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Depositional patterns and records in sediment drifts off the Antarctic Peninsula and West Antarctica

南极半岛和南极洲西部沉积物的沉积模式和记录

基本信息

批准号：
NE/J006548/1
负责人：
Robert Larter
金额：
$ 35.93万
依托单位：
British Antarctic Survey
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2014
资助国家：
英国
起止时间：
2014 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FJ006548%2F1
关键词：
Depositional patterns records sediment drifts

项目摘要

The biggest uncertainty in predictions of sea-level rise is what the contribution will be from the great ice sheets on Antarctica and Greenland as climate warms. The West Antarctic Ice Sheet and the Antarctic Peninsula Ice Sheet are the cause of greatest concern, as they are showing signs of significant ice loss and there are theoretical reasons for expecting them to be most vulnerable. Important sources of information for helping to predict how these ice sheets will change as climate warms are records of their response to past climate changes contained in sea bed sediments around Antarctica. Such records extend further back in time than ice cores from the ice sheets themselves. They can also show how the margins of the ice sheets interacted with changes in ocean temperature and circulation, which recent studies have identified as having an important influence on ice sheets.Although sedimentary records in the shallow seas close to Antarctica have been periodically disturbed or removed by past expansions of the ice sheets, there are places in the nearby deep ocean where sediments have accumulated continuously over millions of years. The international Integrated Ocean Drilling Program is considering a proposal to send a drilling ship to collect long sediment cores from some of these places. However, before this is done additional survey data are needed to find the sites that will provide the most continuous, detailed records and to make sure that it will be safe to drill those sites. In this research proposal we are seeking funding to collect this essential survey data. On the same expedition we also propose to collect short sediment cores for pilot studies to confirm that the analytical methods we intend to apply to the longer drill cores will provide reliable information about sediment ages, past climate and past ice sheet behaviour. One of the major difficulties in studying sediment records from the sea bed around Antarctica has been obtaining reliable ages from the sediments. This is because the types of microfossils that are analysed to determine sediment ages in drill cores from most of the world's oceans are rare or absent in many sediment cores collected near Antarctica. By carrying out detailed survey and studying short cores we hope to identify sites where there are sufficient numbers of these microfossils to apply the standard dating techniques. We also plan to test whether a new method of dating sediments that is based on analysis of their magnetic properties will work in the area of the proposed drill sites. It has recently been shown that in many places analysis of the magnetic properties of sea bed sediments can provide records of past changes in the intensity of the Earth's magnetic field, and comparison of these records to well-dated reference records allows ages to be assigned to sediments throughout a core. By comparing ages obtained using this method with ones obtained from microfossils, where they are present, we will be able to find out how well the magnetic dating method works in the study area. If the magnetic method works well, we will be able to establish detailed age models for drill cores without dependence on microfossils, which will greatly extend the area that can be studied by drilling and allow more detailed records of past changes to be derived from the drill cores.

预测海平面上升的最大不确定性是，随着气候变暖，南极洲和格陵兰岛的大冰盖将做出什么贡献。西南极冰盖和南极半岛冰盖是最令人担忧的原因，因为它们显示出大量冰川消失的迹象，从理论上讲，有理由认为它们最脆弱。帮助预测随着气候变暖这些冰盖将如何变化的重要信息来源是它们对南极洲周围海底沉积物中过去气候变化的反应的记录。这样的记录可以追溯到比冰盖本身的冰芯更早的时间。它们还可以显示冰盖边缘如何与海洋温度和环流的变化相互作用，最近的研究发现，这对冰盖有重要影响。尽管南极洲附近浅海的沉积记录曾周期性地被冰盖过去的扩张所干扰或移除，但在附近的深海中，沉积物在数百万年内不断积累。国际综合海洋钻探计划正在考虑一项提议，即派遣一艘钻井船从其中一些地方收集长沉积物岩心。然而，在此之前，需要更多的调查数据来找到将提供最连续、最详细的记录的地点，并确保对这些地点进行钻探将是安全的。在这项研究提案中，我们正在寻求资金来收集这一重要的调查数据。在同一次考察中，我们还建议收集短沉积物岩芯进行初步研究，以确认我们打算应用于较长钻探岩芯的分析方法将提供有关沉积物年龄、过去气候和过去冰盖行为的可靠信息。研究南极周围海床的沉积物记录的主要困难之一是从沉积物中获得可靠的年龄。这是因为，在南极洲附近采集的许多沉积岩心中，用于确定世界上大多数海洋钻探岩芯中沉积年龄的微化石类型很少，甚至没有。通过开展详细的调查和研究短岩心，我们希望找到有足够数量的这种微化石的地点，以应用标准的测年技术。我们还计划测试一种基于对沉积物磁性分析的新方法是否适用于拟议的钻探地点。最近的研究表明，在许多地方，对海底沉积物磁性的分析可以提供过去地球磁场强度变化的记录，将这些记录与有日期的参考记录进行比较，就可以确定整个岩心的沉积物的年龄。通过将使用这种方法获得的年龄与从微化石中获得的年龄进行比较，我们将能够发现磁测年方法在该研究地区的应用情况。如果磁法效果良好，我们将能够在不依赖微化石的情况下建立详细的钻芯年龄模型，这将极大地扩大可以通过钻探进行研究的区域，并允许从钻芯中推导出更详细的过去变化记录。