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Sea-level rise (SLR) causes the frequency of extreme sea levels to amplify. Projections of the frequency amplification of extremes are often computed for arbitrary future years and for the historical centennial event. Such projections may therefore not provide salient information to adaptation planners, as they do not indicate when certain flood risk thresholds will be crossed given the current degree of local coastal flood protection.To better support adaptation planning, we introduce a framework that extends the emerging timing perspective on sea-level rise to the frequency amplification of extreme sea levels. Moreover, by relating amplification factors to model estimates of local flood protection standards, we project the timing of a range of decreases in the local degree of protection. The projections are based on tide gauge observations (GESLA3) and relative sea-level projections of IPCC AR6 until 2150.Our central estimates indicate that the estimated degrees of protection will on average be exceeded 10 times more frequently within the next 30 years (the lead time that large adaptation measures may take) at 26 & 32% of the tide gauges considered, and annually at 4 & 8%, for respectively a low & high emissions scenario (SSP1-2.6 & SSP3-7.0). Furthermore, in scenarios in which sea-level rise will accelerate, the same decreases in the degree of coastal protection will occur substantially faster in the future. Our projection framework may help adaptation planners to assess the available lead time and useful lifetime of protective infrastructure, given unacceptable decreases in the degree of coastal protection., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

The amplification of coastal hazards such as distant-source tsunamis under future relative sea-level rise (RSLR) is poorly constrained. In southern California, the Alaska-Aleutian subduction zone has been identified as an earthquake source region of particular concern for a worst-case scenario distant-source tsunami. Here, we explore how RSLR over the next century will influence future maximum nearshore tsunami heights (MNTH) at the Ports of Los Angeles and Long Beach. Earthquake and tsunami modeling combined with local probabilistic RSLR projections show the increased potential for more frequent, relatively low magnitude earthquakes to produce distant-source tsunamis that exceed historically observed MNTH. By 2100, under RSLR projections for a high-emissions representative concentration pathway (RCP8.5), the earthquake magnitude required to produce >1 m MNTH falls from ~Mw9.1 (required today) to Mw8.0, a magnitude that is ~6.7 times more frequent along the Alaska-Aleutian subduction zone., Rising sea level in the next century exposes the Ports of Los Angeles and Long Beach to higher hazards from Alaskan tsunamis. By 2100, waves generated by an M8 Alaskan earthquake cause similar impacts in California to waves from an Alaskan M9 today.

Global sea level rise (SLR) may impose substantial economic costs to coastal communities worldwide, but characterizing its global impact remains challenging because SLR costs depend heavily on natural characteristics and human investments at each location—including topography, the spatial distribution of assets, and local adaptation decisions. To date, several impact models have been developed to estimate global costs of SLR, yet the limited availability of open-source and modular platforms that easily ingest up-to-date socioeconomic and physical data sources limits the ability of existing systems to transparently incorporate new insights. In this paper, we present a modular open-source platform designed to address this need, providing end-to-end transparency from global input data to a scalable least-cost optimization framework that estimates adaptation and net SLR costs for nearly 10,000 global coastline segments and administrative regions. Our approach accounts both for uncertainty in the magnitude of global SLR and spatial variability in local relative sea level rise. Using this platform, we evaluate costs across 110 possible socioeconomic and SLR trajectories in the 21st century. We find annual global SLR costs of $180 billion to $200 billion in 2100 assuming optimal adaptation, moderate emissions (RCP 4.5) and middle-of-the-road (SSP 2) socioeconomic trajectories. Under the highest SLR scenarios modeled, this value ranges from $400 billion to $520 billion. We make this platform publicly available in an effort to spur research collaboration and support decision-making, with segment level physical and socioeconomic input characteristics provided at https://doi.org/10.5281/zenodo.6449231, source code for this dataset at https://doi.org/10.5281/zenodo.6456115, the modeling framework at https://doi.org/10.5281/zenodo.6453099, and model results at https://doi.org/10.5281/zenodo.6014086.

Coastal tidal wetlands produce and accumulate significant amounts of organic carbon (C) that help to mitigate climate change. However, previous data limitations have prevented a robust evaluation of the global rates and mechanisms driving C accumulation. Here, we go beyond recent soil C stock estimates to reveal global tidal wetland C accumulation and predict changes under relative sea level rise, temperature and precipitation. We use data from literature study sites and our new observations spanning wide latitudinal gradients and 20 countries. Globally, tidal wetlands accumulate 53.65 (95%CI: 48.52–59.01) Tg C yr−1, which is ∼30% of the organic C buried on the ocean floor. Modeling based on current climatic drivers and under projected emissions scenarios revealed a net increase in the global C accumulation by 2100. This rapid increase is driven by sea level rise in tidal marshes, and higher temperature and precipitation in mangroves. Countries with large areas of coastal wetlands, like Indonesia and Mexico, are more susceptible to tidal wetland C losses under climate change, while regions such as Australia, Brazil, the USA and China will experience a significant C accumulation increase under all projected scenarios., The global tidal wetlands accumulate 53.65 (95%CI: 48.52-59.01) Tg C yr-1, which is ∼30% of the organic C buried on the ocean floor. Modelling based on current climatic drivers and under projected emissions scenarios revealed a net increase in the global C accumulation by 2100.

This study reports a new and significantly enhanced analysis of US flood hazard at 30 m spatial resolution. Specific improvements include updated hydrography data, new methods to determine channel depth, more rigorous flood frequency analysis, output downscaling to property tract level, and inclusion of the impact of local interventions in the flooding system. For the first time, we consider pluvial, fluvial, and coastal flood hazards within the same framework and provide projections for both current (rather than historic average) conditions and for future time periods centered on 2035 and 2050 under the RCP4.5 emissions pathway. Validation against high-quality local models and the entire catalog of FEMA 1% annual probability flood maps yielded Critical Success Index values in the range 0.69–0.82. Significant improvements over a previous pluvial/fluvial model version are shown for high-frequency events and coastal zones, along with minor improvements in areas where model performance was already good. The result is the first comprehensive and consistent national-scale analysis of flood hazard for the conterminous US for both current and future conditions. Even though we consider a stabilization emissions scenario and a near-future time horizon, we project clear patterns of changing flood hazard (3σ changes in 100 years inundated area of −3.8 to +16% at 1° scale), that are significant when considered as a proportion of the land area where human use is possible or in terms of the currently protected land area where the standard of flood defense protection may become compromised by this time.

Sea-level budgets account for the contributions of processes driving sea-level change, but are predominantly focused on global-mean sea level and limited to the 20th and 21st centuries. Here we estimate site-specific sea-level budgets along the U.S. Atlantic coast during the Common Era (0–2000 CE) by separating relative sea-level (RSL) records into process-related signals on different spatial scales. Regional-scale, temporally linear processes driven by glacial isostatic adjustment dominate RSL change and exhibit a spatial gradient, with fastest rates of rise in southern New Jersey (1.6 ± 0.02 mm yr−1). Regional and local, temporally non-linear processes, such as ocean/atmosphere dynamics and groundwater withdrawal, contributed between −0.3 and 0.4 mm yr−1 over centennial timescales. The most significant change in the budgets is the increasing influence of the common global signal due to ice melt and thermal expansion since 1800 CE, which became a dominant contributor to RSL with a 20th century rate of 1.3 ± 0.1 mm yr−1., Sea-level rise is an important part of climate change, but most sea-level budgets are global and cannot capture important regional changes. Here the authors estimate sea-level budgets along the U.S. Atlantic coast, finding a faster rate of rise during the 20th century than any time in the past 2000 years.

Sea level rise will cause spatial shifts in economic activity over the next 200 years. Using a spatially disaggregated, dynamic model of the world economy, this paper estimates the consequences of probabilistic projections of local sea level changes. Under an intermediate scenario of greenhouse gas emissions, permanent flooding is projected to reduce global real GDP by 0.19 percent in present value terms. By the year 2200, a projected 1.46 percent of the population will be displaced. Losses in coastal localities are much larger. When ignoring the dynamic response of investment and migration, the loss in real GDP in 2200 increases from 0.11 percent to 4.5 percent. (JEL E23, F01, Q54, Q56) Desmet and Rossi- Hansberg acknowledge the support and hospitality of PERC while doing part of this research. Kopp, Kulp, and Strauss were supported in part by US National Science Foundation grant ICER- 1663807 and by National Aeronautics and Space Administration grant 80NSSC17K0698. Nagy acknowledges financial support from the Spanish Ministry of Economy and Competitiveness, through the Severo Ochoa Program for Centers of Excellence in R&D (SEV- 2015-0563) and the Juan de la Cierva Grant (FJCI- 2017- 34728); and from the Government of Catalonia, through CERCA and SGR Program (2017-SGR-1393). Oppenheimer acknowledges support from US National Science Foundation Award Number 1520683.

39 pages, 8 figures, 3 tables.-- Gridded Surface Height Anomalies Version 1801. Ver. 1801 available from NASA JPL PO.DAAC, CA, USA(https://doi.org/10.5067/SLREF-CDRV1). Data are also available through Wiese et al. (2017), Global sea level provides an important indicator of the state of the warming climate, but changes in regional sea level are most relevant for coastal communities around the world. With improvements to the sea‐level observing system, the knowledge of regional sea‐level change has advanced dramatically in recent years. Satellite measurements coupled with in situ observations have allowed for comprehensive study and improved understanding of the diverse set of drivers that lead to variations in sea level in space and time. Despite the advances, gaps in the understanding of contemporary sea‐level change remain and inhibit the ability to predict how the relevant processes may lead to future change. These gaps arise in part due to the complexity of the linkages between the drivers of sea‐level change. Here we review the individual processes which lead to sea‐level change and then describe how they combine and vary regionally. The intent of the paper is to provide an overview of the current state of understanding of the processes that cause regional sea‐level change and to identify and discuss limitations and uncertainty in our understanding of these processes. Areas where the lack of understanding or gaps in knowledge inhibit the ability to provide the needed information for comprehensive planning efforts are of particular focus. Finally, a goal of this paper is to highlight the role of the expanded sea‐level observation network—particularly as related to satellite observations—in the improved scientific understanding of the contributors to regional sea‐level change, The research was carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. The authors acknowledge support from the National Aeronautics and Space Administration under Grants 80NSSC17K0565, 80NSSC170567, 80NSSC17K0566, 80NSSC17K0564, and NNX17AB27G. A. A. acknowledgessupport under GRACE/GRACEFO Science Team Grant (NNH15ZDA001N‐GRACE). T. W. acknowledges support by the National Aeronautics and Space Administration (NASA) under the New (Early Career) Investigator Program in Earth Science (Grant: 80NSSC18K0743). C. G. P was supported by the J. Lamar Worzel Assistant Scientist Fund and the Penzance Endowed Fund in Support of Assistant Scientists at the Woods Hole Oceanographic Institution, With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)

The artificial impoundment of water behind dams causes global mean sea level (GMSL) to fall as reservoirs fill but also generates a local rise in sea level due to the increased mass in the reservoir and the crustal deformation this mass induces. To estimate spatiotemporal fluctuations in sea level due to water impoundment, we use a historical data set that includes 6,329 reservoirs completed between 1900 and 2011, as well as projections of 3,565 reservoirs that are expected to be completed by 2040. The GMSL change associated with the historical data (−0.2 mm yr−1 from 1900–2011) is consistent with previous studies, but the temporal and spatial resolution allows for local studies that were not previously possible, revealing that some locations experience a sea level rise of as much as 40 mm over less than a decade. Future construction of reservoirs through ~2040 is projected to cause a GMSL fall whose rate is comparable to that of the last century (−0.3 mm yr−1) but with a geographic distribution that will be distinct from the last century, including a rise in sea level in more coastal areas. The analysis of expected construction shows that significant impoundment near coastal communities in the coming decades could enhance the flooding risk already heightened by global sea level rise., Key Points We present a spatially resolved time series of sea level due to reservoir construction from 1900–2040Some locations in the past century have experienced a reservoir‐induced rise in sea level that exceeds 40 mm over less than a decadeFuture dam construction will cause patterns in sea level change that are different from the past and larger than current projections

Deep uncertainty describes situations when there is either ignorance or disagreement over (1) models used to describe key system processes and (2) probability distributions used to characterize the uncertainty of key variables and parameters. Future projections of Antarctic ice sheet (AIS) mass loss remain characterized by deep uncertainty. This complicates decisions on long‐lived coastal protection projects when determining what margin of safety to implement. If the chosen margin of safety does not properly account for uncertainties in sea level rise, the effectiveness of flood protection could decrease over time, potentially putting lives and properties at a greater risk. To address this issue, we develop a flood damage allowance framework for calculating the height of a flood protection strategy needed to ensure that a given level of financial risk is maintained. The damage allowance framework considers decision maker preferences such as planning horizons, protection strategies, and subjective views of AIS stability. We use Manhattan—with the population and built environment fixed in time—to illustrate how our framework could be used to calculate a range of damage allowances based on multiple plausible scenarios of AIS melt. Under high greenhouse gas emissions, we find that results are sensitive to the selection of the upper limit of AIS contributions to sea level rise. Design metrics that specify financial risk targets, such as expected flood damage, allow for the calculation of avoided flood damages (i.e., benefits) that can be combined with estimates of construction cost and then integrated into existing financial decision‐making approaches (e.g., benefit‐cost analysis)., Key Points Not accounting for sea-level rise when designing ood protection could cause the originally selected margin of safety to decrease over timeDamage allowances provide the heights of flood protection strategies needed to maintain the expected flood damage as sea levels riseBenefit‐cost analysis used for flood protection decision‐making should consider multiple scenarios of Antarctic ice sheet melt

Foraminifera from salt-marsh environments have been used extensively in quantitative relative sea-level reconstructions due to their strong relationship with tidal level. However, the influence of temporal and spatial variability of salt-marsh foraminifera on quantitative reconstructions remains unconstrained. Here, we conducted a monitoring study of foraminifera from four intertidal monitoring stations in New Jersey from high marsh environments over three years that included several extreme weather (temperature, precipitation, and storm surge) events. We sampled four replicates from each station seasonally (four times per year) for a total of 188 samples. The dead foraminiferal assemblages were separated into four site-specific assemblages. After accounting for systematic trends in changes in foraminifera over time among stations, the distribution of foraminiferal assemblages across monitoring stations explained ~87% of the remaining variation, while ~13% can be explained by temporal and/or spatial variability among the replicate samples. We applied a Bayesian transfer function to estimate the elevation of the four monitoring stations. All samples from each station predicted an elevation estimate within a 95% uncertainty interval consistent with the observed elevation of that station. Combining samples into replicate- and seasonal-aggregate datasets decreased elevation estimate uncertainty, with the greatest decrease in aggregate datasets from Fall and Winter. Information about the temporal and spatial variability of modern foraminiferal distributions was formally incorporated into the Bayesian transfer function through informative foraminifera variability priors and was applied to a Common Era relative sea-level record in New Jersey. The average difference in paleomarsh elevation estimates and uncertainties using an informative vs uninformative prior was minimal (

International audience; Changes in sea level lead to some of the most severe impacts of anthropogenic climate change. Consequently, they are a subject of great interest in both scientific research and public policy. This paper defines concepts and terminology associated with sea level and sea-level changes in order to facilitate progress in sea-level science, in which communication is sometimes hindered by inconsistent and unclear language. We identify key terms and clarify their physical and mathematical meanings, make links between concepts and across disciplines, draw distinctions where there is ambiguity, and propose new terminology where it is lacking or where existing terminology is confusing. We include for-mulae and diagrams to support the definitions.

Minimizing the adverse consequences of sea-level change presents a key societal challenge. New modelling is necessary to examine the implications of global policy decisions that determine future greenhouse gas emissions and local policies around coastal risk that influence where and how we live.

Tidal marshes rank among Earth’s vulnerable ecosystems, which will retreat if future rates of relative sea-level rise (RSLR) exceed marshes’ ability to accrete vertically. Here, we assess the limits to marsh vulnerability by analyzing >780 Holocene reconstructions of tidal marsh evolution in Great Britain. These reconstructions include both transgressive (tidal marsh retreat) and regressive (tidal marsh expansion) contacts. The probability of a marsh retreat was conditional upon Holocene rates of RSLR, which varied between −7.7 and 15.2 mm/yr. Holocene records indicate that marshes are nine times more likely to retreat than expand when RSLR rates are ≥7.1 mm/yr. Coupling estimated probabilities of marsh retreat with projections of future RSLR suggests a major risk of tidal marsh loss in the twenty-first century. All of Great Britain has a >80% probability of a marsh retreat under Representative Concentration Pathway (RCP) 8.5 by 2100, with areas of southern and eastern England achieving this probability by 2040., Quantifying the vulnerability of tidal marsh ecosystems to relative sea-level rise (RSLR) is essential if the threat is to be mitigated. Here, the authors analyze the response of Great Britain’s tidal marshes to RSLR during the Holocene and predict an almost inevitable loss of this ecosystem by 2100 under rapid RSLR scenarios.

High-quality relative sea-level (RSL) data reveal spatial and temporal variations in crustal movements during the Holocene, which are used for many applications, ranging from calibrating models of earth rheology and ice sheet reconstructions to the development of coastal lowlands and human occupation. Here, we present a Holocene RSL database for the Atlantic coast of Europe (ACE) and estimate rates of RSL change from the ACE database using a spatio-temporal empirical hierarchical model. The database contains 214 index points, which locate the RSL position in space and time, and 126 limiting dates, which constrain RSL to above or below a certain elevation at a specific point in time. The temporal distribution extends from present to ~11.5 ka, with only 42 index points older than 7 ka. The spatial distribution spans 1700 km from French Flanders (France) to Algarve (Portugal), with more than half of the index points concentrated along the French coast. The ACE database shows RSL was below present during the Holocene. Rates of RSL change were highest during the early Holocene, ranging between 6.8 ± 0.5 mm yr-1 in middle Portugal and 6.3 ± 0.8 mm yr-1 in southern France from 10 to 7 ka. Mid-to late-Holocene rates decreased over time with rates ranging between 0.9 ± 0.4 mm yr-1 in middle France and 0.1 ± 0.5 mm yr-1 in middle Portugal from 4 ka to present. Comparison of the RSL data to output from a glacial-isostatic adjustment model suggests that deglaciation of the British-Irish and Fennoscandian Ice Sheets dominates the large-scale variability captured by the ACE database, which reflects a decreasing influence of the collapsing British-Irish and Fennoscandian peripheral forebulge that migrated from the northeast to the northwest after ~4 ka. (c) 2018 Elsevier Ltd AGA received a postdoctoral grant from the Basque Government ( POS-2014-1-51 ). AC and AGA were supported by Antropicosta (MINECO, CGL2013-41083-P ), Harea-Coastal Geology Research Group ( EJ/GV, IT976-16 ) and Quaternary Unit for Research and Education ( UPV/EHU , UFI11/09 ) grants. REK was supported in part by NSF grants OCE-1458904 and OCE-1702587 . BPH was supported by Singapore Ministry of Education Academic Research Fund Tier 1 RG119/17 , the National Research Foundation Singapore , and the Singapore Ministry of Education, under the Research Centres of Excellence initiative

Future sea-level rise generates hazards for coastal populations, economies, infrastructure, and ecosystems around the world. The projection of future sea-level rise relies on an accurate understanding of the mechanisms driving its complex spatio-temporal evolution, which must be founded on an understanding of its history. We review the current methodologies and data sources used to reconstruct the history of sea-level change over geological (Pliocene, Last Interglacial, and Holocene) and instrumental (tide-gauge and satellite alimetry) eras, and the tools used to project the future spatial and temporal evolution of sea level. We summarize the understanding of the future evolution of sea level over the near (through 2050), medium (2100), and long (post-2100) terms. Using case studies from Singapore and New Jersey, we illustrate the ways in which current methodologies and data sources can constrain future projections, and how accurate projections can motivate the development of new sea-level research questions across relevant timescales. Ministry of Education (MOE) National Research Foundation (NRF) The authors acknowledge funding from Singapore Ministry of Education Academic Research Fund Tier 1 RG119/17, the National Research Foundation Singapore, and the Singapore Ministry of Education, under the Research Centres of Excellence initiative; US National Ocean and Atmospheric Administration (NOAA) Grant NA11OAR4310101; US National Science Foundation (NSF) Grants ICER-1663807, OCE 1458904 and 1702587, EAR 1520683, and Postdoctoral Fellowship 1625150; National Aeronautics and Space Administration (NASA) Grant 80NSSC17K0698; the Community Foundation of New Jersey; and David and Arleen McGlade. This article is a contribution to PALSEA2 (Palaeo-Constraints on Sea-Level Rise), International Geoscience Program (IGCP) Project 639, “Sea Level Change from Minutes to Millennia,” and INQUA Project 1601P “Geographic variability of HOLocene relative SEA level (HOLSEA).” This work is Earth Observatory of Singapore contribution no. 198.