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

Ole Valk, Michiel M. Rutgers Van Der Loeff, Walter Geibert, Sandra Gdaniec, S. Bradley Moran, Kate Lepore, Robert Lawrence Edwards, Yanbin Lu, Viena Puigcorbé, Nuria Casacuberta, Ronja Paffrath, William Smethie, Matthieu Roy-Barman

Research output: Contribution to journalReview articlepeer-review

5 Scopus citations

Abstract

This study provides dissolved and particulate 230Th and 232Th results as well as particulate 234Th 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 230Th from 1991 to 2015 enables the identification of processes that control the temporal development of 230Th distributions in the Amundsen Basin. After 2007, 230Th 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 230Th concentrations leads to the observed depletion in dissolved 230Th in the central Arctic. Because atmospherically derived tracers (chlorofluorocarbon (CFC), sulfur hexafluoride (SF6)) 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 230Th depletion propagates downward in the water column by settling particles and reversible scavenging.

Original languageEnglish (US)
Pages (from-to)221-234
Number of pages14
JournalOcean Science
Volume16
Issue number1
DOIs
StatePublished - Feb 14 2020

Bibliographical note

Funding Information:
Financial support. This research has been supported by the

Funding Information:
Acknowledgements. We thank the captain and crew of RV Po-larstern for their help during expeditions ARKXXIX/3 and ARKXXII/2. We would like to thank Ronja Paffrath for help on board. Ingrid Stimac is thanked for invaluable technical support and help in the laboratory. This work was partially supported by a U.S. NSF grant (OCE, grant no. 143886) to Robert Lawrence Edwards. Finally we thank the two anonymous reviewers for very thoughtful and constructive comments, which helped to improve the paper.

Funding Information:
This research has been supported by the NSF (OCE, grant no. 143886) and the Swiss National Science Foundation (AMBIZIONE, grant no. PZ00P2-154805).

Publisher Copyright:
© Author(s) 2020.

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