In:
Ocean Science, Copernicus GmbH, Vol. 14, No. 4 ( 2018-07-13), p. 575-588
Abstract:
Abstract. Full-depth profiles of hydrographic and geochemical
properties at the Izu–Ogasawara Trench were observed for the first time
using a CTD-CMS (conductivity–temperature–depth profiler with
carousel multiple sampling) system. Additionally, comparative samplings were
done at the northern Mariana Trench using the same methods. A well-mixed
hydrographic structure below 7000 m was observed within the Izu–Ogasawara
Trench. Seawater samples collected from this well-mixed hadal layer
exhibited constant concentrations of nitrate, phosphate, silicate, and
nitrous oxide as well as constant nitrogen and oxygen isotopic compositions
of nitrate and nitrous oxide. These results agree well with previous
observations of the Izu–Ogasawara hadal waters and deep-sea
water surrounding the Izu–Ogasawara Trench. In turn, methane concentrations and
isotopic compositions indicated spatial heterogeneity within the well-mixed
hadal water mass, strongly suggesting a local methane source within the
trench, in addition to the background methane originating from the general
deep-sea bottom water. Sedimentary compound releases, associated with
sediment re-suspensions, are considered to be the most likely mechanism for
generating this significant CH4 anomaly.
Type of Medium:
Online Resource
ISSN:
1812-0792
DOI:
10.5194/os-14-575-2018
DOI:
10.5194/os-14-575-2018-supplement
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2018
detail.hit.zdb_id:
2183769-7
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