Responses of ocean biogeochemistry to atmospheric supply of lithogenic and pyrogenic iron-containing aerosols

Ito, Akinori; Ye, Ying; Yamamoto, Akitomo; Watanabe, Michio; Aita, Maki Noguchi

doi:10.1017/s0016756819001080

Cited by 33 publications

(45 citation statements)

References 95 publications

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“…However, due to their spatiotemporal distribution and higher fractional Fe solubility (Chuang et al, 2005;Guieu et al, 2005;Sedwick et al, 2007;Sholkovitz et al, 2009), combustion aerosols may play an important role in influencing the fluxes of DFe over oceanic regions with little dust input, downwind from industrialized regions, and/or near major shipping routes (Ito et al, 2019a). Furthermore, an ocean biogeochemistry model suggests that pyrogenic Fe-containing aerosols stimulate the marine productivity more efficiently than lithogenic aerosols, especially in the Pacific and Southern Ocean (Ito et al, 2019). Because anthropogenic aerosols are small in size (i.e., < 1 μm) and found predominantly within the accumulation mode, the total amount collected on the filters is also small, complicating efforts to characterize the oxidation forms and mineralogy of aerosol Fe.…”

Section: Anthropogenic and Biomass Burning Aerosols: Fe Solubility Anmentioning

confidence: 99%

Perspective on identifying and characterizing the processes controlling iron speciation and residence time at the atmosphere-ocean interface

et al. 2019

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It is well recognized that the atmospheric deposition of iron (Fe) affects ocean productivity, atmospheric CO 2 uptake, ecosystem diversity, and overall climate. Despite significant advances in measurement techniques and modeling efforts, discrepancies persist between observations and models that hinder accurate predictions of processes and their global effects. Here, we provide an assessment report on where the current state of knowledge is and where future research emphasis would have the highest impact in furthering the field of Fe atmosphere-ocean biogeochemical cycle. These results were determined through consensus reached by diverse researchers from the oceanographic and atmospheric science communities with backgrounds in laboratory and in situ measurements, modeling, and remote sensing. We discuss i) novel measurement methodologies and instrumentation that allow detection and speciation of different forms and oxidation states of Fe in deliquesced mineral aerosol, cloud/rainwater, and seawater; ii) oceanic models that treat Fe cycling with several external sources and sinks, dissolved, colloidal, particulate, inorganic, and organic ligand-complexed forms of Fe, as well as Fe in detritus and phytoplankton; and iii) atmospheric models that consider natural and anthropogenic sources of Fe, mobilization of Fe in mineral aerosols due to the dissolution of Fe-oxides and Fe-substituted aluminosilicates through proton-promoted, organic ligand-promoted, and photo-reductive mechanisms. In addition, the study identifies existing challenges and disconnects (both fundamental and methodological) such as i) inconsistencies in Fe nomenclature and the definition of bioavailable Fe between oceanic and atmospheric disciplines, and ii) the lack of characterization of the processes controlling Fe speciation and residence time at the atmosphere-ocean interface. Such challenges are undoubtedly caused by extremely low concentrations, short lifetime, and the myriad of physical, (photo)chemical, and biological processes affecting global biogeochemical cycling of Fe. However, we also argue that the historical division (separate treatment of Fe biogeochemistry in oceanic and atmospheric disciplines) and the classical funding structures (that often create obstacles for transdisciplinary collaboration) are also hampering the advancement of knowledge in the field. Finally, the study

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Section: Anthropogenic and Biomass Burning Aerosols: Fe Solubility Anmentioning

confidence: 99%

Perspective on identifying and characterizing the processes controlling iron speciation and residence time at the atmosphere-ocean interface

et al. 2019

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“…In addition, emissions of dissolved Fe (DFe) and dissolved P (DP) from anthropogenic combustion and biomass burning processes can contribute significantly to the atmospheric inputs into the ocean (e.g., Barkley et al, 2019;Matsui et al, 2018). However, the aerosols from natural and combustion sources tend to be deposited in different regions of the oceans; for example, the subtropical North Atlantic Ocean and the Arabian Sea receive the majority of Fe originated from dust aerosols, in contrast to the Pacific and Southern oceans where the Fe-containing combustion aerosols are mainly deposited (Ito et al, 2019b).…”

Section: Introductionmentioning

confidence: 99%

“…On the other hand, a number of studies argue that anthropogenic N deposition is equally important for ocean biogeochemistry (Duce et al, 2008;Wang et al, 2015a). The essential role of iron in oceanic productivity is, however, well established (Tagliabue et al, 2017) and currently routinely included in biogeochemistry modelling studies (e.g., Aumont and Bopp, 2006;Hajima et al, 2019;Ito et al, 2019b;Moore et al, 2001;Tagliabue et al, 2014Tagliabue et al, , 2016. Nitrogen fixation rates are also sensitive to atmospheric Fe inputs (Camarero and Catalan, 2012;Schulz et al, 2012) since N2-fixing species (diazotrophs) have elevated Fe requirements.…”

Section: Introductionmentioning

confidence: 99%

An explicit estimate of the atmospheric nutrient impact on global oceanic productivity

Myriokefalitakis¹,

Gröger²,

Hieronymus³

et al. 2020

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Abstract. State-of-the-art global nutrient deposition fields are here coupled to the biogeochemistry model PISCES to investigate the effect on ocean biogeochemistry in the context of atmospheric forcings for preindustrial, present, and future periods. Present-day atmospheric deposition fluxes of inorganic N, Fe, and P over the global ocean are accounted equal to ~40 Tg-N yr−1, ~0.28 Tg-Fe yr−1 and ~0.10 Tg-P yr−1. The resulting globally integrated primary production of roughly 47 Pg-C yr−1 is well within the range of satellite-based estimates and other modeling predictions. Preindustrial atmospheric nutrient deposition fluxes are lower compared to present-day (~51 %, ~36 %, and ~40 % for N, Fe, and P, respectively), resulting here in a lower marine primary production by ~3 % globally. Future changes in air pollutants under the RCP8.5 scenario result in a modest decrease of the bioaccessible nutrients input into the global ocean compared to present-day (~13 %, ~14 % and ~20 % for N, Fe and P, respectively), without significantly affecting the projected primary production in the model. The global mean nitrogen-fixation rates changed only marginally from preindustrial to future conditions (111 ± 0.6 Tg-N yr−1). With regard to the atmospheric inputs to the ocean, sensitivity model simulations indicate that the contribution of nutrients' organic fraction results in an increase in primary production by about 2.4 %. This estimate is almost equal to the effect of emissions and atmospheric processing on the oceanic biogeochemistry since preindustrial times in the model when only the inorganic fraction of the nutrients is considered. Although the impact of the atmospheric organic nutrients may imply a relatively weak response of marine productivity on a global scale, stronger regional effects up to ~20 % are calculated in the oligotrophic subtropical gyres. Overall, this work provides a first explicit assessment of the contribution of the organic forms of atmospheric nutrients, highlighting the importance of their representation in biogeochemistry models and thus the oceanic productivity estimates.

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“…However, there is evidence that the dissolved organic nitrogen (DON) inputs (e.g., from rivers along the coasts) can likewise be also efficiently utilized (e.g., Aumont et al, 2015). In the atmosphere, the global organic nitrogen (ON) cycle has been demonstrated to have a strong (∼ 45 %) anthropogenic component (Kanakidou et al, 2012). Kanakidou et al (2016) calculated that 20 %-25 % of the nitrogen deposition is in the form of ON; overall, with DON deposition, this is about 25 % of the total dissolved nitrogen deposition to the global ocean.…”

mentioning

confidence: 99%

“…However, the aerosols from natural and combustion sources tend to be deposited in different regions of the oceans. For example, the subtropical North Atlantic Ocean and the Arabian Sea receive the majority of Fe that has originated from natural dust aerosols, in contrast to the Pacific and Southern Ocean where the Fe-containing combustion aerosols play a more important role compared to atmospheric dust (Ito et al, 2019b).…”

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confidence: 99%

An explicit estimate of the atmospheric nutrient impact on global oceanic productivity

et al. 2020

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Abstract. State-of-the-art global nutrient deposition fields are coupled here to the Pelagic Interactions Scheme for Carbon and Ecosystem Studies (PISCES) biogeochemistry model to investigate their effect on ocean biogeochemistry in the context of atmospheric forcings for pre-industrial, present, and future periods. PISCES, as part of the European Community Earth system model (EC-Earth) model suite, runs in offline mode using prescribed dynamical fields as simulated by the Nucleus for European Modelling of the Ocean (NEMO) ocean model. Present-day atmospheric deposition fluxes of inorganic N, Fe, and P into the global ocean account for ∼ 40 Tg N yr−1, ∼ 0.28 Tg Fe yr−1, and ∼ 0.10 Tg P yr−1. Pre-industrial atmospheric nutrient deposition fluxes are lower compared to the present day (∼ 51 %, ∼ 36 %, and ∼ 40 % for N, Fe, and P, respectively). However, the overall impact on global productivity is low (∼ 3 %) since a large part of marine productivity is driven by nutrients recycled in the upper ocean layer or other local factors. Prominent changes are, nevertheless, found for regional productivity. Reductions of up to 20 % occur in oligotrophic regions such as the subtropical gyres in the Northern Hemisphere under pre-industrial conditions. In the subpolar Pacific, reduced pre-industrial Fe fluxes lead to a substantial decline of siliceous diatom production and subsequent accumulation of Si, P, and N, in the subpolar gyre. Transport of these nutrient-enriched waters leads to strongly elevated production of calcareous nanophytoplankton further south and southeast, where iron no longer limits productivity. The North Pacific is found to be the most sensitive to variations in depositional fluxes, mainly because the water exchange with nutrient-rich polar waters is hampered by land bridges. By contrast, large amounts of unutilized nutrients are advected equatorward in the Southern Ocean and North Atlantic, making these regions less sensitive to external nutrient inputs. Despite the lower aerosol N : P ratios with respect to the Redfield ratio during the pre-industrial period, the nitrogen fixation decreased in the subtropical gyres mainly due to diminished iron supply. Future changes in air pollutants under the Representative Concentration Pathway 8.5 (RCP8.5) emission scenario result in a modest decrease of the atmospheric nutrients inputs into the global ocean compared to the present day (∼ 13 %, ∼ 14 %, and ∼ 20 % for N, Fe, and P, respectively), without significantly affecting the projected primary production in the model. Sensitivity simulations further show that the impact of atmospheric organic nutrients on the global oceanic productivity has turned out roughly as high as the present-day productivity increase since the pre-industrial era when only the inorganic nutrients' supply is considered in the model. On the other hand, variations in atmospheric phosphorus supply have almost no effect on the calculated oceanic productivity.

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Responses of ocean biogeochemistry to atmospheric supply of lithogenic and pyrogenic iron-containing aerosols

Cited by 33 publications

References 95 publications

Perspective on identifying and characterizing the processes controlling iron speciation and residence time at the atmosphere-ocean interface

Perspective on identifying and characterizing the processes controlling iron speciation and residence time at the atmosphere-ocean interface

An explicit estimate of the atmospheric nutrient impact on global oceanic productivity

An explicit estimate of the atmospheric nutrient impact on global oceanic productivity

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