NSFGEO-NERC Pliocene sea level amplitudes (PLIOAMP)

NSFGEO-NERC 上新世海平面振幅 (PLIOAMP)

基本信息

批准号：
NE/T007397/2
负责人：
Edward Gasson
金额：
$ 53.02万
依托单位：
UNIVERSITY OF EXETER
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2021
资助国家：
英国
起止时间：
2021 至无数据
项目状态：
未结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FT007397%2F2
关键词：
NSFGEO NERC Pliocene sea level

项目摘要

It is estimated that 5% of the world's population lives on land which is less than 5 metres above current sea level, in communities that are vulnerable to the impacts of sea level rise, either from direct loss of land, or increased flood risk. Society more broadly may be impacted by disruption to key infrastructure which is located on the coast e.g. power stations, and by the movement of displaced communities. The Antarctic ice sheet is the largest potential contributor to future sea level rise and projections of Antarctic ice sheet change in the future also have the largest range of estimates. This makes it difficult to accurately determine the risks of future sea level rise. Because sea level rise from Antarctic ice loss is not evenly distributed across the oceans, retreat of the Antarctic Ice Sheet will disproportionately affect coastlines that are furthest away, such as those in Europe and North America. In this proposal we will improve projections of Antarctic ice sheet change by reconstructing how the ice sheet changed during past warm intervals during the mid-Pliocene (approximately 3 million years ago). The mid-Pliocene is the last geological interval when atmospheric CO2 was similar to present day. The proposal will focus on reconstructing the amplitudes of mid-Pliocene sea level change between colder glacial stages and warmer interglacial states. We will use these data as a constraint for two types of ice sheet models. Recent work has used Pliocene interglacial sea level maxima as a constraint for Antarctic ice sheet models and has led to much higher projections of future sea level rise from Antarctica under anthropogenic warming. However, subsequent work has suggested that it may not be possible to accurately determine absolute Pliocene sea level maxima, such that the value of using these data has been questioned. The main source of uncertainty on these estimates comes from attempts to quantify them relative to a modern-day reference (i.e. as metres above present). An alternative approach that we will propose and one that can greatly improve past sea level estimates is to focus on the Pliocene glacial-interglacial sea level amplitude. We will reconstruct the glacial-interglacial sea level amplitude for 3 intervals in the mid-Pliocene using analysis of sediments recovered from the drilling of ocean sediment cores. Specifically, we will measure the geochemical composition (the isotopes of oxygen, magnesium and calcium) of calcite microorganisms (benthic foraminifera) to reconstruct past ice volume. In the absence of a modern-day reference we will simulate both the Pliocene glacial (cooler climate intervals) and interglacial (warmer climate intervals) extent of the Antarctic and Northern Hemisphere Ice Sheets (principally the Greenland Ice Sheet) and compare this with the sea level data that we will produce. We will then be able to determine what was the magnitude of Antarctic ice sheet melt during the past. Combining two groups based in the UK and US, the ice sheet models used will include the Penn State Ice Sheet Model (PSU-ISM) and the BISICLES ice sheet model. The treatment of the grounding line physics (the point at which grounded ice becomes floating ice shelf) is very different in these two models. The PSU-ISM requires additional processes (ice shelf hydrofracture and ice cliff failure) to simulate Antarctic retreat that was consistent with Pliocene sea level maxima. By using the BISICLES model, which has much higher resolution at the grounding line, we will be able to test whether these processes are needed to simulate ice retreat consistent with our measured Pliocene sea level amplitudes. Finally, we will use what we learn to produce a new set of future sea level estimates that are constrained using the palaeoclimate data. These will have tighter constraints than previous future sea level projections, enabling a more accurate estimate of the risk of future sea level rise from Antarctica.

据估计，在容易受到海平面上升影响的社区，由于直接丧失土地或增加洪水风险，世界上有5％的人口居住在目前海平面不到5米的土地上。社会更广泛地可能会受到位于海岸的关键基础设施的中断影响。电站，以及流离失所社区的运动。南极冰盖是促进未来海平面上升和未来南极冰盖变化预测的最大潜在贡献者，也具有最大的估计范围。这使得难以准确确定未来海平面上升的风险。由于南极冰损失的海平面升高并未均匀分布在整个海洋中，因此南极冰盖的撤退会不成比例地影响远处最远的海岸线，例如欧洲和北美的海岸线。在此提案中，我们将通过重建在上新世中期（大约300万年前）的暖气间隔内重建冰盖的变化，从而改善南极冰盖变化的预测。上新世中期是大气二氧化碳与当天相似的最后一个地质间隔。该提案将着重于重建冰冷阶段和温暖的冰川间状态之间中新世海平面变化的幅度。我们将使用这些数据作为两种类型的冰盖模型的约束。最近的工作将上新世冰川间海平面最大值作为对南极冰盖模型的限制，并导致在人为变暖下从南极从南极上升的未来海平面上升。但是，随后的工作表明，不可能准确地确定绝对上新世海平面最大值，因此使用这些数据的价值已经受到质疑。这些估计值的不确定性的主要来源是试图相对于现代参考来量化它们的尝试（即，如上米）。我们将提出的一种替代方法，可以极大地改善过去的海平面估计值是专注于上新世冰川间 - 冰川海平面的幅度。我们将使用从海洋沉积物核心钻探中回收的沉积物进行分析，重建冰川冰上的海平面幅度3个间隔。具体而言，我们将测量方解石微生物（底栖有孔虫）的地球化学成分（氧，镁和钙的同位素）以重建过去的冰量。在没有现代参考的情况下，我们将模拟南极和北半球冰片（主要是格陵兰冰板）的上新世冰川（较凉的气候间隔）和冰间（较温暖的气候间隔）范围，并将其与海相比我们将生成的级别数据。然后，我们将能够确定过去融化的南极冰盖的大小是多少。结合了英国和美国的两个组，所使用的冰盖模型将包括宾夕法尼亚州冰盖模型（PSU-ism）和双杆冰盖模型。在这两种模型中，接地线物理学的处理（接地冰成为浮冰架的点）非常不同。 PSU主义需要其他过程（冰架氢裂和冰悬崖失败），以模拟与上新世海平面最大值一致的南极撤退。通过使用在接地线上具有更高分辨率的双菌素模型，我们将能够测试是否需要这些过程来模拟与我们测得的上新世海平面幅度一致的冰撤退。最后，我们将使用我们学会的知识来生成一套新的未来海平面估计，这些估计是使用古气候数据来限制的。这些将比以前的海平面预测具有更严格的限制，从而更准确地估计了南极从南极升高的风险。