Stable isotope ratios of foraminifera, grain-size distribution and magnetic susceptibility record of sediment core MD99-2339

High-resolution grain size and magnetic susceptibility records from the eastern Gulf of Cadiz (site MD99-2339; 1170m water depth) reveal contourites formed by the Mediterranean Outflow (MOW) during the last 47kyr BP. Oscillations in the MOW's intensity occurred in phase with Greenland temperature variations with a stronger outflow during northern hemisphere coolings such as Dansgaard-Oeschger stadials, Heinrich events, and the Younger Dryas. Benthic delta13C data implies the Western Mediterranean Deep Water as one of the main sources feeding the outflow current, while differential changes in the properties of the Mediterranean source and entrained North Atlantic Central Water largely control the MOW's strength. Detailed studies for Heinrich events 1, 4 and 5 show that the flow strength peaked only when subtropical surface waters prevailed in the eastern Gulf of Cadiz, while incursions of icebergs and subpolar surface water were not favorable for the MOW's intensification. As the MOW was strong when the Atlantic's thermohaline circulation (THC) was weakened, the heat and salt injected by the MOW into the intermediate North Atlantic waters might have preconditioned the THC to switch from the stadial to the interstadial mode.取自加的斯湾东部站位MD99-2339（水深1170米）的高分辨率粒度与磁化率记录，揭示了过去47千年BP期间由地中海溢流（Mediterranean Outflow, MOW）形成的等深流沉积。地中海溢流强度的振荡与格陵兰温度变化呈同相位特征：在北半球冷期（如Dansgaard-Oeschger冷阶、海因里希事件以及新仙女木事件）期间，溢流强度更强。底栖δ¹³C数据表明，西地中海深层水（Western Mediterranean Deep Water）是补给该溢流的主要源水之一；而地中海源水与卷入的北大西洋中层水的性质差异变化，在很大程度上控制了地中海溢流的强度。针对海因里希事件1、4、5的详细研究显示，仅当加的斯湾东部盛行亚热带表层水时，流强才会达到峰值，而冰山入侵与亚极地表层水侵入则不利于地中海溢流的增强。由于大西洋热盐环流（thermohaline circulation, THC）减弱时地中海溢流强度较高，其注入北大西洋中层水的热量与盐分，可能预先促使热盐环流从冷阶模式转换为间冷阶模式。