Stable isotope record of planktonic foraminifera from the Sulu Sea@en

A high-resolution, accelerator mass spectroscopy 14C dated sediment record from the Sulu Sea clearly indicates that the Younger Dryas event affected the western equatorial Pacific. Planktonic foraminiferal delta18O and abundance data both record significant changes during Younger Dryas time. In particular, a 0.4 per mil increase in the delta18O value of Globigerinoides ruber and the reappearance of the cool water planktonic foraminifera, Neogloboquadrina pachyderma, occur during the Younger Dryas at this location. These isotopic and faunal changes are a response to either surface water temperature or salinity changes, or some combination of the two. Changes in surface salinities could have been accomplished through either local or global processes. Intensification of the monsoon climate system and increased precipitation at approximately 11 ka is one mechanism that may have resulted in local changes in salinity. A meltwater pulse derived from the Tibetan Plateau is another mechanism which may have caused local changes in salinity. The presence of the Younger Dryas in the tropical western Pacific clearly indicates that this climatic event is not restricted to the North Atlantic or high latitudes, but rather is global in extent.本研究基于苏禄海（Sulu Sea）一处经加速器质谱法（accelerator mass spectroscopy）¹⁴C定年的高分辨率沉积记录，清晰证实新仙女木事件（Younger Dryas）曾影响西赤道太平洋区域。浮游有孔虫氧同位素δ¹⁸O及丰度数据均记录了新仙女木期的显著变化。具体而言，该站位在新仙女木期内，红拟抱球虫（Globigerinoides ruber）的δ¹⁸O值升高0.4‰，同时冷水型浮游有孔虫厚壁新方抱球虫（Neogloboquadrina pachyderma）重现。上述同位素与种群组合变化，可归因于表层海水温度、盐度的改变，或二者的共同作用。表层盐度变化可通过局地或全球过程实现。约11 ka时季风气候系统增强、降水增加，是引发局地盐度变化的潜在机制之一；源自青藏高原的融水脉冲，则是另一项可能导致局地盐度改变的机制。热带西太平洋存在新仙女木事件这一事实，明确表明该气候事件并非仅局限于北大西洋或高纬度区域，而是具有全球性分布特征。