How hot was the Jurassic Greenhouse climate?

对地球历史上温暖间隔的研究有助于深入了解二氧化碳和温度升高下气候系统的行为。侏罗纪就是这样的一个时期，大气中二氧化碳的浓度接近于现在的400ppm或更高的浓度。这个变暖世界的一个显著特征是存在大型陆表海道，如北美中晚侏罗世圣丹斯海（例如Danise et al. 2020）。圣丹斯海的最大范围从犹他州一直延伸到北冰洋。这些巨大的陆表海道是我们获取古代海洋气候和生物多样性信息的主要来源。然而，越来越多的证据表明，由于水体质量、深度、盐度和分层的变化以及缺氧的场所，这些航道往往与公海条件脱钩。因此，了解这些系统对于重建陆表海道在海洋环流、碳循环和气候改善方面的作用至关重要。这项研究将调查圣丹斯海的关键地点，在美国和加拿大。利用野外采集的稳定同位素和块状同位素生物碳酸盐样品，将以前所未有的空间分辨率分析重建温度和碳循环。碳酸盐团块同位素温度计是重建陆表环境温度的宝贵工具，因为它不依赖于碳酸盐沉淀水的同位素组成（Price et al. 2019; Vickers et al. 2019; Bajnai et al. 2020; Paxton et al. 2020）。分析技术将用于评价地球化学特征和生物保存（如电感耦合等离子体原子发射光谱仪（ICP-AES）和阴极发光岩石学）。

Examination of warm intervals in Earth's history help develop insight into the behavior of the climate system under elevated carbon dioxide and temperature. One such interval is the Jurassic which sees atmospheric CO2 concentrations close to current concentrations of around 400 ppm or higher. A significant feature of this warmer world was the presence of large epicontinental seaways such as the Middle-Late Jurassic Sundance Sea of North America (e.g. Danise et al. 2020). At its greatest extent the Sundance Sea stretched from Utah to the Arctic Ocean. These large epicontinental seaways are the dominant source for much of our information about ancient marine climates and biodiversity. There is, however, growing evidence that these seaways are often decoupled from open-ocean conditions because of variations in water mass, depth, salinity, and stratification and being a loci of anoxia. Hence, understanding these systems is critical to reconstruct the role epicontinental seaways play in terms of ocean circulation, carbon cycling, and climate amelioration.This research will investigate key sites within the Sundance Sea, in the USA and Canada. Using stable isotopes and clumped isotopes biogenic carbonate samples derived from fieldwork, will be analysed to reconstruct temperature and carbon cycling at unprecedented spatial resolution. The carbonate clumped isotope thermometer is a valuable tool for reconstructing temperatures in epicontinental settings due to its independence from the isotopic composition of the water from which a carbonate precipitates (Price et al. 2019; Vickers et al. 2019; Bajnai et al. 2020; Paxton et al. 2020). Analytical techniques will be used to evaluate the geochemical character and biogenic preservation (e.g., Inductively Coupled Plasma-Atomic Emission Spectrometer (ICP-AES) and the cathodoluminescence petrography.