Kwon Eun Young

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Kwon
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Eun Young
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  • Article
    Global estimate of submarine groundwater discharge based on an observationally constrained radium isotope model
    (John Wiley & Sons, 2014-12-03) Kwon, Eun Young ; Kim, Guebuem ; Primeau, Francois W. ; Moore, Willard S. ; Cho, Hyung-Mi ; DeVries, Timothy ; Sarmiento, Jorge L. ; Charette, Matthew A. ; Cho, Yang-Ki
    Along the continental margins, rivers and submarine groundwater supply nutrients, trace elements, and radionuclides to the coastal ocean, supporting coastal ecosystems and, increasingly, causing harmful algal blooms and eutrophication. While the global magnitude of gauged riverine water discharge is well known, the magnitude of submarine groundwater discharge (SGD) is poorly constrained. Using an inverse model combined with a global compilation of 228Ra observations, we show that the SGD integrated over the Atlantic and Indo-Pacific Oceans between 60°S and 70°N is (12 ± 3) × 1013 m3 yr−1, which is 3 to 4 times greater than the freshwater fluxes into the oceans by rivers. Unlike the rivers, where more than half of the total flux is discharged into the Atlantic, about 70% of SGD flows into the Indo-Pacific Oceans. We suggest that SGD is the dominant pathway for dissolved terrestrial materials to the global ocean, and this necessitates revisions for the budgets of chemical elements including carbon.
  • Article
    Coastal ocean and shelf-sea biogeochemical cycling of trace elements and isotopes : lessons learned from GEOTRACES
    (The Royal Society, 2016-10-17) Charette, Matthew A. ; Lam, Phoebe J. ; Lohan, Maeve C. ; Kwon, Eun Young ; Hatje, Vanessa ; Jeandel, Catherine ; Shiller, Alan M. ; Cutter, Gregory A. ; Thomas, Alex ; Boyd, Philip ; Homoky, William B. ; Milne, Angela ; Thomas, Helmuth ; Andersson, Per S. ; Porcelli, Don ; Tanaka, Takahiro ; Geibert, Walter ; Dehairs, Frank ; Garcia-Orellana, Jordi
    Continental shelves and shelf seas play a central role in the global carbon cycle. However, their importance with respect to trace element and isotope (TEI) inputs to ocean basins is less well understood. Here, we present major findings on shelf TEI biogeochemistry from the GEOTRACES programme as well as a proof of concept for a new method to estimate shelf TEI fluxes. The case studies focus on advances in our understanding of TEI cycling in the Arctic, transformations within a major river estuary (Amazon), shelf sediment micronutrient fluxes and basin-scale estimates of submarine groundwater discharge. The proposed shelf flux tracer is 228-radium (T1/2 = 5.75 yr), which is continuously supplied to the shelf from coastal aquifers, sediment porewater exchange and rivers. Model-derived shelf 228Ra fluxes are combined with TEI/ 228Ra ratios to quantify ocean TEI fluxes from the western North Atlantic margin. The results from this new approach agree well with previous estimates for shelf Co, Fe, Mn and Zn inputs and exceed published estimates of atmospheric deposition by factors of approximately 3–23. Lastly, recommendations are made for additional GEOTRACES process studies and coastal margin-focused section cruises that will help refine the model and provide better insight on the mechanisms driving shelf-derived TEI fluxes to the ocean.
  • Article
    Enriched regions of 228Ra along the U.S. GEOTRACES Pacific Meridional Transect (GP15)
    (American Geophysical Union, 2024-03-07) Moore, Willard S. ; Charette, Matthew A. ; Henderson, Paul B. ; Hammond, Douglas E. ; Kemnitz, Nathaniel ; Le Roy, Emilie ; Kwon, Eun Young ; Hult, Mikael
    The half-life of 228Ra (5.7 years) aligns well with near-surface and near-bottom ocean mixing timescales. Because 228Ra is sourced from sediments, regions of enhanced activity represent water that has recently interacted with sediments on the continental margin or seabed. The GP15 meridional transect from Alaska to Tahiti along152°W encountered several regions in the upper ocean where 228Ra was enriched. These enrichments follow surface and subsurface ocean current patterns and pair with earlier measurements of 228Ra and transient radionuclides to reveal the origins of these enriched regions. An enriched region at Alaska margin stations 1–3 was sourced locally but did not extend to the Alaskan trench at station 4. A large shallow region between 47° and 32°N. was sourced from the west by the North Pacific Current; another shallow enriched region between 11° and 5° N was also sourced from the west by the North Equatorial Countercurrent. Subsurface enrichments (100–400 m) between 18 and 47°N were associated with Central Mode Water and North Pacific Intermediate Water. The 228Ra activities in the upper Pacific were six times lower than activities in the Atlantic. In deep waters the primary enrichment was 27°–47°N. Two stations (32° and 37°N) were especially enriched, having near-bottom inventories several times greater than other stations. With these two exceptions the remaining Pacific stations exhibited averaged inventories lower than those in the Atlantic. There was one region of enriched 223Ra (half-life = 11 days) above the Puna Ridge near Hawaii.