Th-230 and Pa-231 on GEOTRACES GA03, the US GEOTRACES North Atlantic transect, and implications for modern and paleoceanographic chemical fluxes
Hayes, Christopher T.
Anderson, Robert F.
Fleisher, Martin Q.
Robinson, Laura F.
Edwards, R. Lawrence
Moran, S. Bradley
MetadataShow full item record
The long-lived uranium decay products 230Th and 231Pa are widely used as quantitative tracers of adsorption to sinking particles (scavenging) in the ocean by exploiting the principles of radioactive disequilibria. Because of their preservation in the Pleistocene sediment record and through largely untested assumptions about their chemical behavior in the water column, the two radionuclides have also been used as proxies for a variety of chemical fluxes in the past ocean. This includes the vertical flux of particulate matter to the seafloor, the lateral flux of insoluble elements to continental margins (boundary scavenging), and the southward flux of water out of the deep North Atlantic. In a section of unprecedented vertical and zonal resolution, the distributions of 230Th and 231Pa across the North Atlantic shed light on the marine cycling of these radionuclides and further inform their use as tracers of chemical flux. Enhanced scavenging intensities are observed in benthic layers of resuspended sediments on the eastern and western margins and in a hydrothermal plume emanating from the Mid-Atlantic Ridge. Boundary scavenging is clearly expressed in the water column along a transect between Mauritania and Cape Verde which is used to quantify a bias in sediment fluxes calculated using 230Th-normalization and to demonstrate enhanced 231Pa removal from the deep North Atlantic by this mechanism. The influence of deep ocean ventilation that leads to the southward export of 231Pa is apparent. The 231Pa/230Th ratio, however, predominantly reflects spatial variability in scavenging intensity, complicating its applicability as a proxy for the Atlantic meridional overturning circulation.
Author Posting. © The Author(s), 2014. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 116 (2015): 29-41, doi:10.1016/j.dsr2.2014.07.007.
Showing items related by title, author, creator and subject.
Cellular elemental content of individual phytoplankton cells collected during US GEOTRACES North Atlantic Transect cruises in the Subtropical western and eastern North Atlantic Ocean during Oct and Nov, 2010 and Nov. 2011. Twining, Benjamin S. (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: firstname.lastname@example.org, 2017-06-21)Phytoplankton contribute significantly to global C cycling and serve as the base of ocean food webs. Phytoplankton require trace metals for growth and also mediate the vertical distributions of many metals in the ocean. ...
Size-fractionated major particle composition and concentrations from the US GEOTRACES North Atlantic Zonal Transect Lam, Phoebe J.; Ohnemus, Daniel C.; Auro, Maureen E. (Elsevier, 2014-11-18)The concentration and the major phase composition (particulate organic matter, CaCO3, opal, lithogenic matter, and iron and manganese oxyhydroxides) of marine particles is thought to determine the scavenging removal of ...
Ohnemus, Daniel C.; Lam, Phoebe J. (Elsevier, 2014-12-06)In this paper, we present, describe, and model the first size-fractionated (0.8–51 µm; >51 µm) water-column particulate trace metal results from the US GEOTRACES North Atlantic Zonal Transect in situ pumping survey, with ...