海盆尺度海洋过程对热带海山生态系统内部波浪机制的调控

IF 3.8 3区 地球科学 Q1 OCEANOGRAPHY
E. Robinson, P. Hosegood, A. Bolton
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引用次数: 0

摘要

浅海海隆作为生物庇护所,尤其是在整个寡营养海洋中发挥着重要作用,因此越来越被认为是需要保护的关键栖息地。传统上,泰勒帽被认为是海山生物量聚集的驱动机制,但基于更高分辨率测量的新证据强调了内波(IW)对当地生态系统的重要性。这些波浪能从深处用冷水冲刷海底生境,并通过湍流混合在短时间内影响营养物质的供应,还可能影响鱼类的行为。不过,这些波浪取决于区域分层情况,因此会受到海洋条件行星尺度变化的影响。我们在此详细观测了印度洋中部一座名为桑德斯(Sandes)的浅海海山在印度洋偶极子(IOD)的不同阶段调节区域分层的内波机制。由 2019 年 IOD 事件引起的深温跃层排除了山顶的内波活动,而 2020 年 IOD 极性反转时与山顶共存的温跃层导致了 30 米振幅的内潮信号(t∼ 12.5 小时)。2022 年观测到的浅温跃层导致 IWs 在山顶上空传播,内潮不明显。谐波分析显示,2020 & 2022 年期间,海山两侧出现了高频波(t ∼ 15 分钟),这可能是局部剪切不稳定性的结果,而 2019 年则出现了非对称响应,这可能是由于强大的背景海流和山顶深度下的温跃层受到抑制。山顶上空的波浪对当地生态系统的潜在重要性可归因于内波传播过程中在温跃层测量到的湍流升高,常规观测到的湍流值为 ε > 10-5 W kg-1。我们的结果凸显了温跃层深度作为顶点内波演化的门控条件的能力。这些结果表明,虽然与经常引用的泰勒帽动力学相比,水柱在短时相尺度上表现出可变性,但它也受到更广泛的海盆尺度过程的调节。因此,在评估这些动态的、对环境至关重要的栖息地时,需要采用更加综合的方法,将物理海洋学控制在多个时空尺度上的影响包括在内。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Modulation of the internal wave regime over a tropical seamount ecosystem by basin-scale oceanographic processes

Shallow seamounts are becoming increasingly recognised as key habitats for conservation due to their role as biological refuges, particularly throughout oligotrophic oceans. Traditionally, Taylor caps have been invoked as the mechanism driving biomass aggregation over seamounts but emerging evidence based on higher resolution measurements highlights the importance of internal waves (IW) to the local ecosystem. These waves can flush the benthic habitat with cool water from depth and impact on nutrient supply over short time scales through turbulent mixing that may also influence fish behaviour. They are dependent on the regional stratification, however, and thus influenced by planetary-scale variability in oceanographic conditions. We present here detailed observations of the internal wave regime over a shallow seamount, called Sandes, in the central Indian Ocean throughout different phases of the Indian Ocean Dipole (IOD) that modulated the regional stratification. A deep thermocline, caused by the 2019 IOD event precluded internal wave activity over the summit, whereas a thermocline collocated with the summit during 2020 when the IOD reversed polarity resulted in a 30 m amplitude internal tide signal (t ∼ 12.5 h). A shallow thermocline, observed during 2022, resulted in propagation of IWs over the summit with less visible internal tide. Harmonic analysis shows the presence of high frequency waves (t ∼ 15 min) on both flanks of the seamount during 2020 & 2022, which are likely a result of local shear instability, whereas 2019 shows an asymmetric response, potentially due to the strong background current and suppression of the thermocline beneath the depth of the summit. The potential importance of the waves over the summit to the local ecosystem may be attributed to the elevated turbulence measured at the thermocline during internal wave propagation, with ε > 10-5 W kg-1 routinely observed. Our results highlight the ability of thermocline depth to act as a gating condition for internal wave evolution over the summit. These results show that, whilst the water column exhibits variability at short spatiotemporal scales compared to the frequently cited Taylor cap dynamics, it is also regulated by the wider basin scale processes. Thus, a more integrated approach is needed when assessing these dynamic and environmentally critical habitats to include the effects of physical oceanographic controls across multiple spatiotemporal scales.

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来源期刊
Progress in Oceanography
Progress in Oceanography 地学-海洋学
CiteScore
7.20
自引率
4.90%
发文量
138
审稿时长
3 months
期刊介绍: Progress in Oceanography publishes the longer, more comprehensive papers that most oceanographers feel are necessary, on occasion, to do justice to their work. Contributions are generally either a review of an aspect of oceanography or a treatise on an expanding oceanographic subject. The articles cover the entire spectrum of disciplines within the science of oceanography. Occasionally volumes are devoted to collections of papers and conference proceedings of exceptional interest. Essential reading for all oceanographers.
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