Dissolved Inorganic Carbon Transport in the Surface-Mixed Layer of the Louisiana Shelf in Northern Gulf of Mexico

Document Type

Article

Publication Date

11-1-2020

Abstract

Rivers and wetlands are a major source of terrestrial derived carbon for coastal ocean margins. This results in a net loss of terrestrial carbon into the shelf water and their subsequent transport to interior ocean basin. This study investigates the transport of dissolved inorganic carbon (DIC) in the surface-mixed layer of Louisiana Shelf in northern Gulf of Mexico (nGOM) adjacent to the Wax Lake Delta (WLD) and Barataria Bay (BB), which represent contrasting net land gain and net land loss areas in this region. DIC samples were collected, in conjunction with short-lived radium isotopes 224Ra (t1/2 = 3.66 days) and 223Ra (t1/2 = 11.43 days) samples during June and September 2019, to quantify shelf transport of DIC in the surface-mixed layer during period of high and low river flow, respectively. Radium distribution implied shelf mixing rates of 140–6,759 and 63–2,724 m2 s−1 for WLD and BB regions, respectively, with more than tenfold decrease in rates between the two seasons. Net shelf transport of DIC was found to be highest for the WLD region in June, highlighting the importance of freshwater discharge in exporting DIC. An upscaling of our study for the entire Louisiana Shelf indicates that 1.54–20.19 × 109 mol C d−1 transported in June 2019 and 0.34–8.12 × 109 mol C d−1 in the form of DIC was exported across the shallow region of the shelf during high and low river flow seasons, representing an important source of DIC to the NGOM.

Publication Source (Journal or Book title)

Journal of Geophysical Research Oceans

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