NSFGEO-NERC Pliocene Sea Level Amplitudes (PLIOAMP)

本项目由美国国家科学基金会地球科学理事会（NSF/GEO）和英国自然环境研究委员会（NERC）通过NSF/GEO-NERC牵头机构协议共同资助。该协议允许美国/英国提交一份联合提案，并由其调查员拥有最大比例预算的机构进行同行评审。在成功地共同确定一项奖励后，每个机构为预算的比例和与它自己的工作有关的调查人员提供资金。南极冰盖对未来海平面上升的预测差异很大，而且仍然非常不确定。特别令人担忧的是，冰盖的海洋部分可能会崩塌，并导致海平面迅速上升。对未来海平面的最高预测来自一项研究，该研究利用上新世（530万至260万年前）的海平面数据校准了一个冰盖模型，该模型主要基于古代海岸线的海拔。然而，最近的工作表明，这些以前的海岸线太不确定，不能用作模型约束。需要对上新世海平面进行独立和更严格的估计，以确定冰盖对比今天更温暖的气候条件的敏感性，并验证未来预测中使用的模型。本项目旨在通过从海洋沉积物中记录的代理数据重建极地冰体积变化的幅度，然后利用这些数据验证和评估模拟冰体积变化的冰盖建模方法，从而实现这一目标。该项目的目的是：1)改进上新世海平面估计；2)使用这些数据来测试和校准预测冰盖模型；3)减少未来海平面预测的不确定性。拟议的工作计划将确定在上新世暖期期间，南极冰盖的海洋部分是否存在大规模退缩，以及能够导致海平面迅速上升的过程，如海冰悬崖断裂，是否确实需要解释过去海平面上升的事件。工作计划将：1)利用海洋地球化学指标重建上新世中期多个冰期-间冰期旋回的冰体积变化幅度；2)模拟南极和北半球冰盖在这些相同旋回中的冰体积变化；3)利用参数化和分辨率化的基准线方案比较两个模式下南极冰盖的变化；4)确定模拟上新世动力学是否需要海洋冰崖破坏。新的海平面估计将限制南极在未来气候变化下的模拟，以世纪和更长的时间尺度预测未来海平面上升。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project is jointly funded by the National Science Foundation’s Directorate of Geosciences (NSF/GEO) and the Natural Environment Research Council (NERC) of the United Kingdom (UK) via the NSF/GEO-NERC Lead Agency Agreement. This Agreement allows a single joint US/UK proposal to be submitted and peer-reviewed by the Agency whose investigator has the largest proportion of the budget. Upon successful joint determination of an award, each Agency funds the proportion of the budget and the investigators associated with its own component of the work. Projections of future sea-level rise from the Antarctic Ice Sheet vary widely and remain deeply uncertain. Of particular concern is the potential for marine-based sectors of the ice sheet to collapse and cause fast sea-level rise. The highest future sea-level projections come from a study that calibrated an ice-sheet model using sea-level data from the Pliocene epoch (5.3 to 2.6 Million years ago), based mainly on the elevation of ancient shorelines. However, recent work indicates that those former shorelines are too uncertain to be used as a model constraint. Independent and better-constrained estimates of Pliocene sea level are needed to determine ice-sheet sensitivity to climatic conditions warmer than today and to validate models used in future projections. This project aims to achieve that through reconstructing the amplitude of polar ice-volume change from proxy data recorded in marine sediments and then using these to validate and assess ice-sheet modeling approaches that simulate ice-volume change. The aims of the project are to 1) improve Pliocene sea-level estimates, 2) use the data to test and calibrate predictive ice-sheet models, and 3) to reduce uncertainty in future sea-level projections. The proposed workplan will determine if there was major retreat of the marine sectors of the Antarctic Ice Sheet during Pliocene warm intervals, and if processes capable of causing rapid sea-level rise such as marine-ice cliff failure are indeed required to explain past episodes of elevated sea level. The work plan will 1) reconstruct the amplitude of ice-volume change for multiple glacial-interglacial cycles during the mid-Pliocene using marine geochemical proxies, 2) simulate ice-volume change across these same cycles for both Antarctic and Northern Hemisphere ice sheets, 3) compare Antarctic ice sheet change in two models using parameterized and resolved grounding-line schemes, and 4) determine if marine ice-cliff failure is required to simulate the Pliocene dynamics. The new sea-level estimates will constrain Antarctic simulations under future climate change, producing projections of future sea level rise on century and longer timescales.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.