Local Sea Level Research Articles

Correcting MIS5e and 5a sea-level estimates for tectonic uplift, an example from southern California

Along tectonically active margins, the difference in elevations between global sea levels during highstands and uplifted marine terraces is a function of both tectonics and glacial-isostatic adjustment (GIA). However, disentangling the relative influence of these two processes remains a challenge for those trying to gain insights into either process. In this study, we outline a strategy for isolating the tectonic contribution to marine isotope stage (MIS) 5e and 5a marine terrace elevations for the southern California coast by determining the cosmogenic radionuclide burial age and elevation of the early Pleistocene (1.48 ± 0.17 Ma) Clairemont Terrace in San Diego. Using this older terrace as a datum for calculating tectonic uplift rate provides a much longer time period to average out uncertainties in past local or relative sea levels (RSL) that arise from ambiguities in GIA parameters and global meltwater volumes. The assumption of constant uplift rates is warranted for this portion of the California coast given its relatively simple tectonic setting on the rift flank of the Salton Trough. From this approach, we determine an average uplift rate of 0.066 ± 0.020 mm/yr or 0.055 ± 0.013 mm/yr, depending on the RSL model used for the time of the Clairemont Terrace formation, for much of the San Diego coastline. Correcting for this tectonic uplift rate leaves an estimate of 15.1 + 2.6/-3.1 m (16.4 + 1.9/-2.6 m) and 4.8 ± 1.9 m (5.6 ± 1.5 m) for RSL during MIS5e and MIS5a, respectively. These new estimates of MIS5e and MIS5a sea levels along the southern California coast provide important constraints on GIA parameters and former ocean and ice volumes.

Early Pennsylvanian fluvial - Aeolian interplay in the Amazonas Basin (central-western Gondwana) and its relation to marine transgression

The Monte Alegre Formation corresponds to the main reservoir rock in the Amazonas Basin petroleum system in Brazil and is correlated with the Pennsylvanian rocks of the Parnaíba and Solimões basins. Previous outcrop and well-based studies are concentrated on the southern edge of the basin and show that the Monte Alegre Formation basically represents an aeolian, deltaic and transitional marine succession. However, there is no published research that demonstrates the depositional system in the northern edge of Amazonas Basin. In this sense, outcrop-based facies and stratigraphic analysis is carried-out to understand the distal influence of marine incursion into the basin and its relationship with paleogeography in the Upper Carboniferous. The data show that the aeolian Monte Alegre system is represented by a braided fluvial system formed by five architectural elements: (i) sandy bedform, (ii) downstream-accretion macroform, (iii) gravel bars and bedforms, (iv) channel and (v) laminated sand sheets, pointing to a braided depositional system. The aeolian succession overlies the fluvial system and is represented by medium-scale trough cross-bedding and large-scale planar cross-bedded sandstones resulting from the accumulation and migration of transverse dunes toward the northwest that grade upward to dry interdunes and aeolian sand sheet deposits that are interbedded, consisting basically of translatent ripple cross-lamination and low-angle cross-stratified lamination sandstones related to water table raises. The stratigraphic record defines a wetting-upward stacking pattern of Monte Alegre Formation resulting from local sea level rise as a result the advance of the marine incursion that settled in the central-western region of Gondwana during the Late Carboniferous. Thus, in addition to corroborating the paleo wind directions predicted for the region during the Late Carboniferous, these deposits help to understand the paleoenvironmental relations between the northern and southern edges of the Amazonas Basin.

Future sea level rise along the coast of China and adjacent region under 1.5 °C and 2.0 °C global warming

Although future sea level rise along the China coast has been projected by various studies for different representative concentration pathways (RCPs), the projections for different warming thresholds, e.g. 1.5 °C and 2.0 °C, have not been done specifically for this region, to the best of our knowledge. We provide such a projection here based on the climate projections of Coupled Model Intercomparison Project Phase 5 (CMIP5). The projections are given for 20 tide-gauge stations along the coast of China, Korea, Japan, and Vietnam. Vertical land motion (VLM) is also estimated for stations that have tide gauge records and satellite altimetry both covering the period of 1993–2018. Local land motion (LLM) is then estimated by subtracting the land motion due to glacial isostatic adjustment (GIA) from VLM. Without considering LLM, sea level rise by 2100 at median probability is projected to be 38–49 cm relative to the average sea level over 1986–2005 under warming of 1.5 °C, and increase to 46–57 cm when the warming threshold is increased to 2.0 °C. The steric component is the main contributor to this increase in sea level. Inclusion of LLM will not affect the sea level increase between the two warming thresholds, but it will make the local sea level rise by 2100 at certain locations substantially higher (up to 36 cm) or lower (up to 13 cm).

Climate change, resilience, and the Native American Fisher-hunter-gatherers of the late Holocene on the Georgia coast, USA

The Georgia Coast of the eastern United States boasts some of the largest and spatially complex Late Archaic sites in North America, with the most famous of these being shell rings. The shell ring village phenomenon and its larger ceremonial landscapes did not, however, last throughout the Late Archaic. Climate shifts that led to local relative sea level change in the area at around 3800 cal. BP appears to have resulted in conditions that suppressed shellfish productivity and ultimately led to the uneven abandonment of shell ring sites. Our understanding of these changes along the Georgia Coast is limited by the fact that much of the research focuses exclusively on large shell midden sites. Investigations at several large terminal Late Archaic sites demonstrate continuity in the size of these occupations compared to earlier Late Archaic sites (i.e., shell rings), demonstrating a socio-ecological resiliency in these small-scale societies. We argue that, contrary to narratives of collapsing socio-ecological systems, the terminal Late Archaic was a time when displaced communities coalesced and forged new community bonds in the wake of a shifting resource base.

Suspended particulate matter for sediment accumulation on inundated anthropogenic marshland in the southern North Sea – Potential, thresholds and limitations

Determining the availability of suspension load, i.e. suspended particulate matter (SPM), in shallow marine tidal systems is necessary to estimate whether coastal lowlands may experience vertical accretion rates that keep pace with global sea level rise. In particular anthropogenic marshland areas are affected by limitations of SPM accumulation due to artificial structures such as dikes and revetments that act as transport barriers.With the use of an autonomously operating turbidity measuring network installed at and around the Hallig Langeness in the North Frisian Wadden Sea, we have analyzed eight individual inundations on this island-like marshland during harsh weather conditions. The results reveal that the majority of the available SPM could not accumulate on the marshland due to adjacent coastal protection measures. This reduction in SPM affects especially grain sizes within the very fine to fine sand range between 63 and 200 μm that can account for up to 70% of the sampled SPM during an inundation. Furthermore, we have determined a tidal average SPM concentration threshold of 0.15 g/l should be available on the tidal flat in order to allow sufficient vertical marshland accretion. Although this threshold is exceeded by the determined SPM on the tidal flats around Langeness, the available SPM on the marshland after passing the coastal protection measures is at most 20%. Hence, an optimized coastal management strategy has the potential to increase the sediment accumulation rate on the marshlands by a factor of five, which might allow for keeping pace with local sea level rise.

Sea Ice Freeboard in the Ross Sea from Airborne Altimetry IcePod 2016–2017 and a Comparison with IceBridge 2013 and ICESat 2003–2008

As part of the Polynyas and Ice Production in the Ross Sea (PIPERS) project, the IcePod system onboard the LC-130 aircraft based at McMurdo Station was flown over the Ross Sea, Antarctica in November 2016 and 2017, with the purpose of repeating the same lines that NASA’s Operation IceBridge (OIB) aircraft flew over in 2013. We resampled the lidar data into 70 m pixels (similar to the footprint size of OIB L2 and ICESat data) and took the mean of the lowest 2% elevation values of 25 km (50 km) length along a flight track as the local sea level of the central 25 km (50 km). Most of the IcePod data were over the same flight lines taken by OIB in 2013, so the total freeboard changes from 2013 to 2016 and 2017 were examined. Combining with the ICESat (2003–2008), we obtained a better picture of total freeboard and its interannual variability in the Ross Sea. The pattern of the sea ice distribution supports that new ice produced in coastal polynyas was transported northward by katabatic winds off the ice shelf. Compared to ICESat years, sea ice near the coast was thicker, while sea ice offshore was thinner in the more recent OIB/IcePod years. The results also showed that, in general, sea ice was thicker in 2017 compared to 2013 or 2016—0.02–0.55 m thicker in total freeboard.

Coastal engineering evolution in low-lying areas and adaptation practice since the eleventh century, Jiangsu Province, China

Coastal engineering is an important measure in coping with coastal risks. With global warming and sea level rising, the sustainable adaptation of the low-lying areas becomes urgent. An in-depth understanding of the relationship between coastal engineering and environmental changes can help improve the adaptation capability for climate change. Here, we use historical documents and synthesis approach to examine coastal engineering evolution on the Jiangsu coast, the largest lowland area along China’s coastlines, and explore its response to local sea level and land use changes. The results show that coastal engineering here experienced a long-term period centered on sea-dike construction, with a shift from primary function of storm surge prevention since the eleventh century, towards a green coastal engineering approach in recent years. On the century scale, there was a close connection between local sea level change and coastal engineering change, while on the ten-year scale, population dynamics and land use changes were the key driving factors. Since the future climate and sea level change magnitude will be beyond what has been observed on the Jiangsu coast, it would be sensible to define a “critical time” that divides the near future and remote future. On such a basis, a strategic plan for the remote future may be formulated to prepare for the critical time when inevitable inundation occurs, and a second strategic plan may be adopted for the near future, to buy time for the coastal communities to make necessary preparations and at the same time to continue to use the resources. For the “near future,” a green coastal engineering approach (in combination with the experiences gained from the Jiangsu coast) should be developed to provide a low cost, high efficiency technique for coastal defense schemes. The thoughts outlined above may be applicable also to a number of low-lying coastal regions of developing countries.

Zonation of mangrove flora and fauna in a subtropical estuarine wetland based on surface elevation.

In the context of sea‐level rise (SLR), an understanding of the spatial distributions of mangrove flora and fauna is required for effective ecosystem management and conservation. These distributions are greatly affected by tidal inundation, and surface elevation is a reliable quantitative indicator of the effects of tidal inundation. Most recent studies have focused exclusively on the quantitative relationships between mangrove‐plant zonation and surface elevation, neglecting mangrove fauna. Here, we measured surface elevation along six transects through the mangrove forests of a subtropical estuarine wetland in Zhenzhu Bay (Guangxi, China), using a real‐time kinematic global positioning system. We identified the mangrove plants along each transect and investigated the spatial distributions of arboreal, epifaunal, and infaunal molluscs, as well as infaunal crabs, using traditional quadrats. Our results indicated that almost all mangrove forests in the bay were distributed within the 400–750 m intertidal zone, between the local mean sea level and mean high water (119 cm above mean sea level). Mangrove plants exhibited obvious zonation patterns, and different species tended to inhabit different niches along the elevation gradient: Aegiceras corniculatum dominated in seaward locations while Lumnitzera racemosa dominated in landward areas. Mangrove molluscs also showed distinct patterns of spatial zonation related to surface elevation, independent of life‐form and season. The spatial distributions of some molluscs were correlated to the relative abundances of certain mangrove plants. In contrast, the spatial distributions of crabs were not related to surface elevation. To the best of our knowledge, this is the first study to explicitly quantify the influences of surface elevation on the spatial distributions of mangrove fauna. This characterization of the vertical ranges of various flora and fauna in mangrove forests provides a basic framework for future studies aimed at predicting changes in the structure and functions of mangrove forests in response to SLR.

Assessment on Shoreline Retreat in Response to Sea Level Rise – Chennai Coast

Dhanalakshmi, S. and Kankara, R.S., 2020. Assessment on shoreline retreat in response to sea level rise – Chennai coast. In: Sheela Nair, L.; Prakash, T.N.; Padmalal, D., and Kumar Seelam, J. (eds.), Oceanic and Coastal Processes of the Indian Seas. Journal of Coastal Research, Special Issue No. 89, pp. 145-149. Coconut Creek (Florida), ISSN 0749-0208.In the present condition, the rise in sea level due to climate change is a serious threat for the environment. Global average sea levels are predicted as 1.8 mm/y during 1870-2009 and nearly 2.8 mm/y along the Indian Coast by Intergovernmental Panel on Climate change (IPCC). Impacts of rise in sea-level will be the loss of land in coastal areas through erosion, submergence of the coastal landscape and the threat of inundation. Shore erosion causes the shoreline to retreat and this leads to affecting the erosion zone by moving the shoreline inland. In this study, the attempt is made to demarcate the impact of sea level rise along the Chennai coast (Tamil Nadu) located along the southeast coast of India. This area experiences threat from many disasters such as storm, cyclone, flood, tsunami and long-term sea level rise. The shoreline has been extracted and using DSAS tool in ArcGIS, long-term (1990-2012, 1990-2013, 1990-2014, 1990-2015 and 1990-2016) were analyzed using Linear regression Rate and Weighted Linear Regression. 36.7% of the coast was seen with eroding condition. Overall long-term analysis trend suggest that more than 60% of the region falls in stable to low accretion. Projection of climate change-induced SLR at different RCPs (2.6, 4.5, 6, 8.5) of IPCC AR5 on different time scale (2025, 2050, 2075, 2100) for the coasts of Chennai. The values range from 7.1 cm to 36.87 cm for RCP 2.6; 7.37 cm to 49.84 cm for RCP 4.5; 7.16 cm to 51.75 cm for RCP 6; 7.38 cm to 77.88 cm for RCP 8.5. Shoreline retreat to an increase in local sea level was mapped using the Bruun Rule. Since the Bruun Rule (BR) has some limitations, the modified Bruun rule was used to analyze the inundation factor. The area of horizontal inundation is estimated as ∼1.6 km (Bruun rule) and ∼1.1 km (Modified Bruun Rule). The required data was processed using GIS environment. Since we adhere to the fact that the coastal change is not a periodical accumulation per year, but that it entraps a value of future crisis assessment and gives a literal warning about the shore to be persevered.

Simulation of Environmental Changes Consdering Sea-level Rise Near a Mega-scale Coastal Dike (Saemangeum [SMG] Dike, Korea)

Yoo, S.-C. and Suh, S.-W., 2020. Simulation of environmental changes considering sea-level rise near a mega-scale coastal dike (Saemangeum [SMG] dike, Korea). In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 309–314. Coconut Creek (Florida), ISSN 0749-0208.The construction of one of the biggest coastal dikes in Korea, the 33-km long Saemangeum (SMG) dike, was completed in 2006. Coastal environmental changes resulted in tidal asymmetry in the near field (i.e., adjacent to the dike) and the far field (i.e., up to opposite part of the Yellow Sea). Coastal hydrodynamic variations and engineering developments for gate operations (to maintain inner reservoir water quality (WQ) standards) rapidly alter coastal environments. The sea level is expected to rise by 80 cm by the end of this century, and an additional 21.4 cm of seasonal local summer sea level jump will serve as a reversing factor of WQ. This study applied the ADCIRC and EFDC models to simulate regional and local hydrodynamic and WQ changes. The far-field impacts of the SMG will occur continuously till year 2100 along the Chinese coast with M2 mordulation. The target water management level was set to elevation with respect to mean sea level (EL) as -1.5 m, which is very limited in terms of free discharge time for gate operation. According to the tidal excursion and residence time simulations, only 14% of gate operations in a month will be possible compared to the existing all-year-round condition, and only 4% will be exchangeable in summer. It is found that SMG yields alteration of tidal hydrodynamics showing overall de-amplification of ∼10 cm in the Yellow Sea (YS), especially along the west coast of Korea (WCK), as well as a slight amplification of ∼10 cm on the eastern coast of China. In addition, reducing the time for inner discharge because of the rising outer sea level directly influences WQ both in the areas near the gates and the inner water due to the increased residence time. Intensive study including long-term variations in tidal asymmetry and associated morphologies is needed to manage the hydrodynamic and/or WQ changes associated with such mega-scale coastal constructions.

Tropical Cyclone Induced Wave Setup around New Caledonia during Cyclone COOK (2017)

Jullien, S.; Aucan, J.; Lefevre, J.; Peltier, A., and Menkes, C.E., 2020. Tropical cyclone induced wave setup around New Caledonia during cyclone COOK (2017). In: Malvarez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 1454-1459. Coconut Creek (Florida), ISSN 0749-0208.Tropical cyclone (TC)-induced coastal flooding arises from a combination of atmospheric surge, and energetic wave-induced setup. TC-generated waves in deep water considerably evolve in shallow water before reaching the coast. Islands surrounded by a barrier reef and lagoon are a particular case of steep and irregular bathymetry over which waves undergo various transformations, and induce complex wave-current interactions. The present study investigates the TC-induced coastal impact on the reef environment of New Caledonia in the tropical southwest Pacific. An unstructured wave-current model simulation encompassing New Caledonia and Vanuatu is used to describe the complete TC-induced waves impact, from wave generation to propagation and transformation in the coastal area. Comparison with in-situ measurements are performed during cyclone COOK in 2017. The results show that coastlines with a double protection (barrier and fringing reefs) are relatively sheltered from the waves induced by TCs (significant wave height is 3 m at the coast vs. 13 m offshore) while shores fronting the reef passes are more severely exposed with waves reaching 9 m close to the coast. Setups and currents that are associated to wave breaking on the barrier reef induce strong lagoon currents and localized sea level anomalies that does not necessarily reach the coast. In more sheltered bays, wave breaking at the entrance of the bay acts against outgoing currents. This phenomenon leads to an additional elevation of the mean water level in the bay.

Examining the response of an eastern Australian mangrove forest to changes in hydro-period over the last century

This study examines mangrove substrate production within a mangrove basin forest in the Tweed Estuary, northern New South Wales, Australia. This is achieved using high resolution dating of 239+240Pu, 236U and 210Pb in mangrove sediments to examine both the modes and rates of mangrove substrate production. Results show a shift in the mode of substrate production occurred approximately 70 years ago in response to human modification of the Tweed Estuary (hydrologic changes). At that time, mangrove substrate production shifted from being dominated by sedimentation processes (fine silt accumulation) to being dominated by biological processes (mangrove root production). Since that time, mangrove peat has been accreting at the study site at the same rate as local sea level rise (SLR), implying current rates of peat substrate development are tuned to increasing sea level. A further implication of the shift to biological accretion at rates corresponding with SLR is that the studied mangrove basin is sequestering C at increasing rates due to subsurface root production.

Improved and extended tide gauge records for the British Isles leading to more consistent estimates of sea level rise and acceleration since 1958

This paper describes methods of obtaining improved estimates of long-term sea level trends for the British Isles. This is achieved by lengthening the sea level records where possible, then removing known sources of variability, and then further adjusting for datum errors that are revealed by the previous processes after verification using metadata from archived sources. Local sea level variability is accounted for using a tide and surge model. Far field variability is accounted for using a “common mode”. This combination reduces the residual variability seen at tide gauges around the coast of the British Isles to the point that a number of previously unrecognised steps in individual records become apparent, permitting a higher level of quality control to be applied. A comprehensive data archaeology exercise was carried out which showed that these step-like errors are mostly coincident with recorded site-specific changes in instrumentation, and that in many cases the periodic tide gauge calibration records can be used to quantify these steps. A smaller number of steps are confirmed by “buddy-checking” against neighbouring tide gauges. After accounting for the observed steps, using levelling information where possible and an empirical fit otherwise, the records become significantly more consistent. The steps are not found to make a large difference to the trend and acceleration observed in UK sea level overall, but their correction results in much more consistent estimates of first order (Sea Level Rise) and second order (Sea Level Acceleration) trends over this 60-year period. We find a mean rate of sea level rise of 2.39 ± 0.27 mm yr−1, and an acceleration of 0.058 ± 0.030 mm yr−2 between Jan. 1958 and Dec. 2018. The cleaner dataset also permits us to show more clearly that the variability other than that derived from local meteorology is indeed consistent around the UK, and relates to sea level changes along the eastern boundary of the North Atlantic.

Steps to Develop Early Warning Systems and Future Scenarios of Storm Wave-Driven Flooding Along Coral Reef-Lined Coasts

Tropical coral reef-lined coasts are exposed to storm wave-driven flooding. In the future, flood events during storms are expected to occur more frequently and to be more severe due to sea-level rise, changes in wind and weather patterns, and the deterioration of coral reefs. Hence, disaster managers and coastal planners are in urgent need of decision-support tools. In the short-term, these tools can be applied in Early Warning Systems (EWS) that can help to prepare for and respond to impending storm-driven flood events. In the long-term, future scenarios of flooding events enable coastal communities and managers to plan and implement adequate risk-reduction strategies. Modeling tools that are used in currently available coastal flood EWS and future scenarios have been developed for open-coast sandy shorelines, which have only limited applicability for coral reef-lined shorelines. The tools need to be able to predict local sea levels, offshore waves, as well as their nearshore transformation over the reefs, and translate this information to onshore flood levels. In addition, future scenarios require long-term projections of coral reef growth, reef composition, and shoreline change. To address these challenges, we have formed the UFORiC (Understanding Flooding of Reef-lined Coasts) working group that outlines its perspectives on data and model requirements to develop EWS for storms and scenarios specific to coral reef-lined coastlines. It reviews the state-of-the-art methods that can currently be incorporated in such systems and provides an outlook on future improvements as new data sources and enhanced methods become available.

Alkenone Distributions and Hydrogen Isotope Ratios Show Changes in Haptophyte Species and Source Water in the Holocene Baltic Sea

AbstractThe Baltic Sea, a dynamic, marginal marine basin, experienced a number of large changes in salinity during the Holocene as a result of fluctuations in global and local sea level related to melting of glacial ice sheets and subsequent isostatic rebound. These changes likely had pronounced effects on the species composition of haptophytes, a common phytoplankton group found in the Baltic Sea. This dynamic environment provides the ideal setting to study how species change impacts distribution and hydrogen isotope ratios of long‐chain alkenones (δ2HC37), haptophyte‐specific biomarkers. Here we analyzed the aforementioned parameters in Holocene sediments covering the contrasting hydrological phases of the Baltic Sea. Alkenone distributions changed with different Baltic Sea salinity phases, suggesting that species shifts coincide with salinity change. δ2HC37 values show two major shifts: one in the middle of the freshwater Ancylus Lake phase (10.6 to 7.7 ka) and a second at the transition from the brackish Littorina Sea phase (7.2 to 3 ka) into the fresher Modern Baltic (3 ka to the present). The first shift represents a significant enrichment of 50‰, which cannot be explained by salinity or species changes only. At this time, the isotopically depleted ice sheets had melted, and only the relatively enriched freshwater source remained. The second shift, coincident with a change in distribution, is likely caused by a change in species composition alone. These findings show that hydrogen isotope ratios of long‐chain alkenones, combined with their relative distribution, can be used to reconstruct changes in source water.

Sea-ice freeboard and thickness in the Ross Sea from airborne (IceBridge 2013) and satellite (ICESat 2003–2008) observations

AbstractNASA's Operation IceBridge mission flew over the Ross Sea, Antarctica (20 and 27 November 2013) and collected data with Airborne Topographic Mapper (ATM) and Digital Mapping System (DMS). Using the DMS and reflectivity of ATM L1B, leads are detected to define local sea level height. The total freeboard is then obtained and converted to ice thickness. The estimated mean sea-ice thickness values are found to be in the 0.48–0.99 m range. Along the N-S track, sea ice was thinner southward rather than northward of the fluxgate, resulting in two peaks of modal thickness: 0.35 m (south) and 0.7 m (north). This supports that new ice produced in coastal polynyas is transported northward by katabatic winds off the ice-shelf. The lowest (2%) elevation method used for freeboard retrieval for ICESat is also tested for ATM data. It is found that the lowest elevation method tends to overestimate freeboard, but mean values are less affected than mode values. Using mean thickness values of ICESat and ATM along the ‘fluxgate’, separating the shelf from the deep ocean, the exported ice volume at this ‘fluxgate’ is found to be higher during the ICESat years (2003–2008) than during the IceBridge year (2013).

Enhancing the protection of archaeological sites as an integrated coastal management strategy: the case of the Posillipo Hill (Naples, Italy)

The coasts of the Mediterranean Sea are characterized by the presence of many archaeological remains (ports, protection structures, villas, fish tanks, etc.) that have been emplaced since the Roman Age and have persisted until present day. Due to their archaeological value, these structures represent an inestimable cultural heritage at regional and national scale. As consequence of local sea level variations, most of these structures are today submerged and, for this reason, they represent an important geo-archaeological proxy for the reconstruction of the ancient coastal landscape. Nevertheless, marine processes, such as coastal erosion and/or flooding, are among the main factors contributing to their damage and, hence, protection and conservation strategies need to be enhanced. In this paper, the vulnerability to marine factors of five coastal archaeological sites has been assessed. The investigated sites are located along the Posillipo Hill, one of the most beautiful and attractive coastal sector in the Gulf of Naples (Southern Italy). The analysis has been carried out by applying a vulnerability index method, which is based on the combination of a number of different indicators accounting for both marine processes and the typology of the remains. The results of this study allowed identifying the most vulnerable sites that require, for their conservation and sustainable usability, urgent management strategies.

Can We Resolve the Basin‐Scale Sea Level Trend Budget From GRACE Ocean Mass?

AbstractUnderstanding sea level changes at a regional scale is important for improving local sea level projections and coastal management planning. Sea level budget (SLB) estimates derived from the sum of observation of each component close for the global mean. The sum of steric and Gravity Recovery and Climate Experiment (GRACE) ocean mass contributions to sea level calculated from measurements does not match the spatial patterns of sea surface height trends from satellite altimetry at 1° grid resolution over the period 2005–2015. We investigate potential drivers of this mismatch aggregating to subbasin regions and find that the steric plus GRACE ocean mass observations do not represent the small‐scale features seen in the satellite altimetry. In addition, there are discrepancies with large variance apparent at the global and hemispheric scale. Thus, the SLB closure on the global scale to some extent represents a cancelation of errors. The SLB is also sensitive to the glacial isostatic adjustment correction for GRACE and to altimery orbital altitude. Discrepancies in the SLB are largest for the Indian‐South Pacific Ocean region. Taking the spread of plausible sea level trends, the SLB closes at the ocean‐basin scale ( ) but with large spread of magnitude, one third or more of the trend signal. Using the most up‐to‐date observation products, our ocean‐region SLB does not close everywhere, and consideration of systematic uncertainties diminishes what information can be gained from the SLB about sea level processes, quantifying contributions, and validating Earth observation systems.

Global Trends of Sea Surface Gravity Wave, Wind, and Coastal Wave Setup

AbstractAssessing trends of sea surface wave, wind, and coastal wave setup is of considerable scientific and practical importance in view of recent and projected long-term sea level rise due to global warming. Here we analyze global significant wave height (SWH) and wind data from 1993 to 2015 and a wave model to (i) calculate wave age and explain the causal, or the lack thereof, relationship between wave and wind trends; and (ii) estimate trends of coastal wave setup and its contributions to secular trends of relative sea level at coastal locations around the world. We show in-phase, increasing SWH and wind trends in regions dominated by younger waves, and decreasing SWH trends where older waves dominate and are unrelated to the local wind trends. In the central North Pacific where wave age is transitional, in-phase decreasing wave and wind trends are found over the west-northwestern region, but wave and wind trends are insignificantly correlated in the south-southeastern region; here, a reversed, upward momentum flux from wave to wind is postulated. We show that coastal wave setup depends primarily on open-ocean SWH but only weakly on wind, varying approximately like SWH/(wind speed)1/5. The wave-setup trends are shown to be increasing along many coastlines where the local relative sea level trends are also increasing: the North and Irish Seas, Mediterranean Sea, East and South Asian seas, and eastern United States, exacerbating the potential for increased floods along these populated coastlines.

Interannual to decadal variability within and across the major Eastern Boundary Upwelling Systems

Climate variability and climate change in Eastern Boundary Upwelling Systems (EBUS) affect global marine ecosystems services. We use passive tracers in a global ocean model hindcast at eddy-permitting resolution to diagnose EBUS low-frequency variability over 1958–2015 period. The results highlight the uniqueness of each EBUS in terms of drivers and climate variability. The wind forcing and the thermocline depth, which are potentially competitive or complementary upwelling drivers under climate change, control EBUS low-frequency variability with different contributions. Moreover, Atlantic and Pacific upwelling systems are independent. In the Pacific, the only coherent variability between California and Humboldt Systems is associated with El Niño Southern Oscillation. The remaining low-frequency variance is partially explained by the North and South Pacific expressions of the Meridional Modes. In the Atlantic, coherent variability between Canary and Benguela Systems is associated with upwelling trends, which are not dynamically linked and represent different processes. In the Canary, a negative upwelling trend is connected to the Atlantic Multi-decadal Oscillation, while in the Benguela, a positive upwelling trend is forced by a global sea level pressure trend, which is consistent with the climate response to anthropogenic forcing. The residual variability is forced by localized offshore high sea level pressure variability.