A New View of Pliocene Glaciations

随着时间的推移，地球的气候系统经历了重大变化，这些变化作为自然实验来检验我们对地球继续变暖可能产生的联系和反馈的理解。该项目研究了上新世中期（约300万至400万年前）南北半球之间的气候变化模式，当时总体气候状况比今天更温暖。关键的是，有证据表明，南极洲的冰量与今天相似，但北半球的陆地上几乎没有永久性的冰。因此，大多数气候科学家认为，气候变化将集中在南极周围地区。该研究小组最近的研究结果表明，相反，始于北半球的变化一直向南传播，实际上决定了全球温度变化的时间和数量。本项目将利用广泛分布于海洋的海洋沉积物岩心重建中上新世气候。一个主要的重点是将轨道尺度变率的数据和概念与国际努力联系起来，通过国际PRISM（上新世研究、解释和天气制图）项目综合上新世数据和建模。资金还支持研究和指导来自地球科学领域代表性不足的博士后研究人员。这项研究的主要知识价值在于首次以足够的分辨率和地理范围收集了一系列数据，以测试北半球在这一时期的动态变化的新模型，并涵盖了从这一制度到北半球周期大规模冰川作用的后期“41 kyr世界”的过渡。研究小组将通过将古气候代用记录与非洲和亚洲季风气候信号同步，从而限制海洋沉积物岩心中记录的同位素和温度变化的阶段，这些气候信号具有独特的北半球旋差依赖性，遵循Hilgen及其同事成功使用的方法来改进新近纪的时间尺度。研究结果有望推动上新世晚期地质年代学的发展，这是该时期古气候和古生物学研究的一个基本方面。布朗大学的实验室将以大约3000年的分辨率分析限制过去海洋表面温度和全球冰量的代理数据。该提案中有待验证的假设，特别是轨道强迫与上新世气候特征的修正相关性，是PlioMIP（上新世模式比较项目）社区的核心，目前主要集中在3.205 Ma的时间片和3.3至2.8 Ma之间的瞬态模拟。

The Earth's climate system has gone through major changes over time that serve as natural experiments to test our understanding of linkages and feedbacks that may come into play if the Earth continues to warm. This project investigates patterns of climate change between the northern and southern hemispheres during the mid-Pliocene epoch (~3 to 4 million years ago) when the overall climate state was warmer than today. Critically, evidence suggests that the amount of ice on Antarctica was similar to today, but that there was little or no permanent ice on land in the northern hemisphere. Most climate scientists have therefore supposed that climate change would focus on the region around the Antarctic. Recent results by this research team suggest that instead, change initiated in the northern hemisphere propagated all the way southward, and actually determined the timing and amount of temperature change globally. This project will use marine sediment cores widely distributed in the ocean to generate reconstructions of mid-Pliocene climate. A major emphasis is to link data and concepts of orbital-scale variability into international efforts to synthesize Pliocene data and modeling through the international PRISM (Pliocene Research, Interpretation and Synoptic Mapping ) program. Funding also supports research and mentoring of a postdoctoral researcher from a demographic underrepresented in geosciences. The chief intellectual merit of this research is to assemble for the first time an array of data sampled at adequate resolution and geographic range to test a new model of northern hemispheric pacing for dynamics of the period, and to cover the transition from this regime to the later "41 kyr world" of cyclic large-scale glaciation of the northern hemisphere. The research team will constrain the phasing of isotopic and temperature changes recorded in marine sediment cores by synchronizing paleoclimate proxy records to African and Asian monsoonal climate signals with a unique northern hemisphere precessional dependence, following the approach used successfully by Hilgen and colleagues to improve the Neogene time scale. The results are expected lead to advances in the geochronology of late Pliocene time period, a fundamental aspect of paleoclimatic and paleobiological studies of the period. Proxy data that constrain past ocean surface temperatures and global ice volume will be analyzed at roughly 3,000-year resolution in laboratories at Brown University. The hypotheses to be tested in this proposal, especially a revised correlation of orbital forcing to Pliocene climatic features, are central to the PlioMIP (Pliocene Model Intercomparison Project) community, now focused on a time slice at 3.205 Ma and transient simulations between 3.3 and 2.8 Ma.