Collaborative Research: P2C2: Re-assessing Pliocene and Miocene warm climates and identifying the 'missing physics' to explain them

合作研究：P2C2：重新评估上新世和中新世温暖气候并确定“缺失的物理学”来解释它们

• 批准号: 1602905
• 负责人: Matthew Huber
• 金额: $ 24.37万
• 依托单位: Purdue University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-15 至 2020-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1602905&HistoricalAwards=false
• 关键词: Collaborative; Research; P2C2; Re; assessing

Many of the long-term trends and transitions in climate over the past 65 million years are correlated with major changes in atmospheric carbon dioxide concentrations. But not all. Periods lasting hundreds of thousands or millions of years, for example during the Miocene and Pliocene, are loosely correlated with CO2 changes that are too small-- at least according to climate models-- to generate the large climate changes evidenced in proxy records. The purpose of this study is to investigate Miocene and Pliocene climate, with an emphasis on understanding the mechanisms responsible for widespread warmth, reduced temperature gradients, and apparently high climate sensitivity. Climate models have been unable previously to reproduce these features, raising concerns regarding their ability to correctly predict future warming. This study is novel and significant because a multi-disciplinary team combining expertise in paleoclimate data, models, and theory will generate geographically widespread, multiproxy past climate records. This data will be compared with new and advanced modeling approaches. A benefit of this approach is that climate models will be improved by this comparison with past data and the lessons learned will lead eventually to improved predictions of future climate change. Specifically, although significant progress has been achieved in understanding of Miocene and Pliocene climates, explanations are lacking for some their basic elements, such as: weakened meridional temperature gradients, weakened zonal temperature gradients across the Pacific, and preferential warming in polar regions, in upwelling regions, and in continental interiors. This study's goals are to better quantify these enigmatic features by developing new geochemical records and compare this data with state-of-the art climate modeling that will enable better prediction of the Earth system to greenhouse gas and non-greenhouse gas forcing. To accomplish this, the project will: (1) Enhance understanding of the signal being recorded by various paleoclimate proxies for sea surface temperature (SST) and generate a suite of new TEX86 and Uk37 paleo-SST records, complemented by existing records, to provide a comprehensive view of evolving surface ocean conditions from the mid Miocene through the Pliocene. (2) Conduct simulations of mid-Miocene and mid-Pliocene climate using the Community Earth System Model (CESM), with a new atmospheric component, CAM5, that includes more sophisticated treatment of cloud-aerosol interactions than previous models. Sensitivity studies to cloud microphysical properties and parameterization, including mixed-phase cloud properties and aerosol (sulfate and dust) emissions will be conducted to constrain previously unexplored interactions between cloud microphysics, aerosols and past climates. (3) Simulate Miocene and Pliocene climates using the "Super-parameterized" (SP) version of the CESM. SP-CESM incorporates a cloud-resolving model in each grid cell to represent convection and clouds more explicitly rather than parameterize them, allowing a more accurate representation of convection and cloud effects on the large-scale atmospheric circulation. In addition to the research objectives, the project has education and engagement components. It will fund two graduate students and a female early career research scientist in STEM disciplines. Three public engagement efforts will be conducted, including public lectures, a website for a broad audience, and an afterschool program for high school students.

在过去的6500万年里，气候的许多长期趋势和转变都与大气中二氧化碳浓度的重大变化有关。但不是全部。 持续数十万年或数百万年的时期，例如中新世和上新世，与CO2变化的关系很松散，这些变化太小----至少根据气候模型----不足以产生代用记录中所证明的大的气候变化。 本研究的目的是调查中新世和上新世的气候，重点是了解负责广泛的温暖，温度梯度降低和明显的高气候敏感性的机制。 气候模型以前无法重现这些特征，这引起了人们对它们正确预测未来变暖能力的担忧。 这项研究是新颖和重要的，因为一个多学科的团队结合了古气候数据，模型和理论的专业知识，将产生地理上广泛的，多代理过去的气候记录。 这些数据将与新的和先进的建模方法进行比较。 这种方法的一个好处是，气候模型将通过与过去数据的比较得到改进，所吸取的教训最终将导致对未来气候变化的预测得到改进。 具体而言，虽然在了解中新世和上新世气候方面取得了重大进展，但缺乏对其一些基本要素的解释，例如：减弱的纬向温度梯度，减弱的太平洋纬向温度梯度，以及极地地区，上升流地区和大陆内部的优先变暖。这项研究的目标是通过开发新的地球化学记录来更好地量化这些神秘的特征，并将这些数据与最先进的气候建模进行比较，从而更好地预测地球系统对温室气体和非温室气体的影响。 为了实现这一目标，该项目将：（1）加强对海洋表面温度的各种古气候代用指标记录的信号的了解，并生成一套新的TEX 86和UK 37古海洋表面温度记录，以现有记录为补充，以全面了解从中新世中期到上新世不断变化的海洋表面状况。(2)使用社区地球系统模型（CESM）进行中新世中期和上新世中期气候模拟，其中包括一个新的大气组件CAM 5，其中包括比以前的模型更复杂的云-气溶胶相互作用处理。将对云的微物理特性和参数化进行敏感性研究，包括混合相云特性和气溶胶（硫酸盐和尘埃）排放，以限制以前未探索的云微物理、气溶胶和过去气候之间的相互作用。(3)使用CESM的“超级参数化”（SP）版本模拟中新世和上新世气候。SP-CESM在每个网格单元中采用了云解析模型，以更明确地表示对流和云，而不是将其参数化，从而更准确地表示对流和云对大尺度大气环流的影响。 除了研究目标外，该项目还包括教育和参与部分。 它将资助两名研究生和一名STEM学科的女性早期职业研究科学家。 将进行三项公众参与工作，包括公开讲座，面向广大受众的网站，以及高中生的课后计划。