North Atlantic Bottom Water Temperature and Ice Volume Records from the Mid-Pleistocene Transition

了解太阳强度、全球冰量和二氧化碳水平对全球气候系统的影响对于气候模型重建过去和未来气候的能力至关重要。特别是，研究过去的冰量变化对预测冰盖稳定性和海平面变化至关重要。在中更新世过渡期（约60万至120万年前），气候对太阳强度的反应发生了巨大变化，冰量和二氧化碳水平的变化可能促成了这一转变。该项目旨在解决海洋底层水温度和环流的变化，以评估全球冰量变化作为中更新世过渡的潜在驱动因素。更广泛的影响包括对一位女博士后科学家的支持，本科生的研究经验，以及为纽约的Lamont-Doherty地球观测核心储存库设计的教育展示。大多数对中更新世过渡的气候解释来自底栖有孔虫的氧同位素记录，记录了温度和冰量信号的组合。底栖有孔虫的Mg/Ca比值可以作为一个独立的海洋底层水温的代理，并已被用来分离海洋底层水温和冰体积组分的氧同位素记录从底栖有孔虫。目前，只有两个高分辨率记录的海洋底部水温和海水氧同位素组成（作为代理冰量）在中更新世过渡。然而，这些研究记录了根本不同的趋势，表明中更新世过渡的不同机制。该项目将利用底栖有孔虫的镁/钙和氧同位素值来评价区域和全球海底水温信号和北大西洋冰量信号。这些数据将用于评估中更新世过渡期间海底水温的任何变化、冰量增长的时间和海平面变化的幅度。这将有助于气候建模者为中更新世过渡设定边界条件，并确定影响全球气候的关键因素。

Understanding the effects of solar strength, global ice volume and carbon dioxide levels on the global climate system is essential for climate models' ability to reconstruct past and future climate. In particular, studying past ice volume variations are of vital importance to predicting ice sheet stability and sea level change. During the mid-Pleistocene transition (~600,000 to 1,200,000 years ago), the climate's response to solar strength changed dramatically and variations in ice volume and carbon dioxide levels may have contributed to this transition. This project aims to resolve changes in ocean bottom water temperature and circulation to evaluate global ice volume variability as a potential driving factor for the mid-Pleistocene transition. The broader impacts include support for a female postdoctoral scientist, undergraduate research experiences, and educational displays designed for the Lamont-Doherty Earth Observatory Core Repository in New York.Most climate interpretations for the mid-Pleistocene transition come from oxygen isotope records from benthic foraminifera, which record a combination of temperature and ice volume signals. The Mg/Ca ratio of benthic foraminifera may serve as an independent proxy of ocean bottom water temperature and has been used to separate ocean bottom water temperature and ice volume components in the oxygen isotope records from benthic foraminifera. Currently there are only two high-resolution records of ocean bottom water temperature and seawater oxygen isotope composition (as a proxy for ice volume) during the mid-Pleistocene transition. However, these studies record fundamentally different trends, suggesting different mechanisms for the mid-Pleistocene transition. This project will use coupled Mg/Ca and oxygen-isotope values of benthic foraminifera to evaluate regional and global signals in ocean bottom water temperature and ice volume signals from the North Atlantic. These data will be used to assess any changes in ocean bottom water temperature, the timing of ice volume growth and the magnitude of sea level variation during the mid-Pleistocene transition. This will aid climate modelers in setting boundary conditions for the mid-Pleistocene transition and in identifying the key factors influencing global climate.