TY  - JOUR
A1  - Hayes, Christopher T.
A1  - Anderson, Robert F.
A1  - Fleisher, Martin Q.
A1  - Serno, Sascha
A1  - Winckler, Gisela
A1  - Gersonde, Rainer
T1  - Biogeography in Pa-231/Th-230 ratios and a balanced Pa-231 budget for the Pacific Ocean
JF  - Earth & planetary science letters
N2  - The ratio of unsupported protactinium-231 to thorium-230 in marine sediments, (Pa/Th)(xs), is potentially sensitive to several processes of oceanographic and climatological interest: deep ocean circulation, marine biological productivity (as it relates to total particle flux) and particle composition (specifically, biogenic opal and authigenic Mn). In order to attribute variations in (Pa/Th)(xs) observed in sediment records to changes in specific processes through time, a better understanding of the chemical cycling of these elements in the modern ocean is necessary. To this end, a survey was undertaken of (Pa/Th)(xs) in surface sediments from the subarctic Pacific (SO202-INOPEX expedition) in combination with a Pacific-wide compilation of published data. Throughout the Pacific, (Pa/Th)(xs) is robustly correlated with the opal content of sediments. In the North and equatorial Pacific, simultaneous positive correlations with productivity indicators suggest that boundary scavenging and opal scavenging combine to enhance the removal of Pa in the eastern equatorial Pacific and subarctic Pacific. Deep ocean water mass ageing (>3.5 km) associated with the Pacific overturning appears to play a secondary role in determining the basin scale distribution of (Pa/Th)(xs). A basin-wide extrapolation of Pa removal is performed which suggests that the Pacific Pa budget is nearly in balance. We hypothesize that through time (Pa/Th)(xs) distributions in the Pacific could define the evolving boundaries of contrasting biogeographic provinces in the North Pacific, while the influence of hydrothermal scavenging of Pa potentially confounds this approach in the South Pacific.
KW  - thorium
KW  - protactinium
KW  - biogeographic provinces
KW  - boundary scavenging
KW  - INOPEX
Y1  - 2014
U6  - https://doi.org/10.1016/j.epsl.2014.02.001
SN  - 0012-821X
SN  - 1385-013X
VL  - 391
SP  - 307
EP  - 318
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Hayes, Christopher T.
A1  - Anderson, Robert F.
A1  - Fleisher, Martin Q.
A1  - Serno, Sascha
A1  - Winckler, Gisela
A1  - Gersonde, Rainer
T1  - Quantifying lithogenic inputs to the North Pacific Ocean using the long-lived thorium isotopes
JF  - Earth & planetary science letters
N2  - Dissolved Th-232 is added to the ocean though the partial dissolution of lithogenic materials such as aerosol dust in the same way as other lithogenically sourced and more biologically important trace metals such as Fe. Oceanic Th-230, on the other hand, is sourced primarily from the highly predictable decay of dissolved U-234. The rate at which dissolved Th-232 is released by mineral dissolution can be constrained by a Th removal rate derived from Th-230:U-234 disequilibria, assuming steady-state. Calculated fluxes of dissolved Th-232 can in turn be used to estimate fluxes of other lithogenically sourced dissolved metals as well as the original lithogenic supplies, such as aerosol dust deposition, given the concentration and fractional solubility of Th (or other metals) in the lithogenic material. This method is applied to 7 water column profiles from the Innovative North Pacific Experiment (INOPEX) cruise of 2009 and 2 sites from the subtropical North Pacific. The structure of shallow depth profiles suggests rapid scavenging at the surface and at least partial regeneration of dissolved Th-232 at 100-200 m depth. This rapid cycling could involve colloidal Th generated during mineral dissolution, which may not be subject to the same removal rates as the more truly dissolved Th-230. An additional deep source of Th-232 was revealed in deep waters, most likely dissolution of seafloor sediments, and offers a constraint on dissolved trace element supply due to boundary exchange. (C) 2013 Elsevier B.V. All rights reserved.
KW  - dust
KW  - aerosols
KW  - thorium
KW  - boundary exchange
KW  - North Pacific Ocean
KW  - GEOTRACES compliant
Y1  - 2013
U6  - https://doi.org/10.1016/j.epsl.2013.09.025
SN  - 0012-821X
SN  - 1385-013X
VL  - 383
IS  - 12
SP  - 16
EP  - 25
PB  - Elsevier
CY  - Amsterdam
ER  -