Grain-size, lithic grains, foraminifera-derived and dinocyst-derived data of sediment core MD99-2281@en

The last glacial period was punctuated by abrupt climatic events with extrema known as Heinrich and Dansgaard-Oeschger events. These millennial events have been the subject of many paleoreconstructions and model experiments in the past decades, but yet the hydrological processes involved remain elusive. In the present work, high-resolution analyses were conducted on the 12-42 ka BP section of core MD99-2281 retrieved southwest of the Faeroe Islands, and combined with analyses conducted in two previous studies (Zumaque et al., 2012; Caulle et al., 2013). Such a multiproxy approach, coupling micropaleontological, geochemical and sedimentological analyses, allows us to track surface, subsurface, and deep hydrological processes occurring during these rapid climatic changes. Records indicate that the coldest episodes of the studied period (Greenland stadials and Heinrich stadials) were characterized by a strong stratification of surface waters. This surface stratification seems to have played a key role in the dynamics of subsurface and deep-water masses. Indeed, periods of high surface stratification are marked by a coupling of subsurface and deep circulations which sharply weaken at the beginning of stadials, while surface conditions progressively deteriorate throughout these cold episodes; conversely, periods of decreasing surface stratification (Greenland interstadials) are characterized by a coupling of surface and deep hydrological processes, with progressively milder surface conditions and gradual intensification of the deep circulation, while the vigor of the subsurface northward Atlantic flow remains constantly high. Our results also reveal different and atypical hydrological signatures during Heinrich stadials (HSs): while HS1 and HS4 exhibit a \"usual\" scheme with reduced overturning circulation, a relatively active North Atlantic circulation seems to have prevailed during HS2, and HS3 seems to have experienced a re-intensification of this circulation during the middle of the event. Our findings thus bring valuable information to better understand hydrological processes occurring in a key area during the abrupt climatic shifts of the last glacial period.末次冰期（last glacial period）期间被一系列极端气候突变事件所打断，其中典型代表为海因里希事件（Heinrich Event）与丹斯果-奥什格尔事件（Dansgaard-Oeschger Event）。近数十年来，这类千年尺度气候事件一直是古气候重建与数值模式试验的研究热点，但其涉及的水文过程机制仍未得到清晰阐释。本研究对法罗群岛（Faeroe Islands）西南海域采集的MD99-2281岩芯12~42 ka BP层段开展了高分辨率分析，并整合了此前两项研究（Zumaque等，2012；Caulle等，2013）的分析数据。该多代用指标方法耦合微古生物学、地球化学与沉积学分析手段，能够追踪这些快速气候突变事件期间发生的表层、次表层及深层水文过程。相关记录显示，研究时段内的最冷时段（格林兰冰阶（Greenland Stadial）与海因里希冰阶（Heinrich Stadial））以表层水体强烈层结为典型特征。这种表层水体层结似乎对次表层与深层水团的动力学过程起到关键调控作用。具体而言，表层层结较强的时期，次表层与深层环流呈现耦合状态；而在冰阶初期，该耦合作用会急剧减弱，同时表层环境在整个冷期内逐渐恶化。反之，表层层结减弱的时期（格林兰间冰阶（Greenland Interstadial））则表现为表层与深层水文过程的耦合，伴随表层环境逐步回暖、深层环流逐渐增强，而次表层北大西洋北向流的活跃度始终维持在较高水平。本研究结果还揭示了海因里希冰阶（Heinrich Stadials, HSs）期间存在差异化且非典型的水文特征：HS1与HS4呈现出翻转环流减弱的“常规”模式，而HS2期间似乎以相对活跃的北大西洋环流为主导，HS3则在事件中期出现了该环流的重新增强。因此，本研究的发现为深入理解末次冰期气候突变事件期间关键海域的水文过程提供了宝贵的科学依据。