英国南安普顿国家海洋学中心Bailey, Lewis P.团队在研究潮汐和季节时间尺度上高度可变的深海洋流中取得新进展。相关论文发表在2024年7月25日出版的《自然—地球科学》杂志上。

据介绍，沉积物和相关物质(如有机碳、营养物质和污染物)的深海运输受近底流控制。在大陆斜坡上，这些底流包括周期性的下坡重力驱动的浊流，和较为稳定的沿坡温盐驱动的顺坡等深线海流。深海监测的最新进展催化了人们对浊流和等深流理解的一步变化。然而，这些过程很少单独运行，近底流仍然需要在混合系统中进行量化。这些测量对于理解深海颗粒输送、校准数值模型和重建古流动至关重要。

研究人员对莫桑比克近海混合系统中，34个仪器系泊点4年的观察数据进行分析，近底流是高度动态变化的。研究观察到在潮汐和季节时间尺度上的速度空间可变性，包括洋流方向的逆转，以及局部海底形态的强列转向和漏斗效应。研究观测到的近底流能够在海底移动和分布沉积物，因此使深海颗粒迁移和古海洋条件的重建复杂化。

附：英文原文

Title: Highly variable deep-sea currents over tidal and seasonal timescales

Author: Bailey, Lewis P., Clare, Michael A., Hunt, James E., Kane, Ian A., Miramontes, Elda, Fonnesu, Marco, Argiolas, Ricardo, Malgesini, Giuseppe, Wallerand, Regis

Issue&Volume: 2024-07-25

Abstract: Deep-sea transport of sediment and associated matter, such as organic carbon, nutrients and pollutants, is controlled by near-bed currents. On the continental slope, these currents include episodic down-slope gravity-driven turbidity currents and more sustained thermohaline-driven along-slope contour currents. Recent advancements in deep-sea monitoring have catalysed a step change in our understanding of turbidity currents and contour currents individually. However, these processes rarely operate in isolation and the near-bed current regime is still to be quantified in a mixed system. Such measurements are crucial for understanding deep-sea particulate transport, calibrating numerical models and reconstructing palaeoflow. Here we use 4years of observations from 34 instrument moorings in a mixed system offshore of Mozambique to show that near-bed currents are highly dynamic. We observe spatial variability in velocity over tidal and seasonal timescales, including reversals in current direction, and a strong steering and funnelling influence by local seabed morphology. The observed near-bed currents are capable of mobilizing and distributing sediments across the seabed, therefore complicating deep-sea particulate transport and reconstruction of palaeoceanographic conditions.

DOI: 10.1038/s41561-024-01494-2

Source: https://www.nature.com/articles/s41561-024-01494-2