Lower export production during glacial periods in the equatorial Pacific derived from (231Pa/230Th)xs,0 measurements in deep-sea sediments
Sims, Kenneth W. W.
McManus, Jerry F.
Leger, Susan Brown
MetadataShow full item record
The (231Pa/230Th)xs,0 records obtained from two cores from the western (MD97-2138; 1°25′S, 146°24′E, 1900 m) and eastern (Ocean Drilling Program Leg 138 Site 849, 0°11.59′N, 110°31.18′W, 3851 m) equatorial Pacific display similar variability over the last 85,000 years, i.e., from isotopic stages 1 to 5a, with systematically higher values during the Holocene, isotopic stage 3, and isotopic stage 5a, and lower values, approaching the production rate ratio of the two isotopes (0.093), during the colder periods corresponding to isotopic stages 2 and 4. We have also measured the 230Th-normalized biogenic preserved and terrigenous fluxes, as well as major and trace elements concentrations, in both cores. The (231Pa/230Th)xs,0 results combined with the changes in preserved carbonate and opal fluxes at the eastern site indicate lower productivity in the eastern equatorial Pacific during glacial periods. The (231Pa/230Th)xs,0 variations in the western equatorial Pacific also seem to be controlled by productivity (carbonate and/or opal). The generally high (231Pa/230Th)xs,0 ratios (>0.093) of the profile could be due to opal and/or MnO2 in the sinking particles. The profiles of (231Pa/230Th)xs,0 and 230Th-normalized fluxes indicate a decrease in exported carbonate, and possibly opal, during isotopic stages 2 and 4 in MD97-2138. Using 230Th-normalized flux, we also show that sediments from the two cores were strongly affected by sediment redistribution by bottom currents suggesting a control of mass accumulation rates by sediment focusing variability.
Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 19 (2004): PA4023, doi:10.1029/2003PA000994.
Showing items related by title, author, creator and subject.
The annual cycle of gross primary production, net community production, and export efficiency across the North Pacific Ocean Palevsky, Hilary I.; Quay, Paul D.; Lockwood, Deirdre E.; Nicholson, David P. (John Wiley & Sons, 2016-02-27)We measured triple oxygen isotopes and oxygen/argon dissolved gas ratios as nonincubation-based geochemical tracers of gross oxygen production (GOP) and net community production (NCP) on 16 container ship transects across ...
Discrepant estimates of primary and export production from satellite algorithms, a biogeochemical model, and geochemical tracer measurements in the North Pacific Ocean Palevsky, Hilary I.; Quay, Paul D.; Nicholson, David P. (John Wiley & Sons, 2016-08-30)Estimates of primary and export production (PP and EP) based on satellite remote sensing algorithms and global biogeochemical models are widely used to provide year-round global coverage not available from direct observations. ...
Primary, new and export production in the NW Pacific subarctic gyre during the vertigo K2 experiments Elskens, Marc; Brion, N.; Buesseler, Ken O.; Van Mooy, Benjamin A. S.; Boyd, Philip W.; Dehairs, Frank; Savoye, Nicolas; Baeyens, W. (2008-01-28)This paper presents results on tracer experiments using 13C and 15N to estimate uptake rates of dissolved inorganic carbon (DIC) and nitrogen (DIN). Experiments were carried out at station K2 (47°N, 161°E) in the NW ...