Evidence of sediment resuspension by nonlinear internal waves on the western Portuguese mid-shelf
Evidence of sediment resuspension by nonlinear internal waves on the western Portuguese mid-shelf
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DOI：
10.1016/j.margeo.2007.04.019
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发表时间：
2007-12
期刊：
影响因子：
2.9
通讯作者：
L. Quaresma;J. Vitorino;Anabela Oliveira;José da Silva
中科院分区：
文献类型：
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作者：
L. Quaresma;J. Vitorino;Anabela Oliveira;José da Silva
本文介绍并讨论了在葡萄牙北方大陆架Nazaré海底峡谷（39°47.4′N/009°11.4′W）附近传播的非线性内波（NIWs）的现场观测结果及其对海底作用的证据。来自该边缘的合成孔径雷达（SAR）图像表明，在峡谷顶部（39°35′N/009°25′W）产生了NIW，随后直接传播到大陆架中部。2004年8月29日至9月1日在该地区进行了一项观测计划，以研究这些短周期内波。在82米等深线处，用沿着峡谷产生的NIW轨迹系泊的热敏电阻链和声学多普勒海流剖面仪进行了温度和海流的高分辨率测量。在实验过程中获得了同步ENVISAT SAR图像。这些观测得到了CTD调查和海底沉积物取样的补充。收集到的数据表明，大幅度的内部孤子的传播迫使强底部电流脉冲。湍流剖面和ADCP回波的变化表明，这些短周期事件引起的中陆架底部沉积物的再动员。底部剪切应力的计算，所观察到的峡谷产生的NIWs引起的，揭示了一个充满活力的内波活动，可以补充，在夏季，冬季涌浪在沉积物再悬浮的作用在中间架。这项工作是对欧洲项目EUROSTRATAFORM的贡献，该项目的目标包括研究特定的峡谷系统动力学和有关的沉积作用对欧洲大陆边的影响。
In-situ observations of nonlinear internal waves (NIWs) propagating over the northern shelf of Portugal, near the Nazaré submarine canyon (39°47.4′N/009°11.4′W), and evidence of their action on the bottom, are presented and discussed. Synthetic Aperture Radar (SAR) images from this margin suggest the generation of NIWs over the canyon head (39°35′N/009°25′W) and the subsequent propagation directly to the mid-shelf. An observational program was conducted in this area in the summer of 2004, between August 29th and September 1st, to study these short-period internal waves. Temperature and current high resolution measurements were made with thermistor chains and acoustic Doppler current profilers (ADCPs), moored along the canyon generated NIW track, at the 82 m isobath. A simultaneous ENVISAT SAR image was obtained during the experiment. These observations were complemented by a CTD survey and bottom sediment sampling. Collected data show the propagation of large amplitude internal solitons forcing strong bottom current pulses. Turbidity profiles and ADCP echo variability suggest the remobilization of the mid-shelf bottom sediments induced by these short-period events. Calculations of bottom shear stress, induced by the observed canyon generated NIWs, reveal an energetic internal wave activity that can complement, during summer, the role of winter swell in sediment resuspension over the mid-shelf. This work is a contribution to the European project EUROSTRATAFORM, whose objectives include the study of the specific canyon systems dynamics and related sedimentary impacts on the European continental margin.