Changes in opal flux and the rain ratio during the last 50,000 years in the Equatorial Pacific

Online Access: Get full text
doi: 10.1016/j.dsr2.2007.01.012
Author(s): Richaud, Mathieu; Loubere, Paul; Pichat, Sylvain; François, Roger
Author Affiliation(s): Primary:
Northern Illinois University, Department of Geology and Environmental Geosciences, DeKalb, IL, United States
University of Oxford, United Kingdom
University of British Columbia, Canada
Volume Title: Role of marine organic carbon and calcite fluxes in driving global climate change, past and future
Volume Author(s): Loubere, Paul, editor
Source: Deep-Sea Research. Part II: Topical Studies in Oceanography, 54(5-7), p.762-771; Chapman conference on The role of marine organic carbon and calcite fluxes in driving global climate change, past and future, Woods Hole, MA, July, 2005, edited by Paul Loubere. Publisher: Elsevier, Oxford, International. ISSN: 0967-0645
Note: In English. Based on Publisher-supplied data; illus., incl. 2 tables
Summary: Changes in the orgC/CaCO3 ratio in particles sinking from the surface to the deep ocean have the potential to alter the atmospheric pCO2 over the span of a glacial/interglacial cycle. Recent paleoceanographic and modern observational studies suggest that silica is a key factor in the global carbon biogeochemical cycle that can influence the flux ratio, especially at low latitudes, through "silicic acid leakage" [Brzezinski, M., Pride, C., Franck, M., Sigman, D., Sarmiento, J., Matsumoto, K., Gruber, N., Rau, R., Coale, K., 2002. A switch from Si(OH)4 to NO3- depletion in the glacial Southern Ocean. Geophysical Research Letters 29, 5]. To test this hypothesis, we reconstruct biogenic fluxes of CaCO3, orgC and Si for three equatorial Pacific cores. We find evidence that a floral shift from a SiO2-based community to a CaCO3-based occurred, starting in mid-marine isotope stage (MIS) 3 (24-59 cal.ka) and declining toward MIS 2 (19-24 cal.ka). This could reflect the connection of the Peru upwelling system to the subantarctic region, and we postulate that excess silica was transported from the subantarctic via the deep Equatorial Undercurrent to the eastern equatorial Pacific. In the eastern equatorial Pacific only, we document a significant decrease in rain ratio starting mid-MIS 3 toward MIS 2. This decrease is concomitant with a significant decrease in silica accumulation rates at the seabed. This pattern is not observed in the Pacific influenced by equatorial divergence and shallow upwelling, where all reconstructed fluxes (CaCO3, orgC, and opal) increase during MIS 2. We conclude that the overall calcium carbonate pump weakened in the EEP under Peru upwelling influence. Abstract Copyright (2007) Elsevier, B.V.
Year of Publication: 2007
Research Program: ODP Ocean Drilling Program
Key Words: 24 Surficial Geology, Quaternary Geology; Actinides; Alkaline earth metals; Calcite; Calcium; Calcium carbonate; Carbon; Carbon cycle; Carbon dioxide; Carbonates; Cenozoic; Chemical ratios; Cores; East Pacific; Equatorial Pacific; Framework silicates; Geochemical cycle; Glacial environment; Isotopes; Leg 138; MIS 3; Metals; Nitrates; North Pacific; Northeast Pacific; ODP Site 846; ODP Site 849; Ocean Drilling Program; Opal; Organic carbon; Pacific Ocean; Paleocirculation; Paleoclimatology; Paleocurrents; Pleistocene; Quaternary; Radioactive isotopes; Silica; Silica minerals; Silicates; South Pacific; Southeast Pacific; Southern Ocean; Th-230; Thorium; Upwelling
Coordinates: S030549 S030541 W0904904 W0904906
N001058 N001100 W1103110 W1103111
Record ID: 2010037818
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands