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    Fate of rising methane bubbles in stratified waters: How much methane reaches the atmosphere? (2006)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Oceans, 111 . C09007.
    Details
    Publication Date: 2018-04-19
    Description: There is growing concern about the transfer of methane originating from water bodies to the atmosphere. Methane from sediments can reach the atmosphere directly via bubbles or indirectly via vertical turbulent transport. This work quantifies methane gas bubble dissolution using a combination of bubble modeling and acoustic observations of rising bubbles to determine what fraction of the methane transported by bubbles will reach the atmosphere. The bubble model predicts the evolving bubble size, gas composition, and rise distance and is suitable for almost all aquatic environments. The model was validated using methane and argon bubble dissolution measurements obtained from the literature for deep, oxic, saline water with excellent results. Methane bubbles from within the hydrate stability zone (typically below ∼500 m water depth in the ocean) are believed to form an outer hydrate rim. To explain the subsequent slow dissolution, a model calibration was performed using bubble dissolution data from the literature measured within the hydrate stability zone. The calibrated model explains the impressively tall flares (〉1300 m) observed in the hydrate stability zone of the Black Sea. This study suggests that only a small amount of methane reaches the surface at active seep sites in the Black Sea, and this only from very shallow water areas (〈100 m). Clearly, the Black Sea and the ocean are rather effective barriers against the transfer of bubble methane to the atmosphere, although substantial amounts of methane may reach the surface in shallow lakes and reservoirs.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/2005JC003183
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Pleistocene variability of the Subtropical Convergence at East Tasman Plateau - Evidence from planktonic foraminiferal Mg/Ca (ODP Site 1172A) (2006)
    AGU (American Geophysical Union)
    In:  Geochemistry, Geophysics, Geosystems, 7 (4). Q04P11.
    Details
    Publication Date: 2018-01-31
    Description: Combined measurements of Mg/Ca and stable oxygen isotopes in tests of the planktonic foraminifer G. bulloides from Ocean Drilling Program (ODP) Site 1172A (East Tasman Plateau) allowed us to reconstruct sea surface temperature (SSTMg/Ca), sea surface salinity (SSS), and hence variations in the Subtropical Convergence (STC) in the southwestern Tasman Sea over the last four major glacial-interglacial changes. During interglacials the commonly enhanced SSTMg/Ca and SSS correspond to a lowered marine productivity and a lowered terrigenous flux, implying that the STC separating cool, high-nutrient Subantarctic Surface Water from warm, saline, oligotrophic Subtropical Surface Water and hence the band of zonal westerlies responsible for the eolian dust flux were located south of East Tasman Plateau. The warm East Australian Current was well established during warm periods and propagated far south. During glacial times, SSTMg/Ca and SSS were lower, while both marine productivity and eolian flux increased. Such conditions prevailed during glacial Marine Isotope Stages MIS 12, MIS 10, and to a lesser degree MIS 6 and implied the extended northward influence of Subantarctic SurfaceWater and a shift of the STC to 〈44�S. The overall climatic signal at Site 1172A appears to be largely attenuated when compared to published climate records from comparable latitudes to the west and to the east. SSTMg/Ca amplitudes were more pronounced in the subantarctic Indian Ocean and at Chatham Rise. They exhibit a consistent pattern suggesting that latitudinal shifts of the STC occurred synchronously in the subantarctic Indian Ocean and at Chatham Rise but were largely damped at East Tasman Plateau due to the influence of the East Australian Current.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/2005GC000984
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    OceanRep: Article in a Scientific Journal - peer-reviewed
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