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

被描述为气候系统试图达到完全冰川状态的早期失败的海洋同位素阶段M2，发生在329万年前，代表着上新世的第一个严寒事件。然而，紧随其后的是一段特殊和持续的温暖，由于它与模拟未来气候有关，因此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。我们的研究主要集中在冷事件管理信息系统M2的建立、稳定性、恢复和向持续升温的过渡等方面，并首次具体详细地发表了这方面的研究成果。我们的结果显示，北大西洋洋流(NAC)的突然南移使得格陵兰冰盖得以扩张。然而，NAC不稳定的原因仍然不确定，尽管它们对未来和过去气候的建模至关重要。这项拟议的研究通过分析北大西洋千年尺度的新地点，扩大了我们的空间覆盖范围。我们使用一种新的组合(甲藻包囊、地球化学、冰排碎屑)来重建海表面温度、盐度、冰融化的证据和NAC强度。 MIS16在65万年前见证了中更新世第一次重大的气候恶化，以及第一次大规模的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在MIS16终止之前很久就增加了，这意味着一种未知的放大机制。我们建议通过MIS16对甲藻孢囊进行首次千年规模的研究，以评估NAC的影响，并量化北大西洋两个战略地点的海面温度和盐度。 基于我们的新的相同样本方法建立的与地球化学古温度相关联的上新世甲藻孢囊组合的扩展数据集将唯一地允许我们确定已灭绝的上新世分类群的数值温度要求，并将现存分类群的现代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孢囊在古环境重建中的实用性。

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.