US EPA

2710441 

Journal Article 

A depth profile of uranium-236 in the Atlantic Ocean 

Christl, M; Lachner, J; Vockenhuber, C; Lechtenfeld, O; Stimac, I; van Der Loeff, MR; Synal, HA 

2012 

Yes 

Geochimica et Cosmochimica Acta
ISSN: 0016-7037 

77 

98-107 

10.1016/j.gca.2011.11.009 

WOS:000299010400007 

In this study the first two oceanic depth profiles of U-236 sampled in the western equatorial Atlantic Ocean are presented. The measured U-236/U-238 ratios decrease from about 10(-9) at the surface down to about 10(-10). Even the lowest ratios measured below 4000 m depth are more than three orders of magnitude above the estimated natural U-236/U-238 level for the pre-anthropogenic ocean. This clearly indicates that anthropogenic U-236 already has reached the deep Atlantic Ocean. Three different conceptual models are applied to identify the relevant processes capable of transporting significant amounts of U-236 from the surface into the deep ocean. While the vertical transport of particulate U is excluded as a significant source, box model calculations suggest that North Atlantic Deep Water production with some minor contribution of U-236 from nuclear reprocessing as the most likely source for U-236 in the deep western equatorial Atlantic Ocean. Our results show that U-236 has a large potential as a new, conservative, and transient tracer in Oceanography. (C) 2011 Elsevier Ltd. All rights reserved.