Climate Change and the Oceans

气候变化与海洋

• 批准号: NE/D00876X/1
• 负责人: Gavin Foster
• 金额: $ 59.08万
• 依托单位: University of Bristol
• 依托单位国家: 英国
• 项目类别: Fellowship
• 财政年份: 2006
• 资助国家: 英国
• 起止时间: 2006 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FD00876X%2F1
• 关键词: Climate; Change; Oceans

The research I propose concerns two fundamental feedback processes within the Earth's climate system / the concentration of atmospheric CO2 and the circulation strength of the oceans. Feedback processes amplify any external forcing of the climate caused by, for example, variations in the Earth's orbit around the sun. Both processes play important roles in the modern climate system, yet their roles in the past, and in particular, their predicted roles in future climate change are uncertain. It is the principal aim of this proposal to reduce this uncertainty by reconstructing the behaviour of these two systems at key times in the past. The first part of the proposed research concerns the concentration of carbon dioxide in the atmosphere. CO2 is an important greenhouse gas such that variations in the amount of atmospheric CO2 are thought to have an important control on the Earth's climate. Indeed, over the last 2.5 million years the climate of the Earth has oscillated between periods of extreme cold (called glacial periods) and comparable warmth (interglacial periods like today). Importantly, these swings in climate have been accompanied by changes in the concentration of atmospheric CO2 (pCO2). The overall driving force for the waxing and waning of ice sheets are subtle variations in the orbit of the Earth around the sun, which influence the amount and seasonal distribution of solar radiation received at high latitudes. Variations in the concentrations of CO2 probably globalise and enhance this orbital forcing. The exact mechanisms responsible for altering pCO2 are not known but probably involve the oceans (the largest store of carbon on the planet that can respond with sufficient rapidity). In order to examine this role, I propose to generate a record of past ocean acidity (pH) in a variety of sensitive areas of the ocean using the boron isotopic composition of planktic and benthic foraminifera (calcareous single celled protists that are common throughout the ocean and are preserved in deep sea sediments). Since the acidity of the ocean largely determines pCO2, I will be able, from this record, to identify how CO2 is stored and released from the deep sea during the waxing and waning of the ice sheets and potentially isolate its role in causing the transitions from one climate state to another. The second part of this proposal concerns the circulation of the oceans. The Equator, which receives more heat from the sun, is hotter than the poles, and it is this temperature gradient that drives ocean (and atmospheric) circulation. The Atlantic portion of ocean circulation is a particularly important and sensitive part of the circulation system. Here, the Gulf Stream carries warm, salty water from the low latitudes to the North Atlantic. These waters then cool, lose heat to the atmosphere and become dense (salty cold water is denser than fresh warm water) and, as a result, sink. They then flow southward at depth, forming the return arm of the convection cell. The release of heat by this mode of circulation is not only important in ameliorating the climate of maritime Europe, but it can influence the overall climate of the planet by determining the water temperature in the Artic seas, where sea-ice forms. Sea-ice is highly reflective and more sea-ice results in more of the Sun's energy being reflected back into space, and hence can influence global temperature. The role of this circulation pattern in future climate scenarios is uncertain; one way to reduce this uncertainty is to examine ocean circulation in the geological past. I propose to use a new analytical technique, involving the laser microsampling of ferromanganese crusts (metallic encrustations that precipitate very slowly from seawater at depth) to reconstruct the strengths and patterns of circulation in the past when the climate was significantly colder (during glacial periods) and warmer than today (the Mid-Pliocene).

我提出的研究涉及地球气候系统中的两个基本反馈过程 /大气二氧化碳的浓度和海洋的循环强度。反馈过程扩大了由于地球围绕太阳的变化而引起的气候的任何外部强迫。这两个过程在现代气候系统中都起着重要作用，但它们在过去的角色，尤其是它们在未来气候变化中的预测作用尚不确定。该提案的主要目的是通过在过去的关键时期重建这两个系统的行为来减少这种不确定性。拟议的研究的第一部分涉及大气中二氧化碳的浓度。二氧化碳是一种重要的温室气体，因此人们认为大气二氧化碳量的变化对地球气候具有重要的控制。的确，在过去的250万年中，地球的气候在极度寒冷的时期（称为冰川时期）和可比的温暖（如今像冰间时期）在摇摆不定。重要的是，这些气候中的波动伴随着大气二氧化碳浓度的变化（PCO2）。冰盖上蜡和减弱的总体驱动力是地球围绕太阳轨道的细微变化，这会影响高纬度收到的太阳辐射的数量和季节性分布。二氧化碳浓度的变化可能全球化并增强了这种轨道强迫。负责改变PCO2的确切机制尚不清楚，但可能涉及海洋（地球上最大的碳存储，可以以足够的速度响应）。为了检查这一角色，我建议使用浮游物和底栖有孔虫的硼同位素组成在海洋各种敏感区域中产生过去的海洋酸度（pH）记录（钙质单细胞生物（钙质单细胞生物）（钙质单细胞生物，它们在整个海洋中很常见并保存在深海沉积物中）。由于海洋的酸度在很大程度上决定了PCO2，因此我将能够从该记录中确定在冰盖的上蜡和减弱期间如何从深海中存储和释放CO2，并有可能隔离其从一个气候状态到另一种气候状态的过渡中的作用。该提案的第二部分涉及海洋的循环。从太阳中获得更多热量的赤道比两极都热，正是这种温度梯度驱动了海洋（和大气）循环。海洋循环的大西洋部分是循环系统特别重要且敏感的部分。在这里，海湾溪流从低纬度的北大西洋上传送温暖而咸的水。然后，这些水冷却，流失到大气中并变得密集（咸冷水比新鲜的温水更浓），因此，下沉。然后，它们以深度向南流动，形成对流电池的回流臂。通过这种循环方式释放热量不仅在改善海洋欧洲的气候中很重要，而且可以通过确定围绕海冰形成的植物海中的水温来影响地球的整体气候。 Sea-Ice具有很高的反射性，更多的海冰会导致更多的太阳能量反射回太空，因此会影响全球温度。这种循环模式在未来的气候场景中的作用尚不确定。减少这种不确定性的一种方法是检查地质过去的海洋循环。我建议使用一种新的分析技术，涉及涉及铁龙伙壳的激光微采样（金属壳（金属包裹物，从深度处的海水沉淀出非常缓慢的沉淀）在过去的循环强度和循环模式中重建了气候的强度和循环模式，而气候在冰冷的（在冰川时期）和今天的温暖（在冰川时期）和温暖（比今天的温暖）。

项目成果

A new boron isotope-pH calibration for Orbulina universa, with implications for understanding and accounting for 'vital effects'

• DOI: 10.1016/j.epsl.2016.09.024
• 发表时间: 2016-11-15
• 期刊: EARTH AND PLANETARY SCIENCE LETTERS
• 影响因子: 5.3
• 作者: Henehan, Michael J.;Foster, Gavin L.;Wilson, Paul A.
• 通讯作者: Wilson, Paul A.