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


Contact
ole.valk [ at ] awi.de

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.



Item Type
Article
Authors
Divisions
Primary Division
Programs
Primary Topic
Peer revision
ISI/Scopus peer-reviewed
Publication Status
Published
Eprint ID
53834
DOI 10.5194/os-16-221-2020

Cite as
Valk, O. , Rutgers van der Loeff, M. M. , Geibert, W. , Gdaniec, S. , Moran, S. B. , Lepore, K. , Edwards, R. L. , Lu, Y. , Puigcorbé, V. , Casacuberta, N. , Paffrath, R. , Smethie, W. and Roy-Barman, M. (2020): Decrease ²³⁰Th in the Amundsen Basin since 2007: far-field effect of increased scavenging on the shelf? , Ocean Science, 16 (1), pp. 221-234 . doi: 10.5194/os-16-221-2020


Share


Citation

Geographical region

Research Platforms

Campaigns
ARK > XXIX > 3


Actions
Edit Item Edit Item