Reconstruction of paleoceanographic changes based on the relationship between planktonic foraminiferal assemblages and water masses off Shimokita over the last 27,000 years

Azumi Kuroyanagi, Hodaka Kawahata, Ken'ichi Ohkushi

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

Planktonic foraminiferal assemblage provides the information about water mass properties. We investigate the fossil foraminiferal fauna using factor analysis to reconstruct the changes in water masses and the outflow/inflow timing of the Oyashio and Tsugaru currents across the Tsugaru Strait off Shimokita (41°33.9′N, 141°52.1′E) in the northwestern North Pacific over the last 26,900 years. In the study area, the Oyashio Current affected both surface and subsurface (below the pycnocline) waters during 26.9-15.7 thousand calendar years before present (cal. kyr BP). Vertical mixing and subsurface warming resulted from the flow of the Oyashio Current into the Japan Sea around 15.7-10.6 cal. kyr BP. The Tsugaru Current started to enter into the Pacific about 11.2-10.6 cal. kyr BP and formed two water masses condition of the surface layer under the influence of the Tsugaru and the subsurface layers of the Oyashio Current during 10.6-9.0 cal. kyr BP. The increasing of inflow of the Tsushima/Tsugaru Current enforced surface layer warming and the stratification of water column. Finally, the subsurface layer started to warm at 6.2 cal. kyr BP. The timings of outflow/inflow of the Oyashio and Tsugaru currents in this study are compatible with the results at the Japan Sea sites.

Original languageEnglish
Pages (from-to)33-42
Number of pages10
JournalFossils
Issue number79
Publication statusPublished - 2006 Mar 1
Externally publishedYes

Keywords

  • Factor analysis
  • Fossil assemblage
  • IMAGES core
  • Planktonic foraminifera
  • Water mass

ASJC Scopus subject areas

  • Palaeontology

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