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  • Compound-specific radiocarbon dating  (3)
  • Crenarchaeol  (1)
  • Lateral transport  (1)
  • American Geophysical Union  (4)
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  • American Geophysical Union  (4)
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  • 1
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    Lateral organic carbon supply to the deep Canada Basin (2010)
    American Geophysical Union
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2008. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 35 (2008): L11607, doi:10.1029/2008GL034271.
    Description: Understanding the processes driving the carbon cycle in the Arctic Ocean is important for assessing the impacts of the predicted rapid and amplified climate change in this region. We analyzed settling particle samples intercepted by a time-series sediment trap deployed in the abyssal Canada Basin (at 3067 m) in order to examine carbon export to the deep Arctic Ocean. Strikingly old radiocarbon ages (apparent mean 14C age = ∼1900 years) of the organic carbon, abundant lithogenic material (∼80%), and mass flux variations temporally decoupled from the cycle of primary productivity in overlying surface waters together suggest that, unlike other ocean basins, the majority of the particulate organic carbon entering the deep Canada Basin is supplied from the surrounding margins.
    Description: This research was funded by the NSF Ocean Sciences Division (Chemical Oceanography program) and NSF Office of Polar Programs, Office of Naval Research, as well as the Ocean and Climate Change Institute and Arctic Research Initiative at the Woods Hole Oceanographic Institution.
    Keywords: POC ; Lateral transport ; Canada Basin
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
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    An evaluation of 14C age relationships between co-occurring foraminifera, alkenones, and total organic carbon in continental margin sediments (2006)
    American Geophysical Union
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2005. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 20 (2005): PA1016, doi:10.1029/2004PA001103.
    Description: Radiocarbon age relationships between co-occurring planktic foraminifera, alkenones and total organic carbon in sediments from the continental margins of Southern Chile, Northwest Africa and the South China Sea were compared with published results from the Namibian margin. Age relationships between the sediment components are site-specific and relatively constant over time. Similar to the Namibian slope, where alkenones have been reported to be 1000 to 4500 years older than co-occurring foraminifera, alkenones were significantly (~1000 yrs) older than co-occurring foraminifera in the Chilean margin sediments. In contrast, alkenones and foraminifera were of similar age (within 2σ error or better) in the NW African and South China Sea sediments. Total-organic-matter and alkenone ages were similar off Namibia (age difference TOC-alkenones: 200-700 years), Chile (100-450 years), and NW Africa (360-770 years), suggesting minor contributions of pre-aged terrigenous material. In the South China Sea total organic carbon is significantly (2000-3000 yrs) older due to greater inputs of pre-aged terrigenous material. Age offsets between alkenones and planktic foraminifera are attributed to lateral advection of organic matter. Physical characteristics of the depositional setting, such as sea-floor morphology, shelf width, and sediment composition, may control the age of co-occurring 2 sediment components. In particular, offsets between alkenones and foraminifera appear to be greatest in deposition centers in morphologic depressions. Aging of organic matter is promoted by transport. Age offsets are correlated with organic richness, suggesting that formation of organic aggregate is a key process.
    Description: GM and MK acknowledge financial support from the WHOI postdoctoral scholarship program. This work was funded by NSF grant OCE-0327405.
    Keywords: Compound-specific radiocarbon dating ; Alkenones ; High accumulation rate sediments
    Repository Name: Woods Hole Open Access Server
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  • 3
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    Compound-specific radiocarbon dating of the varved Holocene sedimentary record of Saanich Inlet, Canada (2010)
    American Geophysical Union
    Details
    Publication Date: 2022-05-25
    Description: 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): PA2012, doi:10.1029/2003PA000927.
    Description: The radiocarbon contents of various biomarkers extracted from the varve-counted sediments of Saanich Inlet, Canada, were determined to assess their applicability for dating purposes. Calibrated ages obtained from the marine planktonic archaeal biomarker crenarchaeol compared favorably with varve-count ages. The same conclusion could be drawn for a more general archaeal biomarker (GDGT-0), although this biomarker proved to be less reliable due to its less-specific origin. The results also lend support to earlier indications that marine crenarchaeota use dissolved inorganic carbon (DIC) as their carbon source. The average reservoir age offset ΔR of 430 years, determined using the crenarchaeol radiocarbon ages, varied by ±110 years. This may be caused by natural variations in ocean-atmosphere mixing or upwelling at the NE Pacific coast but variability may also be due to an inconsistency in the marine calibration curve when used at sites with high reservoir ages.
    Description: This work was supported by the Netherlands Organization for Scientific Research (NWO) and NSF grants OCE-9907129 and OCE-0137005 (Eglinton).
    Keywords: Compound-specific radiocarbon dating ; Crenarchaeol ; Reservoir age ; NE Pacific ; Saanich Inlet
    Repository Name: Woods Hole Open Access Server
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  • 4
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    Aging of marine organic matter during cross-shelf lateral transport in the Benguela upwelling system revealed by compound-specific radiocarbon dating (2010)
    American Geophysical Union
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2007. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 8 (2007): Q09004, doi:10.1029/2007GC001603.
    Description: Organic matter accumulation and burial on the Namibian shelf and upper slope are spatially heterogeneous and strongly controlled by lateral transport in subsurface nepheloid layers. Much of the material deposited in depo-centers on the slope ultimately derives from the shelf. Supply of organic matter from the shelf involves selective transport of organic matter. We studied these selective transport processes by analyzing the radiocarbon content of co-occurring sediment fractions. Here we present radiocarbon data for total organic carbon as well as three tracers of surface ocean productivity (phytoplankton-derived alkenones, membrane lipids of pelagic crenarchaeota (crenarchaeol), and calcareous microfossils of planktic foraminifera) in core-top and near-surface sediment samples. The samples were collected on the Namibian margin along a shelf-slope transect (85 to 1040 m) at 24°S and from the upper slope depo-center at 25.5°S. In core-top sediments, alkenone ages gradually increased from modern to 3490 radiocarbon years with distance from shore and with water depth. Crenarchaeol, while younger than alkenones, also increased in age with distance offshore. It was concluded that the observed ages were a consequence of cross-shelf transport and associated aging of organic matter. Radiocarbon ages of preserved lipid biomarkers in sediments thus at least partially depend on the relative amount of laterally supplied, pre-aged material present in a sample, highlighting the importance of nepheloid transport for the sedimentation of organic matter over the Namibian margin.
    Description: This work was funded by NSF grant OCE- 0327405 to T.I.E. and by a Spinoza grant to J.S.S.D. from NWO.
    Keywords: Compound-specific radiocarbon dating ; Sediment transport
    Repository Name: Woods Hole Open Access Server
    Type: Article
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