权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Unlocking the potential of IODP site U1534 to reveal the sensitivity of Atlantic Overturning Circulation to "cold water route" variability.

释放 IODP 站点 U1534 的潜力，揭示大西洋翻转环流对“冷水路线”变化的敏感性。

基本信息

批准号：
NE/T010908/1
负责人：
Victoria Louise Peck
金额：
$ 4.72万
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：
2020
资助国家：
英国
起止时间：
2020 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FT010908%2F1
关键词：
Unlocking potential IODP site U1534

项目摘要

The Atlantic meridional overturning circulation (AMOC) plays a fundamental role in regulating the Earth's climate. Past reductions in the strength of this overturning circulation have been associated with dramatic cooling in the northern hemisphere. A recent trend of cooling in the subpolar Atlantic Ocean and warming in the Gulf Stream region is indicative of a weakening of the AMOC. General Circulation Models are typically biased toward a stable AMOC and unable to replicate the observed sensitivity of the AMOC to climate forcing. This model bias in AMOC stability suggests that certain parameters are inaccurately represented, compromising our ability to predict future AMOC change. One element of the AMOC that remains poorly understood is the role of Antarctic Intermediate Water (AAIW). AAIW is one of the primary water masses characterizing the northward-flowing upper limb of the AMOC. Counter-balancing the southward flow of North Atlantic Deep Water, AAIW currently penetrates as far as 20 deg N in the North Atlantic. Despite a recent surge in research effort a consensus on the role of AAIW in contributing to AMOC variability has not been achieved. Today, AAIW is primarily formed in the SE Pacific and SW Atlantic Oceans. AAIW and its precursor, Subantarctic Mode Water, are advected eastward through Drake Passage along the Subantarctic Front (SAF). This injection of cold, low salinity Pacific water into the South Atlantic Ocean is commonly referred to as the 'cold water route. Variability in the connectivity between the Pacific and Atlantic Oceans via this cold water route may modify the physical properties of AAIW forming in the SW Atlantic Ocean, in turn affecting the heat and salinity budget of the AMOC. It has been shown that during the last glacial period the SAF was likely in a more northerly position relative to today. Truncated by South America, the SAF would not have transported Pacific-sourced Subantarctic Mode Water into the South Atlantic effectively closing the cold water route. During the deglaciation the SAF migrated south and once established within Drake Passage the route was open and Pacific-sourced water was injected into the South Atlantic. The coincidence of this opening of the cold water route and reinvigoration of the AMOC demands further investigation to constrain the sensitivity of AMOC to Pacific-Atlantic connectivity through Drake Passage. Marine sediments recovered at IODP Site U1534 on Expedition 382 present the first opportunity to constrain variability in endmember physical and geochemical properties of AAIW as it enters the upper limb of the AMOC over multiple glacial-interglacial cycles. This proposal will generate a definitive age model for U1534 and will form the foundation for a future NERC grant to address the question of the cold water route influence on AMOC. In addition, the advances proposed here will benefit numerous associated projects with national and international collaborators and potential studentships and optimise the outputs of this UK-lead ocean drilling effort.

大西洋经向翻转环流（AMOC）在调节地球气候方面发挥着基础性作用。过去这种翻转环流强度的减弱与北半球的急剧降温有关。最近副极地大西洋变冷和墨西哥湾流地区变暖的趋势表明 AMOC 正在减弱。大气环流模型通常偏向于稳定的 AMOC，并且无法复制观察到的 AMOC 对气候强迫的敏感性。 AMOC 稳定性的这种模型偏差表明某些参数的表示不准确，从而损害了我们预测未来 AMOC 变化的能力。 AMOC 中人们对南极中层水 (AAIW) 的作用仍知之甚少的一项内容。 AAIW 是 AMOC 北流上缘的主要水团之一。为了平衡北大西洋深水向南的流动，AAIW 目前已渗透至北大西洋北纬 20 度。尽管最近研究工作激增，但关于 AAIW 在导致 AMOC 变异中的作用尚未达成共识。如今，AAIW 主要形成于东南太平洋和西南大西洋。 AAIW 及其前身亚南极模式水沿着亚南极锋 (SAF) 通过德雷克海峡向东平流。这种将寒冷、低盐度的太平洋水注入南大西洋的方式通常被称为“冷水航线”。太平洋和大西洋之间通过这条冷水航线的连通性的变化可能会改变西南大西洋形成的 AAIW 的物理特性，进而影响 AMOC 的热量和盐度预算。研究表明，在末次冰期期间，SAF 的位置可能比今天更靠北。由于被南美洲截断，新加坡武装部队无法将来自太平洋的亚南极模式水输送到南大西洋，从而有效地关闭冷水航线。在冰消期期间，新加坡武装部队向南迁移，一旦在德雷克海峡内建立，路线就开放了，来自太平洋的水被注入南大西洋。冷水航线的开通和 AMOC 的重振同时发生，需要进一步调查，以限制 AMOC 对通过德雷克海峡连接太平洋与大西洋的敏感性。 382 号远征中在 IODP 站点 U1534 回收的海洋沉积物首次有机会限制 AAIW 在多个冰期-间冰期循环中进入 AMOC 上肢时端元物理和地球化学性质的变化。该提案将为 U1534 生成一个明确的年龄模型，并将为未来 NERC 拨款奠定基础，以解决冷水航线对 AMOC 的影响问题。此外，这里提出的进展将有利于与国内和国际合作者以及潜在学生的众多相关项目，并优化英国主导的海洋钻探工作的产出。