Multisensor observations of internal waves and their effects in the Bay of Biscay

• Type: Article in International Conference Proceedings Book
• Date: 2000

Authors

Da Silva, JCB (Author) Other; New, AL (Author) Other; Smyth, TJ (Author) Other; Robinson, IS (Author) Other

Conference proceedings International

Title: European Space Agency, (Special Publication) ESA SP

Pages: 1246-1258

ERS-Envisat Symposium 'Looking Down to Earth in the New Millennium'

Gothenburg, 16 October 2000 through 20 October 2000

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ISI Web of Knowledge

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Other information

Authenticus ID: P-007-BRW

Abstract (EN): Observations of internal solitary waves (ISWs or IWs) with ERS SAR and other satellite sensors in the central Bay of Biscay are presented and discussed. The existence of the IWs, and longer wavelength internal tides, as locally large features here, about 140-150 km from the nearest shelf break topography, was predicted and studied with in situ ADCP measurements by New and Pingree (1990a, 1992). Here we will discuss part of a series of ERS SAR observations from 1993 until 2000 which extend southwards from the shelf-break region in the northern Bay of Biscay into the central Bay. An initial study of some of these images has been undertaken by New and da Silva (2000), which provides strongly supportive evidence that the internal waves in the central Bay are generated locally where a beam of internal tidal energy reaches the ocean surface, after generation at the shelf break and reflection from the sea-floor, as conjectured by New and Pingree (1992). In the present paper, the SAR observations are matched and compared with SeaWiFS image data. These show features like phytoplankton blooms that correlate with the well-known surface cooling effect at the Armorican and Celtic shelf edge which results from mixing originated by the IW activity. Mixing originated by the large-amplitude IWs in the central Bay has also been predicted to occur by New and Pingree (2000). In the present paper we characterise the signatures of these IWs in the central Bay of Biscay, and seek evidence of their mixing effects, such as increased phytoplankton abundance, using satellite multisensors (radar and ocean colour). We find that the internal waves in the central Bay, which occur in tidally-generated packets or trains, do indeed correspond to regions or "bands" of increased phytoplankton abundance. These bands (which are apparent on some occasions at least) lag behind, and appear between, the IW trains, which are associated with the troughs of the longer internal tides. That is, the bands of increased chlorophyll occur over the crests of the internal tides. A possible explanation is hypothesised for such a phase shift. The SeaWiFS images also support the occurrence of generally enhanced levels of chlorophyll in the central Bay, close to where the ray of internal tidal energy is expected to surface.

Language: English

Type (Professor's evaluation): Scientific