1 / 15

228 Ra-derived ocean mixing and nutrient fluxes in the Cape Basin

D357. 228 Ra-derived ocean mixing and nutrient fluxes in the Cape Basin. Kz. Yu- Te (Alan ) Hsieh 10-09-2012. Kx. Data: Malcolm Woodward. Study regions: Cape Basin ( UK- GEOTRACES D357). Oct-Nov 2010. Sea surface temperature ( o C ). Salinity ( o / oo ).

ilya
Télécharger la présentation

228 Ra-derived ocean mixing and nutrient fluxes in the Cape Basin

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. D357 228Ra-derived ocean mixingand nutrient fluxes in the Cape Basin Kz Yu-Te (Alan) Hsieh 10-09-2012 Kx Data: Malcolm Woodward

  2. Study regions: Cape Basin (UK-GEOTRACES D357) Oct-Nov 2010 Sea surface temperature (oC) Salinity (o/oo)

  3. Uranium- Thorium-series isotopes

  4. Radium-228 as a tracer for ocean mixing • One dimensional diffusion model • assumptions: • 228Ra at steady-state • One dimensional input • No particulate removal 228Ra decay 228Ra 232Th 228Ra 228Ra Horizontal mixing (Kx) T1/2: 5.75 years decay Vertical mixing (Kz)

  5. Results: 226Ra and 228Ra profiles Methods: MC-ICP-MS (Hsieh and Henderson, 2011; Foster et al., 2004) (1976)

  6. D357

  7. (A) stn2 This study Hanfland, 2002 Stn4.5 A (B) SST (Matano and Beier, 2003)

  8. ACL stn2 stn0 stn1 stn4.5 stn3 stn4 AAIW NADW AABW

  9. Coast High Ra, S and T Eddy High Ra, S and T Open Ocean High Ra, S and T From Indian Ocean coast

  10. Horizontal mixing (Kx) in the surface ocean Kx(107 cm2 s-1) Kx = 3.8 Kx = 1.3

  11. Vertical mixing (Kz) in the surface ocean Kz (cm2 s-1) 0.9 ± 0.2 1.3 ± 0.3 (ACL eddy) 2.1 ± 0.4 Average Kz in the surface South Atlantic (based on tritium profiles): Kz = 1.5 cm2 S-1, Li et al. (1984)

  12. Vertical nutrient fluxes Nitrate 228Ra decay (dNO3-/dz) Vertical mixing (Kz) Fnitrate = Kz (dNO3-/dz) Fick’s first law

  13. Nutrient profiles and vertical fluxes (ACL eddy) N flux (mmol m-2 d-1) 0.50 ± 0.12 0.46 ± 0.13 0.51 ± 0.13

  14. Convert nitrogen fluxes to carbon fluxes (ACL)

  15. Conclusions 1. 228Ra-derived horizontal and vertical ocean mixing coefficients in the surface Cape Basin: Kx = 3.8 ± 0.8 (107 cm2 d-1) and Kz = 0.9 ± 0.2 to 2.1 ± 0.4 (cm2 d-1) 2. 228Ra-derived vertical nutrient and carbon fluxes show comparable results with other techniques in the Cape Basin (N: 0.46 – 0.51 mmol m-2 d-1; C: 3.1- 3.3 mmol m-2 d-1). 3. Agulhas current leakage enhances ocean mixing in the Cape Basin but not nutrient inputs.

More Related