In this study we present dissolved and particulate 230Th and 232Th results, as well as particulate 234Th data, obtained as part of the GEOTRACES central Arctic Ocean sections GN04 (2015) and IPY11 (2007). Samples were analyzed following GEOTRACES methods and compared to previous results from 1991. We observe significant decreases in 230Th concentrations in the deep waters of the Nansen Basin. We ascribe this nonsteady state removal process to a variable release and scavenging of trace metals near an ultraslow spreading ridge. This finding demonstrates that hydrothermal scavenging in the deep-sea may vary on annual time scales and highlights the importance of repeated GEOTRACES sections.
Bibliographical noteFunding Information:
We thank the Captain and crew of RV Polarstern for their help during expeditions ARKXXIX/3 and ARKXXII/2. We would like to thank Ronja Paffrath for help on board as well as Loes Gerringa, Vera Schlindwein, and Ursula Schauer for helpful discussions. Ingrid Stimac is thanked for invaluable technical support and help in the laboratory. We thank Matthieu Roy- Barman for providing five in situ pumps in 2015. Pere Masqué is thanked for enabling V. Puigcorbés participation in PS94, which was partly supported by the Generalitat de Catalunya through the research group MERS (2014 SGR- 1356). This work was partially supported by a U.S. NSF grant (OCE 143886) to R. L. E. Finally, we thank two anonymous reviewers for very helpful and constructive comments, which helped to improve the manuscript. The full radionuclide data set is available in the supporting information and at www. pangaea.de.
©2018. The Authors.
- Arctic Ocean
- Gakkel Ridge
- Th scavenging removal
- Th time series
- hydrothermal vents