Assessing the role of ocean circulation in rapid climate change through the novel integration of high-resolution proxy records

海洋环流在冰川-间冰期周期和千年时间尺度上发生的全球气候变化中的作用一直是深入研究的主题。海洋环流重新分配地球表面的热量，因此有可能放大气候变化。此外，深海是最大的二氧化碳储存库，因此在控制大气二氧化碳浓度的冰川-间冰期变化方面发挥着重要作用。因此，环流体系之间的迅速转变被认为是引发气候变化的一种可能机制，包括大气二氧化碳浓度和海平面的冰川-间冰期转变，并可能放大其他过程引发的气候变化。海洋代用指标是我们在气候变化期间对过去海洋状况的唯一限制。大多数海洋代用指标通常用于追踪海洋中的一个变量，通常是水团的位置和混合，但受到一些气候调制过程的影响。大多数已发表的海洋环流记录都是基于对海洋沉积物中生物化的深居原生动物的碳同位素组成的测量。然而，这些生物的碳同位素组成不仅受到循环变化的影响，还受到其他几个过程的影响，包括深海有机物的呼吸作用。海洋环流在推动冰川-间冰期气候变化和千年尺度气候变率方面的作用仍然存在争议，因为没有足够的信息来解决环流变化是否发生在深海碳化学和气候变化的同时，之前或之后。我们正在提议开发新的记录，使我们能够确定过去二十万年中的“事件序列”，即最后两次冰期-间冰期循环。事实证明，海洋沉积物中铁锰氧化物矿物的钕同位素组成可以直接用于重建海洋环流。新同位素对与碳同位素相同的过程不敏感。我们还将比较对相同海洋沉积物样品的钕和碳同位素测量，以确定碳同位素记录的非海洋环流成分。然后，我们将把它与一组营养替代物进行比较，这些营养替代物是化石化的深居有孔虫的微量金属成分，以便将再生成分与影响碳同位素的其他过程分开。这种方法将使我们能够研究海洋气候系统的两个不同部分之间的相位关系，物理控制和生物控制，在这些气候变化期间。

The role of ocean circulation during global climate changes that occur during glacial-interglacial cycles and on millenial timescales has been the subject of intense research. Ocean circulation redistributes heat on the earth's surface and therefore has the potential to amplify climate change. Furthermore, the deep ocean is the largest reservoir of carbon dioxide and therefore has an important role in glacial-interglacial changes controlling in atmospheric carbon dioxide concentration. As such, rapid shifts between circulation regimes have been suggested as a possible mechanism to trigger climate change, including glacial-interglacial transitions in atmospheric carbon dioxide concentrations and sea level, and as a possible amplifier of climate changes that were started by other processes. Marine proxies provide our only constraints on past ocean conditions during periods of climate change. Most marine proxies are generally used to trace one variable in the ocean, typically watermass location and mixing, but are affected by a number of climate-modulated processes. Most published records of ocean circulation are based on measurements of the carbon isotope composition of fossilized deep-dwelling protozoa that occur in ocean sediments. However, the carbon isotope composition of these creatures is not just affected by changes in circulation, but also by several other processes including respiration of organic matter in the deep ocean. The role of ocean circulation in driving glacial-interglacial climate change and millenial-scale climate variability is still debated because there isn't enough information to address if circulation changs occurred at the same time, before, or after changes in deep ocean carbon chemistry and climate. We are proposing to develop new records that will let us determine the 'sequence of events' during the last two hundred thousand years, the last two glacial-interglacial cycles. As it turns out, the neodymium isotope composition of iron-manganese oxide minerals in marine sediments can be used to directly reconstruct ocean circulation. Neodymium isotopes are not sensitive to the same process as carbon isotopes. We are also going to compare neodymium and carbon isotope measurements on the same marine sediment samples to determine the non-ocean circulation component of the carbon isotope record. We are then going to compare this with a set of nutrient proxies, the trace metal composition of fossilized deep-dwelling foraminifera, in order to separate the regeneration component from the other processes that affect carbon isotopes. This approach will allow us to study the phasing relationships between two different parts of the ocean-climate system, the physically controlled, and the biologically controlled, during these periods of climate change.