Projections Of Future Sea Level Rise Research Articles

Coastal Airports and Rising Sea Levels

Griggs, G., 2020. Coastal airports and rising sea levels. Journal of Coastal Research, 36(5), 1079–1092. Coconut Creek (Florida), ISSN 0749-0208.Most of the world's major cities are located along coastlines, and their large international airports are typically built either very close to sea level or on filled shallow coastal waters. These large facilities handle thousands of flights and millions of passengers annually, and in addition to being critical infrastructure, they are huge economic engines. Being very close to sea level, however, many of these airports are already exposed to extreme flood events (hurricanes, typhoons, large storms, and high tides) and in the future will face increasing risks with global sea-level rise. LaGuardia, John F. Kennedy (JFK), and Newark all suffered some flood damage during Superstorm Sandy in 2012. San Francisco and Oakland airports have already developed plans to build walls to protect them from 2 to 3 ft (0.6 to 0.9 m) of additional sea-level rise. In addition to these airports, the Federal Aviation Administration has designated the airports at Philadelphia, Washington National, Miami, Tampa, Ft. Lauderdale, Louis Armstrong New Orleans, and Honolulu as at-risk from future storm surge and high water from extreme events. A rising ocean is inevitable and will be additive over time with extreme events. The existing elevations of individual airports combined with projections of future sea-level rise can provide important guidance on when these facilities are likely to be exposed to tidal flooding and, therefore, when airport management should begin to plan to respond or adapt to the future threats.

Story mapping and sea level rise

While interactive maps are important tools for risk communication, most maps omit the lived experiences and personal stories of the community members who are most at risk. We describe a project to develop an interactive tool that juxtaposes coastal residents' videorecorded stories about sea level rise and coastal flooding with an interactive map that shows future sea level rise projections. We outline project development including digital platform selection, project design, participant recruitment, and narrative framing, and tie our design decisions to rhetorical and ethical considerations of interest for others developing interactive tools with community participation.

A new open-source viscoelastic solid earth deformation module implemented in Elmer (v8.4)

Abstract. We present a new, open-source viscoelastic solid earth deformation model, Elmer/Earth. Using the multi-physics finite-element package Elmer, a model to compute viscoelastic material deformation has been implemented into the existing linear elasticity solver routine. Unlike approaches often implemented in engineering codes, our solver accounts for the restoring force of buoyancy within a system of layers with depth-varying density. It does this by directly integrating the solution of the system rather than by applying stress-jump conditions in the form of Winkler foundations on inter-layer boundaries, as is usually needed when solving the minimization problem given by the stress divergence in commercial codes. We benchmarked the new model with results from a commercial finite-element engineering package (ABAQUS, v2018) and another open-source code that uses viscoelastic normal mode theory, TABOO, using a flat-earth setup loaded by a cylindrical disc of 100 km in diameter and 100 m in height at the density of ice. Evaluating the differences in predicted surface deformation at the centre of the load and two distinctive distances (100 and 200 km), average deviations of 7 and 2.7 cm of Elmer/Earth results to ABAQUS and TABOO, respectively, were observed. In view of more than 100 cm maximum vertical deformation and the different numerical methods and parameters, these are very encouraging results. Elmer is set up as a highly scalable parallel code and distributed under the (L)GPL license, meaning that large-scale computations can be made without any licensing restrictions. Scaling figures presented in this paper show good parallel performance of the new model. Additionally, the high-fidelity ice-sheet code Elmer/Ice utilizes the same source base as Elmer and thereby the new model opens the way to undertaking high-resolution coupled ice-flow–solid-earth deformation simulations, which are required for robust projections of future sea-level rise and glacial isostatic adjustment.

Surface mass balance downscaling through elevation classes in an Earth system model: application to the Greenland ice sheet

Abstract. The modeling of ice sheets in Earth system models (ESMs) is an active area of research with applications to future sea level rise projections and paleoclimate studies. A major challenge for surface mass balance (SMB) modeling with ESMs arises from their coarse resolution. This paper evaluates the elevation class (EC) method as an SMB downscaling alternative to the dynamical downscaling of regional climate models. To this end, we compare EC-simulated elevation-dependent surface energy and mass balance gradients from the Community Earth System Model 1.0 (CESM1.0) with those from the regional climate model RACMO2.3. The EC implementation in CESM1.0 combines prognostic snow albedo, a multilayer snow model, and elevation corrections for two atmospheric forcing variables: temperature and humidity. Despite making no corrections for incoming radiation and precipitation, we find that the EC method in CESM1.0 yields similar SMB gradients to RACMO2.3, in part due to compensating biases in snowfall, surface melt, and refreezing gradients. We discuss the sensitivity of the results to the lapse rate used for the temperature correction. We also evaluate the impact of the EC method on the climate simulated by the ESM and find minor cooling over the Greenland ice sheet and Barents and Greenland seas, which compensates for a warm bias in the ESM due to topographic smoothing. Based on our diagnostic procedure to evaluate the EC method, we make several recommendations for future implementations.

Marine ice sheet instability amplifies and skews uncertainty in projections of future sea-level rise

Sea-level rise may accelerate significantly if marine ice sheets become unstable. If such instability occurs, there would be considerable uncertainty in future sea-level rise projections due to imperfectly modeled ice sheet processes and unpredictable climate variability. In this study, we use mathematical and computational approaches to identify the ice sheet processes that drive uncertainty in sea-level projections. Using stochastic perturbation theory from statistical physics as a tool, we show mathematically that the marine ice sheet instability greatly amplifies and skews uncertainty in sea-level projections with worst-case scenarios of rapid sea-level rise being more likely than best-case scenarios of slower sea-level rise. We also perform large ensemble simulations with a state-of-the-art ice sheet model of Thwaites Glacier, a marine-terminating glacier in West Antarctica that is thought to be unstable. These ensemble simulations indicate that the uncertainty solely related to internal climate variability can be a large fraction of the total ice loss expected from Thwaites Glacier. We conclude that internal climate variability alone can be responsible for significant uncertainty in projections of sea-level rise and that large ensembles are a necessary tool for quantifying the upper bounds of this uncertainty.

Uncertain seas: probabilistic modeling of future coastal flood zones

ABSTRACTFuture sea-level rise will likely expand the inland extent of storm surge inundation and, in turn, increase the vulnerability of the people, properties and economies of coastal communities. Modeling future storm surge inundation enhanced by sea-level rise uses numerous data sources with inherent uncertainties. There is uncertainty in (1) hydrodynamic storm surge models, (2) future sea-level rise projections, and (3) topographic digital elevation models representing the height of the coastal land surface. This study implemented a Monte Carlo approach to incorporate the uncertainties of these data sources and model the future 1% flood zone extent in the Tottenville neighborhood of New York City (NYC) in a probabilistic, geographical information science (GIS) framework. Generated spatiotemporal statistical products indicate a range of possible future flood zone extents that results from the uncertainties of the data sources and from the terrain itself. Small changes in the modeled land and water heights within the estimated uncertainties of the data sources results in larger uncertainty in the future flood zone extent in low-lying areas with smaller terrain slope. An interactive web map, UncertainSeas.com, visualizes these statistical products and can inform coastal management policies to reduce the vulnerability of Tottenville, NYC to future coastal inundation.

Automated detection of basal icequakes and discrimination from surface crevassing

ABSTRACTIcequakes at or near the bed of a glacier have the potential to allow us to investigate the interaction of ice with the underlying till or bedrock. Understanding this interaction is important for studying basal sliding of glaciers and ice streams, a critical process in ice dynamics models used to constrain future sea-level rise projections. However, seismic observations on glaciers can be dominated by seismic energy from surface crevassing. We present a method of automatically detecting basal icequakes and discriminating them from surface crevassing, comparing this method to a commonly used spectrum-based method of detecting icequakes. We use data from Skeidararjökull, an outlet glacier of the Vatnajökull Ice Cap, South-East Iceland, to demonstrate that our method outperforms the commonly used spectrum-based method. Our method detects a higher number of basal icequakes, has a lower rate of incorrectly identifying crevassing as basal icequakes and detects an additional, spatially independent basal icequake cluster. We also show independently that the icequakes do not originate from near the glacier surface. We conclude that the method described here is more effective than currently implemented methods for detecting and discriminating basal icequakes from surface crevassing.

Response of Mangroves to Late Holocene Sea-Level Change: Palaeoecological Evidence from Sumatra, Indonesia

This study was conducted with aim to reconstruct the late Holocene mangrove history and to investigate if mangroves can be resilient to current and projected sea-level rise (SLR). The palynological record from a sediment core in the Mendahara Ilir region (MI) in Sumatra was compared with available sea level reconstructions from sites close to MI (Malacca Strait and Singapore). The palynological results show that the mangrove swamp forest was already present in MI ca. 2300 years ago. At time, the sea-level was estimated to be ca. 2 m higher than the present level, thus indicating persistence of mangroves in MI for the current global increase scenario of more than 1 m SLR by 2100. However, the estimated rate of change from the MI core are ca. 2.2 mm/yr. These values are much lower than current (5.0 mm/yr) and future (7 mm/yr) estimates. Thus posing a threat on the resilience and the capacity to adapt of the mangrove swamp forest. Additionally, the palynological results indicate that the mangrove swamp forests were quickly moving seaward and landward following regression and transgression phases in MI. Without a clear inland free path, such migration will be impeded under current and future projections of SLR.

Present day and future scenarios of coastal erosion and flooding processes along the Italian Adriatic coast: the case of Molise region

Coastal erosion and flooding are the main hazards affecting coastal areas, especially low-lying ones, which are particularly prone to damage by storm surges. Due to climate change and socio-economic development, the potential impacts of coastal hazards are globally increasing, and erosion and flooding processes will persist in the future especially when considering the future sea level rise projections. In this paper, we have applied an index-based methodology for the evaluation of the present-day susceptibility to erosion and flooding processes along an Italian Adriatic coastal stretch, the Molise coast. The susceptibility indexes that characterize the coastal system in terms of beach and dune system morphologies, shoreline evolution, wave climate effect, river features and coastal topography, have allowed for dividing the study coast into stretches according to their degree of erosion and flooding susceptibility. To identify the hotspot areas, i.e., the areas characterized by the highest potential coastal risk, susceptibility and socio-economic exposure indexes have been combined. The latter have been evaluated for coastal sectors of 1 km according to the CRAF 1 phase of the RISC-KIT index-method, based on indicators referring to land use categories, economic activities and social vulnerability. Taking in consideration the IPCC sea level projections, future hazard scenarios based on estimated global sea level rise by 2065 and 2100 have been evaluated by means of specific erosion and flooding models executed for the hotspot areas. These scenarios have shown that sea level rise will cause strong erosion of beach and dune systems along the study coast, exposing the economic activities and ecological assets to potential serious damage. The study highlights that correct predictions of future coastal hazard scenarios are essential for the assessment of the long term coastal risk and the definition of related prevention and mitigation measures.

Bounding probabilistic sea-level projections within the framework of the possibility theory

Despite progresses in climate change science, projections of future sea-level rise remain highly uncertain, especially due to large unknowns in the melting processes affecting the ice-sheets in Greenland and Antarctica. Based on climate-models outcomes and the expertise of scientists concerned with these issues, the IPCC provided constraints to the quantiles of sea-level projections. Moreover, additional physical limits to future sea-level rise have been established, although approximately. However, many probability functions can comply with this imprecise knowledge. In this contribution, we provide a framework based on extra-probabilistic theories (namely the possibility theory) to model the uncertainties in sea-level rise projections by 2100 under the RCP 8.5 scenario. The results provide a concise representation of uncertainties in future sea-level rise and of their intrinsically imprecise nature, including a maximum bound of the total uncertainty. Today, coastal impact studies are increasingly moving away from deterministic sea-level projections, which underestimate the expectancy of damages and adaptation needs compared to probabilistic laws. However, we show that the probability functions used so-far have only explored a rather conservative subset of sea-level projections compliant with the IPCC. As a consequence, coastal impact studies relying on these probabilistic sea-level projections are expected to underestimate the possibility of large damages and adaptation needs.

Sea-level feedback lowers projections of future Antarctic Ice-Sheet mass loss

The stability of marine sectors of the Antarctic Ice Sheet (AIS) in a warming climate has been identified as the largest source of uncertainty in projections of future sea-level rise. Sea-level fall near the grounding line of a retreating marine ice sheet has a stabilizing influence on the ice sheets, and previous studies have established the importance of this feedback on ice age AIS evolution. Here we use a coupled ice sheet–sea-level model to investigate the impact of the feedback mechanism on future AIS retreat over centennial and millennial timescales for a range of emission scenarios. We show that the combination of bedrock uplift and sea-surface drop associated with ice-sheet retreat significantly reduces AIS mass loss relative to a simulation without these effects included. Sensitivity analyses show that the stabilization tends to be greatest for lower emission scenarios and Earth models characterized by a thin elastic lithosphere and low-viscosity upper mantle, as is the case for West Antarctica.

Sea level change under IPCC-A2 scenario in Bohai, Yellow, and East China Seas

Because of the environmental and socioeconomic impacts of anthropogenic sea level rise (SLR), it is very important to understand the processes leading to past and present SLRs towards more reliable future SLR projections. A regional ocean general circulation model (ROGCM), with a grid refinement in the Bohai, Yellow, and East China Seas (BYECSs), was set up to project SLR induced by the ocean dynamic change in the 21st century. The model does not consider the contributions from ice sheets and glacier melting. Data of all forcing terms required in the model came from the simulation of the Community Climate System Model version 3.0 (CCSM3) under the International Panel on Climate Change (IPCC)-A2 scenario. Simulation results show that at the end of the 21st century, the sea level in the BYECSs will rise about 0.12 to 0.20 m. The SLR in the BYECSs during the 21st century is mainly caused by the ocean mass redistribution due to the ocean dynamic change of the Pacific Ocean, which means that water in the Pacific Ocean tends to move to the continental shelves of the BYECSs, although the local steric sea level change is another factor.

Probabilistic reanalysis of twentieth-century sea-level rise.

Estimating and accounting for twentieth-century global mean sea level (GMSL) rise is critical to characterizing current and future human-induced sea-level change. Several previous analyses of tide gauge records--employing different methods to accommodate the spatial sparsity and temporal incompleteness of the data and to constrain the geometry of long-term sea-level change--have concluded that GMSL rose over the twentieth century at a mean rate of 1.6 to 1.9 millimetres per year. Efforts to account for this rate by summing estimates of individual contributions from glacier and ice-sheet mass loss, ocean thermal expansion, and changes in land water storage fall significantly short in the period before 1990. The failure to close the budget of GMSL during this period has led to suggestions that several contributions may have been systematically underestimated. However, the extent to which the limitations of tide gauge analyses have affected estimates of the GMSL rate of change is unclear. Here we revisit estimates of twentieth-century GMSL rise using probabilistic techniques and find a rate of GMSL rise from 1901 to 1990 of 1.2 ± 0.2 millimetres per year (90% confidence interval). Based on individual contributions tabulated in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, this estimate closes the twentieth-century sea-level budget. Our analysis, which combines tide gauge records with physics-based and model-derived geometries of the various contributing signals, also indicates that GMSL rose at a rate of 3.0 ± 0.7 millimetres per year between 1993 and 2010, consistent with prior estimates from tide gauge records.The increase in rate relative to the 1901-90 trend is accordingly larger than previously thought; this revision may affect some projections of future sea-level rise.

Tidal and seasonal effects on survival rates of the endangered California clapper rail: does invasive Spartina facilitate greater survival in a dynamic environment?

Invasive species frequently degrade habitats, disturb ecosystem processes, and can increase the likelihood of extinction of imperiled populations. However, novel or enhanced functions provided by invading species may reduce the impact of processes that limit populations. It is important to recognize how invasive species benefit endangered species to determine overall effects on sensitive ecosystems. For example, since the 1990s, hybrid Spartina (Spartina foliosa × alterniflora) has expanded throughout South San Francisco Bay, USA, supplanting native vegetation and invading mudflats. The endangered California clapper rail (Rallus longirostris obsoletus) uses the tall, dense hybrid Spartina for cover and nesting, but the effects of hybrid Spartina on clapper rail survival was unknown. We estimated survival rates of 108 radio-marked California clapper rails in South San Francisco Bay from January 2007 to March 2010, a period of extensive hybrid Spartina eradication, with Kaplan–Meier product limit estimators. Clapper rail survival patterns were consistent with hybrid Spartina providing increased refuge cover from predators during tidal extremes which flood native vegetation, particularly during the winter when the vegetation senesces. Model averaged annual survival rates within hybrid Spartina dominated marshes before eradication (Ŝ = 0.466) were greater than the same marshes posttreatment (Ŝ = 0.275) and a marsh dominated by native vegetation (Ŝ = 0.272). However, models with and without marsh treatment as explanatory factor for survival rates had nearly equivalent support in the observed data, lending ambiguity as to whether hybrid Spartina facilitated greater survival rates than native marshland. Conservation actions to aid in recovery of this endangered species should recognize the importance of available of high tide refugia, particularly in light of invasive species eradication programs and projections of future sea-level rise.

Establishing relative sea level trends where a coast lacks a long term tide gauge

Vulnerability assessment of coastal areas to projected sea level rise requires incorporation of historic trends in relative sea level change as an exposure factor. Most shorelines of developing countries lack long term tide gauges, such as the Pacific Islands region, which are especially vulnerable to climate change impacts. This study has the objective of demonstrating how long-term relative sea level trends can be derived from proxy records, on the tectonically unstable main island of Fiji. At Tikina Wai on the western coast, while elevations of present mangrove zones of Rhizophora stylosa, Rhizophora samoensis and Bruguiera gymnorrhiza were <1.2 m around mean sea level, sediment cores down to 3 m showed mangrove occurrence meters lower than they can grow today. Pollen analysis identified past locations of these mangrove species zones, and the present day elevations of the species were used to reconstruct past sea levels. Results of this study showed that relative sea-level has been slowly rising for the last several centuries at about 2.1 mm a−1, yet mangrove communities have remained resilient with nearly equivalent net sedimentation rates, though with some zone retreat landwards. With such local subsidence, the Tikina Wai district is more exposed to future sea level rise projections than stable coastal areas elsewhere, with additional exposure in having a micro-tidal range. Adaptation actions identified to address this risk include enhancement of sedimentation under mangrove communities through coastal and catchment planning to remove obstructions to sediment supply, reducing non-climate stresses to increase organic production, and replanting of degraded areas. Such information on relative sea level trends can be used to identify where adaptation resources are best concentrated.

Implications, Planning, and Design Considerations for Rising Sea Levels at the Coast

Implications, Planning, and Design Considerations for Rising Sea Levels at the Coast

Integrated assessment of sea-level rise adaptation strategies using a Bayesian decision network approach

The exposure to sea-level rise (SLR) risks emerges as a challenging issue in the broader debate about the possible consequences of global environmental change for at least four reasons: the potentially serious impacts, the very high uncertainty regarding future projections of SLR and their effects on the environmental and socio-economic system, the multiple scales involved, and the need to take effective management decisions in terms of climate change adaptation. Unfortunately, mechanistic models generally demonstrated a limited ability to characterise in appropriate detail how complex coastal systems and their constituent parts may respond to climate change drivers and to possible adaptation initiatives. The research reported here develops an innovative methodological framework, which integrates different research areas – participatory and probabilistic modelling, and decision analysis – within a coordinated process aimed at decision support. The effectiveness of alternative adaptation measures in a lagoon in north-east Italy is assessed by means of Bayesian Decision Network (BDN) models, developed upon judgments elicited from selected experts. A concept map of the system was first developed in a group brainstorming context and was later evolved into BDN models, thus providing a simplified quantitative structure. Conditional probabilities, quantifying the causal links between the direct and indirect consequences of SLR on the area of study, are elicited from the experts. The proposed methodological framework allows the integrated assessment of factors and processes belonging to different domains of knowledge. Moreover, it activates an informed and transparent participatory process involving disciplinary experts and policy makers, where the main risk factors are considered together with the expected effects of the adaptation options, with effective treatment and communication of the uncertainty pervading the SLR issue. Finally, the framework shows potentials for being further developed and applied to consider new evidences and/or different adaptation strategies, and it results sufficiently flexible to be adopted and effectively reused in other similar case studies.

Effect of Sea‐Level Rise on Salt Water Intrusion near a Coastal Well Field in Southeastern Florida

A variable-density groundwater flow and dispersive solute transport model was developed for the shallow coastal aquifer system near a municipal supply well field in southeastern Florida. The model was calibrated for a 105-year period (1900 to 2005). An analysis with the model suggests that well-field withdrawals were the dominant cause of salt water intrusion near the well field, and that historical sea-level rise, which is similar to lower-bound projections of future sea-level rise, exacerbated the extent of salt water intrusion. Average 2005 hydrologic conditions were used for 100-year sensitivity simulations aimed at quantifying the effect of projected rises in sea level on fresh coastal groundwater resources near the well field. Use of average 2005 hydrologic conditions and a constant sea level result in total dissolved solids (TDS) concentration of the well field exceeding drinking water standards after 70 years. When sea-level rise is included in the simulations, drinking water standards are exceeded 10 to 21 years earlier, depending on the specified rate of sea-level rise.

Retraction Note: Constraints on future sea-level rise from past sea-level change

This Letter presented projections of future sea-level rise based on simulations of the past 22,000 years of sea-level history using a simple, empirical model linking sea-level rise to global mean-temperature anomalies. One of the main conclusions of the Letter was that the model results supported the projections of sea-level rise during the twenty-first century that are reported in the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Unfortunately, we have since found that our projections were affected by two oversights in our model approach. First, we tested the sensitivity of our results to the length of the time step used in the integration of the model for the period of deglaciation, which we found to be robust. However, we overlooked that the simulations of the twentieth and twenty-first centuries are sensitive to this time step, which led to an overestimation of the sea-level response to warming in the simulations for these centuries. Second, we did not include the effect of the uncertainty in the temperature reconstructions since the Medieval Climate Anomaly in our uncertainty estimates for the twenty-first-century projections. This led to an inconsistency between the twentieth-century simulation used to test the predictive capability of the model and the twenty-first-century simulation, owing to a provisional allowance for warming since the Little Ice Age in the twentieth-century simulations. Thus we no longer have confidence in our projections for the twentieth and twenty-first centuries, and for this reason the authors retract the results pertaining to sea-level rise after 1900. Both our simulations of the last deglaciation, and the result that the equilibrium response of sea-level change to temperature is non-linear over the last deglaciation, are robust to the length of the time step used, and are still valid.We thank S. Rahmstorf and M. Vermeer for bringing these issues to our attention.

Understanding global sea levels: past, present and future

The coastal zone has changed profoundly during the 20th century and, as a result, society is becoming increasingly vulnerable to the impact of sea-level rise and variability. This demands improved understanding to facilitate appropriate planning to minimise potential losses. With this in mind, the World Climate Research Programme organised a workshop (held in June 2006) to document current understanding and to identify research and observations required to reduce current uncertainties associated with sea-level rise and variability. While sea levels have varied by over 120 m during glacial/interglacial cycles, there has been little net rise over the past several millennia until the 19th century and early 20th century, when geological and tide-gauge data indicate an increase in the rate of sea-level rise. Recent satellite-altimeter data and tide-gauge data have indicated that sea levels are now rising at over 3 mm year−1. The major contributions to 20th and 21st century sea-level rise are thought to be a result of ocean thermal expansion and the melting of glaciers and ice caps. Ice sheets are thought to have been a minor contributor to 20th century sea-level rise, but are potentially the largest contributor in the longer term. Sea levels are currently rising at the upper limit of the projections of the Third Assessment Report of the Intergovernmental Panel on Climate Change (TAR IPCC), and there is increasing concern of potentially large ice-sheet contributions during the 21st century and beyond, particularly if greenhouse gas emissions continue unabated. A suite of ongoing satellite and in situ observational activities need to be sustained and new activities supported. To the extent that we are able to sustain these observations, research programmes utilising the resulting data should be able to significantly improve our understanding and narrow projections of future sea-level rise and variability.