Application of an inverse method to interpret 231Pa/230Th observations from marine sediments
Figure S2: Posterior uncertainties for the horizontal circulation between 2000 and 3000 m (solution with prior LNM = 3000). (411.1Kb)
Figure S3: Posterior uncertainties for the horizontal circulation between 4000 and 5000 m (solution with prior LNM = 3000). (400.9Kb)
Figure S4: Partition coefficient at 12 stations in the Atlantic Ocean computed from paired measurements of particulate and total 231Pa activity and the geographic locations of stations with paired measurements of particulate and total 231Pa activity and measurements of particulate 230Th activity. (479.4Kb)
Figure S5: A plot of measured [Pa] against the objectively mapped [Pa] at the same data locations. (97.58Kb)
Figure S6: Analysis of reconstructed 231Pa from Holocene, LGM, and H1 sediments using an extended data set that includes the 231Pa/230Th record from Negre et al. . (115.2Kb)
Bradtmiller, Louisa I.
McManus, Jerry F.
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Records of 231Pa/230Th from Atlantic sediments have been interpreted to reflect changes in ocean circulation during the geologic past. Such interpretations should be tested with due regard to the limited spatial coverage of 231Pa/230Th data and the uncertainties in our current understanding of the behavior of both nuclides in the ocean. Here an inverse method is used to evaluate the information contained in 231Pa/230Th compilations for the Holocene, Last Glacial Maximum (LGM), and Heinrich Event 1 (H1). An estimate of the abyssal circulation in the modern Atlantic Ocean is obtained by combining hydrographic observations and dynamical constraints. Then sediment 231Pa/230Th data for each time interval are combined with an advection-scavenging model in order to determine their (in)consistency with the modern circulation estimate. We find that the majority of sediment 231Pa/230Th data for the Holocene, LGM, or H1 can be brought into consistency with the modern circulation if plausible assumptions are made about the large-scale distribution of 231Pa and about model uncertainties. Moreover, the adjustments in the data needed to reach compatibility with a hypothetical state of no flow (no advection) are positively biased for each time interval, suggesting that the 231Pa/230Th data (including that for H1) are more consistent with a persistence of some circulation than with no circulation. Our study does not imply that earlier claims of a circulation change during the LGM or H1 are inaccurate, but that these claims cannot be given a rigorous basis given the current uncertainties involved in the analysis of the 231Pa/230Th data.
Author Posting. © American Geophysical Union, 2011. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 26 (2011): PA1212, doi:10.1029/2010PA002022.
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