FN Archimer Export Format
PT J
TI Silicon pool dynamics and biogenic silica export in the Southern Ocean inferred from Si-isotopes
BT 
AF FRIPIAT, F.
   CAVAGNA, A. -J.
   DEHAIRS, F.
   SPEICH, Sabrina
   ANDRE, L.
   CARDINAL, D.
AS 1:1,2;2:3;3:3;4:4;5:1;6:1;
FF 1:;2:;3:;4:;5:;6:;
C1 Royal Museum Cent Africa, Sect Mineral & Petrog, Tervuren, Belgium.
   Univ Libre Bruxelles, Dept Earth & Environm Sci, Brussels, Belgium.
   Vrije Univ Brussel, Brussels, Belgium.
   IFREMER, CNRS, Lab Phys Oceans, IRD,UBO,UMR6523, Plouzane, France.
C2 ROYAL MUSEUM CENT AFRICA, BELGIUM
   UNIV LIBRE BRUXELLES, BELGIUM
   UNIV VRIJE BRUSSEL, BELGIUM
   UBO, FRANCE
IN DOAJ
IF 2.293
TC 40
TU Centre national de la recherche scientifique
   Institut de recherche pour le développement
   Institut français de recherche pour l'exploitation de la mer
   Université de Bretagne Occidentale
UR https://archimer.ifremer.fr/doc/00052/16298/13811.pdf
LA English
DT Article
CR MD 166 / BONUS-GOODHOPE
BO Marion Dufresne
AB Silicon isotopic signatures (delta(30)Si) of water column silicic acid (Si(OH)(4)) were measured in the Southern Ocean, along a meridional transect from South Africa (Subtropical Zone) down to 57 degrees S (northern Weddell Gyre). This provides the first reported data of a summer transect across the whole Antarctic Circumpolar Current (ACC). delta(30)Si variations are large in the upper 1000 m, reflecting the effect of the silica pump superimposed upon meridional water transfer across the ACC: the transport of Antarctic surface waters northward by a net Ekman drift and their convergence and mixing with warmer upper-ocean Si-depleted waters to the north. Using Si isotopic signatures, we determine different mixing interfaces: the Antarctic Surface Water (AASW), the Antarctic Intermediate Water (AAIW), and thermoclines in the low latitude areas. The residual silicic acid concentrations of end-members control the delta(30)Si alteration of the mixing products and with the exception of AASW, all mixing interfaces have a highly Si-depleted mixed layer end-member. These processes deplete the silicic acid AASW concentration northward, across the different interfaces, without significantly changing the AASW delta(30)Si composition. By comparing our new results with a previous study in the Australian sector we show that during the circumpolar transport of the ACC eastward, the delta(30)Si composition of the silicic acid pools is getting slightly, but significantly lighter from the Atlantic to the Australian sectors. This results either from the dissolution of biogenic silica in the deeper layers and/or from an isopycnal mixing with the deep water masses in the different oceanic basins: North Atlantic Deep Water in the Atlantic, and Indian Ocean deep water in the Indo-Australian sector. This isotopic trend is further transmitted to the subsurface waters, representing mixing interfaces between the surface and deeper layers. Through the use of delta(30)Si constraints, net biogenic silica production (representative of annual export), at the Greenwich Meridian is estimated to be 5.2 +/- 1.3 and 1.1 +/- 0.3 mol Sim(-2) for the Antarctic Zone and Polar Front Zone, respectively. This is in good agreement with previous estimations. Furthermore, summertime Si-supply into the mixed layer of both zones, via vertical mixing, is estimated to be 1.6 +/- 0.4 and 0.1 +/- 0.5 mol Sim(-2), respectively.
PY 2011
SO Ocean Science
SN 1812-0784
PU Copernicus Gesellschaft Mbh
VL 7
IS 5
UT 000296742800001
BP 533
EP 547
DI 10.5194/os-7-533-2011
ID 16298
ER

EF