Late Quaternary changes in the Westerly Winds over the Southern Ocean

南大洋西风的晚第四纪变化

• 批准号: NE/K004514/1
• 负责人: Dominic Hodgson
• 金额: $ 84.67万
• 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: 2013
• 资助国家: 英国
• 起止时间: 2013 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FK004514%2F1
• 关键词: Late; Quaternary; changes; Westerly; Winds

Public summaryClimate changes have been attributed to the increasing concentrations of greenhouse gases (e.g. CO2) in our atmosphere. These measured increases in atmospheric CO2 are partly controlled by changes in the ability of the world's oceans to absorb CO2 at the surface (e.g. via diffusion and the biological pump) versus release of old carbon to the atmosphere from deep ocean reservoirs (e.g. via upwelling and out gassing).Of the world's oceans, the Southern Ocean has been identified (by models) as playing a major role in modulating global atmospheric CO2, particularly on glacial-interglacial timescales. This is because surface nutrients are high indicating their incomplete utilisation by the biological pump, and because wind driven changes in ocean circulation can bring old carbon stored in deep ocean reservoirs to the surface. Changes in the strength of the Southern Hemisphere Westerly Winds (SHW) influence Southern Ocean circulation and control how much of this carbon rich deep water reaches the ocean surface. Thus any change in the strength or position of the SHW such as the recently observed intensification of the winds, could influence whether the Southern Ocean acts as a net source or sink of atmospheric CO2.At present our understanding of past changes in the SHW is based mainly on geological proxy records from South America, one record from South Africa, and two from New Zealand. With the exception of Campbell Island there are no studies of changes in the SHW in the Southern Ocean where the core of the SHW wind belt is located. This lack of spatial resolution has been identified by Stager et al. (2012) as a major limitation in our understanding of past climate. As a result, although present General Circulation Models use a variety of processes (biology, ocean chemistry, and ocean physics), they either fail to produce the magnitude of past atmospheric CO2 variations or do not agree with geologic field data. Here we propose to substantially improve the spatial resolution of the geological data by generating proxy records in each of the three major sectors of the Southern Ocean, focusing on sub-Antarctic islands situated in the core belt of the SHW. We apply a novel diatom proxy for past wind strength independently controlled by a range of standard sedimentological and biogeochemical proxies. The new proxy is based on the direct transfer of sea spray across the islands by wind, and its effect on the salinity of west coast lakes and ponds. This works on sub-Antarctic islands where there is a marked west-east conductivity gradient in water bodies across the island. This conductivity gradient determines which diatom communities are present in the lakes. Once this diatom- conductivity relationship is established quantitatively, the subfossil diatom communities deposited in radiocarbon dated sediment cores can be used to reconstruct changes in conductivity through time, and hence past relative wind strength.We have demonstrated that this approach works at Macquarie Island and we have also tested its feasibility at Marion and Campbell Islands. This proposal is for funding to support further work on Campbell and Marion Islands, and in the Cape Horn archipelago. To interpret our data we will carry out a series of General Circulation Model runs to explore the long term changes in SHW strength and the processes driving them, by taking advantage of the new Paleoclimate Modelling Intercomparison Project 3 (PMIP3) AOGCM (climate model) simulations. These experiments will allow comprehensive model-observation evaluation of the new proxy wind strength reconstructions.Ultimately this work will help provide improved boundary conditions for models which simulate the impact of past changes in wind strength on the upwelling of deep ocean carbon reservoirs, and improve our understanding of the relationship between past changes in global atmospheric CO2 and temperature.

气候变化被归因于我们大气中温室气体（如CO2）浓度的增加。这些测量到的大气CO2的增加部分是由世界海洋在表面吸收CO2的能力的变化所控制的（例如通过扩散和生物泵）与深海储层向大气释放旧碳的对比（例如通过上升流和气体排出）。在世界海洋中，南大洋已被确定（通过模型）在调节全球大气CO2中发挥主要作用，特别是在冰川-间冰期时间尺度上。这是因为表面营养物质很高，表明它们没有被生物泵充分利用，而且风驱动的海洋环流变化可以将储存在深海水库中的旧碳带到表面。南半球西风（SHW）强度的变化影响着南大洋环流，并控制着有多少富含碳的深水到达海洋表面。因此，SHW的强度或位置的任何变化，如最近观察到的风力增强，都可能影响南大洋是否作为大气CO2的净源或汇。目前，我们对SHW过去变化的理解主要基于南美洲的地质代用记录，一个记录来自南非，两个来自新西兰。除坎贝尔岛外，没有对南大洋SHW的变化进行研究，而南大洋是SHW风带的核心所在。Stager等人（2012年）认为这种空间分辨率的缺乏是我们对过去气候的理解的主要限制。因此，尽管目前的大气环流模式使用了各种过程（生物学、海洋化学和海洋物理学），但它们要么无法产生过去大气CO2变化的幅度，要么与地质场数据不一致。在这里，我们建议通过在南大洋的三个主要部门中的每一个产生代理记录，重点放在位于SHW核心带的亚南极岛屿，大大提高地质数据的空间分辨率。我们采用了一种新的硅藻代理独立控制的一系列标准的沉积学和地球化学代理过去的风力强度。新的代理是基于海上喷雾通过风直接转移到岛屿上，以及它对西海岸湖泊和池塘盐度的影响。这种方法适用于亚南极岛屿，那里整个岛屿的水体有明显的东西向电导率梯度。这种电导率梯度决定了湖泊中存在哪些硅藻群落。一旦这种硅藻-电导率关系定量建立，沉积在放射性碳年代测定的沉积物岩心中的亚化石硅藻群落可用于重建电导率随时间的变化，从而重建过去的相对风强度。我们已经证明，这种方法适用于麦考瑞岛，我们还测试了它在马里恩和坎贝尔群岛的可行性。该提案旨在提供资金，支持在坎贝尔和马里恩群岛以及合恩角群岛开展进一步工作。为了解释我们的数据，我们将利用新的古气候模拟相互比较项目3（PMIP 3）AOGCM（气候模式）模拟，进行一系列的大气环流模式运行，以探索SHW强度的长期变化及其驱动过程。这些实验将允许对新的代理风强度重建进行全面的模型观测评估，最终这项工作将有助于为模拟过去风强度变化对深海碳库上涌的影响的模型提供改进的边界条件，并提高我们对全球大气CO2和温度过去变化之间关系的理解。

项目成果

The Spatial Structure of the 128 ka Antarctic Sea Ice Minimum

128 ka南极海冰最小值的空间结构

• DOI: 10.1002/2017gl074594
• 发表时间: 2017
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Holloway M

On the identity of Navicula gottlandica (Bacillariophyta), with the description of two new species Navicula eileencoxiana and Navicula bergstromiana from the Australo-Pacific region

关于 Navicula Gottlandica（硅藻门）的身份，以及来自澳大利亚-太平洋地区的两个新种 Navicula eileencoxiana 和 Navicula bergstromiana 的描述

• DOI: 10.5091/plecevo.2019.1607
• 发表时间: 2019
• 期刊: Plant Ecology and Evolution
• 影响因子: 1.1
• 作者: Sabbe K

Late Glacial and Holocene Palaeolake History of the Última Esperanza Region of Southern Patagonia

南巴塔哥尼亚 Áltima Esperanza 地区的晚冰期和全新世古湖历史

• DOI: 10.3389/feart.2022.813396
• 发表时间: 2022
• 期刊: Frontiers in Earth Science
• 影响因子: 2.9
• 作者: Roberts S

Late glacial-Holocene record of Southern Hemisphere westerly wind dynamics from the Falkland Islands, South Atlantic Ocean

南大西洋福克兰群岛南半球西风动力学的晚冰期-全新世记录

• DOI: 10.1130/g49805.1
• 发表时间: 2022
• 期刊: Geology
• 影响因子: 5.8
• 作者: Monteath A

Extinction of austral diatoms in response to large-scale climate dynamics in Antarctica.

• DOI: 10.1126/sciadv.abh3233
• 发表时间: 2021-09-17
• 期刊: Science advances
• 影响因子: 13.6
• 作者: Pinseel E;Van de Vijver B;Wolfe AP;Harper M;Antoniades D;Ashworth AC;Ector L;Lewis AR;Perren B;Hodgson DA;Sabbe K;Verleyen E;Vyverman W
• 通讯作者: Vyverman W