Paleoceanography of the Oyashio Area during the Last 20,000 Years Based on Benthic Foraminifera.

Ohkushi, Ken’ichi; Nemoto, Naoki; Nakamura, Toshio; Tsukawaki, Shinji

doi:10.4116/jaqua.39.427

Cited by 7 publications

(7 citation statements)

References 20 publications

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“…The earlymid Holocene assemblages occurred in the silty sediments (litho-facies 3). Our results are similar to faunal changes reported for nearby sites by Ohkushi et al (2000 indicating the same bottom water change in the Oyashio region, south of Hokkaido.…”

Section: Change Of Bottom Water Conditionssupporting

confidence: 94%

Change of bottom water conditions at intermediate depths of the Oyashio region, NW Pacific over the past 20,000 yrs

Ikehara

Ohkushi

Shibahara

et al. 2006

Global and Planetary Change

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Section: Change Of Bottom Water Conditionssupporting

confidence: 94%

Change of bottom water conditions at intermediate depths of the Oyashio region, NW Pacific over the past 20,000 yrs

Ikehara

Ohkushi

Shibahara

et al. 2006

Global and Planetary Change

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“…1; Table 1). These samples were recovered from water depths between 958 and 2350 m. It has been widely observed that the planktonic foraminiferal test is absent in surface sediment of the northern part of the mixed water region, even above the lysocline (Kallel et al, 1988;Oba 1991Oba , 1993Ohkushi et al, 2000) perhaps owing to high biological productivity. The surface sediments of St. 21, 6B, and 1 contain no planktonic foraminifera, therefore, we picked G. bulloides from early Holocene sections of these cores.…”

Section: Holocene Sediment Samplesmentioning

confidence: 99%

Sea surface temperature record off central Japan since the Last Glacial Maximum using planktonic foraminiferal Mg/Ca thermometry

Sagawa

Toyoda

Oba

2005

J Quaternary Science

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Sagawa, T., Toyoda, K. and Oba, T. 2005. Sea surface temperature record off central Japan since the Last Glacial Maximum using planktonic foraminiferal Mg/Ca thermometry.ABSTRACT: We conducted paired measurements of the Mg/Ca ratio and 18 O of planktonic foraminifera, Globigerina bulloides, from a sediment core (MD01-2420) off central Japan in the northwest Pacific, to reconstruct current movements since the Last Glacial Maximum (LGM). These methods make it possible to determine the magnitude and timing of the sea surface temperature (SST) changes and to reconstruct the variations of the past seawater 18 O ( 18 Ow) off central Japan. The amplitude of Mg/Ca-based SST changes between the Holocene and the LGM was about 10 C. The strong resemblance of the SSTs estimated from both methods, Mg/Ca-based and 18 O-based, suggests that the SST changes were caused primarily by latitudinal displacement of the KuroshioOyashio currents and no distinct change in the carbonate dissolution of the core. The southward migration of the water mass was 5-6 in latitude at the LGM. The values for regional 18 Ow changes, which were obtained by subtracting the ice volume contribution from the calculated 18 Ow, describe the millennial-scale water mass migration over the last 30 kyr.

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“…The ages of the four cores (St. 21, St. 5, LM-8 and CH08-04) rely on previous publications (Labeyrie et al, 1990;Yamane and Oba, 1999;Ohkushi et al, 2000) in which the ages were determined by -counting and AMS 14 C dating using planktonic Foraminifera, oxygen isotope stage boundaries and correlation with other well-dated cores. Eight AMS 14 C dates and one ash layer with an eruption age that is well known (Machida and Arai, 1992) are used for the age determination of the IMAGES core (MD01-2421).…”

Section: O Of Four Previous Cores and A New Images Corementioning

confidence: 99%

“…1b), off central Japan in the Kuroshio Current region (Chinzei et al, 1987;Labeyrie et al, 1990;Takemoto and Oda, 1997) and off Hokkaido in the Oyashio Current region (Kallel et al, 1988;Ohkushi et al, 2000). One core (LM-8) was recovered from the mixed water mass region between the Kuroshio and Oyashio Currents (Yamane and Oba, 1999).…”

Section: Introductionmentioning

confidence: 99%

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Sea‐surface temperature and salinity changes in the northwest Pacific since the Last Glacial Maximum

Oba

Murayama²

2004

J Quaternary Science

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Oba, T. and Murayama, M. 2004. Sea-surface temperature and salinity changes in the northwest Pacific since the Last Glacial Maximum.ABSTRACT: The oxygen isotope records of both benthic and planktonic Foraminifera in five piston cores, collected from the region between the Oyashio and Kuroshio Currents near Japan, clearly show the marked latitudinal shifts of these two currents during the past 25 kyr. Under the present hydrographic condition, a clear relationship between the sea-surface temperature (SST) and oxygen isotope differences from benthic to planktonic Foraminifera is observed in this region. Using this relationship, we find decreased SSTs of 12-13 C (maximum 15 C) in the southernmost core site at the Last Glacial Maximum (LGM), indicating the Oyashio Current shifted southward. The SSTs at the southern two core sites abruptly increased more than 10 C at 10-11 ka, suggesting the Kuroshio Current shifted northward over these sites at 10-11 ka. In contrast, the northern two core sites have remained under the influence of the cold Oyashio Current for the past 25 kyr. With the reasonable estimate of bottom-water temperature decrease of 2.5 C at the LGM, the SSTs estimated by this new method give exactly the same SST values calculated from Mg/Ca ratio of planktonic Foraminifera, allowing palaeosea-surface salinities to be reconstructed. The result suggests that the ice volume effect was 1.0 AE 0.1% at the LGM.

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Paleoceanography of the Oyashio Area during the Last 20,000 Years Based on Benthic Foraminifera.

Cited by 7 publications

References 20 publications

Change of bottom water conditions at intermediate depths of the Oyashio region, NW Pacific over the past 20,000 yrs

Change of bottom water conditions at intermediate depths of the Oyashio region, NW Pacific over the past 20,000 yrs

Sea surface temperature record off central Japan since the Last Glacial Maximum using planktonic foraminiferal Mg/Ca thermometry

Sea‐surface temperature and salinity changes in the northwest Pacific since the Last Glacial Maximum

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