TY - JOUR
T1 - Late Quaternary paleoceanographic changes in the southwestern Okhotsk Sea
T2 - Evidence from geochemical, radiolarian, and diatom records
AU - Okazaki, Yusuke
AU - Takahashi, Kozo
AU - Katsuki, Kota
AU - Ono, Ayumu
AU - Hori, Joichi
AU - Sakamoto, Tatsuhiko
AU - Uchida, Masao
AU - Shibata, Yasuyuki
AU - Ikehara, Minoru
AU - Aoki, Kaori
N1 - Funding Information:
We express our appreciation to the captain, crew, and scientists on board the IMAGES WEPAMA 2001 Cruise of the R/V Marion Defresne . We thank Dr. Hodaka Kawahata for his management and financial support of the Cruise. We are grateful to Professor Tadamichi Oba for his leadership of the on-board work to collect the sediment cores. This manuscript was greatly improved by critical reviews provided by Dr. Thorsten Kiefer, Dr. Richard W. Jordan, and an anonymous reviewer. Our thanks are extended to Dr. Richard W. Jordan and Ms. Eileen S. Takahashi for English editing of the manuscript. This study was funded by the following research programs of MEXT: Grants-in-Aid-for Scientific Research B2 Project No. 10480128, B1 Project No. 13440152 and the GCMAPS program (H. Kawahata, PI). YO received a partial fund from the Professor Tatsuro Matsumoto Scholarship Fund.
PY - 2005/8
Y1 - 2005/8
N2 - High-resolution analyses of geochemical parameters (biogenic opal, calcium carbonate, organic carbon, and nitrogen) and microfossil assemblages (diatoms and radiolarians) on Core MD01-2412 clarified detailed paleoceanographic changes such as sea-ice cover and biological production in the southwestern Okhotsk Sea during the last 115 kyr. An age model of Core MD01-2412 was established based on δ18O stratigraphy, accelerator mass spectrometer (AMS) 14C, and tephrochronology. Sea-ice history reconstructed by siliceous microplankton records indicated that the present sea-ice condition was formed during the last 8 kyr. Only during Marine Isotope Stage (MIS) 2 was the duration of sea-ice cover in this region much longer than that of today (4-5 months a year). Two diatom species, Thalassionema nitzschioides and Fragilariopsis doliolus, revealed that the Soya Warm Current Water (SWCW) flowed into the Okhotsk Sea near the site of Core MD01-2412 during the last 12-14 kyr and during MIS 5a, and was associated with sea-level rise. Biological productivity rapidly increased during MIS 1, associated with sea-ice retreat. Two major increases of organic carbon (OC) contents (wt%) and Corg/N ratios were observed, and the timings of these events were 15.8-16.7 ka (Event 1) and 13.1-13.6 ka (Event 2). Corresponding to these events, the abundance of Cycladophora davisiana, an intermediate water dwelling radiolarian species, increased. This high C. davisiana abundance can be correlated to the input of terrestrial organic matter from the submerged shelf to the intermediate water. Apart from the radiolarians, the production of diatoms in the surface waters was suppressed by the development of well-stratified surface water along with sea-ice melting during the early Holocene. Diatom production increased gradually during the last 10 kyr with enhanced vertical mixing.
AB - High-resolution analyses of geochemical parameters (biogenic opal, calcium carbonate, organic carbon, and nitrogen) and microfossil assemblages (diatoms and radiolarians) on Core MD01-2412 clarified detailed paleoceanographic changes such as sea-ice cover and biological production in the southwestern Okhotsk Sea during the last 115 kyr. An age model of Core MD01-2412 was established based on δ18O stratigraphy, accelerator mass spectrometer (AMS) 14C, and tephrochronology. Sea-ice history reconstructed by siliceous microplankton records indicated that the present sea-ice condition was formed during the last 8 kyr. Only during Marine Isotope Stage (MIS) 2 was the duration of sea-ice cover in this region much longer than that of today (4-5 months a year). Two diatom species, Thalassionema nitzschioides and Fragilariopsis doliolus, revealed that the Soya Warm Current Water (SWCW) flowed into the Okhotsk Sea near the site of Core MD01-2412 during the last 12-14 kyr and during MIS 5a, and was associated with sea-level rise. Biological productivity rapidly increased during MIS 1, associated with sea-ice retreat. Two major increases of organic carbon (OC) contents (wt%) and Corg/N ratios were observed, and the timings of these events were 15.8-16.7 ka (Event 1) and 13.1-13.6 ka (Event 2). Corresponding to these events, the abundance of Cycladophora davisiana, an intermediate water dwelling radiolarian species, increased. This high C. davisiana abundance can be correlated to the input of terrestrial organic matter from the submerged shelf to the intermediate water. Apart from the radiolarians, the production of diatoms in the surface waters was suppressed by the development of well-stratified surface water along with sea-ice melting during the early Holocene. Diatom production increased gradually during the last 10 kyr with enhanced vertical mixing.
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U2 - 10.1016/j.dsr2.2005.07.007
DO - 10.1016/j.dsr2.2005.07.007
M3 - Article
AN - SCOPUS:33644512067
VL - 52
SP - 2332
EP - 2350
JO - Deep-Sea Research Part II: Topical Studies in Oceanography
JF - Deep-Sea Research Part II: Topical Studies in Oceanography
SN - 0967-0645
IS - 16-18
ER -