Convection and Cascading on Arctic Shelves: a tracer study

如果海洋环流减速或停止，会发生什么？可以肯定的是，西欧将出现严重的、可能是灾难性的经济和环境崩溃。维持海洋循环需要什么？循环需要水在赤道附近混合，并在两极附近下沉。下沉的水必须足够稠密，才能重新供应最终向南流向赤道的深水。因此，高密度水的形成是维持西欧海洋环流和气候稳定的基本要求。极地地区的致密水形成地点主要是深水的开阔海域，或浅水的陆架地点。陆架高密度水生产的贡献是深水整体供应的重要组成部分。在北极冬季，生长在海面上的冰释放出寒冷的咸水。稠密的卤水下沉并开始在货架上积累，然后流向货架边缘。在这里，它以瀑布的形式从陡峭的陆架斜坡上俯冲下来，开始与北冰洋的水混合。最终，稠密的大陆架水进入深水，以维持海洋的循环。今天，我们仍然不确定控制卤水密度的物理参数，以及瀑布的混合如何决定稠密水对深部的贡献。这项提议将与挪威研究人员联合起来，研究斯皮茨卑尔根两个交通便利地点的稠水形成和瀑布。我们将使用系泊仪器监测大陆架上稠密水池的温度和盐度的变化，然后随着这些水从陆架斜坡上倾泻而下。为了了解冰的生长和混合如何影响水的性质，我们将使用水分子中的氧原子作为化学标记或示踪剂。通过对示踪剂的仔细测量，我们将能够确定致密水的配方，这种变化在级联过程中是如何变化的，以及致密陆架水对深海的贡献。然后，我们将在深水形成的计算机模型中使用这些结果，以确保我们能够准确预测气候变化，特别是海冰增长的变化，可能会如何影响海洋循环。

What would happen if ocean circulation slowed or stopped? It is certain that in western Europe there would be substantial and potentially catastrophic economic and environmental collapse. What is required to maintain ocean circulation? Circulation requires water to be mixed near the equator and to sink near the poles. The water that sinks must be dense enough to re-supply the deep waters which eventually flow south, back toward the equator. Dense water formation is therefore an essential requirement for maintaining ocean circulation and climatic stability in western Europe. Locations of dense water formation in the polar regions are primarily open ocean sites in deep water, or shelf sites in shallow water. The contribution of dense water production on shelves is an important component in the overall supply of deep water. During the Arctic winter, cold, salty brine is released from ice growing at the sea surface. The dense brine sinks and begins to accumulate on the shelf before flowing towards the shelf edge. Here it plunges down the steep shelf slope as a cascade where it begins to mix with the waters of the Arctic seas. Eventually, the dense shelf water becomes incorporated into the deep waters to maintain the circulation of the oceans. Today, we are still unsure of the physical parameters that control the brine density and how mixing of the cascade determines how much the dense water contributes to the deep. This proposal will unite with Norwegian researchers to study dense water formation and cascading at two easily accessible sites in Spitsbergen. We will use moored instruments to monitor the change in temperature and salinity of the dense water pool on the shelf and then follow this water as it cascades down the shelf slope. To understand how ice growth and mixing affect the properties of the water we will use the oxygen atom in a water molecule as a chemical marker or tracer. Through careful measurement of the tracer we will be able to determine the recipe of the dense water, how this changes during the cascade and the contribution that the dense shelf water is making to the deep. We will then use these results in computer models of deep water formation to ensure that we can make accurate predictions of how climate change, and particularly changes in sea ice growth, may affect ocean circulation.