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| Titel |
Intensification of the oxygen minimum zone in the Okhotsk Sea during the Preboreal interval (11.4-10 ka) |
| VerfasserIn |
Natalia V. Bubenshchikova, Dirk Nürnberg, Ralf Tiedemann |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250037620
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| Zusammenfassung |
| The Okhotsk Sea is characterized by production the oxygenated Okhotsk Sea Intermediate
Water (OSIW: 200-800 m), driven mainly by brine rejection on the northern and western
shelves during seasonal sea ice formation. In the Okhotsk Sea, an oxygen minimum zone
(OMZ) appears as a layer with oxygen contents 0.3-1.5 ml l-1 between  750 and 1500 m
water depths mainly because of a combination of high primary productivity, predominant
ventilation of the upper 500 m of OSIW, an inflow of oxygen-depleted intermediate water
mass from the North Pacific and regional topography. During glacial periods, the
intermediate water mass oxygenation appears to have strengthened in the Okhotsk Sea due
to increased production of the oxygenated OSIW. The intermediate water mass
oxygenation was reduced during glacial terminations and interglacials mainly because of
oxidation of a large amount of organic matter in sediments and intensification of the
OMZ.
Recently, we reconstructed variations of the Okhotsk Sea OMZ over the last
46-130 ka basing on the downcores changes of the Oxic, Suboxic and Dysoxic
benthic foraminiferal indicator groups identified following Kaiho [1] in four sediment
cores: LV28-2-4, LV28-43-5, LV28-40-5 and MD01-2415 [2, 3]. The KOMEX cores
LV28-2-4 and LV28-40-5 were recovered from the eastern Sakhalin slope at water
depths of 1265 and 1312 m, and core LV28-43-5 was taken from the southwestern
Kamchatka slope at water depth of 839 m during the V28 cruise of the R/V Akademik
M.A. Lavrentyev in 1998. Cores LV28-2-4, LV28-40-5 and LV28-43-5 cover 46,
78 and 52 ka, respectively [2]. The IMAGES core MD01-2415 was collected on
the northern continental slope at water depth 822 m during the WEPAMA 2001
cruise of the R/V Marion Dufresne. A 46.23 m-long sediment core MD01-2415
represents the last 1.1 million years [4]. Benthic foraminifera were investigated in
the upper 8.30 m of the core MD01-2415 sediments, which cover the last 130 ka
[3].
Our results indicated that during the Preboreal interval (11.4-10 ka) the Dysoxic benthic
foraminifera (mainly Bolivina spp.) were widely distributed in sediments between 822 to
1312 m water depths suggesting pronounced decrease of the intermediate water oxygenation
and intensification of OMZ in the Okhotsk Sea [2, 3]. It can be estimated that oxygen content
near the core sites between 822 to 1312 m water depths dropped by factor two or three in the
Preboreal ( |
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