Aleynik Dmitry, Inall Mark E, Dale Andrew, Vink Annemiek
SAMS, Scottish Association for Marine Science, Scottish Marine Institute, Oban, PA37 1QA, UK.
University of Edinburgh, School of Geosciences, Edinburgh, EH9 3FE, UK.
Sci Rep. 2017 Dec 5;7(1):16959. doi: 10.1038/s41598-017-16912-2.
Proposed harvesting of polymetallic nodules in the Central Tropical Pacific will generate plumes of suspended sediment which are anticipated to be ecologically harmful. While the deep sea is low in energy, it also can be highly turbulent, since the vertical density gradient which suppresses turbulence is weak. The ability to predict the impact of deep plumes is limited by scarcity of in-situ observations. Our observations show that the low-energy environment more than four kilometres below the surface ultimately becomes an order of magnitude more energetic for periods of weeks in response to the passage of mesoscale eddies. The source of these eddies is remote in time and space, here identified as the Central American Gap Winds. Abyssal current variability is controlled by comparable contributions from tides, surface winds and passing eddies. During eddy-induced elevated flow periods mining-related plumes, potentially supplemented by natural sediment resuspension, are expected to spread and disperse more widely and rapidly. Predictions are given of the timing, location and scales of impact.
在中热带太平洋提议开采多金属结核将产生悬浮沉积物羽流，预计这会对生态环境造成危害。虽然深海能量较低，但由于抑制湍流的垂直密度梯度较弱，深海也可能具有高度湍流性。由于现场观测数据稀缺，预测深海羽流影响的能力受到限制。我们的观测表明，在中尺度涡旋经过时，海面以下超过4公里的低能量环境在数周时间内最终会变得能量高出一个数量级。这些涡旋的来源在时间和空间上都很遥远，这里确定为中美洲海峡风。深海海流的变化受潮汐、海面风以及过往涡旋的类似作用控制。在涡旋引起的流量增加期间，与采矿相关的羽流，可能因自然沉积物再悬浮而增强，预计会更广泛、更迅速地扩散和消散。文中给出了影响的时间、地点和规模的预测。
