Origin of Millennial-scale Climate Signals in the Northwestern Subtropical Atlantic

千年尺度的气候变化是否与地球轨道的变化（以及太阳对地球表面影响的时间和分布）有关的问题已有数十年历史，但仍然是气候变化科学界争论的话题。这项研究由特拉华大学的一位科学家领导，研究了更新世期间短期气候变化如何随着轨道进动周期性的变化而演变，重点关注过去 90 万年。中心假设是西北副热带大西洋的千年尺度气候信号与外部驱动因素有关，特别是进动的第四谐波。如果热带日照强迫控制了千年尺度的变化，那么随着 19,000 年进动频率在大约 340,000 年前消失，第四次谐波（4,800 年）峰值的光谱功率应该会减少。作为检验这一假设的先决条件，这项工作将填补布莱克-巴哈马外脊稳定氧同位素记录的一个关键空白，完成布莱克外脊长达 140 万年的浮游有孔虫稳定同位素记录。这实现了海洋钻探计划第 172 条的主要目标。就更广泛的影响而言，该研究将提供有关自然气候变化的重要信息，研究结果将通过首席科学家的公开演讲进行传播。资金还支持硕士学位学生。

The question of whether millennial-scale climate changes are related to changes in the Earth's orbit (and thus the timing and distribution of solar influence on the Earth's surface) is decades old, but remains the subject of debate in the climate change science community. This research, led by a scientist at the University of Delaware, investigates how short-term climate variability evolved as the periodicity of orbital precession has changed through the Pleistocene, focusing on the last 900,000 years. The central hypothesis is that millennial-scale climate signals in the northwestern subtropical Atlantic are linked to external driving factors, specifically the fourth harmonic of precession. If tropical insolation forcing controls millennial-scale variability, then there should be a reduction in the spectral power of the fourth harmonic (4,800 year) peak as the 19,000 year precession frequency disappears after about 340,000 years ago. As a prerequisite for testing the hypothesis, the work will fill a key gap in the stable oxygen isotope record from the Blake-Bahama Outer Ridge, completing a 1.4 million year long planktonic foraminifer stable isotope record from the Blake Outer Ridge. This fulfills a primary objective of Ocean Drilling Program Leg 172. In terms of broader impacts, the research will provide important information about natural climate variability, and results will be disseminated through public presentations by the lead scientist. Funding also supports a Master's degree student.