NSFGEO-NERC Pliocene Sea Level Amplitudes (PLIOAMP)

该项目由国家科学基金会地球科学局(NSF/GEO)和英国自然环境研究理事会(NERC)通过NSF/GEO-NERC牵头机构协议共同资助。该协定允许美国和英国提交一个单一的联合提案，并由该机构进行同行审查，该机构的调查员在预算中所占比例最大。在成功地联合确定一项裁决后，每个机构将为预算和调查员与其自身工作部分相关的比例提供资金。对南极冰盖未来海平面上升的预测差异很大，仍然存在很大的不确定性。尤其令人关切的是，冰盖的海洋部分有可能崩塌并导致海平面快速上升。未来最高的海平面预测来自一项研究，该研究使用上新世(530万至260万年前)的海平面数据校准了冰盖模型，主要基于古代海岸线的海拔。然而，最近的研究表明，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好的约束估计，以确定冰盖对比今天更温暖的气候条件的敏感性，并验证在未来预测中使用的模型。该项目旨在通过从海洋沉积物中记录的替代数据重建极地冰量变化的幅度，然后使用这些数据来验证和评估模拟冰量变化的冰盖模拟方法。该项目的目标是1)改进上新世海平面估计，2)使用数据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南极冰盖的海洋部分在上新世暖期是否有重大退缩，以及是否确实需要能够导致海平面迅速上升的过程，如海冰悬崖破裂，以解释过去发生的海平面上升事件。该工作计划将1)使用海洋地球化学指标重建上新世中期多个冰川-间冰期周期的冰量变化幅度，2)模拟南极和北半球冰盖在这些相同周期内的冰量变化，3)使用参数化和解析的接地线方案比较两个模型中南极冰盖的变化，以及4)确定是否需要海洋冰崖破裂来模拟上新世的动力学。新的海平面估计将限制未来气候变化下的南极模拟，产生对未来海平面上升的世纪和更长时间尺度的预测。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.