Reconstructing millennial-scale variability in deep-water circulation of the North Atlantic during the early Pleistocene

重建早更新世期间北大西洋深水环流的千年尺度变化

• 批准号: NE/G015260/1
• 负责人: Ian Hall
• 金额: $ 3.25万
• 依托单位: CARDIFF UNIVERSITY
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2009
• 资助国家: 英国
• 起止时间: 2009 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FG015260%2F1
• 关键词: Reconstructing; millennial; scale; variability; deep

Summary: The observation of repeated, large and abrupt climatic shifts during the last glacial and deglacial periods has raised current concern over the possibility of abrupt climate change in the future. Yet there is still considerable uncertainty concerning the mechanisms of such changes in the past, even to the extent that we do not fully understand how their effects are transmitted throughout the climate system. Records from Greenland ice cores and North Atlantic sediments suggest that high latitudes in the Northern Hemisphere were repeatedly subjected to very large and abrupt fluctuations in temperature during the last glaciation, commonly referred to as Dansgaard-Oeschger (D-O) oscillations. A single D-O oscillation comprised an abrupt warming event (typically >10 degrees C rise in mean annual temperature over Greenland) within just a few decades, followed by a few centuries of more gradual cooling before an abrupt return to cold conditions. These transitions have been linked to variations in the strength of the deep ocean circulation, which may have affected marine heat transports to the North Atlantic and Nordic Seas. It is increasingly recognised that to understand the processes of abrupt climate change it is necessary to document the variability of the climate system during a wide range of different boundary conditions (e.g. insolation, global ice volume, atmospheric CO2 levels). Here we propose to use marine sediment cores from the sup-polar North Atlantic obtained during Ocean Drilling Programme Leg 164, Site 982, to examine the nature of millennial-scale variability in deep ocean flow speeds of Iceland Scotland Overflow Water (a precursor of North Atlantic Deep Water, the watermass responsible for initiating the global thermohaline circulation) in response to the changing orbital and sub-orbital climate regimes immediately prior to, and across the so called 'mid-Pleistocene climate transition' (MPT; ~1.2-0.7 million years ago). During this transition the dominant influence of orbital forcing changed from obliquity forcing (41,000 years) to eccentricity (100,000 years) modulated precession (23,000 years) thereafter. The palaeocurrrent data generated within this project will be integrated with existing high-resolution records of deep ocean ventilation (based on benthic carbon isotopes) and surface ocean variability (ice rafted debris, stable isotopes) to establish a detailed view of the relationships among these important climate components and further our understanding of how their millennial-scale variability evolved through changing boundary conditions of the mid-Pleistocene. Such palaeo-observations are important for providing input to climate models and evaluating numerical simulations of climate and ice-sheet behaviours.

摘要：在最后一次冰川和冰期期间，观察到重复，大而突然的气候变化，引起了人们对未来突然气候变化可能性的关注。然而，关于过去这种变化的机制仍然存在很大的不确定性，即使我们没有完全了解它们在整个气候系统中如何传播它们的效果。格陵兰冰核心和北大西洋沉积物的记录表明，在最后一次冰川期间，北半球的高纬度反复在温度下发生很大且突然的波动，通常称为Dansgaard-Oeschger（D-O）振荡。单个D-O振荡包括在短短几十年内突然的变暖事件（通常> 10度C的平均年温度升高10度），随后几个世纪的逐渐冷却，然后突然恢复到寒冷的状况。这些过渡与深海循环强度的变化有关，这可能影响了海洋热量传输到北大西洋和北欧海洋。人们越来越认识到，要了解突然的气候变化过程，有必要记录在广泛的不同边界条件下气候系统的变异性（例如，减肥，全球冰量，大气二氧化碳水平）。在这里，我们建议使用在海洋钻井计划中获得的北大西洋的海洋沉积物岩心，地点982，检查冰岛苏格兰溢流水的深海流速千年尺度可变性的性质到所谓的“中渐缩气候过渡”（MPT; 〜1.2-070万年前）。在此过渡期间，轨道强迫的主要影响从倾斜强迫（41，000年）变为偏心率（100,000年）调节的进动（23，000年）。该项目中生成的古汇体数据将与现有的深海通风（基于底栖碳同位素）和表面海洋变异性（冰筏碎屑，稳定的同位素）的现有高分辨率记录集成在一起，以详细的看法，以对这些重要的气候成分之间的关​​系建立对这些重要的气候成分之间的关​​系，并进一步了解我们对千年可变性的环境的理解。此类古观察对于为气候模型提供输入并评估气候和冰淇淋行为的数值模拟很重要。

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