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Diatom Silica Oxygen Isotope Records from the Late Quaternary Antarctic Margin

晚第四纪南极边缘硅藻硅氧同位素记录

基本信息

批准号：
NE/G004137/1
负责人：
Melanie Leng
金额：
$ 28.84万
依托单位：
British Geological Survey
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2009
资助国家：
英国
起止时间：
2009 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FG004137%2F1
关键词：
Diatom Silica Oxygen Isotope Records

项目摘要

Antarctica and its ice sheets have played, and continue to play, a major role in the global ocean-atmosphere system, hence, it is critical that we have a sound understanding of the past behaviour of Antarctica and it's ice sheets with a view to understanding their potential future variability under a warming climate. The Southern Ocean is a key component of the thermohaline circulation of the world's oceans and the re-distribution of heat and salt around the oceans is integral to processes that regulate rapid climate transitions. Computer modelling results have shown that sufficient melt water input to the Antarctic continental shelf area is capable of shutting down the formation of cold, salty deep water in Antarctica hence upsetting the balance of the thermohaline circulation and the ocean-climate system of the Northern Hemisphere. In order to further investigate these processes that originate in Antarctica, it is necessary to understand the transfer mechanisms of ocean-climate signals from the Antarctic ice sheets, across the continental margin seas, into the Southern Ocean. Exceptionally well-preserved Antarctic margin sediment cores, recovered during the last decade, contain an excellent archive of these ice-ocean-climate interactions, often on seasonal timescales, from the end of the last ice age and throughout the recent warm interglacial (the Holocene). The cores are seasonally layered through the deglaication, intermittently layered through the Holocene, and the layers are dominated by fossil planktonic diatoms (algae); individual species of which are sensitive to sea surface conditions including sea ice concentration, fresh water influx, and open ocean influence upon the margin. Following the last ice age, these Holocene Antarctic sediments record climate fluctuations of tens to thousands of years long and whatever environmental forcing mechanism is responsible for these fluctuations, the changes are likely to be felt in the Antarctic coastal regions first, and the cores proposed for this research are located in prime positions to record these changes. Diatom oxygen isotope measurements represent an under-utilised technique that provides a means of obtaining oxygen isotope records in high latitude environments. The measurement of oxygen isotopes in diatoms is a widely used proxy in the study of the history of lakes, however, to date there have been many fewer attempts to use records of diatom oxygen isotopes in the oceans. Studies that have taken place have demonstrated the sensitivity of diatom oxyegn isotope measurements in polar and sub-polar waters to changes in surface ocean environmental parameters such as salinity, freshwater input and sea surface temperature. The research proposed here will be the first attempt to produce diatom oxygen isotope records from the Antarctic margin, a region sensitive to the waxing and waning of the Antarctic ice sheets in terms of melt water through-put to the Southern Ocean. We propose to investigate the evolution of seasonality along the Antarctic margin since the last ice age, and also the processes involved in producing the sediment record, by relating diatom oxygen isotope measurements on season-specific diatom taxa (i.e. diatom species that thrived particularly in spring or autumn) to relative freshwater influx to the coast, from either melted terrestrial ice or sea ice. We also hope to show that the diatom oxygen isotope measurements will be low at the end of the last ice age, as a large quantity of old ice sheets were melting, and will be higher during warmer time periods of the Holocene when ice sheets were at a minimum.

南极洲及其冰盖在全球海洋-大气系统中发挥了并将继续发挥重要作用，因此，我们必须正确了解南极洲及其冰盖过去的行为，以便了解它们在气候变暖的情况下未来可能发生的变化。南大洋是世界海洋温盐环流的一个关键组成部分，海洋周围热量和盐分的重新分布是调节气候快速转变过程的一个组成部分。计算机模拟结果表明，如果有足够的融水流入南极大陆架地区，就能够阻止南极洲寒冷、含盐的深水的形成，从而破坏北方温盐环流和海洋气候系统的平衡。为了进一步研究这些起源于南极洲的过程，有必要了解海洋气候信号从南极冰盖穿过大陆边缘海进入南大洋的传输机制。在过去的十年中，南极边缘沉积物岩心保存得非常完好，包含了这些冰-海洋-气候相互作用的优秀档案，通常是在季节性时间尺度上，从最后一个冰河时代结束到最近的温暖间冰期（全新世）。岩芯季节性分层通过deglaification，间歇性分层通过全新世，和层的化石硅藻（藻类）占主导地位，其中个别物种是敏感的海面条件，包括海冰浓度，淡水流入，并开放的海洋影响的边缘。在最后一个冰河时代之后，这些全新世南极沉积物记录了数十年至数千年的气候波动，无论环境强迫机制是如何造成这些波动的，这些变化都可能首先在南极沿海地区感受到，而为这项研究提出的岩心位于记录这些变化的主要位置。硅藻氧同位素测量代表了一种未充分利用的技术，提供了一种在高纬度环境中获得氧同位素记录的手段。硅藻中氧同位素的测量是湖泊历史研究中广泛使用的替代物，然而，迄今为止，使用海洋中硅藻氧同位素记录的尝试要少得多。已经进行的研究表明，在极地和次极地沃茨进行的硅藻氧同位素测量对诸如盐度、淡水输入量和海面温度等表层海洋环境参数的变化十分敏感。这里提出的研究将是第一次尝试从南极边缘产生硅藻氧同位素记录，南极边缘是一个对南极冰盖在融水流入南大洋方面的盈亏敏感的地区。我们建议调查的演变季节性沿着南极边缘自上一个冰河时代以来，还涉及在生产的沉积物记录的过程中，有关硅藻氧同位素测量季节性特定的硅藻类群（即硅藻物种，特别是在春季或秋季蓬勃发展）相对淡水流入海岸，无论是融化的陆地冰或海冰。我们还希望表明，硅藻的氧同位素测量将在最后一个冰河时代结束时较低，因为大量的旧冰盖正在融化，而在全新世的温暖时期，当冰盖处于最小值时，硅藻的氧同位素测量值将较高。