High precision 230Th and 232Th in the Norwegian Sea and Denmark by thermal ionization mass spectrometry

S. B. Moran, J. A. Hoff, K. O. Buesseler, R. L. Edwards

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Seawater samples (1–2 liters) were collected from the Norwegian Sea and Denmark Strait and analyzed for 230Th and 232Th using highly sensitive thermal ionization mass spectrometry (TIMS). Depth profiles of dissolved 230Th and 232Th are characterized by surface water minima (<1 fg/kg, <5 pg/kg), subsurface maxima (12 fg/kg, 134 pg/kg), and intermediate concentrations that progressively decrease toward the bottom (∼5 fg/kg, ∼17 pg/kg), respectively. The lack of an increase in 230Th with depth is suggested to result from the short ventilation age of Norwegian Sea Deep Water combined with enhanced scavenging near the basin margins. The 230Th maximum is attributed to advection of high 230Th in the Arctic Intermediate Water, whereas the 232Th maximum may be related to a particulate source. The low dissolved 230Th and 232Th concentrations observed in the NADW formation regions implies a minor advective export of these long‐lived Th tracers to the North Atlantic.

Original languageEnglish (US)
Pages (from-to)2589-2592
Number of pages4
JournalGeophysical Research Letters
Issue number19
StatePublished - Oct 1 1995


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