Radium-228-derived ocean mixing and trace element inputs in the South Atlantic

• Published in: Biogeosciences
• Main Authors: Y.-T. Hsieh, W. Geibert, E. M. S. Woodward, N. J. Wyatt, M. C. Lohan, E. P. Achterberg, G. M. Henderson
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2021
• Subjects: Ecology; QH540-549.5; Life; QH501-531; Geology; QE1-996.5; Southern Ocean; Argentine
• Online Access: https://doi.org/10.5194/bg-18-1645-2021; https://doaj.org/article/66dfa5d56e934313acbc0755aa0af532

Trace elements (TEs) play important roles as micronutrients in modulating marine productivity in the global ocean. The South Atlantic around 40 ∘ S is a prominent region of high productivity and a transition zone between the nitrate-depleted subtropical gyre and the iron-limited Southern Ocean. However, the sources and fluxes of trace elements to this region remain unclear. In this study, the distribution of the naturally occurring radioisotope 228 Ra in the water column of the South Atlantic (Cape Basin and Argentine Basin) has been investigated along a 40 ∘ S zonal transect to estimate ocean mixing and trace element supply to the surface ocean. Ra-228 profiles have been used to determine the horizontal and vertical mixing rates in the near-surface open ocean. In the Argentine Basin, horizontal mixing from the continental shelf to the open ocean shows an eddy diffusion of <math xmlns="http://www.w3.org/1998/Math/MathML" id="M4" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi>K</mi><mi>x</mi></msub><mo>=</mo><mn mathvariant="normal">1.8</mn><mo>±</mo><mn mathvariant="normal">1.4</mn></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="69pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="5b3549c8a00c9456492d0ff0f458c984"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-18-1645-2021-ie00001.svg" width="69pt" height="12pt" src="bg-18-1645-2021-ie00001.png"/></svg:svg> (10 6 cm 2 s −1 ) and an integrated advection velocity <math xmlns="http://www.w3.org/1998/Math/MathML" id="M8" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>w</mi><mo>=</mo><mn mathvariant="normal">0.6</mn><mo>±</mo><mn mathvariant="normal">0.3</mn></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="65pt" height="10pt" class="svg-formula" ...