pulsed iceberg release from antarctica as early as 19 000 years ago the largest iceberg release occurred during meltwater pulse 1a providing the long sought confirmation of antarctic contributions to this major jump in sea level rise our understanding of the deglacial evolution of the antarctic ice sheet ais following the last glacial maximum 26 000 19 000 years ago 1 is based largely on a few well dated but temporally and geographically restricted terrestrial and shallow marine sequences2 3 4 this sparseness limits our understanding of the dominant feedbacks between the ais southern hemisphere climate and global sea level marine records of iceberg rafted debris ibrd provide a nearly continuous signal of ice sheet dynamics and variability ibrd records from the north atlantic ocean have been widely used to reconstruct variability in northern hemisphere ice sheets5 but comparable records from the southern ocean of the ais are lacking because of the low resolution and large dating uncertainties in existing sediment cores here we present two well dated high resolution ibrd records that capture a spatially integrated signal of ais variability during the last deglaciation we document eight events of increased iceberg flux from various parts of the ais between 20 000 and 9 000 years ago in marked contrast to previous scenarios which identified the main ais retreat as occurring after meltwater pulse 1a3 6 7 8 and continuing into the late holocene epoch the highest ibrd flux occurred 14 600 years ago providing the first direct evidence for an antarctic contribution to meltwater pulse 1a climate model simulations with ais freshwater forcing identify a positive feedback between poleward transport of circumpolar deep water subsurface warming and ais melt suggesting that small perturbations to the ice sheet can be substantially enhanced providing a possible mechanism for rapid sea level rise

mid pacific microatolls record sea level stability over the past 5000 yr there has been geographical variation in sea level since rapid postglacial melting of polar ice ceased similar to 6 k y ago reflecting isostatic adjustments of earth and ocean surfaces to past and ongoing redistribution of ice and water loads a new data set of over 100 fossil microatolls from christmas kiritimati island provides a holocene sea level record of unparalleled continuity living reef flat corals grow up to a low tide level adjacent fossil microatolls long lived porites corals up to several meters in diameter occur at similar elevations 0 1 m and extensive fossil microatolls in the island interior are at consistent elevations within each population collectively they comprise an almost continuous sequence spanning the past 5 k y indicating that locally sea level has been within 0 25 m of its present position and precluding global sea level oscillations of one or more meters inferred from less stable locations or using other sea level indicators this mid pacific atoll is tectonically stable and far from former ice sheets the precisely surveyed and radiometrically dated microatolls indicate that sea level has not experienced significant oscillations in accordance with geophysical modeling which implies that the eustatic contribution from past ice melt and the isostatic adjustment of the ocean floor to loading largely cancel each other at this site

response of the global ocean to greenland and antarctic ice melting 1 we investigate the transient response of the global ocean circulation to enhanced freshwater forcing associated with melting of the greenland and antarctic ice sheets increased freshwater runoff from greenland results in a basin wide response of the north atlantic on timescales of a few years communicated via boundary waves equatorial kelvin waves and westward propagating rossby waves in addition modified air sea interaction plays a fundamental role in setting up the basin scale response of the atlantic circulation in its subpolar and subtropical gyres in particular the modified ocean dynamics and thermodynamics lead to a depression in the central north and south atlantic that would not be expected from linear wave dynamics moreover the heat content increases on basin and global scales in response to anomalous freshwater forcing from greenland suggesting that the ocean s response to enhanced freshwater forcing would be a coupled problem other parts of the world ocean experience a much slower adjustment in response to greenland freshwater forcing communicated via planetary waves but also involving advective diffusive processes especially in the southern ocean over the 50 years considered here most of the sea level increase associated with freshwater input from greenland remains in the atlantic ocean in contrast ice melting around antarctica has a much reduced effect on the global ocean in both cases none of the basins came to a stationary state during the 50 year experiment

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

simulation of large scale coastal change using a morphological behaviour model abstract quantitative simulation of large scale coastal behaviour lscb is possible using a model based only on principles of sand mass conservation and geometric rules for shoreface and active sand body morphology dynamic processes are subsumed into a set of parameters that define the geometry of the active cross shore profile which in turn can represent an entire coastal cell the parameters together with a set of local behaviour rules governing adjustments at discrete points along the profile provide a simple formulation that is constrained by sediment mass balance to yield emergent numerical solutions for profile kinematics the emergent qualities of this shoreface translation model are exemplified in simulation experiments on changes to sand deposits on the southeastern australian coast and shelf during the post glacial marine transgression in another example the model is used to simulate lscb over engineering time scales at an idiosyncratic site both examples illustrate the over riding importance of small residual sand movements that accumulate through time to cause lscb in comparison to gross sand movements the residuals are too small to measure directly or predict on the basis of available theory exploratory inverse simulation provides a quantitative method for side stepping these limitations the shoreface translation model therefore is used as a tool to explore possible forms of coastal behaviour through an approach that incorporates available data along with theoretical considerations validation is not strictly possible for this type of inverse approach so the degree to which a simulation reproduces observed features in nature is a measure of its success

late holocene great earthquakes in the eastern part of the aleutian megathrust abstract the great earthquake mw 9 2 of ad 1964 may not be typical of other megathrust earthquakes in the region during the last 4000 years we present new field data from three sites copper river delta the lower katalla river valley and puffy slough to enhance the temporal and spatial resolutions of the paleoseismic records of multiple great earthquakes differences in the spatial patterns of coseismic uplift and subsidence suggest different rupture combinations of the kodiak prince william sound and western yakutat segments of the plate boundary the longest and most comprehensive records all come from the prince william sound segment most sites here reveal net subsidence over multiple earthquake cycles except where probable upper plate faulting contributes locally to net uplift with measurable differences between sites only a few kilometres apart we identify the katalla area as a source of local seismic hazard similar to other locations in the western part of the yakutat microplate including the two mw8 ruptures in ad 1899 we use a bayesian radiocarbon modelling approach to estimate the age and recurrence intervals of multiple great earthquakes for the prince william sound segment of the megathrust the long interval 883 34 2 years between the penultimate earthquake and ad 1964 contrasts with the older earthquakes that have intervals ranging from 420 to 610 years with a mean of 535 years

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

salt marsh reconstructions of relative sea level change in the north atlantic during the last 2000 years abstract sea level changes record changes in the mass balance of ice sheets and mountain glaciers as well as dynamic ocean atmosphere processes unravelling the contribution of each of these mechanisms on late holocene timescales ideally requires observations from a number of sites on several coasts within one or more oceans we present the first 2000 year long continuous salt marsh based reconstructions of relative sea level rsl change from the eastern north atlantic and uniquely from a slowly uplifting coastline we develop three rsl histories from two sites in north west scotland to test for regional changes in sea level tendency a positive tendency indicating an increase in the proximity of marine conditions and a negative tendency the reverse whilst at the same time highlighting methodological issues including the problems of dataset noise when applying transfer functions to fossil salt marsh sequences the records show that rsl has been stable 0 4 m during the last two millennia and that the regional sea level tendency has been negative throughout most of the record lengths a recent switch in the biostratigraphy of all three records indicating a regional positive tendency means we cannot reject the hypothesis of a 20th century sea level acceleration occurring in north west scotland that must have exceeded the rate of background rsl fall 0 4 mm yr 1 but this signal appears muted and later than recorded from the western north atlantic

can long term variability in the gulf stream transport be inferred from sea level recent studies by sturges and collaborators suggest a simple but powerful technique to estimate climatic changes in the transport of the gulf stream from the difference between the oceanic sea level calculated with a simple wind driven rossby wave model and the observed coastal sea level the hypothesis behind this technique is tested using 40 years of data 1950 to 1989 obtained from a three dimensional atlantic ocean model forced by observed surface data the analysis shows that variations in sea level difference between the ocean and the coast are indeed coherent with variations of the gulf stream transport for periods shorter than 1 year or longer than 4 5 years the results obtained from the three dimensional model confirm the findings of the simple rossby wave model that decadal climatic changes in the gulf stream transport vary considerably with latitude

lateglacial and holocene water level variations along the ne german baltic sea coast review and new results abstract a comprehensive overview is given of the current knowledge regarding the lateglacial and holocene water table evolution along the west pomeranian coast which is related to the four evolutionary stages of the baltic sea the baltic ice lake the yoldia sea the ancylus lake and the littorina sea the first three stages were characterized by intensive water table fluctuations in the baltic basin the balance between glacio isostatic uplift and water table rise due to meltwater and river discharge produced either a temporary connection with the ocean or isolation from it new findings are presented on the water levels reached during the different stages only at about 8 ky bp did the baltic obtain a permanent connection with the ocean the first marine sediments in the recent coastal zone ca 7 8 ky old are found at 15 m and are related to the initial littorina sea the maximum of the main littorina transgression was reached at 1 5 m to 2 0 m ca 5 8 ky bp the course of the sea level reveals that later only some minor oscillations took place correlated with climatic fluctuations these indicate a control by regional changes in the north atlantic circulation rather than by global sea level alterations isostatic movements were determined by comparing the reconstructed relative sea level curve with curves assumed as nearly eustatic the resulting isostatic curve shows uplift at 11 5 ky bp of about 55 m which decreased until 7 8 ky bp to 6 m and ceased at ca 3 ky bp currently the coastal zone experiences a slight tilting with uplift in the northeastern part and inundation in the southwestern area

meltwater pulse 1a from antarctica as a trigger of the bolling allerod warm interval meltwater pulse 1a mwp 1a was a prominent feature of the last deglaciation which led to a sea level rise of 20 meters in less than 500 years concurrent with mwp 1a was the onset of the bolling allerod interstadial event 14 600 years before the present which marked the termination of the last glacial period previous studies have been unable to reconcile a warm northern hemisphere with mwp 1a originating from the laurentide or fennoscandian ice sheets with the use of a climate model of intermediate complexity we demonstrate that with mwp 1a originating from the antarctic ice sheet consistent with recent sea level fingerprinting inferences the strength of north atlantic deep water nadw formation increases thereby warming the north atlantic region and providing an explanation for the onset of the bolling allerod warm interval the established mode of active nadw formation is then able to respond to subsequent freshwater forcing from the laurentide and fennoscandian ice sheets setting the stage for the younger dryas cold period the melting of continental ice sheets during the last deglaciation provided a freshwater source to the ocean that affected global sea level and the strength of the thermohaline circulation an exceptionally large melting event inferred from far field relative sea level records occurred

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

tidal evolution of the northwest european shelf seas from the last glacial maximum to the present 1 two dimensional paleotidal simulations have been undertaken to investigate tidal and tide dependent changes tidal amplitudes tidal current velocities seasonal stratification peak bed stress vectors that have occurred in the nw european shelf seas during the last 20 ka the simulations test the effect of shelf wide isostatic changes of sea level by incorporating results from two different crustal rebound models and the effect of the ocean tide variability by setting open boundary values either fixed to the present state or variable according to the results of a global paleotidal model the use of the different crustal rebound models does not affect the overall changes in tidal patterns but the timing of the changes is sensitive to the local isostatic effects that differ between the models the incorporation of ocean tide changes greatly augments the amplitude of tides and tidal currents in the celtic and malin seas before 10 ka bp and has a large impact on the distribution of seasonally stratified conditions magnitude of peak bed stress vectors and tidal dissipation in the shelf seas the predictions on seasonal stratification are supported by well dated evidence on tidal mixing front migration in the celtic sea additional experiments using the global model suggest that the variability of offshore tides has been caused mainly by changes of eustatic sea level and ice sheet extent in particular a large decrease observed at 10 8 ka bp is attributed to the opening of hudson strait accompanied by the retreat of the laurentide ice sheet

contrasting records of sea level change in the eastern and western north atlantic during the last 300 years we present a new 300 year sea level reconstruction from a salt marsh on the isle of wight central english channel uk that we compare to other salt marsh and long tide gauge records to examine spatial and temporal variability in sea level change in the north atlantic our new reconstruction identifies an overall rise in relative sea level rsl of c 0 30 m since the start of the eighteenth century at a rate of 0 9 0 3 mmyr 1 error in variables changepoint analysis indicates that there is no statistically significant deviation from a constant rate within the dataset the reconstruction is broadly comparable to other tide gauge and salt marsh records from the european atlantic demonstrating coherence in sea level in this region over the last 150 300 years in contrast we identify significant differences in the rate and timing of rsl with records from the east coast of north america the absence of a strong late 19th early 20th century rsl acceleration contrasts with that recorded in salt marsh sediments along the eastern usa coastline in particular in a well dated and precise sea level reconstruction from north carolina this suggests that this part of the north carolina sea level record represents a regionally specific sea level acceleration this is significant because the north carolina record has been used as if it were globally representative within semi empirical parameterisations of past and future sea level change we conclude that regional scale differences of sea level change highlight the value of using several regionally representative rsl records when calibrating and testing semi empirical models of sea level against palaeo records this is because by using records that potentially over estimate sea level rise in the past such models risk over estimating sea level rise in the future

the sea level fingerprint of the 8 2 ka climate event the 8 2 ka cooling event was an abrupt widespread climate instability there is general consensus that the episode was likely initiated by a catastrophic outflow of proglacial lakes agassiz and ojibway through the hudson strait with subsequent disruption of the atlantic meridional overturning circulation however the total discharge and flux during the 8 2 ka event remain uncertain we compute the sea level signature or fingerprint associated with the drainage of lakes agassiz and ojibway as well as the expected sea level signal over the same time period due to glacial isostatic adjustment gia in response to the late pleistocene deglaciation our analysis demonstrates that sites relatively close to the lakes including the west and gulf coasts of the united states have small signals due to the lake release and potentially large gia signals and thus they may not be optimal field sites for constraining the outflow volume other sites such as the east coast of south america and western africa have significantly larger signals associated with the lake release and are thus better choices in this regard

sea level climate correlation during the past 1400 yr we present a new mean high water curve for hammock river marsh clinton connecticut obtained by improving the age model for an existing record of relative marsh elevation based on foraminiferal analysis of a 1 8 m long peat core unlike the earlier curve the new curve confirms trend changes in mean high water rise during the past 1400 yr as noted for salt marshes 15 km farther west suggesting a regional cause these trend changes and century scale mean high water variations in the clinton record correlate positively with large scale regional variations in sea surface and summer air temperature indicating a link between sea level and the climate ocean system on the basis of the clinton mean high water curve we conclude that real sea level oscillated centimeters to decimeters on a century time scale over the past 1400 yr was 25 25 cm higher ca a d 1050 medieval warm period than ca a d 1650 little ice age and rose at a mean rate of 1 mm yr 1 over the past 350 yr there was little or no rise during the cool 1800s

development of a foraminifera based transfer function in the basque marshes n spain implications for sea level studies in the bay of biscay abstract in order to reconstruct former sea level we have developed a foraminifera based transfer function using three models based on a modern dataset of 59 samples and 23 species obtained from four basque marshes in northern spain the relationship between observed and foraminifera predicted elevation illustrated the strong performance of the transfer function r 2 jack ranges from 0 74 to 0 81 these results indicated that precise reconstructions of former sea levels are possible error ranges from 0 11 to 0 19 m the transfer function was used to calibrate the foraminiferal assemblages collected from a 50 cm salt marsh core we placed the foraminifera based reconstructions into a temporal framework using 137 cs pb concentrations and 210 pb derived sediment accumulation rates the resulting relative sea level curve is in good agreement with regional tide gauge data both instrumental data and microfossil records suggest a rate of relative sea level rise of approximately 2 mm yr 1 for the 20th century

high resolution numerical modeling of tides in the western atlantic gulf of mexico and caribbean sea during the holocene 1 tidal constituents and datums are computed on a high resolution grid of the northwestern atlantic ocean including the gulf of mexico and the caribbean sea a global model is used to determine tidal parameters on a grid with a nominal resolution of 800 800 the global model includes self attraction and loading drag in shallow marginal seas and internal tide drag in the deep ocean simulations are performed at 1000 year intervals during the holocene 10 000 calibrated years before present 10 ka in combination with changes in bathymetry and coastline location derived from a glacial isostatic adjustment model the global model results are then used to force a regional barotropic tidal model the regional model uses an unstructured finite element grid with very high resolution at the coastline the model results reveal significant variations in tidal constituent amplitudes throughout the holocene in the northwestern atlantic semi diurnal components show a strong amplification at around 9 ka while in the gulf of mexico the response is much more muted variations in diurnal tidal parameters are found to be less significant than semi diurnal parameters throughout the model domain changes in tidal range of great relevance to changes in relative sea level rsl are also investigated throughout the holocene the overall structure is similar to the patterns observed in the m2 tide with peak increases of 200 300 relative to present day being observed along the east coast of the united states from 9 to 8 ka finally the high spatial resolution of the regional model allows for the investigation of tidal changes at spatial scales e g individual bays much smaller than in previous studies

late quaternary relative sea level change in the western gulf of maine evidence for a migrating glacial forebulge new radiocarbon dated cores obtained by vibracorers in the western gulf of maine confirm that a short lived relative sea level lowstand of 55 m occurred at 11 10 5 ka these cores and younger salt marsh data also reveal that rates of transgression varied throughout the holocene probably due to local variations in glacial isostasy the isostatic component is resolved by subtracting published approximations of eustatic sea level from our well determined observations of local relative sea level a large peak in the isostatic curve coincides with the lowstand and is interpreted as a forebulge 20 25 m in amplitude forebulge migration is estimated at 7 11 km 100 yr based on the timing of lowstands across the region

patterns of holocene relative sea level change in the north of britain and ireland temporal and spatial patterns of relative sea level rsl change in the north of britain and ireland during the holocene are examined four episodes each defined by marked changes in the rsl trend are identified each episode is marked by a rise to a culminating shoreline followed by a fall episode hrsl 1 dates from the younger dryas to early in the holocene hrsl 2 to hrsl 4 occurred later in the holocene there is extensive evidence for each episode and on this basis the spatial distribution of the altitude data for three culminating shorelines and a shoreline formed at the time of the holocene storegga slide tsunami ca 8110 100 cal bp is analysed ordinary kriging is used to determine the general pattern following which gaussian trend surface analysis is employed recognising that empirical measurements of rsl change can be unevenly distributed spatially a new approach is introduced which enables the developing pattern to be identified the patterns for the most widely occurring shorelines were analysed and found to be similar and common centre and axis models were developed for all shorelines the analyses described provide models of the spatial pattern of holocene rsl change in the area between ca 8100 cal bp and ca 1000 cal bp based on 2262 high resolution shoreline altitude measurements these models fit the data closely no shoreline altitude measurement lying more than 1 70 m or 1 82 m from the predicted value the models disclose a similar pattern to a recently published glacial isostatic adjustment model for present rsl change across the area indicating that the overall spatial pattern of rsl change may not have varied greatly during the last ca 8000 years

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

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

paleogeography glacially induced crustal displacement and late quaternary coastlines on the continental shelf of british columbia canada abstract subsequent to the last glacial maximum lgm complex isostatic adjustments resulted from deglaciation eustatic sea level change tectonic faulting and a relatively thin flexible lithosphere in the queen charlotte islands qci region a geostatistical interpolation model charts the sequence of evolving landscapes and displays temporal changes in the magnitudes and extent of crustal flexure that accompanied forebulge development on the late quaternary northeast pacific continental shelf between 14 2 and 8 7 ka bp wavelength and forebulge amplitude are consistent with thermal modeling implying low upper mantle viscosity and thin elastic lithospheric thickness beneath queen charlotte qc sound and hecate strait glacial ice 690 m thick began retreating from dixon entrance after 14 5 ka bp 14c years ago and prior to 12 6 ka bp permitting over 100 m of crustal uplift in northern hecate strait a forebulge persisted in hecate strait and qc sound from 13 2 until after 9 7 ka bp implying fixed glacial ice on the british columbia bc mainland until 10 ka bp paleogeographic reconstructions show two emergent ice free terrains one extending eastward from the qci and the other in qc sound by 11 7 ka bp a landbridge connected the bc mainland and the qci

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

stratigraphic evidence for an early holocene earthquake in aceh indonesia abstract the holocene stratigraphy of the coastal plain of the aceh province of sumatra contains 6 m of sediment with three regionally consistent buried soils above pre quaternary bedrock or pre holocene unconsolidated sediment litho bio and chronostratigraphic analyses of the lower buried soil reveals a rapid change in relative sea level caused by coseismic subsidence during an early holocene megathrust earthquake evidence for paleoseismic subsidence is preserved as a buried mangrove soil dominated by a pollen assemblage of rhizophora and or bruguiera ceriops taxa the soil is abruptly overlain by a thin tsunami sand the sand contains mixed pollen and abraded foraminiferal assemblages of both offshore and onshore environments the tsunami sand grades upward into mud that contains both well preserved foraminifera of intertidal origin and individuals of the gastropod cerithidea cingulata radiocarbon ages from the pre and post seismic sedimentary sequences constrain the paleoearthquake to 6500 7000 cal yrs bp we use micro and macrofossil data to determine the local paleoenvironment before and after the earthquake we estimate coseismic subsidence to be 0 45 0 30 m which is comparable to the 0 6 m of subsidence observed during the 2004 aceh andaman earthquake on aceh s west coast

global meltwater discharge and the deglacial sea level record from northwest scotland quantitative models of earth ice sheet ocean interactions predict that periods of rapid eustatic sea level rise indicating enhanced meltwater discharge to the oceans should be manifest in the relative sea level histories from sites within the limits of late devensian ice sheets analysis of a record of relative sea level change for the last 16000 calendar years from northwest scotland constrains the magnitude and timing of two major pulses of meltwater ca 14000 and ca 11300 cal yr bp inferred from coral records the ca 14000 cal yr bp event saw a temporary doubling of the flux of meltwater but existence of the second major event at ca 11300 cal yr bp is not supported by the data from northwest scotland copyright 1999 john wiley sons ltd

high rates of sea level rise during the last interglacial period sea level during the last interglacial stood at least 4 m higher than at present with evidence of short term fluctuations of up to 10 m a new continuous sea level record from the red sea and coral ages suggest that during these fluctuations sea level changes were on the order of 1 6 m per century

a data calibrated distribution of deglacial chronologies for the north american ice complex from glaciological modeling article i nfo past deglacial ice sheet reconstructions have generally relied upon discipline specific constraints with no at tention given to the determination of objective confidence intervals reconstructions based on geophysical inversion of relative sea level rsl data have the advantage of large sets of proxy data but lack ice mechanical constraints conversely reconstructions based on dynamical ice sheet models are glaciologically self consistent but depend on poorly constrained climate forcings and sub glacial processes as an example of a much better constrained methodology that computes explicit error bars we present a dis tribution of high resolution glaciologically self consistent deglacial histories for the north american ice com plex calibrated against a large set of rsl marine limit and geodetic data the history is derived from ensemble based analyses using the 3d mun glacial systems model and a high resolution ice margin chronol ogy derived from geological and geomorphological observations isostatic response is computed with the vm5a viscosity structure bayesian calibration of the model is carried out using markov chain monte carlo methods in combination with artificial neural networks trained to the model results the calibration provides a posterior distribution for model parameters and thereby modeled glacial histories given the observational data sets that takes data uncertainty into account final ensemble results also account for fits between com puted and observed strandlines and marine limits given the model including choice of calibration parameters input and constraint data sets and vm5a earth rhe ology we find the north american contribution to mwp1a was likely between 9 4 and 13 2 m eustatic over a 500 year interval this is more than half of the total 16 to 26 m meltwater pulse over 500 to 700 years with lower values being more probable indicated by the barbados coral record fairbanks 1989 peltier and fairbanks 2006 if one assumes a 5 meter living range for the acropora palmata coral 20 ka ice volume for north america was likely 70 1 2 0 m eustatic or about 60 of the total contribution to eustatic sea level change we suspect that the potentially most critical unquantified uncertainties in our analyses are those related to model structure especially climate forcing deglacial ice margin chronology and earth rheology

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

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

identifying coseismic subsidence in tidal wetland stratigraphic sequences at the cascadia subduction zone of western north america tidal wetland stratigraphy reveals that great plate boundary earthquakes have caused hundreds of kilometers of coast to subside at the cascadia subduction zone however determining earthquake recurrence intervals and mapping the coastal extent of past great earthquake ruptures in this region are complicated by the effects of many sedimentologic hydrographic and oceanographic processes that occur on the coasts of tectonically passive as well as active continental margins tidal wetland stratigraphy at many cascadia estuaries differs little from that at similar sites on passive margin coasts where stratigraphic sequences form through nonseismic processes unrelated to coseismic land level changes methods developed through study of similar stratigraphic sequences in europe provide a framework for investigating the cascadia estuarine record five kinds of criteria must be evaluated when inferring regional coastal subsidence due to great plate boundary earthquakes the suddenness and amount of submergence the lateral extent of submerged tidal wetland soils the coincidence of submergence with tsunami deposits and the degree of synchroneity of submergence events at widely spaced sites evaluation of such criteria at the cascadia subduction zone indicates regional coastal subsidence during at least two great earthquakes evidence for a coseismic origin remains equivocal however for the many peat mud contacts in cascadia stratigraphic sequences that lack 1 contrasts in lithology or fossils indicative of more than half a meter of submergence 2 well studied tsunami deposits or 3 precise ages needed for regional correlation paleoecologic studies of fossil assemblages are particularly important in estimating the size of sudden sea level changes recorded by abrupt peat mud contacts and in helping to distinguish erosional and gradually formed contacts from coseismic contacts reconstruction of a history of great earthquakes for the cascadia subduction zone will require rigorous application of the above criteria and many detailed investigations

middle and late holocene sea level changes in eastern maine reconstructed from foraminiferal saltmarsh stratigraphy and ams 14c dates on basal peat abstract a relative sea level history is reconstructed for machiasport maine spanning the past 6000 calendar years and combining two different methods the first method establishes the long term 10 3 yr trend of sea level rise by dating the base of the holocene saltmarsh peat overlying a pleistocene substrate the second method uses detailed analyses of the foraminiferal stratigraphy of two saltmarsh peat cores to quantify fluctuations superimposed on the long term trend the indicative meaning of the peat the height at which the peat was deposited relative to mean tide level is calculated by a transfer function based on vertical distributions of modern foraminiferal assemblages the chronology is determined from ams 14 c dates on saltmarsh plant fragments embedded in the peat the combination of the two different approaches produces a high resolution replicable sea level record which takes into account the autocompaction of the peat sequence long term mean rates of sea level rise corrected for changes in tidal range are 0 75 mm yr between 6000 and 1500 cal yr b p and 0 43 mm yr during the past 1500 years the foraminiferal stratigraphy reveals several low amplitude fluctuations during a relatively stable period between 1100 and 400 cal yr b p and a sea level rise of 0 5 m during the past 300 years

nineteenth and twentieth century sea level changes in tasmania and new zealand positive deviations from linear sea level trends represent important climate signals if they are persistent and geographically widespread this paper documents rapid sea level rise reconstructed from sedimentary records obtained from salt marshes in the southwest pacific region tasmania and new zealand a new late holocene relative sea level record from eastern tasmania was dated by ams14c conventional high precision and bomb spike 137cs 210pb stable pb isotopic ratios trace metals pollen and charcoal analyses palaeosea level positions were determined by foraminiferal analyses relative sea level in tasmania was within half a metre of present sea level for much of the last 6000 yr between 1900 and 1950 relative sea level rose at an average rate of 4 2 0 1 mm yr during the latter half of the 20th century the reconstructed rate of relative sea level rise was 0 7 0 6 mm yr our study is consistent with a similar pattern of relative sea level change recently reconstructed for southern new zealand the change in the rate of sea level rise in the sw pacific during the early 20th century was larger than in the north atlantic and could suggest that northern hemisphere land based ice was the most significant melt source for global sea level rise

barbados based estimate of ice volume at last glacial maximum affected by subducted plate coral records from the barbados have been used to infer that due to ice expansion sea level was 120 m lower than today during the last glacial maximum a 3d simulation of the mantle in this region suggests these estimates were biased by the presence of a subducted slab and indicates the sea level difference was closer to 130 m

deglacial meltwater pulse 1b and younger dryas sea levels revisited with boreholes at tahiti reconstructing sea level changes during the last deglaciation provides a way of understanding the ice dynamics that can perturb large continental ice sheets the resolution of the few sea level records covering the critical time interval between 14 000 and 9 000 calendar years before the present is still insufficient to draw conclusions about sea level changes associated with the younger dryas cold event and the meltwater pulse 1b mwp 1b we used the uranium thorium method to date shallow living corals from three new cores drilled onshore in the tahiti barrier reef no significant discontinuity can be detected in the sea level rise during the mwp 1b period the new tahiti sea level record shows that the sea level rise slowed down during the younger dryas before accelerating again during the holocene

late quaternary deglaciation and sea level history of eastern juan de fuca strait cascadia abstract eastern juan de fuca strait of southwestern british columbia northwestern washington state is near the western and southern terminus of late wisconsinan glaciation in north america seismic reflection profiles bathymetric data sediment core data and 41 new radiocarbon dates provide insight into the history of ice retreat and sea level change in the eastern portion of the strait the retreating ice margin appears to have passed through the area between 14 460 200 and 13 595 145 14c yr glacial marine sediments date between 12 889 50 and 11 110 50 14c yr bp wave eroded unconformities drowned prograded deposits and a partially isolated low stand basin are evidence attributed to low stand sea levels following deglaciation and five new control points on the local eustatic sea level curve are assigned based on radiocarbon dating of these features sea level change was rapid from 75 m immediately after deglaciation to possibly 60 4 m at 9920 60 14c yr bp after this time gradual sea level transgression took place relative sea level reached its approximate present position by 5470 115 14c yr bp since then relative sea level has remained constant suggesting eustatic rise is balanced by crustal uplift

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

great tsunamigenic earthquakes during the past 1000 yr on the alaska megathrust large to great earthquakes and related tsunamis generated on the alaska megathrust produce major hazards for both the area of rupture and heavily populated coastlines around much of the pacific ocean recent modeling studies suggest that single segment ruptures as well as multi segment 1964 type ruptures can produce great earthquakes m8 and significant hazards both in the near field and to distant locations through the generation of tsunamis we present new paleoseismological data from kodiak island and a new analysis of radiocarbon data based on bayesian age modeling to combine our observations with previous geological historical and archaeological investigations we suggest that in addition to multi segment ruptures in a d 1964 and 1020 1150 95 age estimate a single segment rupture occurred in 1788 with coseismic land surface deformation across kodiak island and a tsunami that is recorded in historical documents and in sediment sequences and another similar rupture of the same kodiak segment at a d 1440 1620 these indicate shorter intervals between ruptures of the kodiak segment than previously assumed and more frequent ruptures than for the prince william sound segment

timing and magnitude of the sea level jump preluding the 8200 yr event evidence from terrestrial glacial and global climate model reconstructions suggests that a sea level jump caused by meltwater release was associated with the triggering of the 8 2 ka cooling event however there has been no direct measurement of this jump using precise sea level data in addition the chronology of the meltwater pulse is based on marine data with limited dating accuracy the most plausible mechanism for triggering the cooling event is the sudden possibly multistaged drainage of the laurentide proglacial lakes agassiz and ojibway through the hudson strait into the north atlantic ca 8470 300 yr ago here we show with detailed sea level data from rotterdam netherlands that the sea level rise commenced 8450 44 yr ago our timing considerably narrows the existing age of this drainage event and provides support for the hypothesis of a double staged lake drainage the jump in sea level reached a local magnitude of 2 11 0 89 m within 200 yr in addition to the ongoing background relative sea level rise 1 95 0 74 m this magnitude observed at considerable distance from the release site points to a global averaged eustatic sea level jump that is double the size of previous estimates 3 0 1 2 m versus 0 4 1 4 m the discrepancy suggests either a coeval antarctic contribution or more likely a previous underestimate of the total american lake drainage

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

new data for the last glacial maximum in great britain and ireland abstract understanding the history of the british and irish ice sheet biis at the last glacial maximum lgm has been advanced by new approaches in particular by cosmogenic nuclide surface exposure dating aminostratigraphy of shelly glacial deposits ams radiocarbon dating and the evidence from continental margin marine cores all of which supersede the previously weak geochronologic control it was formerly believed that great britain and ireland was largely ice free between the last interglacial oxygen isotope sub stage 5e and the late devensian when the lgm occurred as such the biis was effectively out of phase with laurentide and scandinavian ice sheets as well as inferences of ice volume from oxygen isotope stratigraphy the biis during the late devensian maximum was also perceived as having been relatively stationary new evidence shows that the lgm was an important event during the evolution of an earlier biis when the extent of ice was greater repeated iceberg rafting events over the past 50 ka are shown by marine cores while the derivative inference of numerous corresponding glacial advances is supported by several clusters of 36 cl ages on glaciated surfaces and glacial boulders that are indicative of deglacial events between 40 and 12 ka these appear to be associated with heinrich events the earliest being inferred as heinrich 4 at about 40 ka during this advance the biis and scandinavian ice sheet sis were in contact and all of ireland was glaciated the ice sheet appears to have fluctuated several times between 40 and 25 ka although evidence for this is poorly preserved but the 36 cl and 14 c evidence is clear that the biis reached its lgm maximum size about 22 ka soon after heinrich event 2 when the biis and sis were not in contact one cluster of 36 cl and 14 c ages at 21 4 1 3 ka records an initial pulse of deglaciation that was followed by extensive deglaciation about 17 4 0 4 ka just before heinrich event 1 when the ice sheet readvanced contrary to previous views the biis probably existed throughout much of devensian time as a mobile and sensitive ice sheet during which the lgm advance was but one important event in places glacial deposits of the earlier devensian glaciation have previously been incorrectly identified as products of the later lgm glaciation

sea level change during the last 2500 years in new jersey usa relative sea level changes during the last w2500 years in new jersey usa were reconstructed to test if late holocene sea level was stable or included persistent and distinctive phases of variability foraminifera and bulk sediment d 13 c values were combined to reconstruct paleomarsh elevation with decimeter precision from sequences of salt marsh sediment at two sites using a multi proxy approach the additional paleoenvironmental information provided by bulk sediment d 13 c values reduced vertical uncertainty in the sea level reconstruction by about one third of that estimated from foraminifera alone using a transfer function the history of sediment deposition was constrained by a composite chronology an ageedepth model developed for each core enabled reconstruction of sea level with multi decadal resolution following correction for land level change 1 4 mm yr four successive and sustained multi centennial sea level trends were objectively identified and quantified 95 confidence interval using error in variables change point analysis to account for age and sea level uncertainties from at least 500 bc to 250 ad sea level fell at 0 11 mm yr the second period saw sea level rise at 0 62 mm yr from 250 ad to 733 ad between 733 ad and 1850 ad sea level fell at 0 12 mm yr the reconstructed rate of sea level rise since w1850 ad was 3 1 mm yr and represents the most rapid period of change for at least 2500 years this trend began between 1830 ad and 1873 ad since this change point reconstructed sea level rise is in agreement with regional tide gauge records and exceeds the global average estimate for the 20th century these positive and negative departures from background rates demonstrate that the late holocene sea level was not stable in new jersey

sea level in time and space revolutions and inconvenient truths in this paper we identify four revolutions that in our view have shaped the study of sea level changes in recent decades i the search for eustasy one of the most hotly debated issues in the 1960s is still relevant as models of glacial isostatic adjustment gia require input of the amount of meltwater transferred to the world s oceans following the demise of the large pleistocene ice sheets ii resolution of sea level archives all sea level archives have limitations in their resolving power but are we willing to define these from studies of salt marsh deposits and corals it is highly likely that climate driven metre scale sea level fluctuations have not occurred during the middle and late holocene iii rapid sea level changes improved coring technology has resulted in the suggestion of meltwater pulses during the last deglaciation low frequency high magnitude events have been documented along seismically active shorelines and provide information on seismic hazards and storm impacts iv merging of empirical sea level investigations and models much sea level research in the past two decades has embraced the integration of models and field derived data providing testable hypotheses and insights into processes we conclude with some reminders about the inconvenient truths that keep the sea level scientist honest

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

the age and origin of the younger dryas climate event in greenland ice cores 230th 234u and 14c dating of barbados corals has extended the calibration of 14c years b p to calendar years b p beyond the 9200 year tree ring series bard et al 1990 this now permits the conversion of 14c chronozones which delimit major climate shifts in western europe to calendar years the younger dryas chronozone defined as 11 000 to 10 000 14c years b p corresponds to 13 000 to 11 700 calendar years b p this calibration affects the interpretation of an intensely studied example of the younger dryas climate event the 18o anomaly between 1785 and 1793 m in dye 3 ice core the end of the 18o anomaly in dye 3 ice core has been dated by measurements of 14c in air bubbles andree et al 1984 1986 and by annual layer counting hammer et al 1986 the older 14c dates fall out of the range of the tree ring calibration series but can now be calibrated to calendar years using the barbados 230th 234u calibration the 14ccorrected age for the end of the 18o event is 10 300 400 calendar years b p compared to the annual layer counting age of 10 720 150 years b p thus the younger dryas event in the dye 3 ice core ends in the preboreal chronozone 11 700 to 10 000 calendar years b p and is not correlative with the end of the younger dryas event identified in pollen records marking european vegetation changes the end of the dye 3 18o event is however correlative with the end of meltwater pulse ib fairbanks 1989 marking a period of intense deglaciation with meltwater discharge rates exceeding 13 000 km yr

tsunami deposits beneath tidal marshes on vancouver island british columbia thin sheets of sand occur within holocene mud and peat deposits beneath tidal marshes at tofino ucluelet and port alberni on vancouver island british columbia the sand sheets are extensive and have sharp upper and lower contacts in most cases they consist of moderately sorted massive sand and silty sand with abundant wood and other plant detritus at port alberni the thickest sheet has gravel and is graded the upper two sand sheets in the tofino ucluelet area and possibly the third are also present at port alberni eyewitness accounts and 137 cs analysis suggest that the uppermost thinnest sand was deposited by the tsunami triggered by the great alaska earthquake in 1964 the next oldest sand sheet has been radiocarbon dated at our data suggest that large tsunamis have struck the southern british columbia coast several times during the late holocene and that some were much larger than the 1964 tsunami which caused about 10 million damage 1964 canadian dollars to communities on vancouver island because such tsunamis can be expected in the future they pose a hazard to people and property in some coastal areas

multi segment earthquakes and tsunami potential of the aleutian megathrust abstract large to great earthquakes and related tsunamis generated on the aleutian megathrust produce major hazards for both the area of rupture and heavily populated coastlines around much of the pacific ocean here we use paleoseismic records preserved in coastal sediments to investigate whether segment boundaries control the largest ruptures or whether in some seismic cycles segments combine to produce earthquakes greater than any observed since instrumented records began virtually the entire megathrust has ruptured since ad1900 with four different segments generating earthquakes m8 0 the largest was the m9 2 great alaska earthquake of march 1964 that ruptured 800 km of the eastern segment of the megathrust the tsunami generated caused fatalities in alaska and along the coast as far south as california east of the 1964 zone of deformation the yakutat microplate experienced two m8 0 earthquakes separated by a week in september 1899 for the first time we present evidence that earthquakes 900 and 1500 years ago simultaneously ruptured adjacent segments of the aleutian megathrust and the yakutat microplate with a combined area 15 greater than 1964 giving an earthquake of greater magnitude and increased tsunamigenic potential

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

gyre scale atmospheric pressure variations and their relation to 19th and 20th century sea level rise 1 most of the long tide gauge records in the north atlantic and north pacific commonly used to estimate global sea level rise and acceleration display a marked difference in behavior in the late 1800 s early 1900 s compared to the latter half of the 20th century the rates of sea level rise tend to be lower in the 19th compared to 20th century we show this behavior may be related to long term gyre scale surface pressure variations similar to those associated with the northern annular mode as sea level pressure increases decreases at decadal and longer timescales at the centers of the subtropical atmospheric gyres sea level trends along the eastern margins in each ocean basin decrease increase this is not an isostatic response the scaling between local surface pressure and sea level at interannual and longer timescales is 3 to 6 times greater than expected by that mechanism rather it appears to be the result of large possibly gyre scale changes in ocean circulation some evidence is also presented indicating slow 2 cm sec westward propagation of sea level changes in the atlantic from the west coast of europe to the east coast of the u s which produce the decadal variability seen there

late holocene vertical land motion and relative sea level changes lessons from the british isles vertical land motion caused by continuing glacial isostatic adjustment is one of several important components of sea level change and is not limited just to previously glaciated regions a national scale analysis for the british isles shows an ellipse of present day relative uplift relative sea level fall 1 2 mm a 1 broadly centred on the deglaciated mountains of scotland the pattern of three foci of relative subsidence 1 mm a 1 results from the additional interactions of the deglacial meltwater load on the atlantic basin and the continental shelf and the signal due to far field ice sheets at a local scale sediment compaction can more than double the rate of relative land subsidence relative land level change the negative of relative sea level change is not the same as vertical land motion there is a spatial pattern in the difference between relative land level change and vertical land motion with differences at present of approximately 0 1 to 0 3 mm a 1 around the british isles and 2 5 to 1 5 mm a 1 globally for the wider scientific and user community whether or not the differences are considered significant will depend upon the location time frame and spatial scale of the study that uses such information copyright 2011 john wiley sons ltd

sea level changes in iceland and the influence of the north atlantic oscillation during the last half millennium abstract we present a new diatom based sea level reconstruction for iceland spanning the last 500 years and investigate the possible mechanisms driving the sea level changes a sea level reconstruction from near the icelandic low pressure system is important as it can improve understanding of ocean atmosphere forcing on north atlantic sea level variability over multi decadal to centennial timescales our reconstruction is from vi arholmi salt marsh in snaefellsnes in western iceland a site from where we previously obtained a 2000 yr record based upon less precise sea level indicators salt marsh foraminifera the 20th century part of our record is corroborated by tide gauge data from reykjavik overall the new reconstruction shows ca 0 6 m rise of relative sea level during the last four centuries of which ca 0 2 m occurred during the 20th century low amplitude and high frequency sea level variability is super imposed on the pre industrial long term rising trend of 0 65 m per 1000 years most of the relative sea level rise occurred in three distinct periods ad 1620 1650 ad 1780 1850 and ad 1950 2000 with maximum rates of 3 2 mm yr during the latter two of these periods maximum rates were achieved at the end of large shifts from negative to positive of the winter north atlantic oscillation nao index as reconstructed from proxy data instrumental data demonstrate that a strong and sustained positive nao a deep icelandic low generates setup on the west coast of iceland resulting in rising sea levels there is no strong evidence that the periods of rapid sea level rise were caused by ocean mass changes glacial isostatic adjustment or regional steric change we suggest that wind forcing plays an important role in causing regional scale coastal sea level variability in the north atlantic not only on multi annual timescales but also on multi decadal to centennial timescales

holocene sea level database for the atlantic coast of the united states we have constructed a database of holocene relative sea level rsl observations for the atlantic coast of the united states the database contains 492 index points which locate the position of rsl in time and space and 344 limiting dates which constrain the minimum or maximum limit of former sea level the majority of the index points in the database are from 6 ka bp to present with only 7 older than 6 ka bp spatially index points are distributed between maine and south carolina but there is an absence of data from georgia and the atlantic coast of florida the database is sub divided into 16 regions based on the distance from the former laurentide ice sheet and are classified depending upon their susceptibility to compaction the index points and limiting data demonstrate that rsl did not exceed present 0 m during the holocene except potentially in regions 1 and 2 eastern maine and southern maine rates of rsl change were highest during the early holocene and have decreased over time due to the diminishing response of the earth s mantle to glacial isostatic adjustment and reduction of ice equivalent meltwater input along the atlantic coast of the united states the linear rate of rsl rise prior to 4 ka bp ranged from 0 5 to 4 5 mm a 1 compared to 0 6 1 8 mm a 1 from 4 ka bp to ad 1900 the database suggests minimal 0 3 mm yr changes in these rates of rsl rise during the late holocene deglaciation of the laurentide ice sheet caused the spatial variability captured by the database the maximum rate of late holocene and ongoing rsl rise occurred in mid atlantic regions new jersey and inner delaware because of collapse of the peripheral forebulge

links between early holocene ice sheet decay sea level rise and abrupt climate change the beginning of the holocene interglacial was marked by ice sheet melting and sea level rise a review of sea level and climate records identifies two sea level jumps associated with the final drainage of glacial lake agassiz and links them to an abrupt cooling event

increasing australian indonesian monsoon rainfall linked to early holocene sea level rise the australian indonesian summer monsoon affects rainfall variability across the indo pacific region reconstructions of monsoon strength from stalagmites show that precipitation increased from 11 000 to 7 000 years ago as rising global sea level caused the flooding of the indonesian continental shelf the australian indonesian summer monsoon affects rainfall variability and hence terrestrial productivity in the densely populated tropical indo pacific region it has been proposed that the main control of summer monsoon precipitation on millennial timescales is local insolation1 2 3 but unravelling the mechanisms that have influenced monsoon variability and teleconnections has proven difficult owing to the lack of high resolution records of past monsoon behaviour here we present a precisely dated reconstruction of monsoon rainfall over the past 12 000 years based on oxygen isotope measurements from two stalagmites collected in southeast indonesia we show that the summer monsoon precipitation increased during the younger dryas cooling event when atlantic meridional overturning circulation was relatively weak4 monsoon precipitation intensified even more rapidly from 11 000 to 7 000 years ago when the indonesian continental shelf was flooded by global sea level rise5 6 7 we suggest that the intensification during the younger dryas cooling was caused by enhanced winter monsoon outflow from asia and a related southward migration of the intertropical convergence zone8 however the early holocene intensification of monsoon precipitation was driven by sea level rise which increased the supply of moisture to the indonesian archipelago

tsunamigenic sea floor deformations in addition to the primary damage they do earthquakes can cause tsunamis massive ocean swells that can inundate coastal regions in their perspective synolakis et al describe results presented at a workshop on the interface between seismology and tsunami hydrodynamics held in santa monica in may 1997 the authors discuss the highlights of the meeting and summarize future directions for research

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

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

glacial rebound and sea level change an example of a relationship between mantle and surface processes lambeck k 1993 glacial rebound and sea level change an example of a relationship between mantle and surface processes in r wortel u hansen and r sabadini editors relationships between mantle processes and geological processes at or near the earth s surface tectonophysics 223 15 37 the problem of glacial rebound provides an outstanding example of the relationship between surface and mantle processes on time scales of 103 to 105 years changes in surface loading of ice and melt water associated with the growth and decay of the great ice sheets deform the surface of the planet and induces flow in the mantle a measure of the earth s response to the changing surface loads and internal deformation is provided by observations of past sea levels relative to the present level and inversion of these observations provides constraints on both the models of the rheological response of the earth to loading and on models of the ice sheets constraints on ice sheet models include the total volume of the grounded ice at the time of maximum glaciation the global rates of melting of the ice sheets the thickness of the ice at maximum glaciation the extent of ice cover over shallow seas such as the north sea and the barents sea and the role of antarctica in the global ice balance constraints on mantle parameters include the effective lithospheric thickness and the effective viscosity of the mantle some recent results for both sets of parameters are discussed

late quaternary sea level change and isostatic and tectonic land movements along the belgian dutch north sea coast geological data and model results early and middle holocene sea level data from belgium plot ca 2 m above data from the western netherlands reflecting differential tectonic and isostatic movements the total uplift rate of belgium relative to the western netherlands decays gradually from 0 66 m kyr 1 at 7500 cal yr bp to less than 0 25 m kyr 1 since 5000 cal yr bp the tectonic component of this relative movement inferred from eemian sea level data is in the order of 0 06 to 0 16 m kyr 1 the isostatic component of the uplift is related to the last phase of the collapse of a peripheral bulge under the netherlands and the dutch and german sectors of the north sea and to hydroisostatic subsidence of the north sea basin caused by water loading as sea level rose comparisons with isostatic rebound models show that they predict well the holocene isostatic movement between belgium and the western netherlands and that the predictions are improved when the tectonic component is removed from the observations preliminary evaluation of sea level data from the dutch sector of the north sea shows that glacio hydroisostatic subsidence relative to belgium was significantly greater than for the western netherlands coastal area and spatially highly variable copyright 2002 john wiley sons ltd