Process study of vertical mixing near the sea floor inside the central valley of the Mid-Atlantic Ridge near 37°N

与湍流动能耗散有关的垂直混合维持着深海和深海的环流。新的证据表明，在大洋中脊系统的中央山谷和脊侧翼（转换）峡谷内发现了最高的混合率。拟于2010年8月进行一次考察，在此期间，将使用自动潜航器，辅以“传统”的下放和系泊技术，在北纬37度附近的大西洋中脊中央谷进行近海底海洋学和海洋地质测量。目前尚不清楚是什么物理机制控制了深海峡谷中强烈的湍流耗散。最近的研究指出了在浅水研究中观察到的水跃的潜在作用。我们的目的是测试是否潮汐变化的水跃可以解释所观察到的大的垂直混合在中央谷的窗台。为了解决跳跃AUV的基础上，高分辨率的近底湍流动能耗散和流速的水平场将获得。此外，高分辨率AUV多波束回声测深仪测绘将使我们能够研究（一）垂直混合过程和测深之间的关系，以及（二）的动态过程的基础上的“混合活动”的形态。

Vertical mixing associated with dissipation of turbulent kinetic energy sustains the circulation of the deep and abyssal ocean. New evidence is emerging that the highest mixing rates are found within the central valleys and ridge flank (transform) canyons of mid-oceanic ridge systems. An expedition is proposed to take place in August 2010 during which near-bottom oceanographic and marine-geologic measurements will be carried out in the central valley of the Mid-Atlantic Ridge near 37°N, using an autonomous underwater vehicle (AUV), complemented by “classical” lowered and mooring-based techniques. It is currently unclear, which physical mechanisms control the intense turbulent dissipation in deep ocean canyons. Recent studies point to a potential role of hydraulic jumps, which have been observed in shallow water studies. We aim at testing whether tidally varying hydraulic jumps can explain the observed large vertical mixing over a sill in the central valley. To resolve the jumps AUV-based high-resolution horizontal fields of near-bottom turbulent kinetic energy dissipation and of flow velocities will be obtained. Further, high-resolution AUV multi-beam echosounder mapping will allow us to study (i) the relationship between vertical mixing processes and the bathymetry, and (ii) the dynamic processes underlying the “mixing active” morphology.