High-Resolution Pleistocene Alkenone Temperature Records of IODP Expedition 346 Sites U1425 and U1429

Abstract:

Site U1425 drilled by IODP Expedition 346 is located at the top of the Yamato Ridge, the central part of the sea. This study reconstructs variations in SST for the last 2 million years by using the alkenone unsaturation index of marine sediments recovered from Site U1425. There have been many studies on the palaeoceanography of the northwestern Pacific marginal seas covering the last glacial maximum and/or the penultimate glacial maximum periods. Until recently, however, little information was available on longer time scale proxy records of the northwestern Pacific margin. Establishing palaeoceanographic records from the northwestern Pacific margin is necessary for understanding the large scale ocean and climate changes and/or their linkages. This study presents a long term alkenone temperature record of Site U1425 spanning the last two million years. The reconstructed alkenone temperatures clearly illustrate the variability being consistent with orbital-scale global climate records over the period. Especially the alkenone SSTs fluctuate greatly and they are comparable to world-wide benthic foraminiferal isotope stack record. We will present more details regarding the characteristics of 2 million year SSTs in the presentation. Site U1429 was drilled by IODP Expedition 346 in the northern part of the Okinawa Trough in the East China Sea. Here we will also present extremely high-resolution alkenone temperature changes of Site U1429 over the last 400,000 years. Comparison of these records with other proxy records from high- to low-latitudes will give us a unique chance to understand the linkage between latitudinal climate patterns and dynamics.