The influence of surfactants on the mechanisms of ocean bubble generation, and the consequences for air-sea gas transfer.

表面活性剂对海洋气泡产生机制的影响以及空气-海洋气体转移的后果。

基本信息

批准号：
NE/H016856/2
负责人：
Helen Czerski
金额：
$ 11.87万
依托单位：
University College London
依托单位国家：
英国
项目类别：
Fellowship
财政年份：
2013
资助国家：
英国
起止时间：
2013 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FH016856%2F2
关键词：
influence surfactants mechanisms ocean bubble

项目摘要

This project will examine how natural ocean substances affect the production of bubbles in the ocean. Bubbles are important for many of the processes that happen in the top few metres of the ocean. They are mostly generated by breaking waves, and although the larger ones rise to the surface very quickly and burst, the smaller bubbles can remain trapped in the ocean for several minutes. Both large and small bubbles are important for the transfer of gas from the atmosphere to the ocean, since they provide lots of surface area where the gas inside the bubble can touch the ocean and may dissolve in it. Breaking waves generate a considerable amount of background noise in the ocean, because every newly-formed bubble emits a pulse of sound. Bubbles can also absorb and redirect sound that comes from other sources, and so knowledge of the bubbles present is important for understanding how sonar pulses and other sound from below the surface bounces off the top of the ocean. As modelling of weather and the effect of high winds and storms improves, an increasing level of detail is needed to understand the physics of the ocean surface properly. We now understand that very small events like bubble production can make a significant difference to larger processes in the ocean like gas absorption, so knowledge of the number and size of bubbles that exist in the ocean is becoming increasingly important. Bubbles underneath breaking waves are formed because of the intense turbulence that exists for the first second or two after wave breaking. This turbulence will distort the bubbles and may break a large bubble into two or more smaller bubbles. These smaller bubbles may fragment in turn, and the process continues until the turbulence is no longer strong enough to break the bubbles up. In addition, bubbles may bump into each other and coalesce, making larger bubbles out of two smaller ones. All these processes determine how many bubbles there are just after a wave breaks and how big they are, and then this fixed population of bubbles rises and dissolves and changes more slowly with time. The distortion of a bubble depends on the strength of the turbulence and the way the bubble surface behaves. The surface tends to reduce the distortion and so prevent the bubble breaking up. Previous research has investigated bubble splitting in clean fresh water and salt water, but natural ocean water contains many other substances, which are generated by the small organisms in the water (for example algae, tiny plants and tiny animals). Many of these substances will stick to bubble surfaces and may change how the bubble surface behaves, including the probability of splitting and rejoining. This fellowship project will look at single bubbles splitting into two bubbles and pairs of bubbles joining together to form one bigger bubble in turbulence, and compare what happens with and without the natural ocean chemicals present. Then, artificial waves will be generated and allowed to break in a wave tank with and without the additional chemicals , so that we can see the changes in the number and size of bubbles that are caused by the chemicals. Finally, the bubbles in real breaking waves at sea will be studied to look for the same effects. The overall results will help us understand how the natural chemistry of the ocean could affect how the ocean and the atmosphere interact. Ocean chemistry can be very different in different regions of the ocean, and this is not currently taken into account in the measurement of natural bubble populations and their effects.

该项目将研究天然海洋物质如何影响海洋气泡的产生。气泡对于在海洋前几米中发生的许多过程都很重要。它们主要是通过断电产生的，尽管较大的波浪非常快地升至表面并破裂，但较小的气泡可能仍将其捕获在海洋中几分钟。大小气泡对于从大气中将气体转移到海洋都很重要，因为它们提供了许多表面积，气泡内部的气体可以触摸海洋并可能溶解在其中。破坏波在海洋中产生了相当多的背景噪声，因为每个新形成的气泡都会发出声音脉冲。气泡还可以吸收其他来源带来的声音，因此对气泡的知识对于了解声纳脉冲和其他声音如何从表面下方反弹出海洋顶部很重要。随着天气的建模以及大风和风暴的影响，需要越来越多的细节才能正确理解海洋表面的物理。我们现在了解到，像气泡产量这样的非常小的事件可以对海洋中的较大过程（如吸收气体吸收）产生显着影响，因此了解海洋中存在的气泡数量和大小的知识变得越来越重要。由于波浪破裂后的第一秒钟或两秒钟存在着强烈的湍流，因此形成了断裂波下方的气泡。这种湍流会使气泡变形，并可能将大气泡分解成两个或更多个较小的气泡。这些较小的气泡可能会依次碎片，并且该过程继续进行，直到湍流不再足够强，无法打破气泡。此外，气泡可能会碰到彼此并结合，从而使两个较小的气泡较大。所有这些过程决定了波浪破裂之后有多少个气泡，并且它们有多大，然后这种固定的气泡群会增加，溶解并随着时间而变慢。气泡的失真取决于湍流的强度和气泡表面的行为方式。表面倾向于减少失真，因此防止气泡破裂。先前的研究调查了在干净的淡水和盐水中分裂的气泡分裂，但天然海水含有许多其他物质，这些物质是由水中的小生物产生的（例如藻类，小植物和小动物）。这些物质中的许多物质都会粘在气泡表面，并可能改变气泡表面的行为，包括分裂和重新加入的概率。这个团契项目将考虑将单个气泡分成两个气泡和成对的气泡，以形成一个更大的湍流气泡，并比较出和没有天然海洋化学物质的情况。然后，将产生人造波，并允许有或没有其他化学物质的波浪储罐中断，以便我们可以看到由化学物质引起的气泡的数量和大小的变化。最后，将研究海上真正破裂波中的气泡，以寻找相同的效果。总体结果将有助于我们了解海洋的自然化学如何影响海洋和大气相互作用。海洋化学在海洋的不同地区可能会大不相同，目前在测量天然气泡种群及其影响时尚未考虑这一点。