Ventilation changes in the western North Pacific since the last glacial period

Abstract

Abstract.We reconstructed the ventilation record of deep water at 2100 m depth in the mid-latitude western North Pacific over the past 25 kyr from radiocarbon measurements of coexisting planktic and benthic foraminiferal shells in sediment with a high sedimentation rate. The 14 C data on fragile and robust planktic foraminiferal shells were concordant with each other, ensuring high quality of the reconstructed ventilation record. The radiocarbon activity changes were consistent with the atmospheric record, suggesting that no massive mixing of old carbon from the abyssal reservoir occurred throughout the glacial to deglacial periods.

Coccolithophore carbonate during the last 450 ka in the NW Pacific Ocean (ODP site 1209B, Shatsky Rise)

“…A similar mechanism has been invoked by Okazaki et al . () for the last glacial in the mid‐latitude western North Pacific.…”

Deep water exchanges between the South China Sea and the Pacific since the last glacial period

“…Comparison of B‐P ages between the SCS and the western Pacific region during the deglacial interval. (a) Compilation of intermediate (green marks) [ Ahagon et al ., ; Duplessy et al ., ; Sagawa and Ikehara , ] and deep (purple symbols) [ Broecker et al ., , ; Minoshima et al ., ; Sarnthein et al ., ; Okazaki et al ., ] ventilation variations from available radiocarbon documents in the western Pacific. The calendar ages are converted from radiocarbon ages with Calib 7.0 using contant resorvoir age of Δ R = 500 ± 300 years, 100 ± 200, and 160 ± 150 yr in the subartic and mid‐latitude and low‐latitude western Pacific, respectively [ Okazaki et al ., ].…”

“…So far, there is no evidence for extremely 14 C‐depleted water mass in the SCS as the “dead end” of deep circulation in the Pacific, although its deep water ventilation decreased during the LGM. The deep water Δ 14 C in the SCS was approximately 90‰ during the LGM, similar to those in the western Pacific [ Broecker et al ., ; Okazaki et al ., ]. The compiled Δ 14 C records of immediate and deep waters in the western North Pacific indicate that this region was not a significant 14 C‐depleted reservoir during glacial times (Figure ).…”

“…There are still only scattered records of Δ 14 C anomalies based on the immediate water from the low‐latitude eastern Pacific, northern Arabian Sea, and South Iceland Rise [ Marchitto et al ., ; Stott et al ., ; Bryan et al ., ; Sarnthein et al ., ], and deep water from the high‐latitude northeast Atlantic Ocean [ Thornalley et al ., ] during the Mystery Interval. Our results have provided further evidence that there was no sign for remarkable intrusions of anomalously 14 C‐depleted water masses into the deep western North Pacific and the SCS during the Mystery Interval (Figure ), consistent with the previous observations based on other equatorial and middle‐high‐latitude sites in the western Pacific [ Sarnthein et al ., 2011; Okazaki et al ., , ; Broecker et al ., ]. Instead, in the western North Pacific, the deep water formation and southward extension may have played an even more significant role in the local middepth Δ 14 C values [ Okazaki et al ., , ], compared with the influence of southern sourced aged Pacific deep water from the Southern Ocean.…”

Pulses of enhanced North Pacific Intermediate Water ventilation from the Okhotsk Sea and Bering Sea during the last deglaciation

“…On the other hand, there is no significant change in ventilation seen from the shallowest records in the Bering Sea (SO201-2-101; 600 m water depth) or Okhotsk Sea (SO178-13-6; 713 m water depth) during the onset of the Bølling/Allerød. In contrast to the intermediate-water layer, deep-water ventilation ages are generally high (Murayama et al, 1992;Keigwin, 2002;Sarnthein et al, 2006;Minoshima et al, 2007;Okazaki et al, 2012) and indicate persistent, old water masses in the deep relative to the intermediate water during the last deglaciation. The largest ventilation age difference between the intermediate-and deep-water masses occurs during HS-1 and matches the results from δ 13 C measurements, which also indicate the largest vertical gradient in δ 13 C between the intermediate-and deep-water masses of the northwest Pacific during HS-1 (Fig.…”