Sea Level Rise

Increasing temperatures due to climate change raise concerns regarding sea level rise in coastal areas. Sea level rise has caused an increase in tidal floods associated with nuisance-level impacts. Nuisance floods are events in which water levels exceed the local threshold for minor impacts. These events can damage infrastructure, cause road closures, and overwhelm storm drains. As sea level has risen along the Georgia coastline, the number of tidal flood days (all days exceeding the nuisance level threshold) has also increased, with the greatest number occurring in 2013 and 2015. Georgia is at extreme risk for sea level rise due to its low elevation along the coast. Continued sea level rise will present major challenges to Georgia’s existing coastal water management system and could cause extensive economic damage through ecosystem damage and losses in property, tourism, and agriculture.

Publications

TitleDescriptionYear
Modeling migration patterns in the USA under sea level riseSea level rise in the United States will lead to large scale migration in the future. We propose a framework to examine future climate migration patterns using models of human migration. Our framework requires that we distinguish between historical versus climate driven migration and recognizes how the impacts of climate change can extend beyond the affected area. We apply our framework to simulate how migration, driven by sea level rise, differs from baseline migration patterns. The results of our case study suggest that the effects of sea level rise are pervasive, expanding beyond coastal areas via increased migration, and disproportionately affecting some areas of the United States.2020
HIGH TIDE TAX: The Price to Protect Coastal Communities from Rising SeasThis study provides the first estimate for the contiguous U.S. of the costs associated with armoring coastal areas that contain public infrastructure and that are projected to be flooded by sea-level rise. The primary focus of this study is estimating the costs of ensuring that roads, rails, and other public infrastructure are protected from the predicted near-term and long-term impacts of sea-level rise under moderate, not worst case, emissions scenarios. 2019
Coastal dynamics and adaptation to uncertain sea level rise: Optimal portfolios for salt marsh migrationMarsh sustainability under rapid sea level rise requires the preservation of transgression zones - undeveloped uplands onto which marshes migrate. This paper develops the first adaptation portfolio model designed to optimize the benefits of a migrating coastal system. Results are illustrated using a case study of marsh conservation in Virginia, USA. Results suggest that models of this type can enhance adaptation benefits beyond those available through current approaches.2019
Ocean at the Door: New Homes and the Rising SeaIn 2018, Climate Central and Zillow produced the first nationwide analysis of the number of new homes in areas vulnerable to coastal flooding in all 24 coastal states and the District of Columbia. This research projected how many homes will become exposed to on-average annual ocean flooding in the coming decades—depending on what choices the world makes around greenhouse-gas pollution today. This report improves those results by incorporating full home footprint data instead of point location estimates, and also provides results for bigger floods, in addition to annual ones.2019
Assessing coastal wetland vulnerability to sea-level rise along the northern Gulf of Mexico coast: Gaps and opportunities for developing a coordinated regional sampling networkIn this study, we quantify the distribution of surface elevation table-marker horizon (SET-MH) stations along the northern Gulf of Mexico coast across states, wetland habitats, and ecologically-relevant abiotic gradients (i.e., gradients in temperature, precipitation, elevation, and relative sea-level rise). Our analyses identify areas with high SET-MH station densities as well as areas with notable gaps. Salt marshes, intermediate elevations, and colder areas with high rainfall have a high number of stations, while salt flat ecosystems, certain elevation zones, the mangrove-marsh ecotone, and hypersaline coastal areas with low rainfall have fewer stations. Our findings represent the first attempt to examine spatial gaps in SET-MH coverage across abiotic gradients. Our analyses can be used to transform a broadly disseminated and unplanned collection of SET-MH stations into a coordinated and strategic regional network. 2017
Climate Change and Homes: Who Would Lose the Most to a Rising Tide?Building on its 2016 analysis of the impact a rising tide could have on U.S. homes, Zillow looked again at how many homes might be underwater by the end of the century — and whether those homes are in the top, middle or bottom tier in their areas. Zillow also calculated the share in urban, suburban and rural areas. Key findings include:
• One-third (32%) of underwater homes would be valued in the bottom third nationally, meaning $123 billion in losses.
• Two in five (39%) underwater homes would be valued in the top third nationally, translating to $597 billion in lost high-end real estate.
• In rural and suburban areas, homes in the top value tier may face particular risk, while in urban areas homes in the bottom value tier are more likely to be affected.
2017
Climate Science Special Report: Fourth National Climate Assessment (NCA4), Volume I This chapter reviews the physical factors driving changes in global mean sea level (GMSL) and those causing additional regional variations in relative sea level (RSL). It presents geological and instrumental observations of historical sea level changes and an assessment of the human contribution to sea level change. It then describes a range of scenarios for future levels and rates of sea level change, and the relationship of these scenarios to the Representative Concentration Pathways (RCPs). Finally, it assesses the impact of changes in sea level on extreme water levels.2017
Sea level rise drives increased tidal flooding frequency at tide gauges along the U.S. East and Gulf Coasts: Projections for 2030 and 2045Tidal flooding is among the most tangible present-day effects of global sea level rise. Here, we utilize a set of NOAA tide gauges along the U.S. East and Gulf Coasts to evaluate the potential impact of future sea level rise on the frequency and severity of tidal flooding. Using the 2001–2015 time period as a baseline, we first determine how often tidal flooding currently occurs. Using localized sea level rise projections based on the Intermediate-Low, Intermediate-High, and Highest projections from the U.S. National Climate Assessment, we then determine the frequency and extent of such flooding at these locations for two near-term time horizons: 2030 and 2045. We show that increases in tidal flooding will be substantial and nearly universal at the 52 locations included in our analysis. Long before areas are permanently inundated, the steady creep of sea level rise will force many communities to grapple with chronic high tide flooding in the next 15 to 30 years.2017
Impediments to inland resettlement under conditions of accelerated sea level riseRecent research suggests that global mean sea level rise may endanger the low-elevation coastal zone sooner than expected, reshaping coastal geography, reducing habitable landmass, and seeding significant coastal out-migrations. Our research reviews the barriers to entry in the noncoastal hinterland. Using three organizing clusters (depletion zones, win-lose zones, and no-trespass zones), we identify principal inland impediments to relocation and provide preliminary estimates of their toll on inland resettlement space. We make the case for proactive adaptation strategies extending landward from on global coastlines and illustrate this position with land use planning responses in Florida and China.2017
Temperature Decouples Ammonium and Nitrite Oxidation in Coastal WatersAnalysis of field data from 270 stations in 29 temperate and subtropical estuaries and lagoons show transient accumulation of nitrite driven primarily by water temperatures, rather than by hypoxia. Increased climate variability and warming coastal waters may therefore increase the frequency of these nitrite peaks, with potential ecosystem consequences that include increased N2O production, NO2– toxicity, and shifts in phytoplankton community composition.2017
Wave Exposure Structures Oyster Distribution on Natural Intertidal Reefs, But Not on Hardened ShorelinesAlthough intertidal oyster reefs are valued for attenuating wave erosion, little attention has been paid to the effects of wave exposure on their distribution. The present study characterized the role of wave exposure in determining the distribution of natural intertidal oyster reefs and of oysters on hardened shorelines (bulkhead and riprap revetments). Wave exposure was determined using the National Oceanic and Atmospheric Administration (NOAA)-developed Wave Exposure Model (WEMo), which integrates adjacent water depth, fetch, and processed wind information, among other variables. Field mapping of oyster reefs in Pamlico and Core sounds, North Carolina, USA, was conducted in summer 2014. Wave exposure was not correlated with the presence of oysters on hardened shorelines. 2017
Centuries of thermal sea-level rise due to anthropogenic emissions of short-lived greenhouse gasesWe show that short-lived greenhouse gases contribute to sea-level rise through thermal expansion (TSLR) over much longer time scales than their atmospheric lifetimes. Chlorofluorocarbons and hydrochlorofluorocarbons have already been phased out under the Montreal Protocol due to concerns about ozone depletion and provide an illustration of how emission reductions avoid multiple centuries of future TSLR. We examine the “world avoided” by the Montreal Protocol by showing that if these gases had instead been eliminated in 2050, additional TSLR of up to about 14 cm would be expected in the 21st century, with continuing contributions lasting more than 500 y. Sea-level rise is often assumed to follow air temperature, but this assumption holds only for TSLR when temperatures are increasing. We present a more complete formulation that is accurate even when atmospheric temperatures are stable or decreasing due to reductions in short-lived gases or net radiative forcing.2017
An empirical analysis of cultural ecosystem values in coastal landscapesThis study describes and analyzes the distribution of cultural ecosystem values found in coastal areas in 5 countries and compares the results with non-coastal areas. Mapped cultural ecosystem values were collected from public participation GIS (PPGIS) processes in the U.S., Australia, New Zealand, Norway, and Malaysia and analyzed to identify the type and intensity of ecosystem values located in coastal areas. Mapped ecosystem values were significantly more abundant in all coastal zones, regardless of ecosystem value category, country, population, or dominant land use. Economic and social values were significantly associated with developed (built) coastal zones, while aesthetic and recreation values were more strongly associated with natural coastal zones. Understanding trade-offs in coastal zone planning and management requires a systematic inventory of the full range of ecosystem services, including cultural services.2017
Migration induced by sea-level rise could reshape the US population landscapeWith millions of potential future migrants in heavily populated coastal communities, SLR scholarship focusing solely on coastal communities characterizes SLR as primarily a coastal issue, obscuring the potential impacts in landlocked communities created by SLR-induced displacement. Here I address this issue by merging projected populations at risk of SLR with migration systems simulations to project future destinations of SLR migrants in the US. I find that unmitigated SLR is expected to reshape the US population distribution, potentially stressing landlocked areas unprepared to accommodate this wave of coastal migrants—even after accounting for potential adaptation. 2017
Coastal Floods: Sea Level Rise and the Human Fingerprint on U.S. Floods since 1950This analysis reviews the assessed human-caused component in global sea level from hourly water level records since 1950 at 27 U.S. tide gauges, creating alternative histories simulating the absence of anthropogenic climate change. Out of 8,726 days when unaltered water level observations exceeded National Weather Service local “nuisance” flood thresholds for minor impacts, 5,809 days did not exceed thresholds in the alternative histories. In other words, human-caused global sea level rise effectively tipped the balance, pushing high water events over the threshold, for about two-thirds of the observed flood days. The fraction has increased from less than half in the 1950s, to more than three-quarters within the last decade (2005-2014), as global sea level has continued to rise.2016
Guide for Considering Climate Change in Coastal ConservationThis guide provides a step-by-step approach, with links to relevant tools, information, and other resources. The document focuses on climate considerations and tools specifically relevant to the coastal environment, including coastal watersheds. The six iterative steps draw on existing guidelines for conservation, as well as newer climate adaptation resources. The information is suitable for anyone working to manage or conserve lands in coastal areas, such as coastal planners, land or watershed conservation organizations, wetland and floodplain managers, emergency managers, and more. The approach provided in this guide can be used to create a new plan if one is needed, to update an existing plan, or to further other types of planning, such as hazard mitigation or comprehensive plans. 2016
Coastal sea level rise with warming above 2 °CHere we provide probabilistic sea level rise projections for the global coastline with warming above the 2°C goal. By 2040, with a 2°C warming, more than 90% of coastal areas will experience sea level rise exceeding the global estimate of 0.2 m, with up to 0.4 m expected along the Atlantic coast of North America and Norway. With a 5°C rise by 2100, sea level will rise rapidly, reaching 0.9 m (median), and 80% of the coastline will exceed the global sea level rise at the 95th percentile upper limit of 1.8 m. The coastal communities of rapidly expanding cities in the developing world, and vulnerable tropical coastal ecosystems, will have a very limited time after midcentury to adapt to sea level rises.2016
Enhanced Atlantic sea-level rise relative to the Pacific under high carbon emission ratesHere we present simulations using a numerical atmospheric-ocean general circulation model with an interactive carbon cycle to evaluate the impact of carbon emission rates on basin-scale ocean heat uptake and sea level. For simulations with emission rates greater than 5 GtC yr−1, sea-level rise is larger in the Atlantic than Pacific Ocean on centennial timescales. This basin-scale asymmetry is related to the shorter flushing timescales and weakening of the overturning circulation in the Atlantic. These factors lead to warmer Atlantic interior waters and greater thermal expansion. We conclude that Atlantic coastal areas may be particularly vulnerable to near-future sea-level rise from present-day high greenhouse gas emission rates.2016
Assessing tidal marsh resilience to sea-level rise at broad geographic scales with multi-metric indicesHere, we develop and apply tidal marsh resilience to sea-level rise (MARS) indices incorporating ten metrics that contribute to overall marsh resilience to SLR. We applied MARS indices to tidal marshes at 16 National Estuarine Research Reserves across the conterminous U.S. This assessment revealed moderate resilience overall, although nearly all marshes had some indication of risk. Pacific marshes were generally more resilient to SLR than Atlantic ones, with the least resilient marshes found in southern New England. We provide a calculation tool to facilitate application of the MARS indices to additional marshes. 2016
EPA Climate Change Indicators in the United States (2016)EPA partners with more than 40 data contributors from various government agencies, academic institutions, and other organizations to compile a key set of indicators related to the causes and effects of climate change. The indicators are published in EPA's report, Climate Change Indicators in the United States, available on this website and in print. The indicators include: Greenhouse Gases, Weather & Climate, Oceans, Snow & Ice, Health & Society, and Ecosystems. 2016
Carbon choices determine US cities committed to futures below sea levelBased on detailed topographic and population data, local high tide lines, and regional long-term sea-level commitment for different carbon emissions and ice sheet stability scenarios, we compute the current population living on endangered land at municipal, state, and national levels within the United States. For unabated climate change, we find that land that is home to more than 20 million people is implicated and is widely distributed among different states and coasts. The total area includes 1,185–1,825 municipalities where land that is home to more than half of the current population would be affected, among them at least 21 cities exceeding 100,000 residents. 2015
Spatial response of coastal marshes to increased atmospheric CO2Coastal marshes provide numerous ecosystem services, are an important carbon sink, and are exposed to drowning as sea-level rise accelerates. Using a meta-analysis of the available observational data, we model the coupled marsh vegetation and morphological dynamics. We find that the fertilization effect of elevated atmospheric CO2 significantly increases marsh resilience to drowning and decreases the spatial extent of marsh retreat under high rates of sea-level rise. While this direct CO2 fertilization effect has so far been neglected in marsh modeling, we find it is central in determining marsh survival under the foreseeable range of climatic changes.2015
Sea Level Changes in the Southeastern United States: Past, Present, and FutureThis paper discusses past, present, and future sea level changes in the southeastern United States. It is aimed at non-scientists and scientists who are not specialists in sea level change. Although this report is about a specific part of the world, sea level change in any region is best viewed in the context of global sea level changes. 2011

Tools

TitleDescriptionYear
Sea Level Rise ViewerNOAA's Digital Ocean program has produced this web mapping tool that enables users tovisualize community-level impacts from coastal flooding or sea level rise (up to 10 feet above average high tides). Photo simulations of how future flooding might impact local landmarks are also provided, as well as data related to water depth, connectivity, flood frequency, socio-economic vulnerability, wetland loss and migration, and mapping confidence.2020
Tutorial for Sea Level Rise Viewer: Marsh MigrationExplore the impacts of sea level rise inundation on local wetlands using the marsh migration tab of NOAA’s Sea Level Rise Viewer. This self-guided tutorial uses an example to help you optimize the viewer and get the This tutorial provides the information natural resource managers, local government planners, and other stakeholders need to guide decisions about where to focus monitoring, restoration, and conservation efforts.2020
Should coastal planners have concern over where land ice is melting?In this study, we exploit an advanced mathematical property of adjoint systems and determine the exact gradient of sea-level fingerprints with respect to local variations in the ice thickness of all of the world’s ice drainage systems. By mapping these fingerprint gradients, we form a new diagnosis tool, henceforth referred to as gradient fingerprint mapping (GFM), that allows for improved assessments of future coastal inundation or emergence. We demonstrate that for Antarctica and Greenland, changes in the predictions of inundation at major port cities depend on the location of the drainage system. For example, in New York, LSL change predictions are greatly sensitive to changes in the northeastern portions of the Greenland Ice Sheet. We apply GFM to 293 major port cities to allow coastal planners to readily calculate LSL change as more reliable predictions of cryospheric mass changes become available.2017
Surging Seas: Ocean at the DoorThe Surging Seas: Ocean at the Door map shows the vulnerability of old and new housing stock to rising seas and chronic floods. Potential flood exposure maps are generated by comparing land elevation to the height of a typical once-a-year flood, plus local sea level rise projections over time. Areas below the resulting heights are classified as being in a “risk zone.” This map displays the number and value of homes located in the selected risk zone, including a special focus on recently built homes. The map incorporates the latest, high-resolution, high-accuracy lidar elevation data supplied by NOAA and provides the ability to search by location name or postal code.
This map is paired with a companion report, brief, and interactive tool (scroll to the “Future Flood Risk to Homes” section of the tool after inputting a location name).
2017
Development and Application of a Method to Identify Salt Marsh Vulnerability to Sea Level RiseIn this study, we exploit an advanced mathematical property of adjoint systems and determine the exact gradient of sea-level fingerprints with respect to local variations in the ice thickness of all of the world’s ice drainage systems. By mapping these fingerprint gradients, we form a new diagnosis tool, henceforth referred to as gradient fingerprint mapping (GFM), that readily allows for improved assessments of future coastal inundation or emergence. We demonstrate that for Antarctica and Greenland, changes in the predictions of inundation at major port cities depend on the location of the drainage system. For example, in London, GFM shows LSL that is significantly affected by changes on the western part of the Greenland Ice Sheet (GrIS), whereas in New York, LSL change predictions are greatly sensitive to changes in the northeastern portions of the GrIS. We apply GFM to 293 major port cities to allow coastal planners to readily calculate LSL change as more reliable predictions of cryospheric mass changes become available.2017

Resources

TitleDescriptionYear
$20B Needed to Shield South Carolina from Rising Sea LevelsIn a state where rising sea levels are threatening oceanfront property, building $20 billion worth of seawalls would protect South Carolina’s coast from the effects of climate change during the next 20 years, a new study by the Center for Climate Integrity says. The $20 billion cost estimate was based on a 6-inch rise in sea level and a 21-inch storm surge. The report says South Carolina needs 3,202 miles of seawalls — enough to cover the entire coast — to shield its beaches, marshes and tidal rivers from sea-level rise. 2020
Where America's Climate Migrants Will Go As Sea Level Rises13 million U.S. coastal residents are expected to be displaced by 2100 due to sea level rise. Researchers are starting to predict where they’ll go.2020
Florida Keys Deliver a Hard Message: As Seas Rise, Some Places Can’t Be SavedOfficials in the Florida Keys announced what many coastal governments nationwide have long feared, but few have been willing to admit: As seas rise and flooding gets worse, not everyone can be saved. And in some places, it doesn’t even make sense to try.2019
82 Days Underwater: The Tide Is High, but They’re Holding OnA brutal “king tides” season made worse by climate change has flooded the streets of a Florida Keys community for nearly three months.2019
Amid flooding and rising sea levels, residents of one barrier island wonder if it’s time to retreatOcracoke Island, NC has been closed to visitors ever since Hurricane Dorian hit last September. And long-time residents are questioning whether and how long this barrier island can survive in the face of threats from extreme weather and rising sea levels. And if it can’t, why rebuild?2019
Wild Weather and Climate Change: Scientists Are Unraveling the LinksOne of the trickiest aspects of climate science is figuring out if a particular heat wave, flood, or drought was made more likely or severe by climate change. But researchers are getting far better at untangling the relationship between extreme weather and global warming.2017
When Rising Seas Transform Risk into CertaintyAlong parts of the East Coast, the entire system of insuring coastal property is beginning to break down.2017
Georgia island confronts 'blue sky' floodsSea-level rise poses daunting ecological and economic challenges to historic Sapelo Island.2017
Westernmost, low-lying region of Louisiana coast on track to drown under sea level riseWithout major efforts to rebuild Louisiana's wetlands, which serve as bulwarks against waves and rising seas, the state's coast has little chance of withstanding the accelerating rate of sea level rise, a new study concludes.2017
Atlantic City and Miami Beach: two takes on tackling the rising waters Sea level rise is making floods more common and as the New Jersey resort braces for the next Sandy, the well-heeled Florida city is throwing money at the problem.2017
Why the U.S. East Coast could be a major ‘hotspot’ for rising seas“[N]ew research [by] scientists us[ing] a high powered climate change model . . . that simulates the ocean, the atmosphere and the cycling of carbon throughout the Earth system . . . found that at high emissions scenarios similar to current rates, the Atlantic sea levels rise considerably faster than the Pacific, with particularly noteworthy impacts for the U.S. East Coast.
“The reason for the difference . . . water that sinks beneath the surface in the Atlantic will generally make it back to the surface again in 200 to 300 years, versus about three times as long for the Pacific . . . leading to warmer water pooling below the surface and, ultimately, greater warming overall. Warm water expands, and that’s the cause of the sea level rise expected in the study.”
2016
Abrupt Sea Level Rise Looms as Increasingly Realistic ThreatNinety-nine percent of the planet's freshwater ice is locked up in the Antarctic and Greenland ice caps. Now, a growing number of studies are raising the possibility that as those ice sheets melt, sea levels could rise by six feet this century, and far higher in the next, flooding many of the world's populated coastal areas. 2016
‘Ghost Forests’ Appear as Rising Seas Kill TreesBare trunks of dead coastal forests are being discovered up and down the mid-Atlantic coastline, killed by the advance of rising seas. The “ghost forests,” as scientists call them, offer eerie evidence of some of the world’s fastest rates of sea level rise. Preliminary findings from an analysis by Virginia Institute of Marine Science (VIMS) scientists suggests 100,000 acres of coastal forest may have died off around the edges of the Chesapeake Bay since the 1850s. Much of the dead forest has now been replaced by marshland, while former marsh areas are now open water. Overall, the changes are diminishing the ability of plants in the region to fight global warming by absorbing carbon dioxide.2016
Ghost Forests: How Rising Seas Are Killing Southern U.S. WoodlandsA steady increase in sea levels is pushing saltwater into U.S. wetlands, killing trees from Florida to as far north as New Jersey. But with sea level projected to rise by as much as six feet this century, the destruction of coastal forests is expected to become a worsening problem worldwide. 2016
What Climate Change Means for GeorgiaThis EPA factsheet provides an overview of expected climate change impacts on Georgia. These include: rising seas and retreating shorelines; coastal storms, homes and infrastructure; water resources, flooding, and drought; agriculture and forest resources; and human health. 2016
Multi-year Arctic ice continues to shrinkThis NASA video tracks the dramatic loss of Artic sea ice area from 1978 to 2014. 2015
Sea Level Rise to Put the “Squeeze” on Coastal GeorgiaThis article describes the effect sea level rise will likely have on the Georgia coast and what coastal communities can do to mitigate these effects. 2012