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Submarine groundwater discharge revealed by 228Ra distribution in the upper Atlantic Ocean

Nature Geoscience volume 1, pages 309–311 (2008)Cite this article

Abstract

Submarine groundwater discharge is defined as any flow of water at continental margins from the seabed to the coastal ocean, regardless of fluid composition or driving force1. The flux of submarine groundwater discharge has been hypothesized to be a pathway for enriching coastal waters in nutrients, carbon and metals2. Here, we estimate the submarine groundwater flux from the inventory of 228Ra in the upper Atlantic Ocean, obtained by interpolating measurements at over 150 stations. Only 46% of the loss in 228Ra from radioactive decay is replenished by input from dust, rivers and coastal sediments. We infer that the remainder must come from submarine groundwater discharge. Using estimates of 228Ra concentrations in submarine groundwater discharge, we arrive at a total flux from submarine groundwater discharge of 2–4×1013 m3 yr−1, between 80 and 160% of the amount of freshwater entering the Atlantic Ocean from rivers. Submarine groundwater discharge is not a freshwater flux, but a flux of terrestrial and sea water that has penetrated permeable coastal sediments. Our assessment of the volume of submarine groundwater discharge confirms that this flux represents an important vehicle for the delivery of nutrients, carbon and metal to the ocean.

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Figure 1: Inventory of 228Ra (×1010 atoms m−2) in the upper 1,000 m of the Atlantic Ocean.
Figure 2: Distribution of 228Ra in groundwater samples from throughout the Atlantic coastline.

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Acknowledgements

We thank the many scientists who have contributed published and unpublished groundwater radium data to this project. This research was supported by NSF.

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Authors and Affiliations

  1. Department of Geological Sciences, University of South Carolina, Columbia, South Carolina 29208, USA

    Willard S. Moore

  2. AOS Program, Princeton University, Princeton, New Jersey 08544, USA

    Jorge L. Sarmiento & Robert M. Key

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  1. Willard S. Moore
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  2. Jorge L. Sarmiento
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  3. Robert M. Key
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All authors contributed equally to this work.

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Correspondence to Willard S. Moore.

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Moore, W., Sarmiento, J. & Key, R. Submarine groundwater discharge revealed by 228Ra distribution in the upper Atlantic Ocean. Nature Geosci 1, 309–311 (2008). https://doi.org/10.1038/ngeo183

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