Achterberg, Eric P. , Steiner, Zvi and Galley, Christopher G. (2022) South Pacific GEOTRACES Cruise No. SO289, 18 February 2022 – 08 April 2022, Valparaiso (Chile) – Noumea (New Caledonia), GEOTRACES GP21. . SONNE-Berichte, SO289 . Gutachterpanel, Bonn, 141 pp. DOI 10.48433/cr_so289.

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Abstract

Research cruise SO289 with FS Sonne was sailed in austral autumn of 2022 in the South
Pacific Ocean (SPO) from Valparaiso (Chile) to Noumea (New Caledonia), with a focus on
trace element biogeochemistry and chemical oceanography but also including physical and
biological oceanographic components. The research topic of the cruise was to determine in
detail the distributions, sources and sinks of trace elements and their isotopes (TEIs) in the
water column along a zonal section in one of the least studied ocean regions on earth. Our aim
was to investigate the biogeochemical cycling of TEIs, and their interactions with surface ocean
productivity and the carbon and nitrogen cycles (incl. N2 fixation) given that some TEIs act as
micronutrients. The findings will have global significance for understanding the chemical
environment in which ecosystems operate. The supply pathways of TEIs to the SPO from ocean
boundaries including the atmosphere (Australian dust), continents (mainly Maipo River),
sediments (on continental shelves/slopes), and ocean crust (hydrothermalism) were
investigated. The TEI transport within water masses was determined with a focus on the
southward flow of hydrothermally derived TEIs towards the Southern Ocean but also the deep
inflow of Southern Ocean waters in the western SPO. The TEI transport assessment along the
cruise track will allow a more reliable use of some TEIs as paleo-circulation proxies. The cruise
will officially be part of the international GEOTRACES program.

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