Recurring occurrence of Early Paleogene hyperthermals: a one-time climatic oddity or a characteristic feature of greenhouse climates?

在地质记录中，突然变暖事件与向海洋和大气释放大量碳有关，特别是在古近纪早期。这些所谓的高温已被证明具有许多与最近由人为碳排放引起的变暖相同的关键特征(例如，有机碳的快速输入、快速变暖)。这使它们成为研究过去变暖事件的机制和影响的主要目标，因此也是测试气候模型预测和生态系统如何应对短期但大量二氧化碳排放的唯一途径之一。最近的研究表明，古近纪早期反复发生的高温事件与碳循环的轨道强迫有关。过去的温室气候是地球气候系统的固有部分，因此也是碳循环的一部分，过去的温室气候应该受到与古近纪早期相同的过程的支配；因此，在这些时间间隔期间，反复发生的高温现象是存在的。然而，到目前为止，在更古老的地质记录中，特别是在中生代温室气候中，还没有关于这些反复发生的高温事件的报道。该项目的主要目标是测试马斯特里赫特地区高温事件的发生或不发生，以便从机理上了解温室气候。这一目标将通过两个站点(北大西洋IODP站点U1403和太平洋ODP站点1210)在马斯特里赫特选定的时间间隔(67-68.5 Ma)生成古气候代理记录来实现。将生成的替代记录基于海底有孔虫地球化学(稳定同位素和镁/钙)、XRF岩心扫描和wt%CaCO3分析。提供这一信息将使人们能够详细了解温室气候的控制机制，从而测试使用高温事件作为类比来理解未来气候变暖及其影响是否合理。此外，这些数据将允许对马斯特里赫斯(本文研究的)和古近纪早期温室气候中高温事件(如果确实存在)背后的驱动机制进行复杂的比较。

In the geologic record, abrupt warming events coupled to the release of large quantities of carbon to the ocean and atmosphere occur especially during the early Paleogene. These so-called hyperthermals have been shown to share many of the same key characteristics (e.g., rapid input of organic carbon, rapid warming) as the recent warming caused by anthropogenic carbon release. This makes them a prime target to study the mechanisms and effects of past warming events and therefore one of the only ways to test climate model predictions and how ecosystems cope with short-term but large CO2 emissions. Recent studies have demonstrated that the recurrent hyperthermal events of the early Paleogene are related to orbital forcing of the carbon cycle. Being an intrinsic part of Earth’s climate system and therefore the carbon cycle, past greenhouse climates should be governed by the same processes as the early Paleogene; arguing for the occurrence of recurrent hyperthermals during these intervals. So far, however, there are no reports about these recurrent hyperthermal events in the older geologic record and especially not from the Mesozoic greenhouse climate. The principal objective of this project is to test for the occurrence or absence of hyperthermal events in the Maastrichtian in order to obtain a mechanistic understanding of greenhouse climates. This objective will be reached through the generation of paleoclimate proxy records from two sites (North Atlantic IODP Site U1403 and Pacific ODP Site 1210) across a selected time interval of the Maastrichtian (67–68.5 Ma). Proxy records to be generated are based on benthic foraminiferal geochemistry (stable isotopes and Mg/Ca), XRF core scanning, and wt% CaCO3 analyses. Providing this information will allow detailed insight into the controlling mechanisms of greenhouse climates and therefore a test if the use of hyperthermal events as analogues to understand future climate warming and its implications is reasonable or not. Moreover, the data will allow a sophisticated comparison of the driving mechanisms behind hyperthermal events (if they indeed exist) during the greenhouse climates of the Maastrichtian (studied herein) and the early Paleogene.