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  • Springer  (3)
  • American Geophysical Union (AGU)  (1)
  • ELSEVIER SCIENCE BV  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Ethylene and methane in the upper water column of the subtropical Atlantic (1999)
    Springer
    Biogeochemistry 44 (1999), S. 73-91 
    Details
    ISSN: 1573-515X
    Keywords: Atlantic ; ethylene ; methane ; sea-air exchange
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The vertical distributions of ethylene and methane in the upper water column of the subtropical Atlantic were measured along a transect from Madeira to the Caribbean and compared with temperature, salinity, oxygen, nutrients, chlorophyll-a, and dissolved organic carbon (DOC). Methane concentrations between 41.6 and 60.7 nL L−1 were found in the upper 20 m of the water column giving a calculated average flux of methane into the atmosphere of 0.82μg m−2 h−1. Methane profiles reveal several distinct maxima in the upper 500 m of the water column and short-time variations which are presumably partly related to the vertical migration of Zooplankton. Ethylene concentrations in near surface waters varied in the range of 1.8 to 8.2 nL L−1. Calculated flux rates for ethylene into the atmosphere were in the range of 0.41 to 1.35μg m−2 h−1 with a mean of 0.83μg m−2h−2. Maximum concentrations of up to 39.2 nL L−2 were detected directly below the pycnocline in the western Atlantic. The vertical distributions of ethylene generally showed one maximum at the pycnocline (about 100 m depth) where elevated concentrations of chlorophyll-a, dissolved oxygen, and nutrients were also found; no ethylene was detected below 270 m depth. This suggests that ethylene release is mainly related to one, probably phytoplankton associated, source, while for methane, enhanced net production occurs at various depth horizons. For surface waters, a simple correlation between ethylene and chlorophyll-a or DOC concentrations could not be observed. No considerable diurnal variation was observed for the distribution and concentration of ethylene in the upper water column.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00992999
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Ethylene and methane in the upper water column of the subtropical Atlantic (1999)
    Springer
    Biogeochemistry 44 (1999), S. 73-91 
    Details
    ISSN: 1573-515X
    Keywords: Atlantic ; ethylene ; methane ; sea-air exchange
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The vertical distributions of ethylene and methane in the upper water column of the subtropical Atlantic were measured along a transect from Madeira to the Caribbean and compared with temperature, salinity, oxygen, nutrients, chlorophyll-a, and dissolved organic carbon (DOC). Methane concentrations between 41.6 and 60.7 nL L-1 were found in the upper 20 m of the water column giving a calculated average flux of methane into the atmosphere of 0.82 μg m-2 h-1. Methane profiles reveal several distinct maxima in the upper 500 m of the water column and short-time variations which are presumably partly related to the vertical migration of zooplankton. Ethylene concentrations in near surface waters varied in the range of 1.8 to 8.2 nL L-1. Calculated flux rates for ethylene into the atmosphere were in the range of 0.41 to 1.35 μg m-2 h-1 with a mean of 0.83 μg m-2 h-1. Maximum concentrations of up to 39.2 nL L-1 were detected directly below the pycnocline in the western Atlantic. The vertical distributions of ethylene generally showed one maximum at the pycnocline (about 100 m depth) where elevated concentrations of chlorophyll-a, dissolved oxygen, and nutrients were also found; no ethylene was detected below 270 m depth. This suggests that ethylene release is mainly related to one, probably phytoplankton associated, source, while for methane, enhanced net production occurs at various depth horizons. For surface waters, a simple correlation between ethylene and chlorophyll-a or DOC concentrations could not be observed. No considerable diurnal variation was observed for the distribution and concentration of ethylene in the upper water column.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006090917059
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    Paper (German National Licenses)
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  • 3
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    Deglacial to Holocene variability in surface water characteristics and major floods in the Beaufort Sea (2020)
    Springer
    In:  EPIC3Communications Earth & Environment, Springer, 1(25), pp. 1-12
    Details
    Publication Date: 2020-10-15
    Description: Surface water characteristics of the Beaufort Sea have global climate implications during the last deglaciation and the Holocene, as (1) sea ice is a critical component of the climate system and (2) Laurentide Ice Sheet meltwater discharges via the Mackenzie River to the Arctic Ocean and further, to its outflow near the deep-water source area of the Atlantic Meridional Overturning Circulation. Here we present high-resolution biomarker records from the southern Beaufort Sea. Multi-proxy biomarker reconstruction suggests that the southern Beaufort Sea was nearly ice-free during the deglacial to Holocene transition, and a seasonal sea-ice cover developed during the mid-late Holocene. Superimposed on the long-term change, two events of high sediment flux were documented at ca. 13 and 11 kyr BP, respectively. The first event can be attributed to the Younger Dryas flood and the second event is likely related to a second flood and/or coastal erosion.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 4
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    Controls on the distributions of GDGTs and n-alkane isotopic compositions in sediments of the Amazon River Basin (2022)
    ELSEVIER SCIENCE BV
    In:  EPIC3Chemical Geology, ELSEVIER SCIENCE BV, 594, pp. 120777, ISSN: 0009-2541
    Details
    Publication Date: 2022-02-26
    Description: ARTICLE INFO Keywords: Amazonia GDGT Amazon River Biomarkers Compound-specific isotopes N-Alkanes Paleoclimate proxies Plant waxes ABSTRACT Lipid biomarker proxies from terrigenous sediments have been extensively used to understand variations in paleoenvironmental conditions, but many of the mechanisms affecting these proxies during riverine transport are still poorly understood. Here, we analyze glycerol dialkyl glycerol tetraether (GDGT) distributions and n-alkane isotopic compositions of soils and sediments from the Amazon River Basin. Our dataset includes suspended sediments of the Amazon River and its main tributaries, as well as soils and sediments of the Xingu River, a large clearwater tributary draining the easternmost part of the Amazon River Basin. Our sampling design aimed at understanding the processes behind spatially distinct GDGT distributions and n-alkane isotopic signatures across lowland Amazonia. Gradual changes in the fractional abundances of isoprenoid GDGTs and in 5- and 6- methyl branched GDGT ratios in suspended sediments of the Amazon River towards its mouth suggest that riverine production is an increasingly important control on the distribution of GDGTs in the lower parts of the system, while values from the western parts are more in line with a dominant soil sourcing. In the Xingu River, indices based on the fractional abundances of branched GDGTs and long-chain n-alkanes demonstrate a strong contri- bution of terrestrial organic material during the high-water season and an important aquatic component during low-water season. Meanwhile, average stable carbon (δ13C) and hydrogen (δD) isotopic signatures of long-chain n-alkanes in soils, riverbed and suspended sediments of the Xingu River are similar and reinforce the relatively conservative behaviour of these proxies within large river systems. The average compound-specific δ13C signa- tures of sediments in the Xingu River are within the expected range for C3 vegetation and do not seem to capture the signals from the nearby deforested areas. n-Alkanes δD signals in the Xingu Basin are similar to values ob- tained in the Amazon River mouth and indicate that n-alkanes sourced from easternmost Amazonian lowlands may predominate over signals from western areas.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 5
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    Anthropogenic Perturbations Change the Quality and Quantity of Terrestrial Carbon Flux to the Coastal Ocean (2023)
    American Geophysical Union (AGU)
    In:  EPIC3Journal of Geophysical Research Biogeosciences, American Geophysical Union (AGU), 128(10), ISSN: 2169-8953
    Details
    Publication Date: 2024-04-11
    Description: Human activities have increasingly changed terrestrial particulate organic carbon (POC) export to the coastal ocean since the Industrial Age (19th century). However, the influence of human perturbations on the composition and flux of terrestrial biospheric and petrogenic POC sub-pools remains poorly constrained. Here, we examined 13C and 14C compositions of bulk POC and source-specific biomarkers (fatty acids, FA) from two nearshore sediment cores collected in the Pearl River-derived mudbelt, to determine the impacts of human perturbations of the Pearl River watershed on the burial of terrestrial POC in the coastal ocean over the last century. Our results show that although agricultural practices and deforestation during the 1930s–1950s increased C4 plant coverage in the watershed, the export fluxes of terrestrial biospheric and petrogenic POC remained rather unchanged; however, added perturbations since 1974, including increasing coal consumption, embankment and dam constructions caused massive export of both petrogenic POC and relatively fresh terrestrial biospheric POC from the river delta. Our data reveal that human activities substantially enhance the transfer of petrogenic POC and fresh biospheric POC to the coastal ocean after ca. 1974, with the latter process acting as an important sink for anthropogenic CO2.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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