NERC-FAPESP: the Marine Gateways Project - Quantifying the causes and climatic consequences of the opening of the South Atlantic

海洋环流是由不同密度的水团驱动的。其中大部分是在海洋-大陆边界产生的，在那里，近内陆的海洋与全球海洋的联系有限，使它们能够进化出不同的温度或盐度。这些边缘盆地通常是在大陆板块合并时形成的——今天的地中海就是一个很好的例子——或者是分裂时形成的——大约1亿年前冈瓦纳大陆分裂时南大西洋的开放是另一个例子。因此，这些海洋门户的演变对海洋环流的模式及其活力有着深远的影响。众所周知，不断变化的古地理在重大气候变化中发挥着关键作用，例如从温室到冰窖的转变，因此，海洋通道是几个即将到来的国际科学钻探项目的重点。当海洋通道只允许非常有限的交换时，大量的蒸发岩可能在边缘海域沉淀。这些在当今世界上尚未形成的巨型盐岩，其规模之大足以改变全球海洋的盐度。最近的盐巨兽形成于大约500万年前的地中海。利用对边缘盆地不同比例的海洋和河流水的响应同位素，结合盒模型和全球气候模拟，已经有可能重建和量化地中海-大西洋交换，并表明这一门户演变的主要气候影响比蒸发岩降水早几百万年。在这个项目中，我们建议将这些技术应用于更古老、更大的南大西洋盐巨人，在那里，对于门户进化的位置和时间以及开放南大西洋对气候的影响仍然存在争议。为了做到这一点，我们正在扩大布里斯托尔和乌得勒支之间的现有合作，那里的研究人员领导了许多大西洋-地中海门户研究，包括圣保罗大学的研究人员，他们在南大西洋含盐演替的古地理和年代学方面具有重要的专业知识。因此，这是NERC-FAPESP全球合作伙伴种子玉米应用程序。在两年的时间里，我们建议在巴西进行由圣保罗大学领导的实地考察，在布里斯托尔大学对现有的全球气候模拟进行试点同位素分析和GCM分析，同时在乌得勒支大学进行盒子建模。在布里斯托尔举行审查初步试点数据的早期会议之后，将在圣保罗举行项目中期模型数据整合讲习班。研讨会将向南美洲更广泛的研究界开放，我们将特别鼓励早期研究人员的参与。此外，我们将支持圣保罗博士生申请实习奖学金（FAPESP-BEPE），以便积极参与项目。该项目的最后阶段将吸引参与与当前科学钻探项目相关的海洋门户研究的研究人员，其中三个由英国科学家领导。在布里斯托尔举行的最后一次会议将是一个论坛，既可以展示该项目的科学成果，也可以启动欧盟成本行动申请，以支持正在进行的社区建设和合作研究活动。这是为了支持和扩大从事长期科学钻探项目的科学界，重点是海洋门户。

Ocean circulation is driven by water masses with different densities. Much of this is generated at the ocean-continent boundary where near landlocked seas have a restricted connection with the global ocean, allowing them to evolve a different temperature or salinity. These marginal basins often form when continental plates coalesce - the Mediterranean today is a good example of this - or disaggregate - the opening of the South Atlantic around 100 million years as Gondwana broke apart is another. The evolution of these marine gateways therefore has a profound impact on the patterns of ocean circulation and its vigour. Changing palaeogeography is known to play a key role in major climate reorganisations such as the transition from greenhouse to icehouse conditions, and marine gateways are therefore the focus of several upcoming international scientific drilling projects.When marine gateways allow only very limited exchange, large volumes of evaporites may precipitate in the marginal seas. These salt giants, which are not forming in the world today can be sufficiently large to change the salinity of the global ocean. The most recent salt giant formed around 5 million years ago in the Mediterranean. Using isotopes that respond to the different proportions of ocean and river water feeding the marginal basin, integrated with box modelling and global climate simulations, it has been possible to reconstruct and quantify Mediterranean-Atlantic exchange and show that the major climate impact of this gateway evolution precedes evaporite precipitation by several million years. In this project we propose to develop and apply these techniques to the older and larger South Atlantic salt giant where there is still controversy over the location and timing of gateway evolution and hence the climatic impact of opening the South Atlantic. To do this we are extending an existing collaboration between Bristol and Utrecht where researchers have led much of the Atlantic-Mediterranean gateway research, to include researchers at the University of Sao Paulo who have essential expertise in the palaeogeography and chronology of the South Atlantic salt-bearing successions. This is therefore a joint NERC-FAPESP global partnership seedcorn application.Over two years we propose to undertake fieldwork in Brazil led by the University of Sao Paulo, pilot isotope analyses and GCM analysis of existing global climate simulations at the University of Bristol, in parallel with box-modelling at Utrecht University. An early meeting in Bristol to review the initial pilot data will be followed by a mid-project model-data integration workshop in Sao Paulo. The workshop will be open to the wider research community in South America and we will particularly encourage the involvement of Early Stage Researchers. In addition, we will support Sao Paulo PhD students to apply for internship scholarships (FAPESP-BEPE) in order to be actively involved in the project. The last phase of this project will draw in researchers involved in marine gateway research associated with current scientific drilling projects, three of which are led by UK scientists. The final meeting in Bristol will be a forum both for presenting the scientific results of the project and for initiating an EU COST-Action application to support on-going community-building and collaborative research activities. This is designed to support and expand the scientific community engaged with long-term scientific drilling projects focused on marine gateways.