Millennial-Scale Planktic Foraminifer Faunal Variability in the East China Sea during the Past 40000 Years (IMAGES MD012404 from the Okinawa Trough)

Abstract

High resolution planktic foraminifer fauna assemblage data are used to reconstruct the millennial-scale sea surface temperature (SST) variability of the past 40000 years at an IMAGES core site (MD012404) in the Okinawa Trough in the East China Sea (ECS). The fauna assemblages in core MD012404 are dominated by five species -Globigerinoides ruber, Globigerina bulloides, Neogloboquadrina dutertrei, Pulleniatina obliquiloculata, and Globigerinita glutinata, which account for > 70% in relative abundance. Our Q-mode factor analysis decomposed the fauna abundance data into three factors, which indicate cold water mass, warm water mass, and possibly coastal water flow with low salinity in the ECS. The MD012404 fauna data show abrupt changes at~16 kya, suggesting a return to a warmer climate or warm water intrusion of the Kuroshio into the Okinawa Trough since the Last Glacial Maximum (LGM). SST estimates based on the fauna assemblages of planktic foraminifers indicate a LGM cooling of 1 -2°C. A maximum cooling by 3 -4°C is observed in episodic, millennial-scale events in the glacial stages of the record. The SST record displays variability that closely tracks the structure of oxygen isotopes of stalagmites from Hulu Cave and ice cores from GISP 2 Dansgaard/Oeschger cycles and Heinrich events. Low salinity in the ECS is inferred based on MD012404 fauna SST and planktic foraminifer oxygen isotope records for the cold millennial-scale intervals, pointing to the Intertropical Convergence Zone (ITCZ) and/or East Asian monsoon as important factors driving SST and salinity in the subtropical western Pacific, both on orbital and suborbital time scales.

The last 100 000 years' palaeoenvironmental changes inferred from the diatom assemblages of core MD012404 from the Okinawa Trough, East China Sea

“…The increased inflows of less-saline water and exports of coastal water altered the relative abundances of diatom assemblages (McQuoid and Nordberg, 2003;Jiang et al, 2006). Large-scale ocean surface cooling has been reported in the ECS during the Last Glacial Maximum (LGM) and the Younger Dryas (YD) based on unsaturated alkenone concentrations, planktic foraminifer fauna transfer functions and Mg/Ca ratios of planktic foraminifers (Li et al, 2001;Sun et al, 2005;Zhou et al, 2007;Chang et al, 2008). Previous studies have also described similar cooling magnitudes within surface water during Heinrich events (HEs), which have been well reported for the high-latitude North Atlantic, as well as globally (Bond et al, 1992;Hemming, 2004).…”

“…The Pulleniatina Minimum Event (PME), which has been widely reported for the western Pacific, spanned from approximately 5 to 3 ka and was characterised by the very low abundance of the tropical-dwelling planktonic foraminifer Pulleniatina obliquiloculata (Li et al, 1997;Ujiié and Ujiié, 1999;Jian et al, 2000;Lin et al, 2006;Chang et al, 2008). This event has usually been attributed to the reduced inflow or the absence of the Kuroshio in the OT because of the enhanced winter monsoon (Jian et al, 2000).…”

Multiproxy reconstruction for Kuroshio responses to northern hemispheric oceanic climate and the Asian Monsoon since Marine Isotope Stage 5.1 (∼88 ka)

“…Previous studies on past climate changes using sediment cores from the OT show orbital-scale (Ijiri et al, 2005;Kao et al, 2006a;Kawahata et al, 2006;Zhou et al, 2007), millennial and abrupt climatic responses, such as the 8.2 ka event, the Younger Dryas, Heinrich (H) events and the DansgaardOeschger cycles of the Kuroshio (Chang et al, 2008(Chang et al, , 2009Ijiri et al, 2005;Liu et al, 2001;Yu et al, 2009). However, most of these studies were limited by either shorter cores or single-proxy reconstruction (Jian et al, 1998;Kao et al, 2006b;Lee et al, 2013;Ujiié and Ujiié, 1999) that covered only a small spatial scale of the OT which the Kuroshio has entered.…”

Introduction to the Special Section “Proxy Records and Mechanistic Studies of the Late Quaternary Paleoceanography of the Western Pacific Marginal Seas Using IMAGES Cores”

“…The second is that the millennial-scale SST variations during the last glacial were wellcorrelated with the oxygen isotope oscillations in stalagmites from Hulu Cave and in the GISP 2 ice cores. Chang et al (2008) hypothesized that these low SSTs and possibly low salinity (higher precipitation) events were coincident with strong East Asian winter monsoons, and were caused by millennial scale migrations of ITCZ in the past 40 kyr. While this is an interesting proposal, it remains to be tested with more records, as Holocene climate records from the terrestrial records of lower-latitude Asia indicate that the southward migration of the ITCZ resulted in colder but mostly drier climate (Staubwasser and Weiss 2006;Yancheva et al 2007).…”

“…Chang et al (2008) report high resolution planktic foraminifer fauna assemblage records of the last 40 kyr for core MD012404 from the Okinawa Trough. Two features are particularly noticeable from these records.…”