Global Biogeochemical Cycles (GLOBAL BIOGEOCHEM CY )

Publisher: American Geophysical Union, American Geophysical Union


Global Biogeochemical Cycles includes papers in the broad areas of global change involving the geosphere and biosphere. Marine, hydrologic, atmospheric, extraterrestrial, geologic, biologic, and human causes of and response to environmental change on timescales of tens, thousands, and millions of years are the purview of the journal.

Impact factor 4.53

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  • Website
    Global Biogeochemical Cycles website
  • Other titles
    Global biogeochemical cycles
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    Periodical, Internet resource
  • Document type
    Journal / Magazine / Newspaper, Internet Resource

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American Geophysical Union

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    • Authors' Pre-print on Authors own or departmental website
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    • Publisher's version/PDF must be used in Institutional Repository 6 months after publication.
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Publications in this journal

  • [Show abstract] [Hide abstract]
    ABSTRACT: Over the past decade, estimates of the atmospheric CO2 uptake by continental shelf seas were constrained within the 0.18-0.45 Pg C yr−1 range. However, most of those estimates are based on extrapolations from limited datasets of local flux measurements (n < 100). Here, we propose to derive the CO2 air-sea exchange of the shelf seas by extracting 3 · 10^6 direct surface ocean CO2 measurements from the global database SOCAT (Surface Ocean CO2 Atlas), atmospheric CO2 values from GLOBALVIEW and calculating gas transfer rates using readily available global temperature, salinity and wind speed fields. We then aggregate our results using a global segmentation of the shelf in 45 units and 152 sub-units to establish a consistent regionalized CO2 exchange budget at the global scale. Within each unit, the data density determines the spatial and temporal resolutions at which the air-sea CO2 fluxes are calculated and range from a 0.5 degree resolution in the best surveyed regions to a whole unit resolution in areas where data coverage is limited. Our approach also accounts, for the first time, for the partial sea ice cover of polar shelves. Our new regionalized global CO2 sink estimate of 0.19 ± 0.05 Pg C yr−1 falls in the low end of previous estimates. Reported to an ice-free surface area of 22 · 106 km2, this value yields a flux density of 0.7 mol C m−2 yr−1, ~40% more intense than that of the open ocean. Our results also highlight the significant contribution of Arctic shelves to this global CO2 uptake (0.07 Pg C yr−1).
    Global Biogeochemical Cycles 10/2014; 28:1199-1214.
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    ABSTRACT: Dissolved cobalt (DCo; < 0.2μm; 14 to 93 pM) and the apparent particulate cobalt (PCo; > 0.2μm; < 1 to 15 pM) were determined in the upper water-column (< 1000 m) of the Western Atlantic Ocean along the GEOTRACES-A02 section (64°N to 50°S). The lowest DCo concentrations, typical of a nutrient-type distribution were observed in surface waters of the subtropical domains. Strong linear relationships between DCo and phosphate (P) as well as meridional gradients of decreasing DCo from high latitudes were characterized and both linked to the Co biological requirement. External sources such as the Amazon and the atmospheric deposition were found to contribute significantly (> 10%) to the DCo stock of the mixed layer in the equatorial and north subtropical domains. Biotic and abiotic processes as well as the physical terms involved in the biogeochemical cycle of Co were defined and estimated. This allowed establishing the first global budget of DCo for the upper 100 m in the Western Atlantic. The biological DCo uptake flux was the dominant sink along the section, as reflected by the overall nutrient-type behavior of DCo. The regeneration varied widely vary within the different biogeochemical domains, accounting for 10% of the DCo-uptake rate in the subarctic gyre and for up to 85% in southern subtropical domain. These findings demonstrated that the regeneration is likely the prevailing source of DCo in the surface waters of the Western Atlantic, except in the subpolar domains where physically-driven sources can sustain the DCo biological requirement.
    Global Biogeochemical Cycles 10/2014;
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    ABSTRACT: We compared carbon (C), nitrogen (N), and phosphorus (P) concentrations in atmospheric deposition, runoff, and soils with microbial respiration [dehydrogenase (DHA)] and ecoenzyme activity (EEA) in an ombrotrophic bog and a minerotrophic fen to investigate the environmental drivers of biogeochemical cycling in peatlands at the Marcell Experimental Forest in northern Minnesota, USA. Ecoenzymatic stoichiometry was used to construct models for C use efficiency (CUE) and decomposition (M), and these were used to model respiration (Rm). Our goals were to determine the relative C, N, and P limitations on microbial processes and organic matter decomposition, and to identify environmental constraints on ecoenzymatic processes. Mean annual water, C, and P yields were greater in the fen, while N yields were similar in both the bog and fen. Soil chemistry differed between the bog and fen, and both watersheds exhibited significant differences among soil horizons. DHA and EEA differed by watersheds and soil horizons, CUE, M, and Rm differed only by soil horizons. C, N, or P limitations indicated by EEA stoichiometry were confirmed with orthogonal regressions of ecoenzyme pairs and enzyme vector analyses, and indicated greater N and P limitation in the bog than in the fen, with an overall tendency toward P-limitation in both the bog and fen. Ecoenzymatic stoichiometry, microbial respiration, and organic matter decomposition were responsive to resource availability and the environmental drivers of microbial metabolism, including those related to global climate changes.
    Global Biogeochemical Cycles 08/2014; 120(1-3):203-224.
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    ABSTRACT: The emissions of carbon dioxide (CO2) from inland waters are substantial on a global scale. Yet, the fundamental question remains open which proportion of these CO2 emissions is induced by sunlight via photochemical mineralization of dissolved organic carbon (DOC), rather than by microbial respiration during DOC decomposition. Also, it is unknown on larger spatial and temporal scales how photochemical mineralization compares to other C fluxes in the inland water C cycle. We combined field and laboratory data with atmospheric radiative transfer modeling to parameterize a photochemical rate model for each day of the year 2009, for 1086 lakes situated between latitudes from 55 to 69°N in Sweden. The sunlight-induced production of dissolved inorganic carbon (DIC) averaged 3.8 ± 0.04 g C m-2 yr-1, which is a flux comparable in size to the organic carbon burial in the lake sediments. Countrywide, 151 ± 1 kt C yr-1 was produced by photochemical mineralization, corresponding to about 12% of total annual mean CO2 emissions from Swedish lakes. With a median depth of 3.2 m, the lakes were generally deep enough that incoming, photochemically active photons were absorbed in the water column. This resulted in a linear positive relationship between DIC photoproduction and the incoming photon flux, which correspond to the absorbed photons. Therefore, the slope of the regression line represents the wavelength- and depth-integrated apparent quantum yield of DIC photoproduction. We used this relationship to obtain a first estimate of DIC photoproduction in lakes and reservoirs worldwide. Global DIC photoproduction amounted to 13 and 35 Mt C yr-1 under overcast and clear sky, respectively. Consequently, these directly sunlight-induced CO2 emissions contribute up to about one tenth to the global CO2 emissions from lakes and reservoirs, corroborating that microbial respiration contributes a substantially larger share than formerly thought, and generate annual C fluxes similar in magnitude to the C burial in natural lake sediments worldwide.
    Global Biogeochemical Cycles 01/2014;