UKIODP Moratorium Award - IODP Expedition 361, Southern African Climates - Ian Hall

UKIODP 暂停奖 - IODP 361 探险队，南部非洲气候 - Ian Hall

• 批准号: NE/P000037/1
• 负责人: Ian Hall
• 金额: $ 7.4万
• 依托单位: CARDIFF UNIVERSITY
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2016
• 资助国家: 英国
• 起止时间: 2016 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FP000037%2F1
• 关键词: UKIODP; Moratorium; Award; IODP; Expedition

The South African Climates (SAFARI) Expedition 361 will investigate the interaction between climate and the Agulhas Current during the Pliocene/Pleistocene. Six drill sites in the southern Indian Ocean and Mozambique Channel will determine (1) the sensitivity of the Agulhas Current, (2) the dynamics of Indian-Atlantic gateway circulation, and (3) the connection between Agulhas Leakage and shifts of the Atlantic Meridional Overturning Circulation (AMOC) during major ocean and climate reorganizations of the past 5 Ma. The Agulhas Current is the strongest western boundary current in the Southern Hemisphere, transporting some 70 Sv of warm and saline surface waters from the tropical Indian Ocean along the East African margin to the tip of Africa. Exchanges of heat and moisture with the atmosphere influence southern African climates, including individual weather systems such as extratropical cyclone formation in the region and rain-fall patterns. Recent ocean models and paleoceanographic data further point at a potential role of the Agulhas Current in controlling the strength and mode of the AMOC during the Late Pleistocene. Spillage of saline Agulhas water into the South Atlantic stimulates buoyancy anomalies that act as a control mechanism on the basin-wide AMOC, with implications for convective activity in the North Atlantic and Northern Hemisphere climate. Expedition 361 aims to extend this work to periods of major ocean and climate restructuring during the Pliocene/Pleistocene to assess the role that the Agulhas Current and ensuing (interocean) marine heat and salt transports have played in shaping the regional- and global-scale ocean and climate development.Within this moratorium proposal a specific focus will be on the The Middle Pleistocene Transition (MPT), circa 1250 and 700 thousand years (kyr) before present (BP) which represents a key interval of Pleistocene climate history. During this time the periodicity of glacial-interglacial cycles altered from a 40 kyr rhythm to a less frequent, more intense and asymmetric 100 kyr pattern. This shift occurred in the absence of significant changes in orbital forcing, suggesting that internal feedbacks in the climate system played a considerable role in bringing about this major climatic reorganisation. Most hypotheses for the origin of the MPT invoke a response to a long-term cooling, driven by decreasing atmospheric pCO2. Ice core records extending over the past 800 kyr indicate glacial-interglacial pCO2 fluctuations of ~100 ppm. Various mechanisms of carbon sequestration and deep ocean storage have been proposed over the past three decades. One of these mechanisms invokes an increase in the efficiency of preformed nutrients utilisation in the Subantarctic Zone of Southern Ocean as a result of increased dust flux. Glacial dust fertilisation in the iron-limited conditions of this High Nutrient, Low Chlorophyl (HNLC) region, could have driven an increase in primary productivity and increased export of carbon from the surface ocean. Given the potential of this mechanism as a driver of Late Pleistocene pCO2 variability, it is conceivable that a similar process may have operated across the MPT. I will use use material from Exp 361 Site on the Agulhas Plateau to reconstruct export production in the Subantarctic Zone across the MPT. This will allow me to investigate the response of the soft-tissue biological pump to the increased iron deposition observed during the onset of the MPT and will ultimately contribute to our understanding of the processes that resulted in lower glacial pCO2 in the post-MPT world.

南非气候（Safari）探险361将调查在上新世/更新世期间气候与阿古尔哈斯电流之间的相互作用。印度洋南部和莫桑比克频道的六个钻机将确定（1）Agulhas电流的敏感性，（2）印度 - 大西洋网关循环的动力学，以及（3）在大海洋和气候重新进行过去的5 MA的大海洋和气候重新进行期间，Agulhas泄漏与大西洋子午倾倒循环（AMOC）的转移之间的联系。 Agulhas电流是南半球最强的西部边界电流，从东非的热带印度洋沿着东非边缘到非洲的尖端，将约70平方公里的温暖和盐水地表水运送到了。与大气的热和水分交换会影响南部非洲气候，包括该地区的个体天气系统，例如该地区的室外气旋形成和雨水倾斜模式。最近的海洋模型和古复活数据进一步指出了阿古尔哈斯电流在更新世晚期在控制AMOC的强度和模式中的潜在作用。将盐水的水溢出到南大西洋刺激浮力异常，该异常充当盆地范围内AMOC的控制机制，对北大西洋和北半球气候的对流活动的影响。 Expedition 361旨在将这项工作扩展到上新世/更新世期间的主要海洋和气候重组时期，以评估Agulhas当前和随之而来的（Interocean）海洋热和盐运输在塑造区域和全球规模的海洋和气候发展方面发挥的作用。在现在（BP）之前（KYR），代表更新世气候历史的关键间隔。在此期间，冰川间冰期循环的周期性从40 kyr节奏变为频繁，更激烈和不对称的100 kyr模式。这种转变发生在没有轨道强迫发生重大变化的情况下，这表明气候系统中的内部反馈在实现这一重大气候重组方面发挥了相当大的作用。 MPT起源的大多数假设都引起了对长期冷却的反应，这是由于大气PCO2降低而驱动的。在过去的800 kyr中延伸的冰核记录表明冰川冰上的PCO2波动〜100 ppm。在过去的三十年中，已经提出了各种碳封存和深海存储的机制。这些机制之一激发了由于粉尘通量增加而导致的南大洋北海北极地区预先形成的养分效率提高。在这种高营养素，低氯基（HNLC）区域的铁限制条件下，冰川粉尘受精可能会驱动一级生产率的提高，并增加了从地表海洋中的碳出口。鉴于该机制是后期更新世PCO2变异性的驱动因素的潜力，可以想象可以在整个MPT上进行类似的过程。我将使用Agulhas高原上EXP 361站点的材料来重建整个MPT的亚北极区的出口产生。这将使我能够研究软组织生物泵对MPT发作期间观察到的铁沉积增加的反应，并最终将有助于我们理解导致MPPT世界中冰川PCO2较低的过程。

项目成果

Sedimentary DNA reveals the link between microbial community dynamics and climate during the late last glaciation in the offshore region of the Zambezi River, Southwest Indian Ocean.

沉积 DNA 揭示了西南印度洋赞比西河近海地区末次冰期末期微生物群落动态与气候之间的联系。

• DOI: 10.1016/j.scitotenv.2023.167787
• 发表时间: 2024
• 期刊: The Science of the total environment
• 作者: Li H

Orbital Forcing and Evolution of the Southern African Monsoon From Late Miocene to Early Pliocene

• DOI: 10.1029/2022pa004588
• 发表时间: 2023-08
• 期刊: Paleoceanography and Paleoclimatology
• 影响因子: 3.5
• 作者: Allana Queiroz de Azevedo;F. Jiménez‐Espejo;F. Bulian;F. Sierro;D. Tangunan;Y. Takashimizu;A. Albuquerque;K. Kubota;C. Escutia;R. Norris;S. Hemming;I. Hall

A New Seismic Stratigraphy in the Indian-Atlantic Ocean Gateway Resembles Major Paleo-Oceanographic Changes of the Last 7 Ma

印度-大西洋门户的新地震地层类似于过去 7 Ma 的主要古海洋变化

• DOI: 10.1029/2018gc007668
• 发表时间: 2019
• 期刊: Geochemistry, Geophysics, Geosystems
• 作者: Gruetzner J

Latitudinal Migrations of the Subtropical Front at the Agulhas Plateau Through the Mid‐Pleistocene Transition

• DOI: 10.1029/2020pa004084
• 发表时间: 2021-07
• 期刊: Paleoceanography and Paleoclimatology
• 影响因子: 3.5
• 作者: A. Cartagena-Sierra;M. Berke;R. Robinson;B. Marcks;I. Castañeda;A. Starr;I. Hall;S. Hemming;L. Levay

Little Change in Ice Age Water Mass Structure From Cape Basin Benthic Neodymium and Carbon Isotopes

• DOI: 10.1029/2021pa004281
• 发表时间: 2021-10
• 期刊: Paleoceanography and Paleoclimatology
• 影响因子: 3.5
• 作者: S. Hines;L. Bolge;S. Goldstein;C. Charles;I. Hall;S. Hemming