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  • PANGAEA  (130)
  • The Oceanography Society  (1)
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  • 1
    Publication Date: 2022-05-26
    Description: Author Posting. © The Oceanography Society, 2014. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 27, no. 3 (2014): 10-16, doi:10.5670/oceanog.2014.78.
    Description: Anthropogenically driven climate change will rapidly become Earth's dominant transformative influence in the coming decades. The oceanic biological pump—the complex suite of processes that results in the transfer of particulate and dissolved organic carbon from the surface to the deep ocean—constitutes the main mechanism for removing CO2 from the atmosphere and sequestering carbon at depth on submillennium time scales. Variations in the efficacy of the biological pump and the strength of the deep ocean carbon sink, which is larger than all other bioactive carbon reservoirs, regulate Earth's climate and have been implicated in past glacial-​interglacial cycles. The numerous biological, chemical, and physical processes involved in the biological pump are inextricably linked and heterogeneous over a wide range of spatial and temporal scales, and they influence virtually the entire ocean ecosystem. Thus, the functioning of the oceanic biological pump is not only relevant to the modulation of Earth's climate but also constitutes the basis for marine biodiversity and key food resources that support the human population. Our understanding of the biological pump is far from complete. Moreover, how the biological pump and the deep ocean carbon sink will respond to the rapid and ongoing anthropogenic changes to our planet—including warming, acidification, and deoxygenation of ocean waters—remains highly uncertain. To understand and quantify present-day and future changes in biological pump processes requires sustained global observations coupled with extensive modeling studies supported by international scientific coordination and funding.
    Description: We thank the National Science Foundation for support of ocean biogeochemical flux studies, including the US JGOFS program throughout its tenure; OCE 9986766 to S. Honjo; and OCE-0425677, OCE-0851350, and OPP-0909377 to T. Eglinton.
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 2
    Publication Date: 2023-03-03
    Description: The data set compiles gamma-ray wet bulk density, magnetic susceptibility (MS), and XRF core scans of the three cores GeoB16433-1 (38° 07.843'N, 144° 00.135'E, 7,525 m water depth), GeoB16431-1 (38° 00.177'N, 143° 59.981'E, 7,542 m water depth), and GeoB16444-1 (37° 42.017'N, 143° 52.377'E, 7,529 m water depth) retrieved from the central Japan Trench during Sonne Cruise SO219A in 2012. Gamma-ray wet bulk density and MS were measured by using the Geotek multi-sensor core logger at MARUM, University of Bremen. XRF core scans (elements: Al, Si, S, K, Ca, Ti, Mn, Fe, Br, Rb, Sr, Zr) were analyzed by using the Avaatech XRF core scanner at MARUM, University of Bremen.
    Keywords: Center for Marine Environmental Sciences; density; magnetic susceptibility; MARUM; XRF CS
    Type: Dataset
    Format: application/zip, 3 datasets
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  • 3
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    PANGAEA
    In:  Supplement to: Schefuß, Enno; Eglinton, Timothy Ian; Spencer-Jones, Charlotte L; Rullkötter, Jürgen; De Pol-Holz, Ricardo; Talbot, Helen M; Grootes, Pieter Meiert; Schneider, Ralph R (2016): Hydrologic control of carbon cycling and aged carbon discharge in the Congo River basin. Nature Geoscience, 9(9), 687-690, https://doi.org/10.1038/ngeo2778
    Publication Date: 2023-03-11
    Description: The age of organic material discharged by rivers provides information about its sources and carbon cycling processes within watersheds. While elevated ages in fluvially-transported organic matter are usually explained by erosion of soils and sediments, it is commonly assumed that mainly young organic material is discharged from flat tropical watersheds due to their extensive plant cover and high carbon turnover. Here we present compound-specific radiocarbon data of terrigenous organic fractions from a sedimentary archive offshore the Congo River in conjunction with molecular markers for methane-producing land cover reflecting wetland extent in the watershed. We find that the Congo River has been discharging aged organic matter for several thousand years with increasing ages from the mid- to the Late Holocene. This suggests that aged organic matter in modern samples is concealed by radiocarbon from nuclear weapons testing. By comparison to indicators for past rainfall changes we detect a systematic control of organic matter sequestration and release by continental hydrology mediating temporary carbon storage in wetlands. As aridification also leads to exposure and rapid remineralization of large amounts of previously stored labile organic matter we infer that this process may cause a profound direct climate feedback currently underestimated in carbon cycle assessments.
    Keywords: Center for Marine Environmental Sciences; MARUM
    Type: Dataset
    Format: application/zip, 4 datasets
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  • 4
    Publication Date: 2023-05-12
    Description: The Benguela Upwelling System is situated between 18°S and 26°S and is characterized by seasonally variable upwelling cells, elevated surface primary and secondary productivity, high sedimentary organic carbon concentrations (up to 20 %), and locally stable bottom water anoxia. Between 2014 and 2019, surface sediment cores were collected, subsampled, and analysed using geochemical and sedimentological tools. For the grain size fractionation, a combined sieve-centrifuge-filtering approach was developed to create seven fractions (〉 250, 250-200, 200-125, 125-63, 63-10, 10-2, ≤ 2.0 µm) and the density fractionation followed a centrifugation sequence to yield four fractions using sodium polytungstate (NaW) heavy liquid (≤ 1.6, 1.6-2.0, 2.0-2.5, 〉 2.5 g cm-3) (cf., Wakeham et al., 2009, https://doi.org/10.1016/j.marchem.2009.08.005). The bulk surface sediment and each fraction were analysed for TOC (%), radiocarbon age (F14C), and surface area (m2 g-1). Together with literature data, these samples are used to test and illustrate a novel hypothesis on sediment hydrodynamic properties in oxygen-depleted environments.
    Keywords: Benguela Upwelling System; density fractionation; grain size analysis; radiocarbon isotope (Fm); SLOB; Total Organic Carbon
    Type: Dataset
    Format: application/zip, 16 datasets
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  • 5
    Publication Date: 2023-04-22
    Description: Compound-specific radiocarbon dating often requires working with small samples of 〈 100 µg carbon (µgC). This makes the radiocarbon dates of biomarker compounds very sensitive to biases caused by extraneous carbon of unknown composition, a procedural blank, which is introduced to the samples during the steps necessary to prepare a sample for radiocarbon analysis by accelerator mass spectrometry (i.e., isolating single compounds from a heterogeneous mixture, combustion, gas purification and graphitization). Reporting accurate radiocarbon dates thus requires a correction for the procedural blank. We present our approach to assess the fraction modern carbon (F14C) and the mass of the procedural blanks introduced during the preparation procedures of lipid biomarkers (i.e. n-alkanoic acids) and lignin phenols. We isolated differently sized aliquots (6-151 µgC) of n-alkanoic acids and lignin phenols obtained from standard materials with known F14C values. Each compound class was extracted from two standard materials (one fossil, one modern) and purified using the same procedures as for natural samples of unknown F14C. There was an inverse linear relationship between the measured F14C values of the processed aliquots and their mass, which suggests constant contamination during processing of individual samples. We used Bayesian methods to fit linear regression lines between F14C and 1/mass for the fossil and modern standards. The intersection points of these lines were used to infer F14Cblank and mblank and their associated uncertainties. We estimated 4.88±0.69 μgC of procedural blank with F14C of 0.714±0.077 for n-alkanoic acids, and 0.90±0.23 μgC of procedural blank with F14C of 0.813±0.155 for lignin phenols. These F14Cblank and mblank can be used to correct AMS results of lipid and lignin samples by isotopic mass balance. This method may serve as a standardized procedure for blank assessment in small-scale radiocarbon analysis.
    Keywords: AWI_Envi; Center for Marine Environmental Sciences; MARUM; Polar Terrestrial Environmental Systems @ AWI
    Type: Dataset
    Format: application/zip, 2.5 MBytes
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  • 6
    Publication Date: 2023-04-22
    Keywords: AWI_Envi; Compounds; Event label; Fraction modern carbon; Fraction modern carbon, standard deviation; Laboratory code/label; Mass; Mass, standard deviation; Messel_oil_shale; Messel, Germany; OUTCROP; Outcrop sample; Polar Terrestrial Environmental Systems @ AWI; Type
    Type: Dataset
    Format: text/tab-separated-values, 205 data points
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  • 7
    Publication Date: 2023-01-13
    Description: The Lingtai section is situated in the central part of the CLP at ~1340 m above sea level (35°04'N, 107°39'E). Long chain n-alkane plant waxes and brGDGTs were analysed in 10 cm thick layers collected at 0.5 m intervals from the upper 18.5 m of the LPS. The section covers the past 200 ka based on the correlation of the quartz grain size record from Lingtai (Sun et al., 2006) with the global benthic d18O stack (Lisiecki and Raymo, 2005), resulting in an average resolution of our records of ~5 ka. From the detected biomarker distributions and their stable isotopic composition, we generated records of vegetation change based on the ACL and the weighed mean of the carbon isotopic composition of the most abundant plant waxes, i.e. the C29, C31, and C33 n-alkanes (δ13Cwax), precipitation using the hydrogen isotopic composition of the same suite of n-alkanes (δ2Hwax), and finally MAT for months above freezing using the MBT'5ME index (De Jonge et al., 2014) and the BayMBT0 model (Dearing Crampton-Flood et al., 2020).
    Type: Dataset
    Format: application/zip, 4 datasets
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  • 8
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    PANGAEA
    In:  Supplement to: Coppola, Alysha I; Wiedemeier, Daniel B; Galy, Valier; Haghipour, Negar; Hanke, Ulrich M; Nascimento, Gabriela S; Usman, Muhammed Ojoshogu; Blattmann, Thomas Michael; Reisser, Moritz; Freymond, Chantal V; Zhao, Meixun; Voss, Britta; Wacker, Lukas; Schefuß, Enno; Peucker-Ehrenbrink, Bernhard; Abiven, Samuel; Schmidt, Michael W I; Eglinton, Timothy Ian (2018): Global-scale evidence for the refractory nature of riverine black carbon. Nature Geoscience, 11(8), 584-588, https://doi.org/10.1038/s41561-018-0159-8
    Publication Date: 2023-01-13
    Description: Wildfires and incomplete combustion of fossil fuel produce large amounts of black carbon. Black carbon production and transport are essential components of the carbon cycle. Constraining estimates of black carbon exported from land to ocean is critical, given ongoing changes in land use and climate, which affect fire occurrence and black carbon dynamics. Here, we present an inventory of the concentration and radiocarbon content (∆14C) of particulate black carbon for 18 rivers around the globe. We find that particulate black carbon accounts for about 15.8 ± 0.9% of river particulate organic carbon, and that fluxes of particulate black carbon co-vary with river-suspended sediment, indicating that particulate black carbon export is primarily controlled by erosion. River particulate black carbon is not exclusively from modern sources but is also aged in intermediate terrestrial carbon pools in several high-latitude rivers, with ages of up to 17,000 14C years. The flux-weighted 14C average age of particulate black carbon exported to oceans is 3,700 ± 400 14C years. We estimate that the annual global flux of particulate black carbon to the ocean is 0.017 to 0.037 Pg, accounting for 4 to 32% of the annually produced black carbon. When buried in marine sediments, particulate black carbon is sequestered to form a long-term sink for CO2.
    Type: Dataset
    Format: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet, 29.3 kBytes
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  • 9
    Publication Date: 2023-01-13
    Keywords: Branched Glycerol dialkyl glycerol tetraethers, fractional abundance Ia; Branched Glycerol dialkyl glycerol tetraethers, fractional abundance Ib; Branched Glycerol dialkyl glycerol tetraethers, fractional abundance Ic; Branched Glycerol dialkyl glycerol tetraethers, fractional abundance IIa; Branched Glycerol dialkyl glycerol tetraethers, fractional abundance IIb; Branched Glycerol dialkyl glycerol tetraethers, fractional abundance IIc; Branched Glycerol dialkyl glycerol tetraethers, fractional abundance IIIa; Branched Glycerol dialkyl glycerol tetraethers, fractional abundance IIIb; Caldarchaeol isomer, fractional abundance; Congo_River; Crenarchaeol isomer, fractional abundance; Cyclization ratio of branched tetraethers; DATE/TIME; Methylation index of dominant branched tetraethers; MULT; Multiple investigations; Ratio; Standard deviation
    Type: Dataset
    Format: text/tab-separated-values, 884 data points
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  • 10
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    PANGAEA
    In:  Supplement to: Hemingway, Jordon D; Schefuß, Enno; Spencer, Robert GM; Dinga, Bienvenu Jean; Eglinton, Timothy Ian; McIntyre, Cameron; Galy, Valier V (2017): Hydrologic controls on seasonal and inter-annual variability of Congo River particulate organic matter source and reservoir age. Chemical Geology, 466, 454-465, https://doi.org/10.1016/j.chemgeo.2017.06.034
    Publication Date: 2023-01-13
    Description: We present dissolved organic carbon (DOC) concentrations, particulate organic matter (POM) composition (d13C, d15N, D14C, N/C), and particulate glycerol dialkyl glycerol tetraether (GDGT) distributions from a 34-month time-series near the mouth of the Congo River. An end-member mixing model using d13C and N/C indicates that exported POM is consistently dominated by C3 rainforest soil sources, with increasing contribution from C3 vegetation and decreasing contribution from phytoplankton at high discharge. Large C4 inputs are never observed despite covering ~ 13% of the catchment. Low and variable D14C values during 2011 [annual mean = (-148 ± 82) per mil], when discharge from left-bank tributaries located in the southern hemisphere reached record lows, likely reflect a bias toward pre-aged POM derived from the Cuvette Congolaise swamp forest. In contrast, D14C values were stable near -50 per mil between January and June 2013, when left-bank discharge was highest. We suggest that headwater POM is replaced and/or diluted by C3 vegetation and pre-aged soils during transit through the Cuvette Congolaise, whereas left-bank tributaries export significantly less pre-aged material. GDGT distributions provide further evidence for seasonal and inter-annual variability in soil provenance. The cyclization of branched tetraethers and the GDGT-0 to crenarchaeol ratio are positively correlated with discharge (r 〉=0.70; p-value 〈= 4.3 × 10**-5) due to the incorporation of swamp-forest soils when discharge from right-bank tributaries located in the northern hemisphere is high. Both metrics reach record lows during 2013, supporting our interpretation of increased left-bank contribution at this time. We conclude that hydrologic variability is a major control of POM provenance in the Congo River Basin and that tropical wetlands can be a significant POM source despite their small geographic coverage.
    Type: Dataset
    Format: application/zip, 3 datasets
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