noaa-ocean-15329 Eastern Equatorial Pacific Water Column Thorium Isotope Data Singh, A.; Marcantonio, F.; Lyle, M. Eastern Equatorial Pacific Water Column Thorium Isotope Data 2013-10-30 NCDC-Paleoclimatology ONLINE Files Pending https://www.ncdc.noaa.gov/paleo/study/15329 Investigator A. Singh Investigator F. Marcantonio Investigator M. Lyle earth science paleoclimate paleoceanography depth,null,null,meter,null,paleoceanography,null,null,N,null earth science paleoclimate paleoceanography 230Th,sediment,null,disintegration per minute per gram,null,paleoceanography,null,null,N,null earth science paleoclimate paleoceanography 232Th,sediment,one standard deviation,disintegration per minute per gram,null,paleoceanography,null,null,N,null earth science paleoclimate paleoceanography 230Th,sediment,one standard deviation,disintegration per minute per gram,null,paleoceanography,null,null,N,null earth science paleoclimate paleoceanography 232Th,sediment,null,disintegration per minute per gram,null,paleoceanography,null,null,N,null earth science paleoclimate paleocean radiogenic isotope geoscientificInformation Complete -8.3 6.5 -89.4 -85.3 -4178 -2525 Ocean Pacific Ocean Eastern Pacific Ocean WC-4>LATITUDE 3.6>LONGITUDE -85.4 Ocean Pacific Ocean Eastern Pacific Ocean WC-1>LATITUDE 6.5>LONGITUDE -85.3 Ocean Pacific Ocean Eastern Pacific Ocean WC-10>LATITUDE -2.4>LONGITUDE -85.4 Ocean Pacific Ocean Eastern Pacific Ocean WC-5>LATITUDE 1.5>LONGITUDE -85.4 Ocean Pacific Ocean Eastern Pacific Ocean WC-13>LATITUDE -8.3>LONGITUDE -88 Ocean Pacific Ocean Eastern Pacific Ocean WC-12>LATITUDE -6.1>LONGITUDE -87.4 Ocean Pacific Ocean Eastern Pacific Ocean WC-6>LATITUDE 0>LONGITUDE -89.4 Ocean Pacific Ocean Eastern Pacific Ocean WC-11>LATITUDE -4.3>LONGITUDE -86.5 None Please cite original publication, online resource, dataset and publication DOIs (where available), and date accessed when using downloaded data. If there is no publication information, please cite investigator, title, online resource, and date accessed. The appearance of external links associated with a dataset does not constitute endorsement by the Department of Commerce/National Oceanic and Atmospheric Administration of external Web sites or the information, products or services contained therein. For other than authorized activities, the Department of Commerce/NOAA does not exercise any editorial control over the information you may find at these locations. These links are provided consistent with the stated purpose of this Department of Commerce/NOAA Web site. English DOC/NOAA/NESDIS/NCEI National Centers for Environmental Information, NESDIS, NOAA, U.S. Department of Commerce https://www.ncdc.noaa.gov/data-access/paleoclimatology-data DATA Center Contact Bruce Bauer bruce.a.bauer@noaa.gov paleo@noaa.gov 303-497-6280 303-497-6513

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Boulder CO 80305-3328 USA online ASCII Singh, A., F. Marcantonio and M. Lyle 2013 Earth and Planetary Science Letters 362 294-304

In an effort to investigate the cause of higher-than-expected sediment inventories of 230Th in the Panama Basin, thorium isotopes were measured in eight deep-water casts within the Guatemala, Panama, and Peru Basins along a meridional transect at ~86°W between 6.5°N and 8.5°S. Dissolved 230Th concentrations increase linearly from the surface to 1000 m at each transect station. Below 1000 m, the deep waters of the Panama Basin show the highest deficit (~50%) of 230Th assuming a reversible exchange of 230Th between dissolved and sinking particulate matter, and in comparison with the globally averaged water-column 230Th. Peru Basin waters have a larger range of dissolved 230Th concentrations (7.9-16.5 fg/kg) than that within Panama Basin waters (5.7-7.1 fg/kg). There is a progressive decrease in average dissolved deep-water (>1000 m) 230Th concentrations from the southernmost sites in the Peru Basin toward the Panama Basin. We suggest that intense scavenging by upwelling-derived-productivity near the equator (±2º) and resuspension of ubiquitous Mn-rich particulates in Panama Basin sediments are the primary causes of the significant south-to-north lateral gradient in deep-water dissolved 230Th. Although 230Th from Peru Basin waters may be transported and then scavenged and ultimately buried in the Panama Basin, our calculations suggest that the quantity of advected 230Th is relatively small (between 15-30% of the total 230Th being produced within water column of the Panama Basin itself). Panama Basin sediment focusing factors greater than 1.3 cannot be explained by lateral export and excess scavenging of water column 230Th. Dissolved 232Th concentrations, in addition to being the lowest reported so far in the literature, fall within a very narrow range (6 pg/kg to 26 pg/kg), and are generally invariable with depth. This invariability suggests the dissolution of dust in surface waters as a likely sole source of dissolved 232Th for the entire water column. STUDY NOTES: Eight deep-water casts were all taken during cruise MV1014.

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