Collaborative research: Sea-level responses to sediment erosion and deposition over the past 3 million years

合作研究：过去 300 万年海平面对沉积物侵蚀和沉积的响应

• 批准号: 1527351
• 负责人: Jerry Mitrovica
• 金额: $ 8.94万
• 依托单位: Harvard University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-01 至 2018-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1527351&HistoricalAwards=false
• 关键词: Collaborative; research; Sea; level; responses

A non-technical description of the project, which explains the project's significance and importanceRising sea level is a concern for coastal communities, regardless of its ultimate cause. This project will more accurately investigate the height of sea level as it was during the mid-Pliocene climatic optimum, approximately three million years ago. This time period is important because atmospheric carbon dioxide had levels of 350 to 450 parts per million and global temperatures were two to three degrees warmer than today. Accordingly, conditions during this episode are analogous to projections of the Earth's future during the next century. Current models of sea level for this time are controversial because of the lack of knowledge about the extent of polar ice that existed. This project will examine three locations where shorelines that formed during the mid-Pliocene climatic optimum are exposed and have wide differences in elevation above present sea level. The main goal is to incorporate the mass of sediment that has subsequently been eroded and redeposited from these uplifted shorelines into numerical models in order to more accurately reconstruct the actual height of sea level during this era and estimate the extent of polar ice. This will provide a tool to better predict the magnitude of future sea-level rise under warming conditions.A technical description of the projectSea-level changes provide an important constraint on ice volumes and polar ice-sheet stability during periods of relative ice-age warmth, including the mid-Pliocene Climatic Optimum (MPCO), the interglacial periods represented by Marine Isotope Stages 5e and 11 (~120 thousand years and ~400 thousand years ago, respectively), and the present. In this regard, the MPCO remains a period of significant interest and contention. Climate models of the MPCO often adopt a eustatic sea level of 25 meters higher than the present-day as a boundary condition, but individual published estimates range from 10-40 meters. Any eustatic value above 10 meters implies major collapse of ice sheets at both poles. Model-based corrections of sea-level markers for glacial isostatic adjustment and mantle flow-induced dynamic topography are available, but the most recent application of these models yields residual elevations for sea-level of MPCO age along the U.S. east coast with large and systematic geographic variability. This proposal focuses on improving existing estimates of eustatic sea level and ice volumes during the MPCO by accounting for sediment redistribution along the US east coast and the southern coastal margins of Australia and South Africa. This research is a novel study at the interface between coastal margin processes and paleoclimate.

该项目的非技术性描述，解释了该项目的意义和重要性海平面上升是沿海社区关注的一个问题，无论其最终原因如何。该项目将更准确地调查大约三百万年前上新世中期气候最佳时期的海平面高度。这个时期很重要，因为大气中二氧化碳的含量为百万分之 350 至 450，而且全球气温比今天高了两到三度。因此，这一时期的情况类似于对下个世纪地球未来的预测。由于缺乏对现存极地冰层范围的了解，当前的海平面模型存在争议。该项目将考察三个地点，这些地点的海岸线是在上新世中期气候最适宜时期形成的，这些地点的海岸线暴露在外，并且与当前海平面的海拔差异很大。主要目标是将随后被侵蚀并从这些隆起的海岸线重新沉积的沉积物纳入数值模型，以便更准确地重建该时期的实际海平面高度并估计极地冰的范围。这将为更好地预测变暖条件下未来海平面上升的幅度提供一个工具。该项目的技术描述海平面变化对冰期相对温暖时期的冰量和极地冰盖稳定性提供了重要的约束，包括上新世中期气候最佳期（MPCO）、以海洋同位素阶段 5e 和 11 为代表的间冰期（分别为约 12 万年前和约 40 万年前）和现在。在这方面，MPCO 仍然是一个引起重大兴趣和争议的时期。 MPCO的气候模型通常采用比现在高25米的海平面平衡作为边界条件，但个别发表的估计范围在10-40米之间。任何高于 10 米的海平面上升值都意味着两极冰盖都会发生严重崩塌。基于模型的海平面标记修正可用于冰川均衡调整和地幔流引起的动态地形，但这些模型的最新应用产生了美国东海岸 MPCO 年龄海平面的残余高程，具有大规模和系统性的特征。地理变化。该提案的重点是通过考虑美国东海岸以及澳大利亚和南非南部沿海边缘的沉积物重新分布，改进 MPCO 期间海平面上升和冰量的现有估计。这项研究是对沿海边缘过程与古气候之间界面的一项新颖研究。