Open Access
Application of an inverse method to interpret 231 Pa/ 230 Th observations from marine sediments
Author(s) -
Burke Andrea,
Marchal Olivier,
Bradtmiller Louisa I.,
McManus Jerry F.,
François Roger
Publication year - 2011
Publication title -
paleoceanography
Language(s) - English
Resource type - Journals
eISSN - 1944-9186
pISSN - 0883-8305
DOI - 10.1029/2010pa002022
Subject(s) - ocean current , last glacial maximum , geology , hydrography , oceanography , climatology , advection , holocene , younger dryas , data assimilation , meteorology , geography , physics , thermodynamics
Records of 231 Pa/ 230 Th 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 231 Pa/ 230 Th 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 231 Pa/ 230 Th 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 231 Pa/ 230 Th 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 231 Pa/ 230 Th 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 231 Pa 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 231 Pa/ 230 Th 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 231 Pa/ 230 Th data.