A New View of Pliocene Glaciations

随着时间的推移，地球气候系统经历了重大变化，这些变化是检验我们对联系和反馈的理解的自然实验，如果地球继续变暖，这些联系和反馈可能会发挥作用。该项目调查了上新世中期(约300万至400万年前)南北半球之间的气候变化模式，当时整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，北半球引发的变化一直向南传播，实际上决定了全球气温变化的时间和数量。该项目将使用广泛分布在海洋中的海洋沉积物岩心来重建上新世中期的气候。一个主要的重点是将轨道尺度变异性的数据和概念与通过国际上新世研究、解释和天气测绘(PRISM)计划合成上新世数据和建模的国际努力联系起来。资金还支持对来自地球科学中代表性不足的人口的博士后研究员的研究和指导。这项研究的主要学术价值是首次收集了一系列以足够分辨率和地理范围采样的数据，以测试北半球起搏的新模型，以了解该时期的动力学，并涵盖从这一体制向后来的北半球周期性大规模冰川作用“41KYR世界”的过渡。该研究小组将通过将古气候替代记录与具有独特北半球进动相关性的非洲和亚洲季风气候信号同步，限制记录在海洋沉积物岩心中的同位素和温度变化的阶段性，遵循希尔根和他的同事成功地使用的方法来改进新近纪的时间尺度。这些结果有望导致上新世晚期地质年代学的进步，这是该时期古气候和古生物研究的一个基本方面。布朗大学的实验室将在大约3000年的分辨率下分析限制过去海洋表面温度和全球冰量的代理数据。这项提议中将要检验的假设，特别是修正后的轨道强迫与上新世气候特征的相关性，是上新世模型对比项目(PlioMIP)的核心，目前集中在3.205 Ma的时间切片和3.3Ma2.8Ma之间的瞬变模拟。

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.