Paleoenvironmental changes in the northern shelf of the Sea of Okhotsk during the Holocene

Sea-ice distribution and atmospheric pressure patterns in southwestern Okhotsk Sea since the Last Glacial Maximum

“…However, most diatom distribution in the Okhotsk Sea did not exhibit such notable changes during this period (e.g., Shiga and Koizumi, 2000;Shimada et al, 2004;Koizumi et al, 2003;Okazaki et al, 2005). Only relative abundance of Paralia sulcata (Ehrenberg) Cleve, typical of coastal water, was changed in core 89211 on the northern continental shelf (Gorbarenko et al, 2007a). This abundance was not observed in any other area of the Okhotsk Sea.…”

“…They belong to the member of ice flora living in waters between −1 and 3°C in temperature (Horner and Alexander, 1972) and their geographic distributions almost overlap with sea-ice distribution in the subarctic Pacific (Sancetta, 1982). In fact, the other sea-ice related diatoms, Bacterosira bathyomphala, Thalassiosira antarctica, and Thalassiosira nordenskioeldii, also appear in every layer of Okhotsk Sea core sediments except for the few layers during the late Quaternary (Shiga and Koizumi 2000;Koizumi et al, 2003;Shimada et al, 2004;Okazaki et al, 2005;Gorbarenko et al, 2007a). This indicates that seaice occasionally covered all of the Okhotsk Sea during each stage of the late Quaternary.…”

“…This abundance was not observed in any other area of the Okhotsk Sea. Furthermore, δ 18 O values of benthic foraminifera of core 89211 had rapidly become low at around 2 ka (Gorbarenko et al, 2007a). The negative δ 18 O excursion most likely resulted from the occurrence of low-salinity surface water in the northern part of Okhotsk Sea.…”

“…5b). However, it should be emphasized that core 89211 was collected from the relatively shallow depth of about 140 m (Gorbarenko et al, 2007a). It is quite likely that variations of sea-ice taxa in core 89211 reflected local geographic changes.…”

“…On the northern continental shelf (core 89211 in Fig. 1; Gorbarenko et al, 2007a), the maximal abundances of F. cylindrus and F. oceanica were identified at about 10 ka. However, the effect of sea-ice in central and southern Okhotsk Sea between 15 and 10 ka was weaker than during the LGM (cores 3, GH00-1002, and MD01-2412).…”