Decrease in 230 Th in the Amundsen Basin since 2007: far-field effect of increased scavenging on the shelf?

This study provides dissolved and particulate 230 Th and 232 Th results as well as particulate 234 Th data collected during expeditions to the central Arctic Ocean (GEOTRACES, an international project to identify processes and quantify fluxes that control the distributions of trace elements; section...

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Bibliographic Details
Published in:Ocean Science
Main Authors: O. Valk, M. M. Rutgers van der Loeff, W. Geibert, S. Gdaniec, S. B. Moran, K. Lepore, R. L. Edwards, Y. Lu, V. Puigcorbé, N. Casacuberta, R. Paffrath, W. Smethie, M. Roy-Barman
Format: Article in Journal/Newspaper
Language:English
Published: Copernicus Publications 2020
Subjects:
Geography. Anthropology. Recreation
G
Environmental sciences
GE1-350
Arctic
Arctic Ocean
Barents Sea
Amundsen Basin
amundsen basin
Fram Strait
Online Access:https://doi.org/10.5194/os-16-221-2020
https://doaj.org/article/4e1c4cfb6d2a44f68ccdf5df7541cd82
Description
Summary:This study provides dissolved and particulate 230 Th and 232 Th results as well as particulate 234 Th data collected during expeditions to the central Arctic Ocean (GEOTRACES, an international project to identify processes and quantify fluxes that control the distributions of trace elements; sections GN04 and GIPY11). Constructing a time series of dissolved 230 Th from 1991 to 2015 enables the identification of processes that control the temporal development of 230 Th distributions in the Amundsen Basin. After 2007, 230 Th concentrations decreased significantly over the entire water column, particularly between 300 and 1500 m. This decrease is accompanied by a circulation change, evidenced by a concomitant increase in salinity. A potentially increased inflow of water of Atlantic origin with low dissolved 230 Th concentrations leads to the observed depletion in dissolved 230 Th in the central Arctic. Because atmospherically derived tracers (chlorofluorocarbon (CFC), sulfur hexafluoride (SF 6 )) do not reveal an increase in ventilation rate, it is suggested that these interior waters have undergone enhanced scavenging of Th during transit from Fram Strait and the Barents Sea to the central Amundsen Basin. The 230 Th depletion propagates downward in the water column by settling particles and reversible scavenging.

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