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.

对项目的非技术描述，解释项目的意义和重要性海平面上升是沿海社区关注的问题，无论其最终原因是什么。这个项目将更准确地调查海平面高度，因为它是在上新世中期气候最佳时期，大约300万年前。这一时期很重要，因为当时大气中的二氧化碳含量为百万分之350到450，全球气温比今天高出2到3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。由于对当时存在的极地冰的范围缺乏了解，目前的海平面模型是有争议的。该项目将考察上新世中期气候最佳时期形成的海岸线暴露的三个地点，这些海岸线与目前的海平面有很大的海拔差异。主要目标是将随后从这些隆起的海岸线上被侵蚀和再沉积的大量沉积物纳入数值模型，以便更准确地重建这一时期的实际海平面高度，并估计极地冰的范围。这将为更好地预测在变暖条件下未来海平面上升的幅度提供一个工具。海平面变化对相对冰期变暖时期的冰量和极地冰盖稳定性提供了重要约束，包括上新世中期气候最佳期（MPCO）、以海洋同位素阶段5e和11（分别为~12万年和~40万年前）和现在为代表的间冰期。在这方面，MPCO仍然是一个重要的兴趣和争论的时期。MPCO的气候模式通常采用比现在高25米的海平面上升作为边界条件，但个别公布的估计范围在10-40米之间。任何高于10米的波动值都意味着两极冰盖的严重崩塌。冰川均衡调整和地幔流诱发的动力地形的海平面标记物的基于模式的校正是可用的，但这些模式的最新应用产生了美国东海岸MPCO时代海平面的剩余高度，具有大而系统的地理变异。该提案的重点是通过考虑沿美国东海岸和澳大利亚和南非南部沿海边缘的沉积物再分配，改进现有的MPCO期间海平面上升和冰量的估计。本研究是在海岸边缘过程与古气候界面上的一项新研究。