van Haren Hans, Hanz Ulrike, de Stigter Henko, Mienis Furu, Duineveld Gerard
Royal Netherlands Institute for Sea Research (NIOZ) and Utrecht University, Den Burg, the Netherlands.
PLoS One. 2017 Dec 21;12(12):e0189720. doi: 10.1371/journal.pone.0189720. eCollection 2017.
The turbulence regime near the crest of a biologically rich seamount of the Mid-Atlantic Ridge southwest of the Azores was registered in high spatial and temporal resolution. Internal tides and their higher harmonics dominate the internal wave motions, producing considerable shear-induced turbulent mixing in layers of 10-50 m thickness. This interior mixing of about 100 times open-ocean interior values is observed both at a high-resolution temperature sensor mooring-site at the crest, 770 m water depth being nearly 400 m below the top of the seamount, and a CTD-yoyo site at the slope off the crest 400 m horizontally away, 880 m water depth. Only at the mooring site, additionally two times higher turbulence is observed near the bottom, associated with highly non-linear wave breaking. The highest abundance of epifauna, notably sponges, are observed just below the crest and 100 m down the eastern slope (700-800 m) in a cross-ridge video-camera transect. This sponge belt is located in a water layer of depressed oxygen levels (saturation 63±2%) with a local minimum centered around 700 m. Turbulent mixing supplies oxygen to this region from above and below and is expected to mix nutrients away from this biodegraded layer towards the depth of highest abundance of macrofauna.
在亚速尔群岛西南的大西洋中脊一座生物丰富的海山顶部附近，以高空间和时间分辨率记录了湍流状态。内潮及其高次谐波主导着内波运动，在厚度为10 - 50米的水层中产生了相当大的剪切诱导湍流混合。在海山顶部水深770米（比海山顶部低近400米）处的高分辨率温度传感器系泊站点以及在顶部水平距离400米、水深880米的海山斜坡处的一个CTD - yoyo站点，都观测到了这种比开阔海洋内部混合值高约100倍的内部混合。仅在系泊站点，在底部附近还观测到了另外两倍高的湍流，这与高度非线性的波浪破碎有关。在跨海山的摄像机断面中，在海山顶部下方和东坡向下100米处（700 - 800米）观测到了最丰富的表栖动物，尤其是海绵。这条海绵带位于氧气水平降低的水层（饱和度63±2%）中，局部最小值集中在700米左右。湍流混合从上方和下方为该区域提供氧气，预计会将营养物质从这个生物降解层混合到大型底栖动物最丰富的深度。
