From Buried Bayous to Global Biogeochemical Fluxes: Submarine Groundwater Discharge in North America's Largest Delta.

Submarine groundwater discharge (SGD) associated with large river deltas stands is an understudied, but potentially important, pathway by which water and solutes flow from the continents to the oceans. Deltas are well known to be important loci for nutrient regeneration, carbon sequestration and authigenic mineral formation, and subsurface fluxes between marine and freshwaters in these systems could be geochemically important globally. This talk will examine the topic of deltaic SGD, its regional and global implications, and use case studies from ongoing work in the Mississippi River Delta (MRD). Recent results indicate that SGD fluxes in the MRD averages 1,000 m³ s^-1, and can reach 5,000 m³ s^-1; making this flux one the 25 largest pathways for water transport in North America. Flow appears to be driven by the stage differential between the Mississippi River (MR) and its surrounding wetlands, and fluctuates seasonally with stage variations in the MR. Water appears to pass through paleochannels, relict crevasse splays, and other buried semi-permeable bodies. Hydrological fluxes may be amplified by the network of levees along the MR that elevate river stages during floods. Given that subsurface flow can undermine levees, deltaic SGD may be an under-recognized component of coastal sustainability, which could accelerate in importance as additional flood control structures are constructed to cope with rising base levels during the Anthropocene.

Submarine groundwater discharge (SGD) associated with large river deltas stands is an understudied, but potentially important, pathway by which water and solutes flow from the continents to the oceans. Deltas are well known to be important loci for nutrient regeneration, carbon sequestration and authigenic mineral formation, and subsurface fluxes between marine and freshwaters in these systems could be geochemically important globally. This talk will examine the topic of deltaic SGD, its regional and global implications, and use case studies from ongoing work in the Mississippi River Delta (MRD). Recent results indicate that SGD fluxes in the MRD averages 1,000 m³ s^-1, and can reach 5,000 m³ s^-1; making this flux one the 25 largest pathways for water transport in North America. Flow appears to be driven by the stage differential between the Mississippi River (MR) and its surrounding wetlands, and fluctuates seasonally with stage variations in the MR. Water appears to pass through paleochannels, relict crevasse splays, and other buried semi-permeable bodies. Hydrological fluxes may be amplified by the network of levees along the MR that elevate river stages during floods. Given that subsurface flow can undermine levees, deltaic SGD may be an under-recognized component of coastal sustainability, which could accelerate in importance as additional flood control structures are constructed to cope with rising base levels during the Anthropocene.