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Short-term, linear, and non-linear local effects of the tides on the surface dynamics in a new, high-resolution model of the Mediterranean Sea circulation
Ocean Dynamics ( IF 2.2 ) Pub Date : 2020-05-07 , DOI: 10.1007/s10236-020-01364-6
Massimiliano Palma , Roberto Iacono , Gianmaria Sannino , Andrea Bargagli , Adriana Carillo , Balazs M. Fekete , Emanuele Lombardi , Ernesto Napolitano , Giovanna Pisacane , Maria Vittoria Struglia

The tides in the Mediterranean Sea are generally weaker than in other regions of the world ocean, but are locally intensified in passages with complex bathymetry, such as the Gibraltar Strait and the Sicily Channel. To date, a detailed understanding of their effects on the circulation, on the short time scales relevant to forecasting, is still missing, due to the lack of specific observations, and of basin-scale, numerical models explicitly accounting for the tidal forcing. The present investigation attempts to bridge this gap, using a newly developed forecasting model of the circulation of the Mediterranean Sea-Black Sea system that includes the effects of the main diurnal and semidiurnal astronomical tides. After validating the model barotropic tidal dynamics through comparison with the results of a tidal inversion software and historical data, a fully baroclinic run is analyzed, with focus on the Mediterranean Sea dynamics. The run covers the period 19 March–30 April 2018 and is initialized and forced with realistic fields produced by state-of-the-art operational models. After verifying that the modelled circulation and hydrology agree with available remote and in situ observations, attention is focused on short-time effects of the tidal forcing on the local circulation. Tides are found to significantly modulate transports not only across the Strait of Gibraltar and the Sicily Channel, as expected, but also across the Corsica Channel and the Otranto Strait. Tidal effects also modify relevant features of the circulation inside the basin, inducing local modulations of some of the main currents and exciting topographic waves that eventually get trapped over shallow bathymetric features, producing diurnal rotations of the flow patterns. Examples of the latter dynamics are found over the Adventure Bank and the Malta Plateau, in the Sicily Channel, and in the eastern portions of the Corsica Channel and the Otranto Strait. Furthermore, in several locations (Sicily Channel, Corsica Channel, Messina Strait, North Adriatic Sea), spectral analysis of the mean kinetic energy reveals the presence of spectral peaks corresponding to periods of about 8 and 6 h, which can only be interpreted as harmonics (overtides and compound tides) of the diurnal and semidiurnal tidal components, generated through non-linear interactions. This shows that, contrary to a widespread assumption, tidal effects in the Mediterranean cannot be linearly superimposed on the basin circulation.

中文翻译:

在新的高分辨率地中海环流模型中,潮汐对表面动力学的短期,线性和非线性局部影响

地中海的潮汐通常比世界其他地区的潮汐弱,但在诸如直布罗陀海峡和西西里海峡等复杂的测深仪航道中,当地的潮汐加剧。迄今为止,由于缺乏具体的观测资料,而且缺乏明确解释潮汐强迫的数值模型,因此仍缺乏对与预报有关的短期尺度上的环流影响的详细了解。本研究试图使用一种新开发的地中海黑海系统环流预报模型弥合这一差距,该模型包括主要的昼间和半昼间天文潮汐的影响。通过与潮汐反演软件和历史数据的比较来验证模型正压潮汐动力学之后,分析了一次完整的斜压运行,重点是地中海动力学。这次运行涵盖了2018年3月19日至4月30日期间,并通过最先进的运营模型生成的实际字段进行了初始化和强制。在验证了模拟的环流和水文学与现有的远程和原位观测结果一致之后,注意力集中在了潮汐强迫对局部环流的短期影响上。人们发现,潮汐不仅可以极大地调节直布罗陀海峡和西西里海峡的运输,而且可以调节科西嘉海峡和奥特朗托海峡的运输。潮汐效应还改变了盆地内部环流的相关特征,引起了一些主要水流的局部调制和令人兴奋的地形波,最终这些波被困在浅水深特征上,产生流动模式的昼夜旋转。后一种动力的例子可见于冒险银行和马耳他高原,西西里海峡,科西嘉海峡和奥特朗托海峡的东部。此外,在几个位置(西西里海峡,科西嘉海峡,墨西拿海峡,北亚得里亚海),对平均动能的光谱分析表明存在对应于大约8和6小时周期的光谱峰,这些峰只能解释为谐波通过非线性相互作用产生的日和半日潮汐分量(潮汐和复合潮汐)。这表明,与广泛的假设相反,地中海的潮汐效应不能线性地叠加在盆地环流上。后一种动力的例子可见于冒险银行和马耳他高原,西西里海峡,科西嘉海峡和奥特朗托海峡的东部。此外,在几个位置(西西里海峡,科西嘉海峡,墨西拿海峡,北亚得里亚海),对平均动能的频谱分析表明存在对应于约8和6 h的频谱峰值,这只能解释为谐波通过非线性相互作用产生的日和半日潮汐分量(潮汐和复合潮汐)。这表明,与广泛的假设相反,地中海的潮汐效应不能线性地叠加在盆地环流上。后一种动力的例子可见于冒险银行和马耳他高原,西西里海峡,科西嘉海峡和奥特朗托海峡的东部。此外,在几个位置(西西里海峡,科西嘉海峡,墨西拿海峡,北亚得里亚海),对平均动能的频谱分析表明存在对应于约8和6 h的频谱峰值,这只能解释为谐波通过非线性相互作用产生的日和半日潮汐分量(潮汐和复合潮汐)。这表明,与广泛的假设相反,地中海的潮汐效应不能线性地叠加在盆地环流上。在科西嘉海峡和奥特朗托海峡的东部。此外,在几个位置(西西里海峡,科西嘉海峡,墨西拿海峡,北亚得里亚海),对平均动能的频谱分析表明存在对应于约8和6 h的频谱峰值,这只能解释为谐波通过非线性相互作用产生的日和半日潮汐分量(潮汐和复合潮汐)。这表明,与广泛的假设相反,地中海的潮汐效应不能线性地叠加在盆地环流上。在科西嘉海峡和奥特朗托海峡的东部。此外,在几个位置(西西里海峡,科西嘉海峡,墨西拿海峡,北亚得里亚海),对平均动能的频谱分析表明存在对应于约8和6 h的频谱峰值,这只能解释为谐波通过非线性相互作用产生的日和半日潮汐分量(潮汐和复合潮汐)。这表明,与广泛的假设相反,地中海的潮汐效应不能线性地叠加在盆地环流上。平均动能的频谱分析显示对应于约8和6 h周期的频谱峰值的存在,这只能解释为通过非线性相互作用产生的昼夜和半昼间潮汐分量的谐波(叠加潮汐和复合潮汐) 。这表明,与广泛的假设相反,地中海的潮汐效应不能线性地叠加在盆地环流上。平均动能的频谱分析显示对应于约8和6 h周期的频谱峰值的存在,这只能解释为通过非线性相互作用产生的昼夜和半昼间潮汐分量的谐波(叠加潮汐和复合潮汐) 。这表明,与广泛的假设相反,地中海的潮汐效应不能线性地叠加在盆地环流上。
更新日期:2020-05-07
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