On the generation and propagation of internal solitary waves in the southern Bay of Biscay

• Type: Article in International Scientific Journal
• Date: 2006

Authors

Azevedo, A (Author) Other; da Silva, JCB (Author) Other; New, AL (Author) Other

Journal

Title: Deep-Sea Research Part I: Oceanographic Research Papers

Vol. 53

Pages: 927-941

ISSN: 0967-0637

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 61 Citations

Scopus - 62 Citations

Scientific classification

FOS: Natural sciences > Earth and related Environmental sciences

Other information

Authenticus ID: P-004-KBZ

DOI: 10.1016/j.dsr.2006.01.013

Abstract (EN): Internal solitary waves (ISWs), travelling towards the South-South-West (SSW), are now well documented in the northern and central Bay of Biscay. These are formed from large-amplitude internal tides which result from the interaction of the barotropic tide with the steep shelf-break topography. In the present paper, we investigate available satellite imagery (Synthetic Aperture Radar (SAR) and ASAR data) to reveal that the southern Bay of Biscay is also a "hotspot" region which has a high level of ISW activity. Here, the ISWs travel towards the East-North-East from the Cape Finisterre region off North-West Spain. In fact, we reveal the presence of two wave-trains travelling in slightly different directions (055 degrees T and 040 degrees T). By calculating the strength of the barotropic tidal forcing in the region, and identifying the likely propagation pathways (rays) of internal tidal (IT) energy, we identify the generation sites for these wave-trains as lying on either side of the Ortegal Promontory (OP). This is an undersea "headland" projecting towards the North-West from the north-western coast of Spain (near 44 degrees N, 8.5 degrees W), and over which the barotropic tides are forced to flow. For each generation site, IT rays emanating from "critical" topography (where the ray slope is equal to the topographic slope) in regions of strong barotropic forcing, rise to the surface (for one site after a reflection from the sea-floor) and pass through the thermocline close to the earliest occurrences of the ISWs in the respective wave trains. These rays would then produce, through nonlinear processes, the ISWs through the same "local generation" mechanism that has been used to explain the occurrence of the ISWs in the northern and central Bay. The "local generation" mechanism may therefore be more widely applicable than previously thought. In addition, the methods we have used to deduce the generation sites for these waves are expected to prove equally useful for studies in other areas of the world's oceans.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 15