Sea surface temperature estimation for MIS 16 of IODP Site 306-U1313@en

Hudson Strait (HS) Heinrich Events, ice-rafting events in the North Atlantic originating from the Laurentide ice sheet (LIS), are among the most dramatic examples of millennial-scale climate variability and have a large influence on global climate. However, it is debated as to whether the occurrence of HS Heinrich Events in the (eastern) North Atlantic in the geological record depends on greater ice discharge, or simply from the longer survival of icebergs in cold waters. Using sediments from Integrated Ocean Drilling Program (IODP) Site U1313 in the North Atlantic spanning the period between 960 and 320 ka, we show that sea surface temperatures (SSTs) did not control the first occurrence of HS Heinrich(-like) Events in the sedimentary record. Using mineralogy and organic geochemistry to determine the characteristics of ice-rafting debris (IRD), we detect the first HS Heinrich(-like) Event in our record around 643 ka (Marine Isotope Stage (MIS) 16), which is similar as previously reported for Site U1308. However, the accompanying high-resolution alkenone-based SST record demonstrates that the first HS Heinrich(-like) Event did not coincide with low SSTs. Thus, the HS Heinrich(-like) Events do indicate enhanced ice discharge from the LIS at the end of the Mid-Pleistocene Transition, not simply the survivability of icebergs due to cold conditions in the North Atlantic.哈德逊海峡（HS）海因里希事件是源自劳伦泰德冰盖（LIS）的北大西洋冰筏事件，亦是千年级气候变率最显著的例证之一，对全球气候具有显著影响。然而，地质记录中（东）北大西洋地区HS海因里希事件的发生究竟是源于冰排放增强，还是仅因冰山在冷水环境中存留更久，学界尚未达成共识。本研究利用北大西洋综合大洋钻探计划（IODP）U1313站位96万至32万年间的沉积物样品，证实海水表面温度（SSTs）并非控制沉积记录中HS海因里希（类）事件首次出现的因素。本研究通过矿物学与有机地球化学方法分析冰筏碎屑（IRD）特征，在研究记录中于约64.3万年前（海洋同位素阶段（MIS）16）识别出首例HS海因里希（类）事件，该结果与此前U1308站位的报道一致。但配套的高分辨率基于烯酮的SST记录显示，首例HS海因里希（类）事件并未伴随海水表面温度降低。因此，HS海因里希（类）事件确实反映了中更新世过渡期末期劳伦泰德冰盖的冰排放增强，而非仅因北大西洋冷水环境使得冰山存留时间延长。