Browsing by Author "Mahowald, NM"

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    Anthropogenic perturbations to the atmospheric molybdenum cycle
    (American Geophysical Union, 2021-01-28) Wong, MY; Rathod, SD; Marino, R; Li, LL; Howarth, RW; Alastuey, A; Alaimo, MG; Barraza, F; Carneiro, MC; Chellam, S; Chen, YC; Cohen, DD; Connelly, D; Dongarra, G; Gómez, D; Hand, JL; Harrison, RM; Hopke, PK; Hueglin, c; Kuang, KW; Lambert, F; Liang, J; Losno, R; Maenhaut, W; Milando, C; Monteiro, MIC; Morera-Gómez, Y; Rodríguez, S; Querol, X; Smichowski, P; Varrica, D; Xiao, YH; Xu, YJ; Mahowald, NM
    Molybdenum (Mo) is a key cofactor in enzymes used for nitrogen (N) fixation and nitrate reduction, and the low availability of Mo can constrain N inputs, affecting ecosystem productivity. Natural atmospheric Mo aerosolization and deposition from sources such as desert dust, sea-salt spray, and volcanoes can affect ecosystem function across long timescales, but anthropogenic activities such as combustion, motor vehicles, and agricultural dust have accelerated the natural Mo cycle. Here we combined a synthesis of global atmospheric concentration observations and modeling to identify and estimate anthropogenic sources of atmospheric Mo. To project the impact of atmospheric Mo on terrestrial ecosystems, we synthesized soil Mo data and estimated the global distribution of soil Mo using two approaches to calculate turnover times. We estimated global emissions of atmospheric Mo in aerosols (<10 μm in diameter) to be 23 Gg Mo yr−1, with 40%–75% from anthropogenic sources. We approximated that for the top meter of soil, Mo turnover times range between 1,000 and 1,000,000 years. In some industrialized regions, anthropogenic inputs have enhanced Mo deposition 100-fold, lowering the soil Mo turnover time considerably. Our synthesis of global observational data, modeling, and a mass balance comparison with riverine Mo exports suggest that anthropogenic activity has greatly accelerated the Mo cycle, with potential to influence N-limited ecosystems. © 2022 American Geophysical Union
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    Atmospheric iron deposition: global distribution, variability, and human perturbations
    (Annual Reviews, 2009-01) Mahowald, NM; Engelstaedter, S; Luo, CW; Sealy, A; Artaxo, P; Benitez-Nelson, C; Bonnet, S; Chen, YS; Chuang, PY; Cohen, DD; Dulac, F; Herut, B; Johansen, AM; Kubilay, N; Losno, R; Maenhaut, W; Paytan, A; Prospero, JM; Shank, LM; Siefert, RL
    Atmospheric inputs of iron to the open ocean are hypothesized to modulate ocean biogeochemistry. This review presents an integration of available observations of atmospheric iron and iron deposition, and also covers bioavailable iron distributions. Methods for estimating temporal variability in ocean deposition over the recent past are reviewed. Desert dust iron is estimated to represent 95% of the global atmospheric iron cycle, and combustion sources of iron are responsible for the remaining 5%. Humans may be significantly perturbing desert dust (up to 50%). The sources of bioavailable iron ire less well understood than those of iron, partly because we do not know what speciation of the iron is bioavailable. Bioavailable iron can derive from atmospheric processing of relatively insoluble desert dust iron or from direct emissions of soluble iron from combustion sources. These results imply that humans could be substantially impacting it-on and bioavailable iron deposition to ocean regions, but there are large uncertainties in our understanding. © 2009, Annual Reviews
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    COARSEMAP: synthesis of observations and models for coarse-mode aerosols
    (American Geophysical Union, 2017-12-11) Wiedinmyer, C; Lihavainen, H; Mahowald, NM; Alastuey, A; Albani, S; Artaxo, P; Bergametti, G; Batterman, S; Brahney, J; Duce, RA; Feng, Y; Buck, C; Ginoux, PA; Chen, Y; Guieu, C; Cohen, DD; Hand, JL; Harrison, RM; Herut, B; Ito, A; Losno, R; Gomez, D; Kanakidou, M; Landing, WM; Laurent, B; Mihalopoulos, N; Mackey, K; Maenhaut, W; Heuglin, C; Milando, C; Miller, RL; Myriokefaitakis, S; Neff, JC; Pandolfi, M; Paytan, A; Pérez, CGP; Prank, M; Prospero, JM; Tamburo, E; Varrica, D; Wong, MY; Zhang, Y
    Coarse mode aerosols influence Earth’s climate and biogeochemistry by interacting with long-wave radiation, promoting ice nucleation, and contributing important elements to biogeochemical cycles during deposition. Yet coarse mode aerosols have received less emphasis in the scientific literature. Here we present first efforts to globally synthesize available mass concentration, composition and optical depth data and modeling for the coarse mode aerosols (<10 µm) in a new project called “COARSEMAP” (http://www.geo.cornell.edu/eas/PeoplePlaces/Faculty/mahowald/COARSEMAP/). We seek more collaborators who have observational data, especially including elemental or composition data, and/or who are interested in detailed modeling of the coarse mode. The goal will be publications synthesizing data with models, as well as providing synthesized results to the wider community.