Persistent sea surface temperature and declined sea surface salinity in the northwestern tropical Pacific over the past 7500 years |
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| Institution: | 1. Key Laboratory of Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China;2. MARUM, Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany;3. ZEKAM, Department of Geosciences, University of Bremen, Bremen, Germany;4. GAIA-Antártica, University of Magallanes, Punta Arenas, Chile;1. School of Geosciences, China University of Petroleum, Qingdao 266580, China;2. Key Laboratory of Marine Hydrocarbon Resources and Environmental Geology, Qingdao Institute of Marine Geology, Ministry of Land and Resources, Qingdao, 266071, China;3. Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, China;4. Laboratory for Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, China;5. State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China |
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| Abstract: | To understand Holocene climate evolutions in low-latitude region of the western Pacific, paired δ18O and Mg/Ca records of planktonic foraminifer Globigerinoides ruber (250–300 μm, sensu stricto, s.s.) from a marine core ORI715-21 (121.5°E, 22.7°N, water depth 760 m) underneath the Kuroshio Current (KC) off eastern Taiwan were analyzed. Over the past 7500 years, the geochemical proxy-inferred sea surface temperature (SST) hovered around 27–28 °C and seawater δ18O (δ18OW) slowly decreased 0.2–0.4‰ for two KC sites at 22.7° and 25.3°N. Comparison with a published high-SST and high-salinity equatorial tropical Pacific record, MD98-2181 located at the Mindanao Current (MC) at 6.3°N, reveals an anomalous time interval at 3.5–1.5 kyr ago (before 1950 AD). SST gradient between the MC site and two KC site decrease from 1.5–2.0 °C to only 0–1 °C, and δ18OW from 0.1–0.3‰ to 0‰ for this 2-kyr time window. The high SST and low gradient could result from a northward shift of the North Equatorial Current, which implies a weakened KC. The long-term descending δ18OW and increasing precipitation in the entire low-latitude western Pacific and the gradually decreasing East Asian summer monsoonal rainfall during middle-to-late Holocene is likely caused by different land and ocean responses to solar insolation and/or enhanced moisture transportation from the Atlantic to Pacific associated with the southward movement of ITCZ. |
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