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The warmest peak of the Last Interglacial (ca. 128–116 ka) is considered a process analogue, and is often studied to better understand the effects of a future warmer climate on the Earth's system. In particular, significant effort has been made to better constrain ice sheet contributions to peak Last Interglacial sea level through field observation of paleo relative sea level indicators. Along tropical coastal margins, these observations are predominantly based on fossil shallow coral reef sequences, also thanks to the possibility of gathering reliable U-series chronological constraints. However, the preservation of many Pleistocene reef sequences is often limited to a series of discrete relative sea-level positions within the interglacial, where corals suitable for dating were preserved. This in turn, limits our ability to understand the continuous evolution of paleo relative sea-level through an entire interglacial, also affecting the possibility to unravel the existence and pattern of sub-stadial sea level oscillations. While the interpretation of lithostratigraphic and geomorphologic properties is often used to overcome this hurdle, geological interpretation may present issues related to subjectivity when dealing with missing facies or incomplete sequences. In this study, we try to step back from a conventional approach generating a spectrum of synthetic Quaternary subtropical fringing reefs for a site in southwestern Madagascar (Indian Ocean). We use the DIONISOS forward (Beicip Franlab) stratigraphic model to build a fossil reef at this location. In each model run, we use distinct Greenland and Antarctica Ice Sheet melt scenarios produced by a coupled ANICE-SELEN glacial isostatic adjustment model. The resulting synthetic reef sequences are then used test these melt scenarios against the stratigraphic record. We propose that this sort of stratigraphic modelling may provide further quantitative control when interpreting Last Interglacial reef sequences.

A 70 km laterally extending tidal notch was carved during the Last Interglacial (127-116 ka BP) along the East-Sardinian coast, Orosei Gulf, with a maximum height of 9.1 m. We present the results of the detailed mapping of the Orosei tidal notch using the Structure from Motion Multi-View Stereo (SfM-MVS) reconstruction method. Although its geometry is laterally constant, the notch depth differs due to local factors. Results of SfM-MVS reconstructions, together with local parameters, were used as input in a geometric model that simulates the notch shape based on randomly sampled relative sea-level curves. The modeled profiles best matching the real shape of the notch are those characterized by a bimodal geometry. Extracting information from this rocky imprint is considered crucial to better understand past changes in sea level, which are in turn significant to better gauge sea-level variations in warmer climate conditions., https://app.dimensions.ai/details/grant/grant.7819993

Since the Pleistocene, the Mediterranean is a hot spot for climate change and human migrations, thus offering the opportunity to investigate how human populations have responded to environmental changes and sea level variations. This is the main topic of the SPHeritage Project (MUR grant: FIRS2019_00040, P.I.: M. Pappalardo) that proposes an interdisciplinary approach to investigate the human-environment interaction (in particular sea level variations) over the last 400,000 years using a combination of micro-invasive methods. The Project is re-investigating the well-known archaeological area of ​​the Balzi Rossi (Ventimiglia, at the border between Italy and France), which represents a unique assemblage of archaeological sites dating to the Palaeolithic, distributed in a geomorphological setting rich of markers of past sea level changes. As most of the local archaeological sequences have been extensively investigated at the beginning of the last century and large part of the deposits removed, we will combine the analyses of materials preserved in museums (including strips of sediments) and the remnants still preserved inside many rockshelters and caves of the archaeological complex. Moreover, our geomorphological survey identified new sedimentary sequences preserving information on relative sea level changes. This approach will permit to obtain innovative data submitting small samples to state-of-the-art methods for dating and palaeoenvironmental reconstruction, thus offering the opportunity to better constrain the time and steps of climate change, sea level oscillations, and human settlements. Moreover, data will converge into geoheritage analyses aimed at finding the best practices for promoting and protecting the site. Here, we present an overview of the project and preliminary results from some of the major archaeological sites.

International audience; In the context of industrial-era global change, Mediterranean coastal areas are threatened by relative sea level (RSL) rise. Shifts in the drivers of coastal dynamics are forecasted to trigger changes in the frequency of flooding of low-lying areas, with significant effects on marine-coastal environments, societies, economy and urban systems. Here, we probe coastal floods in the eastern part of the Gulf of Venice (coastal Croatia) to understand the drivers of saltwater intrusions. We reconstructed RSL rise in the north-eastern Adriatic during the Holocene based on 43 RSL index points and analyzed the evolution of coastal submersions on the Istrian Peninsula for the last 5200 years based on inputs of marine components and increases in supratidal scrubs. We produced pollen-based climate reconstructions to analyze the potential effects of air temperature and precipitation changes on submersions. We investigated the response of precipitation and temperature to mid-late Holocene summer/winter insolation forcing and insolation-induced changes in sea surface temperatures (SSTs). We found that during periods of warmer SST, coastal flooding increased markedly. This process seems to have been initiated by warmer atmospheric temperatures that led to increases in summer evaporation, counterbalancing the effects of heavy precipitation during winter. As a result, freshwater flows into coastal areas were reduced and resulted in recurrent inputs of saltwater inland. Our study suggests that present-day climate drivers (increases in SSTs and air temperatures, and decreases in precipitation) will probably favour frequent coastal flooding, a process that will be amplified by RSL rise.

Sea-level rise is predicted to cause major damage to tropical coastlines. While coral reefs can act as natural barriers for ocean waves, their protection hinges on the ability of scleractinian corals to produce enough calcium carbonate (CaCO3 ) to keep up with rising sea levels. As a consequence of intensifying disturbances, coral communities are changing rapidly, potentially reducing community-level CaCO3 production. By combining colony-level physiology and long-term monitoring data, we show that reefs recovering from major disturbances can produce 40% more CaCO3 than currently estimated due to the disproportionate contribution of juvenile corals. However, the buffering effect of highly productive juvenile corals is compromised by recruitment failures, which have been more frequently observed after large-scale, repeated bleaching events. While the size structure of corals can bolster a critical ecological function on reefs, climate change impacts on recruitment may undermine this buffering effect, thus further compromising the persistence of reefs and their provision of important ecosystem services.

In this paper, we describe a sea-level database compiled using published last interglacial, Marine Isotopic Stage 5 (MIS 5), geological sea-level proxies within East Africa and the Western Indian Ocean (EAWIO). Encompassing vast tropical coastlines and coralline islands, this region has many occurrences of well-preserved last interglacial stratigraphies. Most notably, islands almost entirely composed of Pleistocene reefs (such as Aldabra, the Seychelles) have provided reliable paleo relative sea-level indicators and well-preserved samples for U-series chronology. Other sea-level proxies include uplifted marine terraces in the north of Somalia and Pleistocene eolian deposits notched by the MIS 5 sea level in Mozambique to tidal notches in luminescence-limited eolian deposits in Mozambique. Our database has been compiled using the World Atlas of Last Interglacial Shorelines (WALIS) interface and contains 58 sea-level indicators and 2 terrestrial-limiting data points. The open-access database is available at https://doi.org/10.5281/zenodo.4302244 (Version 1.03; Boyden et al., 2020).

Reconstructing the topography of shallow underwater environments using Structure-from-Motion – Multi View Stereo (SfM-MVS) techniques applied to aerial imagery from Unmanned Aerial Vehicles (UAVs) is a challenging problem, as it involves non-linear distortions caused by water refraction. This study presents an experiment with aerial photographs collected with a consumer-grade UAV on the shallow-water reef of Fuvahmulah, the Maldives. Under conditions of rising tide, we surveyed the same portion of the reef in ten successive flights. For each flight, we used SfM-MVS to reconstruct the Digital Elevation Model (DEM) of the reef, and used the flight at low tide (where the reef is almost entirely dry) to compare the performance of DEM reconstruction under higher water levels. Our results show that differences with the reference DEM increase with increasing depth, but are substantially larger if no underwater ground control points are taken into account in the processing. Correcting our imagery with algorithms that account for refraction did not improve the overall accuracy of reconstruction. We conclude that reconstructing shallow-water reefs (less than 1 m depth) with consumer-grade SfM-MVSs and SfM-MVS is possible, but its precision is limited and strongly correlated with water depth. The best results are achieved when ground control points were placed both above and underwater and no refraction correction is used in our processing.

Sea-level rise represents a severe hazard for populations living within low-elevation coastal zones and is already largely affecting coastal communities worldwide. As sea level continues to rise following unabated greenhouse gas emissions, the exposure of coastal communities to inundation and erosion will increase exponentially. These impacts will be further magnified under extreme storm conditions. In this paper, we focus on one of the most valuable coastal real estate markets globally (Palm Beach, FL). We use XBeach, an open-source hydro and morphodynamic model, to assess the impact of a major tropical cyclone (Hurricane Matthew, 2016) under three different sea-level scenarios. The first scenario (modern sea level) serves as a baseline against which other model runs are evaluated. The other two runs use different 2100 sea-level projections, localized to the study site: (i) IPCC RCP 8.5 (0.83 m by 2100) and (ii) same as (i), but including enhanced Antarctic ice loss (1.62 m by 2100). Our results show that the effective doubling of future sea level under heightened Antarctic ice loss amplifies flow velocity and wave height, leading to a 46% increase in eroded beach volume and the overtopping of coastal protection structures. This further exacerbates the vulnerability of coastal properties on the island, leading to significant increases in parcel inundation.

The evolution of past global ice sheets is highly uncertain. One example is the missing ice problem during the Last Glacial Maximum (LGM, 26 000-19 000 years before present) – an apparent 8-28 m discrepancy between far-field sea level indicators and modelled sea level from ice sheet reconstructions. In the absence of ice sheet reconstructions, researchers often use marine δ18O proxy records to infer ice volume prior to the LGM. We present a global ice sheet reconstruction for the past 80 000 years, called PaleoMIST 1.0, constructed independently of far-field sea level and δ18O proxy records. Our reconstruction is compatible with LGM far-field sea-level records without requiring extra ice volume, thus solving the missing ice problem. However, for Marine Isotope Stage 3 (57 000-29 000 years before present) - a pre-LGM period - our reconstruction does not match proxy-based sea level reconstructions, indicating the relationship between marine δ18O and sea level may be more complex than assumed., The configuration of past ice sheets, and therefore sea level, is highly uncertain. Here, the authors provide a global reconstruction of ice sheets for the past 80,000 years that allows to test proxy based sea level reconstructions and helps to reconcile disagreements with sea level changes inferred from models.

We produced a new suite of sea-level data which allowed assessing the Holocene evolution of the Bonifacio Strait, a key coastal sector of the Mediterranean Sea which experienced significant morphological changes since the Last Glacial Maximum. Squeezed between Corsica and Sardinia islands, this strait connects the two major basins of the western Mediterranean. Due to its peculiar geographic and morphological setting, the Bonifacio Strait is affected by extreme meteomarine conditions characterized by severe winds, waves, and currents. The millennial sea-level changes were reconstructed through multiproxy investigations made of sediment coring and underwater beachrock sampling carried out on both sides of the strait. These data provided fresh insights into the timing of the progressive opening of the Bonifacio Strait which followed the Last Glacial Maximum when Corsica and Sardinia were connected forming the largest Mediterranean island. Major palaeogeographic changes occurred before ~7 ka BP. Since that period, the significant decrease of the northern ice-sheet melting triggered a significant sea-level stabilization which induced only minor modifications in the palaeogeography of the strait. In the late Holocene, the isostatic-related subsidence became the dominant factor controlling the sea-level changes which rose with rates ≤0.35 mm a−1 in the last four millennia. Our data have also an important archaeological implication because they indicate that the Bonifacio Strait has not represented a significant geographical barrier along the early Neolithic migration path which connected mainland Italy to northern Corsica and finally to Sardinia. This further confirms the ability of early Neolithic communities to navigate not also across large sea stretches but also maritime areas characterized by extremely complex meteomarine conditions.

Several studies have highlighted the difficulties inherent to the use of bimodal fluvial sediments in beach nourishment and the resulting unpredictable behaviour of the beach profile. In this paper, we monitored the temporal evolution of a nourishment project carried out on a northwestern Mediterranean beach and using fluvial mixed sand and gravel nourishment material. The main aim of the study was to examine the morpho-sedimentary evolution of the beach from the injection of the nourishment material to the attainment of a targeted equilibrium profile. The monitoring activity was conducted coupling multiple topo-bathymetric surveys and sediment sampling. The data show that the targeted equilibrium profile was attained less than 2 years after the nourishment, and, since that period, the shoreline has shown minimal mobility. Our results show that the positioning of the nourishment material is as important as the correct choice of grain size to attain rapid and successful nourishment of a beach. Further applications of this methodology in other coastal settings and/or with different nourishment sediments (e.g. medium or fine sands) are presently being considered. If confirmed at a broader scale, this nourishment design, employing bimodal fluvial sediments, should significantly contribute to the mitigation of beach erosion.

We assembled a database of Holocene relative sea-level index points (n = 213) and marine (n = 211) and terrestrial (n = 122) limiting points for the broader South and Southeast Asian region including the Maldives, India and Sri Lanka. The standardized review of published age-elevation information from corals, deltaic, estuarine and mangrove deposits, beachrocks and tidal notches, yielded a new suite of relative sea-level index and limiting points produced according to a standardized protocol. Expected spatial variability in Holocene relative sea-level change due to glacial isostatic adjustment was accounted for, by first subdividing the study area into ten geographic sub-regions from the Central Indian Ocean to the Western Tropical Pacific, and second by comparing sub-regional relative sea-level data to model predictions of glacial isostatic adjustment. Results show that some of the regionally constrained relative sea-level data are characterized by significant inconsistencies that cannot be explained by glacial isostatic adjustment. Such inconsistencies of standardized relative sea-level data become particularly obvious in areas around the Red River Delta in Vietnam, the Gulf of Thailand, the northwest coast of Malaysia and the Spermonde Archipelago in Indonesia. Based on a critical evaluation of the reviewed relative sea-level indicators, we discuss possible sources of local divergence and identify regions where data are currently insufficient to constrain glacial isostatic adjustment predictions. The remaining quality-controlled and consistent relative sea-level data show that glacial isostatic adjustment and syn-/post-formational influences such as tectonic uplift, subsidence and compaction were the dominant local drivers of Holocene relative sea-level change. Collectively, the results of this review suggest that Holocene sea levels in South and Southeast Asia and surrounding regions have been controlled by a variety of global and local drivers and imply that additional index points from the Java Sea in Indonesia would be valuable to better assess the spatial variability, and to calibrate geophysical models of glacial isostatic adjustment. Published version

International audience; Over the past 3.5 million years, there have been several intervals when climate conditions were warmer than during the pre-industrial Holocene. Although past intervals of warming were forced differently than future anthropogenic change, such periods can provide insights into potential future climate impacts and ecosystem feedbacks, especially over centennial-to-millennial timescales that are often not covered by climate model simulations. Our observation-based synthesis of the understanding of past intervals with temperatures within the range of projected future warming suggests that there is a low risk of runaway greenhouse gas feedbacks for global warming of no more than 2 °C. However, substantial regional environmental impacts can occur. A global average warming of 1–2 °C with strong polar amplification has, in the past, been accompanied by significant shifts in climate zones and the spatial distribution of land and ocean ecosystems. Sustained warming at this level has also led to substantial reductions of the Greenland and Antarctic ice sheets, with sea-level increases of at least several metres on millennial timescales. Comparison of palaeo observations with climate model results suggests that, due to the lack of certain feedback processes, model-based climate projections may underestimate long-term warming in response to future radiative forcing by as much as a factor of two, and thus may also underestimate centennial-to-millennial-scale sea-level rise.

International audience; A recent suite of Relative Sea-Level (RSL) data for the past 12 ka BP has provided new insights into the sea-level histories of the western Mediterranean region. Our analysis of the chronostratigraphic context of sea-level indicators from Spain (Catalonia, the Balearic Islands and the Gulf of Valencia), France (Corsica Island) and Italy (Sardinia Island) has yielded 162 new sea-level index and limiting points. These data have considerably enhanced previous RSL compilations, in addition to improving the quality of spatio-temporal sea-level reconstructions and our capacity to estimate isostatic-related vertical motions in the western Mediterranean basin. The glacial and hydro-isostatic adjustment (GIA) pattern elucidated by the new database shows discrepancy with respect to those predicted by the available GIA models. In particular, the new results underscore a non-coherent isostatic response of the central portion of the western Mediterranean, with the Balearic Islands manifesting significant departures from the sea-level histories of Corsica, Sardinia and, more generally, along most of the western Mediterranean coast. Our results are a crucial contribution to defining both the pattern and the magnitude of the isostatic signal along the western Mediterranean coast. In fact, vertical isostatic motions represent a key to better assess any possible post-industrial acceleration in sea-level rise and to define future scenarios of coastal inundation in the context of global change.

Sea-level changes have shaped the world's carbonate platform margins and continental shelves, leaving typical geomorphic imprints, such as drowned reef terraces. In this paper, we present the results of 112 scuba diving transects across seven different Maldivian atolls and one multibeam survey around Male Island, the capital of Maldives. We report on the occurrence of drowned reef terraces down to 120 m depth. In total, we identified six levels of submerged terraces that we consider as indicative of periods of time with stable or slowly rising sea level that can be attributed either to deceleration of the last deglacial sea-level rise or to Late Quaternary sea-level highstands. We compare our dataset to the depth of reef terraces reported globally, and we discuss the reasons why common global submerged terrace levels are difficult to identify in the field record.

International audience; Very high resolution (VHR) airborne data enable detection and physical measurements of individual coral reef colonies. The bathymetric LiDAR system, as an active remote sensing technique, accurately computes the coral reef ecosystem’s surface and reflectance using a single green wavelength at the decimetre scale over 1-to-100 km2 areas. A passive multispectral camera mounted on an airborne drone can build a blue-green-red (BGR) orthorectified mosaic at the centimetre scale over 0.01-to-0.1 km2 areas. A combination of these technologies is used for the first time here to map coral reef ecological state at the submeter scale. Airborne drone BGR values (0.03 m pixel size) serve to calibrate airborne bathymetric LiDAR surface and intensity data (0.5 m pixel size). A classification of five ecological states is then mapped through an artificial neural network (ANN). The classification was developed over a small area (0.01 km2) in the lagoon of Moorea Island (French Polynesia) at VHR (0.5 m pixel size) and then extended to the whole lagoon (46.83 km2). The ANN was first calibrated with 275 samples to determine the class of coral state through LiDAR-based predictors; then, the classification was validated through 135 samples, reaching a satisfactory performance (overall accuracy = 0.75).

As global climate warms and sea level rises, coastal areas will be subject to more frequent extreme flooding and hurricanes. Geologic evidence for extreme coastal storms during past warm periods has the potential to provide fundamental insights into their future intensity. Recent studies argue that during the Last Interglacial (MIS 5e, ∼128–116 ka) tropical and extratropical North Atlantic cyclones may have been more intense than at present, and may have produced waves larger than those observed historically. Such strong swells are inferred to have created a number of geologic features that can be observed today along the coastlines of Bermuda and the Bahamas. In this paper, we investigate the most iconic among these features: massive boulders atop a cliff in North Eleuthera, Bahamas. We combine geologic field surveys, wave models, and boulder transport equations to test the hypothesis that such boulders must have been emplaced by storms of greater-than-historical intensity. By contrast, our results suggest that with the higher relative sea level (RSL) estimated for the Bahamas during MIS 5e, boulders of this size could have been transported by waves generated by storms of historical intensity. Thus, while the megaboulders of Eleuthera cannot be used as geologic proof for past “superstorms,” they do show that with rising sea levels, cliffs and coastal barriers will be subject to significantly greater erosional energy, even without changes in storm intensity.

Paleo relative sea-level (RSL) indicators formed during the Marine Isotope Stage (MIS) 5e have been reported by a large number of studies worldwide. Despite this, three main aspects are seldom reported: (1) use of high-precision survey techniques applied to MIS 5e RSL indicators; (2) application of modern analogs to understand the indicative meaning of MIS 5e RSL indicators; (3) estimates of the effects of glacial isostatic adjustment (GIA) on the MIS 5e records. In this study, we show how the three points above have been addressed in a focused study on Last Interglacial outcrops on the island of Mallorca. We measured the elevation of several RSL indicators with high-accuracy differential GPS (vertical accuracies down to 0.1 m) and we established the relationship between each RSL indicator and the paleo sea level through calculation of the indicative meaning for each RSL indicator. In particular, we present a novel technique to calculate the indicative meaning of fossil beach deposits with a phase-averaged morphodynamic model (CSHORE). We show how this approach helps overcoming difficulties with the survey of the modern analogs for these indicators. Our results show that two paleo RSLs are imprinted in Mallorca at + 2.9 ± 0.8 m and + 11.3 ± 1.0 m. We then compare our field-based results with modelled paleo RSL, calculated from the predictions of the ice-earth coupled ANICE-SELEN model, using few different ice-sheet melting scenarios during MIS 5e. We conclude that indicative ranges can be derived from relatively simple morphodynamic models and that the comparison of field-derived and modelled RSL values is a good method to validate possible scenarios of MIS 5e sea-level variability, especially in absence of precise dating.

Topographic changes due to mantle convection affected the elevation of last interglacial sea-level records across the globe., Estimating minimum ice volume during the last interglacial based on local sea-level indicators requires that these indicators are corrected for processes that alter local sea level relative to the global average. Although glacial isostatic adjustment is generally accounted for, global scale dynamic changes in topography driven by convective mantle flow are generally not considered. We use numerical models of mantle flow to quantify vertical deflections caused by dynamic topography and compare predictions at passive margins to a globally distributed set of last interglacial sea-level markers. The deflections predicted as a result of dynamic topography are significantly correlated with marker elevations (>95% probability) and are consistent with construction and preservation attributes across marker types. We conclude that a dynamic topography signal is present in the elevation of last interglacial sea-level records and that the signal must be accounted for in any effort to determine peak global mean sea level during the last interglacial to within an accuracy of several meters.

We propose a novel technique to measure the small-scale three-dimensional features of a shallow-water coral reef using a small drone equipped with a consumer-grade camera, a handheld GPS and structure from motion (SfM) algorithms. We used a GoPro HERO4 with a modified lens mounted on a DJI Phantom 2 drone (maximum total take-off weight

This article reviews key data and debates focused on relative sea-level changes since the Last Interglacial (approximately the last 132,000 years) in the Mediterranean Basin, and their implications for past human populations. Geological and geomorphological landscape studies are critical to archaeology. Coastal regions provide a wide range of resources to the populations that inhabit them. Coastal landscapes are increasingly the focus of scholarly discussions from the earliest exploitation of littoral resources and early hominin cognition, to the inundation of the earliest permanently settled fishing villages and eventually, formative centres of urbanisation. In the Mediterranean, these would become hubs of maritime transportation that gave rise to the roots of modern seaborne trade. As such, this article represents an original review of both the geo-scientific and archaeological data that specifically relate to sea-level changes and resulting impacts on both physical and cultural landscapes from the Palaeolithic until the emergence of the Classical periods. Our review highlights that the interdisciplinary links between coastal archaeology, geomorphology and sea-level changes are important to explain environmental impacts on coastal human societies and human migration. We review geological indicators of sea level and outline how archaeological features are commonly used as proxies for measuring past sea levels, both gradual changes and catastrophic events. We argue that coastal archaeologists should, as a part of their analyses, incorporate important sea-level concepts, such as indicative meaning. The interpretation of the indicative meaning of Roman fishtanks, for example, plays a critical role in reconstructions of late Holocene Mediterranean sea levels. We identify avenues for future work, which include the consideration of glacial isostatic adjustment (GIA) in addition to coastal tectonics to explain vertical movements of coastlines, more research on Palaeolithic island colonisation, broadening of Palaeolithic studies to include materials from the entire coastal landscape and not just coastal resources, a focus on rescue of archaeological sites under threat by coastal change, and expansion of underwater archaeological explorations in combination with submarine geomorphology. This article presents a collaborative synthesis of data, some of which have been collected and analysed by the authors, as the MEDFLOOD (MEDiterranean sea-level change and projection for future FLOODing) community, and highlights key sites, data, concepts and ongoing debates.

Knowledge on the timing and magnitude of past sea-level changes is essential to understand modern and future sea-level variability. Holocene sea-level data from literature on the west coast of Sulawesi, central Indonesia, suggest that this region experienced two relative sea-level highstands over the last 6000 years, with magnitudes exceeding two meters. However, recent datasets from the Indo-Pacific region do not support high-magnitude sea-level oscillations during the Holocene in tectonically stable far-field locations. Here we present a new, high-precision, mid-Holocene sea-level dataset from the Spermonde Shelf off southwest Sulawesi. We surveyed 21 fossil microatolls on the reef flats of two coral islands (Pulau Panambungan and Pulau Barrang Lompo) and referred their elevations to local mean sea level and to the height of living coral. Radiometrically calibrated ages from emergent fossil microatolls on Pulau Panambungan indicate a relative sea-level highstand not exceeding 0.5 m above present at ca. 5600 cal. yr BP. The highstand is followed by a relatively rapid sea-level fall towards present sea level that was reached at around 4000 cal. yr BP. Fossil microatolls from nearby Pulau Barrang Lompo show the same trend, however with a coherent negative vertical offset of about 0.8 m compared to their equivalents on Pulau Panambungan. The largely consistent gradients of both trends (~− 0.14 mm yr− 1), the consistent elevation of living microatolls in the Spermonde, and a number of instructive geomorphic features indicate a localized, post-formational and probably recent drop of the fossil microatolls on the densely populated island Pulau Barrang Lompo. The relative sea-level trend inferred from Pulau Panambungan is well within the range of geophysical predictions based on ANICE-SELEN ice sheet model, which predict a highstand that is significantly lower than those predicted by other GIA models for this area. Although a complete interpretation of the Holocene sea-level history will require additional high-resolution datasets from this and surrounding territories in SE Asia, our results suggest that there was merely a single Holocene highstand in central Indonesia, the magnitude of which was substantially lower than hitherto assumed.

Biological dinitrogen (N2) fixation (diazotrophy, BNF) relieves marine primary producers of nitrogen (N) limitation in a large part of the world oceans. N concentrations are particularly low in tropical regions where coral reefs are located, and N is therefore a key limiting nutrient for these productive ecosystems. In this context, the importance of diazotrophy for reef productivity is still not resolved, with studies up to now lacking organismal and seasonal resolution. Here, we present a budget of gross primary production (GPP) and BNF for a highly seasonal Red Sea fringing reef, based on ecophysiological and benthic cover measurements combined with geospatial analyses. Benthic GPP varied from 215 to 262 mmol C m−2 reef d−1, with hard corals making the largest contribution (41–76%). Diazotrophy was omnipresent in space and time, and benthic BNF varied from 0.16 to 0.92 mmol N m−2 reef d−1. Planktonic GPP and BNF rates were respectively approximately 60- and 20-fold lower than those of the benthos, emphasizing the importance of the benthic compartment in reef biogeochemical cycling. BNF showed higher sensitivity to seasonality than GPP, implying greater climatic control on reef BNF. Up to about 20% of net reef primary production could be supported by BNF during summer, suggesting a strong biogeochemical coupling between diazotrophy and the reef carbon cycle.

International audience; The Last Interglacial (MIS 5e, 128-116 ka) is among the most studied past periods in Earth's history. The climate at that time was warmer than today, primarily due to different orbital conditions, with smaller ice sheets and higher sea-level. Field evidence for MIS 5e sea-level was reported from thousands of sites, but often paleo shorelines were measured with low-accuracy techniques and, in some cases, there are contrasting interpretations about paleo sea-level reconstructions. For this reason, large uncertainties still surround both the maximum sea-level attained as well as the pattern of sea-level change throughout MIS 5e. Such uncertainties are exacerbated by the lack of a uniform approach to measuring and interpreting the geological evidence of paleo sea-levels. In this review, we discuss the characteristics of MIS 5e field observations, and we set the basis for a standardized approach to MIS 5e paleo sea-level reconstructions, that is already successfully applied in Holocene sea-level research. Application of the standard definitions and methodologies described in this paper will enhance our ability to compare data from different research groups and different areas, in order to gain deeper insights into MIS 5e sea-level changes. Improving estimates of Last Interglacial sea-level is, in turn, a key to understanding the behavior of ice sheets in a warmer world. (C) 2016 Elsevier B.V. All rights reserved.

Due to their importance in the assessment of coastal hazards, several studies have focused on geomorphological and sedimentological field evidence of catastrophic wave impacts related to historical tsunami events. Among them, many authors used boulder fields as important indicators of past tsunamis, especially in the Mediterranean Sea. The aim of this study was to understand the mechanism of deposition of clusters of large boulders, consisting of beachrock slabs, which were found on the southern coasts of Lesvos Island (NE Aegean Sea). Methods to infer the origin of boulder deposits (tsunami vs. storm wave) are often based on hydrodynamic models even if different environmental complexities are difficult to be incorporated into numerical models. In this study, hydrodynamic equations did not provide unequivocal indication of the mechanism responsible for boulder deposition in the study area. Further analyses, ranging from geomorphologic to seismotectonic data, indicated a tsunami as the most likely cause of displacement of the boulders but still do not allow to totally exclude the extreme storm origin. Additional historical investigations (based on tsunami catalogues, historical photos and aged inhabitants interviews) indicated that the boulders are likely to have been deposited by the tsunami triggered by the 6.7 Ms Chios-Karaburum earthquake of 1949 or, alternatively, by minor effects of the destructive tsunami produced by 1956's Amorgos Island earthquake. Results of this study point out that, at Mediterranean scale, to flank numerical models with the huge amount of the available historical data become a crucial tool in terms of prevention policies related to catastrophic coastal events.

Recent works (Evelpidou et al., 2012) suggest that the modern tidal notch is disappearing worldwide due sea level rise over the last century. In order to assess this hypothesis, we measured modern tidal notches in several of sites along the Mediterranean coasts. We report observations on tidal notches cut along carbonate coasts from 73 sites from Italy, France, Croatia, Montenegro, Greece, Malta and Spain, plus additional observations carried outside the Mediterranean. At each site, we measured notch width and depth, and we described the characteristics of the biological rim at the base of the notch. We correlated these parameters with wave energy, tide gauge datasets and rock lithology.Our results suggest that, considering 'the development of tidal notches the consequence of midlittoral bioerosion' (as done in Evelpidou et al., 2012) is a simplification that can lead to misleading results, such as stating that notches are disappearing. Important roles in notch formation can be also played by wave action, rate of karst dissolution, salt weathering and wetting and drying cycles. Of course notch formation can be augmented and favoured also by bioerosion which can, in particular cases, be the main process of notch formation and development.Our dataset shows that notches are carved by an ensemble rather than by a single process, both today and in the past, and that it is difficult, if not impossible, to disentangle them and establish which one is prevailing. We therefore show that tidal notches are still forming, challenging the hypothesis that sea level rise has drowned them. © 2015 Elsevier Ltd.

For nearly a century, the Atlantic Coastal Plain (ACP) of the United States has been the focus of studies investigating Pliocene and Pleistocene shorelines, however, the mapping of paleoshorelines was primarily done by using elevation contours on topographic maps. Here we review published geologic maps and compare them to paleoshoreline locations obtained through geomorphometric classification and satellite data. We furthermore present the results of an extensive field campaign that measured the mid-Pliocene (~ 3.3–2.9 Ma) shorelines of the Atlantic Coastal Plain using high-accuracy GPS and digital elevation models. We compare our new dataset to positions and elevations extracted from published maps and find that the extracted site information from earlier studies is prone to significant error, both in the location and, more severely, in the elevation of the paleoshoreline. We also investigate, using geophysical modeling, the origin of post-depositional displacement of the shoreline from Georgia to Virginia. In particular, we correct the elevation of our shoreline for glacial isostatic adjustment (GIA) and then compare the corrected elevation to predictions of mantle flow-induced dynamic topography (DT). While a subset of these models does reconcile the general trends in the observed elevation of the mid-Pliocene shoreline, local discrepancies persist. These discrepancies suggests that either (i) the DT and GIA models presented here do not capture the full range of uncertainty in the input parameters; and/or (ii) other influences, such as sediment loading and unloading or local fault-driven tectonics, may have contributed to post-depositional deformation of the mid-Pliocene shoreline that are not captured in the above models. In this context, our field measurements represent an important observational dataset with which to compare future generations of geodynamic models. Improvements in models for DT, GIA and other relevant processes, together with an expanded, geographically distributed set of shoreline records, will ultimately be the key to obtaining more accurate estimates of eustatic sea level not only in the mid-Pliocene but also earlier in the Cenozoic.

Received 9 December 2014, Revised 9 February 2015, Accepted 12 February 2015, Available online 5 March 2015, Sérgio P. Ávila [et al.], The privileged location of Santa Maria Island (Azores archipelago) in the middle of the North Atlantic makes the fossiliferous outcrops on this island of utmost importance to gain a better understanding of how coeval living communities relate to the broader evolutionary and biogeographic history of the Atlantic basin during the late Neogene and the Quaternary. Here we focus on this island's MIS 5e fossil record, offering a comprehensive review on the palaeobiodiversity, palaeoecology and palaeobiogeography of the biota living in the mid North Atlantic during this interglacial. Several studies in oceanic islands stress the huge impact of sea level changes on insular communities. Pleistocene sea-level changes occur during the short-time events known as “Terminations” (associated to glacial/interglacial shifts) as well as with the onset of glaciations (associated to interglacial/glacial shifts). Both are responsible for extinctions and local disappearance of species, bottleneck effects and formation of new species, resulting in community structure changes. This work increases the number of fossil marine taxa reported from the Last Interglacial deposits of Santa Maria to 143 species. All the 19 new records are molluscs (13 gastropods and 6 bivalves), thus increasing the number of fossil molluscs to 136 species. Although thermophilic members of the “Senegalese” tropical fauna were found in these deposits, many of the most emblematic species (e.g., Persististrombus latus (¼Strombus bubonius), Cymbula safiana, Harpa doris, Cardita senegalensis, Barbatia plicata, Ctena eburnea or Hyotissa hyotis) are absent, suggesting that they did not reach the Azores. Our results indicate that the main differences between the species composition of the MIS 5e and the present-day shallow-water Azorean communities are probably due to the dropping of sea surface temperature associated with the onset of the last glaciation, which had both direct and indirect effects on species ecology. A group of 21 thermophilic species was directly affected by the lower sea surface temperature, whereas a group of four sand-associated species was indirectly but similarly affected by the lowering of the sea level. Both groups have locally disappeared from the Azores. However, none of the extant endemic species found on the studied MIS 5e outcrops was apparently affected by the lowering SST. In contrast to the biogeographical relationships of the recent Azorean shallow marine molluscs, which are predominantly with the Mediterranean Region, Portugal and with the Madeira and Canary Islands archipelagos, the palaeobiogeographical relationships of the MIS 5e Azorean marine molluscs are mainly with Canaries and West Africa. Despite the general low similarity of the biogeographical relationships between the Azores and Cape Verde Archipelago, on both the recent and the MIS 5e analysis, this similarity is nevertheless higher for the MIS 5e mollusc assemblages, emphasizing the role of Cape Verde as an important source of warm-water species during the Last Interglacial.

International audience; Understanding the effects of environmental change on ecosystems requires the identification of baselines that may act as reference conditions. However, the continuous change of these references challenges our ability to define the true natural status of ecosystems. The so-called sliding baseline syndrome can be overcome through the analysis of quantitative time series, which are, however, extremely rare. Here we show how combining historical quantitative data with descriptive 'naturalistic' information arranged in a chronological chain allows highlighting long-term trends and can be used to inform present conservation schemes. We analysed the long-term change of a coralligenous reef, a marine habitat en-demic to the Mediterranean Sea. The coralligenous assemblages of Mesco Reef (Ligurian Sea, NW Mediterranean) have been studied, although discontinuously, since 1937 thus making available both detailed descriptive information and scanty quantitative data: while the former was useful to understand the natural history of the ecosystem, the analysis of the latter was of paramount importance to provide a formal measure of change over time. Epi-benthic assemblages remained comparatively stable until the 1990s, when species replacement , invasion by alien algae, and biotic homogenisation occurred within few years, leading to a new and completely different ecosystem state. The shift experienced by the cor-alligenous assemblages of Mesco Reef was probably induced by a combination of seawater warming and local human pressures, the latter mainly resulting in increased water turbidity; in turn, cumulative stress may have favoured the establishment of alien species. This study showed that the combined analysis of quantitative and descriptive historical data represent a precious knowledge to understand ecosystem trends over time and provide help to identify baselines for ecological management.