TY - JOUR
T1 - Distribution of U-236 in the US GEOTRACES Eastern Pacific Zonal Transect and its use as a water mass tracer
AU - Villa-Alfageme, M.
AU - Chamizo, E.
AU - Kenna, T. C.
AU - López-Lora, M.
AU - Casacuberta, N.
AU - Chang, C.
AU - Masqué, P.
AU - Christl, M.
PY - 2019/7/5
Y1 - 2019/7/5
N2 - We report dissolved concentrations of the long-lived radioisotope U-236 measured in the water column along the 2013 US GEOTRACES Eastern Pacific Zonal Transect (GP16). This transect followed a 10-15 degrees S line from Manta, Ecuador, to Papeete, Haiti, French Polynesia, crossing the southern East Pacific Rise, intercepting one of the largest hydrothermal plumes as well as a productivity gradient, which includes the upwelling zone and associated low oxygen waters offshore from Peru and the oligotrophic sub-tropical gyre. Accelerator Mass Spectrometry was used to measure dissolved seawater U-236 concentrations as low as 1 x 10(3) atom kg(-1), which are among the lowest levels reported to date. Differences in upper water column U-236 distributions from east to west are a result of variable contributions from different surface and intermediate waters encountered along the transect.The distribution of U-236, both in depth and geographically, provides complementary information to that obtained from Delta C-14 and helium isotopes, demonstrating that U-236 concentrations are diagnostic in the identification of and contributions from the different deep and bottom water masses encountered along the EPZT (Jenkins a al., 2017). For example, we observe minimum U-236 concentrations along the EPZT between 2000 and 3000 m that are consistent with contributions attributed to Pacific Deep Water. We also observe increases in U-236 below 3000 m at the eastern and western termini of the EPZT. This is consistent with contributions associated with Antarctic Bottom Water and Lower Circumpolar Deep Water. Our results indicate that U-236 may be used in conjunction with Delta C-14 and He-3 isotopes as an additional tool with which to identify and resolve contributions from different water masses in the Pacific Ocean.This article is part of a special issue entitled: "Cycles of trace elements and isotopes in the ocean - GEOTRACES and beyond" - edited by Tim M. Conway, Tristan Homer, Yves Plancherel, and Aridane G. Gonzalez.
AB - We report dissolved concentrations of the long-lived radioisotope U-236 measured in the water column along the 2013 US GEOTRACES Eastern Pacific Zonal Transect (GP16). This transect followed a 10-15 degrees S line from Manta, Ecuador, to Papeete, Haiti, French Polynesia, crossing the southern East Pacific Rise, intercepting one of the largest hydrothermal plumes as well as a productivity gradient, which includes the upwelling zone and associated low oxygen waters offshore from Peru and the oligotrophic sub-tropical gyre. Accelerator Mass Spectrometry was used to measure dissolved seawater U-236 concentrations as low as 1 x 10(3) atom kg(-1), which are among the lowest levels reported to date. Differences in upper water column U-236 distributions from east to west are a result of variable contributions from different surface and intermediate waters encountered along the transect.The distribution of U-236, both in depth and geographically, provides complementary information to that obtained from Delta C-14 and helium isotopes, demonstrating that U-236 concentrations are diagnostic in the identification of and contributions from the different deep and bottom water masses encountered along the EPZT (Jenkins a al., 2017). For example, we observe minimum U-236 concentrations along the EPZT between 2000 and 3000 m that are consistent with contributions attributed to Pacific Deep Water. We also observe increases in U-236 below 3000 m at the eastern and western termini of the EPZT. This is consistent with contributions associated with Antarctic Bottom Water and Lower Circumpolar Deep Water. Our results indicate that U-236 may be used in conjunction with Delta C-14 and He-3 isotopes as an additional tool with which to identify and resolve contributions from different water masses in the Pacific Ocean.This article is part of a special issue entitled: "Cycles of trace elements and isotopes in the ocean - GEOTRACES and beyond" - edited by Tim M. Conway, Tristan Homer, Yves Plancherel, and Aridane G. Gonzalez.
KW - 236 U
KW - Accelerator Mass Spectrometry
KW - Deep waters
KW - Ocean circulation
KW - Pacific Ocean
UR - http://www.mendeley.com/research/distribution-236u-geotraces-eastern-pacific-zonal-transect-water-mass-tracer
U2 - 10.1016/j.chemgeo.2019.04.003
DO - 10.1016/j.chemgeo.2019.04.003
M3 - Article
SN - 0009-2541
VL - 517
SP - 44
EP - 57
JO - Chemical Geology
JF - Chemical Geology
ER -