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

Climate and vegetation in Hokkaido, northern Japan, since the LGM: Pollen records from core GH02-1030 off Tokachi in the northwestern Pacific

“…Visual observation and soft X-ray radiographs revealed no clear erosional surface in the core, and even very thin sand layers were found in the lower part ( Fig. 2; Ikehara et al, 2006).…”

“…Previous paleoceanographic studies of this core have examined its lithology, age-depth model, and benthic foraminifera (Ikehara et al, 2006); assemblages of benthic foraminifera (Shibahara et al, 2007); Mg/Ca ratio and oxygen isotopes of planktonic and benthic foraminifera (Sagawa and Ikehara, 2008) and alkenone sea surface temperatures and terrestrial biomarkers (Inagaki et al, 2009). …”

“…Columnar section of core GH02-1030 with ages of benthic and planktonic foraminifera (afterIkehara et al, 2006). 4.3. Zone T3 (2.02-0.3 m in depth; 10-0.5 ka)…”

Characteristics of sediments and their dispersal systems along the shelf and slope of an active forearc margin, eastern Hokkaido, northern Japan

“…13). The low rate of mass accumulation reflects the low dry bulk density (0.4 g cm − 3 ) of the surface sediments, which may in turn reflect high levels of diatom productivity within the Oyashio Current during the Holocene (Shiomoto et al, 1994;Narita et al, 2002;Ikehara et al, 2006). Assuming that the sedimentation area on the slope is 1000-2000 km 2 , the sedimentation rate is calculated to be 0.24-0.48 Mt y − 1 .…”

A new local marine reservoir correction for the last deglacial period in the Sanriku region, northwestern North Pacific, based on radiocarbon dates from the Towada-Hachinohe (To-H) tephra

“…Upwelling of the old seawater in the subarctic North Pacific makes large ΔR in this region. As the circulation of surface and intermediate water in the NW Pacific changed between the last glacial maximum-last deglaciation and the Holocene (e.g., Ahagon et al, 2003 ;Ohkushi et al, 2003 ;Harada et al, 2004 ;Ikehara et al, 2006 ;Shibahara et al, 2007 ;Sagawa and Ikehara, 2008), the extent of the local reservoir effect in this area remains controversial. The local reservoir effect in the modern and former oceans has been estimated using radiocarbon dates from marine materials of known age, and radiocarbon dates from contemporaneous terrestrial and marine materials (e.g., Yoneda et al, 2001 ;Nakamura et al, 2007).…”