Time series thorium-230 data reveal scavenging intensification over the last 15 years in the Arctic Ocean
Since 2007, thorium-230 (230Th) concentrations decreased significantly over the entire water column, particularly between 300 and 1,500 m in the Amundsen Basin, Arctic Ocean. As is often the case with 230Th, this decrease could reflect either ventilation of 230Th-depleted water or removal of this particle reactive tracer by scavenging intensification. Valk and co-workers (2020, see reference below) demonstrate that the later hypothesis is likely explaining 230Th-depletion in intermediate layers of the Amundsen basin. They also hypothesize that the scavenging intensification occurs at the “source” and during the transport of these waters, along the Siberian shelves.
1. Valk, O., Rutgers van der Loeff, M. M., Geibert, W., Gdaniec, S., Moran, S. B., Lepore, K., Edwards, RL., Lu, Y., Puigcorbé, V., Casacuberta, N., Paffrath, R., Smethie, W. Roy-Barman, M. (2020). Decrease in 230Th in the Amundsen Basin since 2007: far-field effect of increased scavenging on the shelf? Ocean Science, 16(1), 221–234. DOI: https://doi.org/10.5194/os-16-221-2020
2. Scholten, J.C., M.M. Rutgers van der Loeff, and A. Michel, Distribution of 230Th and 231Pa in the water column in relation to the ventilation of the deep Arctic basins. Deep-Sea Research II, 1995. 42: p. 1519-1531.
3. Hayes, C.T., et al., 230Th and 231Pa on GEOTRACES GA03, the U.S. GEOTRACES North Atlantic transect, and implications for modern and paleoceanographic chemical fluxes. Deep-Sea Research Part II: Topical Studies in Oceanography, 2015. 116: p. 29-41.
4. Vogler, S., et al., 230Th in the eastern North Atlantic: the importance of water mass ventilation in the balance of230Th. Earth and Planetary Science Letters, 1998. 156(1–2): p. 61-74.
5. Moran, S.B., et al., High precision 230Th and 232Th in the Norwegian Sea and Denmark by thermal ionization mass spectrometry. Geophysical Research Letters, 1995. 22(19): p. 2589-2592.
6. Gdaniec, S., et al., 231Pa and 230Th in the Arctic Ocean: Implications for boundary scavenging and 231Pa-230Th fractionation in the Eurasian Basin. Chemical Geology, 2020. 532: p. 119380.