Quantifying Oceanic Whitecap Energy Dissipation and Bubble-Mediated Air-Sea Fluxes

风不断地将能量从大气转移到全球海洋，帮助产生表面波、洋流和从最陡峭的海浪的顶部直接撕裂的水滴。风和表层海洋的相互作用是一个极其复杂的过程，海洋科学家和工程师仍然需要充分了解这一过程，这仍然是一个活跃的研究领域。也许风吹过海洋表面最根本的后果是产生海浪。我们预测海浪的产生、演化和衰变的能力对于人类与全球海洋互动的方式非常重要。例如，海浪预报经常被用来帮助航运公司计划全球海洋上的货物和人员运输，海洋工程师需要知道大浪发生的频率以及这些海浪将如何与他们建造的海洋结构物相互作用，海洋学家需要预测海浪如何影响天气和气候，休闲水手、游泳者和冲浪者依靠准确的海浪预报来安全地享受我们海岸线周围的海洋。海洋学家特别感兴趣的是风和海浪之间的能量平衡。由于风是海浪的主要能源，因此必须有一种机制来消散这种能量输入，否则海浪会继续增长。部分能量耗散发生在我们的海岸线上，在那里，进入的海浪进入浅水时会破裂，释放出能量。这种能量的释放有助于将空气卷进水中，移动沉积物和沙子，并创造混乱的湍急水流。然而，绝大多数的海浪能量都被在公海上破碎的海浪所耗散。在刮风的日子里，它们很容易被发现，因为它们会产生气泡和白色泡沫，通常被称为白色泡沫。这些白浪对地球气候演变的重要性是海洋学家、大气科学家和气候学家非常感兴趣的一个领域。在每个白色冰盖内有数千个气泡，大小从人头发的宽度到大约5便士硬币的宽度不等。这些气泡就像大气的微小复制品，可以与周围的水交换气体。这种气泡介导的气体转移机制对于有多少二氧化碳从大气转移到海洋非常重要。当这些气泡上升到水面并破裂时，它可以向大气中发送微小的海雾水滴，就像你从侧面看到的一杯苏打水的泡沫一样。当这些微小的水滴在大气中时，它们可以帮助在海洋上形成云，将细菌从海洋表面输送到大气中，并可以散射来自太阳的光。更好地了解这些气泡和海洋水滴对地球气候的影响程度，对于准确预测未来地球气候非常重要。为了解决这些难题，我们的研究将使用最先进的造波设备在帝国理工学院的实验室复制破裂的海浪，并将拍摄亚得里亚海的白浪，在那里我们可以使用由意大利海洋科学研究所运营的独特的海洋观测平台。我们将使用波高计、数码相机和立体视觉图像处理技术相结合的方法来测量波浪能量，拍摄破碎的海浪泡沫，并计数和测量破碎海浪产生的气泡的数量和大小。这些数据将被用来改进海洋波浪的计算机模型，以及用于地球气候计算机模型的大气和海洋之间气体交换的预测。

The winds constantly transfer energy from the atmosphere to the global oceans and seas helping to generate surface waves, currents and tearing water droplets directly from the crests of the steepest waves. The interaction of the wind and the surface ocean is an extremely complex process that still remains to be fully understood by ocean scientists and engineers and remains an active area of research. Perhaps the most fundamental consequence of wind blowing over the surface of the oceans is the generation of waves. Our ability to forecast the generation, evolution, and decay of ocean waves is important for the way humans interact with the global oceans. For example, wave forecasts are routinely used to help shipping companies plan the transport of goods and people across the global oceans, marine engineers need to know how often large waves occur and how these waves will interact with the structures they build for use in the ocean, oceanographers need to predict the how ocean waves affect weather and climate, and recreational sailors, swimmers and surfers rely on accurate wave forecasts to safely enjoy the seas and oceans around our coastline.Of particular interest to oceanographers is the energy balance between the wind and the waves. Since the wind acts as the primary source of energy for the waves, there must be a mechanism for dissipating this energy input, otherwise the waves would continue to grow. Part of this energy dissipation occurs along our coastlines where incoming waves break as they enter shallow water, releasing their energy. This release of energy helps to entrain air into the water, to move sediment and sand, and to create chaotic turbulent water motions. However, the vast majority of wave energy is dissipated by waves breaking in the open ocean. These are easy to spot on a windy day because of the bubbles and white foam they produce, commonly called whitecaps. The importance of these whitecaps to how the Earth's climate evolves is an area of huge interest to oceanographers, atmospheric scientists and climate scientists. Within each whitecap there are thousands of bubbles ranging in size from the width of a human hair to about the width of a 5 pence piece. These bubbles are like tiny replicas of the atmosphere that exchange gas with the surrounding water. This bubble-mediated mechanism of gas transfer is very important to how much carbon dioxide is transferred from the atmosphere to the ocean. When each of these bubbles rises to the water surface and bursts it can send tiny sea spray droplets into the atmosphere, much like the fizz of a glass of soda drink that you see when you look at it from the side. When these tiny droplets are in the atmosphere they can help to form clouds over the ocean, transport bacteria from the ocean surface into the atmosphere and can scatter light from the sun. Gaining a better understanding of how much these bubbles and sea spray droplets matter to the Earth's climate is important to make accurate future projections of the Earth's climate.To tackle these difficult questions, our research will use state of the art wave making facilities to replicate breaking ocean waves in the laboratory at Imperial College, and will photograph whitecaps in the Adriatic Sea where we have access to a unique ocean observing platform that is operated by the Italian Institute of Marine Science. We will use a combination of wave height gauges, digital cameras and stereovision image processing techniques, to measure wave energy, photograph the breaking wave foam, and count the number and measure the size of bubbles generated by the breaking waves. These data will be used to improve computer models of ocean waves, and predictions of the exchange of gas between the atmosphere and the oceans for use in computer models of Earth's climate.