Major Mid-Late Holocene Cooling in the East China Sea Revealed by an Alkenone Sea Surface Temperature Record

• Published in: Journal of Ocean University of China 2014-12, Vol.13 (6), p.935-940
• Main Authors: Zhao, Meixun, Ding, Ling, Xing, Lei, Qiao, Shuqing, Yang, Zuosheng
• Format: Article
• Language: English
• Subjects: Climate; Climate change; Continental shelves; Cooling; Earth and Environmental Science; Earth Sciences; El Nino; Holocene; Meteorology; Ocean circulation; Ocean currents; Ocean temperature; Oceanography; Sea surface temperature; Southern Oscillation; Surface water; Upwelling; 东中国海; 中晚全新世; 全新世中期; 夏季风强度; 海表; 温度记录; 烯酮; 降温
• ISSN: 1672-5182; 1993-5021; 1672-5174
• DOI: 10.1007/s11802-014-2641-2

Although the mid-late Holocene cold and dry event about 4000years ago （the 4ka event） has been observed almost globally, it was most prominent in terrestrial climate proxies from the lower latitudes. Here we evaluate the oceanic response to this event in terms of a Holocene sea surface temperature （SST） record reconstructed using the U~7 index for Core B3 on the continen- tal shelf of the East China Sea. The record reveals a large temperature drop of about 5~C from the mid-Holocene （24.7~C at 5.6ka） to the 4ka event （19.2~C at 3.8ka）. This mid-late Holocene cooling period in Core B3 correlated with （i） decreases in the East Asia summer monsoon intensity and （ii） the transition period with increased E1 Nifio/Southern Oscillation activities in the Equatorial Pa- cific. Our SST record provides oceanic evidence for a more global nature of the mid-late Holocene climate change, which was most likely caused by a southward migration of the Intertropical Converge Zone in response to the decreasing summer solar insolation in the Northern Hemisphere. However, the large SST drop around Core B3 indicates that the mid-late Holocene cooling was regionally amplified by the initiation/strengthening of eddy circulation/cold front which caused upwelling and resulted in additional SST de- crease. Upwelling during the mid-late Holocene also enhanced with surface productivity in the East China Sea as reflected by higher alkenone content around Core B3.