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

在海平面上升的预测中，最大的不确定性在于，随着气候变暖，南极洲和格陵兰岛的大冰原将对海平面上升产生何种影响。南极西部冰原和南极半岛冰原是最令人担忧的原因，因为它们显示出显著的冰损失迹象，理论上有理由认为它们是最脆弱的。帮助预测这些冰盖将如何随着气候变暖而变化的重要信息来源是它们对南极洲周围海床沉积物中过去气候变化的反应记录。这些记录比冰原本身的冰芯更久远。它们还可以显示冰盖的边缘如何与海洋温度和环流的变化相互作用，最近的研究已经确定这些变化对冰盖有重要影响。虽然靠近南极洲的浅海的沉积记录被过去冰盖的扩张周期性地扰乱或移除了，但在附近的深海中，有些地方的沉积物已经连续积累了数百万年。国际综合海洋钻探计划正在考虑一项提议，即派遣一艘钻探船从这些地方收集长沉积物岩心。然而，在此之前，需要额外的调查数据来找到能够提供最连续、最详细记录的地点，并确保在这些地点钻探是安全的。在这项研究计划中，我们正在寻求资金来收集这些重要的调查数据。在同一次探险中，我们还建议收集短沉积物岩心进行初步研究，以确认我们打算应用于较长钻探岩心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。研究南极洲周围海床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。这是因为在世界上大多数海洋的岩心中，用来分析确定沉积物年龄的微化石类型在南极洲附近收集的许多沉积物岩心中是罕见的或不存在的。通过详细的调查和研究短岩心，我们希望找到有足够数量的这些微化石的地点，以应用标准的测年技术。我们还计划测试一种基于磁性分析的沉积物测年新方法是否适用于拟议的钻探地点。最近有研究表明，在许多地方，对海底沉积物磁性的分析可以提供地球磁场强度过去变化的记录，并将这些记录与年代确定的参考记录进行比较，可以确定整个岩心沉积物的年龄。通过将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，我们将能够发现磁定年法在研究区域的效果如何。如果磁法效果良好，我们将能够建立详细的岩心年龄模型，而不依赖于微化石，这将极大地扩展可以通过钻探研究的领域，并允许从岩心中获得更详细的过去变化记录。

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.