Plio-pleistocene dinoflagellate cysts and paleoceanography of the North Atlantic region

329万年前发生的海洋同位素阶段（MIS）M2被描述为气候系统达到完全冰川状态的早期失败尝试，代表了上新世的第一次严寒时期。 然而紧随其后的是一段异常且持续的温暖时期，由于其与未来气候建模的相关性而引起了人们的强烈兴趣。 相比之下，MIS M2 在很大程度上被忽视了。 我们的研究重点是寒冷事件 MIS M2、其开始、稳定性、恢复以及向持续温暖的过渡，并且我们是第一个专门详细发表该事件的人。 我们的结果显示北大西洋洋流（NAC）突然向南移动，导致格陵兰冰盖扩张。 然而，NAC 不稳定的原因仍然不确定，尽管它们对于未来和过去气候的建模至关重要。 拟议的研究通过以千年尺度的分辨率分析北大西洋的新地点，扩大了我们的空间覆盖范围。 我们使用一种新颖的代理组合（甲藻包囊、地球化学、冰筏碎片）来重建海面温度、盐度、冰融化的证据和 NAC 强度。 65 万年前的 MIS 16 见证了中更新世的第一次重大气候恶化，以及第一次大规模冰山释放到北大西洋。 矛盾的是，全球大气二氧化碳水平和基于地球化学的古温度早在 MIS 16 终止之前就增加了，这意味着未知的放大机制。 我们建议通过 MIS 16 对甲藻包囊进行第一个千年规模的研究，以评估 NAC 的影响并量化北大西洋两个战略位置的海面温度和盐度。 基于我们新颖的同样本方法，与地球化学古温度相关的上新世甲藻包囊组合的扩展数据集将独特地使我们能够确定灭绝的上新世类群的数值温度要求，并将现有类群的当前温度分布与上新世温度分布进行比较，从而提高上新世甲藻包囊在古环境重建中的效用。

Described as an early failed attempt by the climate system to reach a full glacial state, marine isotope stage (MIS) M2 occurring 3.29 million years ago represents the first severely cold episode of the Pliocene. Yet it was followed immediately by an interval of exceptional and sustained warmth that has attracted intense interest owing to its relevance for modeling future climate. MIS M2 in contrast has been largely overlooked. Our research focuses on the cold event MIS M2, its inception, (in)stability, recovery, and transition to sustained warmth, and we are the first to have published specifically and in detail on it. Our results show an abrupt southward shift of the North Atlantic Current (NAC) that allowed the Greenland ice sheet to expand. Yet the causes of NAC instability remain uncertain, although they are critical to the modeling of future as well as past climates. The proposed research expands our spatial coverage by analyzing new sites in the North Atlantic at millennial-scale resolution. We use a novel combination of proxies (dinoflagellate cysts, geochemistry, ice-rafted debris) to reconstruct sea-surface temperature, salinity, evidence of ice melting, and NAC strength. MIS 16 at 0.65 million years ago saw the first major climatic deterioration of the Middle Pleistocene and first massive release of icebergs into the North Atlantic. Paradoxically, global atmospheric CO2 levels and geochemically-based paleotemperatures increased well before the termination of MIS 16, implying an unknown amplification mechanism. We propose the first millennial-scale study of dinoflagellate cysts through MIS 16 to assess NAC influence and quantify sea-surface temperatures and salinities from two strategically located sites in the North Atlantic. An expanding data set of Pliocene dinoflagellate cyst assemblages linked to geochemical paleotemperatures based on our novel same-sample method will uniquely allow us to determine numerical temperature requirements of extinct Pliocene taxa and to compare present-day with Pliocene temperature distributions of extant taxa, improving the utility of Pliocene dinoflagellate cysts for paleoenvironmental reconstructions.