What can paired measurements of Th isotope activity and particle concentration tell us about particle cycling in the ocean?
MetadataShow full item record
The ability of paired measurements of thorium isotope activity and particle concentration to constrain rate constants of sorption reactions and particle dynamics in the ocean is examined. This study is motivated by GEOTRACES and other sampling programs where Th and particle data are gathered in various oceanic environments. Our approach relies on inversions with a model of trace metal and particle cycling in the water column. First, the model is used to simulate vertical profiles of (i) the activity of three Th isotopes (228,230,234Th) in the dissolved phase, small suspended particles, and large sinking particles, and (ii) the concentration of small and large particles. The simulated profiles are then subsampled and corrupted with noise to generate a pseudo data set. These data are combined with the model with arbitrary values of rate constants of Th adsorption, Th desorption, particle sinking, particle remineralization, and particle (dis)aggregation in an effort to recover the actual values used to generate the data. Inversions are performed using a least-squares technique with varying assumptions about data noise, data sampling, and model errors. We find that accurate and precise recovery of rate parameters is possible when all data have a relative error of less than 20%, vertical sampling is dense enough to resolve activity and concentration gradients, and model errors are negligible. Estimating cycling rates from data with larger errors and (or) at locations where model assumptions are not tenable would remain challenging. On the other hand, the paired data set would improve significantly the relative precision of rate parameters compared to that of prior estimates (⩾100%), even with current data uncertainties and significant model errors. Based on these results, we advocate the joint measurement of all three Th isotopes, 228Ra, and particles collected by in situ filtration within GEOTRACES and other sampling programs targeted at the study of particle processes in the ocean.
Author Posting. © The Author(s), 2012. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Geochimica et Cosmochimica Acta 90 (2012):126–148, doi:10.1016/j.gca.2012.05.009.
Showing items related by title, author, creator and subject.
A new method for the estimation of sinking particle fluxes from measurements of the particle size distribution, average sinking velocity, and carbon content McDonnell, Andrew M. P.; Buesseler, Ken O. (Association for the Sciences of Limnology and Oceanography, 2012-05)We describe a new method for estimating sinking particulate carbon fluxes at high spatial and temporal resolutions from measurements of the particle concentration size distribution taken with an in situ camera system, in ...
Marchal, Olivier (2006-04-25)The 'Sandström theorem' as interpreted by Jeffreys (1925) is that in a flow maintained by a temperature difference, the pathline from the cold region to the warm region must lie below the return path. A formal demonstration ...
Sutherland, Kelly R.; Madin, Laurence P.; Stocker, Roman (2010-07)Salps are common in oceanic waters and have higher per individual filtration rates than any other zooplankton filter feeder. Though salps are centimeters in length, feeding via particle capture occurs on a fine, mucous ...