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We report on the distribution of contemporary foraminifera in salt marshes in Mission Bay and Carpinteria Slough, Southern California. Combining these data with existing datasets from Seal Beach and Tijuana, we explore the potential for a regional training set to underpin quantitative reconstructions of paleoenvironmental change from foraminifera preserved in salt-marsh sediments. We demonstrate that species’ distributions are highly dependent on elevation, suggesting fossil foraminiferal assemblages here, as in many other regions, are useful depositional elevation indicators. Transfer functions provide predictions from Mission Bay cores with decimeter-scale uncertainties. Nevertheless, interpretation of marsh-surface elevation change is complicated by a complex geomorphic setting and anthropogenic impacts. An abrupt change in elevation in the mid-1700s may be related to lateral spreading of water-saturated sediments during an earthquake on the Rose Canyon fault, suggesting the potential for foraminifera to support new palaeoseismic and sea-level records for the region.

Saltmarshes play a key role in sequestering and storing carbon, as well as providing a wide range of other ecosystem services. Assessments of both total carbon stocks and rates of carbon accumulation are vital for quantifying saltmarsh contributions to climate-change mitigation and for guiding efforts to protect and restore coastal wetlands. Current assessments of the rates at which UK saltmarshes accumulate carbon are based on a small and spatially limited dataset. To address this knowledge gap, we estimate sedimentation rates and assess organic carbon density from 22 saltmarshes distributed around the UK. Bayesian modelling quantifies the relationship between depth and age from 210Pb and 137Cs activity data. We combine these sedimentation rates with centimetre-resolution organic carbon density measurements to quantify carbon accumulation rates through time. By upscaling these estimates to the total UK saltmarsh area and fully quantifying uncertainties, we conclude that UK saltmarsh carbon burial rates are lower than previously thought.

Detailed sea-level budgets are now available for the 20th and 21st centuries, but separating the differing contributions of sea-level rise prior to 1900 remains difficult, in part due to additional temporal and vertical uncertainties associated with proxy records, and the spatially variable nature of driving processes.We present tide gauge and proxy reconstructions of sea level since 1700, and analyse their structure using Gaussian process modelling which allows for continuous reconstructions with fully quantified uncertainties. This enables the timing of accelerations, magnitude and rates of change to be determined, and in turn enables site-specific sea-level budgets to be derived. The contribution of different driving mechanisms (e.g., glacio-isostatic adjustment and sterodynamic changes) for each site is assessed, and the evolution of the barystatic contribution for the last 300 years is evaluated.

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We test whether vegetation community composition from a 10-year climate manipulation experiment on a Welsh peat bog resembles vegetation communities during periods of climate change inferred from a peat core. Experimentally warmed and combined warmed and droughted treatments drove significant increases in ericaceous shrubs but Sphagnum was unaffected. Similarly, Calluna vulgaris seeds increase during inferred warmer periods in the palaeoecological record. Experimental short-term episodic drought (four 4-week drought treatments) did not affect vegetation. Plant community composition has undergone several abrupt changes throughout the past c. 1500 years, often in response to human disturbance. Only slight changes occurred during the Medieval Climate Anomaly (c. 950-1250 Common Era [CE]) in vegetation and hydrology, while abrupt changes occurred during the Little Ice Age (c. 1300-1850 CE) when water tables were highest, suggesting that these shifts were driven by changes in water table, modulated by climate. A period of water table drawdown c. 1800, synchronous with historical records of increased drainage, corresponds with the development of the present-day vegetation community. Modern analogues for fossil material, characterized by abundant Rhynchospora alba and Sphagnum pulchrum, are more common after this event. Vegetation changes due to climate inferred from the palaeo record differ from those observed in the experiments, possibly relating to differences in the importance of drivers of vegetation change over varying timescales. Whereas temperature is frequently identified as the dominant driver of plant community change in experiments, sustained changes in water table appear to be more important in the long-term record. We find evidence that recent climate change and other anthropogenic stressors (e.g. drainage, heavy metal and nitrogen pollution) may promote the development of novel plant communities without analogues in the fossil record. These communities may be poorer at sequestering carbon and may respond differently to future climate change.Rydym yn aprofi os mae cyfansoddiad cymuned planhigion mewn arbrawf trin hinsawdd o 10 mlynedd ar gors mawn yn Gymru yn debyg i gymunedau oedd yn bodoli yn ystod cyfnodau o newid yn yr hinsawdd, e.e., yr Anomaledd Hinsawdd Canoloesol (AHC - c. 950-1250 CE), a nodwydd o graidd mawn. Fe wnaeth triniaethau arbrofol o cynhesu a cynhesu yn cyfunol efo sychder gyrru cynyddu sylweddol mewn phrysgwydd ericaceous. Doedd na ddim effaith ar digonedd Sphagnum. Yn yr un modd, nath hadau Erica tetralix a Calluna vulgaris cynyddu yn ystod cyfnodau cynhesach a gasglwyd yn y cofnod palaeoecolegol. Ni wnaeth sychder episodig tymor byr arbrofol (pedair triniaeth sychder o 4 wythnos) effeithio cymuned planhigion. Mae cyfansoddiad cymuned planhigion wedi profi sawl newid sydyn trwy gydol y gorffennol c. 1500 flynyddoedd, yn aml mewn ymateb i aflonyddwch dynol. Dim ond newidiadau bach a ddigwyddodd yn ystod yr AHC ar gyfer planhigion a hydroleg, tra digwyddodd newidiadau sydyn yn ystod yr Oes Iâ Fach (tua 1300-1850 CE) pan oedd y trwythiadau dŵr ar eu uchaf, sydd yn awgrymu bod y newidiadau hyn yn cael eu gyrru gan newidiadau yn y lefel trwythiad, wedi'u modiwleiddio gan yr hinsawdd. O gwmpas c.1800 mae yna cyfnod o dynnu i lawr trwythiad dwr, sy'n gydamserol â chofnodion hanesyddol o ddraeniad cynyddol, yn cyfateb i ddatblygiad y gymuned planhygion heddiw. Mae analogau modern ar gyfer deunydd ffosil, a nodweddir gan Rhyncospora alba a Sphagnum pulchrum, yn fwy cyffredin ar ôl y digwyddiad hwn. Mae newidiadau llystyfiant oherwydd hinsawdd a gwelodd yn yr cofnod palaeo yn wahanol i'r rhai a arsylwyd yn yr arbrofion, o bosibl yn ymwneud â gwahaniaethau ym mhwysigrwydd gyrwyr newid llystyfiant dros amserlenni amrywiol. Tra bod tymheredd yn aml yn cael ei nodi fel prif ysgogydd newid cymunedol planhigion mewn arbrofion, mae'n ymddangos bod newidiadau parhaus yn y lefel trwythiad yn bwysicach yn y tymor hir. Mae yna tystiolaeth y gallai newid yn yr hinsawdd yn ddiweddar, efo phwysleisiau anthropogenig eraill (e.e. draenio, llygredd metel trwm a nitrogen) hyrwyddo datblygiad cymunedau planhigion newydd heb analogau yn y cofnod ffosil. Efallai bod y cymunedau hyn yn dlotach wrth atafaelu carbon a gallant ymateb yn wahanol i newid yn yr hinsawdd yn y dyfodol.

The late-Quaternary relative sea-level (RSL) history of Ireland is complex, positioned at the margins of the former British-Irish Ice Sheet, and subject to the influence of ice unloading and forebulge collapse. Geophysical models of post-glacial isostatic adjustment (GIA) provide estimates of the pattern of RSL change since deglaciation which may be tested and validated with empirical data from proxy records. For the region of northwest Ireland, there is a paucity of high-quality RSL data and, therefore, equivocal evidence to support the GIA models that predict a mid to Late-Holocene RSL highstand of between +0.5 and +2 m above present. This study aims to investigate this model-data discrepancy by reconstructing RSL change from a near continuous salt-marsh sequence at Bracky Bridge, Donegal, spanning the last ca. 2500 years. We develop a transfer function model to reconstruct the vertical position of sea level using a regional diatom training set to quantify the indicative meaning and predict the palaeomarsh elevation of the core samples. A chronology is provided by a combination of 14C and 210Pb data, with sample specific ages derived from an age-depth model using a Bayesian framework. Our reconstruction shows ca. 2 m of relative sea-level rise in the past 2500 years. This is not compatible with some previously published sea-level index points from the region, which we re-interpret as freshwater/terrestrial limiting data. These results do not provide any evidence to support a Mid-Holocene RSL highstand above present sea level. Whilst none of the available GIA models replicate the timing and magnitude of the Late-Holocene RSL rise in our reconstruction, those which incorporate a thick and extensive British-Irish Sea Ice Sheet provide the best fit.

Coasts in tectonically active regions face varying threat levels as land subsides or uplifts relative to rising sea levels. We review the processes influencing relative sea-level change in New Zealand, and the geological context behind ongoing land movements, focussing on major population centres. Whilst Holocene sea levels have been reconstructed using a variety of techniques, recent work uses salt-marsh microfossil assemblages to reconstruct relative sea-level changes over the past few centuries. For the twentieth century, these proxy-based studies often show enhanced rates of sea-level rise relative to tide-gauge observations. The effects of tectonic subsidence must be considered, alongside vertical and dating uncertainties in the sea-level reconstructions. Global Positioning Systems (GPS) observations for the past few decades show that vertical land movement (VLM) may be influencing rates of relative sea-level rise. However, the short period of GPS observations, during which trends and rates have varied at some localities, raises questions over the longer-term contribution of VLM to sea-level change over the past few centuries and for future projections. We argue that high-resolution palaeo-sea-level reconstructions from salt-marsh sedimentary sequences can help to answer these questions regarding the interplay between sea-level change and VLM at key locations.

Regional datasets of the vertical distribution of intertidal foraminifera are useful to reconstruct Holocene sea-level changes from fossil foraminifera in estuaries and salt marshes. In this paper, we present a new foraminiferal dataset from the Ythan Estuary (Scotland) and combine it with data from eight other coastal sites from England, Denmark and Germany to produce a regional modern training set for the North Sea. We recognise a correlation between foraminifera and tidal elevation which makes the foraminifera suitable as sea-level indicators. We subdivide the data into subregional training sets and develop WA and WAPLS transfer functions. Applying a variety of statistical methods, including detrended canonical analysis, cross-validation by bootstrapping and leave-one-site-out, and the modern analogue technique, we establish the most appropriate transfer function from which to reconstruct early Holocene sea-level changes in a sediment core from the western North Sea coast. Results show that the subregional England/Scotland training set provides the most appropriate sea-level reconstructions, with decimetre-scale uncertainties. The techniques we use in this study, that consider both the modern and fossil assemblages to determine the best training set and transfer function, are suggested as a template for the development of regional transfer functions based on foraminifera and other intertidal microfossils.

Accurate Holocene relative sea-level curves are vital for modelling future sea-level changes, particularly in regions where relative sea-level changes are dominated by isostatically induced vertical land movements. In North Wales, various glacial isostatic adjustment (GIA) models predict a mid-Holocene relative sea-level highstand between 4 and 6 ka, which is unsubstantiated by any geological sea-level data but affects the ability of geophysical models to model accurately past and future sea levels. Here, we use a newly developed foraminifera-based sea-level transfer function to produce a 3300-year-long late-Holocene relative sea-level reconstruction from a salt marsh in the Malltraeth estuary on the south Anglesey coast in North Wales. This is the longest continuous late-Holocene relative sea-level reconstruction in Northwest Europe. We combine this record with two new late-Holocene sea-level index points (SLIPs) obtained from a freshwater marsh at Rhoscolyn, Anglesey, and with previously published regional SLIPs, to produce a relative sea-level record for North Wales that spans from ca. 13,000 BP to the present. This record leaves no room for a mid-Holocene relative sea-level highstand in the region. We conclude that GIA models that include a mid-Holocene sea-level highstand for North Wales need revision before they are used in the modelling of past and future relative sea-level changes around the British Isles.

Although the Netherlands has a long tradition of sea-level research, no Holocene relative sea-level curve is available for the north of the country. Previous studies hypothesized that the relative sea-level reconstruction for the western Netherlands is also valid for the northern part of the country. However, glacial isostatic adjustment (GIA) models predict a lower and steeper relative sea-level curve because of greater postglacial isostatic subsidence. Long-term data of relative sea-level change are important to inform GIA models and understand postglacial vertical land motion related to the rebound of Fennoscandia and neotectonic activity. We compiled and evaluated a set of basal peat radiocarbon dates to reconstruct the Holocene relative mean sea-level rise in the Dutch Wadden Sea area. For the early Holocene, this reconstruction is lower than the western Netherlands curve. After 6400 cal a BP, the curve for the Wadden Sea is statistically indistinguishable from that for the western Netherlands, a result that conflicts with GIA model results. It remains to be investigated whether the problem lies with the GIA model predictions or with the quality of the available data. Additional basal peat radiocarbon dates from suitable sites should be collected to further resolve this problem.

Accurate reconstruction of Lateglacial and Holocene relative sea-level (RSL) histories is complicated where mismatches exist between geological data and RSL curves generated by models of glacio-isostatic adjustment (GIA). In Ireland, such discrepancies have profound implications for interpreting the glacial history of the British Isles and for the use of glacial rebound models to predict future sea-level changes. To address this issue we present new RSL data from four sites along the western coast of Ireland, including 17 data points from the critical period before 5000 14C a BP for which very few data are available. We generate new RSL simulations from an existing GIA model, incorporating a thickened Irish Ice sheet component. Simulated curves from Co. Mayo and Co. Donegal accommodate the higher than present Lateglacial RSL inferred from glaciomarine muds while still meeting the requirement for below present RSL indicated by the new terrestrial limiting data points. Relaxation of trimline constraints on maximum ice sheet thickness provides considerable scope for improved GIA performance. These results demonstrate inferences about RSL drawn from GIA modelling and glacio-sedimentary data are not mutually exclusive, and represent a significant step towards resolving a long-standing debate between the field-based and modelling communities.

Salt-marsh foraminifera are frequently used around the world as proxies in paleoenvironmental studies of sea-level change. Quantitative reconstructions of sea-level change use transfer functions which are based on the vertical zonation of salt-marsh foraminifera with respect to the tidal frame. This paper explores for the first time the environmental factors that control the foraminiferal assemblages in Southern California marshes using modern surface samples (1 cm thick) from two marshes Seal Beach and Tijuana Estuary. The dead foraminiferal assemblages demonstrate distinct zonation across the salt-marsh surfaces which is primarily related to elevation. Other variables less important than elevation such as O2, temperature, salinity and pH additionally control the distribution pattern of these assemblages. The tidal flat and low marshes are characterized by high abundances of Miliammina fusca and calcareous species. The middle marsh is dominated by Jadammina macrescens and Trochammina inflata, while the high marsh zone is dominated by Trochamminita irregularis, Miliammina petila, J. macrescens and T. inflata. Regression modelling was used for the development of a sea-level transfer function based on a combined training set of surface samples from the two study sites. The performance of the Weighted Average – Partial Least Squares (WA-PLS) transfer function suggests a robust relationship between the observed and estimated elevations (r2Jack = 0.72), and is capable of predicting former sea levels to a precision of ± 0.09 m. Our results can be used for future paleoenvironmental reconstructions along the Southern California coast, an area that has experienced changes in sea level in the past and will be affected by future sea-level rise coupled with climate and anthropogenic changes, resulting in wide impacts on the natural coastal habitats in this region.

Salt-marsh sediments are routinely used to reconstruct sea-level changes over past millennia. These reconstructions bridge an important gap between geological and instrumental sea-level records, and provide insights into the role of atmospheric, oceanic, climatic and anthropogenic sea-level drivers, thereby improving understanding of contemporary and future sea-level changes. Salt-marsh foraminifera, diatoms and testate amoebae are three of the proxies capable of accurately reconstructing former sea level over decadal to millennial timescales. Datasets of surface assemblages are collated along elevational gradients to provide modern analogues that can be used to infer former marsh-surface elevations from fossil assemblages. Testate amoebae are the most recently developed proxy and existing studies suggest that they are at least as precise as the two other proxies. This study provides a synthesis of sea-level research using testate amoebae and collates and analyses existing surface datasets of intertidal salt-marsh testate amoebae from sites throughout the North Atlantic. We test the hypothesis that intertidal testate amoebae demonstrate cosmopolitan intertidal zonation across wide geographical areas in a way that is unique to this proxy. Testate amoebae assemblages are harmonised under a unified taxonomy and standardised into a single basin-wide training set suitable for reconstructing sea-level changes from salt-marsh sediments across the North Atlantic. Transfer functions are developed using regression modelling and show comparable performance values to published local training sets of foraminifera, diatoms and testate amoebae. When used to develop recent (last 100 years) sea-level reconstructions for sites in Norway and Quebec, Canada, the testate amoebae-based transfer function demonstrated prediction uncertainties of ± 0.26 m and ± 0.10 m respectively. These uncertainties equate to 10% and 11% of the tidal ranges at each site, which is of comparable precision to other published sea-level reconstructions based on foraminifera or diatoms. There is great scope for further developing intertidal testate amoebae as precise sea-level indicators and their application should be tested at sites beyond the North Atlantic.

Supplemental material, Supplement_1_WA_Reconstruction for Testing the mid-Holocene relative sea-level highstand hypothesis in North Wales, UK by Greg T Rushby, Geoff T Richards, W Roland Gehrels, William P Anderson, Mark D Bateman and William H Blake in The Holocene

Proxy records of past sea-level change provide a means of extending sea-level histories from tide gauges into the pre-industrial period. This is especially valuable in the South Atlantic region where sea-level data are limited to only a few tide-gauge records. Multi-proxy approaches to sea-level reconstruction are relatively rare but have distinct benefits when groups of micro-organisms are sparse or under-represented in modern or fossil sediments. Here, we address this challenge by utilising surface foraminifera, testate amoebae and diatoms from a salt marsh at Swan Inlet, East Falkland. All three micro-organism groups occupied distinct vertical niches in the contemporary salt-marsh. We investigated the relative performance of each group of micro-organisms in providing a sea-level reconstruction using individual (group-specific) regression models and with a multi-proxy regression model that combined all three groups. Foraminifera alone were not a suitable proxy. Surveyed sample elevations were closely matched by estimated elevations using Weighted-Average (WA) and Weighted-Average Partial-Least-Squares (WA- PLS) regressions. Relative sea-level reconstructions were derived by applying each model to microfossil assemblages recovered from a core (SI-2) from the same site. The combined transfer function yielded reconstructive precision (± 0.08 m) comparable to our best single-proxy transfer function (± 0.06 m) but only 18% of palaeo-samples were identified as having “close” or “good” analogues in the combined training data set. We highlight the benefit of a pragmatic approach to sea-level reconstructions whereby additional proxies should be employed if the use of only one proxy performs poorly across the width of the elevation gradient.

The most significant climate cooling of the Holocene is centred on 8.2 kyr BP (the ‘8.2 event’). Its cause is widely attributed to an abrupt slowdown of the Atlantic Meridional Overturning Circulation (AMOC) associated with the sudden drainage of Laurentide proglacial Lakes Agassiz and Ojibway, but model simulations have difficulty reproducing the event with a single-pulse scenario of freshwater input. Several lines of evidence point to multiple episodes of freshwater release from the decaying Laurentide Ice Sheet (LIS) between ∼8900 and ∼8200 cal yr BP, yet the precise number, timing and magnitude of these events – critical constraints for AMOC simulations – are far from resolved. Here we present a high-resolution relative sea level (RSL) record for the period 8800 to 7800 cal yr BP developed from estuarine and salt-marsh deposits in SW Scotland. We find that RSL rose abruptly in three steps by 0.35 m, 0.7 m and 0.4 m (mean) at 8760–8640, 8595–8465, 8323–8218 cal yr BP respectively. The timing of these RSL steps correlate closely with short-lived events expressed in North Atlantic proxy climate and oceanographic records, providing evidence of at least three distinct episodes of enhanced meltwater discharge from the decaying LIS prior to the 8.2 event. Our observations can be used to test the fidelity of both climate and ice-sheet models in simulating abrupt change during the early Holocene.

Traditional methods of investment appraisal have been criticized in the context of climate change adaptation. Economic assessment of adaptation options needs to explicitly incorporate the uncertainty of future climate conditions and should recognise that uncertainties may diminish over time as a result of improved understanding and learning. Real options analysis (ROA) is an appraisal tool developed to incorporate concepts of flexibility and learning that relies on probabilistic data to characterise uncertainties. It is also a relatively resource-intensive decision support tool. We test whether, and to what extent, learning can result from the use of successive generations of real life climate scenarios, and how non-probabilistic uncertainties can be handled through adapting the principles of ROA in coastal economic adaptation decisions. Using a relatively simple form of ROA on a vulnerable piece of coastal rail infrastructure in the United Kingdom, and two successive UK climate assessments, we estimate the values associated with utilising up-dated information on sea-level rise. The value of learning can be compared to the capital cost of adaptation investment, and may be used to illustrate the potential scale of the value of learning in coastal protection, and other adaptation contexts.

Small islands tend to experience exacerbated environmental/social vulnerabilities, due to isolation, size and a small resource base. The response of social communities to environmental stress can be addressed by compiling palaeoecological proxies for land management alongside archaeological records. This paper presents pollen data from four new late Holocene sequences that lie around sea-level on the Isles of Scilly (south-west England), to understand the impact of coastal change on island communities. Interpretation of sequences near the coastal zone can be confounded by problems in disentangling human impact from maritime and wetland influence. Multivariate analysis is used to separate samples influenced by maritime conditions and wetland development from 'inland' human land management practices. During the Bronze Age clearance of woodland resulted in an intensively managed pastoral system and archaeological datasets indicate that maritime resources formed an important part of the subsistence economy. Despite coastal change that resulted in loss of land area and reduced the extent of the intertidal zone, the pollen data and evidence from existing archaeological data show continuity through later prehistory and into the medieval period. The archaeological data and pollen evidence point towards a highly resilient community that employed a mixed and varied subsistence base. Copyright (c) 2015 John Wiley & Sons, Ltd.

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.

Relative sea-level data from the pre-industrial era are required for validating geophysical models of glacio-isostatic adjustment as well as for testing models used to make sea-level predictions based on future climate change scenarios. We present the first late Holocene (past ∼3300 years) relative sea-level reconstruction for northwestern Norway based on investigations in South Hinnoya in the Vesteralen – Lofoton archipelago. Sea-level changes are reconstructed from analyses of salt-marsh and estuarine sediments and the micro-organisms (foraminifera and testate amoebae) preserved within. The ‘indicative meaning’ of the microfauna is established from their modern distributions. Records are dated by radiocarbon, 201Pb, 137Cs and chemostratigraphical analyses. Our results show a continuous relative sea-level decline of 0.7–0.9 mm yr−1 for South Hinnoya during the late Holocene. The reconstruction extends the relative sea-level trend recorded by local tide gauge data which is only available for the past ∼25 years. Our reconstruction demonstrates that existing models of shoreline elevations and GIA overpredict sea-level positions during the late Holocene. We suggest that models might be adjusted in order to reconcile modelled and reconstructed sea-level changes and ultimately improve understanding of GIA in Fennoscandia.

This paper presents a novel method to reconstruct sea-level change in coastal freshwater back-barrier marshes. Freshwater environments have long been considered to be unsuitable for the reconstruction of Holocene sea level changes as they provide limiting, rather than precise, sea-level index points. We recorded the stratigraphy of a small beach and back-barrier coastal Phragmites (reed) marsh at Hallsands, south Devon, southwest England, using hand-drilled cores and ground-penetrating radar, and collected five new sea-level index points from the base of a Holocene peat sequence to refine the regional Holocene relative sea-level curve. We demonstrate that the samples, despite their freshwater origin, yield accurate sea-level index points as determined from the quantifiable relationship between tide levels and groundwater. By means of water-table monitoring and groundwater modelling we show that the primary controls on the water table in the marsh are: (1) stratigraphy; (2)peat permeability; and (3) recharge rates in the back-barrier marsh. The five index points document relative sea-level positions between 7200 and 2400 cal yr BP. Three points are in good agreement with previously collected regional data from inter-tidal deposits and two points usefully fill gaps in the existing reconstruction. An amended Holocene relative sea-level curve for south Devon, based on 30 data points, is presented. We conclude that the combined approach of data collection and modelling used in this paper can be applied to similar coastal settings around the world and allows the collection of sea-level index points from locations not previously thought suitable for this purpose.

Understanding late Holocene to present relative sea-level changes at centennial or sub-centennial scales requires geological records that dovetail with the instrumental era. Salt marsh sediments are one of the most reliable geological tide gauges. In this paper we review the methodological and technical advances that promoted research on ‘high resolution’ late Holocene sea-level change. We work through an example to demonstrate different pathways to quantitative reconstructions of relative sea level based on salt marsh sediments. We demonstrate that any reconstruction is in part a result of the environment from which the record is taken, the modern dataset used to calibrate the fossil changes, statistical assumptions behind calibrating microfossil assemblages and choices made by the researchers. With the error term of typical transfer function models ~ 10–15% of the tidal range, micro-tidal environments should produce the most precise sea-level reconstructions. Sampled elevation range of the modern dataset also has a strong influence on model predictive ability. Model-specific errors may under represent total uncertainty which comes from field practices, sedimentary environment, palaeo-tidal changes and sediment compaction as well as statistical uncertainties. Geological tide gauges require a detailed chronology but we must be certain that apparent relative sea-level fluctuations are not simply a consequence of an age–depth model. We make six suggestions to aid the development and interpretation of geological tide gauge records.

A high-resolution pollen and micro-charcoal (>5 μm) record has been produced from a short sediment (50 cm) core recovered from a salt marsh in the Little Swanport Estuary, eastern Tasmania. This record suggests that there are four phases associated with the European settlement of the region. An initial phase from around 1830 to 1858 AD, which is similar to the previous Aboriginal period; a relatively low impact transitional phase from 1859 to 1898 AD; a rapid and marked deforestation period from 1899 to 1932 AD; and establishment of the contemporary landscape, with reforestation occurring, but with marked differences in species composition (i.e., greater representation of exotic taxa and altered understorey composition) from 1933 to 2006 AD. Key similarities are seen across Australia with the European settlement phase (i.e., addition of exotic taxa, deforestation and/or changes in vegetation composition, alterations in fire regimes and increased sedimentation rates), but high-resolution analysis suggests that these impacts may manifest in different ways depending on the local environmental setting and/or historical context of the settlement location. Furthermore, Amaranthaceae pollen representation appears to be impacted by changes in sea level. However, other factors such as human modifications, particularly grazing, and climate variability may play additional roles and further research is required to disentangle the relative effects of these factors.

Future climate change is likely to increase the frequency of coastal storms and floods, with major consequences for coastal transport infrastructure. This paper assesses the extent to which projected sea-level rise is likely to impact upon the functioning of the Dawlish to Teignmouth stretch of the London to Penzance railway line, in England. Using a semi-empirical modelling approach, we identify a relationship between sea-level change and rail incidents over the last 150years and then use model-based sea-level predictions to extrapolate this relationship into the future. We find that days with line restrictions (DLRs) look set to increase by up to 1170%, to as many as 84–120 per year, by 2100 in a high sea-level rise scenario (0.55–0.81m). Increased costs to the railway industry deriving from maintenance and line restrictions will be small (£ millions) in comparison with damage caused by individual extreme events (£10s of millions), while the costs of diversion of the railway are higher still (£100s of millions to billions). Socio-economic costs to the region are likely to be significant although they are more difficult to estimate accurately. Finally, we explain how our methodology is applicable to vulnerable coastal transport infrastructure worldwide.

Sea-level and ice-sheet databases have driven numerous advances in understanding the Earth system. We describe the challenges and offer best strategies that can be adopted to build self-consistent and standardised databases of geological and geochemical information used to archive palaeo-sea-levels and palaeo-ice-sheets. There are three phases in the development of a database: (i) measurement, (ii) interpretation, and (iii) database creation. Measurement should include the objective description of the position and age of a sample, description of associated geological features, and quantification of uncertainties. Interpretation of the sample may have a subjective component, but it should always include uncertainties and alternative or contrasting interpretations, with any exclusion of existing interpretations requiring a full justification. During the creation of a database, an approach based on accessibility, transparency, trust, availability, continuity, completeness, and communication of content (ATTAC3) must be adopted. It is essential to consider the community that creates and benefits from a database. We conclude that funding agencies should not only consider the creation of original data in specific research-question-oriented projects, but also include the possibility of using part of the funding for IT-related and database creation tasks, which are essential to guarantee accessibility and maintenance of the collected data.

We assess the relationship between temperature and global sea-level (GSL) variability over the Common Era through a statistical metaanalysis of proxy relative sea-level reconstructions and tide-gauge data. GSL rose at 0.1 ± 0.1 mm/y (2σ) over 0-700 CE. A GSL fall of 0.2 ± 0.2 mm/y over 1000-1400 CE is associated with ∼ 0.2 °C global mean cooling. A significant GSL acceleration began in the 19th century and yielded a 20th century rise that is extremely likely (probability [Formula: see text]) faster than during any of the previous 27 centuries. A semiempirical model calibrated against the GSL reconstruction indicates that, in the absence of anthropogenic climate change, it is extremely likely ([Formula: see text]) that 20th century GSL would have risen by less than 51% of the observed [Formula: see text] cm. The new semiempirical model largely reconciles previous differences between semiempirical 21st century GSL projections and the process model-based projections summarized in the Intergovernmental Panel on Climate Change's Fifth Assessment Report.

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 AMS(14)C (conventional, high precision and bomb-spike), Cs-137, Pb-210, 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. (C) 2011 Elsevier B.V. All rights reserved.

Pollen, molluscs and foraminifera are used to reconstruct Holocene environmental changes in the Palude Frattarolo–Lago Salso area (Tavoliere Plain, Apulia, Italy) near the Coppa Nevigata archaeological site. This settlement, inhabited from the Early Neolithic to the Iron Age, was situated on the edge of a broad lagoon that extended for some 40 km along the eastern margin of the Tavoliere Plain. The paleoenvironmental history was investigated using an 8.6 m deep core drilled in the ancient lagoon. The records show a shoaling-upwards sequence characterised by a semi-closed lagoonal environment that gradually became isolated from the sea and ultimately transformed into a terrestrial environment. The semi-closed lagoon was in existence between 6340 and 4880 cal. yr BP and contained a brackish environment with a moderate input of sea water, undergoing frequent changes in size and salinity. The vegetational landscape at this time was dominated by mixed oak forests. Between 4880 and 3230 cal. yr BP the semi-closed lagoon turned into a closed waterbody. The surrounding landscape opened around 4000 cal. yr BP, similar to many other sites in the central Mediterranean region. A hiatus in deposition occurred between 3230 and somewhat before 180 cal. yr BP, when a freshwater environment prevailed and the area was an open and dry grassland. Our multiproxy approach shows that during the last few thousand years large natural habitats of northern Apulia were progressively reduced in size. In spite of an ancient human occupation, a mainly natural cause for the evolution of the lagoon appears most likely.

Holocene relative sea-level data contain information on vertical land movements along coasts and, hence, can provide vital input for predictions of future sea-level change. At Thurlestone, in southwest England, late Holocene coastal sediments were cored and sampled in coastal back-barrier marshes. The presence of a basal sedimentary unit containing salt-marsh microfossils made it possible to obtain precise estimates of late Holocene relative sea-level change from the sediments. This is important because previous studies have suggested that the southwest of England is experiencing the fastest rates of land subsidence in the British Isles. Ten new late Holocene basal sea-level index points fill an important gap in the palaeosea-level data set for southwest England. Another 15 early and middle Holocene sea-level index points are available from previous work. The data show that relative sea level rose by about 10 m between 9000 and 7000 cal. yr BP and a further 8 m in the last 7000 yr. In the last 2000 yr, relative sea level rose on average by 0.9 mm/yr. The coast is currently subsiding by 1.1 mm/yr due to ongoing glacial isostatic adjustment (GIA). The Bradley et al. (2009) GIA model, which is used in the United Kingdom to determine land-motion rates for input into future sea-level predictions, underestimates the rate of coastal subsidence by about 0.16 mm/yr, but performs better than other models. Our data validate the land-motion rates currently used in regional sea-level projections.

Following the Last Glacial Maximum (25,000–20,000 years ago), sea level rose at rates on the order of several tens of millimeters per year at times, and increased overall by over 130 m. However, melting of the great ice sheets was largely complete by 6,000 years ago, and it is believed that sea level did not rise significantly again until recently. The rates of sea level change during the last few centuries and in recent decades can be measured in units of millimeters per year and are particularly important in understanding present-day climate change. We now have a range of techniques with which sea level changes can be measured and thus studied more intensively than before, as a global average and in each region. This article introduces each of the main data sets and presents the primary research findings. It is hoped that a greater understanding of the reasons for past observed sea level change, discussed elsewhere in this issue, will lead to better estimation of the changes likely to occur in the future.

This paper aims to establish whether contemporary salt-marsh foraminifera from eastern Tasmania are suitably related to elevation and can therefore be used to reconstruct past sea levels. A proxy reconstruction of recent sea-level change in Tasmania is potentially useful because in New Zealand a prominent early 20th century acceleration of sea-level rise has been documented which requires regional confirmation. Forty-three surface samples were collected from two salt marshes in the Little Swanport Estuary. Common species are: Trochammina inflata, Jadammina macrescens, Miliammina fusca, Trochamminita irregularis and Trochamminita salsa. The latter two species have been previously grouped together as T. salsa, but are distinguished here because they occupy distinct vertical niches. We performed regression analyses on the agglutinated foraminifera and their surface elevations using the software package C2 and tested the accuracy of various regression models by comparing predicted heights of the two transects with surveyed heights. We found that the surveyed heights are closely matched by elevations predicted by Weighted-Average Partial-Least-Squares (WA-PLS) models. These models predict sea level to within ± 0.10 m. PLS models showed favourable statistical parameters but were unreliable when used for predictions. Applications of PLS regression models in sea-level reconstructions therefore require caution. We compare our results with other studies from around the world and conclude that microtidal coastlines provide the most advantageous conditions for precise sea-level reconstructions.

Two of the most important topics in Sea Level Science are addressed in this paper. One is concerned with the evidence for the apparent acceleration in the rate of global sea level change between the nineteenth and twentieth centuries and, thereby, with the question of whether the twentieth century sea level rise was a consequence of an accelerated climate change of anthropogenic origin. An acceleration is indeed observed in both tide gauge and saltmarsh data at different locations around the world, yielding quadratic coefficients ‘c’ of order 0.005 mm/year2, and with the most rapid changes of rate of sea level rise occurring around the end of the nineteenth century. The second topic refers to whether there is evidence that extreme sea levels have increased in recent decades at rates significantly different from those in mean levels. Recent results, which suggest that at most locations rates of change of extreme and mean sea levels are comparable, are presented. In addition, a short review is given of recent work on extreme sea levels by other authors. This body of work, which is focused primarily on Europe and the Mediterranean, also tends to support mean and extreme sea levels changing at similar rates at most locations.

Surface sediments were sampled from the salt marshes of the Morbihan Gulf (Brittany, France), the Barbadun, Plentzia and Urdaibai estuaries (Basque Country, northern Spain), the Minho and Lima estuaries (northern Portugal) and the Sado estuary (southern Portugal), to study the vertical distribution of foraminifera and their potential use for sea-level studies along the Atlantic coasts of SW Europe. The most abundant species found in the marshes are Jadammina macrescens and Trochammina inflata , with Miliammina fusca and Arenoparrella mexicana as secondary species, but there are some important regional differences in the composition of the foraminiferal assemblages. In the Basque marshes, Haynesina germanica and Ammonia tepida are dominant species, whereas in northern Portugal the most abundant species are M. fusca , Haplophragmoides spp. and T. inflata together with J. macrescens . Local transfer functions for sea-level reconstruction were constructed from fossil foraminiferal assemblages using Partial-Least-Squares (PLS) regression for data sets with a linear distribution (Morbihan and Sado) and Weighted-Averaging-Partial-Least-Squares (WA-PLS) regression for data sets with unimodal foraminiferal distributions (Basque and Minho-Lima). The most accurate models were obtained from high marsh assemblages. The transfer function models provided errors of ca. ±0.10 m, indicating that precise reconstructions of former sea levels are possible in this area.

Four decades of palaeosea-level research in the British Isles have produced a large dataset of age–altitude curves of postglacial sea-level changes. Patterns of late Holocene relative sea-level change reveal the persistent influence of the British/Irish Ice Sheet and the larger Scandinavian Ice Sheet on contemporary rates of vertical land movements. The Shennan and Horton (2002) map of late Holocene relative land movements has been used in future sea-level rise predictions by the United Kingdom Climate Impact Programme in their 2002 assessment (UKCIP02), but has been mistaken for a map of absolute land movements. In this paper, land-motion data for Britain are extracted from the Shennan and Horton (2002) relative sea-level data, and a new map of crustal land movements is presented which also includes Ireland. This procedure takes into account the regional 20th century sea-level rise (∼0.14 m) and the process of ocean syphoning (i.e. a global fall in sea level of ∼0.3 mm/yr due to GIA induced ocean-floor lowering and re-distribution of ocean mass). The calculated land-motion rates also depend on the global late Holocene ice-equivalent sea-level change, given by the Intergovernmental Panel on Climate Change as 0.0–0.2 mm/yr. Accounting for these processes reduces the misfit between geological observations of vertical land motion and those independently derived from gravity-aligned Global Positioning System (AG GPS) measurements and shows that UKCIP02 has underestimated land subsidence in southern Britain and over-estimated land uplift in Scotland, both by 0.1–0.2 mm/yr. A best fit between GPS and geological estimates of land movements in Britain is achieved for a global long-term eustatic sea-level fall of ca 0.2 mm/yr, suggesting some global ice expansion in the late Holocene, rather than melt. If this is correct, uplift rates in Scotland would be lower and subsidence rates in southern Britain would be faster (by 0.4–0.5 mm/yr) than estimated by UKCIP02. More high-quality late Holocene relative sea-level data are required to quantify vertical land motion as accurately as possible, especially near large coastal population centres, for input into regional scenarios of future sea-level rise.

Proxy-based sea-level reconstructions place the instrumentally observed rates of recent sea-level rise in a longer term context by providing data that extend the instrumental sea-level record into past centuries. This paper presents the first sea-level reconstructions based on analyses of testate amoebae, to test their ability to produce high-precision reconstructions of past sea level. We present two reconstructions for the past 100"yr from sites in Maine (USA) and Nova Scotia (Canada) based on short cores from salt marshes, and modern training data from North America and the United Kingdom. These are compared with tide-gauge records and reconstructions based on foraminifera from the same cores. The reconstructions show good agreement with both the tide-gauge data and the foraminifera-based reconstructions. The UK data perform well in predicting known elevations of North American surface samples and produce sea-level reconstructions very similar to those based on the North American data, suggesting the methodology is robust across large geographical areas. We conclude that testate amoebae have the potential to provide robust, higher precision sea-level reconstructions for the past few centuries if modern transfer functions are improved and core sites are located within the main zone of testate amoebae occurrence on the salt marsh.

We provide records of relative sea level since A.D. 1500 from two salt marshes in North Carolina to complement existing tide-gauge records and to determine when recent rates of accelerated sea-level rise commenced. Reconstructions were developed using foraminifera-based transfer functions and composite chronologies, which were validated against regional twentieth century tide-gauge records. The measured rate of relative sea-level rise in North Carolina during the twentieth century was 3.0–3.3 mm/a, consisting of a background rate of ~1 mm/a, plus an abrupt increase of 2.2 mm/a, which began between A.D. 1879 and 1915. This acceleration is broadly synchronous with other studies from the Atlantic coast. The magnitude of the acceleration at both sites is larger than at sites farther north along the U.S. and Canadian Atlantic coast and may be indicative of a latitudinal trend.

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. This tenfold increase in the rate of rise can be attributed to climate change through the melting of land ice and the thermal expansion of ocean water. As the present warming trend is expected to continue, global mean sea level will continue to rise. Here we review recent insights into past sea-level changes on decadal to millennial timescales and how they may help constrain future changes. We find that most studies constrain global mean sea-level rise to less than one metre over the twenty-first century, but departures from this global mean could reach several decimetres in many areas. We conclude that improving estimates of the spatial variability in future sea-level change is an important research target in coming years

We report a record of atmospheric Pb deposition at a coastal site in western Iceland that spans the last two millennia. The elemental concentrations of Pb, Al, Li and Ti are determined using ICP-MS from a sediment monolith collected from a salt marsh. Multicollector (MC) ICP-MS analysis is used to obtain isotopic ratios of stable Pb. The Pb/Ti and Pb/Li ratios are used to separate natural Pb background concentrations from Pb derived from remote anthropogenic sources. The pollution record in western Iceland is subdued in comparison with Pb records from the European mainland, but the isotopic character, profile and timing of Pb deposition show good agreement with the atmospheric Pb fall-out reported from sites in Scandinavia and northwestern Europe. At the bottom of the sequence we isolate a low-level (0.1-0.4 mg kg(-1)) Pb enrichment signal dated to AD 50-150. The isotopic signature and timing of this signal suggest Roman metal working industries as the source. In the subsequent millennium there was no significant or very low (i.e. elemental concentrations0.01 mg kg(-1)) anthropogenic Pb deposition at the site up to, and including, the early Medieval period. Above a pumice layer, dated to AD 1226-1227, a small increase in Pb deposition is found. This trend is maintained until a more substantive and progressive increase is signalled during the late 1700s and early 1800s. This is followed by a substantial enrichment signal in the sediments (3.0 mg kg(-1)) that is interpreted as derived from industrial coal burning and metal working during the 19th and 20th centuries in northern Europe. During the late 20th century, significant fall-out from European fuel additives reached Iceland.

Previous sea-level studies suggest that southwest Britain has the fastest subsiding coastline in the United Kingdom, but tide-gauge data, GPS and gravity measurements and geophysical models show little evidence of anomalous subsidence in this region. In this paper we present 15 new sea-level index points from four coastal barrier systems in south Devon. Eight are from compaction-free basal sediments and others were corrected for autocompaction. Our data suggest that relative sea level along the south Devon coastline has risen by 21 ± 4 m during the past 9000 years. Sea-level rise slowed during the middle and late Holocene and a rise of 8 ± 1 m has occurred since ca. 7000 cal. yr BP. Anomalous ages for many rejected points are attributed to sediment reworking during barrier transgression. The relative sea-level history during the early and middle Holocene shows a good fit with geophysical model predictions, but the geological and modelled data diverge in the later Holocene. Unlike the geophysical models, sea-level index points cannot differentiate between late Holocene relative sea-level histories of south Devon and southwest Cornwall. It is suggested that this discrepancy can be resolved by obtaining additional high-quality sea-level index points covering the past 4000 years. Copyright © 2008 John Wiley & Sons, Ltd.