Browsing by Author "Seki, O"

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    Dust deposition tracks late-Holocene shifts in monsoon activity and the increasing role of human disturbance in the Puna-Altiplano, northwest Argentina
    (SAGE, 2020-04-01) Hooper, J; Marx, SK; May, JH; Lupo, LC; Kulemeyer, JJ; Pereira, EdlÁ; Seki, O; Heijnis, H; Child, DP; Gadd, PS; Zawadzki, A
    The Puna-Altiplano plateau represents a regionally significant dust source, which is critically located at the nexus between the tropical and sub-polar synoptic systems that dominate the South American climate. Dust emissions in this region would therefore be expected to be sensitive to changes in these systems, in particular the strength and position of the South American Summer Monsoon (SASM). Here, we present a late-Holocene multi-proxy study where changes in dust flux, reconstructed from a high-altitude peat mire, are examined in light of climate variability and human impacts. Results show that for most the 4300 cal. yr BP record, dust flux sensitively tracked changes in SASM activity. Prior to 2600 cal. yr BP relatively high dust flux implies dry conditions prevailed across the Puna-Altiplao in association with reduced SASM activity. The chemistry of dust deposited at this time matched the large endorheic basins on the Puna, which host ephemeral lakes and terminal fans, indicating these were actively supplying dust to the airstream. After 2600 cal. yr BP, SASM activity increased while dust flux decreased and the dust chemistry changed, collectively implying the shutting down of the Puna-Altiplano as a significant dust source. Dust flux increased after 1000 cal. yr BP during the ‘Medieval Warm Period’, associated with a return to drier conditions and reactivation of dust sources across the endorheic basins of the Puna. Natural variability in dust flux was dwarfed, however, by the very significant increase in flux after 400 cal. yr BP following Spanish Colonisation and associated changing landuse practices. This finding attests to the globally significant role of humans on dust emissions. © 2020 by SAGE Publications
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    Reconstructing atmospheric particulate loads over the north-western Pacific Ocean during the mid to late Holocene: volcanism, dust and human perturbation of regional aerosol loads/composition
    (Australasian Quaternary Association Inc., 2022-12-06) Marx, SK; Hooper, J; Irino, T; Seki, O; Stromsoe, N; Saunders, KM; Zawadzki, A; Dosseto, A; Jacobson, GE
    Atmospheric particulate transport over the North Pacific Ocean is known to be significant for regional biogeochemical processes and climate. For example, dust aerosol is known to fertilize phytoplankton, increasing the effectiveness of the biological C pump. Despite its importance, there has been little work tracing the changing sources and relative loads of particulate aerosols in this key region over the Holocene. The deserts of northern East Asia are the 2nd largest global dust source, while the eastern extent of East Asia forms part of the Pacific ring of fire, indicating tephra forms a significant, albeit episodic component of atmospheric particulate loads. Critically, East Asia has also undergone a significant transformation over recent decades, with widespread agricultural intensification and a massive increase in industrial activity, especially following China’s Great Leap Forward from late 1950s. This has likely perturbed regional atmospheric aerosol characteristics. In this study, we use peat mires from the Daisetsuzan Mountains in central Hokkaido, Japan, to reconstruct the history of atmospheric particulate deposition over the mid to late Holocene. Results show that over the past 4 kyr mineral flux was relatively low and dominated by dust input from mainland China, as evidenced by the rare earth element (REE) and eNd composition of sediments deposited in the mire. Within the last millennium, particulate fluxes changed more significantly, with the deposition of at least two major tephras. Further dramatic changes are recorded in the very top sections of the peat mire, where Chinese dust input becomes more geochemically significant. At the same time, the onset of nascent particulate matter is recorded by increasing concentrations of ‘industrial’ metals such as Pb and Cu. Collectively, this demonstrates the vast scale of human perturbation of atmospheric particulate, even within a region where the atmosphere is loaded with ‘natural’ particulate aerosol.
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    Reconstructing atmospheric particulate loads over the north-western Pacific Ocean during the mid to late Holocene: volcanism, dust and human perturbation of regional aerosol loads/composition.
    (Australasian Quaternary Association, 2022-12-06) Marx, SK; Hooper, J; Irino, T; Seki, O; Stromsoe, N; Saunders, KM; Zawadzki, A; Dosseto, A; Jacobson, GE
    Atmospheric particulate transport over the North Pacific Ocean is known to be significant for regional biogeochemical processes and climate. For example, dust aerosol is known to fertilize phytoplankton, increasing the effectiveness of the biological C pump. Despite its importance, there has been little work tracing the changing sources and relative loads of particulate aerosols in this key region over the Holocene. The deserts of northern East Asia are the 2nd largest global dust source, while the eastern extent of East Asia forms part of the Pacific ring of fire, indicating tephra forms a significant, albeit episodic component of atmospheric particulate loads. Critically, East Asia has also undergone a significant transformation over recent decades, with widespread agricultural intensification and a massive increase in industrial activity, especially following China’s Great Leap Forward from late 1950s. This has likely perturbed regional atmospheric aerosol characteristics. In this study, we use peat mires from the Daisetsuzan Mountains in central Hokkaido, Japan, to reconstruct the history of atmospheric particulate deposition over the mid to late Holocene. Results show that over the past 4 kyr mineral flux was relatively low and dominated by dust input from mainland China, as evidenced by the rare earth element (REE) and eNd composition of sediments deposited in the mire. Within the last millennium, particulate fluxes changed more significantly, with the deposition of at least two major tephras. Further dramatic changes are recorded in the very top sections of the peat mire, where Chinese dust input becomes more geochemically significant. At the same time, the onset of nascent particulate matter is recorded by increasing concentrations of ‘industrial’ metals such as Pb and Cu. Collectively, this demonstrates the vast scale of human perturbation of atmospheric particulate, even within a region where the atmosphere is loaded with ‘natural’ particulate aerosol.