Bridging the timing gap: connecting Southern Ocean and Antarctic Climate records

缩小时间差距：连接南大洋和南极气候记录

• 批准号: NE/N003861/1
• 负责人: Laura Robinson
• 金额: $ 52.85万
• 依托单位: University of Bristol
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2015
• 资助国家: 英国
• 起止时间: 2015 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FN003861%2F1
• 关键词: Bridging; timing; gap; connecting; Southern

In light of current concerns over greenhouse-gas emissions and related temperature rise it is important to understand the mechanisms operating in the global climate system. This understanding may allow us to anticipate human-induced climate change and related ecosystem vulnerability. The Southern Ocean plays a central role in defining Earth's climate because it is a location where cold, deep waters rise to the surface and exchange gases and heat with the atmosphere. One of the most important gases for the climate system is carbon dioxide (CO2). Since the oceans contain about 60 times more carbon than the atmosphere, it only takes a small perturbation in the ocean to have a large climate impact. Atmospheric CO2 levels have shown systematic changes over the past 800,000 years as revealed by gasses trapped in ice cores, and recent evidence has come to light that shows that CO2 can increase rapidly over only hundreds of years. We still do not know how and why these changes in CO2 occur but their size and speed suggests that they must have been driven by changes in the deep ocean.Mechanisms that have been put forward to explain lower atmospheric CO2 concentrations during past cold (glacial) periods focus on increased CO2 uptake in the Southern Ocean. This could have been achieved by a combination of increased sea ice cover and a more layered structure in the water column, which prevents CO2 from escaping to the atmosphere. The concept is supported by modeling evidence and predicts that we should find old, carbon-rich waters in the deep Southern Ocean during past cold times. If this layered water structure was removed, then these deep waters would release CO2 to the atmosphere as ice ages came to a close. Records from ice cores show us that the actual rise of CO2 during the end of the last ice age ('last deglaciation') happened in multiple steps. So far, however, it has been very difficult to obtain records from the Southern Ocean to test the hypothesis posed above, or the alternative hypothesis that carbon sequestration in the South was achieved due to more active CO2 uptake by planktonic marine plants. What we have been lacking is a suitable recorder ('archive') of past environmental conditions directly in the Southern Ocean that can resolve time increments of about 100 years or less, similar to in the record preserved in ice cores.With our project we aim to transform understanding of the Southern Ocean's role in climate change by creating detailed records of the circulation, temperature, and CO2 chemistry of the Southern Ocean at the end of the last ice age and into the current warm period (past 25,000 years) at unprecedented temporal resolution. To achieve this we will make geochemical measurements on the skeletons of fossil deep-sea corals, a novel archive that allows us to create unique coupled records of past oceanographic change on a precise and accurate timescale. The skeletons of deep-sea corals are formed using the chemical ingredients of the seawater that they live in. This means that during the lifetime of a coral (~100 years) a record of water mass composition and temperature is captured as they grow. By performing a suite of geochemical measurements on each fossil coral, we can reconstruct environmental conditions at the time it grew. Repeating this exercise for hundreds of corals will allow us to construct the first directly dated record of the Southern Ocean's behavior since the last ice age. Our new record will allow comparison of the relative timing of environmental changes in the Southern Ocean with those of ice core records. It will therefore address one of the most hotly debated questions in global climate change research, the origin of changes in atmospheric CO2 and temperature on time scales of hundreds to thousands of years.

鉴于当前对温室气体排放和相关气温上升的担忧，了解全球气候系统的运作机制非常重要。这种理解可能使我们能够预测人类引起的气候变化和相关的生态系统脆弱性。南大洋在定义地球气候方面发挥着核心作用，因为它是寒冷的深水上升到地表并与大气交换气体和热量的地方。气候系统最重要的气体之一是二氧化碳 (CO2)。由于海洋中的碳含量大约是大气的 60 倍，因此海洋中的微小扰动就会对气候产生巨大的影响。冰芯中的气体揭示了过去 80 万年中大气中的二氧化碳水平发生了系统性变化，而最近的证据表明，二氧化碳在短短数百年内就能迅速增加。我们仍然不知道二氧化碳的这些变化是如何以及为何发生的，但其规模和速度表明它们一定是由深海的变化驱动的。为解释过去寒冷（冰川）时期大气二氧化碳浓度较低而提出的机制集中于南大洋二氧化碳吸收的增加。这可以通过增加海冰覆盖和水柱中更多的分层结构相结合来实现，这可以防止二氧化碳逃逸到大气中。这一概念得到了模型证据的支持，并预测我们应该在过去的寒冷时期在南大洋深处找到古老的富含碳的水域。如果这种分层的水结构被移除，那么随着冰河时代的结束，这些深水将会向大气中释放二氧化碳。冰芯记录向我们表明，在最后一个冰河时代（“最后一次冰消期”）结束时，二氧化碳的实际上升是分多个步骤发生的。然而，到目前为止，很难从南大洋获得记录来检验上述假设，或者检验南方的碳封存是由于浮游海洋植物更活跃地吸收二氧化碳而实现的另一种假设。我们一直缺乏的是一个合适的直接记录南大洋过去环境条件的记录仪（“档案”），它可以解析大约100年或更短的时间增量，类似于冰芯中保存的记录。通过我们的项目，我们的目标是通过创建南大洋在最后一个冰河时代末期和当前温暖时期（过去25,000年）的环流、温度和二氧化碳化学的详细记录，转变对南大洋在气候变化中的作用的理解。 前所未有的时间分辨率。为了实现这一目标，我们将对深海珊瑚化石的骨骼进行地球化学测量，这是一种新颖的档案，使我们能够在精确和准确的时间尺度上创建过去海洋变化的独特耦合记录。深海珊瑚的骨骼是利用它们所生活的海水的化学成分形成的。这意味着在珊瑚的一生（约 100 年）中，随着它们的生长，会捕获水体成分和温度的记录。通过对每个化石珊瑚进行一系列地球化学测量，我们可以重建其生长时的环境条件。对数百个珊瑚重复这一练习将使我们能够构建自上一个冰河时代以来南大洋行为的第一个直接日期记录。我们的新记录将允许将南大洋环境变化的相对时间与冰芯记录进行比较。因此，它将解决全球气候变化研究中最受争议的问题之一，即数百至数千年时间尺度上大气二氧化碳和温度变化的起源。

项目成果

Rapid shifts in circulation and biogeochemistry of the Southern Ocean during deglacial carbon cycle events.

• DOI: 10.1126/sciadv.abb3807
• 发表时间: 2020-10
• 期刊: Science advances
• 影响因子: 13.6
• 作者: Li T;Robinson LF;Chen T;Wang XT;Burke A;Rae JWB;Pegrum-Haram A;Knowles TDJ;Li G;Chen J;Ng HC;Prokopenko M;Rowland GH;Samperiz A;Stewart JA;Southon J;Spooner PT
• 通讯作者: Spooner PT

Acceleration of Northern Ice Sheet Melt Induces AMOC Slowdown and Northern Cooling in Simulations of the Early Last Deglaciation

• DOI: 10.1029/2017pa003308
• 发表时间: 2018-07
• 期刊: Paleoceanography and Paleoclimatology
• 影响因子: 3.5
• 作者: R. Ivanović;L. Gregoire;Andrea Burke;A. Wickert;Paul J. Valdes;H. C. Ng;Laura F. Robinson;Jerry F. McManus;J. Mitrovica;Lindsay Lee;J. Dentith

Persistently well-ventilated intermediate-depth ocean through the last deglaciation

• DOI: 10.1038/s41561-020-0638-6
• 发表时间: 2020-10-12
• 期刊: NATURE GEOSCIENCE
• 影响因子: 18.3
• 作者: Chen, Tianyu;Robinson, Laura F.;Harpp, Karen S.
• 通讯作者: Harpp, Karen S.

Ba/Ca of stylasterid coral skeletons records dissolved seawater barium concentrations

• DOI: 10.1016/j.chemgeo.2023.121355
• 发表时间: 2023-02-24
• 期刊: CHEMICAL GEOLOGY
• 影响因子: 3.9
• 作者: Kershaw，James;Stewart，Joseph A.;Haussermann，Vreni
• 通讯作者: Haussermann，Vreni

What fraction of the Pacific and Indian oceans' deep water is formed in the Southern Ocean?

太平洋和印度洋深水的哪一部分是在南大洋形成的？

• DOI: 10.5194/bg-15-3779-2018
• 发表时间: 2018
• 期刊: Biogeosciences
• 影响因子: 4.9
• 作者: Rae J