FN Archimer Export Format
PT J
TI An Estimate of Thorium 234 Partition Coefficients Through Global Inverse Modeling
BT 
AF LE GLAND, Guillaume
   AUMONT, Olivier
   MEMERY, Laurent
AS 1:1;2:2;3:1;
FF 1:;2:;3:;
C1 Inst Univ Europeen Mer, LEMAR, Plouzane, France.
   Inst Pierre Simon Laplace, LOCEAN, Paris, France.
C2 UBO, FRANCE
   IPSL, FRANCE
UM LEMAR
IN WOS Cotutelle UMR
   copubli-france
IF 3.559
TC 6
UR https://archimer.ifremer.fr/doc/00605/71666/70108.pdf
   https://archimer.ifremer.fr/doc/00605/71666/70109.xlsx
LA English
DT Article
DE ;thorium 234;inverse modeling;partition coefficient;biological carbon pump
AB Thorium-234 (Th-234), an insoluble radioisotope scavenged by marine particles, can be used as a proxy of the biological carbon pump. Thorium-234 observations can constrain biogeochemical models, but a necessary first step is to estimate the poorly known partition coefficients between particulate and dissolved phases. In this study, the Th-234 partition coefficients for five particle types, differing in size and chemical composition, are estimated by fitting a global 3-D Th-234 model based on the coupled ocean general circulation-biogeochemistry model NEMO-PISCES (at a resolution of 2 degrees) to a global Th-234 data set (including GEOTRACES data). Surface partition coefficients are estimated between 0.79 and 16.7x10(6). Biogenic silica has the smallest partition coefficients. Small particulate organic carbon and lithogenic dust have the largest. Thorium-234 observations at depth cannot be recovered without allowing partition coefficients to increase by one order of magnitude from surface to 1,000m deep. In our time-dependent global 3-D model, the biases introduced by three common assumptions made in biological carbon pump studies can be quantified. First, using the C:Th-234 ratio of large particles alone leads to an overestimation of carbon export at the base of the euphotic layer, by up to a factor 2. Furthermore, assuming steady state and neglecting transport by advection and diffusion can bias fluxes by as much as 50%, especially at high latitudes and in upwellings, with a sign and intensity depending on the season. 
PY 2019
PD JUL
SO Journal Of Geophysical Research-oceans
SN 2169-9275
PU Amer Geophysical Union
VL 124
IS 6
UT 000477722200007
BP 3575
EP 3606
DI 10.1029/2018JC014668
ID 71666
ER

EF