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，它吸收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，这个重要的海洋碳汇在未来会如何变化还存在不确定性，关键是要更好地了解海洋碳系统，才能准确预测地球气候。海洋碳吸收的一个关键驱动因素是海洋生物：生活在海洋表面的植物通过光合作用将被吸收到海洋中的大气碳转化为它们体内的有机物。这些有机物质最终以“海洋雪”的形式沉入深海，在海底沉积物中被锁住数千年。海洋学家通常使用沉积物捕集器来捕获和测量海洋雪，然而沉积物捕集器只能在一个地方收集数据，通常以月为时间尺度。结果是严重缺乏关于海洋雪的较短时间和空间尺度变异性的信息，使人们难以理解调节海洋碳储存的过程。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电流计数据，这些数据通常与沉积物陷阱一起收集，以更高的时间分辨率（小时）估计碳通量。我们将使用后向散射数据，也由声电流计记录，但通常被视为副产品。为了验证该方法，我们将分析在南大洋收集的样本数据集，该数据集包括沉积物捕集器和声波后向散射数据。除了提供尚未确定的时间尺度的碳通量数据外，该项目的输出还可以应用于大量遗留的声学数据（例如，过去几十年来在世界各地海洋收集的当前数据记录），大大提高了过去和现在碳通量估算的全球覆盖范围。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.