Can you hear marine snow falling?

全球海洋在我们的气候系统中发挥着关键作用，它提取和储存了人类释放到大气中的大部分碳，从而缓冲了全球变暖的影响。然而，这一重要的海洋碳汇未来可能如何变化还存在不确定性，关键是需要更好地了解海洋碳系统，以准确预测地球气候。海洋碳吸收的一个关键驱动力是海洋生物：生活在海洋表面的植物通过光合作用将吸收到海洋中的大气碳转化为体内的有机物质。这些有机物最终以“海洋雪”的形式沉入深海，在那里它可以在海底沉积物中被锁定数千年。海洋学家通常使用沉积物收集器来捕获和测量海洋雪，但是沉积物收集器只能在一个地方收集数据，通常是每月一次。结果是严重缺乏关于海洋雪的较短时间和空间尺度变化的信息，使得难以理解介导海洋碳储存的过程。在这个项目中，我们将开发一种新的方法来重新利用标准的海洋声学海流计数据，通常收集在沉积物陷阱旁边，以更高的时间分辨率（小时）估计碳通量。我们将使用反向散射数据，也记录了声海流计，但通常忽略作为一个双产品。为了测试的方法，我们将分析一个样本数据集收集在南大洋，其中包括沉积物陷阱和声学后向散射数据。除了提供尚未解决的时间尺度的碳通量数据外，该项目的产出还可应用于大量遗留声学数据（例如过去几十年在世界各大洋收集的当前数据记录），从而大大改善过去和现在碳通量估计的全球覆盖范围。最终，我们将提高理解和预测海洋未来碳储存能力以及地球气候的能力。

The global ocean plays a key role in our climate system by extracting and storing much of the carbon released by humans into the atmosphere, thereby buffering the effects of global warming. However, there are uncertainties as to how this important ocean-carbon sink may change in future, and critically a better understanding of the ocean-carbon system is needed to accurately predict the Earth's climate. A key driver of ocean carbon uptake is marine life: plants that live in the surface ocean convert the atmospheric carbon that is absorbed into the ocean into their body organic matter through photosynthesis. This organic matter eventually sinks to the deep ocean in the form of 'marine snow' where it can be locked up for thousands of years in seafloor sediments. Oceanographers typically use sediment-traps to capture and measure marine snow, however sediment traps can only collect data in one place on typically monthly timescales. The result is a severe lack of information about the shorter time and space scale variability of marine snow, making it difficult to understand the processes that mediate ocean carbon storage. In this project we will develop a novel method to repurpose standard oceanographic acoustic current meter data, typically collected alongside sediment traps, to estimate carbon fluxes at much higher temporal resolutions (hours). We will use backscatter data, also recorded by the acoustic current meter but normally disregarded as a bi-product. To test the method, we will analyse an exemplar data set collected in the Southern Ocean which consists of both sediment-trap and acoustic backscatter data. As well as providing carbon flux data at yet unresolved temporal scales, output from this project can be applied to a wealth of legacy acoustic data (e.g. current data records collected across the world oceans over past decades), greatly improving the global coverage of past and present carbon flux estimates. Ultimately, we will improve the ability to understand and predict the future carbon storage capacity of the ocean and hence the Earth's climate.