Reconstructing “background” Rates of sea-level rise as a tool for forecasting coastal wetland loss, Mississippi Delta

Coastal marshes are threatened by relative sea-level (RSL) rise, yet recent studies predict marsh survival even under the high rates of RSL rise expected later in this century. However, because these studies are mostly based on short-term records, uncertainty persists about the longer-term vulnerability of coastal marshes. We present an 8500-year-long marsh record from the Mississippi Delta, showing that at rates of RSL rise exceeding 6 to 9 mm year−1, marsh conversion into open water occurs in about 50 years. At rates of RSL rise exceeding ~3 mm year−1, marsh drowning occurs within a few centuries. Because present-day rates of global sea-level rise already surpass this rate, submergence of the remaining ~15,000 km2 of marshland in coastal Louisiana is probably inevitable. RSL-driven tipping points for marsh drowning vary geographically, and those for the Mississippi Delta may be lower than elsewhere. Nevertheless, our findings highlight the need for consideration of longer time windows in determining the vulnerability of coastal marshes worldwide.

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Impact of Barrier Breaching on Wetland Ecosystems under the Influence of Storm Surge, Sea-Level Rise and Freshwater Discharge

Wetlands ◽

10.1007/s13157-019-01219-x ◽

2019 ◽

Vol 40 (4) ◽

pp. 771-785 ◽

Cited By ~ 1

Author(s):

Xiaorong Li ◽

Nicoletta Leonardi ◽

Andrew J. Plater

Keyword(s):

Climate Change ◽

Sea Level Rise ◽

Sea Level ◽

River Discharge ◽

Coastal Wetland ◽

Storm Surges ◽

Wetland Ecology ◽

Barrier Beach ◽

Wetland Ecosystems ◽

Wetland Habitats

Abstract Coastal wetland ecosystems and biodiversity are susceptible to changes in salinity brought about by the local effects of climate change, meteorological extremes, coastal evolution and human intervention. This study investigates changes in the salinity of surface water and the associated impacts on back-barrier wetlands as a result of breaching of a barrier beach and under the compound action of different surge heights, accelerated sea-level rise (SLR), river discharge and rainfall. We show that barrier breaching can have significant effects in terms of vegetation die-back even without the occurrence of large storm surges or in the absence of SLR, and that rainfall alone is unlikely to be sufficient to mitigate increased salinity due to direct tidal flushing. Results demonstrate that an increase in sea level corresponding to the RCP8.5 scenario for year 2100 causes a greater impact in terms of reedbed loss than storm surges up to 2 m with no SLR. In mitigation of the consequent changes in wetland ecology, regulation of relatively small and continuous river discharge can be regarded as a strategy for the management of coastal back-barrier wetland habitats and for the maintenance of brackish ecosystems. As such, this study provides a tool for scoping the potential impacts of storms, climate change and alternative management strategies on existing wetland habitats and species.

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A Dutch geoscience perspective on the Katrina disaster

Netherlands Journal of Geosciences – Geologie en Mijnbouw ◽

10.1017/s0016774600077878 ◽

2007 ◽

Vol 86 (3) ◽

pp. 307-315 ◽

Cited By ~ 5

Author(s):

T.E. Törnqvist

Keyword(s):

Sea Level ◽

Mississippi Delta ◽

Gulf Coast ◽

Wetland Loss ◽

Decision Makers ◽

Long Term Stability ◽

Anthropogenic Processes ◽

The Times ◽

Precarious Situation

AbstractA combination of geological and anthropogenic processes have rendered the U.S. Gulf Coast in general – and the Mississippi Delta in particular – extremely sensitive to coastal hazard. Thus, the Katrina disaster was not a question of ‘if’ but of ‘when’. This contribution outlines the geo-environmental context of the Mississippi Delta that evolved during the 20th century and set the stage for Hurricane Katrina’s devastation. This includes a brief discussion of the processes responsible for coastal erosion and wetland loss, the proposed measures to combat these problems, and the policy decisions (or, rather, the lack thereof) made so far. A connection is made with the 1953 storm surge that devastated the southwestern Netherlands and had a profound impact on Dutch science and engineering by providing the impetus for the widely known and highly praised Delta Plan, as well as for unprecedented studies of Holocene sea-level change. Whether a similar route will be followed for the Gulf Coast is primarily dependent on the amount of political will. Results are presented of recent studies of crustal movements in the Mississippi Delta that show surprising long-term stability of the Pleistocene basement, evidence that could prove critical for decision makers with regard to the rebuilding process. Finally, the neglect of the precarious situation along the Gulf Coast by the federal government is viewed as a possible metaphor for current U.S. policies with respect to science in general, and to global warming in particular.“Land that sits below sea level. Levees and dams that stand against nature’s fury. Countryside that sinks more every year. New Orleans? No. Holland: a nation whose flood protections makes ours look primitive and slapdash”John McQuaid, The Times-Picayune, November 13, 2005

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Beyond just sea-level rise: considering macroclimatic drivers within coastal wetland vulnerability assessments to climate change

Global Change Biology ◽

10.1111/gcb.13084 ◽

2015 ◽

Vol 22 (1) ◽

pp. 1-11 ◽

Cited By ~ 126

Author(s):

Michael J. Osland ◽

Nicholas M. Enwright ◽

Richard H. Day ◽

Christopher A. Gabler ◽

Camille L. Stagg ◽

...

Keyword(s):

Climate Change ◽

Sea Level Rise ◽

Sea Level ◽

Coastal Wetland ◽

Vulnerability Assessments

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Modelling Actual and Future Seawater Intrusion in the Variconi Coastal Wetland (Italy) Due to Climate and Landscape Changes

Water ◽

10.3390/w11071502 ◽

2019 ◽

Vol 11 (7) ◽

pp. 1502 ◽

Cited By ~ 8

Author(s):

Mastrocicco ◽

Busico ◽

Colombani ◽

Vigliotti ◽

Ruberti

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Seawater Intrusion ◽

Coastal Wetland ◽

Coastal Lagoons ◽

Three Dimensional ◽

Climate Data ◽

Climate Change Effects ◽

Modelling Framework ◽

Groundwater Overexploitation

Coastal freshwater resources are commonly under high risk of being contaminated from seawater. The main processes that affect seawater intrusion are groundwater overexploitation, land use change, and climate change effects. In this context coastal lagoons represent the more sensitive environments prone to seawater intrusion. Numerical modelling is a useful tool to understand and predict seawater intrusion. In this study, a three-dimensional SEAWAT model is employed to simulate the seawater intrusion to coastal aquifers of Variconi Oasis (Italy). The present simulation was divided into a calibration and a validation model, then the model was used to predict the salinization trend up to 2050. Results show the role of the sea in salinizing the beach front, while the retrodunal environment is characterized by transitional environments. Future seawater intrusion scenarios considering only climate data showed no significative differences in respect to the actual situation. The same happens considering also a low sea level rise prediction. On the contrary, the worst scenario (high sea level rise prediction), depicts a quite different situation, with a saline intrusion in the Variconi oasis that will severely affect the fragile transitional ecosystem. This modelling framework can be used to quantify the effects of climate changes in similar coastal environments.

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