Convection and Cascading on Arctic Shelves: a tracer study

如果海洋环流减缓或停止会发生什么？可以肯定的是，西欧的经济和环境将出现严重的、潜在的灾难性崩溃。维持海洋环流需要什么？环流需要水在赤道附近混合，在两极附近下沉。下沉的水必须足够稠密，以重新补给最终向南流回赤道的深水。因此，致密水的形成是维持西欧海洋环流和气候稳定的必要条件。极地地区致密水形成的地点主要是深水中的开阔海洋地点或浅水中的陆架地点。陆架上致密产水的贡献是深水总供给的重要组成部分。在北极的冬季，海面上生长的冰释放出寒冷的咸水。浓盐水下沉并开始在陆架上积聚，然后流向陆架边缘。在这里，它像瀑布一样沿着陡峭的陆架斜坡倾泻而下，开始与北极海域的水混合。最终，密集的陆架水被并入深水中，以维持海洋的循环。今天，我们仍然不确定控制盐水密度的物理参数，以及级联的混合如何决定高密度水对深海的贡献。该提案将与挪威的研究人员联合起来，在斯匹次卑尔根岛两个容易到达的地点研究致密水的形成和瀑布。我们将使用系泊仪器监测大陆架上密集水池的温度和盐度变化，然后跟踪这些水沿着大陆架斜坡倾泻而下的过程。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，我们将能够确定稠密水的配方，它在级联过程中是如何变化的，以及稠密的陆架水对深海的贡献。然后，我们将把这些结果用于深水形成的计算机模型，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，如何影响海洋环流。

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.