10.1594/PANGAEA.745479
Rutgers van der Loeff, Michiel M
Michiel M
Rutgers van der Loeff
0000-0003-1393-3742
Cai, Pinghe
Pinghe
Cai
Stimac, Ingrid
Ingrid
Stimac
0000-0001-6053-2330
Bracher, Astrid
Astrid
Bracher
0000-0003-3025-5517
Middag, Rob
Rob
Middag
0000-0002-3326-530X
Klunder, Maarten B
Maarten B
Klunder
van Heuven, Steven
Steven
van Heuven
0000-0003-2001-8710
Radionuclides measured on 27 water bottle profiles during POLARSTERN cruise ANT-XXIV/3
PANGAEA
2011
CTD/Rosette
ANT-XXIV/3
Polarstern
Global marine biogeochemical cycles of trace elements and their isotopes (GEOTRACES)
Marine Geochemistry @ AWI (AWI_MarGeoChem)
Priority Programme 1158 Antarctic Research with Comparable Investigations in Arctic Sea Ice Areas (SPP1158)
2008-02-13T15:41:00/2008-04-11T14:14:00
Supplementary Publication Series of Datasets
10.1016/j.dsr2.2011.02.004
27 datasets
application/zip
Creative Commons Attribution 3.0 Unported
As part of the GEOTRACES Polarstern expedition ANT XXIV/3 (ZERO and DRAKE) we have measured the vertical distribution of 234Th on sections through the Antarctic Circumpolar Current along the zero meridian and in Drake Passage and on an EW section through the Weddell Sea. Steady state export fluxes of 234Th from the upper 100m, derived from the depletion of 234Th with respect to its parent 238U, ranged from 621±105 dpm/m**2/d to 1773±90 dpm/m**2/d. This 234Th flux was converted into an export flux of organic carbon ranging from 3.1-13.2 mmolC/m**2/d (2.1-9.0 mmolC/m**2/d) using POC/234Th ratio of bulk (respectively >50 µm) suspended particles at the export depth (100 m). Non-steady state fluxes assuming zero flux under ice cover were up to 23% higher. In addition, particulate and dissolved 234Th were measured underway in high resolution in the surface water with a semi-automated procedure. Particulate 234Th in surface waters is inversely correlated with light transmission and pCO2 and positively with fluorescence and optical backscatter and is interpreted as a proxy for algal biomass. High resolution underway mapping of particulate and dissolved 234Th in surface water shows clearly where trace elements are absorbed by plankton and where they are exported to depth. Quantitative determination of the export flux requires the full 234Th profile since surface depletion and export flux become decoupled through changes in wind mixed layer depth and in contribution to export from subsurface layers.
In a zone of very low algal abundance (54-58 °S at the zero meridian), confirmed by satellite Chl-a data, the lowest carbon export of the ACC was observed, allowing Fe and Mn to maintain their highest surface concentrations (Klunder et al., this issue, Middag et al., this issue).
An ice-edge bloom that had developed in Dec/Jan in the zone 60-65 °S as studied during the previous leg (Strass et al., in prep) had caused a high export flux at 64.5 °S when we visited the area two months later (Feb/March). The ice-edge bloom had then shifted south to 65-69 °S evident from uptake of CO2 and dissolved Fe, Mn and 234Th, without causing export yet. In this way, the parallel analysis of 234Th can help to explain the scavenging behaviour of other trace elements.
Supplement to: Rutgers van der Loeff, Michiel M; Cai, Pinghe; Stimac, Ingrid; Bracher, Astrid; Middag, Rob; Klunder, Maarten B; van Heuven, Steven (2011): 234Th in surface waters: distribution of particle export flux across the Antarctic Circumpolar Current and in the Weddell Sea during the GEOTRACES expedition ZERO and DRAKE. Deep Sea Research Part II: Topical Studies in Oceanography, 58(25-26), 2749-2766
-64.4433
8.9995
-69.4001
-42.3328
South Atlantic Ocean
Weddell Sea
Scotia Sea, southwest Atlantic
Drake Passage
German Research Foundation
https://doi.org/10.13039/501100001659
5472008
Priority Programme 1158 Antarctic Research with Comparable Investigations in Arctic Sea Ice Areas