Gulf Coast demise: The reversal from Late Holocene growth and stability to rapid inundation and erosion caused by accelerated sea-level rise and diminished sediment supply

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Acceleration of sea-level rise, coupled with natural and human-induced reductions in sediment supply, has resulted in unprecedented change across the Gulf Coast (southern United States). Recent projections indicate widespread inundation of existing wetlands by the year 2050, including most of the Mississippi Delta, the Everglades, and the Louisiana Chenier Plain. In addition, barrier islands, peninsulas, and mainland beaches are experiencing rapid erosion. These changes are a stark reversal from the stability and growth of these coastal settings during the last 4000 yr. Indeed, current rates of change outpace those of the Early Holocene, when sea level was rising at about the same rate as today, but sediment supply to the coast was not impeded by the alteration of sediment supply and dispersal systems. Unfortunately, Gulf Coast states have been slow to recognize the magnitude of the problem, but there is still time to slow the rate of change and reduce its impacts. GRAPHICAL ABSTRACT Graphical abstract titled “Coastal Settings of the Gulf Coast (USA)” illustrating changes in relative sea-level rise over the past 10,000 years and projected future trends. The left side shows paleo records (black line) indicating rapid sea-level rise after the last glacial period, with rates decreasing from about 4.2 mm/yr (episodic rise) to 1.4 mm/yr and then 0.5 mm/yr during the Late Holocene. This period is labeled “Late Holocene Growth and Stability,” associated with slow sea-level rise and high sediment supply. A vertical red line marked “Reversal” around 1860 separates the paleo record from modern observations. On the right, tide-gauge records (blue) and satellite records (red) show accelerating sea-level rise from 1860 to 2022, transitioning from approximately −30 cm to above 0 cm. A dotted purple line represents IPCC projections through 2050, reaching roughly +30 cm. The modern period is labeled “Rapid Inundation and Erosion,” associated with rapid sea-level rise and low sediment supply. Axes show age in calibrated years before present on the left, modern years on the right, depth below mean sea level (mbsl), and relative sea-level change in centimeters. A legend identifies paleo records, tide-gauge records, satellite records, and IPCC projections.