INTRIGUED: INvestigating The Role of the North Pacific In Glacial and Deglacial CO2 and Climate

地质记录为了解地球气候的不同运作方式提供了一扇宝贵的窗口。在现代气候变化之前，最近的大规模地球气候变化是更新世冰川旋回，其特征是大冰盖的生长和解体，主要雨带的快速变化以及海洋环流的突变。根据冰芯中的气泡重建的大气中二氧化碳浓度的变化与这些冰河时期的气候事件密切相关。事实上，在冰期-间冰期的循环中，二氧化碳和温度的紧密耦合已经成为气候科学中的一个标志性图像，是二氧化碳在气候中的重要性的一个典型代表，也是比较当前人为二氧化碳上升的自然模板。然而，尽管冰期-间冰期的二氧化碳变化备受关注，我们仍然没有完全了解其原因。关于冰川二氧化碳变化的主要假设涉及冰河时期海洋对二氧化碳的吸收增加，这些二氧化碳在冰川消融期间被排放到大气中。然而，尽管经过几十年的研究，由于缺乏冰川海洋中二氧化碳储存的数据，这些假设几乎没有得到直接的验证。在我们对冰河时期二氧化碳和气候变化的理解中，最明显的漏洞之一是太平洋的行为。这个盆地包含了全球海洋总量的一半，二氧化碳含量是大气的30倍，因此它的行为将对全球产生影响。最近也有人提出，北太平洋可能在冰期二氧化碳上升中发挥积极作用，当地深水的形成有助于将二氧化碳从深海释放到大气中。如果正确的话，这一假设为地球气候系统提供了一个新的视角，在最近的过去，深水能够在每个高纬度盆地形成，北太平洋可能在冰川消融中发挥关键作用。然而，很少有数据可以验证太平洋在冰川二氧化碳储存中的作用这一长期存在的观点，也很少有数据可以验证最近的假设，即北太平洋深水导致了冰川二氧化碳的快速上升。考虑到太平洋二氧化碳储存库的规模，我们对其行为缺乏了解是全面了解冰期-间冰期二氧化碳变化和冰河时期气候的主要障碍。该提案旨在通过研究北太平洋深处如何在冰期储存二氧化碳，并在冰川消退期间将其释放回大气，来改变我们对冰期二氧化碳和气候变化的理解。我们将对最近从深海沉积物岩心中采集的样品，在微化石壳（记录海水中二氧化碳的行为）和放射性碳（记录深水是如何离开表层海洋的）中使用最先进的硼同位素地球化学测量。通过将这些新记录与其他已发表的数据进行比较，我们将能够区分太平洋深处二氧化碳储存的不同机制，并测试北太平洋深水形成的程度和最后一次冰川消融期间二氧化碳的释放。我们还将改进用于进行硼同位素测量的技术，并为硼同位素与海水CO2化学之间的关系添加新的约束条件，这将有助于其他小组使用该技术研究CO2变化。为了帮助我们更多地了解二氧化碳和海洋环流变化的机制，并与其他相关学科的科学家协同工作，我们将把我们的数据与地球系统模型的结果进行比较，并与营养循环和气候动力学方面的专家合作。我们的项目最终将提高对海洋和大气之间二氧化碳交换的理解，这是预测未来气候变化路径的重要因素。

The geological record offers an invaluable window into the different ways earth's climate can operate. The most recent large-scale changes in earth's climate, prior to modern climate change, were the Pleistocene glacial cycles, which feature growth and disintegration of large ice sheets, rapid shifts in major rain belts, and abrupt changes in ocean circulation. Changes in atmospheric CO2 concentrations, reconstructed from air bubbles in ice cores, are intimately linked with these ice age climate events. Indeed the close coupling of CO2 and temperature over glacial-interglacial cycles has become an iconic image in climate science, a poster child for the importance of CO2 in climate, and the natural template against which to compare current man-made CO2 rise. However despite the high profile of glacial-interglacial CO2 change, we still don't fully understand its cause. The leading hypotheses for glacial CO2 change involve increased CO2 uptake by the ocean during ice ages, which is vented to the atmosphere during deglaciation. However despite decades of work these hypotheses have had few direct tests, due to a lack of data on CO2 storage in the glacial ocean. One of the most glaring holes in our understanding of ice age CO2 and climate change is the behaviour of the Pacific. This basin contains half of global ocean volume, and ~30 times more CO2 than the atmosphere, and so its behaviour will have global impact. It has also recently been suggested that the North Pacific may play an active role in deglacial CO2 rise, with local deep water formation helping to release CO2 from the deep ocean to the atmosphere. If correct, this hypothesis provides a new view of Earth's climate system, with deep water able to form in each high latitude basin in the recent past, and the North Pacific potentially playing a pivotal role in deglaciation. However few data exist to test either the long-standing ideas on the Pacific's role in glacial CO2 storage, nor the more recent hypothesis that North Pacific deep water contributed to rapid deglacial CO2 rise. Given the size of the Pacific CO2 reservoir, our lack of knowledge on its behaviour is a major barrier to a full understanding of glacial-interglacial CO2 change and the climate of the ice ages. This proposal aims to transform our understanding of ice age CO2 and climate change, by investigating how the deep North Pacific stored CO2 during ice ages, and released it back to the atmosphere during deglaciations. We will use cutting-edge geochemical measurements of boron isotopes in microfossil shells (which record the behaviour of CO2 in seawater) and radiocarbon (which records how recently deep waters left the surface ocean), on recently collected samples from deep ocean sediment cores. By comparing these new records to other published data, we will be able to distinguish between different mechanisms of CO2 storage in the deep Pacific, and to test the extent of North Pacific deep water formation and CO2 release during the last deglaciation. We will also improve the techniques used to make boron isotope measurements, and add new constraints on the relationship between boron isotopes and seawater CO2 chemistry, which will help other groups using this technique to study CO2 change. To help us understand more about the mechanisms of changes in CO2 and ocean circulation, and provide synergy with scientists in other related disciplines, we will compare our data to results from earth system models, and collaborate with experts on nutrient cycling and climate dynamics. Our project will ultimately improve understanding of CO2 exchange between the ocean and the atmosphere, which is an important factor for predicting the path of future climate change.