Reconstruction of Deep-Water Temperatures in the Drake Passage Over the Last Glacial Cycle: Application of Carbonate Clumped Isotope Thermometer to Absolutely-Dated Deep-Sea Corals

这项拟议的研究旨在通过将新开发的碳酸盐簇状同位素温度计应用于一组独特的现代和化石深海珊瑚，来获得过去4万年来德雷克海峡深水温度的高分辨率、精确和准确的记录，从而加深对南大洋在调节全球气候中的作用的理解。此外，这项研究将进一步评估这一新温度计从深海珊瑚骨架中准确估计过去海洋温度的潜力。资金将支持一名职业生涯早期的初级科学家和一名研究生。尽管南大洋在调节全球气候方面发挥了关键作用，但南大洋环境变化的速度和幅度往往很难加以限制。特别是，关于上一次冰川周期期间南大洋深水温度的知识极其有限。这既是因为缺乏关于南大洋深海的准确年代的气候记录，也是因为大多数现有的温度指标(例如有孔虫和珊瑚的Del18O和镁/钙)受到生物“重要影响”的影响。后者尤其有问题；它在解释这些地球化学指标方面造成了很大的挑战，并可能导致温度估计中相当于数十度的偏差。最近开发的碳酸盐块状同位素温度计为重建南大洋的深水温度带来了新的希望，因为对该温度计在深海珊瑚中的校准研究表明，它在很大程度上没有重要影响。这项拟议的研究旨在改进深海珊瑚在低温下的碳酸盐块块同位素温度计的校准，改进实验方法以获得高精度的温度估计，然后将该温度计应用于最近由极地计划办公室(OPP)资助的两次巡航中从德雷克海峡收集的独特的现代和化石深海珊瑚，这些珊瑚已经通过放射性碳法和U系列方法进行了测年。通过将重建的温度与这些深海珊瑚的放射性碳和U-Th年龄相结合，这项研究将探索这些温度变化与全球气候变化之间的关系。

This proposed research aims to produce high resolution, precise and accurate records of deep water temperatures in the Drake Passage over the past ~40,000 years, by applying the newly developed carbonate clumped isotope thermometer to a unique collection of modern and fossil deep-sea corals, and thus advance the understanding of the role of the Southern Ocean in modulating global climate. In addition, this study will provide further evaluation on the potential of this new thermometer to derive accurate estimates of past ocean temperatures from deep-sea coral skeletons. Funding will support an early-career junior scientist and a graduate student. Despite its crucial role in modulating global climate, rates and amplitudes of environmental changes in the Southern Ocean are often difficult to constrain. In particular, the knowledge about the deep water temperatures in the Southern Ocean during the last glacial cycle is extremely limited. This results both from the lack of well-dated climate archives for the deep Southern Ocean and from the fact that most existing temperature proxies (e.g. del18O and Mg/Ca of foraminifera and corals) suffer from the biological 'vital effects'. The latter is especially problematic; it causes substantial challenges in interpreting these geochemical proxies and can lead to biases equivalent to tens of degrees in temperature estimates. Recent development of carbonate clumped isotope thermometer, holds new promises for reconstructing deep water temperatures in the Southern Ocean, since calibration studies of this thermometer in deep-sea corals suggest it is largely free of vital effects. This proposed research seeks to refine the calibration of carbonate clumped isotope thermometer in deep-sea corals at low temperatures, improve the experimental methods to obtain high precision in temperature estimates, and then apply this thermometer to a unique collection of modern and fossil deep-sea corals collected from the Drake Passage during two recent Office of Polar Programs (OPP)-funded cruises, that have already been dated by radiocarbon and U-series methods. By combining the reconstructed temperatures with the radiocarbon and U-Th ages for these deep-sea corals, this study will explore the relationships between these temperature changes and global climate changes.