Enhanced silicate weathering of tropical shelf sediments exposed during glacial lowstands; a sink for atmospheric CO2

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doi: 10.1016/j.gca.2016.12.010
Author(s): Wan Shiming; Clift, Peter Dominic; Zhao Debo; Hovius, Niels; Munhoven, Guy; France-Lanord, Christian; Wang Yinxi; Xiong Zhifang; Huang Jie; Yu, Zhaojie; Zhang Jin; Ma Wentao; Zhang Guoliang; Li Anchun; Li Tiegang
Author Affiliation(s): Primary:
Chinese Academy of Sciences, Institute of Oceanology, Qingdao, China
Université de Lorraine, France
Louisiana State University, United States
Deutsches GeoForschungsZentrum, Germany
Université de Liège, Belgium
Nanjing University, China
Université de Paris X, France
Tongji University, China
State Oceanic Administration, China
Volume Title: Geochimica et Cosmochimica Acta
Source: Geochimica et Cosmochimica Acta, Vol.200, p.123-144. Publisher: Elsevier, New York, NY, International. ISSN: 0016-7037 CODEN: GCACAK
Note: In English. Includes appendices. 125 refs.; illus., incl. 3 tables, sketch map
Summary: Atmospheric CO2 and global climate are closely coupled. Since 800 ka CO2 concentrations have been up to 50% higher during interglacial compared to glacial periods. Because of its dependence on temperature, humidity, and erosion rates, chemical weathering of exposed silicate minerals was suggested to have dampened these cyclic variations of atmospheric composition. Cooler and drier conditions and lower non-glacial erosion rates suppressed in situ chemical weathering rates during glacial periods. However, using systematic variations in major element geochemistry, Sr-Nd isotopes and clay mineral records from Ocean Drilling Program Sites 1143 and 1144 in the South China Sea spanning the last 1.1 Ma, we show that sediment deposited during glacial periods was more weathered than sediment delivered during interglacials. We attribute this to subaerial exposure and weathering of unconsolidated shelf sediments during glacial sealevel lowstands. Our estimates suggest that enhanced silicate weathering of tropical shelf sediments exposed during glacial lowstands can account for ∼9% of the carbon dioxide removed from the atmosphere during the glacial and thus represent a significant part of the observed glacial-interglacial variation of ∼80 ppmv. As a result, if similar magnitudes can be identified in other tropical shelf-slope systems, the effects of increased sediment exposure and subsequent silicate weathering during lowstands could have potentially enhanced the drawdown of atmospheric CO2 during cold stages of the Quaternary. This in turn would have caused an intensification of glacial cycles.
Year of Publication: 2017
Research Program: ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 24 Surficial Geology, Quaternary Geology; Carbon; Carbon cycle; Carbon dioxide; Cenozoic; Chemical weathering; Clay minerals; Climate change; Continental shelf; Crystal chemistry; Depositional environment; Geochemical cycle; Glacial environment; ICP mass spectra; Interglacial environment; Leg 184; Lowstands; Major elements; Marine environment; Marine sediments; Mass spectra; North Pacific; Northwest Pacific; ODP Site 1143; ODP Site 1144; Ocean Drilling Program; Pacific Ocean; Paleoclimatology; Pleistocene; Quaternary; Sediments; Sheet silicates; Shelf environment; Silicates; South China Sea; Spectra; Tropical environment; Weathering; West Pacific
Coordinates: N092143 N092143 E1131707 E1131707
N200311 N200311 E1172508 E1172508
Record ID: 2017055785
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands