A direct link between ocean circulation and abrupt climate change?

海洋环流与气候突变之间有直接联系吗？

• 批准号: NE/I006370/1
• 负责人: Stephen Barker
• 金额: $ 6.54万
• 依托单位: CARDIFF UNIVERSITY
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2011
• 资助国家: 英国
• 起止时间: 2011 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FI006370%2F1
• 关键词: direct; link; between; ocean; circulation

Summary The surprising possibility that climate may change by as much as 10 degrees C within just 10-20 years was discovered through examining ice-cores drilled into the Greenland ice sheet. The enormous impact that similar future changes could have on the world's society motivates efforts to understand the possible causes of abrupt climate change and the likelihood of future occurrences. Abrupt oscillations in climate, termed Dansgaard-Oeschger (D-O) events, occurred frequently during an interval 30 - 60 thousand years ago (ka). Reorganisations of the ocean circulation in the Atlantic (the so-called Atlantic meridional overturning circulation, AMOC) have been invoked to play a dominant role in governing the abrupt nature of D-O events. The AMOC is characterised by warm salty surface water flowing northwards to the northern North Atlantic, where it cools and sinks, forming North Atlantic deepwater (NADW) that flows southwards as a deep return flow. It is the movement of warm water to the high latitudes and the subsequent release of heat to the atmosphere that helps regulates the climate of the North Atlantic. Changes in the AMOC have been related to climate shifts in modelling studies. Yet despite intensive study, we still lack unequivocal physical evidence for a systematic and direct role of deep ocean circulation in abrupt climate change. Here we propose to examine ocean sediments at very high temporal resolution in order to test the involvement of deep circulation changes during past abrupt climate change. The flow of NADW (the deep water limb of the AMOC) forms an intense current at depth along the eastern continental margin of North America. We aim to reconstruct changes in the strength of this current by assessing changes in the grain size of seafloor sediments: very simply, faster current flow causes sorting of the sediment and leads to larger average grain size. Previous studies have suggested that cold intervals are related to reduced deep water formation in the northern North Atlantic and a shoaling of NADW. We will test this hypothesis by detecting intervals of stronger shallow flow using sediment cores at 1.8 km and 3 km depth. Previous work has demonstrated that our chosen core sites and sampling intervals will produce records with a resolution of ~100 years and will therefore be capable of reconstructing the multi-centennial scale D-O oscillations. Pilot study data that we have obtained from an earlier time interval provide confidence in our chosen methods and have yielded very promising results, suggesting a tight coupling between ocean circulation changes and climate. This study addresses a clearly identified gap in our understanding of abrupt climate change. Testing the hypothesis that abrupt climate change is directly related to changes in ocean circulation, and further investigating the differences between different cold events, will represent an important advance in the field of paleoclimatology. The results of this study will be of direct benefit to, for example, climate modellers, and hence will be of importance in enhancing our predictive knowledge of future abrupt climate change. Our study will address directly NERC's current challenge to 'Quantify forces and feedbacks that drive the Earth System' within its Earth System Science Theme, and specifically Challenges 8 and 11 ('Ocean processes and their interaction with the Earth System' and 'What do records of past environments reveal about the operation of the Earth System?).

通过检查钻入格陵兰冰盖的冰芯，发现了在短短10-20年内气候可能变化高达10摄氏度的惊人可能性。类似的未来变化可能对世界社会产生的巨大影响促使人们努力了解气候突变的可能原因和未来发生的可能性。气候突变事件，称为Dansgaard-Oeschger（D-O）事件，频繁发生在3 - 6万年前（ka）。大西洋海洋环流的重组（所谓的大西洋纬向翻转环流，AMOC）已被援引发挥主导作用，在管理D-O事件的突然性质。AMOC的特点是温暖的咸表面水向北流到北大西洋北方，在那里冷却和下沉，形成北大西洋深水（NADW），作为深回流向南流动。正是温暖的海水向高纬度地区的移动以及随后向大气中释放的热量帮助调节了北大西洋的气候。AMOC的变化与模拟研究中的气候变化有关。然而，尽管进行了深入的研究，我们仍然缺乏明确的物理证据来证明深海环流在气候突变中的系统和直接作用。在这里，我们建议在非常高的时间分辨率检查海洋沉积物，以测试在过去的气候突变的深环流变化的参与。NADW（AMOC的深水边缘）的流动在沿着北美东部大陆边缘的深度形成了一个强烈的电流。我们的目标是通过评估海底沉积物粒度的变化来重建这种电流强度的变化：很简单，更快的电流流动导致沉积物的分选，并导致更大的平均粒度。以前的研究表明，冷间隔与北大西洋北方深水形成减少和NADW变浅有关。我们将通过使用1.8公里和3公里深的沉积物岩心探测较强的浅水流间隔来检验这一假设。以前的工作已经表明，我们选择的核心网站和采样间隔将产生记录的分辨率约为100年，因此将能够重建多百年尺度的D-O振荡。我们从较早的时间间隔获得的试点研究数据为我们选择的方法提供了信心，并产生了非常有希望的结果，表明海洋环流变化和气候之间存在紧密的耦合。这项研究解决了我们对突然气候变化的理解中明确确定的差距。检验气候突变与海洋环流变化直接相关的假设，并进一步研究不同冷事件之间的差异，将代表古气候学领域的一个重要进展。这项研究的结果将直接有益于，例如，气候模拟，因此将是重要的，在提高我们的预测知识的未来气候突变。我们的研究将直接解决NERC当前的挑战，即在其地球系统科学主题中“量化驱动地球系统的力量和反馈”，特别是挑战8和11（“海洋过程及其与地球系统的相互作用”和“过去环境的记录揭示了地球系统的运作？”）。

项目成果

Abrupt changes in deep Atlantic circulation during the transition to full glacial conditions

• DOI: 10.1002/palo.20025
• 发表时间: 2013-06
• 期刊: Paleoceanography
• 作者: D. Thornalley;S. Barker;Julia Becker;I. Hall;G. Knorr

Early Interglacial Legacy of Deglacial Climate Instability

• DOI: 10.1029/2019pa003661
• 发表时间: 2019-08-01
• 期刊: PALEOCEANOGRAPHY AND PALEOCLIMATOLOGY
• 影响因子: 3.5
• 作者: Barker, Stephen;Knorr, Gregor;Thornalley, David
• 通讯作者: Thornalley, David