Rising seas weaken an offshore sediment lifeline to coastal wetlands

Abstract Coastal wetlands require sediment to keep pace with rising seas, but sea-level rise may itself weaken their sediment supply. We combine satellite observations, physical sensitivity experiments, and global analyses to reveal this overlooked mechanism. Along coastal Louisiana, winter suspended sediment concentrations declined by 27–58% from 2003 to 2024, coinciding with rising water levels and weakening wave-driven seabed stress, despite stable riverine sediment loading and wave forcing. Sensitivity experiments indicate that deepening alone could reduce sediment-resuspension potential by 31–63% by 2100. Globally, 79% of analyzed coastal waters between 66°S and 66°N exhibit strong wave–sediment coupling. Under SSP5-8.5, projected deepening reduces wave-driven bottom stress near wetlands by 17–23% by 2100. Rising seas can thus increase sediment demand while weakening potential offshore sediment supply.