Beyond the instrumental record: Reconstructing Atlantic overturning over the past 7000 yrs (ReconAMOC)

超越乐器记录：重建过去 7000 年的大西洋倾覆 (ReconAMOC)

基本信息

批准号：
NE/S009736/1
负责人：
David Thornalley
金额：
$ 71.66万
依托单位：
University College London
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2019
资助国家：
英国
起止时间：
2019 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FS009736%2F1
关键词：
Beyond instrumental record Reconstructing Atlantic

项目摘要

The Atlantic meridional overturning circulation (AMOC) - part of the so-called 'ocean conveyor belt' - is a key component of Earth's climate system. It involves the northward transport of warm surface waters to the high latitude North Atlantic, where they cool (releasing heat to the atmosphere), sink and flow back southwards at depth. Changes in the AMOC are thought to alter global temperature and precipitation patterns, regional sea-level, and socio-economically important marine ecosystems. There are concerns regarding the strength and stability of AMOC in the future. This is because predicted surface ocean warming and freshening could weaken the formation of dense water that helps drive the AMOC. Earlier research suggests that the AMOC may have different stable states, raising the possibility that the AMOC could rapidly switch to a weaker, or even an 'off', state, having a severe impact on global climate. IPCC models do not predict an abrupt weakening of the AMOC under typical 21st century scenarios; yet there are suggestions that current climate models may be excessively stable.NERC and the international community have invested heavily in monitoring the AMOC, including the implementation of the RAPID array since 2004 and more recently the OSNAP array. Since observations began in 2004, AMOC has weakened at a rate ten times faster than predicted by most models. Yet the extent to which this decline can be attributed to natural multi-decadal variability is uncertain. The limited time span of the RAPID array means we are unable to gain an understanding of the nature of AMOC variability on timescales longer than interannual-to-decadal. Therefore we must turn to geological archives to reconstruct AMOC changes beyond the instrumental record. Yet there are no existing records to provide perspective on recent AMOC variability at multi-decadal and longer timescales. Using recent, novel techniques to constrain past variability, coupled with exceptional sediment archives, ReconAMOC will constrain past AMOC variability on decadal to centennial timescales, generating records for the last 7000 years that will become benchmark constraints on AMOC behaviour. We will focus on the past 7000 years because the climate was not dramatically different to the present day, and remnant glacial ice sheets had melted away so that the major features of deep Atlantic circulation were broadly similar to modern. ReconAMOC deploys a twin approach that utilizes (i) the characteristic subsurface temperature AMOC fingerprint, and (ii) the deep western boundary current response to AMOC change. We have verified these new paleoclimate approaches against variability in the instrumental record and demonstrated their applicability through an extensive pilot study. ReconAMOC is therefore a low risk yet ambitious project, bringing together an international team of collaborators, that will meet a long-sought and much-needed requirement of a wide range of climate scientists and modellers. ReconAMOC will enable testing and improvement of model simulations of AMOC that help facilitate assessment of the vulnerability of the AMOC to climate change, and permit the investigation of the role of AMOC on other components of the climate system. The topics addressed by ReconAMOC are key research targets at national UK (e.g. identified strategic science themes and goals within the NERC strategy) and international (e.g. CMIP6, IMAGESII, SCOR, PAGES, IODP and NSF) levels. Specifically, the ReconAMOC proposal builds on the NERC programmes RAPID, RAPID-WATCH, and RAPID-AMOC, in which interannual to multi-decadal variability in the AMOC is a central focus, as well as NERC programme ACSIS examining interannual to decadal climate variability in the Atlantic.

大西洋子午倾覆循环（AMOC） - 所谓的“海洋传送带”的一部分 - 是地球气候系统的关键组成部分。它涉及向北运输温暖的地表水到北大西洋高纬度的地方，在那里它们冷却（向大气中释放热量），深入下沉并向南流动。 AMOC的变化被认为会改变全球温度和降水模式，区域海平面和社会经济重要的海洋生态系统。人们对未来AMOC的强度和稳定性存在担忧。这是因为预测的表面海洋变暖和清新可以削弱有助于驱动AMOC的密集水的形成。较早的研究表明，AMOC可能具有不同的稳定状态，这增加了AMOC可以迅速转变为较弱甚至“关闭”状态的可能性，对全球气候产生了严重影响。 IPCC模型不会预测在典型的21世纪情景下AMOC突然削弱；然而，有人建议当前的气候模型可能过于稳定。NERC和国际社会在监视AMOC方面进行了大量投资，包括自2004年以来的快速阵列实施以及最近的OSNAP阵列。自从2004年开始观察以来，AMOC的削弱速度比大多数模型的预期快十倍。然而，尚不确定这种下降可以归因于自然多年多变异的程度。快速阵列的有限时间跨度意味着我们无法了解时间尺度上的AMOC变异性的性质，而不是年龄段到年龄段。因此，我们必须转向地质档案，以重建超出器乐记录的AMOC变化。然而，没有现有的记录可以提供有关多年代和较长时间尺度上最近的AMOC变异性的观点。使用最新的新技术来限制过去的变异性，再加上出色的沉积物档案，Reconamoc将限制过去7000年的decadal decadal变异性，从而产生对AMOC行为的基准限制的记录。我们将重点关注过去7000年，因为气候与当今的气候并没有大不相同，而残留的冰川冰盖已经融化了，因此深层大西洋循环的主要特征与现代广泛相似。 ReconAmoc部署了一种使用（i）特征地下温度AMOC指纹的双胞胎方法，以及（ii）深层边界对AMOC变化的响应。我们已经验证了这些新的古气候方法，以防止工具记录中的可变性，并通过广泛的试点研究证明了它们的适用性。因此，Reconamoc是一个低风险但雄心勃勃的项目，将国际合作者团队汇总在一起，这将满足众多气候科学家和建模者的备受追捧和急需的要求。 Reconamoc将实现AMOC模型模拟的测试和改进，以帮助评估AMOC对气候变化的脆弱性，并允许研究AMOC对气候系统其他组件的作用。 ReconAmoc提出的主题是英国国家（例如NERC战略中确定的战略科学主题和目标）和国际（例如CMIP6，ImageII，SCOR，SCOR，PAGES，PAGES，IODP和NSF）的主要研究目标。具体而言，Regamoc提案建立在NERC计划的快速，快速观察和快速AMOC的基础上，其中AMOC的年婚与多年差异性是一个核心重点，以及NERC计划ACSIS ACSIS检查大西洋大西洋的年间到衰老的气候变化。