Sea surface temperature record off central Japan since the Last Glacial Maximum using planktonic foraminiferal Mg/Ca thermometry

Abstract

Sagawa, T., Toyoda, K. and Oba, T. 2005. Sea surface temperature record off central Japan since the Last Glacial Maximum using planktonic foraminiferal Mg/Ca thermometry.ABSTRACT: We conducted paired measurements of the Mg/Ca ratio and 18 O of planktonic foraminifera, Globigerina bulloides, from a sediment core (MD01-2420) off central Japan in the northwest Pacific, to reconstruct current movements since the Last Glacial Maximum (LGM). These methods make it possible to determine the magnitude and timing of the sea surface temperature (SST) changes and to reconstruct the variations of the past seawater 18 O ( 18 Ow) off central Japan. The amplitude of Mg/Ca-based SST changes between the Holocene and the LGM was about 10 C. The strong resemblance of the SSTs estimated from both methods, Mg/Ca-based and 18 O-based, suggests that the SST changes were caused primarily by latitudinal displacement of the KuroshioOyashio currents and no distinct change in the carbonate dissolution of the core. The southward migration of the water mass was 5-6 in latitude at the LGM. The values for regional 18 Ow changes, which were obtained by subtracting the ice volume contribution from the calculated 18 Ow, describe the millennial-scale water mass migration over the last 30 kyr.

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

“…1 Sagawa et al (2006) confirmed the high quality of the core by comparing the sediment colour and planktic foraminiferal δ 18 O between this core and MD01-2421, another IMAGES piston core adjacent to the MD01-2420 site with well-established age control (Oba and Murayama, 2004;Oba et al, 2006). …”

“…After confirming that all dirt had been removed, we washed the shells in Milli-Q water and dried them in an oven at 40 • C. 14 C ages were measured by accelerator mass spectrometry (AMS) at the National Ocean Sciences AMS facility (NOSAMS) at Woods Hole Oceanographic Institution (Table 2). Three 14 C ages of G. inflata were measured at the Center for Chronological Research, Nagoya University, Japan (Table 2; Sagawa et al, 2006).…”

Quantitative reconstruction of palaeoclimate from pollen profiles in northeastern Japan and the timing of a cold reversal event during the Last Termination

“…13.9-12.4 cal. ka was reported at Kashima, which is the boundary of the Kuroshio Warm Current and the Oyashio Cold Current off central Japan (Sagawa et al, 2006). These data may indicate that the Kuroshio Warm Current retreated southward, and heat transportation from the tropical zone was weak in this period.…”

Response of mid‐latitude North Pacific surface temperatures to orbital forcing and linkage to the East Asian summer monsoon and tropical ocean–atmosphere interactions

“…The high sedimentation rate of Core MD01-2421 (average 33 cm ka À1 ) allowed us to achieve a much higher resolution analysis than has been attained previously. The Kashima Core Research Group investigated this core for foraminiferal oxygen isotopes (Oba and Murayama, 2004;Oba et al, 2006), planktonic foraminiferal assemblages (Niimura et al, 2006), the Mg/Ca ratio (Sagawa et al, 2006), diatom assemblages (Koizumi et al, 2004), nannofossil assemblages (Aizawa et al, 2004), U K 0 37 (Yamamoto et al, 2004(Yamamoto et al, , 2005bIsono et al, unpublished data), organic carbon content and isotopes (Ueshima et al, 2006), pollen and spores (Igarashi and Oba, 2006) and lignin (Yamamoto et al, 2005a).…”